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package jsr166y; |
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import java.util.concurrent.*; |
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import java.util.ArrayList; |
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import java.util.Arrays; |
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import java.util.Collection; |
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import java.util.Collections; |
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import java.util.List; |
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import java.util.Random; |
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import java.util.concurrent.AbstractExecutorService; |
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import java.util.concurrent.Callable; |
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import java.util.concurrent.ExecutorService; |
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import java.util.concurrent.Future; |
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import java.util.concurrent.RejectedExecutionException; |
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import java.util.concurrent.RunnableFuture; |
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import java.util.concurrent.TimeUnit; |
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import java.util.concurrent.TimeoutException; |
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import java.util.concurrent.atomic.AtomicInteger; |
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import java.util.concurrent.locks.LockSupport; |
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import java.util.concurrent.locks.ReentrantLock; |
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import java.util.concurrent.atomic.AtomicInteger; |
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import java.util.concurrent.CountDownLatch; |
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import java.util.concurrent.locks.Condition; |
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/** |
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* An {@link ExecutorService} for running {@link ForkJoinTask}s. |
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* set of worker threads: Submissions from non-FJ threads enter |
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* into a submission queue. Workers take these tasks and typically |
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* split them into subtasks that may be stolen by other workers. |
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* The main work-stealing mechanics implemented in class |
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* ForkJoinWorkerThread give first priority to processing tasks |
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* from their own queues (LIFO or FIFO, depending on mode), then |
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* to randomized FIFO steals of tasks in other worker queues, and |
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* lastly to new submissions. These mechanics do not consider |
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* affinities, loads, cache localities, etc, so rarely provide the |
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* best possible performance on a given machine, but portably |
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* provide good throughput by averaging over these factors. |
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* (Further, even if we did try to use such information, we do not |
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* usually have a basis for exploiting it. For example, some sets |
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* of tasks profit from cache affinities, but others are harmed by |
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* cache pollution effects.) |
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* |
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* Beyond work-stealing support and essential bookkeeping, the |
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* main responsibility of this framework is to take actions when |
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* one worker is waiting to join a task stolen (or always held by) |
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* another. Because we are multiplexing many tasks on to a pool |
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* of workers, we can't just let them block (as in Thread.join). |
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* We also cannot just reassign the joiner's run-time stack with |
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* another and replace it later, which would be a form of |
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* "continuation", that even if possible is not necessarily a good |
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* idea. Given that the creation costs of most threads on most |
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* systems mainly surrounds setting up runtime stacks, thread |
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* creation and switching is usually not much more expensive than |
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* stack creation and switching, and is more flexible). Instead we |
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* Preference rules give first priority to processing tasks from |
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* their own queues (LIFO or FIFO, depending on mode), then to |
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* randomized FIFO steals of tasks in other worker queues, and |
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* lastly to new submissions. |
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* |
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* The main throughput advantages of work-stealing stem from |
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* decentralized control -- workers mostly take tasks from |
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* themselves or each other. We cannot negate this in the |
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* implementation of other management responsibilities. The main |
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* tactic for avoiding bottlenecks is packing nearly all |
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* essentially atomic control state into a single 64bit volatile |
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* variable ("ctl"). This variable is read on the order of 10-100 |
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* times as often as it is modified (always via CAS). (There is |
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* some additional control state, for example variable "shutdown" |
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* for which we can cope with uncoordinated updates.) This |
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* streamlines synchronization and control at the expense of messy |
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* constructions needed to repack status bits upon updates. |
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* Updates tend not to contend with each other except during |
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* bursts while submitted tasks begin or end. In some cases when |
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* they do contend, threads can instead do something else |
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* (usually, scan for tesks) until contention subsides. |
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* |
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* To enable packing, we restrict maximum parallelism to (1<<15)-1 |
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* (which is far in excess of normal operating range) to allow |
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* ids, counts, and their negations (used for thresholding) to fit |
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* into 16bit fields. |
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* |
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* Recording Workers. Workers are recorded in the "workers" array |
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* that is created upon pool construction and expanded if (rarely) |
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* necessary. This is an array as opposed to some other data |
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* structure to support index-based random steals by workers. |
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* Updates to the array recording new workers and unrecording |
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* terminated ones are protected from each other by a seqLock |
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* (scanGuard) but the array is otherwise concurrently readable, |
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* and accessed directly by workers. To simplify index-based |
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* operations, the array size is always a power of two, and all |
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* readers must tolerate null slots. To avoid flailing during |
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* start-up, the array is presized to hold twice #parallelism |
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* workers (which is unlikely to need further resizing during |
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* execution). But to avoid dealing with so many null slots, |
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* variable scanGuard includes a mask for the nearest power of two |
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* that contains all current workers. All worker thread creation |
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* is on-demand, triggered by task submissions, replacement of |
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* terminated workers, and/or compensation for blocked |
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* workers. However, all other support code is set up to work with |
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* other policies. To ensure that we do not hold on to worker |
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* references that would prevent GC, ALL accesses to workers are |
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* via indices into the workers array (which is one source of some |
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* of the messy code constructions here). In essence, the workers |
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* array serves as a weak reference mechanism. Thus for example |
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* the wait queue field of ctl stores worker indices, not worker |
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* references. Access to the workers in associated methods (for |
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* example signalWork) must both index-check and null-check the |
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* IDs. All such accesses ignore bad IDs by returning out early |
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* from what they are doing, since this can only be associated |
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* with termination, in which case it is OK to give up. |
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* |
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* All uses of the workers array, as well as queue arrays, check |
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* that the array is non-null (even if previously non-null). This |
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* allows nulling during termination, which is currently not |
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* necessary, but remains an option for resource-revocation-based |
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* shutdown schemes. |
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* |
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* Wait Queuing. Unlike HPC work-stealing frameworks, we cannot |
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* let workers spin indefinitely scanning for tasks when none are |
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* can be immediately found, and we cannot start/resume workers |
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* unless there appear to be tasks available. On the other hand, |
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* we must quickly prod them into action when new tasks are |
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* submitted or generated. We park/unpark workers after placing |
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* in an event wait queue when they cannot find work. This "queue" |
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* is actually a simple Treiber stack, headed by the "id" field of |
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* ctl, plus a 15bit counter value to both wake up waiters (by |
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* advancing their count) and avoid ABA effects. Successors are |
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* held in worker field "nextWait". Queuing deals with several |
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* intrinsic races, mainly that a task-producing thread can miss |
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* seeing (and signalling) another thread that gave up looking for |
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* work but has not yet entered the wait queue. We solve this by |
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* requiring a full sweep of all workers both before (in scan()) |
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* and after (in awaitWork()) a newly waiting worker is added to |
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* the wait queue. During a rescan, the worker might release some |
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* other queued worker rather than itself, which has the same net |
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* effect. |
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* |
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* Signalling. We create or wake up workers only when there |
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* appears to be at least one task they might be able to find and |
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* execute. When a submission is added or another worker adds a |
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* task to a queue that previously had two or fewer tasks, they |
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* signal waiting workers (or trigger creation of new ones if |
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* fewer than the given parallelism level -- see signalWork). |
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* These primary signals are buttressed by signals during rescans |
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* as well as those performed when a worker steals a task and |
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* notices that there are more tasks too; together these cover the |
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* signals needed in cases when more than two tasks are pushed |
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* but untaken. |
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* |
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* Trimming workers. To release resources after periods of lack of |
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* use, a worker starting to wait when the pool is quiescent will |
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* time out and terminate if the pool has remained quiescent for |
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* SHRINK_RATE nanosecs. |
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* |
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* Submissions. External submissions are maintained in an |
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* array-based queue that is structured identically to |
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* ForkJoinWorkerThread queues (which see) except for the use of |
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* submissionLock in method addSubmission. Unlike worker queues, |
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* multiple external threads can add new submissions. |
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* |
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* Compensation. Beyond work-stealing support and lifecycle |
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* control, the main responsibility of this framework is to take |
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* actions when one worker is waiting to join a task stolen (or |
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* always held by) another. Because we are multiplexing many |
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* tasks on to a pool of workers, we can't just let them block (as |
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* in Thread.join). We also cannot just reassign the joiner's |
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* run-time stack with another and replace it later, which would |
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* be a form of "continuation", that even if possible is not |
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* necessarily a good idea since we sometimes need both an |
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* unblocked task and its continuation to progress. Instead we |
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* combine two tactics: |
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* |
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* Helping: Arranging for the joiner to execute some task that it |
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* would be running if the steal had not occurred. Method |
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* ForkJoinWorkerThread.helpJoinTask tracks joining->stealing |
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* ForkJoinWorkerThread.joinTask tracks joining->stealing |
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* links to try to find such a task. |
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* |
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* Compensating: Unless there are already enough live threads, |
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* method helpMaintainParallelism() may create or or |
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* re-activate a spare thread to compensate for blocked |
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* joiners until they unblock. |
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* |
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* It is impossible to keep exactly the target (parallelism) |
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* number of threads running at any given time. Determining |
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* existence of conservatively safe helping targets, the |
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* availability of already-created spares, and the apparent need |
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* to create new spares are all racy and require heuristic |
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* guidance, so we rely on multiple retries of each. Compensation |
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* occurs in slow-motion. It is triggered only upon timeouts of |
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* Object.wait used for joins. This reduces poor decisions that |
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* would otherwise be made when threads are waiting for others |
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* that are stalled because of unrelated activities such as |
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* garbage collection. |
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* method tryPreBlock() may create or re-activate a spare |
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* thread to compensate for blocked joiners until they |
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* unblock. |
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* |
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* The ManagedBlocker extension API can't use helping so relies |
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* only on compensation in method awaitBlocker. |
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* |
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* The main throughput advantages of work-stealing stem from |
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* decentralized control -- workers mostly steal tasks from each |
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* other. We do not want to negate this by creating bottlenecks |
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* implementing other management responsibilities. So we use a |
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* collection of techniques that avoid, reduce, or cope well with |
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* contention. These entail several instances of bit-packing into |
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* CASable fields to maintain only the minimally required |
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* atomicity. To enable such packing, we restrict maximum |
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* parallelism to (1<<15)-1 (enabling twice this (to accommodate |
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* unbalanced increments and decrements) to fit into a 16 bit |
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* field, which is far in excess of normal operating range. Even |
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* though updates to some of these bookkeeping fields do sometimes |
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* contend with each other, they don't normally cache-contend with |
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* updates to others enough to warrant memory padding or |
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* isolation. So they are all held as fields of ForkJoinPool |
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* objects. The main capabilities are as follows: |
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* |
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* 1. Creating and removing workers. Workers are recorded in the |
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* "workers" array. This is an array as opposed to some other data |
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* structure to support index-based random steals by workers. |
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* Updates to the array recording new workers and unrecording |
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* terminated ones are protected from each other by a lock |
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* (workerLock) but the array is otherwise concurrently readable, |
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* and accessed directly by workers. To simplify index-based |
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* operations, the array size is always a power of two, and all |
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* readers must tolerate null slots. Currently, all worker thread |
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* creation is on-demand, triggered by task submissions, |
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* replacement of terminated workers, and/or compensation for |
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* blocked workers. However, all other support code is set up to |
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* work with other policies. |
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* |
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* To ensure that we do not hold on to worker references that |
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* would prevent GC, ALL accesses to workers are via indices into |
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* the workers array (which is one source of some of the unusual |
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* code constructions here). In essence, the workers array serves |
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* as a WeakReference mechanism. Thus for example the event queue |
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* stores worker indices, not worker references. Access to the |
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* workers in associated methods (for example releaseEventWaiters) |
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* must both index-check and null-check the IDs. All such accesses |
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* ignore bad IDs by returning out early from what they are doing, |
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* since this can only be associated with shutdown, in which case |
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* it is OK to give up. On termination, we just clobber these |
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* data structures without trying to use them. |
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* |
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* 2. Bookkeeping for dynamically adding and removing workers. We |
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* aim to approximately maintain the given level of parallelism. |
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* When some workers are known to be blocked (on joins or via |
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* ManagedBlocker), we may create or resume others to take their |
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* place until they unblock (see below). Implementing this |
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* requires counts of the number of "running" threads (i.e., those |
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* that are neither blocked nor artificially suspended) as well as |
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* the total number. These two values are packed into one field, |
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* "workerCounts" because we need accurate snapshots when deciding |
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* to create, resume or suspend. Note however that the |
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* correspondence of these counts to reality is not guaranteed. In |
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* particular updates for unblocked threads may lag until they |
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* actually wake up. |
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* |
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* 3. Maintaining global run state. The run state of the pool |
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* consists of a runLevel (SHUTDOWN, TERMINATING, etc) similar to |
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* those in other Executor implementations, as well as a count of |
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* "active" workers -- those that are, or soon will be, or |
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* recently were executing tasks. The runLevel and active count |
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* are packed together in order to correctly trigger shutdown and |
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* termination. Without care, active counts can be subject to very |
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* high contention. We substantially reduce this contention by |
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* relaxing update rules. A worker must claim active status |
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* prospectively, by activating if it sees that a submitted or |
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* stealable task exists (it may find after activating that the |
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* task no longer exists). It stays active while processing this |
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* task (if it exists) and any other local subtasks it produces, |
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* until it cannot find any other tasks. It then tries |
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* inactivating (see method preStep), but upon update contention |
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* instead scans for more tasks, later retrying inactivation if it |
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* doesn't find any. |
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* |
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* 4. Managing idle workers waiting for tasks. We cannot let |
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* workers spin indefinitely scanning for tasks when none are |
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* available. On the other hand, we must quickly prod them into |
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* action when new tasks are submitted or generated. We |
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* park/unpark these idle workers using an event-count scheme. |
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* Field eventCount is incremented upon events that may enable |
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* workers that previously could not find a task to now find one: |
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* Submission of a new task to the pool, or another worker pushing |
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* a task onto a previously empty queue. (We also use this |
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* mechanism for configuration and termination actions that |
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* require wakeups of idle workers). Each worker maintains its |
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* last known event count, and blocks when a scan for work did not |
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* find a task AND its lastEventCount matches the current |
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* eventCount. Waiting idle workers are recorded in a variant of |
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* Treiber stack headed by field eventWaiters which, when nonzero, |
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* encodes the thread index and count awaited for by the worker |
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* thread most recently calling eventSync. This thread in turn has |
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* a record (field nextEventWaiter) for the next waiting worker. |
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* In addition to allowing simpler decisions about need for |
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* wakeup, the event count bits in eventWaiters serve the role of |
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* tags to avoid ABA errors in Treiber stacks. Upon any wakeup, |
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* released threads also try to release at most two others. The |
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* net effect is a tree-like diffusion of signals, where released |
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* threads (and possibly others) help with unparks. To further |
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* reduce contention effects a bit, failed CASes to increment |
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* field eventCount are tolerated without retries in signalWork. |
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* Conceptually they are merged into the same event, which is OK |
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* when their only purpose is to enable workers to scan for work. |
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* |
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* 5. Managing suspension of extra workers. When a worker notices |
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* (usually upon timeout of a wait()) that there are too few |
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* running threads, we may create a new thread to maintain |
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* parallelism level, or at least avoid starvation. Usually, extra |
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* threads are needed for only very short periods, yet join |
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* dependencies are such that we sometimes need them in |
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* bursts. Rather than create new threads each time this happens, |
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* we suspend no-longer-needed extra ones as "spares". For most |
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* purposes, we don't distinguish "extra" spare threads from |
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* normal "core" threads: On each call to preStep (the only point |
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* at which we can do this) a worker checks to see if there are |
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* now too many running workers, and if so, suspends itself. |
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* Method helpMaintainParallelism looks for suspended threads to |
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* resume before considering creating a new replacement. The |
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* spares themselves are encoded on another variant of a Treiber |
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* Stack, headed at field "spareWaiters". Note that the use of |
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* spares is intrinsically racy. One thread may become a spare at |
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* about the same time as another is needlessly being created. We |
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* counteract this and related slop in part by requiring resumed |
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* spares to immediately recheck (in preStep) to see whether they |
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* they should re-suspend. |
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* |
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* 6. Killing off unneeded workers. A timeout mechanism is used to |
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* shed unused workers: The oldest (first) event queue waiter uses |
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* a timed rather than hard wait. When this wait times out without |
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* a normal wakeup, it tries to shutdown any one (for convenience |
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* the newest) other spare or event waiter via |
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* tryShutdownUnusedWorker. This eventually reduces the number of |
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* worker threads to a minimum of one after a long enough period |
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* without use. |
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* |
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* 7. Deciding when to create new workers. The main dynamic |
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* control in this class is deciding when to create extra threads |
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* in method helpMaintainParallelism. We would like to keep |
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* exactly #parallelism threads running, which is an impossible |
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* task. We always need to create one when the number of running |
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* threads would become zero and all workers are busy. Beyond |
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* this, we must rely on heuristics that work well in the the |
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* presence of transients phenomena such as GC stalls, dynamic |
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* compilation, and wake-up lags. These transients are extremely |
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* common -- we are normally trying to fully saturate the CPUs on |
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* a machine, so almost any activity other than running tasks |
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* impedes accuracy. Our main defense is to allow parallelism to |
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* lapse for a while during joins, and use a timeout to see if, |
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* after the resulting settling, there is still a need for |
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* additional workers. This also better copes with the fact that |
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* some of the methods in this class tend to never become compiled |
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* (but are interpreted), so some components of the entire set of |
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* controls might execute 100 times faster than others. And |
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* similarly for cases where the apparent lack of work is just due |
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* to GC stalls and other transient system activity. |
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> |
* It is impossible to keep exactly the target parallelism number |
266 |
> |
* of threads running at any given time. Determining the |
267 |
> |
* existence of conservatively safe helping targets, the |
268 |
> |
* availability of already-created spares, and the apparent need |
269 |
> |
* to create new spares are all racy and require heuristic |
270 |
> |
* guidance, so we rely on multiple retries of each. Currently, |
271 |
> |
* in keeping with on-demand signalling policy, we compensate only |
272 |
> |
* if blocking would leave less than one active (non-waiting, |
273 |
> |
* non-blocked) worker. Additionally, to avoid some false alarms |
274 |
> |
* due to GC, lagging counters, system activity, etc, compensated |
275 |
> |
* blocking for joins is only attempted after a number of rechecks |
276 |
> |
* proportional to the current apparent deficit (where retries are |
277 |
> |
* interspersed with Thread.yield, for good citizenship). The |
278 |
> |
* variable blockedCount, incremented before blocking and |
279 |
> |
* decremented after, is sometimes needed to distinguish cases of |
280 |
> |
* waiting for work vs blocking on joins or other managed sync, |
281 |
> |
* but both the cases are equivalent for most pool control, so we |
282 |
> |
* can update non-atomically. (Additionally, contention on |
283 |
> |
* blockedCount alleviates some contention on ctl). |
284 |
> |
* |
285 |
> |
* Shutdown and Termination. A call to shutdownNow atomically sets |
286 |
> |
* the ctl stop bit and then (non-atomically) sets each workers |
287 |
> |
* "terminate" status, cancels all unprocessed tasks, and wakes up |
288 |
> |
* all waiting workers. Detecting whether termination should |
289 |
> |
* commence after a non-abrupt shutdown() call requires more work |
290 |
> |
* and bookkeeping. We need consensus about quiesence (i.e., that |
291 |
> |
* there is no more work) which is reflected in active counts so |
292 |
> |
* long as there are no current blockers, as well as possible |
293 |
> |
* re-evaluations during independent changes in blocking or |
294 |
> |
* quiescing workers. |
295 |
|
* |
296 |
< |
* Beware that there is a lot of representation-level coupling |
296 |
> |
* Style notes: There is a lot of representation-level coupling |
297 |
|
* among classes ForkJoinPool, ForkJoinWorkerThread, and |
298 |
< |
* ForkJoinTask. For example, direct access to "workers" array by |
298 |
> |
* ForkJoinTask. Most fields of ForkJoinWorkerThread maintain |
299 |
> |
* data structures managed by ForkJoinPool, so are directly |
300 |
> |
* accessed. Conversely we allow access to "workers" array by |
301 |
|
* workers, and direct access to ForkJoinTask.status by both |
302 |
|
* ForkJoinPool and ForkJoinWorkerThread. There is little point |
303 |
|
* trying to reduce this, since any associated future changes in |
304 |
|
* representations will need to be accompanied by algorithmic |
305 |
< |
* changes anyway. |
306 |
< |
* |
307 |
< |
* Style notes: There are lots of inline assignments (of form |
308 |
< |
* "while ((local = field) != 0)") which are usually the simplest |
309 |
< |
* way to ensure the required read orderings (which are sometimes |
310 |
< |
* critical). Also several occurrences of the unusual "do {} |
311 |
< |
* while(!cas...)" which is the simplest way to force an update of |
312 |
< |
* a CAS'ed variable. There are also other coding oddities that |
313 |
< |
* help some methods perform reasonably even when interpreted (not |
314 |
< |
* compiled), at the expense of some messy constructions that |
315 |
< |
* reduce byte code counts. |
316 |
< |
* |
317 |
< |
* The order of declarations in this file is: (1) statics (2) |
318 |
< |
* fields (along with constants used when unpacking some of them) |
319 |
< |
* (3) internal control methods (4) callbacks and other support |
320 |
< |
* for ForkJoinTask and ForkJoinWorkerThread classes, (5) exported |
321 |
< |
* methods (plus a few little helpers). |
305 |
> |
* changes anyway. All together, these low-level implementation |
306 |
> |
* choices produce as much as a factor of 4 performance |
307 |
> |
* improvement compared to naive implementations, and enable the |
308 |
> |
* processing of billions of tasks per second, at the expense of |
309 |
> |
* some ugliness. |
310 |
> |
* |
311 |
> |
* Methods signalWork() and scan() are the main bottlenecks so are |
312 |
> |
* especially heavily micro-optimized/mangled. There are lots of |
313 |
> |
* inline assignments (of form "while ((local = field) != 0)") |
314 |
> |
* which are usually the simplest way to ensure the required read |
315 |
> |
* orderings (which are sometimes critical). This leads to a |
316 |
> |
* "C"-like style of listing declarations of these locals at the |
317 |
> |
* heads of methods or blocks. There are several occurrences of |
318 |
> |
* the unusual "do {} while (!cas...)" which is the simplest way |
319 |
> |
* to force an update of a CAS'ed variable. There are also other |
320 |
> |
* coding oddities that help some methods perform reasonably even |
321 |
> |
* when interpreted (not compiled). |
322 |
> |
* |
323 |
> |
* The order of declarations in this file is: (1) declarations of |
324 |
> |
* statics (2) fields (along with constants used when unpacking |
325 |
> |
* some of them), listed in an order that tends to reduce |
326 |
> |
* contention among them a bit under most JVMs. (3) internal |
327 |
> |
* control methods (4) callbacks and other support for |
328 |
> |
* ForkJoinTask and ForkJoinWorkerThread classes, (5) exported |
329 |
> |
* methods (plus a few little helpers). (6) static block |
330 |
> |
* initializing all statics in a minimally dependent order. |
331 |
|
*/ |
332 |
|
|
333 |
|
/** |
362 |
|
* overridden in ForkJoinPool constructors. |
363 |
|
*/ |
364 |
|
public static final ForkJoinWorkerThreadFactory |
365 |
< |
defaultForkJoinWorkerThreadFactory = |
395 |
< |
new DefaultForkJoinWorkerThreadFactory(); |
365 |
> |
defaultForkJoinWorkerThreadFactory; |
366 |
|
|
367 |
|
/** |
368 |
|
* Permission required for callers of methods that may start or |
369 |
|
* kill threads. |
370 |
|
*/ |
371 |
< |
private static final RuntimePermission modifyThreadPermission = |
402 |
< |
new RuntimePermission("modifyThread"); |
371 |
> |
private static final RuntimePermission modifyThreadPermission; |
372 |
|
|
373 |
|
/** |
374 |
|
* If there is a security manager, makes sure caller has |
383 |
|
/** |
384 |
|
* Generator for assigning sequence numbers as pool names. |
385 |
|
*/ |
386 |
< |
private static final AtomicInteger poolNumberGenerator = |
418 |
< |
new AtomicInteger(); |
386 |
> |
private static final AtomicInteger poolNumberGenerator; |
387 |
|
|
388 |
|
/** |
389 |
< |
* The time to block in a join (see awaitJoin) before checking if |
390 |
< |
* a new worker should be (re)started to maintain parallelism |
391 |
< |
* level. The value should be short enough to maintain global |
392 |
< |
* responsiveness and progress but long enough to avoid |
393 |
< |
* counterproductive firings during GC stalls or unrelated system |
426 |
< |
* activity, and to not bog down systems with continual re-firings |
427 |
< |
* on GCs or legitimately long waits. |
389 |
> |
* Generator for initial random seeds for worker victim |
390 |
> |
* selection. This is used only to create initial seeds. Random |
391 |
> |
* steals use a cheaper xorshift generator per steal attempt. We |
392 |
> |
* don't expect much contention on seedGenerator, so just use a |
393 |
> |
* plain Random. |
394 |
|
*/ |
395 |
< |
private static final long JOIN_TIMEOUT_MILLIS = 250L; // 4 per second |
395 |
> |
static final Random workerSeedGenerator; |
396 |
|
|
397 |
|
/** |
398 |
< |
* The wakeup interval (in nanoseconds) for the oldest worker |
399 |
< |
* worker waiting for an event invokes tryShutdownUnusedWorker to shrink |
400 |
< |
* the number of workers. The exact value does not matter too |
401 |
< |
* much, but should be long enough to slowly release resources |
402 |
< |
* during long periods without use without disrupting normal use. |
398 |
> |
* Array holding all worker threads in the pool. Initialized upon |
399 |
> |
* construction. Array size must be a power of two. Updates and |
400 |
> |
* replacements are protected by scanGuard, but the array is |
401 |
> |
* always kept in a consistent enough state to be randomly |
402 |
> |
* accessed without locking by workers performing work-stealing, |
403 |
> |
* as well as other traversal-based methods in this class, so long |
404 |
> |
* as reads memory-acquire by first reading ctl. All readers must |
405 |
> |
* tolerate that some array slots may be null. |
406 |
|
*/ |
407 |
< |
private static final long SHRINK_RATE_NANOS = |
439 |
< |
30L * 1000L * 1000L * 1000L; // 2 per minute |
407 |
> |
ForkJoinWorkerThread[] workers; |
408 |
|
|
409 |
|
/** |
410 |
< |
* Absolute bound for parallelism level. Twice this number plus |
411 |
< |
* one (i.e., 0xfff) must fit into a 16bit field to enable |
412 |
< |
* word-packing for some counts and indices. |
410 |
> |
* Initial size for submission queue array. Must be a power of |
411 |
> |
* two. In many applications, these always stay small so we use a |
412 |
> |
* small initial cap. |
413 |
|
*/ |
414 |
< |
private static final int MAX_WORKERS = 0x7fff; |
414 |
> |
private static final int INITIAL_QUEUE_CAPACITY = 8; |
415 |
|
|
416 |
|
/** |
417 |
< |
* Array holding all worker threads in the pool. Array size must |
418 |
< |
* be a power of two. Updates and replacements are protected by |
419 |
< |
* workerLock, but the array is always kept in a consistent enough |
420 |
< |
* state to be randomly accessed without locking by workers |
453 |
< |
* performing work-stealing, as well as other traversal-based |
454 |
< |
* methods in this class. All readers must tolerate that some |
455 |
< |
* array slots may be null. |
417 |
> |
* Maximum size for submission queue array. Must be a power of two |
418 |
> |
* less than or equal to 1 << (31 - width of array entry) to |
419 |
> |
* ensure lack of index wraparound, but is capped at a lower |
420 |
> |
* value to help users trap runaway computations. |
421 |
|
*/ |
422 |
< |
volatile ForkJoinWorkerThread[] workers; |
422 |
> |
private static final int MAXIMUM_QUEUE_CAPACITY = 1 << 24; // 16M |
423 |
|
|
424 |
|
/** |
425 |
< |
* Queue for external submissions. |
425 |
> |
* Array serving as submission queue. Initialized upon construction. |
426 |
|
*/ |
427 |
< |
private final LinkedTransferQueue<ForkJoinTask<?>> submissionQueue; |
427 |
> |
private ForkJoinTask<?>[] submissionQueue; |
428 |
|
|
429 |
|
/** |
430 |
< |
* Lock protecting updates to workers array. |
430 |
> |
* Lock protecting submissions array for addSubmission |
431 |
|
*/ |
432 |
< |
private final ReentrantLock workerLock; |
432 |
> |
private final ReentrantLock submissionLock; |
433 |
|
|
434 |
|
/** |
435 |
< |
* Latch released upon termination. |
435 |
> |
* Condition for awaitTermination, using submissionLock for |
436 |
> |
* convenience. |
437 |
|
*/ |
438 |
< |
private final Phaser termination; |
438 |
> |
private final Condition termination; |
439 |
|
|
440 |
|
/** |
441 |
|
* Creation factory for worker threads. |
443 |
|
private final ForkJoinWorkerThreadFactory factory; |
444 |
|
|
445 |
|
/** |
446 |
< |
* Sum of per-thread steal counts, updated only when threads are |
447 |
< |
* idle or terminating. |
446 |
> |
* The uncaught exception handler used when any worker abruptly |
447 |
> |
* terminates. |
448 |
|
*/ |
449 |
< |
private volatile long stealCount; |
449 |
> |
final Thread.UncaughtExceptionHandler ueh; |
450 |
|
|
451 |
|
/** |
452 |
< |
* Encoded record of top of Treiber stack of threads waiting for |
487 |
< |
* events. The top 32 bits contain the count being waited for. The |
488 |
< |
* bottom 16 bits contains one plus the pool index of waiting |
489 |
< |
* worker thread. (Bits 16-31 are unused.) |
452 |
> |
* Prefix for assigning names to worker threads |
453 |
|
*/ |
454 |
< |
private volatile long eventWaiters; |
492 |
< |
|
493 |
< |
private static final int EVENT_COUNT_SHIFT = 32; |
494 |
< |
private static final long WAITER_ID_MASK = (1L << 16) - 1L; |
454 |
> |
private final String workerNamePrefix; |
455 |
|
|
456 |
|
/** |
457 |
< |
* A counter for events that may wake up worker threads: |
458 |
< |
* - Submission of a new task to the pool |
499 |
< |
* - A worker pushing a task on an empty queue |
500 |
< |
* - termination |
457 |
> |
* Sum of per-thread steal counts, updated only when threads are |
458 |
> |
* idle or terminating. |
459 |
|
*/ |
460 |
< |
private volatile int eventCount; |
460 |
> |
private volatile long stealCount; |
461 |
|
|
462 |
|
/** |
463 |
< |
* Encoded record of top of Treiber stack of spare threads waiting |
464 |
< |
* for resumption. The top 16 bits contain an arbitrary count to |
465 |
< |
* avoid ABA effects. The bottom 16bits contains one plus the pool |
466 |
< |
* index of waiting worker thread. |
467 |
< |
*/ |
468 |
< |
private volatile int spareWaiters; |
469 |
< |
|
470 |
< |
private static final int SPARE_COUNT_SHIFT = 16; |
471 |
< |
private static final int SPARE_ID_MASK = (1 << 16) - 1; |
463 |
> |
* Main pool control -- a long packed with: |
464 |
> |
* AC: Number of active running workers minus target parallelism (16 bits) |
465 |
> |
* TC: Number of total workers minus target parallelism (16bits) |
466 |
> |
* ST: true if pool is terminating (1 bit) |
467 |
> |
* EC: the wait count of top waiting thread (15 bits) |
468 |
> |
* ID: ~poolIndex of top of Treiber stack of waiting threads (16 bits) |
469 |
> |
* |
470 |
> |
* When convenient, we can extract the upper 32 bits of counts and |
471 |
> |
* the lower 32 bits of queue state, u = (int)(ctl >>> 32) and e = |
472 |
> |
* (int)ctl. The ec field is never accessed alone, but always |
473 |
> |
* together with id and st. The offsets of counts by the target |
474 |
> |
* parallelism and the positionings of fields makes it possible to |
475 |
> |
* perform the most common checks via sign tests of fields: When |
476 |
> |
* ac is negative, there are not enough active workers, when tc is |
477 |
> |
* negative, there are not enough total workers, when id is |
478 |
> |
* negative, there is at least one waiting worker, and when e is |
479 |
> |
* negative, the pool is terminating. To deal with these possibly |
480 |
> |
* negative fields, we use casts in and out of "short" and/or |
481 |
> |
* signed shifts to maintain signedness. |
482 |
> |
*/ |
483 |
> |
volatile long ctl; |
484 |
> |
|
485 |
> |
// bit positions/shifts for fields |
486 |
> |
private static final int AC_SHIFT = 48; |
487 |
> |
private static final int TC_SHIFT = 32; |
488 |
> |
private static final int ST_SHIFT = 31; |
489 |
> |
private static final int EC_SHIFT = 16; |
490 |
> |
|
491 |
> |
// bounds |
492 |
> |
private static final int MAX_ID = 0x7fff; // max poolIndex |
493 |
> |
private static final int SMASK = 0xffff; // mask short bits |
494 |
> |
private static final int SHORT_SIGN = 1 << 15; |
495 |
> |
private static final int INT_SIGN = 1 << 31; |
496 |
> |
|
497 |
> |
// masks |
498 |
> |
private static final long STOP_BIT = 0x0001L << ST_SHIFT; |
499 |
> |
private static final long AC_MASK = ((long)SMASK) << AC_SHIFT; |
500 |
> |
private static final long TC_MASK = ((long)SMASK) << TC_SHIFT; |
501 |
> |
|
502 |
> |
// units for incrementing and decrementing |
503 |
> |
private static final long TC_UNIT = 1L << TC_SHIFT; |
504 |
> |
private static final long AC_UNIT = 1L << AC_SHIFT; |
505 |
> |
|
506 |
> |
// masks and units for dealing with u = (int)(ctl >>> 32) |
507 |
> |
private static final int UAC_SHIFT = AC_SHIFT - 32; |
508 |
> |
private static final int UTC_SHIFT = TC_SHIFT - 32; |
509 |
> |
private static final int UAC_MASK = SMASK << UAC_SHIFT; |
510 |
> |
private static final int UTC_MASK = SMASK << UTC_SHIFT; |
511 |
> |
private static final int UAC_UNIT = 1 << UAC_SHIFT; |
512 |
> |
private static final int UTC_UNIT = 1 << UTC_SHIFT; |
513 |
> |
|
514 |
> |
// masks and units for dealing with e = (int)ctl |
515 |
> |
private static final int E_MASK = 0x7fffffff; // no STOP_BIT |
516 |
> |
private static final int EC_UNIT = 1 << EC_SHIFT; |
517 |
|
|
518 |
|
/** |
519 |
< |
* Lifecycle control. The low word contains the number of workers |
517 |
< |
* that are (probably) executing tasks. This value is atomically |
518 |
< |
* incremented before a worker gets a task to run, and decremented |
519 |
< |
* when worker has no tasks and cannot find any. Bits 16-18 |
520 |
< |
* contain runLevel value. When all are zero, the pool is |
521 |
< |
* running. Level transitions are monotonic (running -> shutdown |
522 |
< |
* -> terminating -> terminated) so each transition adds a bit. |
523 |
< |
* These are bundled together to ensure consistent read for |
524 |
< |
* termination checks (i.e., that runLevel is at least SHUTDOWN |
525 |
< |
* and active threads is zero). |
526 |
< |
* |
527 |
< |
* Notes: Most direct CASes are dependent on these bitfield |
528 |
< |
* positions. Also, this field is non-private to enable direct |
529 |
< |
* performance-sensitive CASes in ForkJoinWorkerThread. |
519 |
> |
* The target parallelism level. |
520 |
|
*/ |
521 |
< |
volatile int runState; |
532 |
< |
|
533 |
< |
// Note: The order among run level values matters. |
534 |
< |
private static final int RUNLEVEL_SHIFT = 16; |
535 |
< |
private static final int SHUTDOWN = 1 << RUNLEVEL_SHIFT; |
536 |
< |
private static final int TERMINATING = 1 << (RUNLEVEL_SHIFT + 1); |
537 |
< |
private static final int TERMINATED = 1 << (RUNLEVEL_SHIFT + 2); |
538 |
< |
private static final int ACTIVE_COUNT_MASK = (1 << RUNLEVEL_SHIFT) - 1; |
521 |
> |
final int parallelism; |
522 |
|
|
523 |
|
/** |
524 |
< |
* Holds number of total (i.e., created and not yet terminated) |
525 |
< |
* and running (i.e., not blocked on joins or other managed sync) |
543 |
< |
* threads, packed together to ensure consistent snapshot when |
544 |
< |
* making decisions about creating and suspending spare |
545 |
< |
* threads. Updated only by CAS. Note that adding a new worker |
546 |
< |
* requires incrementing both counts, since workers start off in |
547 |
< |
* running state. |
524 |
> |
* Index (mod submission queue length) of next element to take |
525 |
> |
* from submission queue. |
526 |
|
*/ |
527 |
< |
private volatile int workerCounts; |
527 |
> |
volatile int queueBase; |
528 |
|
|
529 |
< |
private static final int TOTAL_COUNT_SHIFT = 16; |
530 |
< |
private static final int RUNNING_COUNT_MASK = (1 << TOTAL_COUNT_SHIFT) - 1; |
531 |
< |
private static final int ONE_RUNNING = 1; |
532 |
< |
private static final int ONE_TOTAL = 1 << TOTAL_COUNT_SHIFT; |
529 |
> |
/** |
530 |
> |
* Index (mod submission queue length) of next element to add |
531 |
> |
* in submission queue. |
532 |
> |
*/ |
533 |
> |
int queueTop; |
534 |
|
|
535 |
|
/** |
536 |
< |
* The target parallelism level. |
558 |
< |
* Accessed directly by ForkJoinWorkerThreads. |
536 |
> |
* True when shutdown() has been called. |
537 |
|
*/ |
538 |
< |
final int parallelism; |
538 |
> |
volatile boolean shutdown; |
539 |
|
|
540 |
|
/** |
541 |
|
* True if use local fifo, not default lifo, for local polling |
544 |
|
final boolean locallyFifo; |
545 |
|
|
546 |
|
/** |
547 |
< |
* The uncaught exception handler used when any worker abruptly |
548 |
< |
* terminates. |
547 |
> |
* The number of threads in ForkJoinWorkerThreads.helpQuiescePool. |
548 |
> |
* When non-zero, suppresses automatic shutdown when active |
549 |
> |
* counts become zero. |
550 |
|
*/ |
551 |
< |
private final Thread.UncaughtExceptionHandler ueh; |
551 |
> |
volatile int quiescerCount; |
552 |
|
|
553 |
|
/** |
554 |
< |
* Pool number, just for assigning useful names to worker threads |
554 |
> |
* The number of threads blocked in join. |
555 |
|
*/ |
556 |
< |
private final int poolNumber; |
578 |
< |
|
579 |
< |
// Utilities for CASing fields. Note that most of these |
580 |
< |
// are usually manually inlined by callers |
556 |
> |
volatile int blockedCount; |
557 |
|
|
558 |
|
/** |
559 |
< |
* Increments running count part of workerCounts |
559 |
> |
* Counter for worker Thread names (unrelated to their poolIndex) |
560 |
|
*/ |
561 |
< |
final void incrementRunningCount() { |
586 |
< |
int c; |
587 |
< |
do {} while (!UNSAFE.compareAndSwapInt(this, workerCountsOffset, |
588 |
< |
c = workerCounts, |
589 |
< |
c + ONE_RUNNING)); |
590 |
< |
} |
561 |
> |
private volatile int nextWorkerNumber; |
562 |
|
|
563 |
|
/** |
564 |
< |
* Tries to decrement running count unless already zero |
564 |
> |
* The index for the next created worker. Accessed under scanGuard. |
565 |
|
*/ |
566 |
< |
final boolean tryDecrementRunningCount() { |
596 |
< |
int wc = workerCounts; |
597 |
< |
if ((wc & RUNNING_COUNT_MASK) == 0) |
598 |
< |
return false; |
599 |
< |
return UNSAFE.compareAndSwapInt(this, workerCountsOffset, |
600 |
< |
wc, wc - ONE_RUNNING); |
601 |
< |
} |
566 |
> |
private int nextWorkerIndex; |
567 |
|
|
568 |
|
/** |
569 |
< |
* Forces decrement of encoded workerCounts, awaiting nonzero if |
570 |
< |
* (rarely) necessary when other count updates lag. |
571 |
< |
* |
572 |
< |
* @param dr -- either zero or ONE_RUNNING |
573 |
< |
* @param dt == either zero or ONE_TOTAL |
569 |
> |
* SeqLock and index masking for for updates to workers array. |
570 |
> |
* Locked when SG_UNIT is set. Unlocking clears bit by adding |
571 |
> |
* SG_UNIT. Staleness of read-only operations can be checked by |
572 |
> |
* comparing scanGuard to value before the reads. The low 16 bits |
573 |
> |
* (i.e, anding with SMASK) hold (the smallest power of two |
574 |
> |
* covering all worker indices, minus one, and is used to avoid |
575 |
> |
* dealing with large numbers of null slots when the workers array |
576 |
> |
* is overallocated. |
577 |
|
*/ |
578 |
< |
private void decrementWorkerCounts(int dr, int dt) { |
579 |
< |
for (;;) { |
580 |
< |
int wc = workerCounts; |
613 |
< |
if ((wc & RUNNING_COUNT_MASK) - dr < 0 || |
614 |
< |
(wc >>> TOTAL_COUNT_SHIFT) - dt < 0) { |
615 |
< |
if ((runState & TERMINATED) != 0) |
616 |
< |
return; // lagging termination on a backout |
617 |
< |
Thread.yield(); |
618 |
< |
} |
619 |
< |
if (UNSAFE.compareAndSwapInt(this, workerCountsOffset, |
620 |
< |
wc, wc - (dr + dt))) |
621 |
< |
return; |
622 |
< |
} |
623 |
< |
} |
578 |
> |
volatile int scanGuard; |
579 |
> |
|
580 |
> |
private static final int SG_UNIT = 1 << 16; |
581 |
|
|
582 |
|
/** |
583 |
< |
* Tries decrementing active count; fails on contention. |
584 |
< |
* Called when workers cannot find tasks to run. |
583 |
> |
* The wakeup interval (in nanoseconds) for a worker waiting for a |
584 |
> |
* task when the pool is quiescent to instead try to shrink the |
585 |
> |
* number of workers. The exact value does not matter too |
586 |
> |
* much. It must be short enough to release resources during |
587 |
> |
* sustained periods of idleness, but not so short that threads |
588 |
> |
* are continually re-created. |
589 |
|
*/ |
590 |
< |
final boolean tryDecrementActiveCount() { |
591 |
< |
int c; |
631 |
< |
return UNSAFE.compareAndSwapInt(this, runStateOffset, |
632 |
< |
c = runState, c - 1); |
633 |
< |
} |
590 |
> |
private static final long SHRINK_RATE = |
591 |
> |
4L * 1000L * 1000L * 1000L; // 4 seconds |
592 |
|
|
593 |
|
/** |
594 |
< |
* Advances to at least the given level. Returns true if not |
595 |
< |
* already in at least the given level. |
594 |
> |
* Top-level loop for worker threads: On each step: if the |
595 |
> |
* previous step swept through all queues and found no tasks, or |
596 |
> |
* there are excess threads, then possibly blocks. Otherwise, |
597 |
> |
* scans for and, if found, executes a task. Returns when pool |
598 |
> |
* and/or worker terminate. |
599 |
> |
* |
600 |
> |
* @param w the worker |
601 |
|
*/ |
602 |
< |
private boolean advanceRunLevel(int level) { |
603 |
< |
for (;;) { |
604 |
< |
int s = runState; |
605 |
< |
if ((s & level) != 0) |
606 |
< |
return false; |
607 |
< |
if (UNSAFE.compareAndSwapInt(this, runStateOffset, s, s | level)) |
608 |
< |
return true; |
602 |
> |
final void work(ForkJoinWorkerThread w) { |
603 |
> |
boolean swept = false; // true on empty scans |
604 |
> |
long c; |
605 |
> |
while (!w.terminate && (int)(c = ctl) >= 0) { |
606 |
> |
int a; // active count |
607 |
> |
if (!swept && (a = (int)(c >> AC_SHIFT)) <= 0) |
608 |
> |
swept = scan(w, a); |
609 |
> |
else if (tryAwaitWork(w, c)) |
610 |
> |
swept = false; |
611 |
|
} |
612 |
|
} |
613 |
|
|
614 |
< |
// workers array maintenance |
614 |
> |
// Signalling |
615 |
|
|
616 |
|
/** |
617 |
< |
* Records and returns a workers array index for new worker. |
617 |
> |
* Wakes up or creates a worker. |
618 |
|
*/ |
619 |
< |
private int recordWorker(ForkJoinWorkerThread w) { |
620 |
< |
// Try using slot totalCount-1. If not available, scan and/or resize |
621 |
< |
int k = (workerCounts >>> TOTAL_COUNT_SHIFT) - 1; |
622 |
< |
final ReentrantLock lock = this.workerLock; |
623 |
< |
lock.lock(); |
624 |
< |
try { |
625 |
< |
ForkJoinWorkerThread[] ws = workers; |
626 |
< |
int n = ws.length; |
627 |
< |
if (k < 0 || k >= n || ws[k] != null) { |
628 |
< |
for (k = 0; k < n && ws[k] != null; ++k) |
629 |
< |
; |
630 |
< |
if (k == n) |
631 |
< |
ws = Arrays.copyOf(ws, n << 1); |
619 |
> |
final void signalWork() { |
620 |
> |
/* |
621 |
> |
* The while condition is true if: (there is are too few total |
622 |
> |
* workers OR there is at least one waiter) AND (there are too |
623 |
> |
* few active workers OR the pool is terminating). The value |
624 |
> |
* of e distinguishes the remaining cases: zero (no waiters) |
625 |
> |
* for create, negative if terminating (in which case do |
626 |
> |
* nothing), else release a waiter. The secondary checks for |
627 |
> |
* release (non-null array etc) can fail if the pool begins |
628 |
> |
* terminating after the test, and don't impose any added cost |
629 |
> |
* because JVMs must perform null and bounds checks anyway. |
630 |
> |
*/ |
631 |
> |
long c; int e, u; |
632 |
> |
while ((((e = (int)(c = ctl)) | (u = (int)(c >>> 32))) & |
633 |
> |
(INT_SIGN|SHORT_SIGN)) == (INT_SIGN|SHORT_SIGN) && e >= 0) { |
634 |
> |
if (e > 0) { // release a waiting worker |
635 |
> |
int i; ForkJoinWorkerThread w; ForkJoinWorkerThread[] ws; |
636 |
> |
if ((ws = workers) == null || |
637 |
> |
(i = ~e & SMASK) >= ws.length || |
638 |
> |
(w = ws[i]) == null) |
639 |
> |
break; |
640 |
> |
long nc = (((long)(w.nextWait & E_MASK)) | |
641 |
> |
((long)(u + UAC_UNIT) << 32)); |
642 |
> |
if (w.eventCount == e && |
643 |
> |
UNSAFE.compareAndSwapLong(this, ctlOffset, c, nc)) { |
644 |
> |
w.eventCount = (e + EC_UNIT) & E_MASK; |
645 |
> |
if (w.parked) |
646 |
> |
UNSAFE.unpark(w); |
647 |
> |
break; |
648 |
> |
} |
649 |
> |
} |
650 |
> |
else if (UNSAFE.compareAndSwapLong |
651 |
> |
(this, ctlOffset, c, |
652 |
> |
(long)(((u + UTC_UNIT) & UTC_MASK) | |
653 |
> |
((u + UAC_UNIT) & UAC_MASK)) << 32)) { |
654 |
> |
addWorker(); |
655 |
> |
break; |
656 |
|
} |
668 |
– |
ws[k] = w; |
669 |
– |
workers = ws; // volatile array write ensures slot visibility |
670 |
– |
} finally { |
671 |
– |
lock.unlock(); |
657 |
|
} |
673 |
– |
return k; |
658 |
|
} |
659 |
|
|
660 |
|
/** |
661 |
< |
* Nulls out record of worker in workers array |
661 |
> |
* Variant of signalWork to help release waiters on rescans. |
662 |
> |
* Tries once to release a waiter if active count < 0. |
663 |
> |
* |
664 |
> |
* @return false if failed due to contention, else true |
665 |
|
*/ |
666 |
< |
private void forgetWorker(ForkJoinWorkerThread w) { |
667 |
< |
int idx = w.poolIndex; |
668 |
< |
// Locking helps method recordWorker avoid unnecessary expansion |
669 |
< |
final ReentrantLock lock = this.workerLock; |
670 |
< |
lock.lock(); |
671 |
< |
try { |
672 |
< |
ForkJoinWorkerThread[] ws = workers; |
673 |
< |
if (idx >= 0 && idx < ws.length && ws[idx] == w) // verify |
674 |
< |
ws[idx] = null; |
675 |
< |
} finally { |
676 |
< |
lock.unlock(); |
666 |
> |
private boolean tryReleaseWaiter() { |
667 |
> |
long c; int e, i; ForkJoinWorkerThread w; ForkJoinWorkerThread[] ws; |
668 |
> |
if ((e = (int)(c = ctl)) > 0 && |
669 |
> |
(int)(c >> AC_SHIFT) < 0 && |
670 |
> |
(ws = workers) != null && |
671 |
> |
(i = ~e & SMASK) < ws.length && |
672 |
> |
(w = ws[i]) != null) { |
673 |
> |
long nc = ((long)(w.nextWait & E_MASK) | |
674 |
> |
((c + AC_UNIT) & (AC_MASK|TC_MASK))); |
675 |
> |
if (w.eventCount != e || |
676 |
> |
!UNSAFE.compareAndSwapLong(this, ctlOffset, c, nc)) |
677 |
> |
return false; |
678 |
> |
w.eventCount = (e + EC_UNIT) & E_MASK; |
679 |
> |
if (w.parked) |
680 |
> |
UNSAFE.unpark(w); |
681 |
|
} |
682 |
+ |
return true; |
683 |
|
} |
684 |
|
|
685 |
+ |
// Scanning for tasks |
686 |
+ |
|
687 |
|
/** |
688 |
< |
* Final callback from terminating worker. Removes record of |
689 |
< |
* worker from array, and adjusts counts. If pool is shutting |
690 |
< |
* down, tries to complete termination. |
688 |
> |
* Scans for and, if found, executes one task. Scans start at a |
689 |
> |
* random index of workers array, and randomly select the first |
690 |
> |
* (2*#workers)-1 probes, and then, if all empty, resort to 2 |
691 |
> |
* circular sweeps, which is necessary to check quiescence. and |
692 |
> |
* taking a submission only if no stealable tasks were found. The |
693 |
> |
* steal code inside the loop is a specialized form of |
694 |
> |
* ForkJoinWorkerThread.deqTask, followed bookkeeping to support |
695 |
> |
* helpJoinTask and signal propagation. The code for submission |
696 |
> |
* queues is almost identical. On each steal, the worker completes |
697 |
> |
* not only the task, but also all local tasks that this task may |
698 |
> |
* have generated. On detecting staleness or contention when |
699 |
> |
* trying to take a task, this method returns without finishing |
700 |
> |
* sweep, which allows global state rechecks before retry. |
701 |
|
* |
702 |
|
* @param w the worker |
703 |
+ |
* @param a the number of active workers |
704 |
+ |
* @return true if swept all queues without finding a task |
705 |
|
*/ |
706 |
< |
final void workerTerminated(ForkJoinWorkerThread w) { |
707 |
< |
forgetWorker(w); |
708 |
< |
decrementWorkerCounts(w.isTrimmed()? 0 : ONE_RUNNING, ONE_TOTAL); |
703 |
< |
while (w.stealCount != 0) // collect final count |
704 |
< |
tryAccumulateStealCount(w); |
705 |
< |
tryTerminate(false); |
706 |
< |
} |
707 |
< |
|
708 |
< |
// Waiting for and signalling events |
709 |
< |
|
710 |
< |
/** |
711 |
< |
* Releases workers blocked on a count not equal to current count. |
712 |
< |
* Normally called after precheck that eventWaiters isn't zero to |
713 |
< |
* avoid wasted array checks. Gives up upon a change in count or |
714 |
< |
* upon releasing two workers, letting others take over. |
715 |
< |
*/ |
716 |
< |
private void releaseEventWaiters() { |
706 |
> |
private boolean scan(ForkJoinWorkerThread w, int a) { |
707 |
> |
int g = scanGuard; // mask 0 avoids useless scans if only one active |
708 |
> |
int m = parallelism == 1 - a? 0 : g & SMASK; |
709 |
|
ForkJoinWorkerThread[] ws = workers; |
710 |
< |
int n = ws.length; |
711 |
< |
long h = eventWaiters; |
712 |
< |
int ec = eventCount; |
713 |
< |
boolean releasedOne = false; |
714 |
< |
ForkJoinWorkerThread w; int id; |
715 |
< |
while ((id = ((int)(h & WAITER_ID_MASK)) - 1) >= 0 && |
716 |
< |
(int)(h >>> EVENT_COUNT_SHIFT) != ec && |
717 |
< |
id < n && (w = ws[id]) != null) { |
718 |
< |
if (UNSAFE.compareAndSwapLong(this, eventWaitersOffset, |
719 |
< |
h, w.nextWaiter)) { |
720 |
< |
LockSupport.unpark(w); |
721 |
< |
if (releasedOne) // exit on second release |
722 |
< |
break; |
723 |
< |
releasedOne = true; |
710 |
> |
if (ws == null || ws.length <= m) // staleness check |
711 |
> |
return false; |
712 |
> |
for (int r = w.seed, k = r, j = -(m + m); j <= m + m; ++j) { |
713 |
> |
ForkJoinTask<?> t; ForkJoinTask<?>[] q; int b, i; |
714 |
> |
ForkJoinWorkerThread v = ws[k & m]; |
715 |
> |
if (v != null && (b = v.queueBase) != v.queueTop && |
716 |
> |
(q = v.queue) != null && (i = (q.length - 1) & b) >= 0) { |
717 |
> |
long u = (i << ASHIFT) + ABASE; |
718 |
> |
if ((t = q[i]) != null && v.queueBase == b && |
719 |
> |
UNSAFE.compareAndSwapObject(q, u, t, null)) { |
720 |
> |
int d = (v.queueBase = b + 1) - v.queueTop; |
721 |
> |
v.stealHint = w.poolIndex; |
722 |
> |
if (d != 0) |
723 |
> |
signalWork(); // propagate if nonempty |
724 |
> |
w.execTask(t); |
725 |
> |
} |
726 |
> |
r ^= r << 13; r ^= r >>> 17; w.seed = r ^ (r << 5); |
727 |
> |
return false; // store next seed |
728 |
|
} |
729 |
< |
if (eventCount != ec) |
730 |
< |
break; |
731 |
< |
h = eventWaiters; |
729 |
> |
else if (j < 0) { // xorshift |
730 |
> |
r ^= r << 13; r ^= r >>> 17; k = r ^= r << 5; |
731 |
> |
} |
732 |
> |
else |
733 |
> |
++k; |
734 |
> |
} |
735 |
> |
if (scanGuard != g) // staleness check |
736 |
> |
return false; |
737 |
> |
else { // try to take submission |
738 |
> |
ForkJoinTask<?> t; ForkJoinTask<?>[] q; int b, i; |
739 |
> |
if ((b = queueBase) != queueTop && |
740 |
> |
(q = submissionQueue) != null && |
741 |
> |
(i = (q.length - 1) & b) >= 0) { |
742 |
> |
long u = (i << ASHIFT) + ABASE; |
743 |
> |
if ((t = q[i]) != null && queueBase == b && |
744 |
> |
UNSAFE.compareAndSwapObject(q, u, t, null)) { |
745 |
> |
queueBase = b + 1; |
746 |
> |
w.execTask(t); |
747 |
> |
} |
748 |
> |
return false; |
749 |
> |
} |
750 |
> |
return true; // all queues empty |
751 |
|
} |
752 |
|
} |
753 |
|
|
754 |
|
/** |
755 |
< |
* Tries to advance eventCount and releases waiters. Called only |
756 |
< |
* from workers. |
757 |
< |
*/ |
758 |
< |
final void signalWork() { |
759 |
< |
int c; // try to increment event count -- CAS failure OK |
760 |
< |
UNSAFE.compareAndSwapInt(this, eventCountOffset, c = eventCount, c+1); |
761 |
< |
if (eventWaiters != 0L) |
762 |
< |
releaseEventWaiters(); |
763 |
< |
} |
764 |
< |
|
765 |
< |
/** |
766 |
< |
* Adds the given worker to event queue and blocks until |
767 |
< |
* terminating or event count advances from the given value |
768 |
< |
* |
769 |
< |
* @param w the calling worker thread |
770 |
< |
* @param ec the count |
771 |
< |
*/ |
772 |
< |
private void eventSync(ForkJoinWorkerThread w, int ec) { |
773 |
< |
long nh = (((long)ec) << EVENT_COUNT_SHIFT) | ((long)(w.poolIndex+1)); |
774 |
< |
long h; |
775 |
< |
while ((runState < SHUTDOWN || !tryTerminate(false)) && |
776 |
< |
(((int)((h = eventWaiters) & WAITER_ID_MASK)) == 0 || |
777 |
< |
(int)(h >>> EVENT_COUNT_SHIFT) == ec) && |
778 |
< |
eventCount == ec) { |
779 |
< |
if (UNSAFE.compareAndSwapLong(this, eventWaitersOffset, |
780 |
< |
w.nextWaiter = h, nh)) { |
781 |
< |
awaitEvent(w, ec); |
782 |
< |
break; |
755 |
> |
* Tries to enqueue worker w in wait queue and await change in |
756 |
> |
* worker's eventCount. If the pool is quiescent, possibly |
757 |
> |
* terminates worker upon exit. Otherwise, before blocking, |
758 |
> |
* rescans queues to avoid missed signals. Upon finding work, |
759 |
> |
* releases at least one worker (which may be the current |
760 |
> |
* worker). Rescans restart upon detected staleness or failure to |
761 |
> |
* release due to contention. |
762 |
> |
* |
763 |
> |
* @param w the calling worker |
764 |
> |
* @param c the ctl value on entry |
765 |
> |
* @return true if waited or another thread was released upon enq |
766 |
> |
*/ |
767 |
> |
private boolean tryAwaitWork(ForkJoinWorkerThread w, long c) { |
768 |
> |
int v = w.eventCount; |
769 |
> |
w.nextWait = (int)c; // w's successor record |
770 |
> |
long nc = (long)(v & E_MASK) | ((c - AC_UNIT) & (AC_MASK|TC_MASK)); |
771 |
> |
if (ctl != c || !UNSAFE.compareAndSwapLong(this, ctlOffset, c, nc)) { |
772 |
> |
long d = ctl; // return true if lost to a deq, to force scan |
773 |
> |
return (int)d != (int)c && ((d - c) & AC_MASK) >= 0L; |
774 |
> |
} |
775 |
> |
for (int sc = w.stealCount; sc != 0;) { // accumulate stealCount |
776 |
> |
long s = stealCount; |
777 |
> |
if (UNSAFE.compareAndSwapLong(this, stealCountOffset, s, s + sc)) |
778 |
> |
sc = w.stealCount = 0; |
779 |
> |
else if (w.eventCount != v) |
780 |
> |
return true; // update next time |
781 |
> |
} |
782 |
> |
if (parallelism + (int)(nc >> AC_SHIFT) == 0 && |
783 |
> |
blockedCount == 0 && quiescerCount == 0) |
784 |
> |
idleAwaitWork(w, nc, c, v); // quiescent |
785 |
> |
for (boolean rescanned = false;;) { |
786 |
> |
if (w.eventCount != v) |
787 |
> |
return true; |
788 |
> |
if (!rescanned) { |
789 |
> |
int g = scanGuard, m = g & SMASK; |
790 |
> |
ForkJoinWorkerThread[] ws = workers; |
791 |
> |
if (ws != null && m < ws.length) { |
792 |
> |
rescanned = true; |
793 |
> |
for (int i = 0; i <= m; ++i) { |
794 |
> |
ForkJoinWorkerThread u = ws[i]; |
795 |
> |
if (u != null) { |
796 |
> |
if (u.queueBase != u.queueTop && |
797 |
> |
!tryReleaseWaiter()) |
798 |
> |
rescanned = false; // contended |
799 |
> |
if (w.eventCount != v) |
800 |
> |
return true; |
801 |
> |
} |
802 |
> |
} |
803 |
> |
} |
804 |
> |
if (scanGuard != g || // stale |
805 |
> |
(queueBase != queueTop && !tryReleaseWaiter())) |
806 |
> |
rescanned = false; |
807 |
> |
if (!rescanned) |
808 |
> |
Thread.yield(); // reduce contention |
809 |
> |
else |
810 |
> |
Thread.interrupted(); // clear before park |
811 |
> |
} |
812 |
> |
else { |
813 |
> |
w.parked = true; // must recheck |
814 |
> |
if (w.eventCount != v) { |
815 |
> |
w.parked = false; |
816 |
> |
return true; |
817 |
> |
} |
818 |
> |
LockSupport.park(this); |
819 |
> |
rescanned = w.parked = false; |
820 |
|
} |
821 |
|
} |
822 |
|
} |
823 |
|
|
824 |
|
/** |
825 |
< |
* Blocks the given worker (that has already been entered as an |
826 |
< |
* event waiter) until terminating or event count advances from |
827 |
< |
* the given value. The oldest (first) waiter uses a timed wait to |
828 |
< |
* occasionally one-by-one shrink the number of workers (to a |
829 |
< |
* minimum of one) if the pool has not been used for extended |
830 |
< |
* periods. |
831 |
< |
* |
832 |
< |
* @param w the calling worker thread |
833 |
< |
* @param ec the count |
834 |
< |
*/ |
835 |
< |
private void awaitEvent(ForkJoinWorkerThread w, int ec) { |
836 |
< |
while (eventCount == ec) { |
837 |
< |
if (tryAccumulateStealCount(w)) { // transfer while idle |
838 |
< |
boolean untimed = (w.nextWaiter != 0L || |
839 |
< |
(workerCounts & RUNNING_COUNT_MASK) <= 1); |
840 |
< |
long startTime = untimed? 0 : System.nanoTime(); |
841 |
< |
Thread.interrupted(); // clear/ignore interrupt |
842 |
< |
if (eventCount != ec || w.runState != 0 || |
843 |
< |
runState >= TERMINATING) // recheck after clear |
825 |
> |
* If inactivating worker w has caused pool to become |
826 |
> |
* quiescent, check for pool termination, and wait for event |
827 |
> |
* for up to SHRINK_RATE nanosecs (rescans are unnecessary in |
828 |
> |
* this case because quiescence reflects consensus about lack |
829 |
> |
* of work). On timeout, if ctl has not changed, terminate the |
830 |
> |
* worker. Upon its termination (see deregisterWorker), it may |
831 |
> |
* wake up another worker to possibly repeat this process. |
832 |
> |
* |
833 |
> |
* @param w the calling worker |
834 |
> |
* @param currentCtl the ctl value after enqueuing w |
835 |
> |
* @param prevCtl the ctl value if w terminated |
836 |
> |
* @param v the eventCount w awaits change |
837 |
> |
*/ |
838 |
> |
private void idleAwaitWork(ForkJoinWorkerThread w, long currentCtl, |
839 |
> |
long prevCtl, int v) { |
840 |
> |
if (w.eventCount == v) { |
841 |
> |
if (shutdown) |
842 |
> |
tryTerminate(false); |
843 |
> |
ForkJoinTask.helpExpungeStaleExceptions(); // help clean weak refs |
844 |
> |
while (ctl == currentCtl) { |
845 |
> |
long startTime = System.nanoTime(); |
846 |
> |
w.parked = true; |
847 |
> |
if (w.eventCount == v) // must recheck |
848 |
> |
LockSupport.parkNanos(this, SHRINK_RATE); |
849 |
> |
w.parked = false; |
850 |
> |
if (w.eventCount != v) |
851 |
> |
break; |
852 |
> |
else if (System.nanoTime() - startTime < SHRINK_RATE) |
853 |
> |
Thread.interrupted(); // spurious wakeup |
854 |
> |
else if (UNSAFE.compareAndSwapLong(this, ctlOffset, |
855 |
> |
currentCtl, prevCtl)) { |
856 |
> |
w.terminate = true; // restore previous |
857 |
> |
w.eventCount = ((int)currentCtl + EC_UNIT) & E_MASK; |
858 |
|
break; |
793 |
– |
if (untimed) |
794 |
– |
LockSupport.park(w); |
795 |
– |
else { |
796 |
– |
LockSupport.parkNanos(w, SHRINK_RATE_NANOS); |
797 |
– |
if (eventCount != ec || w.runState != 0 || |
798 |
– |
runState >= TERMINATING) |
799 |
– |
break; |
800 |
– |
if (System.nanoTime() - startTime >= SHRINK_RATE_NANOS) |
801 |
– |
tryShutdownUnusedWorker(ec); |
859 |
|
} |
860 |
|
} |
861 |
|
} |
862 |
|
} |
863 |
|
|
864 |
< |
// Maintaining parallelism |
864 |
> |
// Submissions |
865 |
|
|
866 |
|
/** |
867 |
< |
* Pushes worker onto the spare stack |
867 |
> |
* Enqueues the given task in the submissionQueue. Same idea as |
868 |
> |
* ForkJoinWorkerThread.pushTask except for use of submissionLock. |
869 |
> |
* |
870 |
> |
* @param t the task |
871 |
|
*/ |
872 |
< |
final void pushSpare(ForkJoinWorkerThread w) { |
873 |
< |
int ns = (++w.spareCount << SPARE_COUNT_SHIFT) | (w.poolIndex + 1); |
874 |
< |
do {} while (!UNSAFE.compareAndSwapInt(this, spareWaitersOffset, |
875 |
< |
w.nextSpare = spareWaiters,ns)); |
872 |
> |
private void addSubmission(ForkJoinTask<?> t) { |
873 |
> |
final ReentrantLock lock = this.submissionLock; |
874 |
> |
lock.lock(); |
875 |
> |
try { |
876 |
> |
ForkJoinTask<?>[] q; int s, m; |
877 |
> |
if ((q = submissionQueue) != null) { // ignore if queue removed |
878 |
> |
long u = (((s = queueTop) & (m = q.length-1)) << ASHIFT)+ABASE; |
879 |
> |
UNSAFE.putOrderedObject(q, u, t); |
880 |
> |
queueTop = s + 1; |
881 |
> |
if (s - queueBase == m) |
882 |
> |
growSubmissionQueue(); |
883 |
> |
} |
884 |
> |
} finally { |
885 |
> |
lock.unlock(); |
886 |
> |
} |
887 |
> |
signalWork(); |
888 |
|
} |
889 |
|
|
890 |
+ |
// (pollSubmission is defined below with exported methods) |
891 |
+ |
|
892 |
|
/** |
893 |
< |
* Tries (once) to resume a spare if the number of running |
894 |
< |
* threads is less than target. |
893 |
> |
* Creates or doubles submissionQueue array. |
894 |
> |
* Basically identical to ForkJoinWorkerThread version |
895 |
|
*/ |
896 |
< |
private void tryResumeSpare() { |
897 |
< |
int sw, id; |
898 |
< |
ForkJoinWorkerThread[] ws = workers; |
899 |
< |
int n = ws.length; |
900 |
< |
ForkJoinWorkerThread w; |
901 |
< |
if ((sw = spareWaiters) != 0 && |
902 |
< |
(id = (sw & SPARE_ID_MASK) - 1) >= 0 && |
903 |
< |
id < n && (w = ws[id]) != null && |
904 |
< |
(workerCounts & RUNNING_COUNT_MASK) < parallelism && |
905 |
< |
spareWaiters == sw && |
906 |
< |
UNSAFE.compareAndSwapInt(this, spareWaitersOffset, |
907 |
< |
sw, w.nextSpare)) { |
908 |
< |
int c; // increment running count before resume |
909 |
< |
do {} while(!UNSAFE.compareAndSwapInt |
910 |
< |
(this, workerCountsOffset, |
911 |
< |
c = workerCounts, c + ONE_RUNNING)); |
912 |
< |
if (w.tryUnsuspend()) |
913 |
< |
LockSupport.unpark(w); |
914 |
< |
else // back out if w was shutdown |
841 |
< |
decrementWorkerCounts(ONE_RUNNING, 0); |
896 |
> |
private void growSubmissionQueue() { |
897 |
> |
ForkJoinTask<?>[] oldQ = submissionQueue; |
898 |
> |
int size = oldQ != null ? oldQ.length << 1 : INITIAL_QUEUE_CAPACITY; |
899 |
> |
if (size > MAXIMUM_QUEUE_CAPACITY) |
900 |
> |
throw new RejectedExecutionException("Queue capacity exceeded"); |
901 |
> |
if (size < INITIAL_QUEUE_CAPACITY) |
902 |
> |
size = INITIAL_QUEUE_CAPACITY; |
903 |
> |
ForkJoinTask<?>[] q = submissionQueue = new ForkJoinTask<?>[size]; |
904 |
> |
int mask = size - 1; |
905 |
> |
int top = queueTop; |
906 |
> |
int oldMask; |
907 |
> |
if (oldQ != null && (oldMask = oldQ.length - 1) >= 0) { |
908 |
> |
for (int b = queueBase; b != top; ++b) { |
909 |
> |
long u = ((b & oldMask) << ASHIFT) + ABASE; |
910 |
> |
Object x = UNSAFE.getObjectVolatile(oldQ, u); |
911 |
> |
if (x != null && UNSAFE.compareAndSwapObject(oldQ, u, x, null)) |
912 |
> |
UNSAFE.putObjectVolatile |
913 |
> |
(q, ((b & mask) << ASHIFT) + ABASE, x); |
914 |
> |
} |
915 |
|
} |
916 |
|
} |
917 |
|
|
918 |
+ |
// Blocking support |
919 |
+ |
|
920 |
|
/** |
921 |
< |
* Tries to increase the number of running workers if below target |
922 |
< |
* parallelism: If a spare exists tries to resume it via |
923 |
< |
* tryResumeSpare. Otherwise, if not enough total workers or all |
924 |
< |
* existing workers are busy, adds a new worker. In all cases also |
925 |
< |
* helps wake up releasable workers waiting for work. |
926 |
< |
*/ |
927 |
< |
private void helpMaintainParallelism() { |
928 |
< |
int pc = parallelism; |
929 |
< |
int wc, rs, tc; |
930 |
< |
while (((wc = workerCounts) & RUNNING_COUNT_MASK) < pc && |
931 |
< |
(rs = runState) < TERMINATING) { |
932 |
< |
if (spareWaiters != 0) |
933 |
< |
tryResumeSpare(); |
934 |
< |
else if ((tc = wc >>> TOTAL_COUNT_SHIFT) >= MAX_WORKERS || |
935 |
< |
(tc >= pc && (rs & ACTIVE_COUNT_MASK) != tc)) |
936 |
< |
break; // enough total |
937 |
< |
else if (runState == rs && workerCounts == wc && |
938 |
< |
UNSAFE.compareAndSwapInt(this, workerCountsOffset, wc, |
939 |
< |
wc + (ONE_RUNNING|ONE_TOTAL))) { |
940 |
< |
ForkJoinWorkerThread w = null; |
941 |
< |
try { |
942 |
< |
w = factory.newThread(this); |
943 |
< |
} finally { // adjust on null or exceptional factory return |
944 |
< |
if (w == null) { |
945 |
< |
decrementWorkerCounts(ONE_RUNNING, ONE_TOTAL); |
946 |
< |
tryTerminate(false); // handle failure during shutdown |
921 |
> |
* Tries to increment blockedCount, decrement active count |
922 |
> |
* (sometimes implicitly) and possibly release or create a |
923 |
> |
* compensating worker in preparation for blocking. Fails |
924 |
> |
* on contention or termination. |
925 |
> |
* |
926 |
> |
* @return true if the caller can block, else should recheck and retry |
927 |
> |
*/ |
928 |
> |
private boolean tryPreBlock() { |
929 |
> |
int b = blockedCount; |
930 |
> |
if (UNSAFE.compareAndSwapInt(this, blockedCountOffset, b, b + 1)) { |
931 |
> |
int pc = parallelism; |
932 |
> |
do { |
933 |
> |
ForkJoinWorkerThread[] ws; ForkJoinWorkerThread w; |
934 |
> |
int e, ac, tc, rc, i; |
935 |
> |
long c = ctl; |
936 |
> |
int u = (int)(c >>> 32); |
937 |
> |
if ((e = (int)c) < 0) { |
938 |
> |
// skip -- terminating |
939 |
> |
} |
940 |
> |
else if ((ac = (u >> UAC_SHIFT)) <= 0 && e != 0 && |
941 |
> |
(ws = workers) != null && |
942 |
> |
(i = ~e & SMASK) < ws.length && |
943 |
> |
(w = ws[i]) != null) { |
944 |
> |
long nc = ((long)(w.nextWait & E_MASK) | |
945 |
> |
(c & (AC_MASK|TC_MASK))); |
946 |
> |
if (w.eventCount == e && |
947 |
> |
UNSAFE.compareAndSwapLong(this, ctlOffset, c, nc)) { |
948 |
> |
w.eventCount = (e + EC_UNIT) & E_MASK; |
949 |
> |
if (w.parked) |
950 |
> |
UNSAFE.unpark(w); |
951 |
> |
return true; // release an idle worker |
952 |
|
} |
953 |
|
} |
954 |
< |
if (w == null) |
955 |
< |
break; |
956 |
< |
w.start(recordWorker(w), ueh); |
957 |
< |
if ((workerCounts >>> TOTAL_COUNT_SHIFT) >= pc) { |
878 |
< |
int c; // advance event count |
879 |
< |
UNSAFE.compareAndSwapInt(this, eventCountOffset, |
880 |
< |
c = eventCount, c+1); |
881 |
< |
break; // add at most one unless total below target |
954 |
> |
else if ((tc = (short)(u >>> UTC_SHIFT)) >= 0 && ac + pc > 1) { |
955 |
> |
long nc = ((c - AC_UNIT) & AC_MASK) | (c & ~AC_MASK); |
956 |
> |
if (UNSAFE.compareAndSwapLong(this, ctlOffset, c, nc)) |
957 |
> |
return true; // no compensation needed |
958 |
|
} |
959 |
< |
} |
959 |
> |
else if (tc + pc < MAX_ID) { |
960 |
> |
long nc = ((c + TC_UNIT) & TC_MASK) | (c & ~TC_MASK); |
961 |
> |
if (UNSAFE.compareAndSwapLong(this, ctlOffset, c, nc)) { |
962 |
> |
addWorker(); |
963 |
> |
return true; // create a replacement |
964 |
> |
} |
965 |
> |
} |
966 |
> |
// try to back out on any failure and let caller retry |
967 |
> |
} while (!UNSAFE.compareAndSwapInt(this, blockedCountOffset, |
968 |
> |
b = blockedCount, b - 1)); |
969 |
|
} |
970 |
< |
if (eventWaiters != 0L) |
886 |
< |
releaseEventWaiters(); |
970 |
> |
return false; |
971 |
|
} |
972 |
|
|
973 |
|
/** |
974 |
< |
* Callback from the oldest waiter in awaitEvent waking up after a |
891 |
< |
* period of non-use. If all workers are idle, tries (once) to |
892 |
< |
* shutdown an event waiter or a spare, if one exists. Note that |
893 |
< |
* we don't need CAS or locks here because the method is called |
894 |
< |
* only from one thread occasionally waking (and even misfires are |
895 |
< |
* OK). Note that until the shutdown worker fully terminates, |
896 |
< |
* workerCounts will overestimate total count, which is tolerable. |
897 |
< |
* |
898 |
< |
* @param ec the event count waited on by caller (to abort |
899 |
< |
* attempt if count has since changed). |
974 |
> |
* Decrements blockedCount and increments active count |
975 |
|
*/ |
976 |
< |
private void tryShutdownUnusedWorker(int ec) { |
977 |
< |
if (runState == 0 && eventCount == ec) { // only trigger if all idle |
978 |
< |
ForkJoinWorkerThread[] ws = workers; |
979 |
< |
int n = ws.length; |
980 |
< |
ForkJoinWorkerThread w = null; |
981 |
< |
boolean shutdown = false; |
982 |
< |
int sw; |
908 |
< |
long h; |
909 |
< |
if ((sw = spareWaiters) != 0) { // prefer killing spares |
910 |
< |
int id = (sw & SPARE_ID_MASK) - 1; |
911 |
< |
if (id >= 0 && id < n && (w = ws[id]) != null && |
912 |
< |
UNSAFE.compareAndSwapInt(this, spareWaitersOffset, |
913 |
< |
sw, w.nextSpare)) |
914 |
< |
shutdown = true; |
915 |
< |
} |
916 |
< |
else if ((h = eventWaiters) != 0L) { |
917 |
< |
long nh; |
918 |
< |
int id = ((int)(h & WAITER_ID_MASK)) - 1; |
919 |
< |
if (id >= 0 && id < n && (w = ws[id]) != null && |
920 |
< |
(nh = w.nextWaiter) != 0L && // keep at least one worker |
921 |
< |
UNSAFE.compareAndSwapLong(this, eventWaitersOffset, h, nh)) |
922 |
< |
shutdown = true; |
923 |
< |
} |
924 |
< |
if (w != null && shutdown) { |
925 |
< |
w.shutdown(); |
926 |
< |
LockSupport.unpark(w); |
927 |
< |
} |
928 |
< |
} |
929 |
< |
releaseEventWaiters(); // in case of interference |
976 |
> |
private void postBlock() { |
977 |
> |
long c; |
978 |
> |
do {} while (!UNSAFE.compareAndSwapLong(this, ctlOffset, // no mask |
979 |
> |
c = ctl, c + AC_UNIT)); |
980 |
> |
int b; |
981 |
> |
do {} while(!UNSAFE.compareAndSwapInt(this, blockedCountOffset, |
982 |
> |
b = blockedCount, b - 1)); |
983 |
|
} |
984 |
|
|
985 |
|
/** |
986 |
< |
* Callback from workers invoked upon each top-level action (i.e., |
987 |
< |
* stealing a task or taking a submission and running it). |
935 |
< |
* Performs one or more of the following: |
936 |
< |
* |
937 |
< |
* 1. If the worker is active and either did not run a task |
938 |
< |
* or there are too many workers, try to set its active status |
939 |
< |
* to inactive and update activeCount. On contention, we may |
940 |
< |
* try again in this or a subsequent call. |
941 |
< |
* |
942 |
< |
* 2. If not enough total workers, help create some. |
943 |
< |
* |
944 |
< |
* 3. If there are too many running workers, suspend this worker |
945 |
< |
* (first forcing inactive if necessary). If it is not needed, |
946 |
< |
* it may be shutdown while suspended (via |
947 |
< |
* tryShutdownUnusedWorker). Otherwise, upon resume it |
948 |
< |
* rechecks running thread count and need for event sync. |
949 |
< |
* |
950 |
< |
* 4. If worker did not run a task, await the next task event via |
951 |
< |
* eventSync if necessary (first forcing inactivation), upon |
952 |
< |
* which the worker may be shutdown via |
953 |
< |
* tryShutdownUnusedWorker. Otherwise, help release any |
954 |
< |
* existing event waiters that are now releasable, |
986 |
> |
* Possibly blocks waiting for the given task to complete, or |
987 |
> |
* cancels the task if terminating. Fails to wait if contended. |
988 |
|
* |
989 |
< |
* @param w the worker |
957 |
< |
* @param ran true if worker ran a task since last call to this method |
989 |
> |
* @param joinMe the task |
990 |
|
*/ |
991 |
< |
final void preStep(ForkJoinWorkerThread w, boolean ran) { |
992 |
< |
int wec = w.lastEventCount; |
993 |
< |
boolean active = w.active; |
994 |
< |
boolean inactivate = false; |
995 |
< |
int pc = parallelism; |
996 |
< |
int rs; |
997 |
< |
while (w.runState == 0 && (rs = runState) < TERMINATING) { |
966 |
< |
if ((inactivate || (active && (rs & ACTIVE_COUNT_MASK) >= pc)) && |
967 |
< |
UNSAFE.compareAndSwapInt(this, runStateOffset, rs, rs - 1)) |
968 |
< |
inactivate = active = w.active = false; |
969 |
< |
int wc = workerCounts; |
970 |
< |
if ((wc & RUNNING_COUNT_MASK) > pc) { |
971 |
< |
if (!(inactivate |= active) && // must inactivate to suspend |
972 |
< |
workerCounts == wc && // try to suspend as spare |
973 |
< |
UNSAFE.compareAndSwapInt(this, workerCountsOffset, |
974 |
< |
wc, wc - ONE_RUNNING)) |
975 |
< |
w.suspendAsSpare(); |
976 |
< |
} |
977 |
< |
else if ((wc >>> TOTAL_COUNT_SHIFT) < pc) |
978 |
< |
helpMaintainParallelism(); // not enough workers |
979 |
< |
else if (!ran) { |
980 |
< |
long h = eventWaiters; |
981 |
< |
int ec = eventCount; |
982 |
< |
if (h != 0L && (int)(h >>> EVENT_COUNT_SHIFT) != ec) |
983 |
< |
releaseEventWaiters(); // release others before waiting |
984 |
< |
else if (ec != wec) { |
985 |
< |
w.lastEventCount = ec; // no need to wait |
986 |
< |
break; |
987 |
< |
} |
988 |
< |
else if (!(inactivate |= active)) |
989 |
< |
eventSync(w, wec); // must inactivate before sync |
991 |
> |
final void tryAwaitJoin(ForkJoinTask<?> joinMe) { |
992 |
> |
int s; |
993 |
> |
Thread.interrupted(); // clear interrupts before checking termination |
994 |
> |
if (joinMe.status >= 0) { |
995 |
> |
if (tryPreBlock()) { |
996 |
> |
joinMe.tryAwaitDone(0L); |
997 |
> |
postBlock(); |
998 |
|
} |
999 |
< |
else |
1000 |
< |
break; |
999 |
> |
if ((ctl & STOP_BIT) != 0L) |
1000 |
> |
joinMe.cancelIgnoringExceptions(); |
1001 |
|
} |
1002 |
|
} |
1003 |
|
|
1004 |
|
/** |
1005 |
< |
* Helps and/or blocks awaiting join of the given task. |
1006 |
< |
* See above for explanation. |
1005 |
> |
* Possibly blocks the given worker waiting for joinMe to |
1006 |
> |
* complete or timeout |
1007 |
|
* |
1008 |
< |
* @param joinMe the task to join |
1009 |
< |
* @param worker the current worker thread |
1008 |
> |
* @param joinMe the task |
1009 |
> |
* @param millis the wait time for underlying Object.wait |
1010 |
|
*/ |
1011 |
< |
final void awaitJoin(ForkJoinTask<?> joinMe, ForkJoinWorkerThread worker) { |
1004 |
< |
int retries = 2 + (parallelism >> 2); // #helpJoins before blocking |
1011 |
> |
final void timedAwaitJoin(ForkJoinTask<?> joinMe, long nanos) { |
1012 |
|
while (joinMe.status >= 0) { |
1013 |
< |
int wc; |
1014 |
< |
worker.helpJoinTask(joinMe); |
1015 |
< |
if (joinMe.status < 0) |
1013 |
> |
Thread.interrupted(); |
1014 |
> |
if ((ctl & STOP_BIT) != 0L) { |
1015 |
> |
joinMe.cancelIgnoringExceptions(); |
1016 |
> |
break; |
1017 |
> |
} |
1018 |
> |
if (tryPreBlock()) { |
1019 |
> |
long last = System.nanoTime(); |
1020 |
> |
while (joinMe.status >= 0) { |
1021 |
> |
long millis = TimeUnit.NANOSECONDS.toMillis(nanos); |
1022 |
> |
if (millis <= 0) |
1023 |
> |
break; |
1024 |
> |
joinMe.tryAwaitDone(millis); |
1025 |
> |
if (joinMe.status < 0) |
1026 |
> |
break; |
1027 |
> |
if ((ctl & STOP_BIT) != 0L) { |
1028 |
> |
joinMe.cancelIgnoringExceptions(); |
1029 |
> |
break; |
1030 |
> |
} |
1031 |
> |
long now = System.nanoTime(); |
1032 |
> |
nanos -= now - last; |
1033 |
> |
last = now; |
1034 |
> |
} |
1035 |
> |
postBlock(); |
1036 |
|
break; |
1010 |
– |
else if (retries > 0) |
1011 |
– |
--retries; |
1012 |
– |
else if (((wc = workerCounts) & RUNNING_COUNT_MASK) != 0 && |
1013 |
– |
UNSAFE.compareAndSwapInt(this, workerCountsOffset, |
1014 |
– |
wc, wc - ONE_RUNNING)) { |
1015 |
– |
int stat, c; long h; |
1016 |
– |
while ((stat = joinMe.status) >= 0 && |
1017 |
– |
(h = eventWaiters) != 0L && // help release others |
1018 |
– |
(int)(h >>> EVENT_COUNT_SHIFT) != eventCount) |
1019 |
– |
releaseEventWaiters(); |
1020 |
– |
if (stat >= 0 && |
1021 |
– |
((workerCounts & RUNNING_COUNT_MASK) == 0 || |
1022 |
– |
(stat = |
1023 |
– |
joinMe.internalAwaitDone(JOIN_TIMEOUT_MILLIS)) >= 0)) |
1024 |
– |
helpMaintainParallelism(); // timeout or no running workers |
1025 |
– |
do {} while (!UNSAFE.compareAndSwapInt |
1026 |
– |
(this, workerCountsOffset, |
1027 |
– |
c = workerCounts, c + ONE_RUNNING)); |
1028 |
– |
if (stat < 0) |
1029 |
– |
break; // else restart |
1037 |
|
} |
1038 |
|
} |
1039 |
|
} |
1040 |
|
|
1041 |
|
/** |
1042 |
< |
* Same idea as awaitJoin, but no helping, retries, or timeouts. |
1042 |
> |
* If necessary, compensates for blocker, and blocks |
1043 |
|
*/ |
1044 |
< |
final void awaitBlocker(ManagedBlocker blocker) |
1044 |
> |
private void awaitBlocker(ManagedBlocker blocker) |
1045 |
|
throws InterruptedException { |
1046 |
|
while (!blocker.isReleasable()) { |
1047 |
< |
int wc = workerCounts; |
1041 |
< |
if ((wc & RUNNING_COUNT_MASK) != 0 && |
1042 |
< |
UNSAFE.compareAndSwapInt(this, workerCountsOffset, |
1043 |
< |
wc, wc - ONE_RUNNING)) { |
1047 |
> |
if (tryPreBlock()) { |
1048 |
|
try { |
1049 |
< |
while (!blocker.isReleasable()) { |
1046 |
< |
long h = eventWaiters; |
1047 |
< |
if (h != 0L && |
1048 |
< |
(int)(h >>> EVENT_COUNT_SHIFT) != eventCount) |
1049 |
< |
releaseEventWaiters(); |
1050 |
< |
else if ((workerCounts & RUNNING_COUNT_MASK) == 0 && |
1051 |
< |
runState < TERMINATING) |
1052 |
< |
helpMaintainParallelism(); |
1053 |
< |
else if (blocker.block()) |
1054 |
< |
break; |
1055 |
< |
} |
1049 |
> |
do {} while (!blocker.isReleasable() && !blocker.block()); |
1050 |
|
} finally { |
1051 |
< |
int c; |
1058 |
< |
do {} while (!UNSAFE.compareAndSwapInt |
1059 |
< |
(this, workerCountsOffset, |
1060 |
< |
c = workerCounts, c + ONE_RUNNING)); |
1051 |
> |
postBlock(); |
1052 |
|
} |
1053 |
|
break; |
1054 |
|
} |
1055 |
|
} |
1056 |
|
} |
1057 |
|
|
1058 |
+ |
// Creating, registering and deregistring workers |
1059 |
+ |
|
1060 |
+ |
/** |
1061 |
+ |
* Tries to create and start a worker; minimally rolls back counts |
1062 |
+ |
* on failure. |
1063 |
+ |
*/ |
1064 |
+ |
private void addWorker() { |
1065 |
+ |
Throwable ex = null; |
1066 |
+ |
ForkJoinWorkerThread t = null; |
1067 |
+ |
try { |
1068 |
+ |
t = factory.newThread(this); |
1069 |
+ |
} catch (Throwable e) { |
1070 |
+ |
ex = e; |
1071 |
+ |
} |
1072 |
+ |
if (t == null) { // null or exceptional factory return |
1073 |
+ |
long c; // adjust counts |
1074 |
+ |
do {} while (!UNSAFE.compareAndSwapLong |
1075 |
+ |
(this, ctlOffset, c = ctl, |
1076 |
+ |
(((c - AC_UNIT) & AC_MASK) | |
1077 |
+ |
((c - TC_UNIT) & TC_MASK) | |
1078 |
+ |
(c & ~(AC_MASK|TC_MASK))))); |
1079 |
+ |
// Propagate exception if originating from an external caller |
1080 |
+ |
if (!tryTerminate(false) && ex != null && |
1081 |
+ |
!(Thread.currentThread() instanceof ForkJoinWorkerThread)) |
1082 |
+ |
UNSAFE.throwException(ex); |
1083 |
+ |
} |
1084 |
+ |
else |
1085 |
+ |
t.start(); |
1086 |
+ |
} |
1087 |
+ |
|
1088 |
+ |
/** |
1089 |
+ |
* Callback from ForkJoinWorkerThread constructor to assign a |
1090 |
+ |
* public name |
1091 |
+ |
*/ |
1092 |
+ |
final String nextWorkerName() { |
1093 |
+ |
for (int n;;) { |
1094 |
+ |
if (UNSAFE.compareAndSwapInt(this, nextWorkerNumberOffset, |
1095 |
+ |
n = nextWorkerNumber, ++n)) |
1096 |
+ |
return workerNamePrefix + n; |
1097 |
+ |
} |
1098 |
+ |
} |
1099 |
+ |
|
1100 |
+ |
/** |
1101 |
+ |
* Callback from ForkJoinWorkerThread constructor to |
1102 |
+ |
* determine its poolIndex and record in workers array. |
1103 |
+ |
* |
1104 |
+ |
* @param w the worker |
1105 |
+ |
* @return the worker's pool index |
1106 |
+ |
*/ |
1107 |
+ |
final int registerWorker(ForkJoinWorkerThread w) { |
1108 |
+ |
/* |
1109 |
+ |
* In the typical case, a new worker acquires the lock, uses |
1110 |
+ |
* next available index and returns quickly. Since we should |
1111 |
+ |
* not block callers (ultimately from signalWork or |
1112 |
+ |
* tryPreBlock) waiting for the lock needed to do this, we |
1113 |
+ |
* instead help release other workers while waiting for the |
1114 |
+ |
* lock. |
1115 |
+ |
*/ |
1116 |
+ |
for (int g;;) { |
1117 |
+ |
ForkJoinWorkerThread[] ws; |
1118 |
+ |
if (((g = scanGuard) & SG_UNIT) == 0 && |
1119 |
+ |
UNSAFE.compareAndSwapInt(this, scanGuardOffset, |
1120 |
+ |
g, g | SG_UNIT)) { |
1121 |
+ |
int k = nextWorkerIndex; |
1122 |
+ |
try { |
1123 |
+ |
if ((ws = workers) != null) { // ignore on shutdown |
1124 |
+ |
int n = ws.length; |
1125 |
+ |
if (k < 0 || k >= n || ws[k] != null) { |
1126 |
+ |
for (k = 0; k < n && ws[k] != null; ++k) |
1127 |
+ |
; |
1128 |
+ |
if (k == n) |
1129 |
+ |
ws = workers = Arrays.copyOf(ws, n << 1); |
1130 |
+ |
} |
1131 |
+ |
ws[k] = w; |
1132 |
+ |
nextWorkerIndex = k + 1; |
1133 |
+ |
int m = g & SMASK; |
1134 |
+ |
g = k >= m? ((m << 1) + 1) & SMASK : g + (SG_UNIT<<1); |
1135 |
+ |
} |
1136 |
+ |
} finally { |
1137 |
+ |
scanGuard = g; |
1138 |
+ |
} |
1139 |
+ |
return k; |
1140 |
+ |
} |
1141 |
+ |
else if ((ws = workers) != null) { // help release others |
1142 |
+ |
for (ForkJoinWorkerThread u : ws) { |
1143 |
+ |
if (u != null && u.queueBase != u.queueTop) { |
1144 |
+ |
if (tryReleaseWaiter()) |
1145 |
+ |
break; |
1146 |
+ |
} |
1147 |
+ |
} |
1148 |
+ |
} |
1149 |
+ |
} |
1150 |
+ |
} |
1151 |
+ |
|
1152 |
+ |
/** |
1153 |
+ |
* Final callback from terminating worker. Removes record of |
1154 |
+ |
* worker from array, and adjusts counts. If pool is shutting |
1155 |
+ |
* down, tries to complete termination. |
1156 |
+ |
* |
1157 |
+ |
* @param w the worker |
1158 |
+ |
*/ |
1159 |
+ |
final void deregisterWorker(ForkJoinWorkerThread w, Throwable ex) { |
1160 |
+ |
int idx = w.poolIndex; |
1161 |
+ |
int sc = w.stealCount; |
1162 |
+ |
int steps = 0; |
1163 |
+ |
// Remove from array, adjust worker counts and collect steal count. |
1164 |
+ |
// We can intermix failed removes or adjusts with steal updates |
1165 |
+ |
do { |
1166 |
+ |
long s, c; |
1167 |
+ |
int g; |
1168 |
+ |
if (steps == 0 && ((g = scanGuard) & SG_UNIT) == 0 && |
1169 |
+ |
UNSAFE.compareAndSwapInt(this, scanGuardOffset, |
1170 |
+ |
g, g |= SG_UNIT)) { |
1171 |
+ |
ForkJoinWorkerThread[] ws = workers; |
1172 |
+ |
if (ws != null && idx >= 0 && |
1173 |
+ |
idx < ws.length && ws[idx] == w) |
1174 |
+ |
ws[idx] = null; // verify |
1175 |
+ |
nextWorkerIndex = idx; |
1176 |
+ |
scanGuard = g + SG_UNIT; |
1177 |
+ |
steps = 1; |
1178 |
+ |
} |
1179 |
+ |
if (steps == 1 && |
1180 |
+ |
UNSAFE.compareAndSwapLong(this, ctlOffset, c = ctl, |
1181 |
+ |
(((c - AC_UNIT) & AC_MASK) | |
1182 |
+ |
((c - TC_UNIT) & TC_MASK) | |
1183 |
+ |
(c & ~(AC_MASK|TC_MASK))))) |
1184 |
+ |
steps = 2; |
1185 |
+ |
if (sc != 0 && |
1186 |
+ |
UNSAFE.compareAndSwapLong(this, stealCountOffset, |
1187 |
+ |
s = stealCount, s + sc)) |
1188 |
+ |
sc = 0; |
1189 |
+ |
} while (steps != 2 || sc != 0); |
1190 |
+ |
if (!tryTerminate(false)) { |
1191 |
+ |
if (ex != null) // possibly replace if died abnormally |
1192 |
+ |
signalWork(); |
1193 |
+ |
else |
1194 |
+ |
tryReleaseWaiter(); |
1195 |
+ |
} |
1196 |
+ |
} |
1197 |
+ |
|
1198 |
+ |
// Shutdown and termination |
1199 |
+ |
|
1200 |
|
/** |
1201 |
|
* Possibly initiates and/or completes termination. |
1202 |
|
* |
1205 |
|
* @return true if now terminating or terminated |
1206 |
|
*/ |
1207 |
|
private boolean tryTerminate(boolean now) { |
1208 |
< |
if (now) |
1209 |
< |
advanceRunLevel(SHUTDOWN); // ensure at least SHUTDOWN |
1210 |
< |
else if (runState < SHUTDOWN || |
1211 |
< |
!submissionQueue.isEmpty() || |
1212 |
< |
(runState & ACTIVE_COUNT_MASK) != 0) |
1213 |
< |
return false; |
1214 |
< |
|
1215 |
< |
if (advanceRunLevel(TERMINATING)) |
1216 |
< |
startTerminating(); |
1217 |
< |
|
1218 |
< |
// Finish now if all threads terminated; else in some subsequent call |
1219 |
< |
if ((workerCounts >>> TOTAL_COUNT_SHIFT) == 0) { |
1220 |
< |
advanceRunLevel(TERMINATED); |
1221 |
< |
termination.arrive(); |
1208 |
> |
long c; |
1209 |
> |
while (((c = ctl) & STOP_BIT) == 0) { |
1210 |
> |
if (!now) { |
1211 |
> |
if ((int)(c >> AC_SHIFT) != -parallelism) |
1212 |
> |
return false; |
1213 |
> |
if (!shutdown || blockedCount != 0 || quiescerCount != 0 || |
1214 |
> |
queueTop - queueBase > 0) { |
1215 |
> |
if (ctl == c) // staleness check |
1216 |
> |
return false; |
1217 |
> |
continue; |
1218 |
> |
} |
1219 |
> |
} |
1220 |
> |
if (UNSAFE.compareAndSwapLong(this, ctlOffset, c, c | STOP_BIT)) |
1221 |
> |
startTerminating(); |
1222 |
> |
} |
1223 |
> |
if ((short)(c >>> TC_SHIFT) == -parallelism) { |
1224 |
> |
submissionLock.lock(); |
1225 |
> |
termination.signalAll(); |
1226 |
> |
submissionLock.unlock(); |
1227 |
|
} |
1228 |
|
return true; |
1229 |
|
} |
1230 |
|
|
1231 |
|
/** |
1232 |
< |
* Actions on transition to TERMINATING |
1233 |
< |
* |
1234 |
< |
* Runs up to four passes through workers: (0) shutting down each |
1235 |
< |
* (without waking up if parked) to quickly spread notifications |
1236 |
< |
* without unnecessary bouncing around event queues etc (1) wake |
1237 |
< |
* up and help cancel tasks (2) interrupt (3) mop up races with |
1100 |
< |
* interrupted workers |
1232 |
> |
* Runs up to three passes through workers: (0) Setting |
1233 |
> |
* termination status for each worker, followed by wakeups up |
1234 |
> |
* queued workers (1) helping cancel tasks (2) interrupting |
1235 |
> |
* lagging threads (likely in external tasks, but possibly also |
1236 |
> |
* blocked in joins). Each pass repeats previous steps because of |
1237 |
> |
* potential lagging thread creation. |
1238 |
|
*/ |
1239 |
|
private void startTerminating() { |
1240 |
|
cancelSubmissions(); |
1241 |
< |
for (int passes = 0; passes < 4 && workerCounts != 0; ++passes) { |
1105 |
< |
int c; // advance event count |
1106 |
< |
UNSAFE.compareAndSwapInt(this, eventCountOffset, |
1107 |
< |
c = eventCount, c+1); |
1108 |
< |
eventWaiters = 0L; // clobber lists |
1109 |
< |
spareWaiters = 0; |
1241 |
> |
for (int pass = 0; pass < 3; ++pass) { |
1242 |
|
ForkJoinWorkerThread[] ws = workers; |
1243 |
< |
int n = ws.length; |
1244 |
< |
for (int i = 0; i < n; ++i) { |
1245 |
< |
ForkJoinWorkerThread w = ws[i]; |
1246 |
< |
if (w != null) { |
1247 |
< |
w.shutdown(); |
1248 |
< |
if (passes > 0 && !w.isTerminated()) { |
1249 |
< |
w.cancelTasks(); |
1250 |
< |
LockSupport.unpark(w); |
1251 |
< |
if (passes > 1) { |
1252 |
< |
try { |
1253 |
< |
w.interrupt(); |
1122 |
< |
} catch (SecurityException ignore) { |
1243 |
> |
if (ws != null) { |
1244 |
> |
for (ForkJoinWorkerThread w : ws) { |
1245 |
> |
if (w != null) { |
1246 |
> |
w.terminate = true; |
1247 |
> |
if (pass > 0) { |
1248 |
> |
w.cancelTasks(); |
1249 |
> |
if (pass > 1 && !w.isInterrupted()) { |
1250 |
> |
try { |
1251 |
> |
w.interrupt(); |
1252 |
> |
} catch (SecurityException ignore) { |
1253 |
> |
} |
1254 |
|
} |
1255 |
|
} |
1256 |
|
} |
1257 |
|
} |
1258 |
+ |
terminateWaiters(); |
1259 |
|
} |
1260 |
|
} |
1261 |
|
} |
1262 |
|
|
1263 |
|
/** |
1264 |
< |
* Clear out and cancel submissions, ignoring exceptions |
1264 |
> |
* Polls and cancels all submissions. Called only during termination. |
1265 |
|
*/ |
1266 |
|
private void cancelSubmissions() { |
1267 |
< |
ForkJoinTask<?> task; |
1268 |
< |
while ((task = submissionQueue.poll()) != null) { |
1269 |
< |
try { |
1270 |
< |
task.cancel(false); |
1271 |
< |
} catch (Throwable ignore) { |
1267 |
> |
while (queueBase != queueTop) { |
1268 |
> |
ForkJoinTask<?> task = pollSubmission(); |
1269 |
> |
if (task != null) { |
1270 |
> |
try { |
1271 |
> |
task.cancel(false); |
1272 |
> |
} catch (Throwable ignore) { |
1273 |
> |
} |
1274 |
|
} |
1275 |
|
} |
1276 |
|
} |
1277 |
|
|
1278 |
< |
// misc support for ForkJoinWorkerThread |
1278 |
> |
/** |
1279 |
> |
* Tries to set the termination status of waiting workers, and |
1280 |
> |
* then wake them up (after which they will terminate). |
1281 |
> |
*/ |
1282 |
> |
private void terminateWaiters() { |
1283 |
> |
ForkJoinWorkerThread[] ws = workers; |
1284 |
> |
if (ws != null) { |
1285 |
> |
ForkJoinWorkerThread w; long c; int i, e; |
1286 |
> |
int n = ws.length; |
1287 |
> |
while ((i = ~(e = (int)(c = ctl)) & SMASK) < n && |
1288 |
> |
(w = ws[i]) != null && w.eventCount == (e & E_MASK)) { |
1289 |
> |
if (UNSAFE.compareAndSwapLong(this, ctlOffset, c, |
1290 |
> |
(long)(w.nextWait & E_MASK) | |
1291 |
> |
((c + AC_UNIT) & AC_MASK) | |
1292 |
> |
(c & (TC_MASK|STOP_BIT)))) { |
1293 |
> |
w.terminate = true; |
1294 |
> |
w.eventCount = e + EC_UNIT; |
1295 |
> |
if (w.parked) |
1296 |
> |
UNSAFE.unpark(w); |
1297 |
> |
} |
1298 |
> |
} |
1299 |
> |
} |
1300 |
> |
} |
1301 |
> |
|
1302 |
> |
// misc ForkJoinWorkerThread support |
1303 |
|
|
1304 |
|
/** |
1305 |
< |
* Returns pool number |
1305 |
> |
* Increment or decrement quiescerCount. Needed only to prevent |
1306 |
> |
* triggering shutdown if a worker is transiently inactive while |
1307 |
> |
* checking quiescence. |
1308 |
> |
* |
1309 |
> |
* @param delta 1 for increment, -1 for decrement |
1310 |
|
*/ |
1311 |
< |
final int getPoolNumber() { |
1312 |
< |
return poolNumber; |
1311 |
> |
final void addQuiescerCount(int delta) { |
1312 |
> |
int c; |
1313 |
> |
do {} while(!UNSAFE.compareAndSwapInt(this, quiescerCountOffset, |
1314 |
> |
c = quiescerCount, c + delta)); |
1315 |
|
} |
1316 |
|
|
1317 |
|
/** |
1318 |
< |
* Tries to accumulates steal count from a worker, clearing |
1319 |
< |
* the worker's value. |
1318 |
> |
* Directly increment or decrement active count without |
1319 |
> |
* queuing. This method is used to transiently assert inactivation |
1320 |
> |
* while checking quiescence. |
1321 |
|
* |
1322 |
< |
* @return true if worker steal count now zero |
1322 |
> |
* @param delta 1 for increment, -1 for decrement |
1323 |
|
*/ |
1324 |
< |
final boolean tryAccumulateStealCount(ForkJoinWorkerThread w) { |
1325 |
< |
int sc = w.stealCount; |
1326 |
< |
long c = stealCount; |
1327 |
< |
// CAS even if zero, for fence effects |
1328 |
< |
if (UNSAFE.compareAndSwapLong(this, stealCountOffset, c, c + sc)) { |
1329 |
< |
if (sc != 0) |
1165 |
< |
w.stealCount = 0; |
1166 |
< |
return true; |
1167 |
< |
} |
1168 |
< |
return sc == 0; |
1324 |
> |
final void addActiveCount(int delta) { |
1325 |
> |
long d = delta < 0 ? -AC_UNIT : AC_UNIT; |
1326 |
> |
long c; |
1327 |
> |
do {} while (!UNSAFE.compareAndSwapLong(this, ctlOffset, c = ctl, |
1328 |
> |
((c + d) & AC_MASK) | |
1329 |
> |
(c & ~AC_MASK))); |
1330 |
|
} |
1331 |
|
|
1332 |
|
/** |
1334 |
|
* active thread. |
1335 |
|
*/ |
1336 |
|
final int idlePerActive() { |
1337 |
< |
int pc = parallelism; // use parallelism, not rc |
1338 |
< |
int ac = runState; // no mask -- artificially boosts during shutdown |
1339 |
< |
// Use exact results for small values, saturate past 4 |
1340 |
< |
return pc <= ac? 0 : pc >>> 1 <= ac? 1 : pc >>> 2 <= ac? 3 : pc >>> 3; |
1337 |
> |
// Approximate at powers of two for small values, saturate past 4 |
1338 |
> |
int p = parallelism; |
1339 |
> |
int a = p + (int)(ctl >> AC_SHIFT); |
1340 |
> |
return (a > (p >>>= 1) ? 0 : |
1341 |
> |
a > (p >>>= 1) ? 1 : |
1342 |
> |
a > (p >>>= 1) ? 2 : |
1343 |
> |
a > (p >>>= 1) ? 4 : |
1344 |
> |
8); |
1345 |
|
} |
1346 |
|
|
1347 |
< |
// Public and protected methods |
1347 |
> |
// Exported methods |
1348 |
|
|
1349 |
|
// Constructors |
1350 |
|
|
1391 |
|
* use {@link #defaultForkJoinWorkerThreadFactory}. |
1392 |
|
* @param handler the handler for internal worker threads that |
1393 |
|
* terminate due to unrecoverable errors encountered while executing |
1394 |
< |
* tasks. For default value, use <code>null</code>. |
1394 |
> |
* tasks. For default value, use {@code null}. |
1395 |
|
* @param asyncMode if true, |
1396 |
|
* establishes local first-in-first-out scheduling mode for forked |
1397 |
|
* tasks that are never joined. This mode may be more appropriate |
1398 |
|
* than default locally stack-based mode in applications in which |
1399 |
|
* worker threads only process event-style asynchronous tasks. |
1400 |
< |
* For default value, use <code>false</code>. |
1400 |
> |
* For default value, use {@code false}. |
1401 |
|
* @throws IllegalArgumentException if parallelism less than or |
1402 |
|
* equal to zero, or greater than implementation limit |
1403 |
|
* @throws NullPointerException if the factory is null |
1413 |
|
checkPermission(); |
1414 |
|
if (factory == null) |
1415 |
|
throw new NullPointerException(); |
1416 |
< |
if (parallelism <= 0 || parallelism > MAX_WORKERS) |
1416 |
> |
if (parallelism <= 0 || parallelism > MAX_ID) |
1417 |
|
throw new IllegalArgumentException(); |
1418 |
|
this.parallelism = parallelism; |
1419 |
|
this.factory = factory; |
1420 |
|
this.ueh = handler; |
1421 |
|
this.locallyFifo = asyncMode; |
1422 |
< |
int arraySize = initialArraySizeFor(parallelism); |
1423 |
< |
this.workers = new ForkJoinWorkerThread[arraySize]; |
1424 |
< |
this.submissionQueue = new LinkedTransferQueue<ForkJoinTask<?>>(); |
1425 |
< |
this.workerLock = new ReentrantLock(); |
1426 |
< |
this.termination = new Phaser(1); |
1427 |
< |
this.poolNumber = poolNumberGenerator.incrementAndGet(); |
1428 |
< |
} |
1429 |
< |
|
1430 |
< |
/** |
1431 |
< |
* Returns initial power of two size for workers array. |
1432 |
< |
* @param pc the initial parallelism level |
1433 |
< |
*/ |
1434 |
< |
private static int initialArraySizeFor(int pc) { |
1435 |
< |
// If possible, initially allocate enough space for one spare |
1436 |
< |
int size = pc < MAX_WORKERS ? pc + 1 : MAX_WORKERS; |
1437 |
< |
// See Hackers Delight, sec 3.2. We know MAX_WORKERS < (1 >>> 16) |
1438 |
< |
size |= size >>> 1; |
1274 |
< |
size |= size >>> 2; |
1275 |
< |
size |= size >>> 4; |
1276 |
< |
size |= size >>> 8; |
1277 |
< |
return size + 1; |
1422 |
> |
long np = (long)(-parallelism); // offset ctl counts |
1423 |
> |
this.ctl = ((np << AC_SHIFT) & AC_MASK) | ((np << TC_SHIFT) & TC_MASK); |
1424 |
> |
this.submissionQueue = new ForkJoinTask<?>[INITIAL_QUEUE_CAPACITY]; |
1425 |
> |
// initialize workers array with room for 2*parallelism if possible |
1426 |
> |
int n = parallelism << 1; |
1427 |
> |
if (n >= MAX_ID) |
1428 |
> |
n = MAX_ID; |
1429 |
> |
else { // See Hackers Delight, sec 3.2, where n < (1 << 16) |
1430 |
> |
n |= n >>> 1; n |= n >>> 2; n |= n >>> 4; n |= n >>> 8; |
1431 |
> |
} |
1432 |
> |
workers = new ForkJoinWorkerThread[n + 1]; |
1433 |
> |
this.submissionLock = new ReentrantLock(); |
1434 |
> |
this.termination = submissionLock.newCondition(); |
1435 |
> |
StringBuilder sb = new StringBuilder("ForkJoinPool-"); |
1436 |
> |
sb.append(poolNumberGenerator.incrementAndGet()); |
1437 |
> |
sb.append("-worker-"); |
1438 |
> |
this.workerNamePrefix = sb.toString(); |
1439 |
|
} |
1440 |
|
|
1441 |
|
// Execution methods |
1442 |
|
|
1443 |
|
/** |
1283 |
– |
* Common code for execute, invoke and submit |
1284 |
– |
*/ |
1285 |
– |
private <T> void doSubmit(ForkJoinTask<T> task) { |
1286 |
– |
if (task == null) |
1287 |
– |
throw new NullPointerException(); |
1288 |
– |
if (runState >= SHUTDOWN) |
1289 |
– |
throw new RejectedExecutionException(); |
1290 |
– |
submissionQueue.offer(task); |
1291 |
– |
int c; // try to increment event count -- CAS failure OK |
1292 |
– |
UNSAFE.compareAndSwapInt(this, eventCountOffset, c = eventCount, c+1); |
1293 |
– |
helpMaintainParallelism(); // create, start, or resume some workers |
1294 |
– |
} |
1295 |
– |
|
1296 |
– |
/** |
1444 |
|
* Performs the given task, returning its result upon completion. |
1445 |
+ |
* If the computation encounters an unchecked Exception or Error, |
1446 |
+ |
* it is rethrown as the outcome of this invocation. Rethrown |
1447 |
+ |
* exceptions behave in the same way as regular exceptions, but, |
1448 |
+ |
* when possible, contain stack traces (as displayed for example |
1449 |
+ |
* using {@code ex.printStackTrace()}) of both the current thread |
1450 |
+ |
* as well as the thread actually encountering the exception; |
1451 |
+ |
* minimally only the latter. |
1452 |
|
* |
1453 |
|
* @param task the task |
1454 |
|
* @return the task's result |
1457 |
|
* scheduled for execution |
1458 |
|
*/ |
1459 |
|
public <T> T invoke(ForkJoinTask<T> task) { |
1460 |
< |
doSubmit(task); |
1461 |
< |
return task.join(); |
1460 |
> |
Thread t = Thread.currentThread(); |
1461 |
> |
if (task == null) |
1462 |
> |
throw new NullPointerException(); |
1463 |
> |
if (shutdown) |
1464 |
> |
throw new RejectedExecutionException(); |
1465 |
> |
if ((t instanceof ForkJoinWorkerThread) && |
1466 |
> |
((ForkJoinWorkerThread)t).pool == this) |
1467 |
> |
return task.invoke(); // bypass submit if in same pool |
1468 |
> |
else { |
1469 |
> |
addSubmission(task); |
1470 |
> |
return task.join(); |
1471 |
> |
} |
1472 |
> |
} |
1473 |
> |
|
1474 |
> |
/** |
1475 |
> |
* Unless terminating, forks task if within an ongoing FJ |
1476 |
> |
* computation in the current pool, else submits as external task. |
1477 |
> |
*/ |
1478 |
> |
private <T> void forkOrSubmit(ForkJoinTask<T> task) { |
1479 |
> |
ForkJoinWorkerThread w; |
1480 |
> |
Thread t = Thread.currentThread(); |
1481 |
> |
if (shutdown) |
1482 |
> |
throw new RejectedExecutionException(); |
1483 |
> |
if ((t instanceof ForkJoinWorkerThread) && |
1484 |
> |
(w = (ForkJoinWorkerThread)t).pool == this) |
1485 |
> |
w.pushTask(task); |
1486 |
> |
else |
1487 |
> |
addSubmission(task); |
1488 |
|
} |
1489 |
|
|
1490 |
|
/** |
1496 |
|
* scheduled for execution |
1497 |
|
*/ |
1498 |
|
public void execute(ForkJoinTask<?> task) { |
1499 |
< |
doSubmit(task); |
1499 |
> |
if (task == null) |
1500 |
> |
throw new NullPointerException(); |
1501 |
> |
forkOrSubmit(task); |
1502 |
|
} |
1503 |
|
|
1504 |
|
// AbstractExecutorService methods |
1509 |
|
* scheduled for execution |
1510 |
|
*/ |
1511 |
|
public void execute(Runnable task) { |
1512 |
+ |
if (task == null) |
1513 |
+ |
throw new NullPointerException(); |
1514 |
|
ForkJoinTask<?> job; |
1515 |
|
if (task instanceof ForkJoinTask<?>) // avoid re-wrap |
1516 |
|
job = (ForkJoinTask<?>) task; |
1517 |
|
else |
1518 |
|
job = ForkJoinTask.adapt(task, null); |
1519 |
< |
doSubmit(job); |
1519 |
> |
forkOrSubmit(job); |
1520 |
|
} |
1521 |
|
|
1522 |
|
/** |
1529 |
|
* scheduled for execution |
1530 |
|
*/ |
1531 |
|
public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) { |
1532 |
< |
doSubmit(task); |
1532 |
> |
if (task == null) |
1533 |
> |
throw new NullPointerException(); |
1534 |
> |
forkOrSubmit(task); |
1535 |
|
return task; |
1536 |
|
} |
1537 |
|
|
1541 |
|
* scheduled for execution |
1542 |
|
*/ |
1543 |
|
public <T> ForkJoinTask<T> submit(Callable<T> task) { |
1544 |
+ |
if (task == null) |
1545 |
+ |
throw new NullPointerException(); |
1546 |
|
ForkJoinTask<T> job = ForkJoinTask.adapt(task); |
1547 |
< |
doSubmit(job); |
1547 |
> |
forkOrSubmit(job); |
1548 |
|
return job; |
1549 |
|
} |
1550 |
|
|
1554 |
|
* scheduled for execution |
1555 |
|
*/ |
1556 |
|
public <T> ForkJoinTask<T> submit(Runnable task, T result) { |
1557 |
+ |
if (task == null) |
1558 |
+ |
throw new NullPointerException(); |
1559 |
|
ForkJoinTask<T> job = ForkJoinTask.adapt(task, result); |
1560 |
< |
doSubmit(job); |
1560 |
> |
forkOrSubmit(job); |
1561 |
|
return job; |
1562 |
|
} |
1563 |
|
|
1567 |
|
* scheduled for execution |
1568 |
|
*/ |
1569 |
|
public ForkJoinTask<?> submit(Runnable task) { |
1570 |
+ |
if (task == null) |
1571 |
+ |
throw new NullPointerException(); |
1572 |
|
ForkJoinTask<?> job; |
1573 |
|
if (task instanceof ForkJoinTask<?>) // avoid re-wrap |
1574 |
|
job = (ForkJoinTask<?>) task; |
1575 |
|
else |
1576 |
|
job = ForkJoinTask.adapt(task, null); |
1577 |
< |
doSubmit(job); |
1577 |
> |
forkOrSubmit(job); |
1578 |
|
return job; |
1579 |
|
} |
1580 |
|
|
1634 |
|
|
1635 |
|
/** |
1636 |
|
* Returns the number of worker threads that have started but not |
1637 |
< |
* yet terminated. This result returned by this method may differ |
1637 |
> |
* yet terminated. The result returned by this method may differ |
1638 |
|
* from {@link #getParallelism} when threads are created to |
1639 |
|
* maintain parallelism when others are cooperatively blocked. |
1640 |
|
* |
1641 |
|
* @return the number of worker threads |
1642 |
|
*/ |
1643 |
|
public int getPoolSize() { |
1644 |
< |
return workerCounts >>> TOTAL_COUNT_SHIFT; |
1644 |
> |
return parallelism + (short)(ctl >>> TC_SHIFT); |
1645 |
|
} |
1646 |
|
|
1647 |
|
/** |
1663 |
|
* @return the number of worker threads |
1664 |
|
*/ |
1665 |
|
public int getRunningThreadCount() { |
1666 |
< |
return workerCounts & RUNNING_COUNT_MASK; |
1666 |
> |
int r = parallelism + (int)(ctl >> AC_SHIFT); |
1667 |
> |
return r <= 0? 0 : r; // suppress momentarily negative values |
1668 |
|
} |
1669 |
|
|
1670 |
|
/** |
1675 |
|
* @return the number of active threads |
1676 |
|
*/ |
1677 |
|
public int getActiveThreadCount() { |
1678 |
< |
return runState & ACTIVE_COUNT_MASK; |
1678 |
> |
int r = parallelism + (int)(ctl >> AC_SHIFT) + blockedCount; |
1679 |
> |
return r <= 0? 0 : r; // suppress momentarily negative values |
1680 |
|
} |
1681 |
|
|
1682 |
|
/** |
1691 |
|
* @return {@code true} if all threads are currently idle |
1692 |
|
*/ |
1693 |
|
public boolean isQuiescent() { |
1694 |
< |
return (runState & ACTIVE_COUNT_MASK) == 0; |
1694 |
> |
return parallelism + (int)(ctl >> AC_SHIFT) + blockedCount == 0; |
1695 |
|
} |
1696 |
|
|
1697 |
|
/** |
1721 |
|
*/ |
1722 |
|
public long getQueuedTaskCount() { |
1723 |
|
long count = 0; |
1724 |
< |
ForkJoinWorkerThread[] ws = workers; |
1725 |
< |
int n = ws.length; |
1726 |
< |
for (int i = 0; i < n; ++i) { |
1727 |
< |
ForkJoinWorkerThread w = ws[i]; |
1728 |
< |
if (w != null) |
1729 |
< |
count += w.getQueueSize(); |
1724 |
> |
ForkJoinWorkerThread[] ws; |
1725 |
> |
if ((short)(ctl >>> TC_SHIFT) > -parallelism && |
1726 |
> |
(ws = workers) != null) { |
1727 |
> |
for (ForkJoinWorkerThread w : ws) |
1728 |
> |
if (w != null) |
1729 |
> |
count -= w.queueBase - w.queueTop; // must read base first |
1730 |
|
} |
1731 |
|
return count; |
1732 |
|
} |
1733 |
|
|
1734 |
|
/** |
1735 |
|
* Returns an estimate of the number of tasks submitted to this |
1736 |
< |
* pool that have not yet begun executing. This method takes time |
1737 |
< |
* proportional to the number of submissions. |
1736 |
> |
* pool that have not yet begun executing. This method may take |
1737 |
> |
* time proportional to the number of submissions. |
1738 |
|
* |
1739 |
|
* @return the number of queued submissions |
1740 |
|
*/ |
1741 |
|
public int getQueuedSubmissionCount() { |
1742 |
< |
return submissionQueue.size(); |
1742 |
> |
return -queueBase + queueTop; |
1743 |
|
} |
1744 |
|
|
1745 |
|
/** |
1749 |
|
* @return {@code true} if there are any queued submissions |
1750 |
|
*/ |
1751 |
|
public boolean hasQueuedSubmissions() { |
1752 |
< |
return !submissionQueue.isEmpty(); |
1752 |
> |
return queueBase != queueTop; |
1753 |
|
} |
1754 |
|
|
1755 |
|
/** |
1760 |
|
* @return the next submission, or {@code null} if none |
1761 |
|
*/ |
1762 |
|
protected ForkJoinTask<?> pollSubmission() { |
1763 |
< |
return submissionQueue.poll(); |
1763 |
> |
ForkJoinTask<?> t; ForkJoinTask<?>[] q; int b, i; |
1764 |
> |
while ((b = queueBase) != queueTop && |
1765 |
> |
(q = submissionQueue) != null && |
1766 |
> |
(i = (q.length - 1) & b) >= 0) { |
1767 |
> |
long u = (i << ASHIFT) + ABASE; |
1768 |
> |
if ((t = q[i]) != null && |
1769 |
> |
queueBase == b && |
1770 |
> |
UNSAFE.compareAndSwapObject(q, u, t, null)) { |
1771 |
> |
queueBase = b + 1; |
1772 |
> |
return t; |
1773 |
> |
} |
1774 |
> |
} |
1775 |
> |
return null; |
1776 |
|
} |
1777 |
|
|
1778 |
|
/** |
1793 |
|
* @return the number of elements transferred |
1794 |
|
*/ |
1795 |
|
protected int drainTasksTo(Collection<? super ForkJoinTask<?>> c) { |
1796 |
< |
int count = submissionQueue.drainTo(c); |
1797 |
< |
ForkJoinWorkerThread[] ws = workers; |
1798 |
< |
int n = ws.length; |
1799 |
< |
for (int i = 0; i < n; ++i) { |
1800 |
< |
ForkJoinWorkerThread w = ws[i]; |
1801 |
< |
if (w != null) |
1802 |
< |
count += w.drainTasksTo(c); |
1796 |
> |
int count = 0; |
1797 |
> |
while (queueBase != queueTop) { |
1798 |
> |
ForkJoinTask<?> t = pollSubmission(); |
1799 |
> |
if (t != null) { |
1800 |
> |
c.add(t); |
1801 |
> |
++count; |
1802 |
> |
} |
1803 |
> |
} |
1804 |
> |
ForkJoinWorkerThread[] ws; |
1805 |
> |
if ((short)(ctl >>> TC_SHIFT) > -parallelism && |
1806 |
> |
(ws = workers) != null) { |
1807 |
> |
for (ForkJoinWorkerThread w : ws) |
1808 |
> |
if (w != null) |
1809 |
> |
count += w.drainTasksTo(c); |
1810 |
|
} |
1811 |
|
return count; |
1812 |
|
} |
1822 |
|
long st = getStealCount(); |
1823 |
|
long qt = getQueuedTaskCount(); |
1824 |
|
long qs = getQueuedSubmissionCount(); |
1612 |
– |
int wc = workerCounts; |
1613 |
– |
int tc = wc >>> TOTAL_COUNT_SHIFT; |
1614 |
– |
int rc = wc & RUNNING_COUNT_MASK; |
1825 |
|
int pc = parallelism; |
1826 |
< |
int rs = runState; |
1827 |
< |
int ac = rs & ACTIVE_COUNT_MASK; |
1826 |
> |
long c = ctl; |
1827 |
> |
int tc = pc + (short)(c >>> TC_SHIFT); |
1828 |
> |
int rc = pc + (int)(c >> AC_SHIFT); |
1829 |
> |
if (rc < 0) // ignore transient negative |
1830 |
> |
rc = 0; |
1831 |
> |
int ac = rc + blockedCount; |
1832 |
> |
String level; |
1833 |
> |
if ((c & STOP_BIT) != 0) |
1834 |
> |
level = (tc == 0)? "Terminated" : "Terminating"; |
1835 |
> |
else |
1836 |
> |
level = shutdown? "Shutting down" : "Running"; |
1837 |
|
return super.toString() + |
1838 |
< |
"[" + runLevelToString(rs) + |
1838 |
> |
"[" + level + |
1839 |
|
", parallelism = " + pc + |
1840 |
|
", size = " + tc + |
1841 |
|
", active = " + ac + |
1846 |
|
"]"; |
1847 |
|
} |
1848 |
|
|
1630 |
– |
private static String runLevelToString(int s) { |
1631 |
– |
return ((s & TERMINATED) != 0 ? "Terminated" : |
1632 |
– |
((s & TERMINATING) != 0 ? "Terminating" : |
1633 |
– |
((s & SHUTDOWN) != 0 ? "Shutting down" : |
1634 |
– |
"Running"))); |
1635 |
– |
} |
1636 |
– |
|
1849 |
|
/** |
1850 |
|
* Initiates an orderly shutdown in which previously submitted |
1851 |
|
* tasks are executed, but no new tasks will be accepted. |
1860 |
|
*/ |
1861 |
|
public void shutdown() { |
1862 |
|
checkPermission(); |
1863 |
< |
advanceRunLevel(SHUTDOWN); |
1863 |
> |
shutdown = true; |
1864 |
|
tryTerminate(false); |
1865 |
|
} |
1866 |
|
|
1882 |
|
*/ |
1883 |
|
public List<Runnable> shutdownNow() { |
1884 |
|
checkPermission(); |
1885 |
+ |
shutdown = true; |
1886 |
|
tryTerminate(true); |
1887 |
|
return Collections.emptyList(); |
1888 |
|
} |
1893 |
|
* @return {@code true} if all tasks have completed following shut down |
1894 |
|
*/ |
1895 |
|
public boolean isTerminated() { |
1896 |
< |
return runState >= TERMINATED; |
1896 |
> |
long c = ctl; |
1897 |
> |
return ((c & STOP_BIT) != 0L && |
1898 |
> |
(short)(c >>> TC_SHIFT) == -parallelism); |
1899 |
|
} |
1900 |
|
|
1901 |
|
/** |
1903 |
|
* commenced but not yet completed. This method may be useful for |
1904 |
|
* debugging. A return of {@code true} reported a sufficient |
1905 |
|
* period after shutdown may indicate that submitted tasks have |
1906 |
< |
* ignored or suppressed interruption, causing this executor not |
1907 |
< |
* to properly terminate. |
1906 |
> |
* ignored or suppressed interruption, or are waiting for IO, |
1907 |
> |
* causing this executor not to properly terminate. (See the |
1908 |
> |
* advisory notes for class {@link ForkJoinTask} stating that |
1909 |
> |
* tasks should not normally entail blocking operations. But if |
1910 |
> |
* they do, they must abort them on interrupt.) |
1911 |
|
* |
1912 |
|
* @return {@code true} if terminating but not yet terminated |
1913 |
|
*/ |
1914 |
|
public boolean isTerminating() { |
1915 |
< |
return (runState & (TERMINATING|TERMINATED)) == TERMINATING; |
1915 |
> |
long c = ctl; |
1916 |
> |
return ((c & STOP_BIT) != 0L && |
1917 |
> |
(short)(c >>> TC_SHIFT) != -parallelism); |
1918 |
> |
} |
1919 |
> |
|
1920 |
> |
/** |
1921 |
> |
* Returns true if terminating or terminated. Used by ForkJoinWorkerThread. |
1922 |
> |
*/ |
1923 |
> |
final boolean isAtLeastTerminating() { |
1924 |
> |
return (ctl & STOP_BIT) != 0L; |
1925 |
|
} |
1926 |
|
|
1927 |
|
/** |
1930 |
|
* @return {@code true} if this pool has been shut down |
1931 |
|
*/ |
1932 |
|
public boolean isShutdown() { |
1933 |
< |
return runState >= SHUTDOWN; |
1933 |
> |
return shutdown; |
1934 |
|
} |
1935 |
|
|
1936 |
|
/** |
1946 |
|
*/ |
1947 |
|
public boolean awaitTermination(long timeout, TimeUnit unit) |
1948 |
|
throws InterruptedException { |
1949 |
+ |
long nanos = unit.toNanos(timeout); |
1950 |
+ |
final ReentrantLock lock = this.submissionLock; |
1951 |
+ |
lock.lock(); |
1952 |
|
try { |
1953 |
< |
return termination.awaitAdvanceInterruptibly(0, timeout, unit) > 0; |
1954 |
< |
} catch(TimeoutException ex) { |
1955 |
< |
return false; |
1953 |
> |
for (;;) { |
1954 |
> |
if (isTerminated()) |
1955 |
> |
return true; |
1956 |
> |
if (nanos <= 0) |
1957 |
> |
return false; |
1958 |
> |
nanos = termination.awaitNanos(nanos); |
1959 |
> |
} |
1960 |
> |
} finally { |
1961 |
> |
lock.unlock(); |
1962 |
|
} |
1963 |
|
} |
1964 |
|
|
1970 |
|
* {@code isReleasable} must return {@code true} if blocking is |
1971 |
|
* not necessary. Method {@code block} blocks the current thread |
1972 |
|
* if necessary (perhaps internally invoking {@code isReleasable} |
1973 |
< |
* before actually blocking). The unusual methods in this API |
1974 |
< |
* accommodate synchronizers that may, but don't usually, block |
1975 |
< |
* for long periods. Similarly, they allow more efficient internal |
1976 |
< |
* handling of cases in which additional workers may be, but |
1977 |
< |
* usually are not, needed to ensure sufficient parallelism. |
1978 |
< |
* Toward this end, implementations of method {@code isReleasable} |
1979 |
< |
* must be amenable to repeated invocation. |
1973 |
> |
* before actually blocking). These actions are performed by any |
1974 |
> |
* thread invoking {@link ForkJoinPool#managedBlock}. The |
1975 |
> |
* unusual methods in this API accommodate synchronizers that may, |
1976 |
> |
* but don't usually, block for long periods. Similarly, they |
1977 |
> |
* allow more efficient internal handling of cases in which |
1978 |
> |
* additional workers may be, but usually are not, needed to |
1979 |
> |
* ensure sufficient parallelism. Toward this end, |
1980 |
> |
* implementations of method {@code isReleasable} must be amenable |
1981 |
> |
* to repeated invocation. |
1982 |
|
* |
1983 |
|
* <p>For example, here is a ManagedBlocker based on a |
1984 |
|
* ReentrantLock: |
2080 |
|
} |
2081 |
|
|
2082 |
|
// Unsafe mechanics |
2083 |
< |
|
2084 |
< |
private static final sun.misc.Unsafe UNSAFE = getUnsafe(); |
2085 |
< |
private static final long workerCountsOffset = |
2086 |
< |
objectFieldOffset("workerCounts", ForkJoinPool.class); |
2087 |
< |
private static final long runStateOffset = |
2088 |
< |
objectFieldOffset("runState", ForkJoinPool.class); |
2089 |
< |
private static final long eventCountOffset = |
2090 |
< |
objectFieldOffset("eventCount", ForkJoinPool.class); |
2091 |
< |
private static final long eventWaitersOffset = |
2092 |
< |
objectFieldOffset("eventWaiters",ForkJoinPool.class); |
2093 |
< |
private static final long stealCountOffset = |
2094 |
< |
objectFieldOffset("stealCount",ForkJoinPool.class); |
2095 |
< |
private static final long spareWaitersOffset = |
2096 |
< |
objectFieldOffset("spareWaiters",ForkJoinPool.class); |
2097 |
< |
|
2098 |
< |
private static long objectFieldOffset(String field, Class<?> klazz) { |
2083 |
> |
private static final sun.misc.Unsafe UNSAFE; |
2084 |
> |
private static final long ctlOffset; |
2085 |
> |
private static final long stealCountOffset; |
2086 |
> |
private static final long blockedCountOffset; |
2087 |
> |
private static final long quiescerCountOffset; |
2088 |
> |
private static final long scanGuardOffset; |
2089 |
> |
private static final long nextWorkerNumberOffset; |
2090 |
> |
private static final long ABASE; |
2091 |
> |
private static final int ASHIFT; |
2092 |
> |
|
2093 |
> |
static { |
2094 |
> |
poolNumberGenerator = new AtomicInteger(); |
2095 |
> |
workerSeedGenerator = new Random(); |
2096 |
> |
modifyThreadPermission = new RuntimePermission("modifyThread"); |
2097 |
> |
defaultForkJoinWorkerThreadFactory = |
2098 |
> |
new DefaultForkJoinWorkerThreadFactory(); |
2099 |
> |
int s; |
2100 |
|
try { |
2101 |
< |
return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field)); |
2102 |
< |
} catch (NoSuchFieldException e) { |
2103 |
< |
// Convert Exception to corresponding Error |
2104 |
< |
NoSuchFieldError error = new NoSuchFieldError(field); |
2105 |
< |
error.initCause(e); |
2106 |
< |
throw error; |
2107 |
< |
} |
2101 |
> |
UNSAFE = getUnsafe(); |
2102 |
> |
Class k = ForkJoinPool.class; |
2103 |
> |
ctlOffset = UNSAFE.objectFieldOffset |
2104 |
> |
(k.getDeclaredField("ctl")); |
2105 |
> |
stealCountOffset = UNSAFE.objectFieldOffset |
2106 |
> |
(k.getDeclaredField("stealCount")); |
2107 |
> |
blockedCountOffset = UNSAFE.objectFieldOffset |
2108 |
> |
(k.getDeclaredField("blockedCount")); |
2109 |
> |
quiescerCountOffset = UNSAFE.objectFieldOffset |
2110 |
> |
(k.getDeclaredField("quiescerCount")); |
2111 |
> |
scanGuardOffset = UNSAFE.objectFieldOffset |
2112 |
> |
(k.getDeclaredField("scanGuard")); |
2113 |
> |
nextWorkerNumberOffset = UNSAFE.objectFieldOffset |
2114 |
> |
(k.getDeclaredField("nextWorkerNumber")); |
2115 |
> |
Class a = ForkJoinTask[].class; |
2116 |
> |
ABASE = UNSAFE.arrayBaseOffset(a); |
2117 |
> |
s = UNSAFE.arrayIndexScale(a); |
2118 |
> |
} catch (Exception e) { |
2119 |
> |
throw new Error(e); |
2120 |
> |
} |
2121 |
> |
if ((s & (s-1)) != 0) |
2122 |
> |
throw new Error("data type scale not a power of two"); |
2123 |
> |
ASHIFT = 31 - Integer.numberOfLeadingZeros(s); |
2124 |
|
} |
2125 |
|
|
2126 |
|
/** |