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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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* <td ALIGN=CENTER> <b>Call from within fork/join computations</b></td> |
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* </tr> |
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* <tr> |
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* <td> <b>Arange async execution</td> |
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* <td> <b>Arrange async execution</td> |
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* <td> {@link #execute(ForkJoinTask)}</td> |
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* <td> {@link ForkJoinTask#fork}</td> |
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* </tr> |
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* Beyond work-stealing support and essential bookkeeping, the |
140 |
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* main responsibility of this framework is to take actions when |
141 |
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* one worker is waiting to join a task stolen (or always held by) |
142 |
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* another. Becauae we are multiplexing many tasks on to a pool |
142 |
> |
* another. Because we are multiplexing many tasks on to a pool |
143 |
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* of workers, we can't just let them block (as in Thread.join). |
144 |
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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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* links to try to find such a task. |
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* |
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* Compensating: Unless there are already enough live threads, |
159 |
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* method helpMaintainParallelism() may create or or |
159 |
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* method helpMaintainParallelism() may create or |
160 |
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* re-activate a spare thread to compensate for blocked |
161 |
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* joiners until they unblock. |
162 |
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* |
163 |
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* Because the determining existence of conservatively safe |
164 |
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* helping targets, the availability of already-created spares, |
165 |
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* and the apparent need to create new spares are all racy and |
166 |
< |
* require heuristic guidance, we rely on multiple retries of |
167 |
< |
* each. Further, because it is impossible to keep exactly the |
168 |
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* target (parallelism) number of threads running at any given |
169 |
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* time, we allow compensation during joins to fail, and enlist |
170 |
< |
* all other threads to help out whenever they are not otherwise |
171 |
< |
* occupied (i.e., mainly in method preStep). |
163 |
> |
* It is impossible to keep exactly the target (parallelism) |
164 |
> |
* number of threads running at any given time. Determining |
165 |
> |
* existence of conservatively safe helping targets, the |
166 |
> |
* availability of already-created spares, and the apparent need |
167 |
> |
* to create new spares are all racy and require heuristic |
168 |
> |
* guidance, so we rely on multiple retries of each. Compensation |
169 |
> |
* occurs in slow-motion. It is triggered only upon timeouts of |
170 |
> |
* Object.wait used for joins. This reduces poor decisions that |
171 |
> |
* would otherwise be made when threads are waiting for others |
172 |
> |
* that are stalled because of unrelated activities such as |
173 |
> |
* garbage collection. |
174 |
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* |
175 |
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* The ManagedBlocker extension API can't use helping so relies |
176 |
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* only on compensation in method awaitBlocker. |
225 |
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* ManagedBlocker), we may create or resume others to take their |
226 |
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* place until they unblock (see below). Implementing this |
227 |
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* requires counts of the number of "running" threads (i.e., those |
228 |
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* that are neither blocked nor artifically suspended) as well as |
228 |
> |
* that are neither blocked nor artificially suspended) as well as |
229 |
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* the total number. These two values are packed into one field, |
230 |
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* "workerCounts" because we need accurate snapshots when deciding |
231 |
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* to create, resume or suspend. Note however that the |
232 |
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* correspondance of these counts to reality is not guaranteed. In |
232 |
> |
* correspondence of these counts to reality is not guaranteed. In |
233 |
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* particular updates for unblocked threads may lag until they |
234 |
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* actually wake up. |
235 |
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* |
272 |
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* In addition to allowing simpler decisions about need for |
273 |
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* wakeup, the event count bits in eventWaiters serve the role of |
274 |
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* tags to avoid ABA errors in Treiber stacks. Upon any wakeup, |
275 |
< |
* released threads also try to release others (but give up upon |
276 |
< |
* contention to reduce useless flailing). The net effect is a |
277 |
< |
* tree-like diffusion of signals, where released threads (and |
278 |
< |
* possibly others) help with unparks. To further reduce |
279 |
< |
* contention effects a bit, failed CASes to increment field |
279 |
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* eventCount are tolerated without retries in signalWork. |
275 |
> |
* released threads also try to release at most two others. The |
276 |
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* net effect is a tree-like diffusion of signals, where released |
277 |
> |
* threads (and possibly others) help with unparks. To further |
278 |
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* reduce contention effects a bit, failed CASes to increment |
279 |
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* field eventCount are tolerated without retries in signalWork. |
280 |
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* Conceptually they are merged into the same event, which is OK |
281 |
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* when their only purpose is to enable workers to scan for work. |
282 |
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* |
283 |
< |
* 5. Managing suspension of extra workers. When a worker is about |
284 |
< |
* to block waiting for a join (or via ManagedBlockers), we may |
285 |
< |
* create a new thread to maintain parallelism level, or at least |
286 |
< |
* avoid starvation. Usually, extra threads are needed for only |
287 |
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* very short periods, yet join dependencies are such that we |
288 |
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* sometimes need them in bursts. Rather than create new threads |
289 |
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* each time this happens, we suspend no-longer-needed extra ones |
290 |
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* as "spares". For most purposes, we don't distinguish "extra" |
291 |
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* spare threads from normal "core" threads: On each call to |
292 |
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* preStep (the only point at which we can do this) a worker |
293 |
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* checks to see if there are now too many running workers, and if |
294 |
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* so, suspends itself. Method helpMaintainParallelism looks for |
295 |
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* suspended threads to resume before considering creating a new |
296 |
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* replacement. The spares themselves are encoded on another |
297 |
< |
* variant of a Treiber Stack, headed at field "spareWaiters". |
298 |
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* Note that the use of spares is intrinsically racy. One thread |
299 |
< |
* may become a spare at about the same time as another is |
300 |
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* needlessly being created. We counteract this and related slop |
301 |
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* in part by requiring resumed spares to immediately recheck (in |
302 |
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* preStep) to see whether they they should re-suspend. |
303 |
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* |
304 |
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* 6. Killing off unneeded workers. The Spare and Event queues use |
305 |
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* similar mechanisms to shed unused workers: The oldest (first) |
306 |
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* waiter uses a timed rather than hard wait. When this wait times |
307 |
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* out without a normal wakeup, it tries to shutdown any one (for |
308 |
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* convenience the newest) other waiter via tryShutdownSpare or |
309 |
< |
* tryShutdownWaiter, respectively. The wakeup rates for spares |
310 |
< |
* are much shorter than for waiters. Together, they will |
311 |
< |
* eventually reduce the number of worker threads to a minimum of |
312 |
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* one after a long enough period without use. |
283 |
> |
* 5. Managing suspension of extra workers. When a worker notices |
284 |
> |
* (usually upon timeout of a wait()) that there are too few |
285 |
> |
* running threads, we may create a new thread to maintain |
286 |
> |
* parallelism level, or at least avoid starvation. Usually, extra |
287 |
> |
* threads are needed for only very short periods, yet join |
288 |
> |
* dependencies are such that we sometimes need them in |
289 |
> |
* bursts. Rather than create new threads each time this happens, |
290 |
> |
* we suspend no-longer-needed extra ones as "spares". For most |
291 |
> |
* purposes, we don't distinguish "extra" spare threads from |
292 |
> |
* normal "core" threads: On each call to preStep (the only point |
293 |
> |
* at which we can do this) a worker checks to see if there are |
294 |
> |
* now too many running workers, and if so, suspends itself. |
295 |
> |
* Method helpMaintainParallelism looks for suspended threads to |
296 |
> |
* resume before considering creating a new replacement. The |
297 |
> |
* spares themselves are encoded on another variant of a Treiber |
298 |
> |
* Stack, headed at field "spareWaiters". Note that the use of |
299 |
> |
* spares is intrinsically racy. One thread may become a spare at |
300 |
> |
* about the same time as another is needlessly being created. We |
301 |
> |
* counteract this and related slop in part by requiring resumed |
302 |
> |
* spares to immediately recheck (in preStep) to see whether they |
303 |
> |
* should re-suspend. |
304 |
> |
* |
305 |
> |
* 6. Killing off unneeded workers. A timeout mechanism is used to |
306 |
> |
* shed unused workers: The oldest (first) event queue waiter uses |
307 |
> |
* a timed rather than hard wait. When this wait times out without |
308 |
> |
* a normal wakeup, it tries to shutdown any one (for convenience |
309 |
> |
* the newest) other spare or event waiter via |
310 |
> |
* tryShutdownUnusedWorker. This eventually reduces the number of |
311 |
> |
* worker threads to a minimum of one after a long enough period |
312 |
> |
* without use. |
313 |
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* |
314 |
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* 7. Deciding when to create new workers. The main dynamic |
315 |
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* control in this class is deciding when to create extra threads |
316 |
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* in method helpMaintainParallelism. We would like to keep |
317 |
< |
* exactly #parallelism threads running, which is an impossble |
317 |
> |
* exactly #parallelism threads running, which is an impossible |
318 |
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* task. We always need to create one when the number of running |
319 |
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* threads would become zero and all workers are busy. Beyond |
320 |
< |
* this, we must rely on heuristics that work well in the the |
321 |
< |
* presence of transients phenomena such as GC stalls, dynamic |
320 |
> |
* this, we must rely on heuristics that work well in the |
321 |
> |
* presence of transient phenomena such as GC stalls, dynamic |
322 |
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* compilation, and wake-up lags. These transients are extremely |
323 |
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* common -- we are normally trying to fully saturate the CPUs on |
324 |
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* a machine, so almost any activity other than running tasks |
325 |
< |
* impedes accuracy. Our main defense is to allow some slack in |
326 |
< |
* creation thresholds, using rules that reflect the fact that the |
327 |
< |
* more threads we have running, the more likely that we are |
328 |
< |
* underestimating the number running threads. (We also include |
329 |
< |
* some heuristic use of Thread.yield when all workers appear to |
330 |
< |
* be busy, to improve likelihood of counts settling.) The rules |
331 |
< |
* also better cope with the fact that some of the methods in this |
332 |
< |
* class tend to never become compiled (but are interpreted), so |
333 |
< |
* some components of the entire set of controls might execute 100 |
334 |
< |
* times faster than others. And similarly for cases where the |
335 |
< |
* apparent lack of work is just due to GC stalls and other |
336 |
< |
* transient system activity. |
325 |
> |
* impedes accuracy. Our main defense is to allow parallelism to |
326 |
> |
* lapse for a while during joins, and use a timeout to see if, |
327 |
> |
* after the resulting settling, there is still a need for |
328 |
> |
* additional workers. This also better copes with the fact that |
329 |
> |
* some of the methods in this class tend to never become compiled |
330 |
> |
* (but are interpreted), so some components of the entire set of |
331 |
> |
* controls might execute 100 times faster than others. And |
332 |
> |
* similarly for cases where the apparent lack of work is just due |
333 |
> |
* to GC stalls and other transient system activity. |
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* |
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* Beware that there is a lot of representation-level coupling |
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* among classes ForkJoinPool, ForkJoinWorkerThread, and |
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* "while ((local = field) != 0)") which are usually the simplest |
346 |
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* way to ensure the required read orderings (which are sometimes |
347 |
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* critical). Also several occurrences of the unusual "do {} |
348 |
< |
* while(!cas...)" which is the simplest way to force an update of |
348 |
> |
* while (!cas...)" which is the simplest way to force an update of |
349 |
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* a CAS'ed variable. There are also other coding oddities that |
350 |
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* help some methods perform reasonably even when interpreted (not |
351 |
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* compiled), at the expense of some messy constructions that |
417 |
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new AtomicInteger(); |
418 |
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|
419 |
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/** |
420 |
+ |
* The time to block in a join (see awaitJoin) before checking if |
421 |
+ |
* a new worker should be (re)started to maintain parallelism |
422 |
+ |
* level. The value should be short enough to maintain global |
423 |
+ |
* responsiveness and progress but long enough to avoid |
424 |
+ |
* counterproductive firings during GC stalls or unrelated system |
425 |
+ |
* activity, and to not bog down systems with continual re-firings |
426 |
+ |
* on GCs or legitimately long waits. |
427 |
+ |
*/ |
428 |
+ |
private static final long JOIN_TIMEOUT_MILLIS = 250L; // 4 per second |
429 |
+ |
|
430 |
+ |
/** |
431 |
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* The wakeup interval (in nanoseconds) for the oldest worker |
432 |
< |
* worker waiting for an event invokes tryShutdownWaiter to shrink |
432 |
> |
* waiting for an event invokes tryShutdownUnusedWorker to shrink |
433 |
|
* the number of workers. The exact value does not matter too |
434 |
|
* much, but should be long enough to slowly release resources |
435 |
|
* during long periods without use without disrupting normal use. |
436 |
|
*/ |
437 |
|
private static final long SHRINK_RATE_NANOS = |
438 |
< |
60L * 1000L * 1000L * 1000L; // one minute |
438 |
> |
30L * 1000L * 1000L * 1000L; // 2 per minute |
439 |
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|
440 |
|
/** |
441 |
|
* Absolute bound for parallelism level. Twice this number plus |
482 |
|
private volatile long stealCount; |
483 |
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|
484 |
|
/** |
485 |
< |
* Encoded record of top of treiber stack of threads waiting for |
485 |
> |
* Encoded record of top of Treiber stack of threads waiting for |
486 |
|
* events. The top 32 bits contain the count being waited for. The |
487 |
|
* bottom 16 bits contains one plus the pool index of waiting |
488 |
|
* worker thread. (Bits 16-31 are unused.) |
501 |
|
private volatile int eventCount; |
502 |
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|
503 |
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/** |
504 |
< |
* Encoded record of top of treiber stack of spare threads waiting |
504 |
> |
* Encoded record of top of Treiber stack of spare threads waiting |
505 |
|
* for resumption. The top 16 bits contain an arbitrary count to |
506 |
|
* avoid ABA effects. The bottom 16bits contains one plus the pool |
507 |
|
* index of waiting worker thread. |
575 |
|
*/ |
576 |
|
private final int poolNumber; |
577 |
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|
570 |
– |
|
578 |
|
// Utilities for CASing fields. Note that most of these |
579 |
|
// are usually manually inlined by callers |
580 |
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|
622 |
|
} |
623 |
|
|
624 |
|
/** |
618 |
– |
* Increments event count |
619 |
– |
*/ |
620 |
– |
private void advanceEventCount() { |
621 |
– |
int c; |
622 |
– |
do {} while(!UNSAFE.compareAndSwapInt(this, eventCountOffset, |
623 |
– |
c = eventCount, c+1)); |
624 |
– |
} |
625 |
– |
|
626 |
– |
/** |
627 |
– |
* Tries incrementing active count; fails on contention. |
628 |
– |
* Called by workers before executing tasks. |
629 |
– |
* |
630 |
– |
* @return true on success |
631 |
– |
*/ |
632 |
– |
final boolean tryIncrementActiveCount() { |
633 |
– |
int c; |
634 |
– |
return UNSAFE.compareAndSwapInt(this, runStateOffset, |
635 |
– |
c = runState, c + 1); |
636 |
– |
} |
637 |
– |
|
638 |
– |
/** |
625 |
|
* Tries decrementing active count; fails on contention. |
626 |
|
* Called when workers cannot find tasks to run. |
627 |
|
*/ |
673 |
|
} |
674 |
|
|
675 |
|
/** |
676 |
< |
* Nulls out record of worker in workers array |
676 |
> |
* Nulls out record of worker in workers array. |
677 |
|
*/ |
678 |
|
private void forgetWorker(ForkJoinWorkerThread w) { |
679 |
|
int idx = w.poolIndex; |
680 |
< |
// Locking helps method recordWorker avoid unecessary expansion |
680 |
> |
// Locking helps method recordWorker avoid unnecessary expansion |
681 |
|
final ReentrantLock lock = this.workerLock; |
682 |
|
lock.lock(); |
683 |
|
try { |
689 |
|
} |
690 |
|
} |
691 |
|
|
706 |
– |
// adding and removing workers |
707 |
– |
|
708 |
– |
/** |
709 |
– |
* Tries to create and add new worker. Assumes that worker counts |
710 |
– |
* are already updated to accommodate the worker, so adjusts on |
711 |
– |
* failure. |
712 |
– |
* |
713 |
– |
* @return the worker, or null on failure |
714 |
– |
*/ |
715 |
– |
private ForkJoinWorkerThread addWorker() { |
716 |
– |
ForkJoinWorkerThread w = null; |
717 |
– |
try { |
718 |
– |
w = factory.newThread(this); |
719 |
– |
} finally { // Adjust on either null or exceptional factory return |
720 |
– |
if (w == null) { |
721 |
– |
decrementWorkerCounts(ONE_RUNNING, ONE_TOTAL); |
722 |
– |
tryTerminate(false); // in case of failure during shutdown |
723 |
– |
} |
724 |
– |
} |
725 |
– |
if (w != null) { |
726 |
– |
w.start(recordWorker(w), ueh); |
727 |
– |
advanceEventCount(); |
728 |
– |
} |
729 |
– |
return w; |
730 |
– |
} |
731 |
– |
|
692 |
|
/** |
693 |
|
* Final callback from terminating worker. Removes record of |
694 |
|
* worker from array, and adjusts counts. If pool is shutting |
695 |
< |
* down, tries to complete terminatation. |
695 |
> |
* down, tries to complete termination. |
696 |
|
* |
697 |
|
* @param w the worker |
698 |
|
*/ |
710 |
|
* Releases workers blocked on a count not equal to current count. |
711 |
|
* Normally called after precheck that eventWaiters isn't zero to |
712 |
|
* avoid wasted array checks. Gives up upon a change in count or |
713 |
< |
* contention, letting other workers take over. |
713 |
> |
* upon releasing two workers, letting others take over. |
714 |
|
*/ |
715 |
|
private void releaseEventWaiters() { |
716 |
|
ForkJoinWorkerThread[] ws = workers; |
717 |
|
int n = ws.length; |
718 |
|
long h = eventWaiters; |
719 |
|
int ec = eventCount; |
720 |
+ |
boolean releasedOne = false; |
721 |
|
ForkJoinWorkerThread w; int id; |
722 |
< |
while ((int)(h >>> EVENT_COUNT_SHIFT) != ec && |
723 |
< |
(id = ((int)(h & WAITER_ID_MASK)) - 1) >= 0 && |
724 |
< |
id < n && (w = ws[id]) != null && |
725 |
< |
UNSAFE.compareAndSwapLong(this, eventWaitersOffset, |
726 |
< |
h, h = w.nextWaiter)) { |
727 |
< |
LockSupport.unpark(w); |
728 |
< |
if (eventWaiters != h || eventCount != ec) |
722 |
> |
while ((id = ((int)(h & WAITER_ID_MASK)) - 1) >= 0 && |
723 |
> |
(int)(h >>> EVENT_COUNT_SHIFT) != ec && |
724 |
> |
id < n && (w = ws[id]) != null) { |
725 |
> |
if (UNSAFE.compareAndSwapLong(this, eventWaitersOffset, |
726 |
> |
h, w.nextWaiter)) { |
727 |
> |
LockSupport.unpark(w); |
728 |
> |
if (releasedOne) // exit on second release |
729 |
> |
break; |
730 |
> |
releasedOne = true; |
731 |
> |
} |
732 |
> |
if (eventCount != ec) |
733 |
|
break; |
734 |
+ |
h = eventWaiters; |
735 |
|
} |
736 |
|
} |
737 |
|
|
748 |
|
|
749 |
|
/** |
750 |
|
* Adds the given worker to event queue and blocks until |
751 |
< |
* terminating or event count advances from the workers |
786 |
< |
* lastEventCount value |
751 |
> |
* terminating or event count advances from the given value |
752 |
|
* |
753 |
|
* @param w the calling worker thread |
754 |
+ |
* @param ec the count |
755 |
|
*/ |
756 |
< |
private void eventSync(ForkJoinWorkerThread w) { |
791 |
< |
int ec = w.lastEventCount; |
756 |
> |
private void eventSync(ForkJoinWorkerThread w, int ec) { |
757 |
|
long nh = (((long)ec) << EVENT_COUNT_SHIFT) | ((long)(w.poolIndex+1)); |
758 |
|
long h; |
759 |
|
while ((runState < SHUTDOWN || !tryTerminate(false)) && |
773 |
|
* event waiter) until terminating or event count advances from |
774 |
|
* the given value. The oldest (first) waiter uses a timed wait to |
775 |
|
* occasionally one-by-one shrink the number of workers (to a |
776 |
< |
* minumum of one) if the pool has not been used for extended |
776 |
> |
* minimum of one) if the pool has not been used for extended |
777 |
|
* periods. |
778 |
|
* |
779 |
|
* @param w the calling worker thread |
786 |
|
(workerCounts & RUNNING_COUNT_MASK) <= 1); |
787 |
|
long startTime = untimed? 0 : System.nanoTime(); |
788 |
|
Thread.interrupted(); // clear/ignore interrupt |
789 |
< |
if (eventCount != ec || !w.isRunning() || |
789 |
> |
if (eventCount != ec || w.runState != 0 || |
790 |
|
runState >= TERMINATING) // recheck after clear |
791 |
|
break; |
792 |
|
if (untimed) |
793 |
|
LockSupport.park(w); |
794 |
|
else { |
795 |
|
LockSupport.parkNanos(w, SHRINK_RATE_NANOS); |
796 |
< |
if (eventCount != ec || !w.isRunning() || |
796 |
> |
if (eventCount != ec || w.runState != 0 || |
797 |
|
runState >= TERMINATING) |
798 |
|
break; |
799 |
|
if (System.nanoTime() - startTime >= SHRINK_RATE_NANOS) |
800 |
< |
tryShutdownWaiter(ec); |
800 |
> |
tryShutdownUnusedWorker(ec); |
801 |
|
} |
802 |
|
} |
803 |
|
} |
804 |
|
} |
805 |
|
|
806 |
< |
/** |
842 |
< |
* Callback from the oldest waiter in awaitEvent waking up after a |
843 |
< |
* period of non-use. Tries (once) to shutdown an event waiter (or |
844 |
< |
* a spare, if one exists). Note that we don't need CAS or locks |
845 |
< |
* here because the method is called only from one thread |
846 |
< |
* occasionally waking (and even misfires are OK). Note that |
847 |
< |
* until the shutdown worker fully terminates, workerCounts |
848 |
< |
* will overestimate total count, which is tolerable. |
849 |
< |
* |
850 |
< |
* @param ec the event count waited on by caller (to abort |
851 |
< |
* attempt if count has since changed). |
852 |
< |
*/ |
853 |
< |
private void tryShutdownWaiter(int ec) { |
854 |
< |
if (spareWaiters != 0) { // prefer killing spares |
855 |
< |
tryShutdownSpare(); |
856 |
< |
return; |
857 |
< |
} |
858 |
< |
ForkJoinWorkerThread[] ws = workers; |
859 |
< |
int n = ws.length; |
860 |
< |
long h = eventWaiters; |
861 |
< |
ForkJoinWorkerThread w; int id; long nh; |
862 |
< |
if (runState == 0 && |
863 |
< |
submissionQueue.isEmpty() && |
864 |
< |
eventCount == ec && |
865 |
< |
(id = ((int)(h & WAITER_ID_MASK)) - 1) >= 0 && |
866 |
< |
id < n && (w = ws[id]) != null && |
867 |
< |
(nh = w.nextWaiter) != 0L && // keep at least one worker |
868 |
< |
UNSAFE.compareAndSwapLong(this, eventWaitersOffset, h, nh)) { |
869 |
< |
w.shutdown(); |
870 |
< |
LockSupport.unpark(w); |
871 |
< |
} |
872 |
< |
releaseEventWaiters(); |
873 |
< |
} |
874 |
< |
|
875 |
< |
// Maintaining spares |
806 |
> |
// Maintaining parallelism |
807 |
|
|
808 |
|
/** |
809 |
< |
* Pushes worker onto the spare stack |
809 |
> |
* Pushes worker onto the spare stack. |
810 |
|
*/ |
811 |
|
final void pushSpare(ForkJoinWorkerThread w) { |
812 |
|
int ns = (++w.spareCount << SPARE_COUNT_SHIFT) | (w.poolIndex + 1); |
815 |
|
} |
816 |
|
|
817 |
|
/** |
818 |
< |
* Callback from oldest spare occasionally waking up. Tries |
819 |
< |
* (once) to shutdown a spare. Same idea as tryShutdownWaiter. |
818 |
> |
* Tries (once) to resume a spare if the number of running |
819 |
> |
* threads is less than target. |
820 |
|
*/ |
821 |
< |
final void tryShutdownSpare() { |
821 |
> |
private void tryResumeSpare() { |
822 |
|
int sw, id; |
892 |
– |
ForkJoinWorkerThread w; |
893 |
– |
ForkJoinWorkerThread[] ws; |
894 |
– |
if ((id = ((sw = spareWaiters) & SPARE_ID_MASK) - 1) >= 0 && |
895 |
– |
id < (ws = workers).length && (w = ws[id]) != null && |
896 |
– |
(workerCounts & RUNNING_COUNT_MASK) >= parallelism && |
897 |
– |
UNSAFE.compareAndSwapInt(this, spareWaitersOffset, |
898 |
– |
sw, w.nextSpare)) { |
899 |
– |
w.shutdown(); |
900 |
– |
LockSupport.unpark(w); |
901 |
– |
advanceEventCount(); |
902 |
– |
} |
903 |
– |
} |
904 |
– |
|
905 |
– |
/** |
906 |
– |
* Tries (once) to resume a spare if worker counts match |
907 |
– |
* the given count. |
908 |
– |
* |
909 |
– |
* @param wc workerCounts value on invocation of this method |
910 |
– |
*/ |
911 |
– |
private void tryResumeSpare(int wc) { |
823 |
|
ForkJoinWorkerThread[] ws = workers; |
824 |
|
int n = ws.length; |
825 |
< |
int sw, id, rs; ForkJoinWorkerThread w; |
826 |
< |
if ((id = ((sw = spareWaiters) & SPARE_ID_MASK) - 1) >= 0 && |
825 |
> |
ForkJoinWorkerThread w; |
826 |
> |
if ((sw = spareWaiters) != 0 && |
827 |
> |
(id = (sw & SPARE_ID_MASK) - 1) >= 0 && |
828 |
|
id < n && (w = ws[id]) != null && |
829 |
< |
(rs = runState) < TERMINATING && |
830 |
< |
eventWaiters == 0L && workerCounts == wc) { |
831 |
< |
// In case all workers busy, heuristically back off to let settle |
832 |
< |
Thread.yield(); |
833 |
< |
if (eventWaiters == 0L && runState == rs && // recheck |
834 |
< |
workerCounts == wc && spareWaiters == sw && |
835 |
< |
UNSAFE.compareAndSwapInt(this, spareWaitersOffset, |
836 |
< |
sw, w.nextSpare)) { |
837 |
< |
int c; // increment running count before resume |
838 |
< |
do {} while(!UNSAFE.compareAndSwapInt |
839 |
< |
(this, workerCountsOffset, |
840 |
< |
c = workerCounts, c + ONE_RUNNING)); |
929 |
< |
if (w.tryUnsuspend()) |
930 |
< |
LockSupport.unpark(w); |
931 |
< |
else // back out if w was shutdown |
932 |
< |
decrementWorkerCounts(ONE_RUNNING, 0); |
933 |
< |
} |
829 |
> |
(workerCounts & RUNNING_COUNT_MASK) < parallelism && |
830 |
> |
spareWaiters == sw && |
831 |
> |
UNSAFE.compareAndSwapInt(this, spareWaitersOffset, |
832 |
> |
sw, w.nextSpare)) { |
833 |
> |
int c; // increment running count before resume |
834 |
> |
do {} while (!UNSAFE.compareAndSwapInt |
835 |
> |
(this, workerCountsOffset, |
836 |
> |
c = workerCounts, c + ONE_RUNNING)); |
837 |
> |
if (w.tryUnsuspend()) |
838 |
> |
LockSupport.unpark(w); |
839 |
> |
else // back out if w was shutdown |
840 |
> |
decrementWorkerCounts(ONE_RUNNING, 0); |
841 |
|
} |
842 |
|
} |
843 |
|
|
937 |
– |
// adding workers on demand |
938 |
– |
|
844 |
|
/** |
845 |
< |
* Adds one or more workers if needed to establish target parallelism. |
846 |
< |
* Retries upon contention. |
845 |
> |
* Tries to increase the number of running workers if below target |
846 |
> |
* parallelism: If a spare exists tries to resume it via |
847 |
> |
* tryResumeSpare. Otherwise, if not enough total workers or all |
848 |
> |
* existing workers are busy, adds a new worker. In all cases also |
849 |
> |
* helps wake up releasable workers waiting for work. |
850 |
|
*/ |
851 |
< |
private void addWorkerIfBelowTarget() { |
851 |
> |
private void helpMaintainParallelism() { |
852 |
|
int pc = parallelism; |
853 |
< |
int wc; |
854 |
< |
while (((wc = workerCounts) >>> TOTAL_COUNT_SHIFT) < pc && |
855 |
< |
runState < TERMINATING) { |
856 |
< |
if (UNSAFE.compareAndSwapInt(this, workerCountsOffset, wc, |
857 |
< |
wc + (ONE_RUNNING|ONE_TOTAL))) { |
858 |
< |
if (addWorker() == null) |
853 |
> |
int wc, rs, tc; |
854 |
> |
while (((wc = workerCounts) & RUNNING_COUNT_MASK) < pc && |
855 |
> |
(rs = runState) < TERMINATING) { |
856 |
> |
if (spareWaiters != 0) |
857 |
> |
tryResumeSpare(); |
858 |
> |
else if ((tc = wc >>> TOTAL_COUNT_SHIFT) >= MAX_WORKERS || |
859 |
> |
(tc >= pc && (rs & ACTIVE_COUNT_MASK) != tc)) |
860 |
> |
break; // enough total |
861 |
> |
else if (runState == rs && workerCounts == wc && |
862 |
> |
UNSAFE.compareAndSwapInt(this, workerCountsOffset, wc, |
863 |
> |
wc + (ONE_RUNNING|ONE_TOTAL))) { |
864 |
> |
ForkJoinWorkerThread w = null; |
865 |
> |
try { |
866 |
> |
w = factory.newThread(this); |
867 |
> |
} finally { // adjust on null or exceptional factory return |
868 |
> |
if (w == null) { |
869 |
> |
decrementWorkerCounts(ONE_RUNNING, ONE_TOTAL); |
870 |
> |
tryTerminate(false); // handle failure during shutdown |
871 |
> |
} |
872 |
> |
} |
873 |
> |
if (w == null) |
874 |
|
break; |
875 |
+ |
w.start(recordWorker(w), ueh); |
876 |
+ |
if ((workerCounts >>> TOTAL_COUNT_SHIFT) >= pc) { |
877 |
+ |
int c; // advance event count |
878 |
+ |
UNSAFE.compareAndSwapInt(this, eventCountOffset, |
879 |
+ |
c = eventCount, c+1); |
880 |
+ |
break; // add at most one unless total below target |
881 |
+ |
} |
882 |
|
} |
883 |
|
} |
884 |
+ |
if (eventWaiters != 0L) |
885 |
+ |
releaseEventWaiters(); |
886 |
|
} |
887 |
|
|
888 |
|
/** |
889 |
< |
* Tries (once) to add a new worker if all existing workers are |
890 |
< |
* busy, and there are either no running workers or the deficit is |
891 |
< |
* at least twice the surplus. |
892 |
< |
* |
893 |
< |
* @param wc workerCounts value on invocation of this method |
894 |
< |
*/ |
895 |
< |
private void tryAddWorkerIfBusy(int wc) { |
964 |
< |
int tc, rc, rs; |
965 |
< |
int pc = parallelism; |
966 |
< |
if ((tc = wc >>> TOTAL_COUNT_SHIFT) < MAX_WORKERS && |
967 |
< |
((rc = wc & RUNNING_COUNT_MASK) == 0 || |
968 |
< |
rc < pc - ((tc - pc) << 1)) && |
969 |
< |
(rs = runState) < TERMINATING && |
970 |
< |
(rs & ACTIVE_COUNT_MASK) == tc) { |
971 |
< |
// Since all workers busy, heuristically back off to let settle |
972 |
< |
Thread.yield(); |
973 |
< |
if (eventWaiters == 0L && spareWaiters == 0 && // recheck |
974 |
< |
runState == rs && workerCounts == wc && |
975 |
< |
UNSAFE.compareAndSwapInt(this, workerCountsOffset, wc, |
976 |
< |
wc + (ONE_RUNNING|ONE_TOTAL))) |
977 |
< |
addWorker(); |
978 |
< |
} |
979 |
< |
} |
980 |
< |
|
981 |
< |
/** |
982 |
< |
* Does at most one of: |
983 |
< |
* |
984 |
< |
* 1. Help wake up existing workers waiting for work via |
985 |
< |
* releaseEventWaiters. (If any exist, then it doesn't |
986 |
< |
* matter right now if under target parallelism level.) |
987 |
< |
* |
988 |
< |
* 2. If a spare exists, try (once) to resume it via tryResumeSpare. |
989 |
< |
* |
990 |
< |
* 3. If there are not enough total workers, add some |
991 |
< |
* via addWorkerIfBelowTarget; |
889 |
> |
* Callback from the oldest waiter in awaitEvent waking up after a |
890 |
> |
* period of non-use. If all workers are idle, tries (once) to |
891 |
> |
* shutdown an event waiter or a spare, if one exists. Note that |
892 |
> |
* we don't need CAS or locks here because the method is called |
893 |
> |
* only from one thread occasionally waking (and even misfires are |
894 |
> |
* OK). Note that until the shutdown worker fully terminates, |
895 |
> |
* workerCounts will overestimate total count, which is tolerable. |
896 |
|
* |
897 |
< |
* 4. Try (once) to add a new worker if all existing workers |
898 |
< |
* are busy, via tryAddWorkerIfBusy |
897 |
> |
* @param ec the event count waited on by caller (to abort |
898 |
> |
* attempt if count has since changed). |
899 |
|
*/ |
900 |
< |
private void helpMaintainParallelism() { |
901 |
< |
long h; int pc, wc; |
902 |
< |
if (((int)((h = eventWaiters) & WAITER_ID_MASK)) != 0) { |
903 |
< |
if ((int)(h >>> EVENT_COUNT_SHIFT) != eventCount) |
904 |
< |
releaseEventWaiters(); // avoid useless call |
905 |
< |
} |
906 |
< |
else if ((pc = parallelism) > |
907 |
< |
((wc = workerCounts) & RUNNING_COUNT_MASK)) { |
908 |
< |
if (spareWaiters != 0) |
909 |
< |
tryResumeSpare(wc); |
910 |
< |
else if ((wc >>> TOTAL_COUNT_SHIFT) < pc) |
911 |
< |
addWorkerIfBelowTarget(); |
912 |
< |
else |
913 |
< |
tryAddWorkerIfBusy(wc); |
900 |
> |
private void tryShutdownUnusedWorker(int ec) { |
901 |
> |
if (runState == 0 && eventCount == ec) { // only trigger if all idle |
902 |
> |
ForkJoinWorkerThread[] ws = workers; |
903 |
> |
int n = ws.length; |
904 |
> |
ForkJoinWorkerThread w = null; |
905 |
> |
boolean shutdown = false; |
906 |
> |
int sw; |
907 |
> |
long h; |
908 |
> |
if ((sw = spareWaiters) != 0) { // prefer killing spares |
909 |
> |
int id = (sw & SPARE_ID_MASK) - 1; |
910 |
> |
if (id >= 0 && id < n && (w = ws[id]) != null && |
911 |
> |
UNSAFE.compareAndSwapInt(this, spareWaitersOffset, |
912 |
> |
sw, w.nextSpare)) |
913 |
> |
shutdown = true; |
914 |
> |
} |
915 |
> |
else if ((h = eventWaiters) != 0L) { |
916 |
> |
long nh; |
917 |
> |
int id = ((int)(h & WAITER_ID_MASK)) - 1; |
918 |
> |
if (id >= 0 && id < n && (w = ws[id]) != null && |
919 |
> |
(nh = w.nextWaiter) != 0L && // keep at least one worker |
920 |
> |
UNSAFE.compareAndSwapLong(this, eventWaitersOffset, h, nh)) |
921 |
> |
shutdown = true; |
922 |
> |
} |
923 |
> |
if (w != null && shutdown) { |
924 |
> |
w.shutdown(); |
925 |
> |
LockSupport.unpark(w); |
926 |
> |
} |
927 |
|
} |
928 |
+ |
releaseEventWaiters(); // in case of interference |
929 |
|
} |
930 |
|
|
931 |
|
/** |
933 |
|
* stealing a task or taking a submission and running it). |
934 |
|
* Performs one or more of the following: |
935 |
|
* |
936 |
< |
* 1. If the worker is active, try to set its active status to |
937 |
< |
* inactive and update activeCount. On contention, we may try |
938 |
< |
* again on this or subsequent call. |
939 |
< |
* |
940 |
< |
* 2. Release any existing event waiters that are now relesable |
941 |
< |
* |
942 |
< |
* 3. If there are too many running threads, suspend this worker |
943 |
< |
* (first forcing inactive if necessary). If it is not |
944 |
< |
* needed, it may be killed while suspended via |
945 |
< |
* tryShutdownSpare. Otherwise, upon resume it rechecks to make |
946 |
< |
* sure that it is still needed. |
947 |
< |
* |
948 |
< |
* 4. If more than 1 miss, await the next task event via |
949 |
< |
* eventSync (first forcing inactivation if necessary), upon |
950 |
< |
* which worker may also be killed, via tryShutdownWaiter. |
951 |
< |
* |
952 |
< |
* 5. Help reactivate other workers via helpMaintainParallelism |
936 |
> |
* 1. If the worker is active and either did not run a task |
937 |
> |
* or there are too many workers, try to set its active status |
938 |
> |
* to inactive and update activeCount. On contention, we may |
939 |
> |
* try again in this or a subsequent call. |
940 |
> |
* |
941 |
> |
* 2. If not enough total workers, help create some. |
942 |
> |
* |
943 |
> |
* 3. If there are too many running workers, suspend this worker |
944 |
> |
* (first forcing inactive if necessary). If it is not needed, |
945 |
> |
* it may be shutdown while suspended (via |
946 |
> |
* tryShutdownUnusedWorker). Otherwise, upon resume it |
947 |
> |
* rechecks running thread count and need for event sync. |
948 |
> |
* |
949 |
> |
* 4. If worker did not run a task, await the next task event via |
950 |
> |
* eventSync if necessary (first forcing inactivation), upon |
951 |
> |
* which the worker may be shutdown via |
952 |
> |
* tryShutdownUnusedWorker. Otherwise, help release any |
953 |
> |
* existing event waiters that are now releasable, |
954 |
|
* |
955 |
|
* @param w the worker |
956 |
< |
* @param misses the number of scans by caller failing to find work |
1038 |
< |
* (saturating at 2 to avoid wraparound) |
956 |
> |
* @param ran true if worker ran a task since last call to this method |
957 |
|
*/ |
958 |
< |
final void preStep(ForkJoinWorkerThread w, int misses) { |
958 |
> |
final void preStep(ForkJoinWorkerThread w, boolean ran) { |
959 |
> |
int wec = w.lastEventCount; |
960 |
|
boolean active = w.active; |
961 |
+ |
boolean inactivate = false; |
962 |
|
int pc = parallelism; |
963 |
< |
for (;;) { |
964 |
< |
int rs, wc, rc, ec; long h; |
965 |
< |
if (active && UNSAFE.compareAndSwapInt(this, runStateOffset, |
966 |
< |
rs = runState, rs - 1)) |
967 |
< |
active = w.active = false; |
968 |
< |
if (((int)((h = eventWaiters) & WAITER_ID_MASK)) != 0 && |
969 |
< |
(int)(h >>> EVENT_COUNT_SHIFT) != eventCount) { |
970 |
< |
releaseEventWaiters(); |
1051 |
< |
if (misses > 1) |
1052 |
< |
continue; // clear before sync below |
1053 |
< |
} |
1054 |
< |
if ((rc = ((wc = workerCounts) & RUNNING_COUNT_MASK)) > pc) { |
1055 |
< |
if (!active && // must inactivate to suspend |
963 |
> |
int rs; |
964 |
> |
while (w.runState == 0 && (rs = runState) < TERMINATING) { |
965 |
> |
if ((inactivate || (active && (rs & ACTIVE_COUNT_MASK) >= pc)) && |
966 |
> |
UNSAFE.compareAndSwapInt(this, runStateOffset, rs, rs - 1)) |
967 |
> |
inactivate = active = w.active = false; |
968 |
> |
int wc = workerCounts; |
969 |
> |
if ((wc & RUNNING_COUNT_MASK) > pc) { |
970 |
> |
if (!(inactivate |= active) && // must inactivate to suspend |
971 |
|
workerCounts == wc && // try to suspend as spare |
972 |
|
UNSAFE.compareAndSwapInt(this, workerCountsOffset, |
973 |
< |
wc, wc - ONE_RUNNING)) { |
973 |
> |
wc, wc - ONE_RUNNING)) |
974 |
|
w.suspendAsSpare(); |
1060 |
– |
if (!w.isRunning()) |
1061 |
– |
break; // was killed while spare |
1062 |
– |
} |
1063 |
– |
continue; |
975 |
|
} |
976 |
< |
if (misses > 0) { |
977 |
< |
if ((ec = eventCount) == w.lastEventCount && misses > 1) { |
978 |
< |
if (!active) { // must inactivate to sync |
979 |
< |
eventSync(w); |
980 |
< |
if (w.isRunning()) |
981 |
< |
misses = 1; // don't re-sync |
982 |
< |
else |
983 |
< |
break; // was killed while waiting |
984 |
< |
} |
985 |
< |
continue; |
976 |
> |
else if ((wc >>> TOTAL_COUNT_SHIFT) < pc) |
977 |
> |
helpMaintainParallelism(); // not enough workers |
978 |
> |
else if (!ran) { |
979 |
> |
long h = eventWaiters; |
980 |
> |
int ec = eventCount; |
981 |
> |
if (h != 0L && (int)(h >>> EVENT_COUNT_SHIFT) != ec) |
982 |
> |
releaseEventWaiters(); // release others before waiting |
983 |
> |
else if (ec != wec) { |
984 |
> |
w.lastEventCount = ec; // no need to wait |
985 |
> |
break; |
986 |
|
} |
987 |
< |
w.lastEventCount = ec; |
987 |
> |
else if (!(inactivate |= active)) |
988 |
> |
eventSync(w, wec); // must inactivate before sync |
989 |
|
} |
990 |
< |
if (rc < pc) |
991 |
< |
helpMaintainParallelism(); |
1080 |
< |
break; |
990 |
> |
else |
991 |
> |
break; |
992 |
|
} |
993 |
|
} |
994 |
|
|
995 |
|
/** |
996 |
|
* Helps and/or blocks awaiting join of the given task. |
997 |
< |
* Alternates between helpJoinTask() and helpMaintainParallelism() |
1087 |
< |
* as many times as there is a deficit in running count (or longer |
1088 |
< |
* if running count would become zero), then blocks if task still |
1089 |
< |
* not done. |
997 |
> |
* See above for explanation. |
998 |
|
* |
999 |
|
* @param joinMe the task to join |
1000 |
+ |
* @param worker the current worker thread |
1001 |
|
*/ |
1002 |
|
final void awaitJoin(ForkJoinTask<?> joinMe, ForkJoinWorkerThread worker) { |
1003 |
< |
int threshold = parallelism; // descend blocking thresholds |
1003 |
> |
int retries = 2 + (parallelism >> 2); // #helpJoins before blocking |
1004 |
|
while (joinMe.status >= 0) { |
1005 |
< |
boolean block; int wc; |
1005 |
> |
int wc; |
1006 |
|
worker.helpJoinTask(joinMe); |
1007 |
|
if (joinMe.status < 0) |
1008 |
|
break; |
1009 |
< |
if (((wc = workerCounts) & RUNNING_COUNT_MASK) <= threshold) { |
1010 |
< |
if (threshold > 0) |
1011 |
< |
--threshold; |
1012 |
< |
else |
1013 |
< |
advanceEventCount(); // force release |
1014 |
< |
block = false; |
1015 |
< |
} |
1016 |
< |
else |
1017 |
< |
block = UNSAFE.compareAndSwapInt(this, workerCountsOffset, |
1018 |
< |
wc, wc - ONE_RUNNING); |
1019 |
< |
helpMaintainParallelism(); |
1020 |
< |
if (block) { |
1021 |
< |
int c; |
1022 |
< |
joinMe.internalAwaitDone(); |
1009 |
> |
else if (retries > 0) |
1010 |
> |
--retries; |
1011 |
> |
else if (((wc = workerCounts) & RUNNING_COUNT_MASK) != 0 && |
1012 |
> |
UNSAFE.compareAndSwapInt(this, workerCountsOffset, |
1013 |
> |
wc, wc - ONE_RUNNING)) { |
1014 |
> |
int stat, c; long h; |
1015 |
> |
while ((stat = joinMe.status) >= 0 && |
1016 |
> |
(h = eventWaiters) != 0L && // help release others |
1017 |
> |
(int)(h >>> EVENT_COUNT_SHIFT) != eventCount) |
1018 |
> |
releaseEventWaiters(); |
1019 |
> |
if (stat >= 0 && |
1020 |
> |
((workerCounts & RUNNING_COUNT_MASK) == 0 || |
1021 |
> |
(stat = |
1022 |
> |
joinMe.internalAwaitDone(JOIN_TIMEOUT_MILLIS)) >= 0)) |
1023 |
> |
helpMaintainParallelism(); // timeout or no running workers |
1024 |
|
do {} while (!UNSAFE.compareAndSwapInt |
1025 |
|
(this, workerCountsOffset, |
1026 |
|
c = workerCounts, c + ONE_RUNNING)); |
1027 |
< |
break; |
1027 |
> |
if (stat < 0) |
1028 |
> |
break; // else restart |
1029 |
|
} |
1030 |
|
} |
1031 |
|
} |
1032 |
|
|
1033 |
|
/** |
1034 |
< |
* Same idea as awaitJoin, but no helping |
1034 |
> |
* Same idea as awaitJoin, but no helping, retries, or timeouts. |
1035 |
|
*/ |
1036 |
|
final void awaitBlocker(ManagedBlocker blocker) |
1037 |
|
throws InterruptedException { |
1127 |
– |
int threshold = parallelism; |
1038 |
|
while (!blocker.isReleasable()) { |
1039 |
< |
boolean block; int wc; |
1040 |
< |
if (((wc = workerCounts) & RUNNING_COUNT_MASK) <= threshold) { |
1041 |
< |
if (threshold > 0) |
1042 |
< |
--threshold; |
1133 |
< |
else |
1134 |
< |
advanceEventCount(); |
1135 |
< |
block = false; |
1136 |
< |
} |
1137 |
< |
else |
1138 |
< |
block = UNSAFE.compareAndSwapInt(this, workerCountsOffset, |
1139 |
< |
wc, wc - ONE_RUNNING); |
1140 |
< |
helpMaintainParallelism(); |
1141 |
< |
if (block) { |
1039 |
> |
int wc = workerCounts; |
1040 |
> |
if ((wc & RUNNING_COUNT_MASK) != 0 && |
1041 |
> |
UNSAFE.compareAndSwapInt(this, workerCountsOffset, |
1042 |
> |
wc, wc - ONE_RUNNING)) { |
1043 |
|
try { |
1044 |
< |
do {} while (!blocker.isReleasable() && !blocker.block()); |
1044 |
> |
while (!blocker.isReleasable()) { |
1045 |
> |
long h = eventWaiters; |
1046 |
> |
if (h != 0L && |
1047 |
> |
(int)(h >>> EVENT_COUNT_SHIFT) != eventCount) |
1048 |
> |
releaseEventWaiters(); |
1049 |
> |
else if ((workerCounts & RUNNING_COUNT_MASK) == 0 && |
1050 |
> |
runState < TERMINATING) |
1051 |
> |
helpMaintainParallelism(); |
1052 |
> |
else if (blocker.block()) |
1053 |
> |
break; |
1054 |
> |
} |
1055 |
|
} finally { |
1056 |
|
int c; |
1057 |
|
do {} while (!UNSAFE.compareAndSwapInt |
1101 |
|
private void startTerminating() { |
1102 |
|
cancelSubmissions(); |
1103 |
|
for (int passes = 0; passes < 4 && workerCounts != 0; ++passes) { |
1104 |
< |
advanceEventCount(); |
1104 |
> |
int c; // advance event count |
1105 |
> |
UNSAFE.compareAndSwapInt(this, eventCountOffset, |
1106 |
> |
c = eventCount, c+1); |
1107 |
|
eventWaiters = 0L; // clobber lists |
1108 |
|
spareWaiters = 0; |
1109 |
< |
ForkJoinWorkerThread[] ws = workers; |
1197 |
< |
int n = ws.length; |
1198 |
< |
for (int i = 0; i < n; ++i) { |
1199 |
< |
ForkJoinWorkerThread w = ws[i]; |
1109 |
> |
for (ForkJoinWorkerThread w : workers) { |
1110 |
|
if (w != null) { |
1111 |
|
w.shutdown(); |
1112 |
|
if (passes > 0 && !w.isTerminated()) { |
1125 |
|
} |
1126 |
|
|
1127 |
|
/** |
1128 |
< |
* Clear out and cancel submissions, ignoring exceptions |
1128 |
> |
* Clears out and cancels submissions, ignoring exceptions. |
1129 |
|
*/ |
1130 |
|
private void cancelSubmissions() { |
1131 |
|
ForkJoinTask<?> task; |
1140 |
|
// misc support for ForkJoinWorkerThread |
1141 |
|
|
1142 |
|
/** |
1143 |
< |
* Returns pool number |
1143 |
> |
* Returns pool number. |
1144 |
|
*/ |
1145 |
|
final int getPoolNumber() { |
1146 |
|
return poolNumber; |
1147 |
|
} |
1148 |
|
|
1149 |
|
/** |
1150 |
< |
* Tries to accumulates steal count from a worker, clearing |
1151 |
< |
* the worker's value. |
1150 |
> |
* Tries to accumulate steal count from a worker, clearing |
1151 |
> |
* the worker's value if successful. |
1152 |
|
* |
1153 |
|
* @return true if worker steal count now zero |
1154 |
|
*/ |
1170 |
|
*/ |
1171 |
|
final int idlePerActive() { |
1172 |
|
int pc = parallelism; // use parallelism, not rc |
1173 |
< |
int ac = runState; // no mask -- artifically boosts during shutdown |
1173 |
> |
int ac = runState; // no mask -- artificially boosts during shutdown |
1174 |
|
// Use exact results for small values, saturate past 4 |
1175 |
< |
return pc <= ac? 0 : pc >>> 1 <= ac? 1 : pc >>> 2 <= ac? 3 : pc >>> 3; |
1175 |
> |
return ((pc <= ac) ? 0 : |
1176 |
> |
(pc >>> 1 <= ac) ? 1 : |
1177 |
> |
(pc >>> 2 <= ac) ? 3 : |
1178 |
> |
pc >>> 3); |
1179 |
|
} |
1180 |
|
|
1181 |
|
// Public and protected methods |
1225 |
|
* use {@link #defaultForkJoinWorkerThreadFactory}. |
1226 |
|
* @param handler the handler for internal worker threads that |
1227 |
|
* terminate due to unrecoverable errors encountered while executing |
1228 |
< |
* tasks. For default value, use <code>null</code>. |
1228 |
> |
* tasks. For default value, use {@code null}. |
1229 |
|
* @param asyncMode if true, |
1230 |
|
* establishes local first-in-first-out scheduling mode for forked |
1231 |
|
* tasks that are never joined. This mode may be more appropriate |
1232 |
|
* than default locally stack-based mode in applications in which |
1233 |
|
* worker threads only process event-style asynchronous tasks. |
1234 |
< |
* For default value, use <code>false</code>. |
1234 |
> |
* For default value, use {@code false}. |
1235 |
|
* @throws IllegalArgumentException if parallelism less than or |
1236 |
|
* equal to zero, or greater than implementation limit |
1237 |
|
* @throws NullPointerException if the factory is null |
1266 |
|
* @param pc the initial parallelism level |
1267 |
|
*/ |
1268 |
|
private static int initialArraySizeFor(int pc) { |
1269 |
< |
// See Hackers Delight, sec 3.2. We know MAX_WORKERS < (1 >>> 16) |
1269 |
> |
// If possible, initially allocate enough space for one spare |
1270 |
|
int size = pc < MAX_WORKERS ? pc + 1 : MAX_WORKERS; |
1271 |
+ |
// See Hackers Delight, sec 3.2. We know MAX_WORKERS < (1 >>> 16) |
1272 |
|
size |= size >>> 1; |
1273 |
|
size |= size >>> 2; |
1274 |
|
size |= size >>> 4; |
1287 |
|
if (runState >= SHUTDOWN) |
1288 |
|
throw new RejectedExecutionException(); |
1289 |
|
submissionQueue.offer(task); |
1290 |
< |
advanceEventCount(); |
1291 |
< |
if (eventWaiters != 0L) |
1292 |
< |
releaseEventWaiters(); |
1379 |
< |
if ((workerCounts >>> TOTAL_COUNT_SHIFT) < parallelism) |
1380 |
< |
addWorkerIfBelowTarget(); |
1290 |
> |
int c; // try to increment event count -- CAS failure OK |
1291 |
> |
UNSAFE.compareAndSwapInt(this, eventCountOffset, c = eventCount, c+1); |
1292 |
> |
helpMaintainParallelism(); // create, start, or resume some workers |
1293 |
|
} |
1294 |
|
|
1295 |
|
/** |
1526 |
|
*/ |
1527 |
|
public long getQueuedTaskCount() { |
1528 |
|
long count = 0; |
1529 |
< |
ForkJoinWorkerThread[] ws = workers; |
1618 |
< |
int n = ws.length; |
1619 |
< |
for (int i = 0; i < n; ++i) { |
1620 |
< |
ForkJoinWorkerThread w = ws[i]; |
1529 |
> |
for (ForkJoinWorkerThread w : workers) |
1530 |
|
if (w != null) |
1531 |
|
count += w.getQueueSize(); |
1623 |
– |
} |
1532 |
|
return count; |
1533 |
|
} |
1534 |
|
|
1583 |
|
*/ |
1584 |
|
protected int drainTasksTo(Collection<? super ForkJoinTask<?>> c) { |
1585 |
|
int count = submissionQueue.drainTo(c); |
1586 |
< |
ForkJoinWorkerThread[] ws = workers; |
1679 |
< |
int n = ws.length; |
1680 |
< |
for (int i = 0; i < n; ++i) { |
1681 |
< |
ForkJoinWorkerThread w = ws[i]; |
1586 |
> |
for (ForkJoinWorkerThread w : workers) |
1587 |
|
if (w != null) |
1588 |
|
count += w.drainTasksTo(c); |
1684 |
– |
} |
1589 |
|
return count; |
1590 |
|
} |
1591 |
|
|
1712 |
|
throws InterruptedException { |
1713 |
|
try { |
1714 |
|
return termination.awaitAdvanceInterruptibly(0, timeout, unit) > 0; |
1715 |
< |
} catch(TimeoutException ex) { |
1715 |
> |
} catch (TimeoutException ex) { |
1716 |
|
return false; |
1717 |
|
} |
1718 |
|
} |
1842 |
|
private static final long eventCountOffset = |
1843 |
|
objectFieldOffset("eventCount", ForkJoinPool.class); |
1844 |
|
private static final long eventWaitersOffset = |
1845 |
< |
objectFieldOffset("eventWaiters",ForkJoinPool.class); |
1845 |
> |
objectFieldOffset("eventWaiters", ForkJoinPool.class); |
1846 |
|
private static final long stealCountOffset = |
1847 |
< |
objectFieldOffset("stealCount",ForkJoinPool.class); |
1847 |
> |
objectFieldOffset("stealCount", ForkJoinPool.class); |
1848 |
|
private static final long spareWaitersOffset = |
1849 |
< |
objectFieldOffset("spareWaiters",ForkJoinPool.class); |
1849 |
> |
objectFieldOffset("spareWaiters", ForkJoinPool.class); |
1850 |
|
|
1851 |
|
private static long objectFieldOffset(String field, Class<?> klazz) { |
1852 |
|
try { |