161 |
|
* re-activate a spare thread to compensate for blocked |
162 |
|
* joiners until they unblock. |
163 |
|
* |
164 |
< |
* Because the determining existence of conservatively safe |
165 |
< |
* helping targets, the availability of already-created spares, |
166 |
< |
* and the apparent need to create new spares are all racy and |
167 |
< |
* require heuristic guidance, we rely on multiple retries of |
168 |
< |
* each. Further, because it is impossible to keep exactly the |
169 |
< |
* target (parallelism) number of threads running at any given |
170 |
< |
* time, we allow compensation during joins to fail, and enlist |
171 |
< |
* all other threads to help out whenever they are not otherwise |
172 |
< |
* occupied (i.e., mainly in method preStep). |
164 |
> |
* It is impossible to keep exactly the target (parallelism) |
165 |
> |
* number of threads running at any given time. Determining |
166 |
> |
* existence of conservatively safe helping targets, the |
167 |
> |
* availability of already-created spares, and the apparent need |
168 |
> |
* to create new spares are all racy and require heuristic |
169 |
> |
* guidance, so we rely on multiple retries of each. Compensation |
170 |
> |
* occurs in slow-motion. It is triggered only upon timeouts of |
171 |
> |
* Object.wait used for joins. This reduces poor decisions that |
172 |
> |
* would otherwise be made when threads are waiting for others |
173 |
> |
* that are stalled because of unrelated activities such as |
174 |
> |
* garbage collection. |
175 |
|
* |
176 |
|
* The ManagedBlocker extension API can't use helping so relies |
177 |
|
* only on compensation in method awaitBlocker. |
261 |
|
* workers that previously could not find a task to now find one: |
262 |
|
* Submission of a new task to the pool, or another worker pushing |
263 |
|
* a task onto a previously empty queue. (We also use this |
264 |
< |
* mechanism for termination actions that require wakeups of idle |
265 |
< |
* workers). Each worker maintains its last known event count, |
266 |
< |
* and blocks when a scan for work did not find a task AND its |
267 |
< |
* lastEventCount matches the current eventCount. Waiting idle |
268 |
< |
* workers are recorded in a variant of Treiber stack headed by |
269 |
< |
* field eventWaiters which, when nonzero, encodes the thread |
270 |
< |
* index and count awaited for by the worker thread most recently |
271 |
< |
* calling eventSync. This thread in turn has a record (field |
272 |
< |
* nextEventWaiter) for the next waiting worker. In addition to |
273 |
< |
* allowing simpler decisions about need for wakeup, the event |
274 |
< |
* count bits in eventWaiters serve the role of tags to avoid ABA |
275 |
< |
* errors in Treiber stacks. To reduce delays in task diffusion, |
276 |
< |
* workers not otherwise occupied may invoke method |
277 |
< |
* releaseEventWaiters, that removes and signals (unparks) workers |
278 |
< |
* not waiting on current count. To reduce stalls, To minimize |
279 |
< |
* task production stalls associate with signalling, any worker |
280 |
< |
* pushing a task on an empty queue invokes the weaker method |
279 |
< |
* signalWork, that only releases idle workers until it detects |
280 |
< |
* interference by other threads trying to release, and lets them |
281 |
< |
* take over. The net effect is a tree-like diffusion of signals, |
282 |
< |
* where released threads (and possibly others) help with unparks. |
283 |
< |
* To further reduce contention effects a bit, failed CASes to |
284 |
< |
* increment field eventCount are tolerated without retries. |
264 |
> |
* mechanism for configuration and termination actions that |
265 |
> |
* require wakeups of idle workers). Each worker maintains its |
266 |
> |
* last known event count, and blocks when a scan for work did not |
267 |
> |
* find a task AND its lastEventCount matches the current |
268 |
> |
* eventCount. Waiting idle workers are recorded in a variant of |
269 |
> |
* Treiber stack headed by field eventWaiters which, when nonzero, |
270 |
> |
* encodes the thread index and count awaited for by the worker |
271 |
> |
* thread most recently calling eventSync. This thread in turn has |
272 |
> |
* a record (field nextEventWaiter) for the next waiting worker. |
273 |
> |
* In addition to allowing simpler decisions about need for |
274 |
> |
* wakeup, the event count bits in eventWaiters serve the role of |
275 |
> |
* tags to avoid ABA errors in Treiber stacks. Upon any wakeup, |
276 |
> |
* released threads also try to release at most two others. The |
277 |
> |
* net effect is a tree-like diffusion of signals, where released |
278 |
> |
* threads (and possibly others) help with unparks. To further |
279 |
> |
* reduce contention effects a bit, failed CASes to increment |
280 |
> |
* field eventCount are tolerated without retries in signalWork. |
281 |
|
* Conceptually they are merged into the same event, which is OK |
282 |
|
* when their only purpose is to enable workers to scan for work. |
283 |
|
* |
284 |
< |
* 5. Managing suspension of extra workers. When a worker is about |
285 |
< |
* to block waiting for a join (or via ManagedBlockers), we may |
286 |
< |
* create a new thread to maintain parallelism level, or at least |
287 |
< |
* avoid starvation. Usually, extra threads are needed for only |
288 |
< |
* very short periods, yet join dependencies are such that we |
289 |
< |
* sometimes need them in bursts. Rather than create new threads |
290 |
< |
* each time this happens, we suspend no-longer-needed extra ones |
291 |
< |
* as "spares". For most purposes, we don't distinguish "extra" |
292 |
< |
* spare threads from normal "core" threads: On each call to |
293 |
< |
* preStep (the only point at which we can do this) a worker |
294 |
< |
* checks to see if there are now too many running workers, and if |
295 |
< |
* so, suspends itself. Method helpMaintainParallelism looks for |
296 |
< |
* suspended threads to resume before considering creating a new |
297 |
< |
* replacement. The spares themselves are encoded on another |
298 |
< |
* variant of a Treiber Stack, headed at field "spareWaiters". |
299 |
< |
* Note that the use of spares is intrinsically racy. One thread |
300 |
< |
* may become a spare at about the same time as another is |
301 |
< |
* needlessly being created. We counteract this and related slop |
302 |
< |
* in part by requiring resumed spares to immediately recheck (in |
303 |
< |
* preStep) to see whether they they should re-suspend. To avoid |
304 |
< |
* long-term build-up of spares, the oldest spare (see |
305 |
< |
* ForkJoinWorkerThread.suspendAsSpare) occasionally wakes up if |
306 |
< |
* not signalled and calls tryTrimSpare, which uses two different |
307 |
< |
* thresholds: Always killing if the number of spares is greater |
308 |
< |
* that 25% of total, and killing others only at a slower rate |
309 |
< |
* (UNUSED_SPARE_TRIM_RATE_NANOS). |
284 |
> |
* 5. Managing suspension of extra workers. When a worker notices |
285 |
> |
* (usually upon timeout of a wait()) that there are too few |
286 |
> |
* running threads, we may create a new thread to maintain |
287 |
> |
* parallelism level, or at least avoid starvation. Usually, extra |
288 |
> |
* threads are needed for only very short periods, yet join |
289 |
> |
* dependencies are such that we sometimes need them in |
290 |
> |
* bursts. Rather than create new threads each time this happens, |
291 |
> |
* we suspend no-longer-needed extra ones as "spares". For most |
292 |
> |
* purposes, we don't distinguish "extra" spare threads from |
293 |
> |
* normal "core" threads: On each call to preStep (the only point |
294 |
> |
* at which we can do this) a worker checks to see if there are |
295 |
> |
* now too many running workers, and if so, suspends itself. |
296 |
> |
* Method helpMaintainParallelism looks for suspended threads to |
297 |
> |
* resume before considering creating a new replacement. The |
298 |
> |
* spares themselves are encoded on another variant of a Treiber |
299 |
> |
* Stack, headed at field "spareWaiters". Note that the use of |
300 |
> |
* spares is intrinsically racy. One thread may become a spare at |
301 |
> |
* about the same time as another is needlessly being created. We |
302 |
> |
* counteract this and related slop in part by requiring resumed |
303 |
> |
* spares to immediately recheck (in preStep) to see whether they |
304 |
> |
* they should re-suspend. |
305 |
> |
* |
306 |
> |
* 6. Killing off unneeded workers. A timeout mechanism is used to |
307 |
> |
* shed unused workers: The oldest (first) event queue waiter uses |
308 |
> |
* a timed rather than hard wait. When this wait times out without |
309 |
> |
* a normal wakeup, it tries to shutdown any one (for convenience |
310 |
> |
* the newest) other spare or event waiter via |
311 |
> |
* tryShutdownUnusedWorker. This eventually reduces the number of |
312 |
> |
* worker threads to a minimum of one after a long enough period |
313 |
> |
* without use. |
314 |
|
* |
315 |
< |
* 6. Deciding when to create new workers. The main dynamic |
315 |
> |
* 7. Deciding when to create new workers. The main dynamic |
316 |
|
* control in this class is deciding when to create extra threads |
317 |
|
* in method helpMaintainParallelism. We would like to keep |
318 |
|
* exactly #parallelism threads running, which is an impossble |
323 |
|
* compilation, and wake-up lags. These transients are extremely |
324 |
|
* common -- we are normally trying to fully saturate the CPUs on |
325 |
|
* a machine, so almost any activity other than running tasks |
326 |
< |
* impedes accuracy. Our main defense is to allow some slack in |
327 |
< |
* creation thresholds, using rules that reflect the fact that the |
328 |
< |
* more threads we have running, the more likely that we are |
329 |
< |
* underestimating the number running threads. The rules also |
330 |
< |
* better cope with the fact that some of the methods in this |
331 |
< |
* class tend to never become compiled (but are interpreted), so |
332 |
< |
* some components of the entire set of controls might execute 100 |
333 |
< |
* times faster than others. And similarly for cases where the |
334 |
< |
* apparent lack of work is just due to GC stalls and other |
335 |
< |
* transient system activity. |
326 |
> |
* impedes accuracy. Our main defense is to allow parallelism to |
327 |
> |
* lapse for a while during joins, and use a timeout to see if, |
328 |
> |
* after the resulting settling, there is still a need for |
329 |
> |
* additional workers. This also better copes with the fact that |
330 |
> |
* some of the methods in this class tend to never become compiled |
331 |
> |
* (but are interpreted), so some components of the entire set of |
332 |
> |
* controls might execute 100 times faster than others. And |
333 |
> |
* similarly for cases where the apparent lack of work is just due |
334 |
> |
* to GC stalls and other transient system activity. |
335 |
|
* |
336 |
|
* Beware that there is a lot of representation-level coupling |
337 |
|
* among classes ForkJoinPool, ForkJoinWorkerThread, and |
418 |
|
new AtomicInteger(); |
419 |
|
|
420 |
|
/** |
421 |
+ |
* The time to block in a join (see awaitJoin) before checking if |
422 |
+ |
* a new worker should be (re)started to maintain parallelism |
423 |
+ |
* level. The value should be short enough to maintain gloabal |
424 |
+ |
* responsiveness and progress but long enough to avoid |
425 |
+ |
* 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. |
428 |
+ |
*/ |
429 |
+ |
private static final long JOIN_TIMEOUT_MILLIS = 250L; // 4 per second |
430 |
+ |
|
431 |
+ |
/** |
432 |
+ |
* The wakeup interval (in nanoseconds) for the oldest worker |
433 |
+ |
* worker waiting for an event invokes tryShutdownUnusedWorker to shrink |
434 |
+ |
* the number of workers. The exact value does not matter too |
435 |
+ |
* much, but should be long enough to slowly release resources |
436 |
+ |
* during long periods without use without disrupting normal use. |
437 |
+ |
*/ |
438 |
+ |
private static final long SHRINK_RATE_NANOS = |
439 |
+ |
30L * 1000L * 1000L * 1000L; // 2 per minute |
440 |
+ |
|
441 |
+ |
/** |
442 |
|
* Absolute bound for parallelism level. Twice this number plus |
443 |
|
* one (i.e., 0xfff) must fit into a 16bit field to enable |
444 |
|
* word-packing for some counts and indices. |
483 |
|
private volatile long stealCount; |
484 |
|
|
485 |
|
/** |
466 |
– |
* The last nanoTime that a spare thread was trimmed |
467 |
– |
*/ |
468 |
– |
private volatile long trimTime; |
469 |
– |
|
470 |
– |
/** |
471 |
– |
* The rate at which to trim unused spares |
472 |
– |
*/ |
473 |
– |
static final long UNUSED_SPARE_TRIM_RATE_NANOS = |
474 |
– |
1000L * 1000L * 1000L; // 1 sec |
475 |
– |
|
476 |
– |
/** |
486 |
|
* 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 |
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. |
530 |
|
*/ |
531 |
< |
private volatile int runState; |
531 |
> |
volatile int runState; |
532 |
|
|
533 |
|
// Note: The order among run level values matters. |
534 |
|
private static final int RUNLEVEL_SHIFT = 16; |
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; |
526 |
– |
private static final int ONE_ACTIVE = 1; // active update delta |
539 |
|
|
540 |
|
/** |
541 |
|
* Holds number of total (i.e., created and not yet terminated) |
576 |
|
*/ |
577 |
|
private final int poolNumber; |
578 |
|
|
579 |
< |
|
580 |
< |
// Utilities for CASing fields. Note that several of these |
569 |
< |
// are manually inlined by callers |
579 |
> |
// Utilities for CASing fields. Note that most of these |
580 |
> |
// are usually manually inlined by callers |
581 |
|
|
582 |
|
/** |
583 |
|
* Increments running count part of workerCounts |
610 |
|
private void decrementWorkerCounts(int dr, int dt) { |
611 |
|
for (;;) { |
612 |
|
int wc = workerCounts; |
602 |
– |
if (wc == 0 && (runState & TERMINATED) != 0) |
603 |
– |
return; // lagging termination on a backout |
613 |
|
if ((wc & RUNNING_COUNT_MASK) - dr < 0 || |
614 |
< |
(wc >>> TOTAL_COUNT_SHIFT) - dt < 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; |
623 |
|
} |
624 |
|
|
625 |
|
/** |
614 |
– |
* Increments event count |
615 |
– |
*/ |
616 |
– |
private void advanceEventCount() { |
617 |
– |
int c; |
618 |
– |
do {} while(!UNSAFE.compareAndSwapInt(this, eventCountOffset, |
619 |
– |
c = eventCount, c+1)); |
620 |
– |
} |
621 |
– |
|
622 |
– |
/** |
623 |
– |
* Tries incrementing active count; fails on contention. |
624 |
– |
* Called by workers before executing tasks. |
625 |
– |
* |
626 |
– |
* @return true on success |
627 |
– |
*/ |
628 |
– |
final boolean tryIncrementActiveCount() { |
629 |
– |
int c; |
630 |
– |
return UNSAFE.compareAndSwapInt(this, runStateOffset, |
631 |
– |
c = runState, c + ONE_ACTIVE); |
632 |
– |
} |
633 |
– |
|
634 |
– |
/** |
626 |
|
* Tries decrementing active count; fails on contention. |
627 |
|
* Called when workers cannot find tasks to run. |
628 |
|
*/ |
629 |
|
final boolean tryDecrementActiveCount() { |
630 |
|
int c; |
631 |
|
return UNSAFE.compareAndSwapInt(this, runStateOffset, |
632 |
< |
c = runState, c - ONE_ACTIVE); |
632 |
> |
c = runState, c - 1); |
633 |
|
} |
634 |
|
|
635 |
|
/** |
690 |
|
} |
691 |
|
} |
692 |
|
|
702 |
– |
// adding and removing workers |
703 |
– |
|
704 |
– |
/** |
705 |
– |
* Tries to create and add new worker. Assumes that worker counts |
706 |
– |
* are already updated to accommodate the worker, so adjusts on |
707 |
– |
* failure. |
708 |
– |
*/ |
709 |
– |
private void addWorker() { |
710 |
– |
ForkJoinWorkerThread w = null; |
711 |
– |
try { |
712 |
– |
w = factory.newThread(this); |
713 |
– |
} finally { // Adjust on either null or exceptional factory return |
714 |
– |
if (w == null) { |
715 |
– |
decrementWorkerCounts(ONE_RUNNING, ONE_TOTAL); |
716 |
– |
tryTerminate(false); // in case of failure during shutdown |
717 |
– |
} |
718 |
– |
} |
719 |
– |
if (w != null) |
720 |
– |
w.start(recordWorker(w), ueh); |
721 |
– |
} |
722 |
– |
|
693 |
|
/** |
694 |
|
* Final callback from terminating worker. Removes record of |
695 |
|
* worker from array, and adjusts counts. If pool is shutting |
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. |
714 |
< |
* |
745 |
< |
* @param signalling true if caller is a signalling worker so can |
746 |
< |
* exit upon (conservatively) detected contention by other threads |
747 |
< |
* who will continue to release |
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(boolean signalling) { |
716 |
> |
private void releaseEventWaiters() { |
717 |
|
ForkJoinWorkerThread[] ws = workers; |
718 |
|
int n = ws.length; |
719 |
< |
long h; // head of stack |
720 |
< |
ForkJoinWorkerThread w; int id, ec; |
721 |
< |
while ((id = ((int)((h = eventWaiters) & WAITER_ID_MASK)) - 1) >= 0 && |
722 |
< |
(int)(h >>> EVENT_COUNT_SHIFT) != (ec = eventCount) && |
719 |
> |
long h = eventWaiters; |
720 |
> |
int ec = eventCount; |
721 |
> |
boolean releasedOne = false; |
722 |
> |
ForkJoinWorkerThread w; int id; |
723 |
> |
while ((id = ((int)(h & WAITER_ID_MASK)) - 1) >= 0 && |
724 |
> |
(int)(h >>> EVENT_COUNT_SHIFT) != ec && |
725 |
|
id < n && (w = ws[id]) != null) { |
726 |
|
if (UNSAFE.compareAndSwapLong(this, eventWaitersOffset, |
727 |
< |
h, h = w.nextWaiter)) |
727 |
> |
h, w.nextWaiter)) { |
728 |
|
LockSupport.unpark(w); |
729 |
< |
if (signalling && (eventCount != ec || eventWaiters != h)) |
729 |
> |
if (releasedOne) // exit on second release |
730 |
> |
break; |
731 |
> |
releasedOne = true; |
732 |
> |
} |
733 |
> |
if (eventCount != ec) |
734 |
|
break; |
735 |
+ |
h = eventWaiters; |
736 |
|
} |
737 |
|
} |
738 |
|
|
744 |
|
int c; // try to increment event count -- CAS failure OK |
745 |
|
UNSAFE.compareAndSwapInt(this, eventCountOffset, c = eventCount, c+1); |
746 |
|
if (eventWaiters != 0L) |
747 |
< |
releaseEventWaiters(true); |
747 |
> |
releaseEventWaiters(); |
748 |
|
} |
749 |
|
|
750 |
|
/** |
751 |
< |
* Blocks worker until terminating or event count |
752 |
< |
* advances from last value held by worker |
751 |
> |
* Adds the given worker to event queue and blocks until |
752 |
> |
* terminating or event count advances from the given value |
753 |
|
* |
754 |
|
* @param w the calling worker thread |
755 |
+ |
* @param ec the count |
756 |
|
*/ |
757 |
< |
private void eventSync(ForkJoinWorkerThread w) { |
758 |
< |
int wec = w.lastEventCount; |
784 |
< |
long nh = (((long)wec) << EVENT_COUNT_SHIFT) | ((long)(w.poolIndex+1)); |
757 |
> |
private void eventSync(ForkJoinWorkerThread w, int ec) { |
758 |
> |
long nh = (((long)ec) << EVENT_COUNT_SHIFT) | ((long)(w.poolIndex+1)); |
759 |
|
long h; |
760 |
|
while ((runState < SHUTDOWN || !tryTerminate(false)) && |
761 |
< |
((h = eventWaiters) == 0L || |
762 |
< |
(int)(h >>> EVENT_COUNT_SHIFT) == wec) && |
763 |
< |
eventCount == wec) { |
761 |
> |
(((int)((h = eventWaiters) & WAITER_ID_MASK)) == 0 || |
762 |
> |
(int)(h >>> EVENT_COUNT_SHIFT) == ec) && |
763 |
> |
eventCount == ec) { |
764 |
|
if (UNSAFE.compareAndSwapLong(this, eventWaitersOffset, |
765 |
|
w.nextWaiter = h, nh)) { |
766 |
< |
while (runState < TERMINATING && eventCount == wec) { |
767 |
< |
if (!tryAccumulateStealCount(w)) // transfer while idle |
768 |
< |
continue; |
769 |
< |
Thread.interrupted(); // clear/ignore interrupt |
770 |
< |
if (eventCount != wec) |
771 |
< |
break; |
766 |
> |
awaitEvent(w, ec); |
767 |
> |
break; |
768 |
> |
} |
769 |
> |
} |
770 |
> |
} |
771 |
> |
|
772 |
> |
/** |
773 |
> |
* Blocks the given worker (that has already been entered as an |
774 |
> |
* event waiter) until terminating or event count advances from |
775 |
> |
* the given value. The oldest (first) waiter uses a timed wait to |
776 |
> |
* occasionally one-by-one shrink the number of workers (to a |
777 |
> |
* minimum of one) if the pool has not been used for extended |
778 |
> |
* periods. |
779 |
> |
* |
780 |
> |
* @param w the calling worker thread |
781 |
> |
* @param ec the count |
782 |
> |
*/ |
783 |
> |
private void awaitEvent(ForkJoinWorkerThread w, int ec) { |
784 |
> |
while (eventCount == ec) { |
785 |
> |
if (tryAccumulateStealCount(w)) { // transfer while idle |
786 |
> |
boolean untimed = (w.nextWaiter != 0L || |
787 |
> |
(workerCounts & RUNNING_COUNT_MASK) <= 1); |
788 |
> |
long startTime = untimed? 0 : System.nanoTime(); |
789 |
> |
Thread.interrupted(); // clear/ignore interrupt |
790 |
> |
if (eventCount != ec || w.runState != 0 || |
791 |
> |
runState >= TERMINATING) // recheck after clear |
792 |
> |
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); |
802 |
|
} |
800 |
– |
break; |
803 |
|
} |
804 |
|
} |
803 |
– |
w.lastEventCount = eventCount; |
805 |
|
} |
806 |
|
|
807 |
< |
// Maintaining spares |
807 |
> |
// Maintaining parallelism |
808 |
|
|
809 |
|
/** |
810 |
|
* Pushes worker onto the spare stack |
811 |
|
*/ |
812 |
|
final void pushSpare(ForkJoinWorkerThread w) { |
813 |
< |
int ns = (++w.spareCount << SPARE_COUNT_SHIFT) | (w.poolIndex+1); |
813 |
> |
int ns = (++w.spareCount << SPARE_COUNT_SHIFT) | (w.poolIndex + 1); |
814 |
|
do {} while (!UNSAFE.compareAndSwapInt(this, spareWaitersOffset, |
815 |
|
w.nextSpare = spareWaiters,ns)); |
816 |
|
} |
817 |
|
|
818 |
|
/** |
819 |
< |
* Tries (once) to resume a spare if running count is less than |
820 |
< |
* target parallelism. Fails on contention or stale workers. |
819 |
> |
* Tries (once) to resume a spare if the number of running |
820 |
> |
* threads is less than target. |
821 |
|
*/ |
822 |
|
private void tryResumeSpare() { |
823 |
|
int sw, id; |
824 |
+ |
ForkJoinWorkerThread[] ws = workers; |
825 |
+ |
int n = ws.length; |
826 |
|
ForkJoinWorkerThread w; |
827 |
< |
ForkJoinWorkerThread[] ws; |
828 |
< |
if ((id = ((sw = spareWaiters) & SPARE_ID_MASK) - 1) >= 0 && |
829 |
< |
id < (ws = workers).length && (w = ws[id]) != null && |
827 |
> |
if ((sw = spareWaiters) != 0 && |
828 |
> |
(id = (sw & SPARE_ID_MASK) - 1) >= 0 && |
829 |
> |
id < n && (w = ws[id]) != null && |
830 |
|
(workerCounts & RUNNING_COUNT_MASK) < parallelism && |
828 |
– |
eventWaiters == 0L && |
831 |
|
spareWaiters == sw && |
832 |
|
UNSAFE.compareAndSwapInt(this, spareWaitersOffset, |
833 |
< |
sw, w.nextSpare) && |
834 |
< |
w.tryUnsuspend()) { |
835 |
< |
int c; // try increment; if contended, finish after unpark |
836 |
< |
boolean inc = UNSAFE.compareAndSwapInt(this, workerCountsOffset, |
837 |
< |
c = workerCounts, |
838 |
< |
c + ONE_RUNNING); |
839 |
< |
LockSupport.unpark(w); |
840 |
< |
if (!inc) { |
841 |
< |
do {} while(!UNSAFE.compareAndSwapInt(this, workerCountsOffset, |
840 |
< |
c = workerCounts, |
841 |
< |
c + ONE_RUNNING)); |
842 |
< |
} |
833 |
> |
sw, w.nextSpare)) { |
834 |
> |
int c; // increment running count before resume |
835 |
> |
do {} while(!UNSAFE.compareAndSwapInt |
836 |
> |
(this, workerCountsOffset, |
837 |
> |
c = workerCounts, c + ONE_RUNNING)); |
838 |
> |
if (w.tryUnsuspend()) |
839 |
> |
LockSupport.unpark(w); |
840 |
> |
else // back out if w was shutdown |
841 |
> |
decrementWorkerCounts(ONE_RUNNING, 0); |
842 |
|
} |
843 |
|
} |
844 |
|
|
845 |
|
/** |
846 |
< |
* Callback from oldest spare occasionally waking up. Tries |
847 |
< |
* (once) to shutdown a spare if more than 25% spare overage, or |
848 |
< |
* if UNUSED_SPARE_TRIM_RATE_NANOS have elapsed and there are at |
849 |
< |
* least #parallelism running threads. Note that we don't need CAS |
850 |
< |
* or locks here because the method is called only from the oldest |
851 |
< |
* suspended spare occasionally waking (and even misfires are OK). |
852 |
< |
* |
854 |
< |
* @param now the wake up nanoTime of caller |
855 |
< |
*/ |
856 |
< |
final void tryTrimSpare(long now) { |
857 |
< |
long lastTrim = trimTime; |
858 |
< |
trimTime = now; |
859 |
< |
helpMaintainParallelism(); // first, help wake up any needed spares |
860 |
< |
int sw, id; |
861 |
< |
ForkJoinWorkerThread w; |
862 |
< |
ForkJoinWorkerThread[] ws; |
846 |
> |
* Tries to increase the number of running workers if below target |
847 |
> |
* parallelism: If a spare exists tries to resume it via |
848 |
> |
* tryResumeSpare. Otherwise, if not enough total workers or all |
849 |
> |
* existing workers are busy, adds a new worker. In all casses also |
850 |
> |
* helps wake up releasable workers waiting for work. |
851 |
> |
*/ |
852 |
> |
private void helpMaintainParallelism() { |
853 |
|
int pc = parallelism; |
854 |
< |
int wc = workerCounts; |
855 |
< |
if ((wc & RUNNING_COUNT_MASK) >= pc && |
856 |
< |
(((wc >>> TOTAL_COUNT_SHIFT) - pc) > (pc >>> 2) + 1 ||// approx 25% |
857 |
< |
now - lastTrim >= UNUSED_SPARE_TRIM_RATE_NANOS) && |
858 |
< |
(id = ((sw = spareWaiters) & SPARE_ID_MASK) - 1) >= 0 && |
859 |
< |
id < (ws = workers).length && (w = ws[id]) != null && |
860 |
< |
UNSAFE.compareAndSwapInt(this, spareWaitersOffset, |
861 |
< |
sw, w.nextSpare)) |
862 |
< |
w.shutdown(false); |
854 |
> |
int wc, rs, tc; |
855 |
> |
while (((wc = workerCounts) & RUNNING_COUNT_MASK) < pc && |
856 |
> |
(rs = runState) < TERMINATING) { |
857 |
> |
if (spareWaiters != 0) |
858 |
> |
tryResumeSpare(); |
859 |
> |
else if ((tc = wc >>> TOTAL_COUNT_SHIFT) >= MAX_WORKERS || |
860 |
> |
(tc >= pc && (rs & ACTIVE_COUNT_MASK) != tc)) |
861 |
> |
break; // enough total |
862 |
> |
else if (runState == rs && workerCounts == wc && |
863 |
> |
UNSAFE.compareAndSwapInt(this, workerCountsOffset, wc, |
864 |
> |
wc + (ONE_RUNNING|ONE_TOTAL))) { |
865 |
> |
ForkJoinWorkerThread w = null; |
866 |
> |
try { |
867 |
> |
w = factory.newThread(this); |
868 |
> |
} finally { // adjust on null or exceptional factory return |
869 |
> |
if (w == null) { |
870 |
> |
decrementWorkerCounts(ONE_RUNNING, ONE_TOTAL); |
871 |
> |
tryTerminate(false); // handle failure during shutdown |
872 |
> |
} |
873 |
> |
} |
874 |
> |
if (w == null) |
875 |
> |
break; |
876 |
> |
w.start(recordWorker(w), ueh); |
877 |
> |
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 |
882 |
> |
} |
883 |
> |
} |
884 |
> |
} |
885 |
> |
if (eventWaiters != 0L) |
886 |
> |
releaseEventWaiters(); |
887 |
|
} |
888 |
|
|
889 |
|
/** |
890 |
< |
* Does at most one of: |
891 |
< |
* |
892 |
< |
* 1. Help wake up existing workers waiting for work via |
893 |
< |
* releaseEventWaiters. (If any exist, then it probably doesn't |
894 |
< |
* matter right now if under target parallelism level.) |
895 |
< |
* |
896 |
< |
* 2. If below parallelism level and a spare exists, try (once) |
883 |
< |
* to resume it via tryResumeSpare. |
890 |
> |
* 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 |
< |
* 3. If neither of the above, tries (once) to add a new |
899 |
< |
* worker if either there are not enough total, or if all |
887 |
< |
* existing workers are busy, there are either no running |
888 |
< |
* workers or the deficit is at least twice the surplus. |
898 |
> |
* @param ec the event count waited on by caller (to abort |
899 |
> |
* attempt if count has since changed). |
900 |
|
*/ |
901 |
< |
private void helpMaintainParallelism() { |
902 |
< |
// uglified to work better when not compiled |
903 |
< |
int pc, wc, rc, tc, rs; long h; |
904 |
< |
if ((h = eventWaiters) != 0L) { |
905 |
< |
if ((int)(h >>> EVENT_COUNT_SHIFT) != eventCount) |
906 |
< |
releaseEventWaiters(false); // avoid useless call |
907 |
< |
} |
908 |
< |
else if ((pc = parallelism) > |
909 |
< |
(rc = ((wc = workerCounts) & RUNNING_COUNT_MASK))) { |
910 |
< |
if (spareWaiters != 0) |
911 |
< |
tryResumeSpare(); |
912 |
< |
else if ((rs = runState) < TERMINATING && |
913 |
< |
((tc = wc >>> TOTAL_COUNT_SHIFT) < pc || |
914 |
< |
(tc == (rs & ACTIVE_COUNT_MASK) && // all busy |
915 |
< |
(rc == 0 || // must add |
916 |
< |
rc < pc - ((tc - pc) << 1)) && // within slack |
917 |
< |
tc < MAX_WORKERS && runState == rs)) && // recheck busy |
918 |
< |
workerCounts == wc && |
919 |
< |
UNSAFE.compareAndSwapInt(this, workerCountsOffset, wc, |
920 |
< |
wc + (ONE_RUNNING|ONE_TOTAL))) |
921 |
< |
addWorker(); |
901 |
> |
private void tryShutdownUnusedWorker(int ec) { |
902 |
> |
if (runState == 0 && eventCount == ec) { // only trigger if all idle |
903 |
> |
ForkJoinWorkerThread[] ws = workers; |
904 |
> |
int n = ws.length; |
905 |
> |
ForkJoinWorkerThread w = null; |
906 |
> |
boolean shutdown = false; |
907 |
> |
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 |
930 |
|
} |
931 |
|
|
932 |
|
/** |
933 |
|
* Callback from workers invoked upon each top-level action (i.e., |
934 |
< |
* stealing a task or taking a submission and running |
935 |
< |
* it). Performs one or more of the following: |
918 |
< |
* |
919 |
< |
* 1. If the worker cannot find work (misses > 0), updates its |
920 |
< |
* active status to inactive and updates activeCount unless |
921 |
< |
* this is the first miss and there is contention, in which |
922 |
< |
* case it may try again (either in this or a subsequent |
923 |
< |
* call). |
924 |
< |
* |
925 |
< |
* 2. If there are at least 2 misses, awaits the next task event |
926 |
< |
* via eventSync |
927 |
< |
* |
928 |
< |
* 3. If there are too many running threads, suspends this worker |
929 |
< |
* (first forcing inactivation if necessary). If it is not |
930 |
< |
* needed, it may be killed while suspended via |
931 |
< |
* tryTrimSpare. Otherwise, upon resume it rechecks to make |
932 |
< |
* sure that it is still needed. |
934 |
> |
* stealing a task or taking a submission and running it). |
935 |
> |
* Performs one or more of the following: |
936 |
|
* |
937 |
< |
* 4. Helps release and/or reactivate other workers via |
938 |
< |
* helpMaintainParallelism |
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, |
955 |
|
* |
956 |
|
* @param w the worker |
957 |
< |
* @param misses the number of scans by caller failing to find work |
939 |
< |
* (saturating at 2 just to avoid wraparound) |
957 |
> |
* @param ran true if worker ran a task since last call to this method |
958 |
|
*/ |
959 |
< |
final void preStep(ForkJoinWorkerThread w, int misses) { |
959 |
> |
final void preStep(ForkJoinWorkerThread w, boolean ran) { |
960 |
> |
int wec = w.lastEventCount; |
961 |
|
boolean active = w.active; |
962 |
+ |
boolean inactivate = false; |
963 |
|
int pc = parallelism; |
964 |
< |
for (;;) { |
964 |
> |
int rs; |
965 |
> |
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 |
< |
int rc = wc & RUNNING_COUNT_MASK; |
971 |
< |
if (active && (misses > 0 || rc > pc)) { |
972 |
< |
int rs; // try inactivate |
949 |
< |
if (UNSAFE.compareAndSwapInt(this, runStateOffset, |
950 |
< |
rs = runState, rs - ONE_ACTIVE)) |
951 |
< |
active = w.active = false; |
952 |
< |
else if (misses > 1 || rc > pc || |
953 |
< |
(rs & ACTIVE_COUNT_MASK) >= pc) |
954 |
< |
continue; // force inactivate |
955 |
< |
} |
956 |
< |
if (misses > 1) { |
957 |
< |
misses = 0; // don't re-sync |
958 |
< |
eventSync(w); // continue loop to recheck rc |
959 |
< |
} |
960 |
< |
else if (rc > pc) { |
961 |
< |
if (workerCounts == wc && // try to suspend as spare |
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()) // false if killed |
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 |
990 |
|
} |
991 |
< |
else { |
968 |
< |
if (rc < pc || eventWaiters != 0L) |
969 |
< |
helpMaintainParallelism(); |
991 |
> |
else |
992 |
|
break; |
971 |
– |
} |
993 |
|
} |
994 |
|
} |
995 |
|
|
996 |
|
/** |
997 |
|
* Helps and/or blocks awaiting join of the given task. |
998 |
< |
* Alternates between helpJoinTask() and helpMaintainParallelism() |
978 |
< |
* as many times as there is a deficit in running count (or longer |
979 |
< |
* if running count would become zero), then blocks if task still |
980 |
< |
* not done. |
998 |
> |
* See above for explanation. |
999 |
|
* |
1000 |
|
* @param joinMe the task to join |
1001 |
+ |
* @param worker the current worker thread |
1002 |
|
*/ |
1003 |
|
final void awaitJoin(ForkJoinTask<?> joinMe, ForkJoinWorkerThread worker) { |
1004 |
< |
int threshold = parallelism; // descend blocking thresholds |
1004 |
> |
int retries = 2 + (parallelism >> 2); // #helpJoins before blocking |
1005 |
|
while (joinMe.status >= 0) { |
1006 |
< |
boolean block; int wc; |
1006 |
> |
int wc; |
1007 |
|
worker.helpJoinTask(joinMe); |
1008 |
|
if (joinMe.status < 0) |
1009 |
|
break; |
1010 |
< |
if (((wc = workerCounts) & RUNNING_COUNT_MASK) <= threshold) { |
1011 |
< |
if (threshold > 0) |
1012 |
< |
--threshold; |
1013 |
< |
else |
1014 |
< |
advanceEventCount(); // force release |
1015 |
< |
block = false; |
1016 |
< |
} |
1017 |
< |
else |
1018 |
< |
block = UNSAFE.compareAndSwapInt(this, workerCountsOffset, |
1019 |
< |
wc, wc - ONE_RUNNING); |
1020 |
< |
helpMaintainParallelism(); |
1021 |
< |
if (block) { |
1022 |
< |
int c; |
1023 |
< |
joinMe.internalAwaitDone(); |
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 |
< |
break; |
1028 |
> |
if (stat < 0) |
1029 |
> |
break; // else restart |
1030 |
|
} |
1031 |
|
} |
1032 |
|
} |
1033 |
|
|
1034 |
|
/** |
1035 |
< |
* Same idea as awaitJoin, but no helping |
1035 |
> |
* Same idea as awaitJoin, but no helping, retries, or timeouts. |
1036 |
|
*/ |
1037 |
|
final void awaitBlocker(ManagedBlocker blocker) |
1038 |
|
throws InterruptedException { |
1018 |
– |
int threshold = parallelism; |
1039 |
|
while (!blocker.isReleasable()) { |
1040 |
< |
boolean block; int wc; |
1041 |
< |
if (((wc = workerCounts) & RUNNING_COUNT_MASK) <= threshold) { |
1042 |
< |
if (threshold > 0) |
1043 |
< |
--threshold; |
1024 |
< |
else |
1025 |
< |
advanceEventCount(); |
1026 |
< |
block = false; |
1027 |
< |
} |
1028 |
< |
else |
1029 |
< |
block = UNSAFE.compareAndSwapInt(this, workerCountsOffset, |
1030 |
< |
wc, wc - ONE_RUNNING); |
1031 |
< |
helpMaintainParallelism(); |
1032 |
< |
if (block) { |
1040 |
> |
int wc = workerCounts; |
1041 |
> |
if ((wc & RUNNING_COUNT_MASK) != 0 && |
1042 |
> |
UNSAFE.compareAndSwapInt(this, workerCountsOffset, |
1043 |
> |
wc, wc - ONE_RUNNING)) { |
1044 |
|
try { |
1045 |
< |
do {} while (!blocker.isReleasable() && !blocker.block()); |
1045 |
> |
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 |
> |
} |
1056 |
|
} finally { |
1057 |
|
int c; |
1058 |
|
do {} while (!UNSAFE.compareAndSwapInt |
1094 |
|
* Actions on transition to TERMINATING |
1095 |
|
* |
1096 |
|
* Runs up to four passes through workers: (0) shutting down each |
1097 |
< |
* quietly (without waking up if parked) to quickly spread |
1098 |
< |
* notifications without unnecessary bouncing around event queues |
1099 |
< |
* etc (1) wake up and help cancel tasks (2) interrupt (3) mop up |
1100 |
< |
* races with interrupted workers |
1097 |
> |
* (without waking up if parked) to quickly spread notifications |
1098 |
> |
* without unnecessary bouncing around event queues etc (1) wake |
1099 |
> |
* up and help cancel tasks (2) interrupt (3) mop up races with |
1100 |
> |
* interrupted workers |
1101 |
|
*/ |
1102 |
|
private void startTerminating() { |
1103 |
|
cancelSubmissions(); |
1104 |
|
for (int passes = 0; passes < 4 && workerCounts != 0; ++passes) { |
1105 |
< |
advanceEventCount(); |
1105 |
> |
int c; // advance event count |
1106 |
> |
UNSAFE.compareAndSwapInt(this, eventCountOffset, |
1107 |
> |
c = eventCount, c+1); |
1108 |
|
eventWaiters = 0L; // clobber lists |
1109 |
|
spareWaiters = 0; |
1110 |
|
ForkJoinWorkerThread[] ws = workers; |
1112 |
|
for (int i = 0; i < n; ++i) { |
1113 |
|
ForkJoinWorkerThread w = ws[i]; |
1114 |
|
if (w != null) { |
1115 |
< |
w.shutdown(true); |
1115 |
> |
w.shutdown(); |
1116 |
|
if (passes > 0 && !w.isTerminated()) { |
1117 |
|
w.cancelTasks(); |
1118 |
|
LockSupport.unpark(w); |
1260 |
|
this.workerLock = new ReentrantLock(); |
1261 |
|
this.termination = new Phaser(1); |
1262 |
|
this.poolNumber = poolNumberGenerator.incrementAndGet(); |
1240 |
– |
this.trimTime = System.nanoTime(); |
1263 |
|
} |
1264 |
|
|
1265 |
|
/** |
1267 |
|
* @param pc the initial parallelism level |
1268 |
|
*/ |
1269 |
|
private static int initialArraySizeFor(int pc) { |
1270 |
< |
// See Hackers Delight, sec 3.2. We know MAX_WORKERS < (1 >>> 16) |
1270 |
> |
// If possible, initially allocate enough space for one spare |
1271 |
|
int size = pc < MAX_WORKERS ? pc + 1 : MAX_WORKERS; |
1272 |
+ |
// See Hackers Delight, sec 3.2. We know MAX_WORKERS < (1 >>> 16) |
1273 |
|
size |= size >>> 1; |
1274 |
|
size |= size >>> 2; |
1275 |
|
size |= size >>> 4; |
1288 |
|
if (runState >= SHUTDOWN) |
1289 |
|
throw new RejectedExecutionException(); |
1290 |
|
submissionQueue.offer(task); |
1291 |
< |
advanceEventCount(); |
1292 |
< |
helpMaintainParallelism(); // start or wake up workers |
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 |
|
/** |
1297 |
|
* Performs the given task, returning its result upon completion. |
1274 |
– |
* If the caller is already engaged in a fork/join computation in |
1275 |
– |
* the current pool, this method is equivalent in effect to |
1276 |
– |
* {@link ForkJoinTask#invoke}. |
1298 |
|
* |
1299 |
|
* @param task the task |
1300 |
|
* @return the task's result |
1309 |
|
|
1310 |
|
/** |
1311 |
|
* Arranges for (asynchronous) execution of the given task. |
1291 |
– |
* If the caller is already engaged in a fork/join computation in |
1292 |
– |
* the current pool, this method is equivalent in effect to |
1293 |
– |
* {@link ForkJoinTask#fork}. |
1312 |
|
* |
1313 |
|
* @param task the task |
1314 |
|
* @throws NullPointerException if the task is null |
1337 |
|
|
1338 |
|
/** |
1339 |
|
* Submits a ForkJoinTask for execution. |
1322 |
– |
* If the caller is already engaged in a fork/join computation in |
1323 |
– |
* the current pool, this method is equivalent in effect to |
1324 |
– |
* {@link ForkJoinTask#fork}. |
1340 |
|
* |
1341 |
|
* @param task the task to submit |
1342 |
|
* @return the task |
1768 |
|
* QueueTaker(BlockingQueue<E> q) { this.queue = q; } |
1769 |
|
* public boolean block() throws InterruptedException { |
1770 |
|
* if (item == null) |
1771 |
< |
* item = queue.take |
1771 |
> |
* item = queue.take(); |
1772 |
|
* return true; |
1773 |
|
* } |
1774 |
|
* public boolean isReleasable() { |
1775 |
< |
* return item != null || (item = queue.poll) != null; |
1775 |
> |
* return item != null || (item = queue.poll()) != null; |
1776 |
|
* } |
1777 |
|
* public E getItem() { // call after pool.managedBlock completes |
1778 |
|
* return item; |