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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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* about the same time as another is needlessly being created. We |
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* counteract this and related slop in part by requiring resumed |
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* spares to immediately recheck (in preStep) to see whether they |
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* they should re-suspend. |
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* should re-suspend. |
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* |
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* 6. Killing off unneeded workers. A timeout mechanism is used to |
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* shed unused workers: The oldest (first) event queue waiter uses |
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* "while ((local = field) != 0)") which are usually the simplest |
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* way to ensure the required read orderings (which are sometimes |
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* critical). Also several occurrences of the unusual "do {} |
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* while(!cas...)" which is the simplest way to force an update of |
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* while (!cas...)" which is the simplest way to force an update of |
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* a CAS'ed variable. There are also other coding oddities that |
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* help some methods perform reasonably even when interpreted (not |
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* compiled), at the expense of some messy constructions that |
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/** |
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* The wakeup interval (in nanoseconds) for the oldest worker |
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* worker waiting for an event invokes tryShutdownUnusedWorker to shrink |
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* waiting for an event invokes tryShutdownUnusedWorker to shrink |
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* the number of workers. The exact value does not matter too |
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* much, but should be long enough to slowly release resources |
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* during long periods without use without disrupting normal use. |
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} |
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/** |
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* Nulls out record of worker in workers array |
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* Nulls out record of worker in workers array. |
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*/ |
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private void forgetWorker(ForkJoinWorkerThread w) { |
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int idx = w.poolIndex; |
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UNSAFE.compareAndSwapInt(this, spareWaitersOffset, |
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sw, w.nextSpare)) { |
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int c; // increment running count before resume |
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do {} while(!UNSAFE.compareAndSwapInt |
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(this, workerCountsOffset, |
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c = workerCounts, c + ONE_RUNNING)); |
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do {} while (!UNSAFE.compareAndSwapInt |
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(this, workerCountsOffset, |
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c = workerCounts, c + ONE_RUNNING)); |
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if (w.tryUnsuspend()) |
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LockSupport.unpark(w); |
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else // back out if w was shutdown |
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c = eventCount, c+1); |
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eventWaiters = 0L; // clobber lists |
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spareWaiters = 0; |
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ForkJoinWorkerThread[] ws = workers; |
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int n = ws.length; |
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for (int i = 0; i < n; ++i) { |
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ForkJoinWorkerThread w = ws[i]; |
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for (ForkJoinWorkerThread w : workers) { |
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if (w != null) { |
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w.shutdown(); |
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if (passes > 0 && !w.isTerminated()) { |
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} |
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/** |
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* Clear out and cancel submissions, ignoring exceptions |
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* Clears out and cancels submissions, ignoring exceptions. |
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*/ |
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private void cancelSubmissions() { |
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ForkJoinTask<?> task; |
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// misc support for ForkJoinWorkerThread |
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/** |
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* Returns pool number |
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* Returns pool number. |
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*/ |
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final int getPoolNumber() { |
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return poolNumber; |
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} |
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/** |
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* Tries to accumulates steal count from a worker, clearing |
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* the worker's value. |
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* Tries to accumulate steal count from a worker, clearing |
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* the worker's value if successful. |
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* |
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* @return true if worker steal count now zero |
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*/ |
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int pc = parallelism; // use parallelism, not rc |
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int ac = runState; // no mask -- artificially boosts during shutdown |
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// Use exact results for small values, saturate past 4 |
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return pc <= ac? 0 : pc >>> 1 <= ac? 1 : pc >>> 2 <= ac? 3 : pc >>> 3; |
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return ((pc <= ac) ? 0 : |
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(pc >>> 1 <= ac) ? 1 : |
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(pc >>> 2 <= ac) ? 3 : |
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pc >>> 3); |
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} |
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// Public and protected methods |
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*/ |
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public long getQueuedTaskCount() { |
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long count = 0; |
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ForkJoinWorkerThread[] ws = workers; |
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int n = ws.length; |
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for (int i = 0; i < n; ++i) { |
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ForkJoinWorkerThread w = ws[i]; |
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for (ForkJoinWorkerThread w : workers) |
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if (w != null) |
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count += w.getQueueSize(); |
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} |
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return count; |
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} |
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*/ |
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protected int drainTasksTo(Collection<? super ForkJoinTask<?>> c) { |
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int count = submissionQueue.drainTo(c); |
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ForkJoinWorkerThread[] ws = workers; |
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int n = ws.length; |
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for (int i = 0; i < n; ++i) { |
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ForkJoinWorkerThread w = ws[i]; |
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for (ForkJoinWorkerThread w : workers) |
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if (w != null) |
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count += w.drainTasksTo(c); |
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} |
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return count; |
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} |
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throws InterruptedException { |
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try { |
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return termination.awaitAdvanceInterruptibly(0, timeout, unit) > 0; |
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} catch(TimeoutException ex) { |
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} catch (TimeoutException ex) { |
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return false; |
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} |
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} |
