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8292969: Bad Thread Utilization in ForkJoinPool

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Reviewed-by: shade, alanb
This commit is contained in:
Doug Lea 2022-09-27 10:50:18 +00:00
parent dd51f7e0b7
commit bc12e9553d
1 changed files with 6 additions and 5 deletions
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11
src/java.base/share/classes/java/util/concurrent/ForkJoinPool.java
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@ -1815,9 +1815,9 @@ public class ForkJoinPool extends AbstractExecutorService {
* returning source id or retry indicator. * returning source id or retry indicator.
* *
* @param w caller's WorkQueue * @param w caller's WorkQueue
* @param prevSrc the previous queue stolen from in current phase, or 0 * @param prevSrc the two previous queues (if nonzero) stolen from in current phase, packed as int
* @param r random seed * @param r random seed
* @return id of queue if taken, negative if none found, prevSrc for retry * @return the next prevSrc value to use, or negative if none found
*/ */
private int scan(WorkQueue w, int prevSrc, int r) { private int scan(WorkQueue w, int prevSrc, int r) {
WorkQueue[] qs = queues; WorkQueue[] qs = queues;
@ -1835,10 +1835,11 @@ public class ForkJoinPool extends AbstractExecutorService {
else if (t != null && WorkQueue.casSlotToNull(a, k, t)) { else if (t != null && WorkQueue.casSlotToNull(a, k, t)) {
q.base = nb; q.base = nb;
w.source = src; w.source = src;
if (prevSrc == 0 && q.base == nb && a[nk] != null) if (src + (src << SWIDTH) != prevSrc &&
signalWork(); // propagate q.base == nb && a[nk] != null)
signalWork(); // propagate at most twice/run
w.topLevelExec(t, q); w.topLevelExec(t, q);
return src; return src + (prevSrc << SWIDTH);
} }
else if (q.array != a || a[k] != null || a[nk] != null) else if (q.array != a || a[k] != null || a[nk] != null)
return prevSrc; // revisit return prevSrc; // revisit