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8080623: CPU overhead in FJ due to spinning in awaitWork

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Reviewed-by: chegar, dholmes
This commit is contained in:
Doug Lea 2015-05-20 14:50:57 +02:00
parent 216d24980d
commit 8654e36410
1 changed files with 9 additions and 6 deletions
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15
jdk/src/java.base/share/classes/java/util/concurrent/ForkJoinPool.java
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@ -1328,13 +1328,16 @@ public class ForkJoinPool extends AbstractExecutorService {
/**
* Number of times to spin-wait before blocking. The spins (in
* awaitRunStateLock and awaitWork) currently use randomized
* spins. If/when MWAIT-like intrinsics becomes available, they
* may allow quieter spinning. The value of SPINS must be a power
* of two, at least 4. The current value causes spinning for a
* small fraction of typical context-switch times, well worthwhile
* given the typical likelihoods that blocking is not necessary.
* spins. Currently set to zero to reduce CPU usage.
*
* If greater than zero the value of SPINS must be a power
* of two, at least 4. A value of 2048 causes spinning for a
* small fraction of typical context-switch times.
*
* If/when MWAIT-like intrinsics becomes available, they
* may allow quieter spinning.
*/
private static final int SPINS = 1 << 11;
private static final int SPINS = 0;
/**
* Increment for seed generators. See class ThreadLocal for