From 8654e36410c788d9430eafa3b4f74d7ce16a56cd Mon Sep 17 00:00:00 2001 From: Doug Lea Date: Wed, 20 May 2015 14:50:57 +0200 Subject: [PATCH] 8080623: CPU overhead in FJ due to spinning in awaitWork Reviewed-by: chegar, dholmes --- .../java/util/concurrent/ForkJoinPool.java | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-) diff --git a/jdk/src/java.base/share/classes/java/util/concurrent/ForkJoinPool.java b/jdk/src/java.base/share/classes/java/util/concurrent/ForkJoinPool.java index 0029322cfc2..58f80866140 100644 --- a/jdk/src/java.base/share/classes/java/util/concurrent/ForkJoinPool.java +++ b/jdk/src/java.base/share/classes/java/util/concurrent/ForkJoinPool.java @@ -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