RFA 8056248: Improve ForkJoin thread throttling

[Paul Sandoz]

Hi,

I would like to backport the improvements to the fork join framework from 9 to 8u40:

  http://mail.openjdk.java.net/pipermail/core-libs-dev/2014-August/028419.html

  https://bugs.openjdk.java.net/browse/JDK-8056248

  http://cr.openjdk.java.net/~psandoz/jdk9/JDK-8056248-fj-thread-throttling/webrev/

  http://hg.openjdk.java.net/jdk9/dev/jdk/rev/7af64e3e095d

The changeset (when shuffled) imports cleanly into jdk8u-dev/jdk. 

However, it also introduced a new system property ("java.util.concurrent.ForkJoinPool.common.maximumSpares"). I am not sure if we can add such a new feature to an 8u release, any advice? If that is not possible I suggest that reference to that property be removed from the JavaDoc, since that makes it easier to support further backports:

diff -r a6403166fc7f src/share/classes/java/util/concurrent/ForkJoinPool.java
--- a/src/share/classes/java/util/concurrent/ForkJoinPool.java	Fri Sep 05 10:54:28 2014 +0200
+++ b/src/share/classes/java/util/concurrent/ForkJoinPool.java	Fri Sep 05 11:26:49 2014 +0200
@@ -143,9 +143,6 @@
  * - the class name of a {@link ForkJoinWorkerThreadFactory}
  * <li>{@code java.util.concurrent.ForkJoinPool.common.exceptionHandler}
  * - the class name of a {@link UncaughtExceptionHandler}
- * <li>{@code java.util.concurrent.ForkJoinPool.common.maximumSpares}
- * - the maximum number of allowed extra threads to maintain target
- * parallelism (default 256).
  * </ul>
  * If a {@link SecurityManager} is present and no factory is
  * specified, then the default pool uses a factory supplying


Thanks,
Paul.