RFR: 8322732: ForkJoinPool may underutilize cores in async mode [v7]

[Doug Lea]

On Wed, 29 May 2024 13:26:10 GMT, Viktor Klang <vklang at openjdk.org> wrote:

>> Doug Lea has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains 41 additional commits since the last revision:
>> 
>>  - Merge branch 'openjdk:master' into JDK-8322732
>>  - Add test for utilization with interdependent tasks
>>  - Un-misplace onSpinWait call
>>  - Adjust control flow
>>  - Reduce memory stalls
>>  - Merge branch 'openjdk:master' into JDK-8322732
>>  - More performance tradoffs
>>  - Address review comments
>>  - Merge branch 'openjdk:master' into JDK-8322732
>>  - Repack some fields; adjust control flow
>>  - ... and 31 more: https://git.openjdk.org/jdk/compare/c056aa9c...cf5fe55c
>
> src/java.base/share/classes/java/util/concurrent/ForkJoinPool.java line 912:
> 
>> 910:      * enough to avoid resizing in most tree-structured tasks, but
>> 911:      * larger for external queues where both false-sharing problems
>> 912:      * and the need for resizing are more common..  (Maintenance note:
> 
> Suggestion:
> 
>      * and the need for resizing are more common.  (Maintenance note:

thanks, done.

> src/java.base/share/classes/java/util/concurrent/ForkJoinPool.java line 1857:
> 
>> 1855:                                        (LMASK & c)))));
>> 1856:         }
>> 1857:         if ((tryTerminate(false, false) & STOP) == 0 && w != null) {
> 
> Suggestion:
> 
>         if ((tryTerminate(false, false) & STOP) == 0L && w != null) {

yes.

> src/java.base/share/classes/java/util/concurrent/ForkJoinPool.java line 2061:
> 
>> 2059:                 w.stackPred = (int)pc;           // set ctl stack link
>> 2060:                 qc = (active & LMASK) | ((pc - RC_UNIT) & UMASK);
>> 2061:                 if (pc == (pc = compareAndExchangeCtl(pc, qc)))
> 
> If I'm reading this right you might want to add a comment :)
> 
> Suggestion:
> 
>                 if (pc == (pc = compareAndExchangeCtl(pc, qc))) // consistent

thanks, done.

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/19131#discussion_r1619023295
PR Review Comment: https://git.openjdk.org/jdk/pull/19131#discussion_r1619024417
PR Review Comment: https://git.openjdk.org/jdk/pull/19131#discussion_r1619025818