On Mon, 14 Oct 2024 20:58:43 GMT, Doug Lea <d...@openjdk.org> wrote:
> This addresses tendencies in previous update to increase fencing, scanning,
> and signalling that can increase contention, and slow down performance
> especially on ARM platforms. It also uses more ARM-friendly constructions to
> reduce overhead (leading to several changes that all of the same form),
src/java.base/share/classes/java/util/concurrent/ForkJoinPool.java line 305:
> 303: * * Slot k must be read with an acquiring read, which it must
> 304: * anyway to dereference and run the task if the (acquiring)
> 305: * CAS succeeds
Suggestion:
* CAS succeeds.
src/java.base/share/classes/java/util/concurrent/ForkJoinPool.java line 854:
> 852: * usages of ForkJoinTasks ignore interrupt status when executing
> 853: * or awaiting completion. Otherwise, reporting task results or
> 854: * exceptions is preferred to throwing InterruptedExeptions,
Suggestion:
* exceptions is preferred to throwing InterruptedExceptions,
src/java.base/share/classes/java/util/concurrent/ForkJoinPool.java line 1287:
> 1285: if (!internal)
> 1286: unlockPhase();
> 1287: if ((room == 0 || U.getReference(a, pk) == null) && pool !=
> null)
We used to look at `- 2` but now we look at `- 1`, perhaps that could account
for stalls?
src/java.base/share/classes/java/util/concurrent/ForkJoinPool.java line 1913:
> 1911: if (!all)
> 1912: break;
> 1913: }
Stylistically, it might be cleaner to do this:
Suggestion:
do {
WorkQueue[] qs; WorkQueue v; int sp, i;
if ((sp = (int)c) == 0 || (qs = queues) == null ||
qs.length <= (i = sp & SMASK) || (v = qs[i]) == null)
break;
if (c == (c = compareAndExchangeCtl(
c, ((UMASK & (c + RC_UNIT)) | (c & TC_MASK) |
(v.stackPred & LMASK))))) {
v.phase = sp;
if (v.parking != 0)
U.unpark(v.owner);
} while(all);
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/21507#discussion_r1803453194
PR Review Comment: https://git.openjdk.org/jdk/pull/21507#discussion_r1803452635
PR Review Comment: https://git.openjdk.org/jdk/pull/21507#discussion_r1803455326
PR Review Comment: https://git.openjdk.org/jdk/pull/21507#discussion_r1803451989
