On Fri, 21 Jul 2023 10:55:19 GMT, Doug Lea <d...@openjdk.org> wrote: >> src/java.base/share/classes/java/util/concurrent/LinkedTransferQueue.java >> line 446: >> >>> 444: Thread.onSpinWait(); >>> 445: else >>> 446: LockSupport.parkNanos(ns); >> >> @DougLea If `ns` is sufficiently large, would it not make sense to use >> managed blocking in case the current thread is a FJWT as below? 🤔 > > It's a good point, but we don't normally do this. Added (L336): > * returns just barely too soon. As is the case in most j.u.c > * blocking support, untimed waits use ManagedBlockers when > * callers are ForkJoin threads, but timed waits use plain > * parkNanos, under the rationale that known-to-be transient > * blocking doesn't require compensation. (This decision should be > * revisited here and elsewhere to deal with very long timeouts.)
I should have mentioned that the tradeoffs include that using ManagedBlocking for timed waits here adds overhead: -- constructing of another object just to track the time, and duplicate checks of other parts of await(. Which requires choosing a threshold where it would be worthwhile. Which is a hard-to-win decision. ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/14317#discussion_r1270561315
