On Tue, 25 Feb 2025 19:42:01 GMT, Sunmisc Unsafe <d...@openjdk.org> wrote:
>> Is it possible to use getAndSet instead of cas-loop on #pend? >> >> final Task t = tail.getAndSet(task); >> t.next = task; >> >> but that would require a new head field to bypass, probably not worth the >> gamble if the footprint increases a lot > >> @sunmisc You are right that it would be nice if there were a way to >> efficiently use getAndSet here because a failed reference CAS hits slow >> paths that vary across GCs. But all of the ways I know to do this are much >> worse. > > After a few days of benchmarks, I realized that you would be absolutely > right. Although I thought if we separate the head (for deleting) and the tail > (for inserting) there would be less contention. > Even the fact that we can change the head (delete) only in one thread does > not help us from volatile, moreover, it became worse. > Perhaps I have made a mistake somewhere in the implementation @sunmisc Thanks for independently trying alternatives. We both had reasons to suspect that other mechanics might work out as well or better, but none seem to. ------------- PR Comment: https://git.openjdk.org/jdk/pull/23702#issuecomment-2683456519
