On Fri, 12 Jul 2024 20:59:26 GMT, Jorn Vernee <jver...@openjdk.org> wrote:
>> This PR limits the number of cases in which we deoptimize frames when >> closing a shared Arena. The initial intent of this was to improve the >> performance of shared arena closure in cases where a lot of threads are >> accessing and closing shared arenas at the same time (see attached >> benchmark), but unfortunately even disabling deoptimization altogether does >> not have a great effect on that benchmark. >> >> Nevertheless, I think the extra logging/testing/benchmark code, and comments >> I've written, together with reducing the number of cases where we deoptimize >> (which makes it clearer exactly why we need to deoptimize in the first >> place), will be useful going forward. So, I've a create this PR out of them. >> >> In this PR: >> - Deoptimizing is now only done in cases where it's needed, instead of >> always. Which is in cases where we are not inside an `@Scoped` method, but >> are inside a compiled frame that has a scoped access somewhere inside of it. >> - I've separated the stack walking code (`for_scope_method`) from the code >> that checks for a reference to the arena being closed >> (`is_accessing_session`), and added logging code to the former. That also >> required changing vframe code to accept an `ouputStream*` rather than always >> printing to `tty`. >> - Added a new test (`TestConcurrentClose`), that tries to close many shared >> arenas at the same time, in order to stress that use case. >> - Added a new benchmark (`ConcurrentClose`), that stresses the cases where >> many threads are accessing and closing shared arenas. >> >> I've done several benchmark runs with different amounts of threads. The >> confined case stays much more consistent, while the shared cases balloons up >> in time spent quickly when there are more than 4 threads: >> >> >> Benchmark Threads Mode Cnt Score Error Units >> ConcurrentClose.sharedAccess 32 avgt 10 9017.397 ± 202.870 us/op >> ConcurrentClose.sharedAccess 24 avgt 10 5178.214 ± 164.922 us/op >> ConcurrentClose.sharedAccess 16 avgt 10 2224.420 ± 165.754 us/op >> ConcurrentClose.sharedAccess 8 avgt 10 593.828 ± 8.321 us/op >> ConcurrentClose.sharedAccess 7 avgt 10 470.700 ± 22.511 us/op >> ConcurrentClose.sharedAccess 6 avgt 10 386.697 ± 59.170 us/op >> ConcurrentClose.sharedAccess 5 avgt 10 291.157 ± 7.023 us/op >> ConcurrentClose.sharedAccess 4 avgt 10 209.178 ± 5.802 us/op >> ConcurrentClose.sharedAccess 1 avgt 10 ... > > Jorn Vernee has updated the pull request incrementally with one additional > commit since the last revision: > > track has_scoped_access for compiled methods @dougxc might want to have a look at Graal support for this one. ------------- PR Comment: https://git.openjdk.org/jdk/pull/20158#issuecomment-2226957995
