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: - 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 52.042 ± 0.630 us/op ConcurrentClose.confinedAccess 32 avgt 10 25.517 ± 1.069 us/op ConcurrentClose.confinedAccess 1 avgt 10 12.398 ± 0.098 us/op (I manually added the `Threads` collumn btw) Testing: tier 1-4 ------------- Commit messages: - polish - slightly improve comment - tweak comment - improve benchmark parameters - cleanup - add benchmark - add note about lacking session oop at safepoint - Only deopt if necessary - refactor close handshake - Return before deoptimizing of target thread already has async exception Changes: https://git.openjdk.org/jdk/pull/20158/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20158&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8335480 Stats: 428 lines in 6 files changed: 339 ins; 19 del; 70 mod Patch: https://git.openjdk.org/jdk/pull/20158.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/20158/head:pull/20158 PR: https://git.openjdk.org/jdk/pull/20158
