RFR: 8335480: Only deoptimize threads if needed when closing shared arena [v5]
Jorn Vernee
jvernee at openjdk.org
Tue Jul 16 15:12:15 UTC 2024
> 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 52.042 ± 0.630 us/op
> ConcurrentClose.conf...
Jorn Vernee has updated the pull request incrementally with one additional commit since the last revision:
clarify javadoc
-------------
Changes:
- all: https://git.openjdk.org/jdk/pull/20158/files
- new: https://git.openjdk.org/jdk/pull/20158/files/62849aa8..cd5f290e
Webrevs:
- full: https://webrevs.openjdk.org/?repo=jdk&pr=20158&range=04
- incr: https://webrevs.openjdk.org/?repo=jdk&pr=20158&range=03-04
Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 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
More information about the core-libs-dev
mailing list