RFR: 8348402: PerfDataManager stalls shutdown for 1ms
Aleksey Shipilev
shade at openjdk.org
Fri Jan 24 09:33:58 UTC 2025
Found this when studying Leyden performance. [JDK-8049304](https://bugs.openjdk.org/browse/JDK-8049304) added 1ms sleep on destruction path to catch up with threads updating the counters.
I was not able to confidently prove the deletion race is benign. Even though `sleep` is not really a fix for that race either, I think it is safer to use GlobalCounter to coordinate deletions.
This improves startup (roundtrip) tests for the expected 1ms:
$ hyperfine -w 10 -r 100 ...
# Before
Benchmark 1: build/linux-x86_64-server-release/images/jdk/bin/java -XX:+UnlockExperimentalVMOptions -XX:+UseEpsilonGC -Xmx128m Hello
Time (mean ± σ): 20.0 ms ± 0.3 ms [User: 11.7 ms, System: 16.0 ms]
Range (min … max): 19.0 ms … 21.7 ms 1000 runs
# After
Benchmark 1: build/linux-x86_64-server-release/images/jdk/bin/java -XX:+UnlockExperimentalVMOptions -XX:+UseEpsilonGC -Xmx128m Hello
Time (mean ± σ): 19.0 ms ± 0.3 ms [User: 11.9 ms, System: 15.8 ms]
Range (min … max): 18.2 ms … 20.8 ms 1000 runs
Additional testing:
- [ ] Linux AArch64 server fastdebug, `all`
- [ ] Linux x86_64 server fastdebug, `all`
-------------
Commit messages:
- Fix minimal build
- Use GlobalCounter to coordinate deletions
Changes: https://git.openjdk.org/jdk/pull/23293/files
Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23293&range=00
Issue: https://bugs.openjdk.org/browse/JDK-8348402
Stats: 23 lines in 5 files changed: 7 ins; 2 del; 14 mod
Patch: https://git.openjdk.org/jdk/pull/23293.diff
Fetch: git fetch https://git.openjdk.org/jdk.git pull/23293/head:pull/23293
PR: https://git.openjdk.org/jdk/pull/23293
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