RFR: 8344831: [REDO] CDS: Parallel relocation
Aleksey Shipilev
shade at openjdk.org
Tue Nov 26 09:48:21 UTC 2024
This re-does [JDK-8341334](https://bugs.openjdk.org/browse/JDK-8341334), being mindful of failures reported in [JDK-8344583](https://bugs.openjdk.org/browse/JDK-8344583). See the original motivation in [JDK-8341334](https://bugs.openjdk.org/browse/JDK-8341334).
To simplify reviews, this PR contains the original commit (https://github.com/openjdk/jdk/commit/4218b882cd0a75f3159495ec2a57305ecfc8bf69), and amendments are stacked on top of it.
The common theme in all failures that we have seen is VM exiting when `ArchiveWorkers` (`AW`) are still actively waiting on related `Semaphores`. Since the `AW` were static, the destructors for `Semaphores` would run as part of `AW` destruction sequence, and what would make the active workers fail.
We resolve this trouble and strengthen the code with the following amendments:
1. `AW` is now a structured stack object. `AW` instances are not exposed statically, so even the abnormal VM termination would not break semaphores. The normal scoping rules would make sure `AW` is shutdown on all normal paths.
2. We move `AW` use mark to the only place it is currently used. This allows us to further insulate from `AW` problems if we flip the `AOTCacheParallelRelocation` flag back to `false` in the field.
3. `AW` is now a single-use object. Making it reusable proves to be fairly hard, especially when workers are lagging behind during the startup or wakeups. Quite a bit of that can be mitigated by smart shutdown protocol, but it requires more coordination, and extra pool work. Single use `AW` is significantly easier to reason about. We can re-instate reusability in/when we need it.
I will put the performance data in a separate commit.
Additional testing:
- [x] GHA
- [x] linux-x86_64-server-fastdebug, `runtime/cds`
- [x] linux-x86_64-server-fastdebug, `all`
- [x] macos-aarch64-server-fastdebug, `compiler/compilercontrol compiler/ciReplay runtime/CommandLine/` (100x, no failures)
-------------
Commit messages:
- Gross simplification: single-use ArchiveWorkers
- Actual REDO increment: amendments to fix failures
- Original JDK-8341334
Changes: https://git.openjdk.org/jdk/pull/22369/files
Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=22369&range=00
Issue: https://bugs.openjdk.org/browse/JDK-8344831
Stats: 313 lines in 5 files changed: 310 ins; 0 del; 3 mod
Patch: https://git.openjdk.org/jdk/pull/22369.diff
Fetch: git fetch https://git.openjdk.org/jdk.git pull/22369/head:pull/22369
PR: https://git.openjdk.org/jdk/pull/22369
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