RFR: 8344831: [REDO] CDS: Parallel relocation [v3]
Aleksey Shipilev
shade at openjdk.org
Wed Nov 27 09:12:34 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)
Aleksey Shipilev has updated the pull request incrementally with one additional commit since the last revision:
We do not actually need to track finished workers
-------------
Changes:
- all: https://git.openjdk.org/jdk/pull/22369/files
- new: https://git.openjdk.org/jdk/pull/22369/files/0fedb425..49773f68
Webrevs:
- full: https://webrevs.openjdk.org/?repo=jdk&pr=22369&range=02
- incr: https://webrevs.openjdk.org/?repo=jdk&pr=22369&range=01-02
Stats: 8 lines in 2 files changed: 1 ins; 4 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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