RFR: 8344831: [REDO] CDS: Parallel relocation [v4]

[David Holmes]

On Wed, 27 Nov 2024 15:29:58 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> 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:
> 
>   Atomicity improvements

This seems okay, though I wonder if there is not a more well-established "smart ptr" style pattern for managing the lifecycle via a wrapper where last thread out does the delete?

Anyway clicking approve.

Thanks

src/hotspot/share/cds/archiveUtils.cpp line 492:

> 490:   }
> 491: 
> 492:   OrderAccess::fence();

What is the fence for?

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Marked as reviewed by dholmes (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/22369#pullrequestreview-2466223756
PR Review Comment: https://git.openjdk.org/jdk/pull/22369#discussion_r1861437133