[jdk17u-dev] RFR: 8310031: Parallel: Implement better work distribution for large object arrays in old gen [v4]

[Richard Reingruber]

On Thu, 7 Mar 2024 12:28:26 GMT, Richard Reingruber <rrich at openjdk.org> wrote:

>> I would like to backport this as a performance bug fix.
>> 
>> We received bug reports from users which have some young pauses of 30s, and even up to 50s (normally <1s) running large Gerrit instances (200GB heap, 100 gc threads).
>> We have tried to tune ParallelGC. Reducing the number of gc threads helps to make the pause time spikes smaller but this makes average pause times longer.
>> 
>> This pr depends on
>> https://github.com/openjdk/jdk17u-dev/pull/2226
>> https://github.com/openjdk/jdk17u-dev/pull/2227
>> https://github.com/openjdk/jdk17u-dev/pull/2228
>> 
>> All hunks except the following 2 applied after a trivial preparation change.
>> The 1st hunk of psCardTable.hpp did not apply because of different context. Resolved by inserting the new lines.
>> The 2nd hunk of psScavenge.cpp did not apply because of different context. Resolved by inserting the new lines.
>> Finally a few trivial changes are required (renaming and the like).
>> 
>> Risk is medium. We've done the downstream backport already many weeks ago.
>> 
>> I've tested on x86_64:
>> jdk:tier1       TEST_VM_OPTS="-XX:+UseParallelGC"
>> langtools:tier1 TEST_VM_OPTS="-XX:+UseParallelGC"
>> 
>> Local CI Testing:
>> The fix passed our CI testing (e.g. 2024-02-25): JTReg tests: tier1-4 of hotspot and jdk. All of Langtools and jaxp. JCK, SPECjvm2008, SPECjbb2015, Renaissance Suite, and SAP specific tests (also with ParallelGC).
>> Testing was done with fastdebug builds on the main platforms and also on Linux/PPC64le.
>
> Richard Reingruber has refreshed the contents of this pull request, and previous commits have been removed. The incremental views will show differences compared to the previous content of the PR. The pull request contains one new commit since the last revision:
> 
>   Merge branch 'master' into 8310031_17u_backport

Thanks, Richard.

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PR Comment: https://git.openjdk.org/jdk17u-dev/pull/2230#issuecomment-1983691062