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

[Paul Hohensee]

On Sat, 24 Feb 2024 10:00:00 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.

Marked as reviewed by phh (Reviewer).

-------------

PR Review: https://git.openjdk.org/jdk17u-dev/pull/2230#pullrequestreview-1907431721