RFR: 8343298: Improve stability of runtime/cds/DeterministicDump.java test

[Aleksey Shipilev]

On Mon, 4 Nov 2024 09:57:46 GMT, Thomas Schatzl <tschatzl at openjdk.org> wrote:

> Hi all,
> 
>   please review this change to make `runtime/cds/DeterministicDump.java` more reliable in presence of GC changes (which https://bugs.openjdk.org/browse/JDK-8295269 stumbled over).
> 
> This includes some change to strip the gc age from the dumped objects, but mainly trying to fix heap sizes etc so that GCs are executed consistently (i.e. not at all) in this test.
> 
> Testing: tier5, running the test a few thousand times
> 
> Thanks,
>   Thomas

Generally looks okay, but I have a few questions:

test/hotspot/jtreg/runtime/cds/DeterministicDump.java line 56:

> 54:         baseArgs.add("-Xmx128M");
> 55:         baseArgs.add("-Xms128M");
> 56:         baseArgs.add("-Xmn128M");

Is it legal/useful to set `Xmn` = `Xmx`?

test/hotspot/jtreg/runtime/cds/DeterministicDump.java line 57:

> 55:         baseArgs.add("-Xms128M");
> 56:         baseArgs.add("-Xmn128M");
> 57:         baseArgs.add("-XX:ParallelGCThreads=1");

`-XX:ConcGCThreads=1` as well, maybe?

test/hotspot/jtreg/runtime/cds/DeterministicDump.java line 59:

> 57:         baseArgs.add("-XX:ParallelGCThreads=1");
> 58:         baseArgs.add("-XX:-ResizeTLAB");
> 59:         baseArgs.add("-XX:-ResizePLAB");

I am guessing we do not want to `-XX:-UseTLAB` summarily, so we get at least the same sized LABs all the time?

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PR Review: https://git.openjdk.org/jdk/pull/21871#pullrequestreview-2412912465
PR Review Comment: https://git.openjdk.org/jdk/pull/21871#discussion_r1827639685
PR Review Comment: https://git.openjdk.org/jdk/pull/21871#discussion_r1827639958
PR Review Comment: https://git.openjdk.org/jdk/pull/21871#discussion_r1827640681