RFR: JDK-8293114: GC should trim the native heap [v9]

[Robbin Ehn]

On Wed, 8 Feb 2023 08:11:20 GMT, Thomas Stuefe <stuefe at openjdk.org> wrote:

> I will repeat the tests. What benchmark would you recommend? I also plan to do a regular benchmark but with an agent lib injected that does concurrent malloc spikes, to mimic third party code doing mallocs on the side.

Internally we have seem workloads that involves classloading as a builder of RSS. (thought to be Symbols (we are looking into that now))
But I don't know what, and if there is such, benchmark that do classloading during the "performance cycle".

Another observation is that if we get unlucky, it seem like we could be trimming (NativeTrimmerThread) while cleaning e.g. stringtable (via ServiceThread). Thus calling free a lot, not sure if that is problematic.
Another case is if user only have very few logical cores, if ServiceThread+NativeTrimmerThread running at the same time user may experience some additional hick-ups.

So we maybe want to use ServiceThread at the cost of sometimes delaying the trimming due to other work?

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PR: https://git.openjdk.org/jdk/pull/10085