RFR: 8307348 - Parallelize heap walk for ObjectCount(AfterGC) JFR event collection [v4]

[Aleksey Shipilev]

On Fri, 5 May 2023 06:49:15 GMT, Thomas Schatzl <tschatzl at openjdk.org> wrote:

> Can you elaborate about this? From what I can see, the callers of `report_object_count_after_gc` other than heap inspection always have GC workers available. As for `GenMarkSweep::mark_sweep_phase1` specifically - this is serial gc. There are no workers for it, and it's not supposed to use multiple threads. One would just pass `nullptr` here I assume.

Oh, I did not realize the implicit assumption about `GenMarkSweep` == Serial. I agree we can pass `nullptr` there. I wonder if there are other assumptions like that.

Let's try and do that change then, @olivergillespie!

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PR Comment: https://git.openjdk.org/jdk/pull/13774#issuecomment-1535926184