RFR: 8270009: Factor out and shuffle methods in G1CollectedHeap::do_collection_pause_at_safepoint_helper [v2]

[Kim Barrett]

On Mon, 12 Jul 2021 13:03:53 GMT, Thomas Schatzl <tschatzl at openjdk.org> wrote:

>> A problem with moving it later to the new placement is that it's now included in the pause time, where it previously wasn't.  I'm not sure it should be included in the pause time, as it's not really part of this collection.  I also wonder if the root scanning ought to be done using the concurrent workers rather than the stw workers, as there are typically fewer of the former (required to not be more?).
>
> It is true that it is now also included in the time used for MMU calculation (as part of the `record_collection_start/end` pair), which may a problem.
> 
> Previous gc timing also included it though, i.e. in the `note_gc_start()/print_phase_times()` pair.
> 
> I'll move it back then.

Things are unfortunately a bit messy and confusing/confused about pause time handling; see JDK-8240779 and JDK-7178365.

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PR: https://git.openjdk.java.net/jdk/pull/4744