RFR: 8254999: Move G1RemSetSamplingTask to more appropriate location [v2]

[Thomas Schatzl]

On Tue, 24 Nov 2020 08:53:18 GMT, Stefan Johansson <sjohanss at openjdk.org> wrote:

>> Please review this change that moves the `Remembered Set Sampling Task` from `g1ServiceThread.cpp` into `g1RemSet.cpp`. This is basically just a move but with a small edition that the task will reschedule itself instead of running if at start of execution the last GC happend more recently than the value of `G1ConcRefinementServiceIntervalMillis`.
>> 
>> This change does not cover moving the timing measurements from the service thread into the task, that will be covered by: 
>> [JDK-8252645](https://bugs.openjdk.java.net/browse/JDK-8252645)
>> 
>> Testing
>> Tier1-3 + local verification that the tast is scheduled as expected.
>
> Stefan Johansson has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains two additional commits since the last revision:
> 
>  - Merge branch 'master' into 8254999-move-sampling-task
>  - 8254999: Move G1RemSetSampligTask to more appropriate location

Changes requested by tschatzl (Reviewer).

src/hotspot/share/gc/g1/g1RemSet.cpp line 599:

> 597:     // Do the actual sampling.
> 598:     sample_young_list_rs_length(&sts);
> 599:     schedule(G1ConcRefinementServiceIntervalMillis);

I am good with the new location of the code but I would prefer if this change would be limited to the move and not change the rescheduling logic.
If it's not too much of a bother please split this out into a second CR.

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PR: https://git.openjdk.java.net/jdk/pull/1395