RFR: Changes to simplify MU accounting

[Kelvin Nilsen]

On Thu, 11 May 2023 22:15:25 GMT, William Kemper <wkemper at openjdk.org> wrote:

>> This represents a small part of the expand-old-on-demand branch.  By itself, this may result in some performance regression because we no longer use MU (mutator utilization) reports to guide generation sizing decisions.  On the other hand, the guidance provided by MU metrics does not seem to be a very accurate predictor of ideal generation sizes.
>
> src/hotspot/share/gc/shenandoah/shenandoahMmuTracker.cpp line 192:
> 
>> 190:   double mu = mutator_delta / (_active_processors * time_delta);
>> 191:   double gcu = gc_delta / (_active_processors * time_delta);
>> 192:   log_info(gc)("Periodic Sample: Average GCU = %.3f%%, Average MU = %.3f%%", gcu * 100, mu * 100);
> 
> These aren't really averages any more right? Just the utilization over the last period?

correct.  i'll change the log message in expand-old-on-demand.

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PR Review Comment: https://git.openjdk.org/shenandoah/pull/274#discussion_r1202966802