RFR: Changes to simplify MU accounting

[Kelvin Nilsen]

On Thu, 11 May 2023 21:53:53 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 106:
> 
>> 104:     _most_recent_timestamp = current;
>> 105:   } else {
>> 106:     double gc_cycle_duration = current - _most_recent_timestamp;
> 
> Is this cycle duration? or time between cycles?

time-between-cycle ends.  i think that's not quite the same as time "between cycles".  Of course, duration suggests that GC is working the entire time, which it is not.  I think I'll go with "period", as updated in expand-old-on-demand branch.

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PR Review Comment: https://git.openjdk.org/shenandoah/pull/274#discussion_r1202946096