RFR: Changes to simplify MU accounting

[Kelvin Nilsen]

On Thu, 11 May 2023 22:04:06 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.hpp line 70:
> 
>> 68: 
>> 69:   bool _most_recent_is_full;
>> 70:   bool _doing_mixed_evacuations;
> 
> This is written, but never read. Is this used somewhere on a different branch as part of the bigger picture?

Good catch.  It is no longer used.  I'll remove it.  (Its a remnant of early experiments with using GCU to trigger GC and wanting to treat GCU during mixed evac as different than GCU outside of mixed evac)  I couldn't figure out how to get a good trigger from GCU so I'll remove this for now.

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PR Review Comment: https://git.openjdk.org/shenandoah/pull/274#discussion_r1202993181