Re: [PATCH 0/8] Optimization batch 10: avoid detecting even more irrelevant renames

> 
> For the testcases mentioned in commit 557ac03 ("merge-ort: begin performance
> work; instrument with trace2_region_* calls", 2020-10-28), the changes in
> just this series improves the performance as follows:
> 
>                      Before Series           After Series
> no-renames:        5.680 s ±  0.096 s     5.665 s ±  0.129 s 
> mega-renames:     13.812 s ±  0.162 s    11.435 s ±  0.158 s
> just-one-mega:   506.0  ms ±  3.9  ms   494.2  ms ±  6.1  ms
> 
> 
> While those results may look somewhat meager, it is important to note that
> the previous optimizations have already reduced rename detection time to
> nearly 0 for these particular testcases so there just isn't much left to
> improve. The final patch in the series shows an alternate testcase where the
> previous optimizations aren't as effective (a simple cherry-pick of a commit
> that simply adds one new empty file), where there was a speedup factor of
> approximately 3 due to this series:
> 
>                      Before Series           After Series
> pick-empty:        1.936 s ±  0.024 s     688.1 ms ±  4.2 ms
> 
> 
> There was also another testcase at $DAYJOB where I saw a factor 7
> improvement from this particular optimization, so it certainly has the
> potential to help when the previous optimizations are not quite enough.