On Tue, Jul 27, 2021 at 05:20:28PM -0400, Taylor Blau wrote: > These new performance tests demonstrate effectively the same behavior as > p5310, but use a multi-pack bitmap instead of a single-pack one. > > Notably, p5326 does not create a MIDX bitmap with multiple packs. This > is so we can measure a direct comparison between it and p5310. Any > difference between the two is measuring just the overhead of using MIDX > bitmaps. > > Here are the results of p5310 and p5326 together, measured at the same > time and on the same machine (using a Xenon W-2255 CPU): Neat. I think having separate perf regression tests for regular and mix bitmaps will be useful, but being able to compare the pack and mix versions is a cherry on top. There was one funny number: > 5310.2: repack to disk 96.78(93.39+11.33) > 5326.2: setup multi-pack index 78.99(75.29+11.58) In p5310, that step is repacking and writing bitmaps. With the midx, it's repacking, then writing a midx with bitmaps. I'd expect the latter to be strictly slower than the former, but here it's faster. Running the code locally, I got similar results (with p5310 just a tiny bit faster). So it may have just been noise or some other timing issue. As an aside, I think that test is a little bit bogus due to GIT_PERF_REPEAT_COUNT; the first trial will generate bitmaps from scratch, and then subsequent runs will reuse partial results. It probably should "rm -f .git/objects/*.bitmap" within the test. We can deal with that separately, though. -Peff
