On Fri, Oct 08, 2021 at 10:30:09AM -0700, Junio C Hamano wrote: > > There are cases it doesn't help, though. For instance, in one of the > > scripts we measure the time to run "git repack -adb" to generate > > bitmaps. But the first run has to do more work, because we can reuse > > results for subsequent ones! It would help to "rm -f > > objects/pack/*.bitmap", but even that's not entirely fair, as it will be > > repacking from a single pack, versus whatever state we started with. > > You need a "do this too for each iteration but do not time it", i.e. > > test_perf 'repack performance' --prepare ' > make a messy original repository > ' --per-iteration-prepare ' > prepare a test repository from the messy original > ' --time-this-part-only ' > git repack -adb > ' > > Syntactically, eh, Yuck. If any step doesn't need to be per-iteration, you can do it in a separate test_expect_success block. So --prepare would always be per-iteration, I think. The tricky thing I meant to highlight in that example is that the preparation step is non-obvious, since the timed command actually throws away the original state. But we can probably stash away what we need. With the test_perf_prepare I showed earlier, maybe: test_expect_success 'stash original state' ' cp -al objects objects.orig ' test_perf_prepare 'set up original state' ' rm -rf objects && cp -al objects.orig objects ' test_perf 'repack' ' git repack -adb ' which is not too bad. Of course it is made a lot easier by my use of the unportable "cp -l", but you get the general idea. ;) This is all a rough sketch anyway, and not something I plan on working on anytime soon. For Jeff's case, the preparation would hopefully just be some sequence of reset/read-tree/etc to manipulate the index and working tree to the original state. -Peff
