From: Junio C Hamano <gitster@pobox.com>
To: Jeff King <peff@peff.net>
Cc: Jeff Hostetler <git@jeffhostetler.com>,
Taylor Blau <me@ttaylorr.com>,
Jeff Hostetler via GitGitGadget <gitgitgadget@gmail.com>,
git@vger.kernel.org, Jeff Hostetler <jeffhost@microsoft.com>
Subject: Re: [PATCH] t/perf/perf-lib.sh: remove test_times.* at the end test_perf_()
Date: Fri, 08 Oct 2021 10:30:09 -0700 [thread overview]
Message-ID: <xmqqee8vl90e.fsf@gitster.g> (raw)
In-Reply-To: <YV+zFqi4VmBVJYex@coredump.intra.peff.net> (Jeff King's message of "Thu, 7 Oct 2021 22:55:18 -0400")
Jeff King <peff@peff.net> writes:
> What I'd propose instead is that we ought to have:
>
> test_perf 'checkout'
> --prepare '
> git reset --hard the_original_state
> ' '
> git checkout
> '
>
> Having two multi-line snippets is a bit ugly (check out that awful
> middle line), but I think this could be added without breaking existing
> tests (they just wouldn't have a --prepare option).
>
> If that syntax is too horrendous, we could have:
>
> # this saves the snippet in a variable internally, and runs
> # it before each trial of the next test_perf(), after which
> # it is discarded
> test_perf_prepare '
> git reset --hard the_original_state
> '
>
> test_perf 'checkout' '
> git checkout
> '
>
> I think that would be pretty easy to implement, and would solve the most
> common form of this problem. And there's plenty of prior art; just about
> every decent benchmarking system has a "do this before each trial"
> mechanism. Our t/perf suite (as you probably noticed) is rather more
> ad-hoc and less mature.
Nice.
> 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.
next prev parent reply other threads:[~2021-10-08 17:30 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-04 22:29 [PATCH] t/perf/perf-lib.sh: remove test_times.* at the end test_perf_() Jeff Hostetler via GitGitGadget
2021-10-05 17:45 ` Taylor Blau
2021-10-06 19:24 ` Jeff King
2021-10-06 19:26 ` Taylor Blau
2021-10-07 17:49 ` Jeff Hostetler
2021-10-08 2:55 ` Jeff King
2021-10-08 7:47 ` A hard dependency on "hyperfine" for t/perf Ævar Arnfjörð Bjarmason
2021-10-08 17:30 ` Junio C Hamano [this message]
2021-10-08 19:57 ` [PATCH] t/perf/perf-lib.sh: remove test_times.* at the end test_perf_() Jeff King
2021-10-10 21:26 ` SZEDER Gábor
2021-10-13 21:09 ` Jeff Hostetler
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