Re: [PATCH] perf tools: Stop depending on .git files for building PERF-VERSION-FILE

[Arnaldo Carvalho de Melo <acme@kernel.org>]

Em Wed, Mar 30, 2022 at 03:22:37PM +0200, Matthieu Baerts escreveu:
> Hi John,
> 
> On 30/03/2022 12:22, John Garry wrote:
> > This essentially reverts commit c72e3f04b45fb2e50cdd81a50c3778c6a57251d8
> > and commit 4e666cdb06eede2069a7b1a96a1359d1c441a3eb.
> > 
> > In commit c72e3f04b45f ("tools/perf/build: Speed up git-version test on
> > re-make"), a makefile dependency on .git/HEAD was added. The background is
> > that running PERF-VERSION-FILE is relatively slow, and commands like
> > "git describe" are particularly slow.
> > 
> > In commit 4e666cdb06ee ("perf tools: Fix dependency for version file
> > creation"), an additional dependency on .git/ORIG_HEAD was added, as
> > .git/HEAD may not change for "git reset --hard HEAD^" command. However,
> > depending on whether we're on a branch or not, a "git cherry-pick" may
> > not lead to the version being updated.
> > 
> > As discussed with the git community in [0], using git internal files for
> > dependencies is not reliable. Commit 4e666cdb06ee also breaks some build
> > scenarios [1].
> > 
> > As mentioned, c72e3f04b45f was added to speed up the build. However in
> > commit 7572733b8499 ("perf tools: Fix version kernel tag") we removed the
> > call to "git describe", so just revert Makefile.perf back to same as pre
> > c72e3f04b45f and the build should not be so slow, as below:
> > 
> > Pre 7572733b8499:
> > $> time util/PERF-VERSION-GEN
> >   PERF_VERSION = 5.17.rc8.g4e666cdb06ee
> > 
> > real    0m0.110s
> > user    0m0.091s
> > sys     0m0.019s
> > 
> > Post 7572733b8499:
> > $> time util/PERF-VERSION-GEN
> >   PERF_VERSION = 5.17.rc8.g7572733b8499
> > 
> > real    0m0.039s
> > user    0m0.036s
> > sys     0m0.007s
> > 
> > [0] https://lore.kernel.org/git/87wngkpddp.fsf@igel.home/T/#m4a4dd6de52fdbe21179306cd57b3761eb07f45f8
> > [1] https://lore.kernel.org/linux-perf-users/20220329093120.4173283-1-matthieu.baerts@tessares.net/T/#u
> > 
> > Fixes: 4e666cdb06ee ("perf tools: Fix dependency for version file creation")
> > Reported-by: Matthieu Baerts <matthieu.baerts@tessares.net>
> > Signed-off-by: John Garry <john.garry@huawei.com>
> 
> Thank you for your patch, I just tested it and it also fixes the issue I
> reported!

I'm taking this as a:

Tested-by: Matthieu Baerts <matthieu.baerts@tessares.net>

Ok?

- Arnaldo