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

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Message-ID: <634d9682-dc78-e09a-865c-9eed28aee667@tessares.net>
Date:   Wed, 30 Mar 2022 16:22:35 +0200
From:   Matthieu Baerts <matthieu.baerts@...sares.net>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     John Garry <john.garry@...wei.com>, peterz@...radead.org,
        mingo@...hat.com, mark.rutland@....com,
        alexander.shishkin@...ux.intel.com, jolsa@...nel.org,
        namhyung@...nel.org, irogers@...gle.com,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perf tools: Stop depending on .git files for building
 PERF-VERSION-FILE

Hi Arnaldo,

On 30/03/2022 16:12, Arnaldo Carvalho de Melo wrote:
> 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@...sares.net>
>>> Signed-off-by: John Garry <john.garry@...wei.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@...sares.net>
> 
> Ok?

Yes, OK for me, thank you!

I never know what maintainers prefer when there is already a
"Reported-by" tag so I didn't specify it but I will do next time.

Cheers,
Matt
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