linux-kernel - Re: [PATCH v4 13/20] perf bench: New microbenchmark for userspace mutex performance

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Date:   Mon, 2 Jan 2017 13:17:19 -0500
From:   Waiman Long <longman@...hat.com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Jonathan Corbet <corbet@....net>, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, Davidlohr Bueso <dave@...olabs.net>,
        Mike Galbraith <umgwanakikbuti@...il.com>,
        Scott J Norton <scott.norton@....com>
Subject: Re: [PATCH v4 13/20] perf bench: New microbenchmark for userspace
 mutex performance

On 01/02/2017 12:16 PM, Arnaldo Carvalho de Melo wrote:
> Em Thu, Dec 29, 2016 at 11:13:39AM -0500, Waiman Long escreveu:
>> This microbenchmark simulates how the use of different futex types
>> can affect the actual performanace of userspace mutex locks. The
>> usage is:
>>
>>         perf bench futex mutex <options>
> Showing the tool output is preferred, trim it if needed or state why
> that is not possible.

I will do so when I update the patchset.

>  
>> Three sets of simple mutex lock and unlock functions are implemented
>> using the wait-wake, PI and TP futexes respectively. This
>> microbenchmark then runs the locking rate measurement tests using
>> either one of those mutexes or all of them consecutively.
>>
>> Signed-off-by: Waiman Long <longman@...hat.com>
>> ---
>>  tools/perf/bench/Build         |   1 +
>>  tools/perf/bench/bench.h       |   1 +
>>  tools/perf/bench/futex-locks.c | 844 +++++++++++++++++++++++++++++++++++++++++
>>  tools/perf/bench/futex.h       |  23 ++
>>  tools/perf/builtin-bench.c     |  10 +
>>  tools/perf/check-headers.sh    |   4 +
> You forgot to document it in tools/perf/Documentation/perf-bench.txt

Yes, I forgot about that. I will update the document in the next v5
patchset.

> Also I would suggest you submit this first without supportint TP
> futexes, i.e. supporting just what is in the kernel already, this way I
> could cherry-pick this, which would be useful already for benchmarking
> the existing types of futexes.
>
> Then, after the new futex type is accepted into the kernel, in a
> separate patch you would add support for it in 'perf bench futex mutex'.

I can separate out the TP portion of the changes and put them later in
the patchset.

Thanks for the comments.

Cheers,
Longman