linux-kernel - Re: [PATCH 2/3] perf bench futex-wake: Restore thread count default to online CPU count

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Message-ID: <20200305153434.5r2jqsfxyrusrgwc@linux-p48b>
Date:   Thu, 5 Mar 2020 07:34:34 -0800
From:   Davidlohr Bueso <dave@...olabs.net>
To:     Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
Cc:     Tommi Rantala <tommi.t.rantala@...ia.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Darren Hart <dvhart@...radead.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] perf bench futex-wake: Restore thread count default
 to online CPU count

On Thu, 05 Mar 2020, Arnaldo Carvalho de Melo wrote:

>Em Thu, Mar 05, 2020 at 10:37:13AM +0200, Tommi Rantala escreveu:
>> Since commit 3b2323c2c1c4 ("perf bench futex: Use cpumaps") the default
>> number of threads the benchmark uses got changed from number of online
>> CPUs to zero:
>>
>>   $ perf bench futex wake
>>   # Running 'futex/wake' benchmark:
>>   Run summary [PID 15930]: blocking on 0 threads (at [private] futex 0x558b8ee4bfac), waking up 1 at a time.
>>   [Run 1]: Wokeup 0 of 0 threads in 0.0000 ms
>>   [...]
>>   [Run 10]: Wokeup 0 of 0 threads in 0.0000 ms
>>   Wokeup 0 of 0 threads in 0.0004 ms (+-40.82%)
>>
>> Restore the old behavior by grabbing the number of online CPUs via
>> cpu->nr:
>>
>>   $ perf bench futex wake
>>   # Running 'futex/wake' benchmark:
>>   Run summary [PID 18356]: blocking on 8 threads (at [private] futex 0xb3e62c), waking up 1 at a time.
>>   [Run 1]: Wokeup 8 of 8 threads in 0.0260 ms
>>   [...]
>>   [Run 10]: Wokeup 8 of 8 threads in 0.0270 ms
>>   Wokeup 8 of 8 threads in 0.0419 ms (+-24.35%)
>>
>> Fixes: 3b2323c2c1c4 ("perf bench futex: Use cpumaps")
>
>Thanks, tested and applied.

Thanks!