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

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Date:   Thu, 5 Mar 2020 11:51:49 -0300
From:   Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
To:     Tommi Rantala <tommi.t.rantala@...ia.com>
Cc:     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>,
        Davidlohr Bueso <dave@...olabs.net>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] perf bench futex-wake: Restore thread count default
 to online CPU count

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.

- Arnaldo

> Signed-off-by: Tommi Rantala <tommi.t.rantala@...ia.com>
> ---
>  tools/perf/bench/futex-wake.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/perf/bench/futex-wake.c b/tools/perf/bench/futex-wake.c
> index df810096abfef..58906e9499bb0 100644
> --- a/tools/perf/bench/futex-wake.c
> +++ b/tools/perf/bench/futex-wake.c
> @@ -43,7 +43,7 @@ static bool done = false, silent = false, fshared = false;
>  static pthread_mutex_t thread_lock;
>  static pthread_cond_t thread_parent, thread_worker;
>  static struct stats waketime_stats, wakeup_stats;
> -static unsigned int ncpus, threads_starting, nthreads = 0;
> +static unsigned int threads_starting, nthreads = 0;
>  static int futex_flag = 0;
>  
>  static const struct option options[] = {
> @@ -141,7 +141,7 @@ int bench_futex_wake(int argc, const char **argv)
>  	sigaction(SIGINT, &act, NULL);
>  
>  	if (!nthreads)
> -		nthreads = ncpus;
> +		nthreads = cpu->nr;
>  
>  	worker = calloc(nthreads, sizeof(*worker));
>  	if (!worker)
> -- 
> 2.21.1
> 

-- 

- Arnaldo