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

From: Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>
To: Tommi Rantala <tommi.t.rantala@nokia.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Darren Hart <dvhart@infradead.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Jiri Olsa <jolsa@redhat.com>, Namhyung Kim <namhyung@kernel.org>,
	Davidlohr Bueso <dave@stgolabs.net>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/3] perf bench futex-wake: Restore thread count default to online CPU count
Date: Thu, 5 Mar 2020 11:51:49 -0300	[thread overview]
Message-ID: <20200305145149.GB7895@kernel.org> (raw)
In-Reply-To: <20200305083714.9381-3-tommi.t.rantala@nokia.com>

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@nokia.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