linux-kernel - Re: [PATCH] perf bench: Flush stdout before starting bench suite

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Message-ID: <87r4lv93nb.wl%h.mitake@gmail.com>
Date:	Tue, 08 Jan 2013 22:59:36 +0900
From:	Hitoshi Mitake <h.mitake@...il.com>
To:	Namhyung Kim <namhyung@...nel.org>
Cc:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Mackerras <paulus@...ba.org>,
	Ingo Molnar <mingo@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Namhyung Kim <namhyung.kim@....com>,
	Hitoshi Mitake <mitake@....info.waseda.ac.jp>
Subject: Re: [PATCH] perf bench: Flush stdout before starting bench suite

At Tue,  8 Jan 2013 18:39:26 +0900,
Namhyung Kim wrote:
> 
> From: Namhyung Kim <namhyung.kim@....com>
> 
> perf bench prints header message for bench suite before starting the
> benchmark.  However if the stdout is redirected to a file and bench
> suite forks child processes this (and possibly other debugging
> messages too) will be repeated multiple times.
> 
>   $ perf bench sched messaging
>   # Running sched/messaging benchmark...
>   # 20 sender and receiver processes per group
>   # 10 groups == 400 processes run
> 
>        Total time: 0.100 [sec]
> 
>   $ perf bench sched messaging > result.txt
>   $ wc -l result.txt
>   391
> 
> In this file, there were so many "Running sched/messaging benchmark..."
> lines.  This was because stdout is converted to fully-buffered due to
> the redirection and inherited child processes.  Other lines are printed
> after reaping all those tasks.
> 
> So fix it by flushing stdout before starting bench suites.

Thanks a lot, I couldn't notice this problem.

Acked-by: Hitoshi Mitake <h.mitake@...il.com>

> 
> Cc: Hitoshi Mitake <mitake@....info.waseda.ac.jp>
> Signed-off-by: Namhyung Kim <namhyung@...nel.org>
> ---
>  tools/perf/builtin-bench.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/tools/perf/builtin-bench.c b/tools/perf/builtin-bench.c
> index cae9a5fd2ecf..afd1255a632f 100644
> --- a/tools/perf/builtin-bench.c
> +++ b/tools/perf/builtin-bench.c
> @@ -159,6 +159,7 @@ static void all_suite(struct bench_subsys *subsys)	  /* FROM HERE */
>  		printf("# Running %s/%s benchmark...\n",
>  		       subsys->name,
>  		       suites[i].name);
> +		fflush(stdout);
>  
>  		argv[1] = suites[i].name;
>  		suites[i].fn(1, argv, NULL);
> @@ -225,6 +226,7 @@ int cmd_bench(int argc, const char **argv, const char *prefix __maybe_unused)
>  				printf("# Running %s/%s benchmark...\n",
>  				       subsystems[i].name,
>  				       subsystems[i].suites[j].name);
> +			fflush(stdout);
>  			status = subsystems[i].suites[j].fn(argc - 1,
>  							    argv + 1, prefix);
>  			goto end;
> -- 
> 1.7.11.7
> 
> 
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