linux-kernel - Re: [PATCH v2] Unbuffered output when pipe/tee to a file

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Message-ID: <YbJQOfeeAoJ1GzJZ@kernel.org>
Date:   Thu, 9 Dec 2021 15:51:37 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Sohaib Mohamed <sohaib.amhmd@...il.com>, irogers@...gle.com,
        Riccardo Mancini <rickyman7@...il.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Fabian Hemmer <copy@...y.sh>, linux-perf-users@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] Unbuffered output when pipe/tee to a file

Em Sun, Nov 28, 2021 at 04:34:05PM +0100, Jiri Olsa escreveu:
> On Fri, Nov 19, 2021 at 08:14:08AM +0200, Sohaib Mohamed wrote:
> > The output of Perf bench gets buffered when I pipe it to a file or to
> > tee, in such a way that I can see it only at the end.
> > 
> > E.g.
> > $ perf bench internals synthesize -t
> > < output comes out fine after each test run >
> > 
> > $ perf bench internals synthesize -t | tee file.txt
> > < output comes out only at the end of all tests >
> > 
> > This patch resolves this issue for 'bench' and 'test' subcommands.
> 
> I can reproduce this for bench, but not for test subcommand
> other that that it makes sense to me

I reproduced it, see my comment to Sohaib's message, its not at the end,
its when the buffer fills up.

>From the "it makes sense to me" I'm deriving an Acked-by you, ok?

- Arnaldo
 
> jirka
> 
> > 
> > See, also:
> > $ perf bench mem all | tee file.txt
> > $ perf bench sched all | tee file.txt
> > $ perf bench internals all -t | tee file.txt
> > $ perf bench internals all | tee file.txt
> > 
> > Suggested-by: Riccardo Mancini <rickyman7@...il.com>
> > Signed-off-by: Sohaib Mohamed <sohaib.amhmd@...il.com>
> > ---
> > v1 -> v2:
> > - Use setvbuf(), instead of sprinkling fflush() calls and missing some places.
> > 
> > v1: https://lore.kernel.org/linux-perf-users/20211112215313.108823-1-sohaib.amhmd@gmail.com/
> > ---
> >  tools/perf/builtin-bench.c      | 5 +++--
> >  tools/perf/tests/builtin-test.c | 3 +++
> >  2 files changed, 6 insertions(+), 2 deletions(-)
> > 
> > diff --git a/tools/perf/builtin-bench.c b/tools/perf/builtin-bench.c
> > index d0895162c2ba..d291f3a8af5f 100644
> > --- a/tools/perf/builtin-bench.c
> > +++ b/tools/perf/builtin-bench.c
> > @@ -226,7 +226,6 @@ static void run_collection(struct collection *coll)
> >  		if (!bench->fn)
> >  			break;
> >  		printf("# Running %s/%s benchmark...\n", coll->name, bench->name);
> > -		fflush(stdout);
> > 
> >  		argv[1] = bench->name;
> >  		run_bench(coll->name, bench->name, bench->fn, 1, argv);
> > @@ -247,6 +246,9 @@ int cmd_bench(int argc, const char **argv)
> >  	struct collection *coll;
> >  	int ret = 0;
> > 
> > +	/* Unbuffered output */
> > +	setvbuf(stdout, NULL, _IONBF, 0);
> > +
> >  	if (argc < 2) {
> >  		/* No collection specified. */
> >  		print_usage();
> > @@ -300,7 +302,6 @@ int cmd_bench(int argc, const char **argv)
> > 
> >  			if (bench_format == BENCH_FORMAT_DEFAULT)
> >  				printf("# Running '%s/%s' benchmark:\n", coll->name, bench->name);
> > -			fflush(stdout);
> >  			ret = run_bench(coll->name, bench->name, bench->fn, argc-1, argv+1);
> >  			goto end;
> >  		}
> > diff --git a/tools/perf/tests/builtin-test.c b/tools/perf/tests/builtin-test.c
> > index 8cb5a1c3489e..d92ae4efd2e6 100644
> > --- a/tools/perf/tests/builtin-test.c
> > +++ b/tools/perf/tests/builtin-test.c
> > @@ -606,6 +606,9 @@ int cmd_test(int argc, const char **argv)
> >          if (ret < 0)
> >                  return ret;
> > 
> > +	/* Unbuffered output */
> > +	setvbuf(stdout, NULL, _IONBF, 0);
> > +
> >  	argc = parse_options_subcommand(argc, argv, test_options, test_subcommands, test_usage, 0);
> >  	if (argc >= 1 && !strcmp(argv[0], "list"))
> >  		return perf_test__list(argc - 1, argv + 1);
> > --
> > 2.25.1
> > 

-- 

- Arnaldo