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

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Message-ID: <YbJZPsCfXi8QUbfR@krava>
Date:   Thu, 9 Dec 2021 20:30:06 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
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

On Thu, Dec 09, 2021 at 03:51:37PM -0300, Arnaldo Carvalho de Melo wrote:
> 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?

ok, yes

Acked-by: Jiri Olsa <jolsa@...hat.com>

jirka

> 
> - 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
>