Re: [tip:perfcounters/urgent] perf stat: Add -n/--null option to run without counters

Jaswinder Singh Rajput
2009-06-27T07:57:20Z

On Sat, 2009-06-27 at 04:31 +0000, tip-bot for Ingo Molnar wrote:
> Commit-ID: 0cfb7a13b8e4e0afd4b856156ab16a182de7505b
> Gitweb: http://git.kernel.org/tip/0cfb7a13b8e4e0afd4b856156ab16a182de7505b
> Author: Ingo Molnar <mingo@elte.hu>
> AuthorDate: Sat, 27 Jun 2009 06:10:30 +0200
> Committer: Ingo Molnar <mingo@elte.hu>
> CommitDate: Sat, 27 Jun 2009 06:11:24 +0200
>
> perf stat: Add -n/--null option to run without counters
>
> Allow a no-counters run. This can be useful to measure just
> elapsed wall-clock time - or to assess the raw overhead of perf
> stat itself, without running any counters.
>

Why it better then $ time <command>

Any way this patch is broken.

Why you are allocating :
memcpy(attrs, default_attrs, sizeof(attrs)); when null_run is set.

To get better picture and solution, Please check [PATCH] perf stat: fix
default attrs and nr_counters

which I send in "Re: [PATCH -tip] perf_counter tools: add support to set
of multiple events in one short" send on Fri, 26 Jun 2009 18:08:40 +0530

Thanks,

--
JSR
> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
> Cc: Mike Galbraith <efault@gmx.de>
> Cc: Paul Mackerras <paulus@samba.org>
> Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
> LKML-Reference: <new-submission>
> Signed-off-by: Ingo Molnar <mingo@elte.hu>
>
>
> ---
> tools/perf/builtin-stat.c | 5 ++++-
> 1 files changed, 4 insertions(+), 1 deletions(-)
>
> diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
> index 8420ec5..cdcd058 100644
> --- a/tools/perf/builtin-stat.c
> +++ b/tools/perf/builtin-stat.c
> @@ -70,6 +70,7 @@ static int run_count = 1;
> static int inherit = 1;
> static int scale = 1;
> static int target_pid = -1;
> +static int null_run = 0;
>
> static int fd[MAX_NR_CPUS][MAX_COUNTERS];
>
> @@ -461,6 +462,8 @@ static const struct option options[] = {
> "be more verbose (show counter open errors, etc)"),
> OPT_INTEGER('r', "repeat", &run_count,
> "repeat command and print average + stddev (max: 100)"),
> + OPT_BOOLEAN('n', "null", &null_run,
> + "null run - dont start any counters"),
> OPT_END()
> };
>
> @@ -476,7 +479,7 @@ int cmd_stat(int argc, const char **argv, const char *prefix)
> if (run_count <= 0 || run_count > MAX_RUN)
> usage_with_options(stat_usage, options);
>
> - if (!nr_counters)
> + if (!null_run && !nr_counters)
> nr_counters = 8;
>
> nr_cpus = sysconf(_SC_NPROCESSORS_ONLN);
> --
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