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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.

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>
This commit is contained in:
Ingo Molnar 2009-06-27 06:10:30 +02:00
parent fde953c1c6
commit 0cfb7a13b8
1 changed files with 4 additions and 1 deletions
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5
tools/perf/builtin-stat.c
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@ -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);