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Commit f9cef0a9 authored by Ingo Molnar's avatar Ingo Molnar
Browse files

perf stat: Add --sync/-S option 

--sync will tell perf stat to run sync() before starting a command.

This allows IO-heavy tests to be used with --repeat, without one
iteration impacting the other.

Elapsed time will stabilize for example:

  before:        3.971525714  seconds time elapsed  ( +-  8.56% )
  after:         3.211098537  seconds time elapsed  ( +-  1.52% )

So measurements will be more accurate.

Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/n/tip-7y40wib8n1eqio7hjpn1dsrm@git.kernel.org


Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 8a850cad

tools/perf/builtin-stat.c

+7 −0
Original line number Diff line number Diff line
@@ -128,6 +128,7 @@ static pid_t target_tid = -1; 
static pid_t			child_pid			= -1;

static bool			null_run			=  false;

static bool			detailed_run			=  false;

static bool			sync_run			=  false;

static bool			big_num				=  true;

static int			big_num_opt			=  -1;

static const char		*cpu_list;
@@ -819,6 +820,8 @@ static const struct option options[] = { 
		    "null run - dont start any counters"),

	OPT_BOOLEAN('d', "detailed", &detailed_run,

		    "detailed run - start a lot of events"),

	OPT_BOOLEAN('S', "sync", &sync_run,

		    "call sync() before starting a run"),

	OPT_CALLBACK_NOOPT('B', "big-num", NULL, NULL, 

			   "print large numbers with thousands\' separators",

			   stat__set_big_num),
@@ -944,6 +947,10 @@ int cmd_stat(int argc, const char **argv, const char *prefix __used) 
	for (run_idx = 0; run_idx < run_count; run_idx++) {

		if (run_count != 1 && verbose)

			fprintf(stderr, "[ perf stat: executing run #%d ... ]\n", run_idx + 1);



		if (sync_run)

			sync();



		status = run_perf_stat(argc, argv);

	}