linux-kernel - [PATCH 5/7] perf stat: Create events as disabled

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Date:	Thu,  3 Dec 2015 10:06:44 +0100
From:	Jiri Olsa <jolsa@...nel.org>
To:	Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	David Ahern <dsahern@...il.com>,
	Ingo Molnar <mingo@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Adrian Hunter <adrian.hunter@...el.com>
Subject: [PATCH 5/7] perf stat: Create events as disabled

Currently we have 2 kinds of stat counters based on
when the event is enabled:
  1) tracee command events, which are enable once the
     tracee executes exec syscall (enable_on_exec bit)
  2) all other events which get alive within the
     perf_event_open syscall

Ad 2) case could raise a problem in case we want additional
filter to be attached for event. In this case we want the
event to be enabled after it's configured with filter.

Changing the behaviour of ad 2) events, so they all are
created as disabled (disabled bit). Adding extra enable
call to make them alive once they finish setup.

Link: http://lkml.kernel.org/n/tip-xwx95lcwjpt40uwzhos3ks9i@git.kernel.org
Signed-off-by: Jiri Olsa <jolsa@...nel.org>
---
 tools/perf/builtin-stat.c | 25 +++++++++++++++++++------
 1 file changed, 19 insertions(+), 6 deletions(-)

diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index 8ca40deaa728..2e70610649a1 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -168,11 +168,18 @@ static int create_perf_stat_counter(struct perf_evsel *evsel)
 	attr->sample_period = 0;
 	attr->sample_type   = 0;
 
+	/*
+	 * Disabling all counters initially, they will be enabled
+	 * either manually by us or by kernel via enable_on_exec
+	 * set later.
+	 */
+	if (perf_evsel__is_group_leader(evsel))
+		attr->disabled = 1;
+
 	if (target__has_cpu(&target))
 		return perf_evsel__open_per_cpu(evsel, perf_evsel__cpus(evsel));
 
 	if (!target__has_task(&target) && perf_evsel__is_group_leader(evsel)) {
-		attr->disabled = 1;
 		if (!initial_delay)
 			attr->enable_on_exec = 1;
 	}
@@ -251,12 +258,18 @@ static void process_interval(void)
 	print_counters(&rs, 0, NULL);
 }
 
-static void handle_initial_delay(void)
+static void enable_counters(void)
 {
-	if (initial_delay) {
+	if (initial_delay)
 		usleep(initial_delay * 1000);
+
+	/*
+	 * We need to enable counters only if:
+	 * - we don't have tracee (attaching to task or cpu)
+	 * - we have initial delay configured
+	 */
+	if (!target__none(&target) || initial_delay)
 		perf_evlist__enable(evsel_list);
-	}
 }
 
 static volatile int workload_exec_errno;
@@ -353,7 +366,7 @@ static int __run_perf_stat(int argc, const char **argv)
 
 	if (forks) {
 		perf_evlist__start_workload(evsel_list);
-		handle_initial_delay();
+		enable_counters();
 
 		if (interval) {
 			while (!waitpid(child_pid, &status, WNOHANG)) {
@@ -372,7 +385,7 @@ static int __run_perf_stat(int argc, const char **argv)
 		if (WIFSIGNALED(status))
 			psignal(WTERMSIG(status), argv[0]);
 	} else {
-		handle_initial_delay();
+		enable_counters();
 		while (!done) {
 			nanosleep(&ts, NULL);
 			if (interval)
-- 
2.4.3

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