Commit f9212819 authored by Frederic Weisbecker's avatar Frederic Weisbecker
Browse files

perf: Make the trace events sample period default to 1 



Trace events are mostly used for tracing and then require not to
be lost when possible. As opposite to hardware events that really
require to trigger after a given sample period, trace events mostly
need to trigger everytime.

It is a frustrating experience to trace with perf and realize we
lost a lot of events because we forgot the "-c 1" option.

Then default sample_period to 1 for trace events but let the user
override it.

Signed-off-by: default avatarFrederic Weisbecker <fweisbec@gmail.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
parent bdef3b02

tools/perf/builtin-record.c

+22 −14
Original line number Diff line number Diff line
@@ -33,11 +33,13 @@ enum write_mode_t { 


static int			*fd[MAX_NR_CPUS][MAX_COUNTERS];



static unsigned int		user_interval 			= UINT_MAX;

static long			default_interval		=      0;



static int			nr_cpus				=      0;

static unsigned int		page_size;

static unsigned int		mmap_pages			=    128;

static unsigned int		user_freq 			= UINT_MAX;

static int			freq				=   1000;

static int			output;

static const char		*output_name			= "perf.data";
@@ -255,10 +257,19 @@ static void create_counter(int counter, int cpu) 
	if (nr_counters > 1)

		attr->sample_type |= PERF_SAMPLE_ID;



	/*

	 * We default some events to a 1 default interval. But keep

	 * it a weak assumption overridable by the user.

	 */

	if (!attr->sample_period || (user_freq != UINT_MAX &&

				     user_interval != UINT_MAX)) {

		if (freq) {

			attr->sample_type	|= PERF_SAMPLE_PERIOD;

			attr->freq		= 1;

			attr->sample_freq	= freq;

		} else {

			attr->sample_period = default_interval;

		}

	}



	if (no_samples)
@@ -689,13 +700,13 @@ static const struct option options[] = { 
			    "CPU to profile on"),

	OPT_BOOLEAN('f', "force", &force,

			"overwrite existing data file (deprecated)"),

	OPT_LONG('c', "count", &default_interval,

	OPT_LONG('c', "count", &user_interval,

		    "event period to sample"),

	OPT_STRING('o', "output", &output_name, "file",

		    "output file name"),

	OPT_BOOLEAN('i', "inherit", &inherit,

		    "child tasks inherit counters"),

	OPT_INTEGER('F', "freq", &freq,

	OPT_INTEGER('F', "freq", &user_freq,

		    "profile at this frequency"),

	OPT_INTEGER('m', "mmap-pages", &mmap_pages,

		    "number of mmap data pages"),
@@ -716,7 +727,6 @@ static const struct option options[] = { 


int cmd_record(int argc, const char **argv, const char *prefix __used)

{

	int counter;

	int i,j;



	argc = parse_options(argc, argv, options, record_usage,
@@ -774,6 +784,11 @@ int cmd_record(int argc, const char **argv, const char *prefix __used) 
	if (!event_array)

		return -ENOMEM;



	if (user_interval != UINT_MAX)

		default_interval = user_interval;

	if (user_freq != UINT_MAX)

		freq = user_freq;



	/*

	 * User specified count overrides default frequency.

	 */
@@ -786,12 +801,5 @@ int cmd_record(int argc, const char **argv, const char *prefix __used) 
		exit(EXIT_FAILURE);

	}



	for (counter = 0; counter < nr_counters; counter++) {

		if (attrs[counter].sample_period)

			continue;



		attrs[counter].sample_period = default_interval;

	}



	return __cmd_record(argc, argv);

}

tools/perf/util/parse-events.c

+2 −0
Original line number Diff line number Diff line
@@ -422,6 +422,8 @@ parse_single_tracepoint_event(char *sys_name, 
	attr->sample_type |= PERF_SAMPLE_TIME;

	attr->sample_type |= PERF_SAMPLE_CPU;



	attr->sample_period = 1;



	snprintf(evt_path, MAXPATHLEN, "%s/%s/%s/id", debugfs_path,

		 sys_name, evt_name);

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