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From: Frederic Weisbecker on 14 Apr 2010 17:00
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: Frederic Weisbecker <fweisbec(a)gmail.com>
Cc: Arnaldo Carvalho de Melo <acme(a)redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra(a)chello.nl>
Cc: Paul Mackerras <paulus(a)samba.org>
Cc: Ingo Molnar <mingo(a)elte.hu>
Cc: Thomas Gleixner <tglx(a)linutronix.de>
---
tools/perf/builtin-record.c | 36 ++++++++++++++++++++++--------------
tools/perf/util/parse-events.c | 2 ++
2 files changed, 24 insertions(+), 14 deletions(-)

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index dcda899..ca2affc 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -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;

- if (freq) {
- attr->sample_type |= PERF_SAMPLE_PERIOD;
- attr->freq = 1;
- attr->sample_freq = freq;
+ /*
+ * 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);
}
diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
index 880070c..3b4ec67 100644
--- a/tools/perf/util/parse-events.c
+++ b/tools/perf/util/parse-events.c
@@ -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);

--
1.6.2.3

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