If recording a big number of events to a big buffer, one might want to
minimize the trace-cmd activity for a certain period in time.
Especially, don't see any trace-cmd activity for some time. If there are
a lot of events, the loop might actually never sleep, resulting in the
"-s" option never becomming active.
E.g. I am using scheduler events to trace thread activity per CPU. Esp.
sched:sched_wakeup and sched:sched_stat_runtime. Even when setting the
sleep time to something huge like 30 seconds, I can see constant activity
from the trace-cmd tasks.
Signed-off-by: David Hildenbrand <da...@redhat.com>
---
Documentation/trace-cmd-record.1.txt | 10 ++++++++++
trace-cmd.h | 3 ++-
trace-record.c | 11 ++++++++++-
trace-recorder.c | 9 ++++++++-
4 files changed, 30 insertions(+), 3 deletions(-)
diff --git a/Documentation/trace-cmd-record.1.txt
b/Documentation/trace-cmd-record.1.txt
index 68afa16..d429caf 100644
--- a/Documentation/trace-cmd-record.1.txt
+++ b/Documentation/trace-cmd-record.1.txt
@@ -326,6 +326,16 @@ OPTIONS
executed will not be changed. This is useful if you want to monitor the
output of the command being executed, but not see the output from
trace-cmd.
+*--initital-delay* 'delay'::
+ The processes that trace-cmd creates to record from the ring buffer need
+ to start copying the data from the ring buffer at some point in time.
+ Setting the 'delay' to zero will cause the processes to start copying
+ from the ring buffer immediately. This is helpful when wanting to
+ minimize trace-cmd activity during some period of time (where -s
+ will not help due to the amount of events being recorded).
+
+ The 'delay' metric is microseconds. The default is set to 0.
+
EXAMPLES
--------
diff --git a/trace-cmd.h b/trace-cmd.h
index 6fd34d7..bae7153 100644
--- a/trace-cmd.h
+++ b/trace-cmd.h
@@ -285,7 +285,8 @@ struct tracecmd_recorder
*tracecmd_create_buffer_recorder_fd(int fd, int cpu, un
struct tracecmd_recorder *tracecmd_create_buffer_recorder(const char *file,
int cpu, unsigned flags, const char *buffer);
struct tracecmd_recorder *tracecmd_create_buffer_recorder_maxkb(const char
*file, int cpu, unsigned flags, const char *buffer, int maxkb);
-int tracecmd_start_recording(struct tracecmd_recorder *recorder, unsigned long
sleep);
+int tracecmd_start_recording(struct tracecmd_recorder *recorder,
+ unsigned long sleep, unsigned long initital_sleep);
void tracecmd_stop_recording(struct tracecmd_recorder *recorder);
void tracecmd_stat_cpu(struct trace_seq *s, int cpu);
long tracecmd_flush_recording(struct tracecmd_recorder *recorder);
diff --git a/trace-record.c b/trace-record.c
index f128257..cd6e158 100644
--- a/trace-record.c
+++ b/trace-record.c
@@ -79,6 +79,7 @@ static const char *output_file = "trace.dat";
static int latency;
static int sleep_time = 1000;
+static int initial_sleep_time = 0;
static int recorder_threads;
static struct pid_record_data *pids;
static int buffers;
@@ -2668,7 +2669,8 @@ static int create_recorder(struct buffer_instance
*instance, int cpu,
}
while (!finished) {
- if (tracecmd_start_recording(recorder, sleep_time) < 0)
+ if (tracecmd_start_recording(recorder, sleep_time,
+ initial_sleep_time) < 0)
break;
}
tracecmd_free_recorder(recorder);
@@ -4211,6 +4213,7 @@ enum {
OPT_funcstack = 254,
OPT_date = 255,
OPT_module = 256,
+ OPT_initital_delay = 257,
};
void trace_stop(int argc, char **argv)
@@ -4452,6 +4455,7 @@ static void parse_record_options(int argc,
{"quiet", no_argument, NULL, OPT_quiet},
{"help", no_argument, NULL, '?'},
{"module", required_argument, NULL, OPT_module},
+ {"initital-delay", required_argument, NULL,
OPT_initital_delay},
{NULL, 0, NULL, 0}
};
@@ -4732,6 +4736,11 @@ static void parse_record_options(int argc,
ctx->instance->filter_mod = optarg;
ctx->filtered = 0;
break;
+ case OPT_initital_delay:
+ if (!optarg)
+ usage(argv);
+ initial_sleep_time = atoi(optarg);
+ break;
case OPT_quiet:
case 'q':
quiet = 1;
diff --git a/trace-recorder.c b/trace-recorder.c
index 85150fd..a48c9e8 100644
--- a/trace-recorder.c
+++ b/trace-recorder.c
@@ -439,7 +439,8 @@ long tracecmd_flush_recording(struct tracecmd_recorder
*recorder)
return total;
}
-int tracecmd_start_recording(struct tracecmd_recorder *recorder, unsigned long
sleep)
+int tracecmd_start_recording(struct tracecmd_recorder *recorder,
+ unsigned long sleep, unsigned long initital_sleep)
{
struct timespec req;
long read = 1;
@@ -447,6 +448,12 @@ int tracecmd_start_recording(struct tracecmd_recorder
*recorder, unsigned long s
recorder->stop = 0;
+ if (initital_sleep) {
+ req.tv_sec = initital_sleep / 1000000;
+ req.tv_nsec = (initital_sleep % 1000000) * 1000;
+ nanosleep(&req, NULL);
+ }
+
do {
/* Only sleep if we did not read anything last time */
if (!read && sleep) {
--
2.14.3
