Re: Profiling sleep times?

[Arun Sharma <asharma@fb.com>]

On 10/3/11 1:17 PM, Peter Zijlstra wrote:
> On Mon, 2011-10-03 at 12:38 -0700, Arun Sharma wrote:
>>                           trace_sched_stat_sleep(tsk, delta);
>
> That one should be accessible as a tracepoint and will add delay to
> count on each occurrence.

Right - the tracepoint seems to work. Was looking for the user stack 
trace as well. For eg:

# cat foo.c
#include <unistd.h>
#include <time.h>
#include <sys/select.h>

main()
{
         struct timespec ts1;
         struct timeval tv1;
         int i;


         for (i = 0; i < 1000; i++) {
                 ts1.tv_sec = 0;
                 ts1.tv_nsec = 1000000;
                 nanosleep(&ts1, NULL);

                 tv1.tv_sec = 0;
                 tv1.tv_usec = 4000;
                 select(0, NULL, NULL, NULL, &tv1);
         }
}

I want something that gives me 4 times as many samples on select() as 
nanosleep().

perf record -g -e sched:sched_stat_sleep -- ./foo

doesn't seem to do it. Additionally, if I have a burn_1us_cpu() loop in 
there, I'd expect to see as many samples as nanosleep() in the wall 
clock profile.

  -Arun