Re: sched_clock - microblaze

Steven Rostedt
2010-04-15T15:05:55Z

On Thu, 2010-04-15 at 16:55 +0200, Michal Simek wrote:
> Hi Thomas and Steven,
>
> I would like to improve time measuring for ftrace (Log below)
>
> I looked at http://lkml.org/lkml/2009/11/16/181
> where Thomas suggested to create sched_clock() function.
> I used the same solution as Wu proposed but it is not nice.
>
> Is unimplemented sched_clock the reason why ftrace not show fine grain time?

Yeah, sched_clock is used by ftrace for timings, so if it only returns
jiffies, then that will, unfortunately, be the resolution of the tracer.

I've been told that if you make a higher resolution timer for sched
clock, it will improve the scheduling in CFS.

-- Steve

>
> Or is there any other thing which is wrong?
>
> Thanks,
> Michal
>
>
>
> Dumping ftrace buffer:
> ---------------------------------
> 0) ! 10000.00 us | }
> 0) <========== |
> 0) ! 10000.00 us | }
> 0) ! 10000.00 us | }
> 0) 0.000 us | get_seconds();
> 0) 0.000 us | tcp_rcv_rtt_update();
> 0) 0.000 us | tcp_ack();
> 0) 0.000 us | tcp_rcv_rtt_update();
> 0) 0.000 us | tcp_urg();
> 0) | tcp_data_queue() {
> 0) 0.000 us | __sk_mem_schedule();
> 0) 0.000 us | tcp_event_data_recv();
> 0) 0.000 us | sock_def_readable();
> 0) 0.000 us | }
> 0) 0.000 us | tcp_check_space();
> 0) | __tcp_ack_snd_check() {
>
>