Re: [RFC PATCH] check_preempt_tick should not compare vruntime with wall time

Ingo Molnar
2010-09-13T18:20:14Z

* Mathieu Desnoyers <mathieu.desnoyers@efficios.com> wrote:

> 2.0GHz Pentium M
>
> * wakeup-latency.c (SIGEV_THREAD) with make -j10
>
> - Mainline 2.6.35.2 kernel
>
> maximum latency: 45762.1 µs
> average latency: 7348.6 µs
> missed timer events: 0
>
> - check_preempt fix
>
> maximum latency: 39858.9 µs
> average latency: 7728.1 µs
> missed timer events: 0

Note that the check_preempt fix, as i mentioned it in the previous mail,
has no effect on this workload - so any effect you see is pure noise.

> - With only Peter's smaller min_gran (shown below):
>
> maximum latency: 29100.6 µs
> average latency: 6684.1 µs
> missed timer events: 0

That's the real improvement.

> - check_preempt fix + Peter's smaller min_gran:
> maximum latency: 20433.0 µs
> average latency: 5112.5 µs
> missed timer events: 0

Again, pure noise effect.

Ingo