> * Frans Pop <elendil@planet.nl> wrote:
>
>>> It would be nice if you could try sched-devel/latest because it has
>>> an improved ftrace "sched_switch" tracer where you can generate much
>>> longer traces of this incident. Try the new /debug/trace_entries
>>> runtime tunable.
>> I'll try to get the trace and will reply on the private thread we had.
>> I may need additional instructions though.
>
> you could also reply to this thread if you dont mind, so that others can
> chime in too.
>
> the 700-800 msecs of delays you see are very "brutal" so there must be
> something fundamentally wrong going on here.
>
> Could you first check (under sched-devel/latest) the quality of your
> sched-clock, via running this script:
>
>
http://people.redhat.com/mingo/cfs-scheduler/tools/watch-rq-clock.sh
>
> if you run it, it should output ~1000 msecs periods every second:
>
> europe:~> watch-rq-clock.sh
> 1002.115042
> 1005.509851
> 1004.187275
> 1004.409980
> 1004.430264
> 1004.445508
>
> if it's way too 'slow', say it only 100 msecs per second, then the
> scheduler clock is mis-measuring time and what the scheduler thinks to
> be a 40 msecs delay might become a 400 msecs delay.
>
