Re: Performance loss 2.6.22->22.6.23->2.6.24-rc7 on CPU intensive benchmark on 8 Core Xeon

[Ingo Molnar <mingo@elte.hu>]

* Colin Fowler <elethiomel@gmail.com> wrote:

> > there are a handful of 'scheduler feature bits' in
> > /proc/sys/kernel/sched_features:
> >
> > enum {
> >         SCHED_FEAT_NEW_FAIR_SLEEPERS    = 1,
> >         SCHED_FEAT_WAKEUP_PREEMPT       = 2,
> >         SCHED_FEAT_START_DEBIT          = 4,
> >         SCHED_FEAT_TREE_AVG             = 8,
> >         SCHED_FEAT_APPROX_AVG           = 16,
> > };
> >
> 
> Toggling SCHED_FEAT_NEW_FAIR_SLEEPERS to 0 or 
> SCHED_FEAT_WAKEUP_PREEMPT to 0 gives me results more inline with my 
> 2.6.22 results. Toggling them both to 0 gives me slightly better 
> results than 2.6.22!

ok, but it would be nice to avoid having to turn these off. Could you 
try whether tuning the /proc/sys/kernel/*granularity* values (in 
particular wakeup_granularity) has any positive effect on your workload?

also, could you run your workload as SCHED_BATCH [via schedtool -B ], 
does that improve the results as well on a default-tuned kernel?

	Ingo