Re: delayacct regression in 2.6.24 git

[Ingo Molnar <mingo@elte.hu>]

* Balbir Singh <balbir@linux.vnet.ibm.com> wrote:

> >> Am I missing something?
> > 
> > delay accounting was causing context-switch slowdown because it 
> > called sched_clock() explicitly - but indeed my fix to that is wrong 
> > ...
> > 
> > how about reverting the change but also using rq->clock instead of 
> > sched_clock()?
> 
> Hmm... I think that might work, I find that schedule() calls 
> __update_rq_clock() which in turn calls sched_clock(), so it might be 
> a worthwhile optimization.

yep, that's the idea - in general rq->clock is updated for almost every 
scheduling event so you can rely on it instead of calling sched_clock() 
directly.

	Ingo