Re: [PATCH RFC] smt nice introduces significant lock contention

[Con Kolivas <kernel@kolivas.org>]

On Friday 02 June 2006 19:31, Chen, Kenneth W wrote:
> Con Kolivas wrote on Friday, June 02, 2006 2:25 AM
>
> > On Friday 02 June 2006 19:17, Chen, Kenneth W wrote:
> > > What about the part in dependent_sleeper() being so bully and actively
> > > resched other low priority sibling tasks?  I think it would be better
> > > to just let the tasks running on sibling CPU to finish its current time
> > > slice and then let the backoff logic to kick in.
> >
> > That would defeat the purpose of smt nice if the higher priority task
> > starts after the lower priority task is running on its sibling cpu.
>
> But only for the duration of lower priority tasks' time slice.  When lower
> priority tasks time slice is used up, a resched is force from
> scheduler_tick(), isn't it?  And at that time, it is delayed to run because
> of smt_nice.  You are saying user can't tolerate that short period of time
> that CPU resource is shared?  It's hard to believe.

nice -20 vs nice 0 is 800ms vs 100ms. That's a long time to me.

-- 
-ck
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