linux-kernel - Re: update on hrtimer based select/poll and range-hrtimers

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Message-ID: <20080907140746.3de99747@infradead.org>
Date:	Sun, 7 Sep 2008 14:07:46 -0700
From:	Arjan van de Ven <arjan@...radead.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	linux-kernel@...r.kernel.org, mingo@...e.hu, tglx@...x.de,
	torvalds@...ux-foundation.org
Subject: Re: update on hrtimer based select/poll and range-hrtimers

On Sun, 07 Sep 2008 22:46:39 +0200
Peter Zijlstra <peterz@...radead.org> wrote:
> > "0.1% of the time" for not-nice, not realtime tasks
> > "0.5% of the time" for nice, not realtime tasks
> > with a cap of 100msec for both.
> > 
> > I would like to request feedback on this approach; I think this is
> > better than the "hardcoded steps" as before, but maybe someone can
> > come up with an ever better idea....
> 
> logarithms pop to mind (again :-)

and it still doesn't strike me as "oh yeah"

how would you see this work? Can you give a numeric example?

> 
> > static unsigned long __estimate_accuracy(struct timespec *tv)
> > {
> >         unsigned long slack;
> >         int divfactor = 1000;
> >   
> >         if (task_nice(current))
> 
> This triggers for both -nice and +nice tasks, it might be worth
> differentiating between those.

good spotting; will fix.


> > 
> >         if (current->policy == SCHED_FIFO ||
> >                 current->policy == SCHED_RR)
> >                 return 0;
> 
> rt_task(current) ?

hmm that's not exactly equivalent.. I can see either but still.


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