linux-kernel - Re: [patch] CFS (Completely Fair Scheduler), v2

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Date:	Tue, 17 Apr 2007 18:30:48 +1000
From:	Peter Williams <pwil3058@...pond.net.au>
To:	William Lee Irwin III <wli@...omorphy.com>
CC:	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Con Kolivas <kernel@...ivas.org>,
	Nick Piggin <npiggin@...e.de>, Mike Galbraith <efault@....de>,
	Arjan van de Ven <arjan@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>, caglar@...dus.org.tr,
	Willy Tarreau <w@....eu>,
	Gene Heskett <gene.heskett@...il.com>,
	Dmitry Adamushko <dmitry.adamushko@...il.com>
Subject: Re: [patch] CFS (Completely Fair Scheduler), v2

William Lee Irwin III wrote:
> Ingo Molnar wrote:
>>> this is the second release of the CFS (Completely Fair Scheduler) 
>>> patchset, against v2.6.21-rc7:
>>>    http://redhat.com/~mingo/cfs-scheduler/sched-cfs-v2.patch
>>> i'd like to thank everyone for the tremendous amount of feedback and 
>>> testing the v1 patch got - i could hardly keep up with just reading the 
>>> mails! Some of the stuff people addressed i couldnt implement yet, i 
>>> mostly concentrated on bugs, regressions and debuggability.
> 
> On Tue, Apr 17, 2007 at 04:46:57PM +1000, Peter Williams wrote:
>> Have you considered using rq->raw_weighted_load instead of 
>> rq->nr_running in calculating fair_clock?  This would take the nice 
>> value (or RT priority) of the other tasks into account when determining 
>> what's fair.
> 
> I suspect you mean (curr->load_weight*delta_exec)/rq->raw_weighted_load
> in update_curr().

Or something like that, yes. :-)

I was trying to make the point that the weighted load stuff provides 
useful data for implementing nice (in a number of ways e.g. see spa_ebs).

Also, now that the old time slices are gone, a simpler more efficient 
function for mapping RT priority or nice (as appropriate) to 
p->load_weight can be used instead of the current one which uses the 
time slice the task would have been allocated as a basis.  I'd suggest 
the function that the current one replaced.  (Because it was mine :-)).

Peter
-- 
Peter Williams                                   pwil3058@...pond.net.au

"Learning, n. The kind of ignorance distinguishing the studious."
  -- Ambrose Bierce
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