linux-kernel - Re: [RFC] scheduler: improve SMP fairness in CFS

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Message-ID: <46A7B8A9.4040400@redhat.com>
Date:	Wed, 25 Jul 2007 16:55:05 -0400
From:	Chris Snook <csnook@...hat.com>
To:	Chris Friesen <cfriesen@...tel.com>
CC:	Ingo Molnar <mingo@...e.hu>, Tong Li <tong.n.li@...el.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC] scheduler: improve SMP fairness in CFS

Chris Friesen wrote:
> Ingo Molnar wrote:
> 
>> the 3s is the problem: change that to 60s! We no way want to 
>> over-migrate for SMP fairness, the change i did gives us reasonable 
>> long-term SMP fairness without the need for high-rate rebalancing.
> 
> Actually, I do have requirements from our engineering guys for 
> short-term fairness.  They'd actually like decent fairness over even 
> shorter intervals...1 second would be nice, 2 is acceptable.
> 
> They are willing to trade off random peak performance for predictability.
> 
> Chris
> 

The sysctls for CFS have nanosecond resolution.  They default to 
millisecond-order values, but you can set them much lower.  See sched_fair.c for 
the knobs and their explanations.

	-- Chris
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