linux-kernel - Re: [RFC] Fair-user scheduler

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Date:	Fri, 26 Jan 2007 12:41:27 -0600
From:	"Chris Friesen" <cfriesen@...tel.com>
To:	vatsa@...ibm.com
CC:	riel@...hat.com, Ingo Molnar <mingo@...e.hu>,
	Nick Piggin <nickpiggin@...oo.com.au>,
	Andrew Morton <akpm@...l.org>, linux-kernel@...r.kernel.org
Subject: Re: [RFC] Fair-user scheduler

Srivatsa Vaddagiri wrote:
> Current Linux CPU scheduler doesnt recognize process aggregates while
> allocating bandwidth. As a result of this, an user could simply spawn large 
> number of processes and get more bandwidth than others.
> 
> Here's a patch that provides fair allocation for all users in a system.
> 
> Some benchmark numbers with and without the patch applied follows:
> 
> 
> 		 	user "vatsa"		    user "guest"
> 		    (make -s -j4 bzImage)      (make -s -j20 bzImage)
> 
> 2.6.20-rc5		472.07s (real)		   257.48s (real)
> 2.6.20-rc5+fairsched	766.74s (real)		   766.73s (real)

As Kirill brought up, why does it take so much more time?  Are you 
thrashing the cache?

> 	- breaks O(1) (ouch!)
> 		Best way to avoid this is to split runqueue to be per-user and
> 		per-cpu, which I have not implemented to keep the patch simple.

Presumably this would be made generic, as in per-"group" rather than per 
user?

> 	- Fairsched aware SMP load balance NOT addressed (yet)

This is kind of important, no?

Chris
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