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

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Date:	Fri, 26 Jan 2007 17:09:00 +0300
From:	Kirill Korotaev <dev@...ru>
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,

> 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)
1. If I interpret these numbers correctly, then your scheduler is not work-conservative,
i.e. 766.74 + 766.73 >> 472.07 + 257.48
why does it slow down users so much?
2. compilation of kernel is quite CPU-bound task. So it's not that hard to be fair :)
   Can you please try some other applications?
   e.g. pipe-based context switching, java Volano benchmark etc.

Thanks,
Kirill

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