linux-kernel - Re: [patch] CFS scheduler, -v12

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Message-ID: <20070524164538.GA13301@linux-os.sc.intel.com>
Date:	Thu, 24 May 2007 09:45:38 -0700
From:	"Siddha, Suresh B" <suresh.b.siddha@...el.com>
To:	Peter Williams <pwil3058@...pond.net.au>
Cc:	Ingo Molnar <mingo@...e.hu>, colpatch@...ibm.com,
	"Siddha, Suresh B" <suresh.b.siddha@...el.com>,
	Nick Piggin <nickpiggin@...oo.com.au>,
	Con Kolivas <kernel@...ivas.org>,
	Christoph Lameter <clameter@....com>,
	Dmitry Adamushko <dmitry.adamushko@...il.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [patch] CFS scheduler, -v12

On Thu, May 24, 2007 at 12:43:58AM -0700, Peter Williams wrote:
>Peter Williams wrote:
>> The relevant code, find_busiest_group() and find_busiest_queue(), has a 
>> lot of code that is ifdefed by CONFIG_SCHED_MC and CONFIG_SCHED_SMT and, 
>> as these macros were defined in the kernels I was testing with, I built 
>> a kernel with these macros undefined and reran my tests.  The 
>> problems/anomalies were not present in 10 consecutive tests on this new 
>> kernel.  Even better on the few occasions that a 3/1 split did occur it 
>> was quickly corrected to 2/2 and top was reporting approx 49% of CPU for 
>> all spinners throughout each of the ten tests.
>> 
>> So all that is required now is an analysis of the code inside the ifdefs 
>> to see why it is causing a problem.
>
>
>Further testing indicates that CONFIG_SCHED_MC is not implicated and
>it's CONFIG_SCHED_SMT that's causing the problem.  This rules out the
>code in find_busiest_group() as it is common to both macros.
>
>I think this makes the scheduling domain parameter values the most
>likely cause of the problem.  I'm not very familiar with this code so 
>I've added those who've modified this code in the last year or 
>so to the 
>address of this e-mail.

What platform is this? I remember you mentioned its a 2 cpu box. Is it
dual core or dual package or one with HT?

thanks,
suresh
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