linux-kernel - Re: [BUG] idle_balance() does not call load_balance

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Message-ID: <20081209040706.GA20525@dirshya.in.ibm.com>
Date:	Tue, 9 Dec 2008 09:37:06 +0530
From:	Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Linux Kernel <linux-kernel@...r.kernel.org>,
	Gautham R Shenoy <ego@...ibm.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [BUG] idle_balance() does not call load_balance_newidle()

* Ingo Molnar <mingo@...e.hu> [2008-12-08 16:49:39]:

> 
> * Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com> wrote:
> 
> > Hi,
> > 
> > load_balance_newidle() does not get called if SD_BALANCE_NEWIDLE is
> > set at higher level domain (3-CPU) and not in low level domain (2-MC).
> > 
> > pulled_task is initialised to -1 and checked for non-zero which is
> > always true if the lowest level sched_domain does not have
> > SD_BALANCE_NEWIDLE flag set.
> > 
> > Trivial fix to initialise pulled_task to zero.
> > Patch against 2.6.28-rc7
> 
> applied to tip/sched/core, thanks! (Not for v2.6.28 because this could 
> affect performance.)

Thanks Ingo.  This patch does not change any functionality in v2.6.28
and hence will not affect performance.  The SD flags are not touched.
I found this bug while setting different SD flags at MC level and CPU
level in my power saving balance patches.

--Vaidy
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