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Message-Id: <1210840898.21616.27.camel@twins>
Date: Thu, 15 May 2008 10:41:38 +0200
From: Peter Zijlstra <a.p.zijlstra@...llo.nl>
To: vatsa@...ux.vnet.ibm.com
Cc: Mike Galbraith <efault@....de>,
"Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>,
Dhaval Giani <dhaval@...ux.vnet.ibm.com>,
LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
Aneesh Kumar KV <aneesh.kumar@...ux.vnet.ibm.com>
Subject: Re: volanoMark regression with kernel 2.6.26-rc1
On Thu, 2008-05-15 at 13:50 +0530, Srivatsa Vaddagiri wrote:
> On Wed, May 14, 2008 at 05:12:47PM +0200, Peter Zijlstra wrote:
> > A few other things I found that make a significant difference:
>
> One more observation: access to aggregate()->rq_weight etc arent
> correctly synchronized i.e while a cpu is doing a aggregate_walk_tree()
> in a domain, and thus possibly modifying rq_weight, load etc, other cpus could
> be concurrently accessing the same data. As a result, its possible to
> see inconsistent rq_weight, load, task_weight combination?
Yes - and that should not be too big an issue as long as we can deal
with it.
Any number we'll put to it will be based on a snapshot of the state so
we're wrong no matter what we do. The trick is trying to keep sane.
My current stack on top of sched-devel:
http://programming.kicks-ass.net/kernel-patches/sched-smp-group-fixes/
I've found that:
http://programming.kicks-ass.net/kernel-patches/sched-smp-group-fixes/sched-agg-update-move_tasks.patch
was sufficient to deal with all the anomalities I've found so far.
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