linux-kernel - Re: [RFC PATCH 0/3] Fix SLQB on memoryless configurations V2

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Message-ID: <20090922100706.GE12254@csn.ul.ie>
Date:	Tue, 22 Sep 2009 11:07:06 +0100
From:	Mel Gorman <mel@....ul.ie>
To:	Sachin Sant <sachinp@...ibm.com>
Cc:	Christoph Lameter <cl@...ux-foundation.org>,
	Nick Piggin <npiggin@...e.de>,
	Pekka Enberg <penberg@...helsinki.fi>,
	heiko.carstens@...ibm.com, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, Tejun Heo <tj@...nel.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Subject: Re: [RFC PATCH 0/3] Fix SLQB on memoryless configurations V2

On Tue, Sep 22, 2009 at 10:33:11AM +0530, Sachin Sant wrote:
> Mel Gorman wrote:
>> On Mon, Sep 21, 2009 at 01:54:12PM -0400, Christoph Lameter wrote:
>>   
>>> Lets just keep SLQB back until the basic issues with memoryless nodes are
>>> resolved.
>>>     
>>
>> It's not even super-clear that the memoryless nodes issues are entirely
>> related to SLQB. Sachin for example says that there was a stall issue
>> with memoryless nodes that could be triggered without SLQB. Sachin, is
>> that still accurate?
>>   
>
> I think there are two different problems that we are dealing with.
>

Agreed.

> First one is the SLQB not working on a ppc64 box which seems to be specific
> to only one machine and i haven't seen that on other power boxes.The patches
> that you have posted seems to allow the box to boot, but eventually it hits
> the stall issue(related to percpu dynamic allocator not working on ppc64),
> which is the second problem we are dealing with.
>
> The stall issue seems to be much more critical as it is affecting almost
> all of the power boxes that i have tested with (4 in all).
> This issue is seen with Linus tree as well and was first seen with
> 2.6.31-git5 (0cb583fd..) 
>
> The stall issue was reported here:
> http://lists.ozlabs.org/pipermail/linuxppc-dev/2009-September/075791.html
>

Because of this, I'd like to try and get SLQB as far as it can at the
moment and then treat this problem from scratch. I'd rather not treat
multiple different bugs as if they were one problem when they probably
are not.

Thanks

-- 
Mel Gorman
Part-time Phd Student                          Linux Technology Center
University of Limerick                         IBM Dublin Software Lab
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