linux-kernel - Re: [PATCH v2] Fix fake numa on ppc

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Date:	Wed, 2 Sep 2009 13:09:01 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Balbir Singh <balbir@...ux.vnet.ibm.com>
cc:	Ankita Garg <ankita@...ibm.com>,
	LKML <linux-kernel@...r.kernel.org>, linuxppc-dev@...abs.org,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>
Subject: Re: [PATCH v2] Fix fake numa on ppc

On Thu, 3 Sep 2009, Balbir Singh wrote:

> > Right, I'm proposing an alternate mapping scheme (which we've used for
> > years) for both platforms such that a cpu is bound (and is set in
> > cpumask_of_node()) to each fake node with which it has physical affinity.
> > That is the only way for zonelist ordering in node order, task migration
> > from offlined cpus, correct sched domains, etc.  I can propose a patchset
> > for x86_64 to do exactly this if there aren't any objections and I hope
> > you'll help do ppc.
> 
> Sounds interesting, I'd definitely be interested in seeing your
> proposal, but I would think of that as additional development on top
> of this patch
> 

Absolutely.  I'm not familiar with numa=fake on ppc, but if cpus are being 
bound to nodes with which they don't have affinity, it definitely warrants 
a fix such as this (although the initial value for fake_enabled looks 
wrong and fake_numa_node_mapping[] can be __cpuinitdata).  I'll cc you, 
Ben, and Ankita on the x86_64 patches.  Thanks.