linux-kernel - Re: [PATCH] pci: derive nearby CPUs from device's instead of bus' NUMA information

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Date:	Mon, 20 Apr 2009 13:03:41 -0700
From:	Jesse Barnes <jbarnes@...tuousgeek.org>
To:	Andreas Herrmann <andreas.herrmann3@....com>
Cc:	Yinghai Lu <yhlu.kernel@...il.com>, Ingo Molnar <mingo@...e.hu>,
	"H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] pci: derive nearby CPUs from device's instead of bus'
 NUMA information

On Mon, 20 Apr 2009 10:47:47 +0200
Andreas Herrmann <andreas.herrmann3@....com> wrote:

> On Fri, Apr 17, 2009 at 12:26:54PM -0700, Yinghai Lu wrote:
> > On Fri, Apr 17, 2009 at 9:21 AM, Ingo Molnar <mingo@...e.hu> wrote:
> > > const struct cpumask * cpumask_of_pcidev(struct pci_dev *dev)
> > > {
> > >        if (dev->numa_node == -1)
> > >                return cpumask_of_pcibus(to_pci_dev(dev)->bus);
> > >
> > >        return cpumask_of_node(dev_to_node(dev));
> > > }
> > >
> > > ? This would work fine in all cases.
> 
> Yes, I think so. That's the general solution w/o additional
> "ifdefing".
> 
> > you are right, dev_to_node(dev) could return -1 on 64bit, if there
> > is no memory on that node.
> 
> Hmm, I thought just in the CONFIG_NUMA=n case -1 is returned.
> 
> During initialization the struct device's numa_node is set to -1 and
> later on the information is inherited from the parent numa_node.
> 
> So what do I miss?

I like the idea of cpumask_of_pcidev(), but it seems like
cpumask_of_pcibus should return the same value.  So if the node is
unassigned or "equadistant" (there's code that treats -1 as both I
think), cpumask_of_pcibus should figure out what the nearest CPUs are
and return that, right?

-- 
Jesse Barnes, Intel Open Source Technology Center
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