netdev - Re: [PATCH] x86/PCI: initialize PCI bus node numbers early

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Date:	Tue, 14 Jul 2009 08:47:31 -0700
From:	Jesse Barnes <jbarnes@...tuousgeek.org>
To:	Jesse Brandeburg <jesse.brandeburg@...il.com>
Cc:	Yinghai Lu <yinghai@...nel.org>, linux-kernel@...r.kernel.org,
	NetDEV list <netdev@...r.kernel.org>, ak@...ux.intel.com,
	matthew@....cx
Subject: Re: [PATCH] x86/PCI: initialize PCI bus node numbers early

On Tue, 14 Jul 2009 00:41:30 -0700
Jesse Brandeburg <jesse.brandeburg@...il.com> wrote:

> On Fri, Jul 10, 2009 at 2:06 PM, Jesse
> Barnes<jbarnes@...tuousgeek.org> wrote:
> > From 2b51fba93f7b2dabf453a74923a9a217611ebc1a Mon Sep 17 00:00:00
> > 2001 From: Jesse Barnes <jbarnes@...tuousgeek.org>
> > Date: Fri, 10 Jul 2009 14:04:30 -0700
> > Subject: [PATCH] x86/PCI: initialize PCI bus node numbers early
> >
> > The current mp_bus_to_node array is initialized only by AMD specific
> > code, since AMD platforms have registers that can be used for
> > determining mode numbers.  On new Intel platforms it's necessary to
> > initialize this array as well though, otherwise all PCI node numbers
> > will be 0, when in fact they should be -1 (indicating that I/O isn't
> > tied to any particular node).
> >
> > So move the mp_bus_to_node code into the common PCI code, and
> > initialize it early with a default value of -1.  This may be
> > overridden later by arch code (e.g. the AMD code).
> >
> > With this change, PCI consistent memory and other node specific
> > allocations (e.g. skbuff allocs) should occur on the "current" node.
> > If, for performance reasons, applications want to be bound to
> > specific nodes, they should open their devices only after being
> > pinned to the CPU where they'll run, for maximum locality.
> >
> > Acked-by: Yinghai Lu <yinghai@...nel.org>
> > Tested-by: Jesse Brandeburg <jesse.brandeburg@...il.com>
> > Signed-off-by: Jesse Barnes <jbarnes@...tuousgeek.org>
> 
> I can confirm this works, aside from the MSI-X interrupt migration
> instability (panics) that I believe are unrelated since they happen
> without this patch.
> 
> I also see a pretty nice performance boost by running with this change
> on a 5520 motherboard, with an 82599 10GbE forwarding packets, esp
> with interrupt affinity set correctly.
> 
> I'd like to see this applied if at all possible, I think it is really
> hampering I/O traffic performance due to limiting all network (among
> others) memory allocation to one of the two numa nodes.

Ok, thanks for testing.  I've pushed it to my linux-next branch.

-- 
Jesse Barnes, Intel Open Source Technology Center
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