netdev - Re: Receive side performance issue with multi-10-GigE and NUMA

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Date:	Fri, 07 Aug 2009 23:18:12 +0200
From:	Brice Goglin <Brice.Goglin@...ia.fr>
To:	Bill Fink <billfink@...dspring.com>
CC:	Linux Network Developers <netdev@...r.kernel.org>,
	Yinghai Lu <yhlu.kernel@...il.com>, gallatin@...i.com
Subject: Re: Receive side performance issue with multi-10-GigE and NUMA

Bill Fink wrote:
> This could be because I discovered that if I did:
>
> 	find /sys -name numa_node -exec grep . {} /dev/null \;
>
> that the numa_node associated with all the PCI devices was always 0,
> and if IIUC then I believe some of the PCI devices should have been
> associated with NUMA node 2.  Perhaps this is what is causing all
> the memory pages allocated by the myri10ge driver to be on NUMA
> node 0, and thus causing the major performance issue.
>   

I've seen some cases in the past where numa_node was always 0 on
quad-Opteron machines with a PCI bus on node 1. IIRC it got fixed in
later kernels thanks to patches from Yinghai Lu (CC'ed).
Is the corresponding local_cpus sysfs file wrong as well ?
Maybe your kernel doesn't properly handle the NUMA location of PCI
devices on Nehalem machines yet?

Brice

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