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

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Date:	Sat, 08 Aug 2009 00:17:20 +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:
> OK.  The tests were run on a 2.6.29.6 kernel so presumably should
> have included the fix you mentioned.
>   

Yes, but I wanted to emphasize that new platforms sometime need some new
code to handle this kind of things. Some Nehalem-specific changes might
be needed now.

>>>> Is the corresponding local_cpus sysfs file wrong as well ?
>>>>         
>>> All sysfs local_cpus values are the same (00000000,000000ff),
>>> so yes they are also wrong.
>>>       
>> And hyperthreading is enabled, right?
>>     
>
> No, hyperthreading is disabled.  It's a dual quad-core system so there
> are a total of 8 cores, 4 on NUMA node 0 and 4 on NUMA node2.
>   

So numa_node says that the device is close to node 0 while local_cpus
says that it's close to all 8 cores ie close to both node0 and node2
(which may well be wrong as well).

Brice

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