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

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Date:	Sat, 08 Aug 2009 07:08:20 -0400
From:	Andrew Gallatin <gallatin@...i.com>
To:	Bill Fink <billfink@...dspring.com>
CC:	Brice Goglin <Brice.Goglin@...ia.fr>,
	Linux Network Developers <netdev@...r.kernel.org>,
	Yinghai Lu <yhlu.kernel@...il.com>
Subject: Re: Receive side performance issue with multi-10-GigE and NUMA

Bill Fink wrote:
 > On Fri, 07 Aug 2009, Andrew Gallatin wrote:
 >
 >> Bill Fink wrote:
 >>
 >>> All sysfs local_cpus values are the same (00000000,000000ff),
 >>> so yes they are also wrong.
 >> How were you handling IRQ binding?  If local_cpus is wrong,
 >> the irqbalance will not be able to make good decisions about
 >> where to bind the NICs' IRQs.  Did you try manually binding
 >> each NICs's interrupt to a separate CPU on the correct node?
 >
 > Yes, all the NIC IRQs were bound to a CPU on the local NUMA node,
 > and the nuttcp application had its CPU affinity set to the same
 > CPU with its memory affinity bound to the same local NUMA node.
 > And the irqbalance daemon wasn't running.

I must be misunderstanding something.  I had thought that
alloc_pages() on NUMA would wind up doing alloc_pages_current(), which
would allocate based on default policy which (if not interleaved)
should allocate from the current NUMA node.  And since restocking the
RX ring happens from a the driver's NAPI softirq context, then it
should always be restocking on the same node the memory is destined to
be consumed on.

Do I just not understand how alloc_pages() works on NUMA?

Thanks,

Drew

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