To: Arjan van de Ven <arjan@infradead.org>
Cc: Brice Goglin <Brice.Goglin@inria.fr>, LKML <linux-kernel@vger.kernel.org>,
       netdev@vger.kernel.org
Subject: Re: [RFC] export irq_set/get_affinity() for multiqueue network drivers
From: Andi Kleen <andi@firstfloor.org>
References: <48B708E1.4070001@inria.fr>
	<20080829055023.07966b4a@infradead.org>
Date: Fri, 29 Aug 2008 18:48:12 +0200
In-Reply-To: <20080829055023.07966b4a@infradead.org> (Arjan van de Ven's message of "Fri, 29 Aug 2008 05:50:23 -0700")
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Arjan van de Ven <arjan@infradead.org> writes:

> On Thu, 28 Aug 2008 22:21:53 +0200
> Brice Goglin <Brice.Goglin@inria.fr> wrote:
>
>> Hello,
>> 
>> Is there any way to setup IRQ masks from within a driver? myri10ge
>> currently relies on an external script (writing in
>> /proc/irq/*/smp_affinity) to bind each queue/MSI-X to a different
>> processor. By default, Linux will either:
>> * round-robin the interrupts (killing the benefit of DCA for instance)
>> * put all IRQs on the same CPU (killing much of th
>
> * do the right thing with the userspace irq balancer

It probably also needs to be hooked up the sched_mc_power_savings
When the switch is on the interrupts shouldn't be spread out over
that many sockets.

Does it need callbacks to change the interrupts when that variable
changes?

Also I suspect handling SMT explicitely is a good idea. e.g. I would
always set the affinity to all thread siblings in a core, not 
just a single one, because context switch is very cheap between them.

-Andi

-- 
ak@linux.intel.com
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