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Message-ID: <4B0BF10C.6070609@linux.intel.com>
Date: Tue, 24 Nov 2009 06:43:24 -0800
From: Arjan van de Ven <arjan@linux.intel.com>
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To: Peter Zijlstra <peterz@infradead.org>
CC: Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@intel.com>,
       Yong Zhang <yong.zhang0@gmail.com>,
       "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
       "arjan@linux.jf.intel.com" <arjan@linux.jf.intel.com>,
       "davem@davemloft.net" <davem@davemloft.net>,
       "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
       Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH] irq: Add node_affinity CPU masks for smarter irqbalance
 hints
References: <20091123064630.7385.30498.stgit@ppwaskie-hc2.jf.intel.com>	 <2674af740911222332i65c0d066h79bf2c1ca1d5e4f0@mail.gmail.com>	 <1258968980.2697.9.camel@ppwaskie-mobl2> <1258995923.4531.715.camel@laptop>	 <Pine.WNT.4.64.0911231529240.10056@ppwaskie-MOBL2.amr.corp.intel.com>	 <1259051902.4531.1053.camel@laptop>	 <1259053156.2631.21.camel@ppwaskie-mobl2> <1259053736.4531.1097.camel@laptop>
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Peter Zijlstra wrote:
> On Tue, 2009-11-24 at 00:59 -0800, Peter P Waskiewicz Jr wrote:
>>> This all sounds backwards.. we've got a perfectly functional interface
>>> for affinity -- which people object to being used for some reason. So
>>> you add another interface on top, and that is ok?
>>>
>> But it's not functional.  If I set the affinity in smp_affinity, then
>> irqbalance will override it 10 seconds later. 
> 
> And here I was thinking the kernel round-robins IRQ delivery on the mask
> specified there. 

the kernel does no such thing, nor has code to do so.

 > Are you talking about some daft userspace thing that
> writes into the irq smp_affinity to effect irq balancing?

thanks ;)