linux-kernel - Re: [PATCH] irq: Add node_affinity CPU masks for smarter irqbalance hints

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Date:	Mon, 23 Nov 2009 18:05:23 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@...el.com>
Cc:	Yong Zhang <yong.zhang0@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"arjan@...ux.jf.intel.com" <arjan@...ux.jf.intel.com>,
	"davem@...emloft.net" <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH] irq: Add node_affinity CPU masks for smarter
 irqbalance hints

On Mon, 2009-11-23 at 01:36 -0800, Peter P Waskiewicz Jr wrote:

> This mechanism isn't going to be used by any internal kernel mechanism
> for determining interrupt placement or operation.  It's purely something
> that either a driver can modify, or external script (through /proc),
> that irqbalance will make use of.  If irqbalance isn't running, or the
> current version of irqbalance doesn't support reading node_affinity,
> then it won't affect the system's operation.
> 
> If irqbalance does support it, it'll read whatever the supplied mask is,
> and then will try and balance interrupts within that mask.  It will bail
> if the mask is invalid, or won't apply to the running system, just like
> how putting a bogus mask into smp_affinity is ignored.
> 
> If there's something I'm missing beyond this with the two suggestions
> you've made (I looked into those two parameters and tried to draw
> conclusions), please let me know.

I don't see the point in adding it, if the driver wants to set a node
cpu mask it can already do that using the regular smp affinity settings.

Same for userspace.

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