linux-kernel - Re: [PATCH v6] x86/apic: limit irq affinity

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Date:	Wed, 25 Nov 2009 07:40:33 -0800
From:	Arjan van de Ven <arjan@...radead.org>
To:	ebiederm@...ssion.com (Eric W. Biederman)
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Dimitri Sivanich <sivanich@....com>,
	Ingo Molnar <mingo@...e.hu>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	Yinghai Lu <yinghai@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	David Miller <davem@...emloft.net>,
	Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@...el.com>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH v6] x86/apic: limit irq affinity

On Tue, 24 Nov 2009 09:41:18 -0800
ebiederm@...ssion.com (Eric W. Biederman) wrote:
> Oii.
> 
> I don't think it is bad to export information to applications like
> irqbalance.
> 
> I think it pretty horrible that one of the standard ways I have heard
> to improve performance on 10G nics is to kill irqbalance.

irqbalance does not move networking irqs; if it does there's something
evil going on in the system. But thanks for the bugreport ;)


> Guys.  Migrating an irq from one cpu to another while the device is
> running without dropping interrupts is hard.

no it isn't; we've been doing it for years.


> I think the irq scheduler is the only scheduler (except for batch
> jobs) that we don't put in the kernel.  It seems to me that if we are
> going to go to all of the trouble to rewrite the generic code to
> better support irqbalance because we are having serious irqbalance
> problems, it will be less effort to suck irqbalance into the kernel
> along with everything else.

we had that; it didn't work.
what I'm asking for is for the kernel to expose the numa information;
right now that is the piece that is missing.

-- 
Arjan van de Ven 	Intel Open Source Technology Centre
For development, discussion and tips for power savings, 
visit http://www.lesswatts.org
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