netdev - Re: [PATCH 0/2] ixgbe, fix numa issues

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Date:	Tue, 25 Feb 2014 06:00:46 -0500
From:	Prarit Bhargava <prarit@...hat.com>
To:	David Laight <David.Laight@...LAB.COM>
CC:	Alexander Duyck <alexander.h.duyck@...el.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
	Jesse Brandeburg <jesse.brandeburg@...el.com>,
	Bruce Allan <bruce.w.allan@...el.com>,
	Carolyn Wyborny <carolyn.wyborny@...el.com>,
	Don Skidmore <donald.c.skidmore@...el.com>,
	Greg Rose <gregory.v.rose@...el.com>,
	John Ronciak <john.ronciak@...el.com>,
	Mitch Williams <mitch.a.williams@...el.com>,
	"David S. Miller" <davem@...emloft.net>,
	"nhorman@...hat.com" <nhorman@...hat.com>,
	"agospoda@...hat.com" <agospoda@...hat.com>,
	"e1000-devel@...ts.sourceforge.net" 
	<e1000-devel@...ts.sourceforge.net>
Subject: Re: [PATCH 0/2] ixgbe, fix numa issues



On 02/25/2014 05:21 AM, David Laight wrote:
> From: Prarit Bhargava
> ...
>> What has caused that check to be necessary is that the ixgbe driver is now
>> allocating so many interrupts that on large systems which full sockets are taken
>> in and out of service, it is possible that there are not enough empty vectors
>> for all the irqs on a down'd cpu.  IMO what the ixgbe driver is effectively
>> doing is starving the system of resources.  If I rmmod the ixgbe driver (and
>> free it's irqs of course) I have no problem in taking all cpus except 1 out of
>> service.
> 
> If I read that correctly it looks as though ixgbe should be allocating
> a number of interrupts on each cpu - for the interrupts it wants to take
> on that cpu.

Yes, the code currently does it.

> 
> Then taking the cpu out of service would 'just' require that the interrupts
> that are tied to that cpu be removed first?

Yes, that would happen with a cpu notifier (I've already written a simple dummy
one that just printk's when called).  I started to implement a single queue
teardown but hit some of these enumeration issues.  I'd like to fix these first
and then get to the teardown.

P.

> 
> 	David
> 
> 
> 
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