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

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Date:	Tue, 25 Feb 2014 10:13:24 -0500
From:	Prarit Bhargava <prarit@...hat.com>
To:	Alexander Duyck <alexander.h.duyck@...el.com>
CC:	David Laight <David.Laight@...LAB.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 10:10 AM, Alexander Duyck wrote:
> On 02/25/2014 03:00 AM, Prarit Bhargava wrote:
>>
>> 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.
>>
>>
> 
> What should happen if you attempt to remove the CPU the root complex is
> attached to?  Will that trigger a remove via the PCIe complex being removed?

I haven't tried that yet :), but my understanding is that the remove will be
triggered.

P.

> 
> Thanks,
> 
> Alex
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