netdev - Re: [Xen-devel] [PATCH 1/8] netback: don't bind kthread to cpu

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Message-ID: <51360452.5070200@citrix.com>
Date:	Tue, 5 Mar 2013 14:42:26 +0000
From:	David Vrabel <david.vrabel@...rix.com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
CC:	Wei Liu <wei.liu2@...rix.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"annie.li@...cle.com" <annie.li@...cle.com>,
	Ian Campbell <Ian.Campbell@...rix.com>,
	"xen-devel@...ts.xen.org" <xen-devel@...ts.xen.org>
Subject: Re: [Xen-devel] [PATCH 1/8] netback: don't bind kthread to cpu

On 05/03/13 13:56, Konrad Rzeszutek Wilk wrote:
> On Tue, Mar 05, 2013 at 01:30:10PM +0000, Wei Liu wrote:
>> On Mon, 2013-03-04 at 20:51 +0000, Konrad Rzeszutek Wilk wrote:
>>> On Fri, Feb 15, 2013 at 04:00:02PM +0000, Wei Liu wrote:
>>>> The initialization process makes an assumption that the online cpus are
>>>> numbered from 0 to xen_netbk_group_nr-1,  which is not always true.
>>>
>>> And xen_netbk_group_nr is num_online_cpus()?
>>>
>>
>> Yes.
>>
>>> So under what conditions does this change? Is this when the CPU hotplug
>>> is involved and the CPUs go offline? In which case should there be a
>>
>> Yes, the hotplug path.
>>
>>> CPU hotplug notifier to re-bind the workers are appropiate?
> 
> ?
> Can't that option be explored?

I'm not sure binding netback threads to particular VCPUs is useful
without also binding the events to the corresponding VCPUs.

I would hope that the scheduler would tend to the correct behavior if
threads aren't bound, anyway.

David
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