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

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Message-ID: <20130304205154.GB16762@phenom.dumpdata.com>
Date:	Mon, 4 Mar 2013 15:51:54 -0500
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	Wei Liu <wei.liu2@...rix.com>
Cc:	xen-devel@...ts.xen.org, netdev@...r.kernel.org,
	ian.campbell@...rix.com, annie.li@...cle.com
Subject: Re: [PATCH 1/8] netback: don't bind kthread to cpu

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()?

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
CPU hotplug notifier to re-bind the workers are appropiate?

> 
> As we only need a pool of worker threads, simply don't bind them to specific
> cpus.

OK. Is there another method of doing this? Are there patches to make the thread
try to be vCPU->guest affinite?

> 
> Signed-off-by: Wei Liu <wei.liu2@...rix.com>
> ---
>  drivers/net/xen-netback/netback.c |    2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
> index 3ae49b1..db8d45a 100644
> --- a/drivers/net/xen-netback/netback.c
> +++ b/drivers/net/xen-netback/netback.c
> @@ -1729,8 +1729,6 @@ static int __init netback_init(void)
>  			goto failed_init;
>  		}
>  
> -		kthread_bind(netbk->task, group);
> -
>  		INIT_LIST_HEAD(&netbk->net_schedule_list);
>  
>  		spin_lock_init(&netbk->net_schedule_list_lock);
> -- 
> 1.7.10.4
> 
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