From mboxrd@z Thu Jan  1 00:00:00 1970
From: Wei Liu <wei.liu2@citrix.com>
Subject: Re: [PATCH net-next 2/3] xen-netback: switch to per-cpu
 scratch space
Date: Fri, 24 May 2013 13:31:30 +0100
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To: David Vrabel <david.vrabel@citrix.com>
Cc: netdev@vger.kernel.org, konrad.wilk@oracle.com, Wei Liu <wei.liu2@citrix.com>, ian.campbell@citrix.com, xen-devel@lists.xen.org
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On Fri, May 24, 2013 at 01:24:41PM +0100, David Vrabel wrote:
> On 24/05/13 11:32, Wei Liu wrote:
> > There are maximum nr_onlie_cpus netback threads running. We can make use of
> > per-cpu scratch space to reduce the size of buffer space when we move to 1:1
> > model.
> 
> How much memory does this actually save?  At first glance the savings
> don't seem worth it for the extra complexity wrt hotplugged VCPUs etc.
> 

It would not save any for the old model netback. But if we switch to 1:1
model the saving depends on how many vifs you run.

This can be calculated by:
(nr_vifs - nr_cpus) * sizeof(scratch space)


Wei.

> David