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Subject: Re: svn commit: r301197 - head/sys/dev/xen/netfront
To: =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= <royger@FreeBSD.org>
References: <201606021114.u52BEQqB047172@repo.freebsd.org>
 <2c81e44d-65de-10f0-8837-f23896855150@selasky.org>
 <20160602125422.gmdsueoeu5fiiec5@mac>
Cc: src-committers@freebsd.org, svn-src-all@freebsd.org,
 svn-src-head@freebsd.org
From: Hans Petter Selasky <hps@selasky.org>
Message-ID: <c8ef340a-e3d3-af3e-d45c-eedf4183750b@selasky.org>
Date: Thu, 2 Jun 2016 15:01:03 +0200
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On 06/02/16 14:54, Roger Pau Monné wrote:
> On Thu, Jun 02, 2016 at 01:19:56PM +0200, Hans Petter Selasky wrote:
>> On 06/02/16 13:14, Roger Pau Monné wrote:
>>> +		callout_reset(&rxq->rx_refill, hz/10, xn_alloc_rx_buffers_callout,
>>> +		    rxq);
>>
>> Maybe use callout_reset_curcpu() to take advantage of callout's SMP
>> capabilities ?
>
> Yes, that's fine. But what's the benefit of it? I don't really care whether
> the callout is run on the current CPU or not. Is callout_reset_curcpu
> cheaper than callout_reset?
>

Hi,

It is maybe not cheaper, but it will distribute the load of the 
xn_alloc_rx_buffers_callout() callback, to the current CPU calling 
callout_reset_curcpu(). Else xn_alloc_rx_buffers_callout() will always 
be called from callback thread zero.

--HPS