netdev - Re: [PATCH net-next v2 1/1] driver: veth: Refine the statistics codes of veth driver

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Message-Id: <20161103.131810.2042355356026457407.davem@davemloft.net>
Date:   Thu, 03 Nov 2016 13:18:10 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     fgao@...ai8.com
Cc:     eric.dumazet@...il.com, cwang@...pensource.com, vijayp@...ayp.ca,
        ej@...njones.ca, pabeni@...hat.com, netdev@...r.kernel.org
Subject: Re: [PATCH net-next v2 1/1] driver: veth: Refine the statistics
 codes of veth driver

From: Gao Feng <fgao@...ai8.com>
Date: Thu, 3 Nov 2016 22:38:28 +0800

> On Thu, Nov 3, 2016 at 10:31 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
>> On Thu, 2016-11-03 at 21:39 +0800, Gao Feng wrote:
>>> Hi Eric,
>>>
>>> On Thu, Nov 3, 2016 at 9:30 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
>>> > On Thu, 2016-11-03 at 21:03 +0800, fgao@...ai8.com wrote:
>>> >> From: Gao Feng <fgao@...ai8.com>
>>> >>
>>> >> The dropped count of veth is located in struct veth_priv, but other
>>> >> statistics like packets and bytes are in another struct pcpu_vstats.
>>> >> Now keep these three counters in the same struct.
>>> >>
>>> >> Signed-off-by: Gao Feng <fgao@...ai8.com>
>>> >> ---
>>> >>  v2: Use right "peer" instead of "dev";
>>> >>  v1: Initial version
>>> >
>>> > May I ask : Why ?
>>>
>>> Just because I think statistics should be in the same struct.
>>
>> That is not a good reason then.
> 
> Because other net devices put the statistics together.

Organizational "prettyness" is not argument for this change, when the
downsides are fundamentally clear:

1) It is not a fast-path accessed statistic, so the per-cpu'ness is
   not important.

2) We aim to minimize the amount of per-cpu data in the kernel because
   it is expensive.  So when not necessary, as is the case here, we
   do not user per-cpu data.

There are no good reasons to make this change, so I am dropping your
patch.