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Date:   Thu, 3 Nov 2016 21:39:11 +0800
From:   Gao Feng <>
To:     Eric Dumazet <>
Cc:     "David S. Miller" <>,
        Cong Wang <>,
        Vijay Pandurangan <>,
        Evan Jones <>,,
        Linux Kernel Network Developers <>
Subject: Re: [PATCH net-next v2 1/1] driver: veth: Refine the statistics codes
 of veth driver

Hi Eric,

On Thu, Nov 3, 2016 at 9:30 PM, Eric Dumazet <> wrote:
> On Thu, 2016-11-03 at 21:03 +0800, wrote:
>> From: Gao Feng <>
>> 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 <>
>> ---
>>  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.

> We did that because there was no point making per-cpu requirements
> bigger, for a counter that is hardly ever updated.
> Do you have a real case where performance dropping packets in a driver
> is needed ?

No, I haven't met the performance issue now.

> At some point we will have to stop dumb percpu explosion, when we have
> 128+ cores per host. Folding all these percpu counters is taking a lot
> of time too.
Ok, I get it. It is designed specially to put the dropped counter as
atomic counter, not percpu.
But I have one question that when put the counters as percpu, and when not?


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