netdev - Re: [PATCH][net-next] openvswitch: change the data type of error status to atomic_long

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Date:	Tue, 9 Sep 2014 08:29:56 +0800
From:	Li RongQing <roy.qing.li@...il.com>
To:	Pravin Shelar <pshelar@...ira.com>
Cc:	netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH][net-next] openvswitch: change the data type of error
 status to atomic_long_t

On Tue, Sep 9, 2014 at 6:26 AM, Pravin Shelar <pshelar@...ira.com> wrote:
> On Sun, Sep 7, 2014 at 2:24 AM, Li RongQing <roy.qing.li@...il.com> wrote:
>> On Sun, Sep 7, 2014 at 11:44 AM, Pravin Shelar <pshelar@...ira.com> wrote:
>>>> The operation of atomic maybe faster than spin lock.
>>>
>>> What is reason for this change?
>>
>> 1.  The operation of atomic maybe faster than spin lock
>> 2.  I did not find that tx_dropped/tx_error/.. is protected by spin
>> lock under net dir,
>> sometime tx_dropped is atomic_long_t; sometime it is percpu variable;
>> sometime it is
>> u64,but does not need to protect.
>>
>
> These are error counter and the access is not performance sensitive
> code. So I do not see obvious need to optimize it. Do you have any
> performance number for this patch?


I have no performance number, and did not know how to get the performance
number, since I did not know how to trigger the error packet continually.

But I think  atomic is suitable for this condition, it maybe
over-skill to use a spin
lock to protect a single variable, and using atomic can save a spin lock space.


-Roy
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