linux-kernel - Re: What is the difference between percpu_xxx and this_cpu

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Message-ID: <4E6EF4AE.4030503@intel.com>
Date:	Tue, 13 Sep 2011 14:14:06 +0800
From:	Huang Ying <ying.huang@...el.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	Tejun Heo <tj@...nel.org>,
	Christoph Lameter <cl@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: What is the difference between percpu_xxx and this_cpu_xxx?

Hi, Eric,

On 09/13/2011 02:11 PM, Eric Dumazet wrote:
> Le mardi 13 septembre 2011 à 12:28 +0800, Huang Ying a écrit :
>> Hi,
>>
>> If my understanding was correct, from the kernel source code, it appears
>> that percpu_xxx and this_cpu_xxx have the same semantics and
>> implementation in effect, haven’t them?
>>
>> If so, why do we need two API for the same thing?
> 
> History mostly, and transition.
> 
> percpu_inc() was an x86 only thing
> 
> __get_cpu_var(var)++ -> percpu_inc(var) -> this_cpu_inc(var)

Thanks for clarification.  Is there someone working on the transition?
Is that possible to translate most percpu_xxx to this_cpu_xxx blindly?

Best Regards,
Huang Ying
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