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Date: Wed, 01 Apr 2009 20:47:41 +0200
From: Eric Dumazet <dada1@cosmosbay.com>
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To: Jeremy Fitzhardinge <jeremy@goop.org>
CC: Ingo Molnar <mingo@elte.hu>, Tejun Heo <htejun@gmail.com>,
       linux kernel <linux-kernel@vger.kernel.org>,
       Linux Netdev List <netdev@vger.kernel.org>,
       Joe Perches <joe@perches.com>, Rusty Russell <rusty@rustcorp.com.au>
Subject: Re: [PATCH] x86: percpu_to_op() misses memory and flags clobbers
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Jeremy Fitzhardinge a écrit :
> Eric Dumazet wrote:
>> +#define percpu_inc(var)        percpu_to_op0("inc", per_cpu__##var)
>> +#define percpu_dec(var)        percpu_to_op0("dec", per_cpu__##var)
>>   
> 
> There's probably not a lot of value in this.  The Intel and AMD
> optimisation guides tend to deprecate inc/dec in favour of using
> add/sub, because the former can cause pipeline stalls due to its partial
> flags update.
> 
>    J

Sure, but this saves one byte per call, this is probably why we still use
inc/dec in so many places...