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SubjectRe: Poll about irqsafe_cpu_add and others
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Le jeudi 17 mars 2011 à 12:46 -0500, Christoph Lameter a écrit :
> On Thu, 17 Mar 2011, Eric Dumazet wrote:
>
> > When we know we run from BH context, we can use __this_cpu_inc(), but if
> > we dont know or run from user/process context, we would need irqsafe_inc
> > variant.
>
> If the BH context is the only one where we care about performance then its
> ok I would think.

Hmm... yes.

By the way, I noticed :

DECLARE_PER_CPU(u64, xt_u64);
__this_cpu_add(xt_u64, 2) translates to following x86_32 code :

mov $xt_u64,%eax
add %fs:0x0,%eax
addl $0x2,(%eax)
adcl $0x0,0x4(%eax)


I wonder why we dont use :

addl $0x2,%fs:xt_u64
addcl $0x0,%fs:xt_u64+4



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