Re: Poll about irqsafe_cpu_add and others

From: Eric Dumazet
Date: Thu Mar 17 2011 - 14:30:43 EST

Le jeudi 17 mars 2011 Ã 12:46 -0500, Christoph Lameter a Ãcrit :
> 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

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at