From: Eric Dumazet <eric.dumazet@gmail.com>
To: Christoph Lameter <cl@linux.com>
Cc: David Miller <davem@davemloft.net>,
linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
netdev@vger.kernel.org, netfilter-devel@vger.kernel.org
Subject: Re: Poll about irqsafe_cpu_add and others
Date: Thu, 17 Mar 2011 19:29:29 +0100 [thread overview]
Message-ID: <1300386569.6315.404.camel@edumazet-laptop> (raw)
In-Reply-To: <alpine.DEB.2.00.1103171245430.16620@router.home>
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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WARNING: multiple messages have this Message-ID (diff)
From: Eric Dumazet <eric.dumazet@gmail.com>
To: Christoph Lameter <cl@linux.com>
Cc: David Miller <davem@davemloft.net>,
linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
netdev@vger.kernel.org, netfilter-devel@vger.kernel.org
Subject: Re: Poll about irqsafe_cpu_add and others
Date: Thu, 17 Mar 2011 19:29:29 +0100 [thread overview]
Message-ID: <1300386569.6315.404.camel@edumazet-laptop> (raw)
Message-ID: <20110317182929.aKEiTlqhEzhsF9_smTD9Q0uGioE9ZtGvIBOqT9szZx8@z> (raw)
In-Reply-To: <alpine.DEB.2.00.1103171245430.16620@router.home>
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
next prev parent reply other threads:[~2011-03-17 18:29 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-03-17 14:23 Poll about irqsafe_cpu_add and others Eric Dumazet
2011-03-17 14:23 ` Eric Dumazet
2011-03-17 14:40 ` Christoph Lameter
2011-03-17 15:14 ` David Miller
2011-03-17 15:14 ` David Miller
2011-03-17 15:18 ` Christoph Lameter
2011-03-17 15:18 ` Christoph Lameter
2011-03-17 16:53 ` Eric Dumazet
2011-03-17 17:46 ` Christoph Lameter
2011-03-17 18:29 ` Eric Dumazet [this message]
2011-03-17 18:29 ` Eric Dumazet
2011-03-17 18:42 ` Christoph Lameter
2011-03-17 18:42 ` Christoph Lameter
2011-03-17 18:55 ` Eric Dumazet
2011-03-17 19:21 ` Christoph Lameter
2011-03-18 6:56 ` Benjamin Herrenschmidt
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