linux-kernel - Re: [cpuops cmpxchg V2 5/5] cpuops: Use cmpxchg for xchg to avoid lock semantics

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Date:	Tue, 14 Dec 2010 17:06:55 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Tejun Heo <tj@...nel.org>
CC:	Christoph Lameter <cl@...ux.com>,
	Eric Dumazet <eric.dumazet@...il.com>,
	akpm@...ux-foundation.org, Pekka Enberg <penberg@...helsinki.fi>,
	linux-kernel@...r.kernel.org,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Subject: Re: [cpuops cmpxchg V2 5/5] cpuops: Use cmpxchg for xchg to avoid
 lock semantics

On 12/14/2010 09:29 AM, Tejun Heo wrote:
> Hello,
> 
> On 12/14/2010 06:22 PM, H. Peter Anvin wrote:
>> On 12/14/2010 09:19 AM, Christoph Lameter wrote:
>>>>
>>>> Is it genuinely faster to do the pre-load mov, or can we drop that too?
>>>>  My guess would be that yes it is, but if it happens not to be it would
>>>> be nice to reduce the code size.
>>>
>>> Dropping the load increases the cycle count from 11 to 16.
>>
>> Great, that answers that!  I'll pick up the patch hopefully today (I'm
>> finally ramping back up on arch/x86 again after having been diverted to
>> an internal project for a while...)
> 
> How do you want to route these?  All patches before this series is
> already in the percpu tree.  I can pull the generic bits and leave out
> the x86 bits so that x86 tree can pull in percpu bits and then put x86
> stuff on top of it.  If you wanna go that way, I would drop all x86
> related patches from the previous patchsets too.
> 

It's probably easiest if you just add them with my Acked-by: then.
Alternatively, I could pick them up so they go into -tip and the tip
test machinery.

	-hpa
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