Re: [Xen-devel] [PATCH] x86: adjust placement of pause insn in _raw_spin_lock()

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

Ah, I suppose it reduce lock acquisition latency slightly. I'll apply it.

 -- Keir

On 8/8/08 14:12, "Keir Fraser" <keir.fraser@xxxxxxxxxxxxx> wrote:

> Why?
> 
>  -- Keir
> 
> On 8/8/08 13:49, "Jan Beulich" <jbeulich@xxxxxxxxxx> wrote:
> 
>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>
>> 
>> Index: 2008-08-06/xen/include/asm-x86/spinlock.h
>> ===================================================================
>> --- 2008-08-06.orig/xen/include/asm-x86/spinlock.h 2007-09-10
>> 09:59:37.000000000 +0200
>> +++ 2008-08-06/xen/include/asm-x86/spinlock.h 2008-08-07 12:36:13.000000000
>> +0200
>> @@ -23,8 +23,8 @@ static inline void _raw_spin_lock(spinlo
>>          "1:  lock; decb %0         \n"
>>          "    js 2f                 \n"
>>          ".section .text.lock,\"ax\"\n"
>> -        "2:  cmpb $0,%0            \n"
>> -        "    rep; nop              \n"
>> +        "2:  rep; nop              \n"
>> +        "    cmpb $0,%0            \n"
>>          "    jle 2b                \n"
>>          "    jmp 1b                \n"
>>          ".previous"
>> 
>> 
>> 
>> 
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