* [PATCH] x86: adjust placement of pause insn in _raw_spin_lock()
@ 2008-08-08 12:49 Jan Beulich
2008-08-08 13:12 ` Keir Fraser
0 siblings, 1 reply; 4+ messages in thread
From: Jan Beulich @ 2008-08-08 12:49 UTC (permalink / raw)
To: xen-devel
Signed-off-by: Jan Beulich <jbeulich@novell.com>
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"
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH] x86: adjust placement of pause insn in _raw_spin_lock()
2008-08-08 12:49 [PATCH] x86: adjust placement of pause insn in _raw_spin_lock() Jan Beulich
@ 2008-08-08 13:12 ` Keir Fraser
2008-08-08 14:02 ` Keir Fraser
2008-08-08 14:12 ` [PATCH] x86: adjust placement of pause insn in_raw_spin_lock() Jan Beulich
0 siblings, 2 replies; 4+ messages in thread
From: Keir Fraser @ 2008-08-08 13:12 UTC (permalink / raw)
To: Jan Beulich, xen-devel
Why?
-- Keir
On 8/8/08 13:49, "Jan Beulich" <jbeulich@novell.com> wrote:
> Signed-off-by: Jan Beulich <jbeulich@novell.com>
>
> 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"
>
>
>
>
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xensource.com
> http://lists.xensource.com/xen-devel
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] x86: adjust placement of pause insn in _raw_spin_lock()
2008-08-08 13:12 ` Keir Fraser
@ 2008-08-08 14:02 ` Keir Fraser
2008-08-08 14:12 ` [PATCH] x86: adjust placement of pause insn in_raw_spin_lock() Jan Beulich
1 sibling, 0 replies; 4+ messages in thread
From: Keir Fraser @ 2008-08-08 14:02 UTC (permalink / raw)
To: Jan Beulich, xen-devel
Ah, I suppose it reduce lock acquisition latency slightly. I'll apply it.
-- Keir
On 8/8/08 14:12, "Keir Fraser" <keir.fraser@eu.citrix.com> wrote:
> Why?
>
> -- Keir
>
> On 8/8/08 13:49, "Jan Beulich" <jbeulich@novell.com> wrote:
>
>> Signed-off-by: Jan Beulich <jbeulich@novell.com>
>>
>> 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"
>>
>>
>>
>>
>> _______________________________________________
>> Xen-devel mailing list
>> Xen-devel@lists.xensource.com
>> http://lists.xensource.com/xen-devel
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] x86: adjust placement of pause insn in_raw_spin_lock()
2008-08-08 13:12 ` Keir Fraser
2008-08-08 14:02 ` Keir Fraser
@ 2008-08-08 14:12 ` Jan Beulich
1 sibling, 0 replies; 4+ messages in thread
From: Jan Beulich @ 2008-08-08 14:12 UTC (permalink / raw)
To: Keir Fraser; +Cc: xen-devel
That's the way it's done elsewhere and it's recommended (i.e. pause
immediately preceding the memory reference of the possibly contended
location). Jan
>>> Keir Fraser <keir.fraser@eu.citrix.com> 08.08.08 15:12 >>>
Why?
-- Keir
On 8/8/08 13:49, "Jan Beulich" <jbeulich@novell.com> wrote:
> Signed-off-by: Jan Beulich <jbeulich@novell.com>
>
> 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"
>
>
>
>
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xensource.com
> http://lists.xensource.com/xen-devel
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2008-08-08 14:12 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz follow: Atom feed
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2008-08-08 12:49 [PATCH] x86: adjust placement of pause insn in _raw_spin_lock() Jan Beulich
2008-08-08 13:12 ` Keir Fraser
2008-08-08 14:02 ` Keir Fraser
2008-08-08 14:12 ` [PATCH] x86: adjust placement of pause insn in_raw_spin_lock() Jan Beulich
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