Re: [PATCH][2.5][RFT] sfence wmb for K7,P3,VIAC3-2(?)

From: Zwane Mwaikambo (zwane@linuxpower.ca)
Date: Tue Apr 01 2003 - 11:07:21 EST

On Tue, 1 Apr 2003, Andi Kleen wrote:

> Yes, you're correct. It was SSE1, not SSE2.
>
> The problem Zwane encountered is that early Athlons don't support SSE1,
> only XP+ do

hmm wouldn't they illegal op? Some tested this on an Athlon 600.

> To use it he would need an a new CONFIG split for Athlon XP and earlier
> Athlon. iirc it didn't make much difference on the athlon anyways which
> has quite fast locked operations on exclusive cachelines - sfence seems
> to be more useful on P4.

How about this instead then;

Index: linux-2.5.66/arch/i386/Kconfig
===================================================================
RCS file: /build/cvsroot/linux-2.5.66/arch/i386/Kconfig,v
retrieving revision 1.1.1.1
diff -u -p -B -r1.1.1.1 Kconfig
--- linux-2.5.66/arch/i386/Kconfig 24 Mar 2003 23:40:26 -0000 1.1.1.1
+++ linux-2.5.66/arch/i386/Kconfig 1 Apr 2003 16:02:46 -0000
@@ -368,6 +368,11 @@ config X86_PREFETCH
         depends on MPENTIUMIII || MPENTIUM4 || MVIAC3_2
         default y
 
+config X86_USE_SFENCE
+ bool
+ depends on MPENTIUM4
+ default y
+
 config X86_SSE2
         bool
         depends on MK8 || MPENTIUM4
Index: linux-2.5.66/include/asm-i386/system.h
===================================================================
RCS file: /build/cvsroot/linux-2.5.66/include/asm-i386/system.h,v
retrieving revision 1.1.1.1
diff -u -p -B -r1.1.1.1 system.h
--- linux-2.5.66/include/asm-i386/system.h 24 Mar 2003 23:40:20 -0000 1.1.1.1
+++ linux-2.5.66/include/asm-i386/system.h 1 Apr 2003 16:03:50 -0000
@@ -355,11 +355,15 @@ static inline unsigned long __cmpxchg(vo
 
 #define read_barrier_depends() do { } while(0)
 
+#ifdef CONFIG_X86_USE_SFENCE
+#define wmb() __asm__ __volatile__ ("sfence;": : :"memory")
+#else
 #ifdef CONFIG_X86_OOSTORE
 #define wmb() __asm__ __volatile__ ("lock; addl $0,0(%%esp)": : :"memory")
 #else
 #define wmb() __asm__ __volatile__ ("": : :"memory")
 #endif
+#endif /* CONFIG_USE_SFENCE */
 
 #ifdef CONFIG_SMP
 #define smp_mb() mb() 

-- 
function.linuxpower.ca
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