Re: Intel Memory Ordering White Paper

Nick Piggin
2007-09-07T22:57:35Z

[-- Attachment #1: Type: text/plain, Size: 374 bytes --]

On Saturday 08 September 2007 08:26, Jesse Barnes wrote:
> FYI, we just released a new white paper describing memory ordering for
> Intel processors:
> http://developer.intel.com/products/processor/manuals/index.htm
>
> Should help answer some questions about some of the ordering primitives
> we use on i386 and x86_64.

So, can we finally noop smp_rmb and smp_wmb on x86?

[-- Attachment #2: x86-barrier-opt.patch --]
[-- Type: text/x-diff, Size: 1011 bytes --]

Index: linux-2.6/include/asm-i386/system.h
===================================================================
--- linux-2.6.orig/include/asm-i386/system.h
+++ linux-2.6/include/asm-i386/system.h
@@ -286,7 +286,7 @@ static inline unsigned long get_limit(un

#ifdef CONFIG_SMP
#define smp_mb() mb()
-#define smp_rmb() rmb()
+#define smp_rmb() barrier()
#define smp_wmb() wmb()
#define smp_read_barrier_depends() read_barrier_depends()
#define set_mb(var, value) do { (void) xchg(&var, value); } while (0)
Index: linux-2.6/include/asm-x86_64/system.h
===================================================================
--- linux-2.6.orig/include/asm-x86_64/system.h
+++ linux-2.6/include/asm-x86_64/system.h
@@ -141,8 +141,8 @@ static inline void write_cr8(unsigned lo

#ifdef CONFIG_SMP
#define smp_mb() mb()
-#define smp_rmb() rmb()
-#define smp_wmb() wmb()
+#define smp_rmb() barrier()
+#define smp_wmb() barrier()
#define smp_read_barrier_depends() do {} while(0)
#else
#define smp_mb() barrier()