[ltt-dev] [URCU PATCH] Optimize caa_get_cycles() for PowerPC64

[ltt-dev] [URCU PATCH] Optimize caa_get_cycles() for PowerPC64

[Tulio Magno Quites Machado Filho]

Make caa_get_cycles() read from the Time Base register with only 1 instruction.

Signed-off-by: Tulio Magno Quites Machado Filho <tuliom at linux.vnet.ibm.com>
---
 urcu/arch/ppc.h |   11 +++++++++++
 1 files changed, 11 insertions(+), 0 deletions(-)

diff --git a/urcu/arch/ppc.h b/urcu/arch/ppc.h
index d7317bb..2b606d0 100644
--- a/urcu/arch/ppc.h
+++ b/urcu/arch/ppc.h
@@ -48,10 +48,20 @@ extern "C" {
 		rval;					\
 	})
 
+#define mftb()						\
+	({						\
+		unsigned long long rval;		\
+		asm volatile("mftb %0" : "=r" (rval));	\
+		rval;					\
+	})
+
 typedef unsigned long long cycles_t;
 
 static inline cycles_t caa_get_cycles (void)
 {
+#ifdef __powerpc64__
+	return (cycles_t) mftb();
+#else
 	long h, l;
 
 	for (;;) {
@@ -62,6 +72,7 @@ static inline cycles_t caa_get_cycles (void)
 		if (mftbu() == h)
 			return (((cycles_t) h) << 32) + l;
 	}
+#endif
 }
 
 #ifdef __cplusplus 
-- 
1.7.4.4

[ltt-dev] [URCU PATCH] Optimize caa_get_cycles() for PowerPC64

[Mathieu Desnoyers]

* Tulio Magno Quites Machado Filho (tuliom at linux.vnet.ibm.com) wrote:
> Make caa_get_cycles() read from the Time Base register with only 1 instruction.

Merged,

I did a small coding style change to the patch, turning the
#if/#else/#endif into multiple function implementations rather than
affecting the cody of the same function.

Thanks!

Mathieu

> 
> Signed-off-by: Tulio Magno Quites Machado Filho <tuliom at linux.vnet.ibm.com>
> ---
>  urcu/arch/ppc.h |   11 +++++++++++
>  1 files changed, 11 insertions(+), 0 deletions(-)
> 
> diff --git a/urcu/arch/ppc.h b/urcu/arch/ppc.h
> index d7317bb..2b606d0 100644
> --- a/urcu/arch/ppc.h
> +++ b/urcu/arch/ppc.h
> @@ -48,10 +48,20 @@ extern "C" {
>  		rval;					\
>  	})
>  
> +#define mftb()						\
> +	({						\
> +		unsigned long long rval;		\
> +		asm volatile("mftb %0" : "=r" (rval));	\
> +		rval;					\
> +	})
> +
>  typedef unsigned long long cycles_t;
>  
>  static inline cycles_t caa_get_cycles (void)
>  {
> +#ifdef __powerpc64__
> +	return (cycles_t) mftb();
> +#else
>  	long h, l;
>  
>  	for (;;) {
> @@ -62,6 +72,7 @@ static inline cycles_t caa_get_cycles (void)
>  		if (mftbu() == h)
>  			return (((cycles_t) h) << 32) + l;
>  	}
> +#endif
>  }
>  
>  #ifdef __cplusplus 
> -- 
> 1.7.4.4
> 
> 
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> 

-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com