Experiments with the netperf benchmark indicated that the size selecting
VMX-based copies in __copy_tofrom_user_power7() was suboptimal on POWER8.
Measurements showed that parity was in the neighbourhood of 3328 bytes,
rather than greater than 4096. The change gives a 1.5-2.0% improvement in
performance for 4096-byte buffers, reducing the relative time spent in
__copy_tofrom_user_power7() from approximately 7% to approximately 5% in
the TCP_RR benchmark.
Signed-off-by: Andrew Jeffery <and...@aj.id.au>
---
arch/powerpc/lib/copyuser_power7.S | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/lib/copyuser_power7.S
b/arch/powerpc/lib/copyuser_power7.S
index a24b4039352c..706b7cc19846 100644
--- a/arch/powerpc/lib/copyuser_power7.S
+++ b/arch/powerpc/lib/copyuser_power7.S
@@ -82,14 +82,14 @@
_GLOBAL(__copy_tofrom_user_power7)
#ifdef CONFIG_ALTIVEC
cmpldi r5,16
- cmpldi cr1,r5,4096
+ cmpldi cr1,r5,3328
std r3,-STACKFRAMESIZE+STK_REG(R31)(r1)
std r4,-STACKFRAMESIZE+STK_REG(R30)(r1)
std r5,-STACKFRAMESIZE+STK_REG(R29)(r1)
blt .Lshort_copy
- bgt cr1,.Lvmx_copy
+ bge cr1,.Lvmx_copy
#else
cmpldi r5,16
--
2.9.3
