I ran some tests to compare hash_64 using shifts and multiplies.
The results:
POWER6: ~2x slower
POWER7: ~2x faster
POWER8: ~2x faster
Now we have a proper config option, select
CONFIG_ARCH_HAS_FAST_MULTIPLIER on POWER7 and POWER8.
Signed-off-by: Anton Blanchard <an...@samba.org>
---
Index: b/arch/powerpc/platforms/Kconfig.cputype
===================================================================
--- a/arch/powerpc/platforms/Kconfig.cputype
+++ b/arch/powerpc/platforms/Kconfig.cputype
@@ -116,10 +116,12 @@ config POWER6_CPU
config POWER7_CPU
bool "POWER7"
depends on PPC_BOOK3S_64
+ select ARCH_HAS_FAST_MULTIPLIER
config POWER8_CPU
bool "POWER8"
depends on PPC_BOOK3S_64
+ select ARCH_HAS_FAST_MULTIPLIER
config E5500_CPU
bool "Freescale e5500"
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