From: Anton Blanchard <anton@samba.org>
To: benh@kernel.crashing.org, paulus@samba.org,
michael@ellerman.id.au, torvalds@linux-foundation.org
Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: [PATCH 2/2] powerpc: Use CONFIG_ARCH_HAS_FAST_MULTIPLIER
Date: Tue, 16 Sep 2014 10:49:14 +1000 [thread overview]
Message-ID: <20140916104914.66abcca1@kryten> (raw)
In-Reply-To: <20140916104749.35b84da8@kryten>
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 <anton@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"
prev parent reply other threads:[~2014-09-16 0:49 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-16 0:47 [PATCH 1/2] powerpc: Add POWER8 CPU selection Anton Blanchard
2014-09-16 0:49 ` Anton Blanchard [this message]
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