linux-kernel - [PATCH 1/4] perf/x86-64: make "default" memcpy() selection actually use glibc's implementation

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Date:	Wed, 18 Jan 2012 13:28:13 +0000
From:	"Jan Beulich" <JBeulich@...e.com>
To:	<a.p.zijlstra@...llo.nl>, <mingo@...e.hu>,
	<acme@...stprotocols.net>, <paulus@...ba.org>
Cc:	<linux-kernel@...r.kernel.org>
Subject: [PATCH 1/4] perf/x86-64: make "default" memcpy() selection
 actually use glibc's implementation

Since arch/x86/lib/memcpy_64.S implements not only __memcpy, but also
memcpy, without further precautions this function will get chose by the
static linker for resolving all references, and hence the "default"
measurement didn't really measure anything else than the
"x86-64-unrolled" one.

Fix this by renaming (through the pre-processor) the conflicting
symbol.

On my Westmere system, the glibc variant turns out to require about 4%
less instructions, but 15% more cycles for the default 1Mb block size
measured.

Signed-off-by: Jan Beulich <jbeulich@...e.com>

--- a/tools/perf/bench/mem-memcpy-x86-64-asm.S
+++ b/tools/perf/bench/mem-memcpy-x86-64-asm.S
@@ -1,2 +1,2 @@
-
+#define memcpy MEMCPY /* don't hide glibc's memcpy() */
 #include "../../../arch/x86/lib/memcpy_64.S"

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