linux-kernel - [PATCH 3/9] perf bench: Make "default" memcpy() selection actually use glibc's implementation

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Message-Id: <1327446481-5505-4-git-send-email-acme@infradead.org>
Date:	Tue, 24 Jan 2012 21:07:55 -0200
From:	Arnaldo Carvalho de Melo <acme@...radead.org>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	linux-kernel@...r.kernel.org, Jan Beulich <JBeulich@...e.com>,
	Paul Mackerras <paulus@...ba.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Jan Beulich <jbeulich@...e.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: [PATCH 3/9] perf bench: Make "default" memcpy() selection actually use glibc's implementation

From: Jan Beulich <JBeulich@...e.com>

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.

Cc: Ingo Molnar <mingo@...e.hu>
Cc: Paul Mackerras <paulus@...ba.org>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Link: http://lkml.kernel.org/r/4F16D6FD020000780006D72F@nat28.tlf.novell.com
Signed-off-by: Jan Beulich <jbeulich@...e.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 tools/perf/bench/mem-memcpy-x86-64-asm.S |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/tools/perf/bench/mem-memcpy-x86-64-asm.S b/tools/perf/bench/mem-memcpy-x86-64-asm.S
index a57b66e..384b607 100644
--- 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"
-- 
1.7.9.rc2.1.g69204

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