From a3a1de0c34de6f5f8332cd6151c46af7813c0fcb Mon Sep 17 00:00:00 2001
From: Tim Blechmann <tim@klingt.org>
Date: Tue, 24 Nov 2009 11:55:15 +0100
Subject: [PATCH] sched, x86: Optimize branch hint in __switch_to()
Branch hint profiling on my nehalem machine showed 96%
incorrect branch hints:
6548732 174664120 96 __switch_to process_64.c
406
6548745 174565593 96 __switch_to process_64.c
410
Signed-off-by: Tim Blechmann <tim@klingt.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <4B0BBB93.3080307@klingt.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
arch/x86/kernel/process_64.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index ad535b6831700..d9db1049e86fc 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -406,11 +406,10 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
* This won't pick up thread selector changes, but I guess that is ok.
*/
savesegment(es, prev->es);
- if (unlikely(next->es | prev->es))
+ if (next->es | prev->es)
loadsegment(es, next->es);
-
savesegment(ds, prev->ds);
- if (unlikely(next->ds | prev->ds))
+ if (next->ds | prev->ds)
loadsegment(ds, next->ds);
--
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