From: Tim Blechmann <tim@klingt.org>
Date: Tue, 24 Nov 2009 10:55:15 +0000 (+0100)
Subject: sched, x86: Optimize branch hint in __switch_to()
X-Git-Tag: v2.6.33-rc1~398^2~11
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=a3a1de0c34de6f5f8332cd6151c46af7813c0fcb;p=karo-tx-linux.git

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>
---

diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index ad535b683170..d9db1049e86f 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);