[RFC][PATCH 06/10] sched: Remove unlikely() from rt_policy() in sched.c

Steven Rostedt
2010-12-07T02:13:33Z

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From: Steven Rostedt <srostedt@redhat.com>

The rt_policy() has an unlikely() that the policy it is checking is
of RT priority (SCHED_FIFO or SCHED_RR).

According to the annotate branch profiler it is incorrect most of the time:

correct incorrect % Function File Line
------- --------- - -------- ---- ----
36667 654674 94 rt_policy sched.c 126

This makes sense because the rt_policy() is used by the sched_set_scheduler()
and nice(). Although users may use sys_nice a bit, all RT users use
the sched_set_scheduler() to set their RT priority, including kernel
threads.

The above numbers were from a normal desktop computer running
firefox, evolution, xchat and was part of a distcc compile farm.

Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
kernel/sched.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/kernel/sched.c b/kernel/sched.c
index dc91a4d..269a045 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -123,7 +123,7 @@

static inline int rt_policy(int policy)
{
- if (unlikely(policy == SCHED_FIFO || policy == SCHED_RR))
+ if (policy == SCHED_FIFO || policy == SCHED_RR)
return 1;
return 0;
}
--
1.7.2.3