Gitweb:     
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=98fbc798533339be802c6dcd48c2293c712e87db
Commit:     98fbc798533339be802c6dcd48c2293c712e87db
Parent:     deac4ee65af4befb66b542e4a782e63da93b51a0
Author:     Dmitry Adamushko <[EMAIL PROTECTED]>
AuthorDate: Fri Aug 24 20:39:10 2007 +0200
Committer:  Ingo Molnar <[EMAIL PROTECTED]>
CommitDate: Fri Aug 24 20:39:10 2007 +0200

    sched: optimize task_tick_rt() a bit
    
    Mitchell Erblich suggested a quality-of-implementation change to
    not requeue SCHED_RR tasks if there's only a single task on the
    runqueue, by checking for rq->nr_running == 1.
    
    provide a more efficient implementation of that, to check that
    particular RT priority-queue only.
    
    [ From: [EMAIL PROTECTED] ]
    
    Also first requeue the task then set need_resched - results in slightly
    better machine-instruction ordering. Also clean up the code a bit.
    
    Signed-off-by: Dmitry Adamushko <[EMAIL PROTECTED]>
    Signed-off-by: Ingo Molnar <[EMAIL PROTECTED]>
---
 kernel/sched_rt.c |   11 ++++++++---
 1 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
index dcdcad6..4b87476 100644
--- a/kernel/sched_rt.c
+++ b/kernel/sched_rt.c
@@ -207,10 +207,15 @@ static void task_tick_rt(struct rq *rq, struct 
task_struct *p)
                return;
 
        p->time_slice = static_prio_timeslice(p->static_prio);
-       set_tsk_need_resched(p);
 
-       /* put it at the end of the queue: */
-       requeue_task_rt(rq, p);
+       /*
+        * Requeue to the end of queue if we are not the only element
+        * on the queue:
+        */
+       if (p->run_list.prev != p->run_list.next) {
+               requeue_task_rt(rq, p);
+               set_tsk_need_resched(p);
+       }
 }
 
 static struct sched_class rt_sched_class __read_mostly = {
-
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