[PATCH] sched: improve efficiency of sched_fork()
Problem:
sched_fork() has always called scheduler_tick() in some (unlikely)
circumstances in order to update the current task in light of those
circumstances. It has always been the case that the work done by
scheduler_tick() was more than was required to handle the problem in
hand but no harm was done except for the waste of a few CPU cycles.
However, the splitting of scheduler_tick() into two procedures in
2.6.20-rc1 enables the wasted cycles to be saved as the new procedure
task_running_tick() does all the work that is required to rectify the
problem being handled.
Solution:
Replace the call to scheduler_tick() in sched_fork() with a call to
task_running_tick().
Signed-off-by: Peter Williams <pwil3058@bigpond.com.au>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/kernel/sched.c b/kernel/sched.c
index 5cd833b..b81ed87 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -1567,6 +1567,7 @@
return try_to_wake_up(p, state, 0);
}
+static void task_running_tick(struct rq *rq, struct task_struct *p);
/*
* Perform scheduler related setup for a newly forked process p.
* p is forked by current.
@@ -1627,7 +1628,7 @@
* runqueue lock is not a problem.
*/
current->time_slice = 1;
- scheduler_tick();
+ task_running_tick(cpu_rq(cpu), current);
}
local_irq_enable();
put_cpu();