From: Ingo Molnar <mingo@elte.hu>
Do wakeup-balancing only if the wakeup-CPU (or any of its siblings) is
idle.
This prevents excessive wakeup-balancing while the system is highly loaded,
but helps spread out the workload on partly idle systems.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---
kernel/sched.c | 6 ++++++
1 files changed, 6 insertions(+)
diff -puN kernel/sched.c~sched-better-wake-balancing-3 kernel/sched.c
--- devel/kernel/sched.c~sched-better-wake-balancing-3 2005-08-21 23:49:39.000000000 -0700
+++ devel-akpm/kernel/sched.c 2005-08-21 23:49:39.000000000 -0700
@@ -1255,7 +1255,13 @@ static int try_to_wake_up(task_t *p, uns
if (unlikely(task_running(rq, p)))
goto out_activate;
+ /*
+ * Only do wakeup-balancing (== potentially migrate the task)
+ * if this CPU (or any SMT sibling) is idle:
+ */
new_cpu = cpu;
+ if (!idle_cpu(this_cpu) && this_cpu == wake_idle(this_cpu, p))
+ goto out_set_cpu;
schedstat_inc(rq, ttwu_cnt);
if (cpu == this_cpu) {
_