From: Nick Piggin <piggin@cyberone.com.au>
Make sure to count kernel preemption as a context switch. A short cut
has been preventing it.
kernel/sched.c | 37 +++++++++++++++----------------------
1 files changed, 15 insertions(+), 22 deletions(-)
diff -puN kernel/sched.c~context-switch-accounting-fix kernel/sched.c
--- 25/kernel/sched.c~context-switch-accounting-fix 2003-11-11 19:29:37.000000000 -0800
+++ 25-akpm/kernel/sched.c 2003-11-11 19:29:37.000000000 -0800
@@ -1513,33 +1513,20 @@ need_resched:
spin_lock_irq(&rq->lock);
- /*
- * if entering off of a kernel preemption go straight
- * to picking the next task.
- */
- if (unlikely(preempt_count() & PREEMPT_ACTIVE))
- goto pick_next_task;
-
- switch (prev->state) {
- case TASK_INTERRUPTIBLE:
- if (unlikely(signal_pending(prev))) {
+ if (prev->state != TASK_RUNNING &&
+ likely(!(preempt_count() & PREEMPT_ACTIVE)) ) {
+ if (unlikely(signal_pending(prev)) &&
+ prev->state == TASK_INTERRUPTIBLE)
prev->state = TASK_RUNNING;
- break;
- }
- default:
- deactivate_task(prev, rq);
- prev->nvcsw++;
- break;
- case TASK_RUNNING:
- prev->nivcsw++;
+ else
+ deactivate_task(prev, rq);
}
-pick_next_task:
- if (unlikely(!rq->nr_running)) {
+
#ifdef CONFIG_SMP
+ if (unlikely(!rq->nr_running))
load_balance(rq, 1, cpu_to_node_mask(smp_processor_id()));
- if (rq->nr_running)
- goto pick_next_task;
#endif
+ if (unlikely(!rq->nr_running)) {
next = rq->idle;
rq->expired_timestamp = 0;
goto switch_tasks;
@@ -1586,6 +1573,12 @@ switch_tasks:
prev->timestamp = now;
if (likely(prev != next)) {
+ if (prev->state == TASK_RUNNING ||
+ unlikely(preempt_count() & PREEMPT_ACTIVE))
+ prev->nivcsw++;
+ else
+ prev->nvcsw++;
+
next->timestamp = now;
rq->nr_switches++;
rq->curr = next;
_