Re: [Announce] [patch] Modular Scheduler Core and Completely Fair Scheduler [CFS]

[Ingo Molnar]

* Ingo Molnar <mingo@xxxxxxx> wrote:

> so Linus was right: this was caused by scheduler starvation. I can see 
> one immediate problem already: the 'nice offset' is not divided by 
> nr_running as it should. The patch below should fix this but i have 
> yet to test it accurately, this change might as well render nice 
> levels unacceptably ineffective under high loads.

erm, rather the updated patch below if you want to use this on a 32-bit 
system. But ... i think you should wait until i have all this re-tested.

	Ingo

---
 include/linux/sched.h |    2 +-
 kernel/sched_fair.c   |    4 +++-
 2 files changed, 4 insertions(+), 2 deletions(-)

Index: linux/include/linux/sched.h
===================================================================
--- linux.orig/include/linux/sched.h
+++ linux/include/linux/sched.h
@@ -839,7 +839,7 @@ struct task_struct {
 
 	s64 wait_runtime;
 	u64 exec_runtime, fair_key;
-	s64 nice_offset, hog_limit;
+	s32 nice_offset, hog_limit;
 
 	unsigned long policy;
 	cpumask_t cpus_allowed;
Index: linux/kernel/sched_fair.c
===================================================================
--- linux.orig/kernel/sched_fair.c
+++ linux/kernel/sched_fair.c
@@ -31,7 +31,9 @@ static void __enqueue_task_fair(struct r
 	int leftmost = 1;
 	long long key;
 
-	key = rq->fair_clock - p->wait_runtime + p->nice_offset;
+	key = rq->fair_clock - p->wait_runtime;
+	if (unlikely(p->nice_offset))
+		key += p->nice_offset / (rq->nr_running + 1);
 
 	p->fair_key = key;
 
-
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