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

Ingo Molnar
2007-04-15T19:38:15Z

* Ingo Molnar <mingo@elte.hu> 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;