Messages in this thread Patch in this message | | | Date | Sun, 15 Apr 2007 21:20:46 +0200 | From | Ingo Molnar <> | Subject | Re: [Announce] [patch] Modular Scheduler Core and Completely Fair Scheduler [CFS] |
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* Willy Tarreau <w@1wt.eu> wrote:
> > to debug this, could you try to apply this add-on as well: > > > > http://redhat.com/~mingo/cfs-scheduler/sched-fair-print.patch > > > > with this patch applied you should have a /proc/sched_debug file > > that prints all runnable tasks and other interesting info from the > > runqueue. > > I don't know if you have seen my mail from yesterday evening (here). I > found that changing keventd prio fixed the problem. You may be > interested in the description. I sent it at 21:01 (+200).
ah, indeed i missed that mail - the response to the patches was quite overwhelming (and i naively thought people dont do Linux hacking over the weekends anymore ;).
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.
Ingo
---------> --- kernel/sched_fair.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
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; p->fair_key = key; - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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