Messages in this thread | | | Date | Sat, 11 Oct 2008 09:55:37 -0400 (EDT) | From | Steven Rostedt <> | Subject | Re: [PATCH] sched: fair scheduler should not resched rt tasks |
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On Sat, 11 Oct 2008, Peter Zijlstra wrote:
> On Sat, 2008-10-11 at 03:01 -0400, Steven Rostedt wrote: > > Using ftrace, I noticed latencies in real-time tasks where they were > > needlessly calling schedule due to sched_fair sending out time slices. > > > > This patch prevents a call to resched_task by the sched fair class if > > the task it wants to reschedule is an rt task. > > Right, thats not a good thing, however this patch looks wrong, we should > never call hrtick_start_fair() on a rt task to begin with.
Great! I don't care which way we fix this. This was making noticeable latencies against rt tasks.
> > The way I can see that happening is through enqueue/dequeue_task_fair() > where we want to re-programm the hrtick because nr_running changes (and > thus the current tasks desired runtime).
My original patch was more like this one, but I wasn't sure if I was skipping any calculations that were assumed to be made. Thus, I wrote the bare minimum and sent it out CC'ing the experts. Looks like my plan worked ;-)
-- Steve
> > Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Steven Rostedt <srostedt@redhat.com>
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