Messages in this thread | | | Date | Wed, 1 Mar 2017 11:19:22 -0500 | From | Steven Rostedt <> | Subject | Re: [PATCH] sched: Optimize pick_next_task for idle_sched_class too |
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On Wed, 1 Mar 2017 17:03:52 +0100 Peter Zijlstra <peterz@infradead.org> wrote:
> On Wed, Mar 01, 2017 at 10:53:03AM -0500, Steven Rostedt wrote: > > Peter, do we have a solution for this yet? Are you going to add the one > > with the linker magic? > > I queued the below earlier today.
Isn't this pretty much identical to the patch I sent you a month ago?
http://lkml.kernel.org/r/20170119101703.2abeaeb6@gandalf.local.home
-- Steve
> > --- > Subject: sched: Fix pick_next_task() for RT,DL > From: Peter Zijlstra <peterz@infradead.org> > Date: Wed Mar 1 10:51:47 CET 2017 > > Pavan noticed that commit 49ee576809d8 ("sched/core: Optimize > pick_next_task() for idle_sched_class") broke RT,DL balancing by > robbing them of the opportinty to do new-'idle' balancing when their > last runnable task (on that runqueue) goes away. > > Cc: Steven Rostedt <rostedt@goodmis.org> > Reported-by: Pavan Kondeti <pkondeti@codeaurora.org> > Fixes: 49ee576809d8 ("sched/core: Optimize pick_next_task() for idle_sched_class") > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> > --- > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -3273,10 +3273,15 @@ pick_next_task(struct rq *rq, struct tas > struct task_struct *p; > > /* > - * Optimization: we know that if all tasks are in > - * the fair class we can call that function directly: > + * Optimization: we know that if all tasks are in the fair class we can > + * call that function directly, but only if the @pref task wasn't of a > + * higher scheduling class, because otherwise those loose the > + * opportunity to pull in more work from other CPUs. > */ > - if (likely(rq->nr_running == rq->cfs.h_nr_running)) { > + if (likely((prev->sched_class == &idle_sched_class || > + prev->sched_class == &fair_sched_class) && > + rq->nr_running == rq->cfs.h_nr_running)) { > + > p = fair_sched_class.pick_next_task(rq, prev, rf); > if (unlikely(p == RETRY_TASK)) > goto again;
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