Messages in this thread | | | Date | Mon, 17 Feb 2020 11:20:36 +0000 | From | Qais Yousef <> | Subject | Re: [PATCH 2/3] sched/rt: allow pulling unfitting task |
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On 02/17/20 14:40, Pavan Kondeti wrote: > Hi Qais, > > On Fri, Feb 14, 2020 at 04:39:48PM +0000, Qais Yousef wrote: > > When implemented RT Capacity Awareness; the logic was done such that if > > a task was running on a fitting CPU, then it was sticky and we would try > > our best to keep it there. > > > > But as Steve suggested, to adhere to the strict priority rules of RT > > class; allow pulling an RT task to unfitting CPU to ensure it gets a > > chance to run ASAP. When doing so, mark the queue as overloaded to give > > the system a chance to push the task to a better fitting CPU when a > > chance arises. > > > > Suggested-by: Steven Rostedt <rostedt@goodmis.org> > > Signed-off-by: Qais Yousef <qais.yousef@arm.com> > > --- > > kernel/sched/rt.c | 16 +++++++++++++--- > > 1 file changed, 13 insertions(+), 3 deletions(-) > > > > diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c > > index 4043abe45459..0c8bac134d3a 100644 > > --- a/kernel/sched/rt.c > > +++ b/kernel/sched/rt.c > > @@ -1646,10 +1646,20 @@ static void put_prev_task_rt(struct rq *rq, struct task_struct *p) > > > > static int pick_rt_task(struct rq *rq, struct task_struct *p, int cpu) > > { > > - if (!task_running(rq, p) && > > - cpumask_test_cpu(cpu, p->cpus_ptr) && > > - rt_task_fits_capacity(p, cpu)) > > + if (!task_running(rq, p) && cpumask_test_cpu(cpu, p->cpus_ptr)) { > > + > > + /* > > + * If the CPU doesn't fit the task, allow pulling but mark the > > + * rq as overloaded so that we can push it again to a more > > + * suitable CPU ASAP. > > + */ > > + if (!rt_task_fits_capacity(p, cpu)) { > > + rt_set_overload(rq); > > + rq->rt.overloaded = 1; > > + } > > + > > Here rq is source rq from which the task is being pulled. I can't understand > how marking overload condition on source_rq help. Because overload condition > gets cleared in the task dequeue path. i.e dec_rt_tasks->dec_rt_migration-> > update_rt_migration().
Err yes indeed I rushed this patch. Let me try again.
Thanks
-- Qais Yousef
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