On Mon, 18 Jun 2018 13:58:25 +0900 Byungchul Park <[email protected]> wrote:
> Hello Steven and Daniel, > > I've changed the 2nd patch a little bit to consider cpudl_clear() > additionally. Can I keep your Acked-by on? Actually, I think this should be a separate patch. It handles a different issue. > > (I temporarily removed the Acked-by you gave me.) > > Acked-by: Steven Rostedt (VMware) <[email protected]> > Acked-by: Daniel Bristot de Oliveira <[email protected]> > > -----8<----- > >From 1e368d276186c22f9da298206c718b33e805828d Mon Sep 17 00:00:00 2001 > From: Byungchul Park <[email protected]> > Date: Mon, 4 Jun 2018 15:05:08 +0900 > Subject: [RESEND PATCH v5 2/2] sched/deadline: Set cp->elements[0].cpu to -1 > when the > heap is empty > > Currently, migrating tasks to cpu0 unconditionally happens when the > heap is empty, since cp->elements[0].cpu is initialized to 0(=cpu0). > We have to distinguish between the empty case and cpu0 to avoid the > unnecessary migrations. Therefore, it has to return an invalid value > e.i. -1 in the case the heap is empty. > > Signed-off-by: Byungchul Park <[email protected]> > Suggested-by: Joel Fernandes <[email protected]> > --- > kernel/sched/cpudeadline.c | 14 ++++++++++++++ > 1 file changed, 14 insertions(+) > > diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c > index ae4fbdc..a200b36 100644 > --- a/kernel/sched/cpudeadline.c > +++ b/kernel/sched/cpudeadline.c > @@ -136,6 +136,10 @@ int cpudl_find(struct cpudl *cp, struct task_struct *p, > > WARN_ON(best_cpu != -1 && !cpu_present(best_cpu)); > > + /* The heap tree is empty, just return. */ > + if (best_cpu == -1) > + return 0; > + Actually, why not put the if before the WARN_ON, and then we can simplify the WARN_ON: if (best_cpu == -1) return 0; WARN_ON(!cpu_present(best_cpu)); -- Steve > if (cpumask_test_cpu(best_cpu, &p->cpus_allowed) && > dl_time_before(dl_se->deadline, cpudl_maximum_dl(cp))) { > if (later_mask) > @@ -172,6 +176,13 @@ void cpudl_clear(struct cpudl *cp, int cpu) > * This could happen if a rq_offline_dl is > * called for a CPU without -dl tasks running. > */ > + } else if (cp->size == 1){ > + /* Only one element in the heap, clear it. */ > + cp->elements[0].cpu = -1; > + cp->elements[cpu].idx = IDX_INVALID; > + cp->size = 0; > + > + cpumask_set_cpu(cpu, cp->free_cpus); > } else { > new_cpu = cp->elements[cp->size - 1].cpu; > cp->elements[old_idx].dl = cp->elements[cp->size - 1].dl; > @@ -267,6 +278,9 @@ int cpudl_init(struct cpudl *cp) > for_each_possible_cpu(i) > cp->elements[i].idx = IDX_INVALID; > > + /* Mark heap as initially empty. */ > + cp->elements[0].cpu = -1; > + > return 0; > } >
