Messages in this thread Patch in this message | | | From | Byungchul Park <> | Subject | [PATCH v4 2/2] sched/deadline: Set cp->elements[0].cpu to -1 when the heap is empty | Date | Mon, 4 Jun 2018 15:36:47 +0900 |
| |
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?
(I temporarily removed the Acked-by you gave me.)
Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org> Acked-by: Daniel Bristot de Oliveira <bristot@redhat.com>
-----8<----- From 1e368d276186c22f9da298206c718b33e805828d Mon Sep 17 00:00:00 2001 From: Byungchul Park <byungchul.park@lge.com> Date: Mon, 4 Jun 2018 15:05:08 +0900 Subject: [PATCH v4 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 <byungchul.park@lge.com> Suggested-by: Joel Fernandes <joelaf@google.com> --- 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; + 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[i].cpu = -1; + return 0; } -- 1.9.1
| |