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) <rost...@goodmis.org>
Acked-by: Daniel Bristot de Oliveira <bris...@redhat.com>
-----8<-----
>From 1e368d276186c22f9da298206c718b33e805828d Mon Sep 17 00:00:00 2001
From: Byungchul Park <byungchul.p...@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.p...@lge.com>
Suggested-by: Joel Fernandes <joe...@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
