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authorDietmar Eggemann <dietmar.eggemann@arm.com>2021-01-19 09:35:42 +0100
committerIngo Molnar <mingo@kernel.org>2021-02-17 14:12:42 +0100
commitde40f33e788b0c016bfde512ace2f76339ef7ddb (patch)
tree3fd7809b0ebcad750b2351a58e95c227660fcdc9 /kernel/sched/deadline.c
parentb0d6d4789677d128b1933af023083054f0973574 (diff)
downloadlinux-de40f33e788b0c016bfde512ace2f76339ef7ddb.tar.bz2
sched/deadline: Reduce rq lock contention in dl_add_task_root_domain()
dl_add_task_root_domain() is called during sched domain rebuild: rebuild_sched_domains_locked() partition_and_rebuild_sched_domains() rebuild_root_domains() for all top_cpuset descendants: update_tasks_root_domain() for all tasks of cpuset: dl_add_task_root_domain() Change it so that only the task pi lock is taken to check if the task has a SCHED_DEADLINE (DL) policy. In case that p is a DL task take the rq lock as well to be able to safely de-reference root domain's DL bandwidth structure. Most of the tasks will have another policy (namely SCHED_NORMAL) and can now bail without taking the rq lock. One thing to note here: Even in case that there aren't any DL user tasks, a slow frequency switching system with cpufreq gov schedutil has a DL task (sugov) per frequency domain running which participates in DL bandwidth management. Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Reviewed-by: Quentin Perret <qperret@google.com> Reviewed-by: Valentin Schneider <valentin.schneider@arm.com> Reviewed-by: Daniel Bristot de Oliveira <bristot@redhat.com> Acked-by: Juri Lelli <juri.lelli@redhat.com> Link: https://lkml.kernel.org/r/20210119083542.19856-1-dietmar.eggemann@arm.com
Diffstat (limited to 'kernel/sched/deadline.c')
-rw-r--r--kernel/sched/deadline.c11
1 files changed, 7 insertions, 4 deletions
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 1508d126e88b..6f377969fa71 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -2388,9 +2388,13 @@ void dl_add_task_root_domain(struct task_struct *p)
struct rq *rq;
struct dl_bw *dl_b;
- rq = task_rq_lock(p, &rf);
- if (!dl_task(p))
- goto unlock;
+ raw_spin_lock_irqsave(&p->pi_lock, rf.flags);
+ if (!dl_task(p)) {
+ raw_spin_unlock_irqrestore(&p->pi_lock, rf.flags);
+ return;
+ }
+
+ rq = __task_rq_lock(p, &rf);
dl_b = &rq->rd->dl_bw;
raw_spin_lock(&dl_b->lock);
@@ -2399,7 +2403,6 @@ void dl_add_task_root_domain(struct task_struct *p)
raw_spin_unlock(&dl_b->lock);
-unlock:
task_rq_unlock(rq, p, &rf);
}