The following commit has been merged into the sched/core branch of tip: Commit-ID: de40f33e788b0c016bfde512ace2f76339ef7ddb Gitweb: https://git.kernel.org/tip/de40f33e788b0c016bfde512ace2f76339ef7ddb Author: Dietmar Eggemann <dietmar.eggemann@xxxxxxx> AuthorDate: Tue, 19 Jan 2021 09:35:42 +01:00 Committer: Ingo Molnar <mingo@xxxxxxxxxx> CommitterDate: Wed, 17 Feb 2021 14:12:42 +01:00 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@xxxxxxx> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> Reviewed-by: Quentin Perret <qperret@xxxxxxxxxx> Reviewed-by: Valentin Schneider <valentin.schneider@xxxxxxx> Reviewed-by: Daniel Bristot de Oliveira <bristot@xxxxxxxxxx> Acked-by: Juri Lelli <juri.lelli@xxxxxxxxxx> Link: https://lkml.kernel.org/r/20210119083542.19856-1-dietmar.eggemann@xxxxxxx --- kernel/sched/deadline.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index 1508d12..6f37796 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); }
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