From: "tip-bot2 for Dietmar Eggemann" <tip-bot2@linutronix.de>
To: linux-tip-commits@vger.kernel.org
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>,
"Peter Zijlstra (Intel)" <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>,
Quentin Perret <qperret@google.com>,
Valentin Schneider <valentin.schneider@arm.com>,
Daniel Bristot de Oliveira <bristot@redhat.com>,
Juri Lelli <juri.lelli@redhat.com>,
x86@kernel.org, linux-kernel@vger.kernel.org
Subject: [tip: sched/core] sched/deadline: Reduce rq lock contention in dl_add_task_root_domain()
Date: Wed, 17 Feb 2021 13:17:32 -0000 [thread overview]
Message-ID: <161356785255.20312.13367741328558766056.tip-bot2@tip-bot2> (raw)
In-Reply-To: <20210119083542.19856-1-dietmar.eggemann@arm.com>
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@arm.com>
AuthorDate: Tue, 19 Jan 2021 09:35:42 +01:00
Committer: Ingo Molnar <mingo@kernel.org>
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@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
---
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);
}
prev parent reply other threads:[~2021-02-17 13:21 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-19 8:35 [PATCH] sched/deadline: Reduce rq lock contention in dl_add_task_root_domain() Dietmar Eggemann
2021-01-19 20:51 ` Valentin Schneider
2021-01-20 7:52 ` Daniel Bristot de Oliveira
2021-01-21 6:28 ` Juri Lelli
2021-02-08 13:43 ` Peter Zijlstra
2021-02-10 13:53 ` [tip: sched/core] " tip-bot2 for Dietmar Eggemann
2021-02-17 13:17 ` tip-bot2 for Dietmar Eggemann [this message]
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