From: "tip-bot2 for Frederic Weisbecker" <tip-bot2@linutronix.de>
To: linux-tip-commits@vger.kernel.org
Cc: Peter Zijlstra <peterz@infradead.org>,
Frederic Weisbecker <frederic@kernel.org>,
Marcelo Tosatti <mtosatti@redhat.com>,
Ingo Molnar <mingo@kernel.org>,
x86@kernel.org, linux-kernel@vger.kernel.org
Subject: [tip: timers/nohz] tick/nohz: Only wake up a single target cpu when kicking a task
Date: Thu, 13 May 2021 13:17:27 -0000 [thread overview]
Message-ID: <162091184780.29796.751845297099091276.tip-bot2@tip-bot2> (raw)
In-Reply-To: <20210512232924.150322-7-frederic@kernel.org>
The following commit has been merged into the timers/nohz branch of tip:
Commit-ID: 29721b859217b946bfc001c1644745ed4d7c26cb
Gitweb: https://git.kernel.org/tip/29721b859217b946bfc001c1644745ed4d7c26cb
Author: Frederic Weisbecker <frederic@kernel.org>
AuthorDate: Thu, 13 May 2021 01:29:20 +02:00
Committer: Ingo Molnar <mingo@kernel.org>
CommitterDate: Thu, 13 May 2021 14:21:22 +02:00
tick/nohz: Only wake up a single target cpu when kicking a task
When adding a tick dependency to a task, its necessary to
wake up the CPU where the task resides to reevaluate tick
dependencies on that CPU.
However the current code wakes up all nohz_full CPUs, which
is unnecessary.
Switch to waking up a single CPU, by using ordering of writes
to task->cpu and task->tick_dep_mask.
[ mingo: Minor readability edit. ]
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210512232924.150322-7-frederic@kernel.org
---
kernel/time/tick-sched.c | 40 ++++++++++++++++++++++++++-------------
1 file changed, 27 insertions(+), 13 deletions(-)
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 89ec0ab..b90ca66 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -322,6 +322,31 @@ void tick_nohz_full_kick_cpu(int cpu)
irq_work_queue_on(&per_cpu(nohz_full_kick_work, cpu), cpu);
}
+static void tick_nohz_kick_task(struct task_struct *tsk)
+{
+ int cpu = task_cpu(tsk);
+
+ /*
+ * If the task concurrently migrates to another CPU,
+ * we guarantee it sees the new tick dependency upon
+ * schedule.
+ *
+ *
+ * set_task_cpu(p, cpu);
+ * STORE p->cpu = @cpu
+ * __schedule() (switch to task 'p')
+ * LOCK rq->lock
+ * smp_mb__after_spin_lock() STORE p->tick_dep_mask
+ * tick_nohz_task_switch() smp_mb() (atomic_fetch_or())
+ * LOAD p->tick_dep_mask LOAD p->cpu
+ */
+
+ preempt_disable();
+ if (cpu_online(cpu))
+ tick_nohz_full_kick_cpu(cpu);
+ preempt_enable();
+}
+
/*
* Kick all full dynticks CPUs in order to force these to re-evaluate
* their dependency on the tick and restart it if necessary.
@@ -404,19 +429,8 @@ EXPORT_SYMBOL_GPL(tick_nohz_dep_clear_cpu);
*/
void tick_nohz_dep_set_task(struct task_struct *tsk, enum tick_dep_bits bit)
{
- if (!atomic_fetch_or(BIT(bit), &tsk->tick_dep_mask)) {
- if (tsk == current) {
- preempt_disable();
- tick_nohz_full_kick();
- preempt_enable();
- } else {
- /*
- * Some future tick_nohz_full_kick_task()
- * should optimize this.
- */
- tick_nohz_full_kick_all();
- }
- }
+ if (!atomic_fetch_or(BIT(bit), &tsk->tick_dep_mask))
+ tick_nohz_kick_task(tsk);
}
EXPORT_SYMBOL_GPL(tick_nohz_dep_set_task);
next prev parent reply other threads:[~2021-05-13 13:19 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-12 23:29 [GIT PULL] tick/nohz updates v3 Frederic Weisbecker
2021-05-12 23:29 ` [PATCH 01/10] tick/nohz: Evaluate the CPU expression after the static key Frederic Weisbecker
2021-05-13 13:17 ` [tip: timers/nohz] " tip-bot2 for Peter Zijlstra
2021-05-12 23:29 ` [PATCH 02/10] tick/nohz: Conditionally restart tick on idle exit Frederic Weisbecker
2021-05-13 13:17 ` [tip: timers/nohz] " tip-bot2 for Yunfeng Ye
2021-05-12 23:29 ` [PATCH 03/10] tick/nohz: Remove superflous check for CONFIG_VIRT_CPU_ACCOUNTING_NATIVE Frederic Weisbecker
2021-05-13 13:17 ` [tip: timers/nohz] " tip-bot2 for Frederic Weisbecker
2021-05-12 23:29 ` [PATCH 04/10] tick/nohz: Update idle_exittime on actual idle exit Frederic Weisbecker
2021-05-13 13:17 ` [tip: timers/nohz] " tip-bot2 for Yunfeng Ye
2021-05-12 23:29 ` [PATCH 05/10] tick/nohz: Update nohz_full Kconfig help Frederic Weisbecker
2021-05-13 13:17 ` [tip: timers/nohz] " tip-bot2 for Frederic Weisbecker
2021-05-12 23:29 ` [PATCH 06/10] tick/nohz: Only wakeup a single target cpu when kicking a task Frederic Weisbecker
2021-05-13 13:17 ` tip-bot2 for Frederic Weisbecker [this message]
2021-05-12 23:29 ` [PATCH 07/10] tick/nohz: Change signal tick dependency to wakeup CPUs of member tasks Frederic Weisbecker
2021-05-13 13:17 ` [tip: timers/nohz] tick/nohz: Change signal tick dependency to wake up " tip-bot2 for Marcelo Tosatti
2021-05-12 23:29 ` [PATCH 08/10] tick/nohz: Kick only _queued_ task whose tick dependency is updated Frederic Weisbecker
2021-05-13 13:17 ` [tip: timers/nohz] " tip-bot2 for Marcelo Tosatti
2021-05-12 23:29 ` [PATCH 09/10] tick/nohz: Call tick_nohz_task_switch() with interrupts disabled Frederic Weisbecker
2021-05-13 13:17 ` [tip: timers/nohz] " tip-bot2 for Peter Zijlstra
2021-05-12 23:29 ` [PATCH 10/10] MAINTAINERS: Add myself as context tracking maintainer Frederic Weisbecker
2021-05-19 9:21 ` [tip: timers/nohz] " tip-bot2 for Frederic Weisbecker
2021-05-13 12:23 ` [GIT PULL] tick/nohz updates v3 Ingo Molnar
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=162091184780.29796.751845297099091276.tip-bot2@tip-bot2 \
--to=tip-bot2@linutronix.de \
--cc=frederic@kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-tip-commits@vger.kernel.org \
--cc=mingo@kernel.org \
--cc=mtosatti@redhat.com \
--cc=peterz@infradead.org \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).