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From: "tip-bot2 for Yunfeng Ye" <tip-bot2@linutronix.de>
To: linux-tip-commits@vger.kernel.org
Cc: Yunfeng Ye <yeyunfeng@huawei.com>,
	Frederic Weisbecker <frederic@kernel.org>,
	Ingo Molnar <mingo@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	x86@kernel.org, linux-kernel@vger.kernel.org
Subject: [tip: timers/nohz] tick/nohz: Conditionally restart tick on idle exit
Date: Thu, 13 May 2021 13:17:29 -0000	[thread overview]
Message-ID: <162091184942.29796.4815200413212139734.tip-bot2@tip-bot2> (raw)
In-Reply-To: <20210512232924.150322-3-frederic@kernel.org>

The following commit has been merged into the timers/nohz branch of tip:

Commit-ID:     a5183862e76fdc25f36b39c2489b816a5c66e2e5
Gitweb:        https://git.kernel.org/tip/a5183862e76fdc25f36b39c2489b816a5c66e2e5
Author:        Yunfeng Ye <yeyunfeng@huawei.com>
AuthorDate:    Thu, 13 May 2021 01:29:16 +02:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Thu, 13 May 2021 14:21:21 +02:00

tick/nohz: Conditionally restart tick on idle exit

In nohz_full mode, switching from idle to a task will unconditionally
issue a tick restart. If the task is alone in the runqueue or is the
highest priority, the tick will fire once then eventually stop. But that
alone is still undesired noise.

Therefore, only restart the tick on idle exit when it's strictly
necessary.

Signed-off-by: Yunfeng Ye <yeyunfeng@huawei.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210512232924.150322-3-frederic@kernel.org
---
 kernel/time/tick-sched.c | 42 +++++++++++++++++++++++++--------------
 1 file changed, 27 insertions(+), 15 deletions(-)

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 828b091..05c1ce1 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -926,22 +926,28 @@ static void tick_nohz_restart_sched_tick(struct tick_sched *ts, ktime_t now)
 	tick_nohz_restart(ts, now);
 }
 
-static void tick_nohz_full_update_tick(struct tick_sched *ts)
+static void __tick_nohz_full_update_tick(struct tick_sched *ts,
+					 ktime_t now)
 {
 #ifdef CONFIG_NO_HZ_FULL
 	int cpu = smp_processor_id();
 
-	if (!tick_nohz_full_cpu(cpu))
+	if (can_stop_full_tick(cpu, ts))
+		tick_nohz_stop_sched_tick(ts, cpu);
+	else if (ts->tick_stopped)
+		tick_nohz_restart_sched_tick(ts, now);
+#endif
+}
+
+static void tick_nohz_full_update_tick(struct tick_sched *ts)
+{
+	if (!tick_nohz_full_cpu(smp_processor_id()))
 		return;
 
 	if (!ts->tick_stopped && ts->nohz_mode == NOHZ_MODE_INACTIVE)
 		return;
 
-	if (can_stop_full_tick(cpu, ts))
-		tick_nohz_stop_sched_tick(ts, cpu);
-	else if (ts->tick_stopped)
-		tick_nohz_restart_sched_tick(ts, ktime_get());
-#endif
+	__tick_nohz_full_update_tick(ts, ktime_get());
 }
 
 static bool can_stop_idle_tick(int cpu, struct tick_sched *ts)
@@ -1209,18 +1215,24 @@ static void tick_nohz_account_idle_ticks(struct tick_sched *ts)
 #endif
 }
 
-static void __tick_nohz_idle_restart_tick(struct tick_sched *ts, ktime_t now)
+void tick_nohz_idle_restart_tick(void)
 {
-	tick_nohz_restart_sched_tick(ts, now);
-	tick_nohz_account_idle_ticks(ts);
+	struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
+
+	if (ts->tick_stopped) {
+		tick_nohz_restart_sched_tick(ts, ktime_get());
+		tick_nohz_account_idle_ticks(ts);
+	}
 }
 
-void tick_nohz_idle_restart_tick(void)
+static void tick_nohz_idle_update_tick(struct tick_sched *ts, ktime_t now)
 {
-	struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
+	if (tick_nohz_full_cpu(smp_processor_id()))
+		__tick_nohz_full_update_tick(ts, now);
+	else
+		tick_nohz_restart_sched_tick(ts, now);
 
-	if (ts->tick_stopped)
-		__tick_nohz_idle_restart_tick(ts, ktime_get());
+	tick_nohz_account_idle_ticks(ts);
 }
 
 /**
@@ -1252,7 +1264,7 @@ void tick_nohz_idle_exit(void)
 		tick_nohz_stop_idle(ts, now);
 
 	if (tick_stopped)
-		__tick_nohz_idle_restart_tick(ts, now);
+		tick_nohz_idle_update_tick(ts, now);
 
 	local_irq_enable();
 }

  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-bot2 for Yunfeng Ye [this message]
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: timers/nohz] tick/nohz: Only wake up " tip-bot2 for Frederic Weisbecker
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

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