linux-kernel - [PATCH 02/14] sched/cputime: Add vtime idle task state

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Message-Id: <20191016025700.31277-3-frederic@kernel.org>
Date:   Wed, 16 Oct 2019 04:56:48 +0200
From:   Frederic Weisbecker <frederic@...nel.org>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Frederic Weisbecker <frederic@...nel.org>,
        Jacek Anaszewski <jacek.anaszewski@...il.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Wanpeng Li <wanpengli@...cent.com>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Rik van Riel <riel@...riel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Yauheni Kaliuta <yauheni.kaliuta@...hat.com>,
        Ingo Molnar <mingo@...nel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Pavel Machek <pavel@....cz>
Subject: [PATCH 02/14] sched/cputime: Add vtime idle task state

Record idle as a VTIME state instead of guessing it from VTIME_SYS and
is_idle_task(). This is going to simplify the cputime read side
especially as its state machine is going to further expand in order to
fully support kcpustat on nohz_full.

Signed-off-by: Frederic Weisbecker <frederic@...nel.org>
Cc: Yauheni Kaliuta <yauheni.kaliuta@...hat.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Rik van Riel <riel@...riel.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Wanpeng Li <wanpengli@...cent.com>
Cc: Ingo Molnar <mingo@...nel.org>
---
 include/linux/sched.h  |  6 ++++--
 kernel/sched/cputime.c | 13 ++++++++-----
 2 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index d5d07335a97b..4ae19be2c126 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -249,10 +249,12 @@ struct prev_cputime {
 enum vtime_state {
 	/* Task is sleeping or running in a CPU with VTIME inactive: */
 	VTIME_INACTIVE = 0,
-	/* Task runs in userspace in a CPU with VTIME active: */
-	VTIME_USER,
+	/* Task is idle */
+	VTIME_IDLE,
 	/* Task runs in kernelspace in a CPU with VTIME active: */
 	VTIME_SYS,
+	/* Task runs in userspace in a CPU with VTIME active: */
+	VTIME_USER,
 };
 
 struct vtime {
diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
index 40f581692254..2e885e870aa1 100644
--- a/kernel/sched/cputime.c
+++ b/kernel/sched/cputime.c
@@ -813,7 +813,7 @@ void vtime_task_switch_generic(struct task_struct *prev)
 	struct vtime *vtime = &prev->vtime;
 
 	write_seqcount_begin(&vtime->seqcount);
-	if (is_idle_task(prev))
+	if (vtime->state == VTIME_IDLE)
 		vtime_account_idle(prev);
 	else
 		__vtime_account_kernel(prev, vtime);
@@ -824,7 +824,10 @@ void vtime_task_switch_generic(struct task_struct *prev)
 	vtime = &current->vtime;
 
 	write_seqcount_begin(&vtime->seqcount);
-	vtime->state = VTIME_SYS;
+	if (is_idle_task(current))
+		vtime->state = VTIME_IDLE;
+	else
+		vtime->state = VTIME_SYS;
 	vtime->starttime = sched_clock();
 	vtime->cpu = smp_processor_id();
 	write_seqcount_end(&vtime->seqcount);
@@ -837,7 +840,7 @@ void vtime_init_idle(struct task_struct *t, int cpu)
 
 	local_irq_save(flags);
 	write_seqcount_begin(&vtime->seqcount);
-	vtime->state = VTIME_SYS;
+	vtime->state = VTIME_IDLE;
 	vtime->starttime = sched_clock();
 	vtime->cpu = cpu;
 	write_seqcount_end(&vtime->seqcount);
@@ -888,8 +891,8 @@ void task_cputime(struct task_struct *t, u64 *utime, u64 *stime)
 		*utime = t->utime;
 		*stime = t->stime;
 
-		/* Task is sleeping, nothing to add */
-		if (vtime->state == VTIME_INACTIVE || is_idle_task(t))
+		/* Task is sleeping or idle, nothing to add */
+		if (vtime->state < VTIME_SYS)
 			continue;
 
 		delta = vtime_delta(vtime);
-- 
2.23.0