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@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Jacek Anaszewski <jacek.anaszewski@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rafael J . Wysocki <rjw@rjwysocki.net>
Cc: Rik van Riel <riel@surriel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Wanpeng Li <wanpengli@tencent.com>
Cc: Yauheni Kaliuta <yauheni.kaliuta@redhat.com>
Link: https://lkml.kernel.org/r/20191016025700.31277-3-frederic@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/include/linux/sched.h b/include/linux/sched.h
index d5d07335a97b9ff69fd476a18e7e5c09e2df8861..4ae19be2c1265d8a05ab09e6dfe94848543310ae 100644 (file)
--- 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 40f58169225488424c9e6914e14f8a330fd22f5c..2e885e870aa157ed9cdbc6aec736c09f733d805e 100644 (file)
--- 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);