[PATCH 06/25] sched/cputime: Add vtime idle task state

Frederic Weisbecker
2018-11-14T02:46:33Z

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>
Cc: Yauheni Kaliuta <yauheni.kaliuta@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Wanpeng Li <wanpengli@tencent.com>
Cc: Ingo Molnar <mingo@kernel.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 9f56880..6d13938 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -265,10 +265,12 @@ struct task_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 6ac27687..a9f42cc 100644
--- a/kernel/sched/cputime.c
+++ b/kernel/sched/cputime.c
@@ -812,7 +812,7 @@ 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);
@@ -823,7 +823,10 @@ 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);
@@ -836,7 +839,7 @@ 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);
@@ -887,8 +890,8 @@ 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);
--
2.7.4