[PATCH RESEND 27/36] vtime: Return nsecs instead of cputime_t to account

Frederic Weisbecker
2017-01-31T03:20:59Z

Turn the full dynticks cputime clock source to return nsec while keeping
its very internals jiffies based for performance reasons.

Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: Wanpeng Li <wanpeng.li@hotmail.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
---
kernel/sched/cputime.c | 31 +++++++++++--------------------
1 file changed, 11 insertions(+), 20 deletions(-)

diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
index f3a56bf..2ecec3a 100644
--- a/kernel/sched/cputime.c
+++ b/kernel/sched/cputime.c
@@ -678,20 +678,20 @@ void thread_group_cputime_adjusted(struct task_struct *p, u64 *ut, u64 *st)
#endif /* !CONFIG_VIRT_CPU_ACCOUNTING_NATIVE */

#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
-static cputime_t vtime_delta(struct task_struct *tsk)
+static u64 vtime_delta(struct task_struct *tsk)
{
unsigned long now = READ_ONCE(jiffies);

if (time_before(now, (unsigned long)tsk->vtime_snap))
return 0;

- return jiffies_to_cputime(now - tsk->vtime_snap);
+ return jiffies_to_nsecs(now - tsk->vtime_snap);
}

-static cputime_t get_vtime_delta(struct task_struct *tsk)
+static u64 get_vtime_delta(struct task_struct *tsk)
{
unsigned long now = READ_ONCE(jiffies);
- cputime_t delta, other;
+ u64 delta, other;

/*
* Unlike tick based timing, vtime based timing never has lost
@@ -700,7 +700,7 @@ static cputime_t get_vtime_delta(struct task_struct *tsk)
* elapsed time. Limit account_other_time to prevent rounding
* errors from causing elapsed vtime to go negative.
*/
- delta = jiffies_to_cputime(now - tsk->vtime_snap);
+ delta = jiffies_to_nsecs(now - tsk->vtime_snap);
other = account_other_time(delta);
WARN_ON_ONCE(tsk->vtime_snap_whence == VTIME_INACTIVE);
tsk->vtime_snap = now;
@@ -710,9 +710,7 @@ static cputime_t get_vtime_delta(struct task_struct *tsk)

static void __vtime_account_system(struct task_struct *tsk)
{
- cputime_t delta_cpu = get_vtime_delta(tsk);
-
- account_system_time(tsk, irq_count(), cputime_to_nsecs(delta_cpu));
+ account_system_time(tsk, irq_count(), get_vtime_delta(tsk));
}

void vtime_account_system(struct task_struct *tsk)
@@ -727,15 +725,10 @@ void vtime_account_system(struct task_struct *tsk)

void vtime_account_user(struct task_struct *tsk)
{
- cputime_t delta_cpu;
-
write_seqcount_begin(&tsk->vtime_seqcount);
tsk->vtime_snap_whence = VTIME_SYS;
- if (vtime_delta(tsk)) {
- u64 nsecs;
- delta_cpu = get_vtime_delta(tsk);
- account_user_time(tsk, cputime_to_nsecs(delta_cpu));
- }
+ if (vtime_delta(tsk))
+ account_user_time(tsk, get_vtime_delta(tsk));
write_seqcount_end(&tsk->vtime_seqcount);
}

@@ -776,9 +769,7 @@ EXPORT_SYMBOL_GPL(vtime_guest_exit);

void vtime_account_idle(struct task_struct *tsk)
{
- cputime_t delta_cpu = get_vtime_delta(tsk);
-
- account_idle_time(cputime_to_nsecs(delta_cpu));
+ account_idle_time(get_vtime_delta(tsk));
}

void arch_vtime_task_switch(struct task_struct *prev)
@@ -818,7 +809,7 @@ u64 task_gtime(struct task_struct *t)

gtime = t->gtime;
if (t->vtime_snap_whence == VTIME_SYS && t->flags & PF_VCPU)
- gtime += cputime_to_nsecs(vtime_delta(t));
+ gtime += vtime_delta(t);

} while (read_seqcount_retry(&t->vtime_seqcount, seq));

@@ -851,7 +842,7 @@ void task_cputime(struct task_struct *t, u64 *utime, u64 *stime)
if (t->vtime_snap_whence == VTIME_INACTIVE || is_idle_task(t))
continue;

- delta = cputime_to_nsecs(vtime_delta(t));
+ delta = vtime_delta(t);

/*
* Task runs either in user or kernel space, add pending nohz time to
--
2.7.4