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Subject[PATCH v4 3/3] sched/cputime: Add steal time support to full dynticks CPU time accounting
Date
From: Wanpeng Li <wanpeng.li@hotmail.com>

This patch adds guest steal-time support to full dynticks CPU
time accounting. After the following commit:

ff9a9b4c4334 ("sched, time: Switch VIRT_CPU_ACCOUNTING_GEN to jiffy granularity")

... time sampling became jiffy based, even if it's still listened
to ring boundaries, so steal_account_process_tick() is reused
to account how many 'ticks' are stolen-time, after the last accumulation.

Suggested-and-Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
---
v3 -> v4:
* fix grammar errors, thanks Ingo
* cleanup fragile codes, thanks Ingo
v2 -> v3:
* convert steal time jiffies to cputime
v1 -> v2:
* fix divide zero bug, thanks Rik

kernel/sched/cputime.c | 23 ++++++++++++++++-------
1 file changed, 16 insertions(+), 7 deletions(-)

diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
index 75f98c5..9ff036b 100644
--- a/kernel/sched/cputime.c
+++ b/kernel/sched/cputime.c
@@ -257,7 +257,7 @@ void account_idle_time(cputime_t cputime)
cpustat[CPUTIME_IDLE] += (__force u64) cputime;
}

-static __always_inline bool steal_account_process_tick(void)
+static __always_inline unsigned long steal_account_process_tick(void)
{
#ifdef CONFIG_PARAVIRT
if (static_key_false(&paravirt_steal_enabled)) {
@@ -279,7 +279,7 @@ static __always_inline bool steal_account_process_tick(void)
return steal_jiffies;
}
#endif
- return false;
+ return 0;
}

/*
@@ -691,9 +691,13 @@ 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);
+ cputime_t delta_time = get_vtime_delta(tsk);
+ cputime_t steal_time = jiffies_to_cputime(steal_account_process_tick());

- account_system_time(tsk, irq_count(), delta_cpu, cputime_to_scaled(delta_cpu));
+ if (steal_time < delta_time) {
+ delta_time -= steal_time;
+ account_system_time(tsk, irq_count(), delta_time, cputime_to_scaled(delta_time));
+ }
}

void vtime_account_system(struct task_struct *tsk)
@@ -718,13 +722,18 @@ void vtime_gen_account_irq_exit(struct task_struct *tsk)

void vtime_account_user(struct task_struct *tsk)
{
- cputime_t delta_cpu;
+ cputime_t delta_time, steal_time;

write_seqcount_begin(&tsk->vtime_seqcount);
tsk->vtime_snap_whence = VTIME_SYS;
if (vtime_delta(tsk)) {
- delta_cpu = get_vtime_delta(tsk);
- account_user_time(tsk, delta_cpu, cputime_to_scaled(delta_cpu));
+ delta_time = get_vtime_delta(tsk);
+ steal_time = jiffies_to_cputime(steal_account_process_tick());
+
+ if (steal_time < delta_time) {
+ delta_time -= steal_time;
+ account_user_time(tsk, delta_time, cputime_to_scaled(delta_time));
+ }
}
write_seqcount_end(&tsk->vtime_seqcount);
}
--
1.9.1
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