[PATCH] sched/cputime: add steal time support to full dynticks CPU time accounting

[Wanpeng Li <kernellwp@gmail.com>]

From: Wanpeng Li <wanpeng.li@hotmail.com>

This patch adds steal guest time support to full dynticks CPU time 
accounting. After commit ff9a9b4c(sched, time: Switch VIRT_CPU_ACCOUNTING_GEN 
to jiffy granularity), time is jiffy based sampling even if it's 
still listened to ring boundaries, so steal_account_process_tick() 
is reused to account how much 'ticks' are steal time after the 
last accumulation. 

Suggested-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 <rkrcmar@redhat.com>
Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
---
 kernel/sched/cputime.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
index 75f98c5..b96bd8f 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;
 }
 
 /*
@@ -691,8 +691,11 @@ static cputime_t get_vtime_delta(struct task_struct *tsk)
 
 static void __vtime_account_system(struct task_struct *tsk)
 {
+	unsigned long steal_time = steal_account_process_tick();
 	cputime_t delta_cpu = get_vtime_delta(tsk);
 
+	delta_cpu = steal_time ? (delta_cpu -
+		jiffies_to_cputime(steal_time)) : delta_cpu;
 	account_system_time(tsk, irq_count(), delta_cpu, cputime_to_scaled(delta_cpu));
 }
 
@@ -723,7 +726,11 @@ void vtime_account_user(struct task_struct *tsk)
 	write_seqcount_begin(&tsk->vtime_seqcount);
 	tsk->vtime_snap_whence = VTIME_SYS;
 	if (vtime_delta(tsk)) {
+		unsigned long steal_time = steal_account_process_tick();
 		delta_cpu = get_vtime_delta(tsk);
+
+		delta_cpu = steal_time ? (delta_cpu -
+			jiffies_to_cputime(steal_time)) : delta_cpu;
 		account_user_time(tsk, delta_cpu, cputime_to_scaled(delta_cpu));
 	}
 	write_seqcount_end(&tsk->vtime_seqcount);
-- 
1.9.1