sched/cputime: Complete nsec conversion of tick based accounting

This is the final step toward tick based cputime conversion. Now that
the whole cputime accounting engine accounts in nsecs, we can convert the
very source of the cputime to account in nsecs.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Wanpeng Li <wanpeng.li@hotmail.com>
Link: http://lkml.kernel.org/r/1485832191-26889-26-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

kernel/sched/cputime.c

@@ -75,14 +75,13 @@ void irqtime_account_irq(struct task_struct *curr)
 }
 EXPORT_SYMBOL_GPL(irqtime_account_irq);
 
-static cputime_t irqtime_tick_accounted(cputime_t maxtime)
+static u64 irqtime_tick_accounted(u64 maxtime)
 {
 	struct irqtime *irqtime = this_cpu_ptr(&cpu_irqtime);
-	cputime_t delta;
+	u64 delta;
 
-	delta = nsecs_to_cputime(irqtime->tick_delta);
-	delta = min(delta, maxtime);
-	irqtime->tick_delta -= cputime_to_nsecs(delta);
+	delta = min(irqtime->tick_delta, maxtime);
+	irqtime->tick_delta -= delta;
 
 	return delta;
 }
@@ -91,7 +90,7 @@ static cputime_t irqtime_tick_accounted(cputime_t maxtime)
 
 #define sched_clock_irqtime	(0)
 
-static cputime_t irqtime_tick_accounted(cputime_t dummy)
+static u64 irqtime_tick_accounted(u64 dummy)
 {
 	return 0;
 }
@@ -234,22 +233,19 @@ void account_idle_time(u64 cputime)
  * ticks are not redelivered later. Due to that, this function may on
  * occasion account more time than the calling functions think elapsed.
  */
-static __always_inline cputime_t steal_account_process_time(cputime_t maxtime)
+static __always_inline u64 steal_account_process_time(u64 maxtime)
 {
 #ifdef CONFIG_PARAVIRT
 	if (static_key_false(&paravirt_steal_enabled)) {
-		cputime_t steal_cputime;
-		u64 steal, rounded;
+		u64 steal;
 
 		steal = paravirt_steal_clock(smp_processor_id());
 		steal -= this_rq()->prev_steal_time;
+		steal = min(steal, maxtime);
+		account_steal_time(steal);
+		this_rq()->prev_steal_time += steal;
 
-		steal_cputime = min(nsecs_to_cputime(steal), maxtime);
-		rounded = cputime_to_nsecs(steal_cputime);
-		account_steal_time(rounded);
-		this_rq()->prev_steal_time += rounded;
-
-		return steal_cputime;
+		return steal;
 	}
 #endif
 	return 0;
@@ -258,9 +254,9 @@ static __always_inline cputime_t steal_account_process_time(cputime_t maxtime)
 /*
  * Account how much elapsed time was spent in steal, irq, or softirq time.
  */
-static inline cputime_t account_other_time(cputime_t max)
+static inline u64 account_other_time(u64 max)
 {
-	cputime_t accounted;
+	u64 accounted;
 
 	/* Shall be converted to a lockdep-enabled lightweight check */
 	WARN_ON_ONCE(!irqs_disabled());
@@ -364,9 +360,7 @@ void thread_group_cputime(struct task_struct *tsk, struct task_cputime *times)
 static void irqtime_account_process_tick(struct task_struct *p, int user_tick,
 					 struct rq *rq, int ticks)
 {
-	u64 old_cputime = (__force u64) cputime_one_jiffy * ticks;
-	cputime_t other;
-	u64 cputime;
+	u64 other, cputime = TICK_NSEC * ticks;
 
 	/*
 	 * When returning from idle, many ticks can get accounted at
@@ -376,11 +370,10 @@ static void irqtime_account_process_tick(struct task_struct *p, int user_tick,
 	 * other time can exceed ticks occasionally.
 	 */
 	other = account_other_time(ULONG_MAX);
-	if (other >= old_cputime)
+	if (other >= cputime)
 		return;
 
-	old_cputime -= other;
-	cputime = cputime_to_nsecs(old_cputime);
+	cputime -= other;
 
 	if (this_cpu_ksoftirqd() == p) {
 		/*
@@ -477,8 +470,7 @@ void thread_group_cputime_adjusted(struct task_struct *p, u64 *ut, u64 *st)
  */
 void account_process_tick(struct task_struct *p, int user_tick)
 {
-	cputime_t old_cputime, steal;
-	u64 cputime;
+	u64 cputime, steal;
 	struct rq *rq = this_rq();
 
 	if (vtime_accounting_cpu_enabled())
@@ -489,14 +481,13 @@ void account_process_tick(struct task_struct *p, int user_tick)
 		return;
 	}
 
-	old_cputime = cputime_one_jiffy;
+	cputime = TICK_NSEC;
 	steal = steal_account_process_time(ULONG_MAX);
 
-	if (steal >= old_cputime)
+	if (steal >= cputime)
 		return;
 
-	old_cputime -= steal;
-	cputime = cputime_to_nsecs(old_cputime);
+	cputime -= steal;
 
 	if (user_tick)
 		account_user_time(p, cputime);
@@ -520,7 +511,7 @@ void account_idle_ticks(unsigned long ticks)
 	}
 
 	cputime = ticks * TICK_NSEC;
-	steal = cputime_to_nsecs(steal_account_process_time(ULONG_MAX));
+	steal = steal_account_process_time(ULONG_MAX);
 
 	if (steal >= cputime)
 		return;
@@ -741,6 +732,7 @@ void vtime_account_user(struct task_struct *tsk)
 	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));
 	}