From 45eacc692771bd2b1ea3d384e6345cab3da10861 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Wed, 15 May 2013 22:16:32 +0200 Subject: vtime: Use consistent clocks among nohz accounting While computing the cputime delta of dynticks CPUs, we are mixing up clocks of differents natures: * local_clock() which takes care of unstable clock sources and fix these if needed. * sched_clock() which is the weaker version of local_clock(). It doesn't compute any fixup in case of unstable source. If the clock source is stable, those two clocks are the same and we can safely compute the difference against two random points. Otherwise it results in random deltas as sched_clock() can randomly drift away, back or forward, from local_clock(). As a consequence, some strange behaviour with unstable tsc has been observed such as non progressing constant zero cputime. (The 'top' command showing no load). Fix this by only using local_clock(), or its irq safe/remote equivalent, in vtime code. Reported-by: Mike Galbraith Suggested-by: Mike Galbraith Cc: Steven Rostedt Cc: Paul E. McKenney Cc: Ingo Molnar Cc: Thomas Gleixner Cc: Peter Zijlstra Cc: Borislav Petkov Cc: Li Zhong Cc: Mike Galbraith Signed-off-by: Frederic Weisbecker Signed-off-by: Ingo Molnar --- include/linux/vtime.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'include/linux/vtime.h') diff --git a/include/linux/vtime.h b/include/linux/vtime.h index 71a5782d8c59..b1dd2db80076 100644 --- a/include/linux/vtime.h +++ b/include/linux/vtime.h @@ -34,7 +34,7 @@ static inline void vtime_user_exit(struct task_struct *tsk) } extern void vtime_guest_enter(struct task_struct *tsk); extern void vtime_guest_exit(struct task_struct *tsk); -extern void vtime_init_idle(struct task_struct *tsk); +extern void vtime_init_idle(struct task_struct *tsk, int cpu); #else static inline void vtime_account_irq_exit(struct task_struct *tsk) { @@ -45,7 +45,7 @@ static inline void vtime_user_enter(struct task_struct *tsk) { } static inline void vtime_user_exit(struct task_struct *tsk) { } static inline void vtime_guest_enter(struct task_struct *tsk) { } static inline void vtime_guest_exit(struct task_struct *tsk) { } -static inline void vtime_init_idle(struct task_struct *tsk) { } +static inline void vtime_init_idle(struct task_struct *tsk, int cpu) { } #endif #ifdef CONFIG_IRQ_TIME_ACCOUNTING -- cgit v1.2.3