On Sun, 2013-06-02 at 19:33 -0400, Jeff Mahoney wrote:

On 6/1/13 3:41 PM, Stefan Seyfried wrote:

...

Am 23.05.2013 16:23, schrieb Jiri Kosina:

...

On Thu, 23 May 2013, Stefan Seyfried wrote:

...

See https://bugzilla.novell.com/show_bug.cgi?id=821422

all tools I tried (vmstat, top, gkrellm) all report 0% cpu usage. Very unlikely to be true :-)

CONFIG_NOHZ_FULL is very likely the culprit, as there are reports of it causing various CPU accounting breakages. Still being debugged upstream.

It's not getting better with rc3 and from what I read CONFIG_NOHZ_FULL is not some kind of killer feature. Could we disable this until it no longer breaks everything and the kitchen sink?

Mike -

Do I recall correctly that you have a fix for this? Or could Stefan have the bad hardware you were worried about?

The below should fix the accounting woes for unstable tsc boxen. These boxen are excluded from playing tickless though. Frederic sent this out, but it's still not found it's way to Linus for some reason. From: Frederic Weisbecker <fweisbec@gmail.com> To: LKML <linux-kernel@vger.kernel.org> Cc: Frederic Weisbecker <fweisbec@gmail.com>, Steven Rostedt <rostedt@goodmis.org>, "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>, Ingo Molnar <mingo@kernel.org>, Thomas Gleixner <tglx@linutronix.de>, Peter Zijlstra <peterz@infradead.org>, Borislav Petkov <bp@alien8.de>, Li Zhong <zhong@linux.vnet.ibm.com>, Mike Galbraith <efault@gmx.de> Subject: [PATCH 2/8] vtime: Use consistent clocks among nohz accounting Date: Mon, 20 May 2013 18:01:50 +0200 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 <efault@gmx.de> Suggested-by: Mike Galbraith <efault@gmx.de> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Li Zhong <zhong@linux.vnet.ibm.com> Cc: Mike Galbraith <efault@gmx.de> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> --- include/linux/vtime.h | 4 ++-- kernel/sched/core.c | 2 +- kernel/sched/cputime.c | 6 +++--- 3 files changed, 6 insertions(+), 6 deletions(-) diff --git a/include/linux/vtime.h b/include/linux/vtime.h index 71a5782..b1dd2db 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 diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 58453b8..e1a27f9 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -4745,7 +4745,7 @@ void __cpuinit init_idle(struct task_struct *idle, int cpu) */ idle->sched_class = &idle_sched_class; ftrace_graph_init_idle_task(idle, cpu); - vtime_init_idle(idle); + vtime_init_idle(idle, cpu); #if defined(CONFIG_SMP) sprintf(idle->comm, "%s/%d", INIT_TASK_COMM, cpu); #endif diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c index cc2dc3ee..b5ccba2 100644 --- a/kernel/sched/cputime.c +++ b/kernel/sched/cputime.c @@ -747,17 +747,17 @@ void arch_vtime_task_switch(struct task_struct *prev) write_seqlock(¤t->vtime_seqlock); current->vtime_snap_whence = VTIME_SYS; - current->vtime_snap = sched_clock(); + current->vtime_snap = sched_clock_cpu(smp_processor_id()); write_sequnlock(¤t->vtime_seqlock); } -void vtime_init_idle(struct task_struct *t) +void vtime_init_idle(struct task_struct *t, int cpu) { unsigned long flags; write_seqlock_irqsave(&t->vtime_seqlock, flags); t->vtime_snap_whence = VTIME_SYS; - t->vtime_snap = sched_clock(); + t->vtime_snap = sched_clock_cpu(cpu); write_sequnlock_irqrestore(&t->vtime_seqlock, flags); } -- To unsubscribe, e-mail: opensuse-kernel+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse-kernel+owner@opensuse.org