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SubjectRe: [PATCH 04/33] cputime: Allow dynamic switch between tick/virtual based cputime accounting
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On Tue, 2013-01-08 at 03:08 +0100, Frederic Weisbecker wrote:

> @@ -439,29 +443,13 @@ void account_idle_ticks(unsigned long ticks)
>
> account_idle_time(jiffies_to_cputime(ticks));
> }
> -
> #endif
>
> +

Spurious newline.

-- Steve

> /*
> * Use precise platform statistics if available:
> */
> #ifdef CONFIG_VIRT_CPU_ACCOUNTING
> -void task_cputime_adjusted(struct task_struct *p, cputime_t *ut, cputime_t *st)
> -{
> - *ut = p->utime;
> - *st = p->stime;
> -}
> -
> -void thread_group_cputime_adjusted(struct task_struct *p, cputime_t *ut, cputime_t *st)
> -{
> - struct task_cputime cputime;
> -
> - thread_group_cputime(p, &cputime);
> -
> - *ut = cputime.utime;
> - *st = cputime.stime;
> -}
> -
> void vtime_account_system_irqsafe(struct task_struct *tsk)
> {
> unsigned long flags;
> @@ -517,8 +505,25 @@ void vtime_account(struct task_struct *tsk)
> }
> EXPORT_SYMBOL_GPL(vtime_account);
> #endif /* __ARCH_HAS_VTIME_ACCOUNT */
> +#endif /* CONFIG_VIRT_CPU_ACCOUNTING */
>
> -#else
> +#ifdef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
> +void task_cputime_adjusted(struct task_struct *p, cputime_t *ut, cputime_t *st)
> +{
> + *ut = p->utime;
> + *st = p->stime;
> +}

Why not keep this out in the open like:

static void __task_cputime_adjusted() {
...
}

#ifdef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
void task_cputime_adjusted(...)
{
__task_cputime_adjusted(p, ut, st);
}

> +
> +void thread_group_cputime_adjusted(struct task_struct *p, cputime_t *ut, cputime_t *st)
> +{
> + struct task_cputime cputime;
> +
> + thread_group_cputime(p, &cputime);
> +
> + *ut = cputime.utime;
> + *st = cputime.stime;
> +}
> +#else /* !CONFIG_VIRT_CPU_ACCOUNTING_NATIVE */
>
> #ifndef nsecs_to_cputime
> # define nsecs_to_cputime(__nsecs) nsecs_to_jiffies(__nsecs)
> @@ -548,6 +553,12 @@ static void cputime_adjust(struct task_cputime *curr,
> {
> cputime_t rtime, utime, total;
>
> + if (vtime_accounting_enabled()) {
> + *ut = curr->utime;
> + *st = curr->stime;

Then here, we can do:

__task_cputime_adjusted(curr, ut, st);
> + return;

Isn't suppose to do basically the same thing, when
vtime_accounting_enabled() is set?

> + }
> +
> utime = curr->utime;
> total = utime + curr->stime;
>
> @@ -601,7 +612,7 @@ void thread_group_cputime_adjusted(struct task_struct *p, cputime_t *ut, cputime
> thread_group_cputime(p, &cputime);
> cputime_adjust(&cputime, &p->signal->prev_cputime, ut, st);
> }
> -#endif
> +#endif /* !CONFIG_VIRT_CPU_ACCOUNTING_NATIVE */
>
> #ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
> static DEFINE_PER_CPU(long, last_jiffies) = INITIAL_JIFFIES;
> @@ -643,6 +654,11 @@ void vtime_account_idle(struct task_struct *tsk)
> account_idle_time(delta_cpu);
> }
>
> +bool vtime_accounting_enabled(void)
> +{
> + return context_tracking_active();
> +}
> +
> static int __cpuinit vtime_cpu_notify(struct notifier_block *self,
> unsigned long action, void *hcpu)
> {
> diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
> index fb8e5e4..314b9ee 100644
> --- a/kernel/time/tick-sched.c
> +++ b/kernel/time/tick-sched.c
> @@ -632,8 +632,11 @@ static void tick_nohz_restart_sched_tick(struct tick_sched *ts, ktime_t now)
>
> static void tick_nohz_account_idle_ticks(struct tick_sched *ts)
> {
> -#ifndef CONFIG_VIRT_CPU_ACCOUNTING
> +#ifndef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
> unsigned long ticks;
> +
> + if (vtime_accounting_enabled())
> + return;

If this can be dynamically changed at runtime, wouldn't some of these
accounting variables get corrupted? Like the last_jiffies per_cpu
variable?

-- Steve

> /*
> * We stopped the tick in idle. Update process times would miss the
> * time we slept as update_process_times does only a 1 tick



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