Re: [PATCH 1/5] sched,time: Count actually elapsed irq & softirq time

[Wanpeng Li]

Hi Rik,
2016-07-13 22:50 GMT+08:00 Frederic Weisbecker <fweisbec@xxxxxxxxx>:
> From: Rik van Riel <riel@xxxxxxxxxx>
>
> Currently, if there was any irq or softirq time during 'ticks'
> jiffies, the entire period will be accounted as irq or softirq
> time.
>
> This is inaccurate if only a subset of the time was actually spent
> handling irqs, and could conceivably mis-count all of the ticks during
> a period as irq time, when there was some irq and some softirq time.
>
> This can actually happen when irqtime_account_process_tick is called
> from account_idle_ticks, which can pass a larger number of ticks down
> all at once.
>
> Fix this by changing irqtime_account_hi_update, irqtime_account_si_update,
> and steal_account_process_ticks to work with cputime_t time units, and
> return the amount of time spent in each mode.

Do we need to minus st cputime from idle cputime in
account_idle_ticks() when noirqtime is true? I try to add this logic
w/ noirqtime and idle=poll boot parameter for a full dynticks guest,
however, there is no difference, where I miss?

Regards,
Wanpeng Li