Re: [PATCH v2] sched/cputime: exclude ktimers threads in irqtime_account_irq

[Yuanhan Zhang]

Hi Sebastian, thanks for your reply.

Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> 于2023年11月30日周四 20:00写道：
>
> On 2023-11-30 17:41:47 [+0800], tiozhang wrote:
> > In CONFIG_PREEMPT_RT kernel, ktimers also calls __do_softirq,
> > so when accounting CPUTIME_SOFTIRQ, ktimers need to be excluded
> > as well as ksoftirqd.
> > Also add this_cpu_ktimers to keep consistency with this_cpu_ksoftirqd.
>
> I'm still not sure what the benefit here is. It says align with
> ksoftirqd but why? Why don't we account softirq time for ksoftirqd (and
> should continue to do so for ktimersd)?

That is my miss. When CONFIG_IRQ_TIME_ACCOUNTING is enabled,
ksoftirqd is counted elsewhere (where ktimers should also be aligned).
Please review my later patch v3.

>
> ktimers runs almost all the time in softirq context. So does every
> force-threaded interrupt. Should we exclude them, too?

For force-threaded interrupt, it counts on CPUTIME_SYSTEM
instead of CPUTIME_IRQ nor CPUTIME_SOFTIRQ.
To me, it does not quite make sense, I'm also thinking of sending a patch
of this, but IMHO it should not be considered in this patch...

>
> Sebastian