Re: [PATCH] nohz: make the idle_entrytime/idle_exittime correct

From	Yunhong Jiang <yunhong.jiang@linux.intel.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH] nohz: make the idle_entrytime/idle_exittime correct
Date	2015-09-18 20:50 +0200
Message-ID	<qa8To-2tx-5@gated-at.bofh.it> (permalink)
References	<q9ujg-2iU-11@gated-at.bofh.it> <q9Pe2-7Ti-17@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Thu, Sep 17, 2015 at 11:45:37PM +0200, Thomas Gleixner wrote:
> On Wed, 16 Sep 2015, Yunhong Jiang wrote:
> 
> > Currently the idle_entrytime is updated on idle_entry, idle_exit and
> > get_cpu_idle/iowait_time_us() with non-NULL parameter. This makes the
> > idle_entrytime not the real entrytime anymore. The idle_exittiime is
> > updated when exit tickless state, which can be idle tickless or full
> > tickless.
> 
> If something calls one of the functions then the cpu is not idle. It's
> running code.

I think the get_cpu_idle/iowait_time_us() can be called from other CPUs.

Hmm, I should state this patch as "no idle_entrytime update on
get_cpu_idle/iowait_time_us()". If you think this statement is correct,
I will re-submit a patch for it.

>  
> > Change the idle_entrytime to be updated only when enter idle, the
> > idle_exittime to be updated only when exit idle. Update
> > the get_cpu_idle_iowait_time_us() accordingly.
> 
> And the rationale for this change is?

I tried to check /proc/timer_list for idle_entrytime/idle_exittime, and
noticed this when reading the corresponding code. So no special reason for
this change, just correctness.

Thanks
--jyh

> 
> Thanks,
> 
> 	tglx
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[PATCH] nohz: make the idle_entrytime/idle_exittime correct Yunhong Jiang <yunhong.jiang@linux.intel.com> - 2015-09-17 01:30 +0200
  Re: [PATCH] nohz: make the idle_entrytime/idle_exittime correct Thomas Gleixner <tglx@linutronix.de> - 2015-09-17 23:50 +0200
    Re: [PATCH] nohz: make the idle_entrytime/idle_exittime correct Yunhong Jiang <yunhong.jiang@linux.intel.com> - 2015-09-18 20:50 +0200

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