linux-kernel - Re: [RESEND PATCH v2 2/2] power/idle: enhance the precision of sleep

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Message-ID: <CAN2waFuETjxzRwST_EGY4GhxFUZZsOPkysrcBsKCSmcp5hV+UQ@mail.gmail.com>
Date:	Fri, 17 Jun 2016 19:18:30 +0800
From:	Zhaoyang Huang <zhaoyang.huang@...aro.org>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
	mingo@...hat.com, peterz@...radead.org,
	Zhaoyang Huang (黄朝阳) 
	<zhaoyang.huang@...eadtrum.com>
Subject: Re: [RESEND PATCH v2 2/2] power/idle: enhance the precision of sleep_length

On 17 June 2016 at 17:27, Thomas Gleixner <tglx@...utronix.de> wrote:
> On Fri, 17 Jun 2016, Zhaoyang Huang wrote:
>> There should be a gap between tick_nohz_idle_enter and
>> tick_nohz_get_sleep_length when idle, which will cause the
>> sleep_length is not very precised. Change it in this patch.
>
> What kind of imprecision are we talking about? Seconds, nanoseconds or
> lightyears?
>
> Your changelog lacks any form of useful information.
>
> Thanks,
>
>         tglx
>
>
sorry for the confusion. The imprecision can be caused by, for
example, the callback function registered for CPU_PM_ENTER, which may
consume a period of time within the 'idle' time. Besides, I also
wonder why not calc the 'sleep_length' in the
tick_nohz_get_sleep_length?  This value is calculated at very
beginning of the idle in current approach.