linux-kernel - Re: [PATCH] clocksource: Allow toggling between runtime and persistent clocksource for idle

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Message-ID: <CALAqxLXrPus4EMuXWLgq2qP1pF0=qg-oki0KB=D+Z6N2zPJJ8g@mail.gmail.com>
Date:	Mon, 6 Jul 2015 10:51:05 -0700
From:	John Stultz <john.stultz@...aro.org>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Tony Lindgren <tony@...mide.com>,
	lkml <linux-kernel@...r.kernel.org>,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
	Felipe Balbi <balbi@...com>, Nishanth Menon <nm@...com>,
	Yingjoe Chen <yingjoe.chen@...iatek.com>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH] clocksource: Allow toggling between runtime and
 persistent clocksource for idle

On Mon, Jul 6, 2015 at 8:46 AM, Thomas Gleixner <tglx@...utronix.de> wrote:
> On Mon, 6 Jul 2015, Tony Lindgren wrote:
>> * Thomas Gleixner <tglx@...utronix.de> [150706 07:20]:
>> > On Mon, 6 Jul 2015, Tony Lindgren wrote:
>> The timekeeping accuracy issue certainly needs some thinking, and
>> also the resolution between the clocksources can be different.. In the
>> test case I have the slow timer is always on and of a lower resolution
>> than the ARM global timer being used during runtime.
>>
>> Got some handy timer test in mind you want me to run to provide data
>> on the accuracy?
>
> John Stultz might have something.

You can turn on ntp stats in your ntp.conf and chart the loopstats
data w/ gnuplot:

set terminal png
set output "loopstat.png"
plot "/var/log/ntpstats/loopstats.<dateoftest>" using 2:3 with linespoints


I also have  the drift-log.py and graph-log.py scripts I use here:
https://github.com/johnstultz-work/timetests

But those aren't really ready for mass consumption, as they're
probably not very cross-distro compatible.

thanks
-john
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