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Date: Tue, 7 Jul 2015 03:24:58 -0700
From: Tony Lindgren <tony@atomide.com>
To: John Stultz <john.stultz@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>, lkml <linux-kernel@vger.kernel.org>,
        "linux-omap@vger.kernel.org" <linux-omap@vger.kernel.org>,
        Felipe Balbi <balbi@ti.com>, Nishanth Menon <nm@ti.com>,
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        "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
        Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH] clocksource: Allow toggling between runtime and
 persistent clocksource for idle
Message-ID: <20150707102458.GR10705@atomide.com>
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* John Stultz <john.stultz@linaro.org> [150706 10:53]:
> On Mon, Jul 6, 2015 at 8:46 AM, Thomas Gleixner <tglx@linutronix.de> wrote:
> > On Mon, 6 Jul 2015, Tony Lindgren wrote:
> >> * Thomas Gleixner <tglx@linutronix.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.

Great thanks, I'll play a bit with those to see how bad the jitter gets.

Regrds,

Tony