linux-kernel - Re: x86-tip tsc/tick gripage

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Date:   Wed, 26 Apr 2017 13:39:49 +0200
From:   Mike Galbraith <efault@....de>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Ingo Molnar <mingo@...nel.org>,
        "Paul E. McKenney" <paulmck@...ibm.com>,
        LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
        Thomas Gleixner <tglx@...utronix.de>,
        Frederic Weisbecker <fweisbec@...il.com>
Subject: Re: x86-tip tsc/tick gripage

On Wed, 2017-04-26 at 12:26 +0200, Peter Zijlstra wrote:
> On Wed, Apr 26, 2017 at 10:57:42AM +0200, Mike Galbraith wrote:
> 
> > Both still lose their TSC.
> > 
> > [   11.982468] tsc: Refined TSC clocksource calibration: 2260.999 MHz
> > [   11.994275] clocksource: tsc: mask: 0xffffffffffffffff max_cycles: 0x20974a4d8bb, max_idle_ns: 440795246623 ns
> > [   13.064172] clocksource: Switched to clocksource tsc
> > [  240.247851] clocksource: timekeeping watchdog on CPU23: Marking clocksource 'tsc' as unstable because the skew is too large:
> > [  240.462501] clocksource:                       'tsc' cs_now: 108fe5be09f cs_last: b90a6a0676 mask: ffffffffffffffff
> > [  240.675057] tsc: Marking TSC unstable due to clocksource watchdog
> 
> 
> And they didn't use to? We don't typically write to TSC or TSC_ADJUST
> and thus would not cause such behaviour.

Nope.  The DL980 is my RT jitter test box, which I use all the time. 
 The other makes very spiffy jitter numbers when TSCs get synched up
(crap bios).. well used to before suse maintenance elves got around to
doing the BIOS replacement ;-/  (poor box, say hi to the goldfish)

	-Mike