linux-kernel - Re: rc5+tip/master: Marking clocksource 'tsc' as unstable because the skew is too large:

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Message-ID: <20160630094919.GB17833@pd.tnic>
Date:	Thu, 30 Jun 2016 11:49:19 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Peter Zijlstra <peterz@...radead.org>, x86-ml <x86@...nel.org>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: rc5+tip/master: Marking clocksource 'tsc' as unstable because
 the skew is too large:

On Thu, Jun 30, 2016 at 10:40:47AM +0200, Thomas Gleixner wrote:
> On Wed, 29 Jun 2016, Borislav Petkov wrote:
> > On Mon, Jun 27, 2016 at 10:06:31PM +0200, Borislav Petkov wrote:
> > > Hey Thomas,
> > > 
> > > Just started seeing this now during testing of Rafael's s/r fix:
> > > 
> > > [   24.973955] clocksource: timekeeping watchdog on CPU3: Marking clocksource 'tsc' as unstable because the skew is too large:
> > > [   24.987744] clocksource:                       'acpi_pm' wd_now: 2df835 wd_last: a6bb64 mask: ffffff
> > > [   24.999587] clocksource:                       'tsc' cs_now: 2bbe793d1e cs_last: 296e28763c mask: ffffffffffffffff
> > > [   25.013400] clocksource: Switched to clocksource acpi_pm
> > > 
> > > In the previous boot it was CPU1.
> > 
> > And here it is again:
> > 
> > ...
> > [   15.720833] IPv6: ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready
> > [   32.883077] clocksource: timekeeping watchdog on CPU1: Marking clocksource 'tsc' as unstable because the skew is too large:
> > [   32.896986] clocksource:                       'acpi_pm' wd_now: 8e147 wd_last: 531b43 mask: ffffff
> > [   32.908834] clocksource:                       'tsc' cs_now: 385f4b6d1e cs_last: 354328bcea mask: ffffffffffffffff
> > [   32.922293] clocksource: Switched to clocksource acpi_pm
> 
> What's the tsc freqeuency on your machine?

$ dmesg | grep -i tsc
[    0.000000] tsc: Fast TSC calibration using PIT
[    0.000000] tsc: Detected 4013.406 MHz processor
[    5.034357] tsc: Refined TSC clocksource calibration: 4013.511 MHz
[    5.034359] clocksource: tsc: mask: 0xffffffffffffffff max_cycles: 0x39da38233dd, max_idle_ns: 440795253361 ns
[    6.068153] clocksource: Switched to clocksource tsc
[   32.883077] clocksource: timekeeping watchdog on CPU1: Marking clocksource 'tsc' as unstable because the skew is too large:
[   32.908834] clocksource:                       'tsc' cs_now: 385f4b6d1e cs_last: 354328bcea mask: ffffffffffffffff

P0 is 4Ghz and TSC is ticking at P0 so 4GHz too. 4-ish, it seems :)

-- 
Regards/Gruss,
    Boris.

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