linux-kernel - Re: Skylake (XPS 13 9350) TSC is way off

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Message-ID: <CALAqxLVgwmfwkmhHD8dVA-g6iGG-uz3sy0n4cA+tSS0AAaT6YQ@mail.gmail.com>
Date:	Wed, 2 Dec 2015 15:42:34 -0800
From:	John Stultz <john.stultz@...aro.org>
To:	Andy Lutomirski <luto@...nel.org>
Cc:	"Brown, Len" <len.brown@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	X86 ML <x86@...nel.org>,
	"Hunter, Adrian" <adrian.hunter@...el.com>
Subject: Re: Skylake (XPS 13 9350) TSC is way off

On Wed, Dec 2, 2015 at 3:38 PM, John Stultz <john.stultz@...aro.org> wrote:
> On Wed, Dec 2, 2015 at 3:25 PM, Andy Lutomirski <luto@...nel.org> wrote:
>> In case it's at all useful, adjtimex -p says:
>>
>>          mode: 0
>>        offset: 0
>>     frequency: 135641
>>      maxerror: 37498
>>      esterror: 1532
>>        status: 8192
>> time_constant: 2
>>     precision: 1
>>     tolerance: 32768000
>>          tick: 10000
>>      raw time:  1449098317s 671243180us = 1449098317.671243180
>>
>> this suggests a rather small correction, so I really have no idea what
>> "Adjusting tsc more than 11% (8039115 vs 7759462)" means.
>>
>> John, you wrote this code.  What does the error message mean?

Also, is there a behavior issue you're seeing or is this just a
concern about the warning? I assumed it was the first, but digging up
the thread here I'm not sure I see any specific problems listed.

thanks
-john
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