linux-kernel - Re: [v1 0/9] Early boot time stamps for x86

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Message-ID: <a3f027ee-c193-2e1f-4f4c-da6cffb80d05@oracle.com>
Date:   Wed, 22 Mar 2017 19:59:43 -0400
From:   Pasha Tatashin <pasha.tatashin@...cle.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org, mingo@...hat.com,
        tglx@...utronix.de, hpa@...or.com
Subject: Re: [v1 0/9] Early boot time stamps for x86

Hi Peter,

Thank you for looking at this patchset.

Yes, I am certain it is 0 or  near 0 on reset on this machine. Because, 
I actually wondered about it, and used stop watch as an alternative way 
to verify the result, twice.

While, I suspect it is often the case that on reset tsc is 0, it is not 
really import, as the offset value is not the important part of the 
project. The important part is that we can cover the whole Linux boot 
process with timestamps, and know where spend time, and avoid 
regressions in the future.

Thank you,
Pasha

On 2017-03-22 16:28, Peter Zijlstra wrote:
> On Wed, Mar 22, 2017 at 04:24:16PM -0400, Pavel Tatashin wrote:
>> - early tsc offset is 549s, so it took over 9 minutes to get through POST,
>>   and GRUB before starting linux
>
> Lol, how cute. You assume TSC starts at 0 on reset.
>