linux-kernel - Re: [PATCH v6 1/4] sched/clock: interface to allow timestamps early in boot

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Message-ID: <aed54345-b752-e93a-8be7-96df9b083f6c@oracle.com>
Date:   Wed, 27 Sep 2017 09:16:00 -0400
From:   Pasha Tatashin <pasha.tatashin@...cle.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     linux@...linux.org.uk, schwidefsky@...ibm.com,
        heiko.carstens@...ibm.com, john.stultz@...aro.org,
        sboyd@...eaurora.org, x86@...nel.org, linux-kernel@...r.kernel.org,
        mingo@...hat.com, tglx@...utronix.de, hpa@...or.com,
        douly.fnst@...fujitsu.com
Subject: Re: [PATCH v6 1/4] sched/clock: interface to allow timestamps early
 in boot

Hi Peter,

I am totally happy with removing notsc. This certainly simplifies the 
sched_clock code. Are there any issues with removing existing kernel 
parameters that I should be aware of?

Thank you,
Pasha

On 09/27/2017 09:10 AM, Peter Zijlstra wrote:
> On Wed, Sep 27, 2017 at 02:58:57PM +0200, Peter Zijlstra wrote:
>> (we're violating "notsc" in any case and really should kill that
>> option).
> 
> Something like so; in particular simple_udelay_calibrate() will issue
> RDTSC _way_ early, so there is absolutely no point in then pretending we
> can't use RDTSC for sched_clock.
>