linux-kernel - Re: [PATCH] x86: Export tsc related information in sysfs

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Date:	Tue, 25 May 2010 22:50:31 -0400
From:	Brian Bloniarz <bmb@...enacr.com>
To:	john stultz <johnstul@...ibm.com>
CC:	"H. Peter Anvin" <hpa@...or.com>,
	Dan Magenheimer <dan.magenheimer@...cle.com>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Andi Kleen <andi@...stfloor.org>,
	Arjan van de Ven <arjan@...radead.org>,
	Venkatesh Pallipadi <venki@...gle.com>, chris.mason@...cle.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86: Export tsc related information in sysfs

john stultz wrote:
> On Tue, 2010-05-25 at 20:16 -0400, Brian Bloniarz wrote:
>> On 05/24/2010 09:33 PM, Brian Bloniarz wrote:
>>> So what's wrong with just adding a
>>> /sys/devices/system/clocksource/clocksource0/tsc_khz?
>> As an RFC:
>>
>> Add clocksource.sys_register & sys_unregister so the
>> current clocksource can add supplemental information to
>> /sys/devices/system/clocksource/clocksource0/
>>
>> Export tsc_khz when current_clocksource==tsc so that
>> daemons like NTP can account for the variability of
>> calibration results.
> 
> I think this is a bad idea, as it creates an ABI that is arch AND
> machine specific, which will cause portability problems in applications
> that expect the interface to be there.

It's an arch-independent ABI that returns ENOENT on
unsupported platforms ;)

Could you please explain what you envision as an
arch-independent solution to this problem?
I guess the tsc_long_calibration=1 alternative is
one.
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