From: john stultz <johnstul@us.ibm.com>
To: Alexandre Pereira Nunes <alexandre.nunes@gmail.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: 2.6.18 tsc clocksource + ntp = excessive drift; acpi_pm does fine.
Date: Tue, 28 Nov 2006 17:03:01 -0800 [thread overview]
Message-ID: <1164762181.5521.49.camel@localhost.localdomain> (raw)
In-Reply-To: <456CCA54.6090504@gmail.com>
On Tue, 2006-11-28 at 21:46 -0200, Alexandre Pereira Nunes wrote:
> Hi,
>
> with default boot I got tsc clocksource selected on an debian's
> 2.6.18-3-k7 SMP build (but UP machine). ntp keeps bothering me with this
> message:
> frequency error 512 PPM exceeds tolerance 500 PPM
Hmmm. Could you send me your dmesg? Also what frequency is your cpu?
Also does booting w/ "noapic" change the behavior?
> If I remove ntp's drift file and restart, it goes fine for a while and
> then it goes with that behaviour again.
> If I remove ntp's drift file, then do a: echo acpi_pm
> >/sys/devices/system/clocksource/clocksource0/available_clocksource ;
I think you mean "current_clocksource" there...
> and then restart ntp, it goes fine "forever".
>
> Any toughs, something I should look at?
>
> I'll be glad to give more feedback.
>
> I don't know if that happened with 2.6.17, but I'm pretty sure that with
> 2.6.16 it was fine.
Yea, its likely the generic timekeeping changes for i386. Previously
(pre-2.6.18) it probably defaulted to the acpi pm timer and was fine.
The new code is a bit more aggressive in trying to use the TSC.
As a short term workaround, you can put "clocksource=acpi_pm" on your
grub line and that will force the clocksource at boot.
thanks
-john
next prev parent reply other threads:[~2006-11-29 1:03 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-11-28 23:46 2.6.18 tsc clocksource + ntp = excessive drift; acpi_pm does fine Alexandre Pereira Nunes
2006-11-29 1:03 ` john stultz [this message]
2006-11-29 1:29 ` Alexandre Pereira Nunes
2006-11-29 11:26 ` Alexandre Pereira Nunes
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