linux-kernel - Re: System time drifts when processor idle.

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Date:	Sat, 28 Aug 2010 14:45:10 +0200
From:	jean-philippe francois <jp.francois@...ove.com>
To:	john stultz <johnstul@...ibm.com>
Cc:	Venkatesh Pallipadi <venki@...gle.com>, Lin Ming <lin@...g.vg>,
	"H. Peter Anvin" <hpa@...or.com>, linux-acpi@...r.kernel.org,
	LKML <linux-kernel@...r.kernel.org>, jslaby@...e.cz
Subject: Re: System time drifts when processor idle.

2010/8/28 john stultz <johnstul@...ibm.com>:

>> > Huh. hpet was not what I would have expected.
>> >
>> >
>> > So first, two experiments:
>> >
>> > 1) Does booting with "clock=acpi_pm" cause the issue to disappear?
>> >

Yes, the problem usually show up quite quickly, and I think I have let
my script run
for a long enough time to say it does not occur with clock=acpi_pm

>> > 2) Does booting with "nohz=off" cause the issue to disappear?
>> >
Not tested yet.

>
> jean-philippe: Is the drift always in 5 minute increments? Can you leave
> it idle for 3 minutes and see a similar 3 minute delay, or is it always
> in units of 5 ?
>
That is interesting !
I think I have always seen 5 minutes or multiples of this delay. I
will try to leave it running for a longer
period of time and come back to you with more results. If you look at
the first message of this thread
(on linux-acpi) the delay is first 5, then 10 minutes.

Thank you for your interest.

Jean-Philippe
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