From: John Sigler <linux.kernel@free.fr>
To: linux-kernel@vger.kernel.org,
linux-rt-users <linux-rt-users@vger.kernel.org>
Cc: johnstul@us.ibm.com, tglx@linutronix.de
Subject: System clock frequency offset changes drastically across reboots
Date: Mon, 03 Sep 2007 12:21:37 +0200 [thread overview]
Message-ID: <46DBE031.1090808@free.fr> (raw)
[ Re-sending... Please feel free to comment, even if you don't have
"The Solution". I'd just like to get some feedback. ]
Hello everyone,
I'm using 2.6.20.7-rt8 on a P3.
I've noticed that the frequency offset of my system clock (computed
either by ntpd, or by hand) changes drastically across reboots.
By drastically, I mean +/- 60 ppm every time I reboot.
Apparently this is caused by some imprecision in the frequency
estimation done in calculate_cpu_khz() (arch/i386/kernel/tsc.c)
My brutally crude work-around was to skip the computation altogether and
hard-code the "correct" value for cpu_khz.
http://linux.kernel.free.fr/cpu_khz.adlink
Has this issue been investigated more thoroughly by other users?
Regards.
next reply other threads:[~2007-09-03 10:22 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-09-03 10:21 John Sigler [this message]
-- strict thread matches above, loose matches on Subject: below --
2007-07-27 11:56 System clock frequency offset changes drastically across reboots John Sigler
2007-07-30 7:59 ` John Sigler
2007-08-03 7:47 ` John Sigler
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