NetBSD Problem Report #44227

From www@NetBSD.org  Sun Dec 12 23:06:36 2010
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Date: Sun, 12 Dec 2010 23:06:36 +0000 (UTC)
From: lacombar@gmail.com
Reply-To: lacombar@gmail.com
To: gnats-bugs@NetBSD.org
Subject: 5.99.25 misdects CPU frequency
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>Number:         44227
>Category:       kern
>Synopsis:       5.99.25 misdects CPU frequency
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Dec 12 23:10:00 +0000 2010
>Last-Modified:  Mon Dec 13 00:15:03 +0000 2010
>Originator:     Arnaud Lacombe
>Release:        5.99.25
>Organization:
n/a
>Environment:
-
>Description:
From http://mail-index.netbsd.org/current-users/2010/04/17/msg013120.htm, dmesg says:

NetBSD 5.99.13 (GENERIC) #14: Sun Jun 21 22:34:42 EDT 2009
        al@nybbas:/nbsd/src/build/obj/sys/arch/i386/compile/GENERIC
total memory = 3037 MB
avail memory = 2977 MB
timecounter: Timecounters tick every 10.000 msec
timecounter: Timecounter "i8254" frequency 1193182 Hz quality 100
LENOVO.                        2743CTO (ThinkPad SL400)
mainbus0 (root)
cpu0 at mainbus0 apid 0: Intel 686-class, 1795MHz, id 0x6fd
cpu1 at mainbus0 apid 1: Intel 686-class, 1795MHz, id 0x6fd

5.99.25 says:

NetBSD 5.99.25 (GENERIC) #0: Tue Apr 27 22:29:06 EDT 2010
        al@nybbas:/nbsd/src/build/obj/sys/arch/i386/compile/GENERIC
total memory = 3037 MB
avail memory = 2977 MB
timecounter: Timecounters tick every 10.000 msec
timecounter: Timecounter "i8254" frequency 1193182 Hz quality 100
LENOVO.                        2743CTO (ThinkPad SL400)
mainbus0 (root)
cpu0 at mainbus0 apid 0: Intel 686-class, 2154MHz, id 0x6fd
cpu1 at mainbus0 apid 1: Intel 686-class, 2154MHz, id 0x6fd

The CPU frequency is wrong is the second case. I cannot say right now whether or not 5.99.41 gets the correct answer.

This may be responsible of the ~16% time drift I'm seeing sometime with 5.99.25. The error between the 2 frequencies is the same ratio, ~16%.
>How-To-Repeat:

>Fix:

>Audit-Trail:
From: Thomas Klausner <wiz@NetBSD.org>
To: gnats-bugs@NetBSD.org
Cc: 
Subject: Re: kern/44227: 5.99.25 misdects CPU frequency
Date: Mon, 13 Dec 2010 01:11:57 +0100

 On Sun, Dec 12, 2010 at 11:10:01PM +0000, lacombar@gmail.com wrote:
 > >Synopsis:       5.99.25 misdects CPU frequency

 When booting with a few Xeon W3520, 2660MHz, the cpu line reported by
 NetBSD switches between
 cpu0 at mainbus0 apid 0: Intel 686-class, 2672MHz, id 0x106a5
 and
 cpu0 at mainbus0 apid 0: Intel 686-class, 3207MHz, id 0x106a5

 This also causes
 -timecounter: Timecounter "TSC" frequency 2672865880 Hz quality 3000
 +timecounter: Timecounter "TSC" frequency 3207398120 Hz quality 3000

 For this reason I've switched the timecounter to avoid the time
 drifting problem:
 # grep timecounter /etc/sysctl.conf
 kern.timecounter.hardware=hpet0

 Then I at least don't see any effects of this weirdness.

 I've seen this behaviour for a long time now (at least in 5.99.15,
 5.99.22, 5.99.23, 5.99.24, 5.99.36, 5.99.39) also with different
 numbers (e.g. 3741MHz). I didn't notice it in the last month or so,
 but there were less reboots than usual. Sometimes reboots change the
 MHz.
  Thomas

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