Corrected gettimeofday() test code

[Don Bowman]

From: Kris Kennaway [mailto:kris at obsecurity.org]
> 
> I forwarded the reports of timecounter problems to phk, and he asked
> that people who are seeing timecounter problems provide FULL details
> of their system configuration, including:
> 
> * dmesg
> 
> * kernel configuration
> 
> * compiler options
> 
> * time-related system configuration (whether ntpd/timed/ntpdate is
> running, and if so whether it's correcting for a seriously drifting
> clock)
> 
> * The kernel timecounter configuration, e.g. the
> kern.timecounter.method and kern.timecounter.hardware sysctls, and
> whether changing them has any effect.
> 
> * The exact output of the corrected test program below (the original
> would give spurious errors if it didn't run at least once a second,
> which may have been confusing some people if their systems were
> sufficiently loaded).
> 
> * The system status when the problem is observed (i.e. does it only
> occur under load; what else is running at the time)
> 

For this config (below), kern.timecounter.method=0 reproduces the
problem, kern.timecounter.method=1 does not.

Output in 'error' case:
1070147643.248866 1070147651.028646 1070147643.248866 1070147651.028646
1070147656.287818 1070147664.067692 1070147656.287818 1070147664.067692
1070147659.326429 1070147667.106238 1070147659.326429 1070147667.106238
1070147668.370071 1070147676.149884 1070147668.370071 1070147676.149884
1070147681.433111 1070147689.212926 1070147681.433111 1070147689.212926
1070147683.418743 1070147691.198632 1070147683.418743 1070147691.198632

problem shows up within ~30s of starting the test program, and the messages
will come out about once per 1-5s period after that, not regularly.

kern.timecounter.hardware: TSC

on this machine, i have others which are i8254 which do it too.

hw.ncpu=1

compiler flags:
COPTFLAGS= -O2 -pipe -malign-loops=4 -malign-jumps=4 -malign-functions=4
-mcpu=i686 -march=i686 -fno-gcse -g



machine is running 4.7-RELEASE-p2.

dmesg, kernel config attached.


Intel-specific functions:
Version 00000673:
Type 0 - Original OEM
Family 6 - Pentium Pro
Model 7 - Pentium III/Pentium III Xeon - external L2 cache
Stepping 3
Reserved 0

from cpuid.

ntpd -p /var/run/ntpd.pid -b -g -A
runs.

Clock does not drift much, less than 2s/day. Clock is 
stepped when system boots. There is a chimer on our router 
which broadcasts ntp time every minute. ntpd is not
observed to step clock.

On the 8254 machine [a dual 0f27 xeon, 533 FSB with HTT enabled]
1070147645.119531 1070148340.497729 1070148339.-693880469 1070148340.497729

both systems were unloaded. This was with the corrected program
you included.

--don

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___#
___# GENERIC -- Generic kernel configuration file for FreeBSD/i386
___#
___# For more information on this file, please read the handbook section on
___# Kernel Configuration Files:
___#
___#    http://www.FreeBSD.org/handbook/kernelconfig-config.html
___#
___# The handbook is also available locally in /usr/share/doc/handbook
___# if you've installed the doc distribution, otherwise always see the
___# FreeBSD World Wide Web server (http://www.FreeBSD.org/) for the
___# latest information.
___#
___# An exhaustive list of options and more detailed explanations of the
___# device lines is also present in the ./LINT configuration file. If you are
___# in doubt as to the purpose or necessity of a line, check first in LINT.
___#
___# $FreeBSD: src/sys/i386/conf/GENERIC,v 1.246.2.39 2002/03/24 13:19:10 wilko Exp $
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___				# Allow ncr to attach legacy NCR devices when 
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___device		asr		# DPT SmartRAID V, VI and Adaptec SCSI RAID
___device		dpt		# DPT Smartcache - See LINT for options!
___device		mly		# Mylex AcceleRAID/eXtremeRAID
___device          ciss		# Compaq SmartRAID 5* series
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___device		aac		# Adaptec FSA RAID, Dell PERC2/PERC3
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___pseudo-device	splash
___# syscons is the default console driver, resembling an SCO console
___device		sc0	at isa? flags 0x100
___# Enable this and PCVT_FREEBSD for pcvt vt220 compatible console driver
___#device		vt0	at isa?
___#options 	XSERVER			# support for X server on a vt console
___#options 	FAT_CURSOR		# start with block cursor
___# If you have a ThinkPAD, uncomment this along with the rest of the PCVT lines
___#options 	PCVT_SCANSET=2		# IBM keyboards are non-std
___# Floating point support - do not disable.
___device		npx0	at nexus? port IO_NPX irq 13
___# Power management support (see LINT for more options)
___#device		apm0    at nexus? disable flags 0x20 # Advanced Power Management
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___device		sio0	at isa? port IO_COM1 flags 0x10 irq 4
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___# PCI Ethernet NICs that use the common MII bus controller code.
___# NOTE: Be sure to keep the 'device miibus' line in order to use these NICs!
___#device		miibus		# MII bus support
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___options 	CPU_ENABLE_SSE
___#options		IPFW2
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