NetBSD Problem Report #57300

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Date: Sun, 26 Mar 2023 10:17:31 +0000 (UTC)
From: nan@chinadtrace.org
Reply-To: nan@chinadtrace.org
To: gnats-bugs@NetBSD.org
Subject: Time system is not accurate on NetBSD VM
X-Send-Pr-Version: www-1.0

>Number:         57300
>Category:       misc
>Synopsis:       Time system is not accurate on NetBSD VM
>Confidential:   no
>Severity:       serious
>Priority:       low
>Responsible:    misc-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Mar 26 10:20:00 +0000 2023
>Last-Modified:  Mon Mar 27 10:45:01 +0000 2023
>Originator:     Nan Xiao
>Release:        9.3
>Organization:
>Environment:
NetBSD localhost 9.3 NetBSD 9.3 (GENERIC) #0: Thu Aug  4 15:30:37 UTC 2022  mkrepro@mkrepro.NetBSD.org:/usr/src/sys/arch/amd64/compile/GENERIC amd64
>Description:
Hi NetBSD community,

My NetBSD is a VirtualBox virtual machine, and host machine is macOS Ventura 13.2.1. I find the date command doesn't display time correctly, and it is very advanced than actual time.

E.g.:

-bash-5.1$ date; sleep 10; date
Sun Mar 26 18:59:44 +08 2023
Sun Mar 26 19:00:13 +08 2023

Actually the time just passes 10 seconds, but date command shows it has passes nearly half a minute. Not sure whether this could be accounted as NetBSD bug, or VirtualBox bug, thanks!

Best Regards
Nan Xiao
>How-To-Repeat:

>Fix:

>Audit-Trail:
From: mlelstv@serpens.de (Michael van Elst)
To: gnats-bugs@netbsd.org
Cc: 
Subject: Re: misc/57300: Time system is not accurate on NetBSD VM
Date: Sun, 26 Mar 2023 10:44:17 -0000 (UTC)

 nan@chinadtrace.org writes:

 >-bash-5.1$ date; sleep 10; date
 >Sun Mar 26 18:59:44 +08 2023
 >Sun Mar 26 19:00:13 +08 2023

 >Actually the time just passes 10 seconds, but date command shows it has passes nearly half a minute. Not sure whether this could be accounted as NetBSD bug, or VirtualBox bug, thanks!


 "sleep 10" waits 1000 clock interrupts. If that lasts 10 seconds, the
 emulation of clock interrupts is correct. The exact delay can vary
 with host speed and load.

 "date" looks at the current timecounter. If that advances 30 seconds
 in 10 seconds, the emulation of the timecounter is bad. Fortunately we
 have multiple, e.g.:

 # sysctl kern.timecounter
 kern.timecounter.choice = TSC(q=3000, f=3292677360 Hz) clockinterrupt(q=0, f=100 Hz) ichlpcib0(q=1000, f=3579545 Hz) hpet0(q=2000, f=14318180 Hz) ACPI-Fast(q=1000, f=3579545 Hz) lapic(q=-100, f=99859155 Hz) i8254(q=100, f=1193182 Hz) dummy(q=-1000000, f=1000000 Hz)
 kern.timecounter.hardware = TSC
 kern.timecounter.timestepwarnings = 0

 By setting kern.timecounter.hardware to one of the choices you may get
 a timecounter that works better.

 While the choice "clockinterrupt" avoids discrepancies between "sleep"
 and "date", the result might not be accurate. For many cases a different
 choice (if there is any) is better.


From: Nan Xiao <nan@chinadtrace.org>
To: gnats-bugs@netbsd.org, misc-bug-people@netbsd.org,
 gnats-admin@netbsd.org, netbsd-bugs@netbsd.org
Cc: 
Subject: Re: misc/57300: Time system is not accurate on NetBSD VM
Date: Mon, 27 Mar 2023 17:28:03 +0800

 Hi Michael,

 Thanks very much for your reply! "clockinterrupt" seems working for my
 VM environment.


 On 2023/3/26 6:50 PM, Michael van Elst wrote:
 > The following reply was made to PR misc/57300; it has been noted by GNATS.
 > 
 > From: mlelstv@serpens.de (Michael van Elst)
 > To: gnats-bugs@netbsd.org
 > Cc: 
 > Subject: Re: misc/57300: Time system is not accurate on NetBSD VM
 > Date: Sun, 26 Mar 2023 10:44:17 -0000 (UTC)
 > 
 >  nan@chinadtrace.org writes:
 >  
 >  >-bash-5.1$ date; sleep 10; date
 >  >Sun Mar 26 18:59:44 +08 2023
 >  >Sun Mar 26 19:00:13 +08 2023
 >  
 >  >Actually the time just passes 10 seconds, but date command shows it has passes nearly half a minute. Not sure whether this could be accounted as NetBSD bug, or VirtualBox bug, thanks!
 >  
 >  
 >  "sleep 10" waits 1000 clock interrupts. If that lasts 10 seconds, the
 >  emulation of clock interrupts is correct. The exact delay can vary
 >  with host speed and load.
 >  
 >  "date" looks at the current timecounter. If that advances 30 seconds
 >  in 10 seconds, the emulation of the timecounter is bad. Fortunately we
 >  have multiple, e.g.:
 >  
 >  # sysctl kern.timecounter
 >  kern.timecounter.choice = TSC(q=3000, f=3292677360 Hz) clockinterrupt(q=0, f=100 Hz) ichlpcib0(q=1000, f=3579545 Hz) hpet0(q=2000, f=14318180 Hz) ACPI-Fast(q=1000, f=3579545 Hz) lapic(q=-100, f=99859155 Hz) i8254(q=100, f=1193182 Hz) dummy(q=-1000000, f=1000000 Hz)
 >  kern.timecounter.hardware = TSC
 >  kern.timecounter.timestepwarnings = 0
 >  
 >  By setting kern.timecounter.hardware to one of the choices you may get
 >  a timecounter that works better.
 >  
 >  While the choice "clockinterrupt" avoids discrepancies between "sleep"
 >  and "date", the result might not be accurate. For many cases a different
 >  choice (if there is any) is better.
 >  
 >  

 -- 
 Best Regards
 Nan Xiao(肖楠)

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