[smokeping-users] Smokeping graphs from VMware slave is "choppy"

Mon May 5 18:17:55 CEST 2008

More a watcher then a participant, but this is a common problem with
anything that is time sensitive in any VM based implementation.  Voip
phone systems have the same issue with audio recording, playing back and
it becomes very evident with conferencing as the number of people in it
increases.  The solution for most of them is to get a hardware board
that they can use as a timing device (all analog to digital conversion
boards have a clock that you can sync to).

The adjustments mentioned do help but if the box becomes busy (do to any
VM's load) you'll still have the issue.

-----Original Message-----
From: smokeping-users-bounces at lists.oetiker.ch
[mailto:smokeping-users-bounces at lists.oetiker.ch] On Behalf Of Bruce
Mackey
Sent: Monday, May 05, 2008 11:58 AM
To: smokeping-users at lists.oetiker.ch
Subject: Re: [smokeping-users] Smokeping graphs from VMware slave is
"choppy"

I was asked to update the list regarding my VMware slave's data being
choppy.

To see exactly how bad my time drift was I ran a short test script: 
	#! /bin/sh
	while [ "1" = "1" ]
	do
	   date
	   sleep 10
	done
which gave the following output:

Mon May  5 11:12:54 EDT 2008
Mon May  5 11:13:04 EDT 2008
Mon May  5 11:13:14 EDT 2008
Mon May  5 11:15:06 EDT 2008
Mon May  5 11:15:16 EDT 2008
Mon May  5 11:15:26 EDT 2008
Mon May  5 11:15:36 EDT 2008
Mon May  5 11:15:46 EDT 2008
Mon May  5 11:15:56 EDT 2008
Mon May  5 11:16:06 EDT 2008
Mon May  5 11:16:16 EDT 2008
Mon May  5 11:16:26 EDT 2008
Mon May  5 11:16:36 EDT 2008
Mon May  5 11:16:46 EDT 2008
Mon May  5 11:16:56 EDT 2008
Mon May  5 11:18:19 EDT 2008
Mon May  5 11:18:29 EDT 2008
Etc.

Each line took about 17 seconds to print out rather than every 10
seconds.  :-(   The jump in time was caused by the VMware tools
performing a host time sync every minute to try and "catch up" with real
time.

An investigation of the VMware time drift problem led me to try turning
off the APIC in the GUEST image.  I changed the kernel startup in my
grub to not use APIC with the flags "nosmp noapic nolapic" added to the
kernel line in my /boot/grub/menu.lst file. The default image loader
config now looks like:

	title           Ubuntu 7.10, kernel 2.6.22-14-generic (no apic)
	root            (hd0,0)
	kernel          /boot/vmlinuz-2.6.22-14-generic
root=UUID=029655e7-0b4c-4353-902e-b16796989e2a ro quiet splash nosmp
noapic nolapic
	initrd          /boot/initrd.img-2.6.22-14-generic
	quiet

And now my output from the script looks like:
Mon May  5 11:32:20 EDT 2008
Mon May  5 11:32:30 EDT 2008
Mon May  5 11:32:40 EDT 2008
Mon May  5 11:32:50 EDT 2008
Mon May  5 11:33:00 EDT 2008
Mon May  5 11:33:10 EDT 2008
Mon May  5 11:33:20 EDT 2008
Mon May  5 11:33:30 EDT 2008
Mon May  5 11:33:40 EDT 2008
Mon May  5 11:33:50 EDT 2008
Mon May  5 11:34:00 EDT 2008
Mon May  5 11:34:11 EDT 2008
Mon May  5 11:34:21 EDT 2008
Mon May  5 11:34:31 EDT 2008
Mon May  5 11:34:41 EDT 2008
Mon May  5 11:34:51 EDT 2008
Mon May  5 11:35:01 EDT 2008
Mon May  5 11:35:11 EDT 2008
Mon May  5 11:35:21 EDT 2008
Mon May  5 11:35:31 EDT 2008
Mon May  5 11:35:41 EDT 2008
Mon May  5 11:35:51 EDT 2008
Mon May  5 11:36:01 EDT 2008
Mon May  5 11:36:11 EDT 2008
Mon May  5 11:36:21 EDT 2008
Mon May  5 11:36:31 EDT 2008
Mon May  5 11:36:41 EDT 2008
Mon May  5 11:36:51 EDT 2008

This appears to have fixed the graph choppiness AND the excess smoke in
my slave graphs.

-Bruce
-----Original Message-----
From: smokeping-users-bounces at lists.oetiker.ch
[mailto:smokeping-users-bounces at lists.oetiker.ch] On Behalf Of Bruce
Mackey
Sent: Friday, May 02, 2008 3:46 PM
To: smokeping-users at lists.oetiker.ch
Subject: Re: [smokeping-users] Smokeping graphs from VMware slave is
"choppy"

I was using a QEMU/KVM engine, but we are transitioning to the VMware
engine now.

I found one mention
(http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cm
d=displayKC&externalId=916) that the HOST OS's power management system
may cause the VMware GUEST Clocks to vary.  I'm going to try to disable
the APM idling feature on the HOST and see if that helps.

-Bruce

-----Original Message-----
From: smokeping-users-bounces at lists.oetiker.ch
[mailto:smokeping-users-bounces at lists.oetiker.ch] On Behalf Of Stefan
Bethke
Sent: Wednesday, April 30, 2008 10:17 AM
To: Wolfgang Hennerbichler
Cc: smokeping-users at lists.oetiker.ch
Subject: Re: [smokeping-users] Smokeping graphs from VMware slave is
"choppy"

Am 30.04.2008 um 16:06 schrieb Wolfgang Hennerbichler:

> On Apr 30, 2008, at 16:01 , Chris Wilson wrote:
>> Hi Bruce,
>>
>> On Wed, 30 Apr 2008, Bruce Mackey wrote:
>>
>>> I suspect there is some time synching issue involved, but when I 
>>> moved my slave to a VMware image, I started getting choppy graphs.
>>
>> vmware time is all over the place. My advice would be "don't do 
>> that".
>
> I guess the same thing goes for xen? I see similar results in my xen 
> environment.

More or less, this is the same for all virtual machine environments. I
believe that VMware offers a stable time source, but I'm not sure which
kernel, if any, can make use of it.

If you wnat some form of virtualisation which does provide this kind of
timing stability, I've used FreeBSD jails quite successfully. I also
suspects that Solaris zones provide similar behaviour.

Stefan

-- 
Stefan Bethke <stb at lassitu.de>   Fon +49 170 346 0140

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