Timekeeping in stable/9
ronald-freebsd8 at klop.yi.org
Sat Jan 21 12:36:47 UTC 2012
On Sat, 21 Jan 2012 10:18:42 +0100, Martin Sugioarto
<martin at sugioarto.com> wrote:
> Am Wed, 18 Jan 2012 07:50:49 +0100
> schrieb Martin Sugioarto <martin at sugioarto.com>:
>> I can confirm this on VirtualBox. I've been running WinXP inside
>> VirtualBox and measured network I/O during downloads. It showed me
>> very high download rates (around 800kB/s) while it's physically
>> possible to download 200kB/s through DSL here (Germany sucks with
>> DSL, even in largest cities, btw!).
>> I correlated this behavior with high disk I/O on the host. That means
>> that the timer issues on the virtual host appear when I start a
>> larger cp job on the host. I also immediately thought that this has
>> something to do with timers.
> Hi everybody,
> I just want to add some information on this. I tested a few things with
> VirtualBox yesterday.
> I switched off ntpd on the host and tested if there are differences,
> but the clock is working correctly on the host. I tested it a few times,
> it is stable, as I expect it to be.
> It seems to be rather a software problem with VirtualBox. I can see that
> when the host is under heavy load (CPU!) the guest does not get enough
> runtime to adjust the clock correctly. After a few minutes there has
> been a difference of 50 seconds between the host and guest clock. And
> furthermore, I don't quite understand how the real time clock works in
> VirtualBox but it seems to slide in the different directions causing
> weird results with progress bars on MS-Windows XP.
> I just want to explain why I thought that I/O influences this. I have
> got my hard disk encrypted, so it puts some load on the CPU, too.
> If you want to test VirtualBox behavior, you can simple dd
> from /dev/random and look at the weird results in VirtualBox.
> I hope it helps further,
As I understand it.
Host: FreeBSD 9
Which one has troubles with its clock? The host or the guest or both?
How many CPU's did you assign to the guest?
Did you install virtualbox guest additions to the guest?
Do you run NTP on the guest XP also? If yes, turn it off. VBox guest
additions can sync the guest clock with the host.
BTW: My experience with VBox is that it is nice for hobby stuff, but not
for heavy load server stuff. VMWare does a better job there.
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