Am Wed, 18 Jan 2012 07:50:49 +0100 schrieb Martin Sugioarto <mar...@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, Martin
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