Re: zero runtime when negative

[mlelstv%serpens.de@localhost (Michael van Elst)]

dennis.c.ferguson%gmail.com@localhost (Dennis Ferguson) writes:

>The clock maintenance code doesn't need to work like the timecounter code
>does now but there needs to be something it can count on in a virtual 
>environment
>to maintain system clocks properly.  What is that?

The guest system really cannot rely on exact real-time. After all,
what happens if you stop the emulator on the host system or when it
is just slowed down due to load.

It is the task of the host system to provide reasonable approximations
which often means to slow down or speed up "virtual time" in the guest.

I know that Linux (Dom0/parvirtual DomU) doesn't have time keeping problems
and the same is true for NetBSD running on my version of the Amiga emulator.
I also know lots of stories that things don't work smoothly in vmware
and qemu.

Here is a list of "best practices" to prevent time keeping problems
of Linux guests in vmware.

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1006427

Most suggestions have to do with selecting a reasonably working emulated
hardware timecounter. Some suggest VMI, which is a set of paravirtual
drivers that can access a virtual timecounter provided by vmware.

-- 
-- 
                                Michael van Elst
Internet: mlelstv%serpens.de@localhost
                                "A potential Snark may lurk in every tree."