[Info-vax] clock problems with OpenVMS x86 on VirtualBox

[Dan Cross]

In article <25f6569c-fa35-46de-8a5d-0a886a11e899n at googlegroups.com>,
gah4  <gah4 at u.washington.edu> wrote:
>On Monday, May 15, 2023 at 7:14:08 AM UTC-7, Dan Cross wrote:
>
>(snip)
>
>> And separately there are issues of IO: in a type-1 scenario, IO 
>> is offloaded to another VM (or even a separate system) on behalf 
>> of a guest; that introduces non-determinate latency and 
>> noisy-neighbor problems without careful construction. Even with 
>> SR-IOV and passthru techniques for hypervisor-bypass, there are 
>> classes of IO that must go through the host, and these can take 
>> arbitrarily long. What do you do when the `outb` to your 
>> virtualized console UART blocks? There are some techniques to 
>> amortize the overhead of these events (posted IOs, for example) 
>> but they are not perfect. 
> 
>(snip)
>
>and then there is NFS, where I/O can take arbitrarily long, even
>without a hypervisor.  
>
>I once sold a machine that clients had NFS mounts from. 
>That is, hard mounts.

The one that'll really flip your noggin is if your virtualized
storage device is backed by a file on an NFS server somewhere...

	- Dan C.