Query on idle VM on a Windows Host.

jimbo45 said:

Hi folks
Just a query to those more experienced with Windows internals etc. No problem to solve -- just would like some knowlege.

If you have a VM which is in an idle state on a Windows host - you need to gain focus in the VM to be able to use it again.

What I want to know is this purely a hardware interrupt e.g keyboard, mouse, touch screen etc or is there a basic process that cycles continuously checking on any device interrupts. It seems to me that Vmware workstation / player and vbox seem to run at higher cpu load than HYPER-V or KVM / QEMU when the VM doesnt have any activity.

Any ideas. !!!! Just curious as I don't use vmware or oracle's vbox.

cheers
jimbo

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cereberus said:

I think it all comes down to definition of idle. No pc is ever truly idle - always background tasks going on.

A pc is only ever idle in sleep mode, and even then a very low power state.

If using Hyper-V, as a type 1 hypervisor, it is not always appreciated that the host is in really a virtual machine as well.

The Hypervisor fully segregates each vm and the host.

The hypervisor obviously dynamically assigns shared CPU/hardware resources to each vm.

In essence each vm is being run intermittently - kind of like toggling sleep on or off very fast.

Of course, each vm is assigned resources fast enough so from a human perspective, it looks like it is running continuously.

I may be oversimplying things but obviously you need to have focus to enter data, use mouse etc.

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jimbo45 said:

Sounds good -- thanks

but one can also put a computer into total sleep mode where a hardware interrupt wakes it up, restarts the task / dispatch manager etc.

I don't know if you ever worked on the old IBM mainframe series of 1970's e.g MVS/SP but that's how they did it. (You can emulate the old IBM MVS/SP OS on a PC -- use hercules emulator etc) -- amazing though that a modest laptop PC has more processing power and I/O storage than a massive 303X IBM Mainframe with water cooling and huge physical disc drives.

I agree type 1 Hypervisors should be far more efficient which in practice shows they are.

For Windows VM's HYPER-V can be truly excellent however the basic Windows OS doesn't IMHO seem to be geared to running VM's other than grudgingly. Windows server editions particularly the latest 2021/2022 LTSC versions with HYPER-V runs rings around the basic Windows platform whether Home or Pro editions. - Can't say anything about Enterprise or workstation editions as I haven't tested those yet and don't have a license.

Cheers
jimbo

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