vm shows less CPU then host

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vm shows less CPU then host

Postby SeventhSon27 » 6. Dec 2017, 12:27

Hi!

I have Windows10 Enterprise ans I see 4 CPU in device manager.
At the same time all the VMs(win/lin) show only 2 CPU.
Who steal 2 CPU-Windows10-host or VirtualBox(last version)?
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Re: vm shows less CPU then host

Postby mpack » 6. Dec 2017, 12:34

How could the guest have the same number of vCPUs as the host has? That would leave the host with none. Do you think that would make the host run well? Do you think the guest would work well on a crippled host?

The number of vCPUs assigned to the guest is configured in the VM recipe. Don't allocate all of the host's cores to a VM. And remember that threads are not cores.

If you need to continue this discussion then provide a VM log file. With the VM fully shut down, right click it in the GUI. Select "Show Log" and save "VBox.log" (ONLY) to a zip file. Attach the zip here.
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Re: vm shows less CPU then host

Postby SeventhSon27 » 7. Dec 2017, 05:32

You are asking very strange questions. I have huge practice with VirtualBox and it always shows all the host's CPU inside any VM.
I run VB on the other Win7 host with 4 CPU and I see the same(4 CPU) inside any VM.
I think that this is only W10 issue. I will try to install on this host Win7 on the separate partition to analizy this issue.
Attachments
W10-2017-11-28-12-27-34.7z
W10 log
(20.94 KiB) Downloaded 2 times
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Re: vm shows less CPU then host

Postby BillG » 7. Dec 2017, 05:59

Not really strange. It is not usual to assign all of the host CPUs to a guest. For example if you were running 4 Windows 7 vms and two windows 8.1 vms on a host with 16 CPUs, it would be common practice to assign each vm 2 CPUs only.

You can certainly assign all of the host CPUs to the guest(s), but it could cause problems if the vms are working hard. If you can see 4 processors in device manager in a guest OS, that vm must have 4 processors allocated to it in its settings. It is certainly not a Windows 10 issue.
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Re: vm shows less CPU then host

Postby socratis » 7. Dec 2017, 07:44

VM settings » System » Processor » Processor(s):
That's where you set the amount of processors your VM will see. But, as others have warned you over and over again; do NOT assign all of them to your VM.

See: CPU Cores versus threads and Why is it a bad idea to allocate as many VCPUs as there are physical CPUs?
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Re: vm shows less CPU then host

Postby mpack » 7. Dec 2017, 10:13

VBox.log wrote:00:00:10.309725 CPUM: Physical host cores: 2

As I suspected. 2 cores, 4 threads.
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Re: vm shows less CPU then host

Postby socratis » 7. Dec 2017, 10:28

Oops, it didn't even occur to me to take a look at the logs :shock:
Thanks mpack...
If you obfuscate any information requested, I will obfuscate my response. These are virtual UUIDs, not real ones.
Do NOT reply with the "QUOTE" button, please use the "POST REPLY", at the bottom of the form.
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