Only 1 CPU possible on a 4 XEON system?

[Orbiter]

Dear Supporters, Maintainers, Helping Hands,

so far I didn't find any clues for VirtualBox 6.1 recognizing only one CPU on my four XEON 8870 IBM System X3850.

Please help me Obi-Wan Kenobi, you're my only hope...

As I got 40 cores (80 threads) on this machine, I expected much more to find in the settings, but not just one CPU.

Installed is Ubuntu Server 19.10 which detects luckily all of the hardware, all CPUs, the special raid controller, 10G fiber network cards etc. (Ubuntu Server 18.3 LTS didn't find those before, Kernel-related I guess.) - So I wouldn't think there is an issue with Ubuntu Server in general, but I think there is an issue with VirtualBox only.

Has anyone solved this problem so far?

Many thanks in advance!
Orbiter

[scottgus1]

I am assuming that by 'one cpu' you mean that the Virtialbox guest settings CPU slider won't allow you to go past 1. If so, take a look here: I have a 64bit host, but can't install 64bit guests.

Sounds like your Intel VT-x/AMD-V is not on in your computer's BIOS. Unlike the targeting computer, you can't use the multi-CPU Force without this.

[Orbiter]

Yes, I mean the guest settings. The slider can be moved to any position, but the whole bar is red only.

Thanks for your immediate answer and your hint. I will look for it in the BIOS.

[Orbiter]

@scottgus1:
I did successfully install 32bit guests as well as 64bit guests. There was no restriction, but the "number of CPUs" slider had no effect so far. Because of this, I don't expect a problem with 32 or 64 bit.
Generally speaking the IBM System X was made for virtualization (ref. IBM).

But I got news:
Now I can tell much more details about this bug(?), as I took a bunch of time and checked several settings under several circumstances.

So at first I looked for the Virtualization settings in the BIOS as suggested and the most likely option I found was "Intel Virtualization Technology" which was already <Enabled>. Then I made the cross-check by disabling it and after that VirtualBox was complaning it needs VT-x enabled. I think you agree the VT-x requirement is fullfilled.

Then crawling through the other BIOS options, I stumbled over "Cores in CPU Package" set to <ALL> . This let me remembering my wonderment why in the guest settings the number of CPUs slider was slidable, but completely red! Are there simply too many CPUs? Is that possible? Who would complain about too many CPUs? Not me.

As mentioned days before, this machine is equipped with four 10-core XEONs, but the CPU-slider in the guest settings had a maximum of 32 (still all red, what I think of that means "not available"). - But then, guess what! Simply by limiting the cores to 8 per CPU in the BIOS settings, I immediately got a completely green bar at the VBox guest settings CPU slider. For the first time ever I was able to choose from 1 up to 32 CPUs. So far so good, obviously there were too many CPUs from the point of view of Oracle, but I'm still not happy, because the performance in the VM is still lousy. Indeed benchmarks show an increase of computing power corresponding to the number of CPUs I assign to the guest, but I don't "feel" the expected increase in overall performance of the guest while increasing the number of CPUs.

I fear there is still a problem with the number of CPUs...

Maybe it's an additional problem with the network performance in the guests environment? - Has somebody experienced some optimized network parameters for VirtualBox guests on this System X or the host Ubuntu Server? (The guest I'm setting up is a Windows Server 2019 DC).
Every clue is appreciated...

[scottgus1]

Not being able to set more than one in a guest when the host has more than 32 sounds like it could be a bug. You might try a suitable story & data on the Bugtracker.

A guest with more processors requires more scheduling overhead on the host to use the processors, so sliding that slider up will make the guest go slower. Only if your guest is running programs that need more processors should you add more. Modern Windows likes 2 processors. Try two, then increase if you would like to see what happens.

[Orbiter]

Ok, I created a ticket for this bug on the bugtracker...

Concerning the performance of the Windows guests, I will examine the effect of reducing the number of CPUs from currently 8 and 16 CPUs down to 2 and report later. Indeed the guest operating system is Windows Server 2019 supporting 16 cores and I'm curious about the different performance/CPUs rates.

[mpack]

And without a log attached I can pretty much guarantee that ticket will never be looked at.

Plus I have a vague memory of this being reported before, years ago. I guess this hardware spec is too rare to make it a high priority.

[Orbiter]

@mpack:
Thank you for the hint. I'll add a log later.

I would like to point out that this bug is not only specific to IBM System X. I'm sorry to inform you that any existing multi-core machine >32 cores is affected. It's a general bug.

You will agree when I say the more people virtualize, the more cores they want. In my view, Oracle is known for optimization and performance. I am sure they will not ignore this bug as I do not believe they want to limit their VM performance by being incompatible to modern high performance hardware. There is an unambiguous trend having more and more cores...

[mpack]

I would like to point out that this bug is not only specific to IBM System X.

Did I mention the manufacturer? I did not. The rare spec is actually having multiple CPUs on the motherboard, instead of 1 CPU, multiple cores, which means that VT-x/AMD-v management of multiple cores is not all done in one central place. Also, it's not common for the number of cores to be >32.

And I'm not denying that it's a bug, just not a high priority one - a bug report with no log will definitely not change that. I'm sure this will become higher priority when it begins to affect paying customers.

[Orbiter]

@mpack:
I'm sorry if you may have understood it that way, I didn't want to criticize you. I just wanted to explain the difficulty that a log may not help because it is a general bug.

Although all necessary details are mentioned in the error description and my workaround, I will add a log later anyway as soon as I can shut down and go into the BIOS to reset the number of cores. Please stand by

As you rightly mention, it is more likely to be worked on when it affects paying customers. Perhaps it even plays into my hands that systems with many CPUs and multiple cores are more likely to be found with this customer base. Let's see.

[mrkevinhoang]

Thanks OP! you solved my problem. Surprisingly not much search results for "cpu redded out" in VBOX. I lowered each core to 8 and now my VBOX shows green. I was also getting "guru meditation" error where the guest machine goes into a weird state and enters guru meditation. I hope this fixes that one too. Thanks.