virtualbox.org

Hi
Please, help me to solve the following problem:
- guest runs perfect with 1 CPU assigned, but runs very slow (up to total hung) when multiple CPU are assigned.
Host:
- CPU: AMD Epyc 2401P
- MB: MZ31-AR0 (firmware F03e)
- OS: CentOS 7 (1708) / FreeBSD 11.1-RELEASE (p6) (tried with both OSes - no difference)
- VirtualBox 5.2.6
Guests:
- Windows 2008 R2 / 2016

I've tried different Paravirtualization Interfaces, tried to turn Hardware Virtualization on/off - no difference.
I've tried to disable SMT Mode as well (i.e. disable hyper-threading in BIOS).

Any suggestions, recommendations, whatever, please.

Logs and vbox configs are attached.

Thank you

Can I have the computer shipped to me (as a loan) until I solve this? I don't have readily available a 24-core, 256 GB RAM system right now...

You're on FreeBSD. They make their own fork. They're usually pretty good about keeping up, but we're not sure about the changes they make to the original VirtualBox.

• I see you have the logs for 1- or 16-CPU configuration. I assume you tried values in between, right?
• Can you quantify "very slow"?
• Do not change the Paravirtualization options. Stick with the defaults.
• Funny that you mentioned the SMT mode. Did you read this? "Does Disabling SMT on a Ryzen 7 CPU Improves its Performance?"

Ok
Provider had updated motherboard firmware. Will check now - if it helps.
If not - I'll install CentOS and contact you for help.
Thank you.

No luck

socratis wrote:Can I have the computer shipped to me (as a loan) until I solve this? I don't have readily available a 24-core, 256 GB RAM system right now...

Sent you PM

socratis wrote:I see you have the logs for 1- or 16-CPU configuration. I assume you tried values in between, right?

Yes. Tried 2, 4, 8, 20. It is funny: the more CPUs assigned to guest - the slower guest running...

socratis wrote:Can you quantify "very slow"?

With one core the installation and first login takes just a few minutes. Guest system responses very quick, etc.
With 16 cores the installation takes much longer. First login takes some minutes and sometimes system falls into BSOD.

socratis wrote:Funny that you mentioned the SMT mode. Did you read this? "Does Disabling SMT on a Ryzen 7 CPU Improves its Performance?"

I had read other topics/articles where system with AMD Ryzen/Epyc fails spontaneously with SMT enabled. So I've tried to disable SMT. But it changed nothing in my case.

Looks line no chances.
With 1 CPU assigned guest works good.
With more than 1 CPU assigned guest falls into BSOD:
"DPC WATCHDOG VIOLATION"
Will try latest stable VB build...

Tried latest test build 5.2.x revision 120822.
No changes.