Ryzen 3000 Series Boost Behavior

[possiblydog]

Hi everyone,

 

I installed Unraid trial a few days ago and I love it. I'm not using for storage, but rather to passthrough GPUs to many different VMs.

 

I have a new Ryzen 9 3900x, and it's currently running 2 Win10 VMs. 1 for my workstation, and one to run Steam games. I use in home streaming to stream from the Steam box to the workstation. This is absolutely killer because of the peace of mind of not running untrusted code on my main machine.

 

Anyway, that all works fine. However, I'm noticing some real performance loss in single threaded workloads vs running on Windows natively. Many benchmark scores are about 15% lower. I believe the reason for this is that the processor is not boosting up to

4.6 GHz like it does in Windows. It maxes out at 4.2 ghz. Is this a limitation of unraid, the Linux 4.X kernel, or something else? Multithreaded benchmarks run at close to native speeds.

 

My next question is about KVM (I think). I notice that KVM presents all cores to Windows as vanilla virtual cores, so Windows' scheduler cannot distinguish between real cores and HT cores. Natively, Windows has a bias for scheduling on real cores, but since that information isn't passed through KVM, the scheduler is made dumber. Is there some config that I'm missing?

 

Thanks very much!

Edited July 29, 2019 by possiblydog

[david279]

Be honest unRaid and Linux in general is so multithreaded that it won't be to often you would see that 4.6. The number is based on 1 or 2 core heavy workloads. The normal all core for the 3900x is something like 4.3 and if temps are too high you won't see that. 

[belliash]

Windows sees it as 8 core CPU without HT because both kernel and qemu have troubles with Ryzen and SMT. However New kernel and qemu fix that, but you need to enable topoext. I will write some how to when I find a while. 

[trott]

8 hours ago, belliash said:

Windows sees it as 8 core CPU without HT because both kernel and qemu have troubles with Ryzen and SMT. However New kernel and qemu fix that, but you need to enable topoext. I will write some how to when I find a while. 

thanks, waiting for it now, I'm thinking build an Unraid server with 3700x but worry about there might be issue with Ryzen

[belliash]

There are some issues, but they do not influent on virtualization and guests. In my case, I cannot achieve the advertised CPU boost speed and I needed to apply some patches on top of Linux kernel in order to make k10temp recognizing CPU and reporting its temperature. Also I have applied a PCI quirks patch, that allows to start VM with GPU passthrough. However I have contacted AMD support regarding this issue and seems they are aware of the problem and the upcoming AGESA 1.0.0.3ABB update should fix it, so this patch will be no longer required.

[brinx]

AGESA 1.0.0.3ABB has to be added to Bios am I right? If so what will happen when OEM of the motherboard will not update their bios?

[belliash]

On 7/31/2019 at 5:38 AM, trott said:

thanks, waiting for it now, I'm thinking build an Unraid server with 3700x but worry about there might be issue with Ryzen

https://www.reddit.com/r/Amd/comments/ckr5f4/amd_ryzen_3000_series_linux_support_and/

8 hours ago, brinx said:

AGESA 1.0.0.3ABB has to be added to Bios am I right? If so what will happen when OEM of the motherboard will not update their bios?

Thats right.