Viewing topic Ryzen 3D cache cpus on Linux

Ryzen 3D cache cpus on Linux

Liemaeu 6 Feb 2024

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I got a Ryzen 9 7900X3D cpu for my Linux gaming pc.

It has 12 cores, but only 6 of them use the 3D cache:
!lstopo output

It's usually better for gaming to use only the 3D cache cores. Will they be selected automatically on Linux? Or do I have to set manually (by taskset/WINE_CPU_TOPOLOGY)?
I have used only Intel cpus before, I'm not into AMD/Ryzen. The only posts I have found on this are for Windows. What is the current state on Linux?

I'm on openSUSE Tumbleweed, kernel 6.7.2-1-default, KDE Plasma 5.27.10, X11.
I have a MSI B650 Gaming Plus Wifi motherboard with up-to-date Bios (7E26v17, 2023-12-14).

(Don't get me wrong. The performance of my new 7900X3D is great. I'm just curious if I set everything correctly to work on max efficiency.)

Last edited by Liemaeu on 6 Feb 2024 at 9:51 am UTC

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Highball 6 Feb 2024

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If nobody knows off of the top of their head here on GOL.

I found this.
Phoronix Review

Usually if something needs to be enabled Phoronix will say in their review. I didn't see anything, but there is a huge comment section, so if you ask there surely people will respond.

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LoudTechie 6 Feb 2024

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If nobody knows off of the top of their head here on GOL.

I found this.
Phoronix Review

Usually if something needs to be enabled Phoronix will say in their review. I didn't see anything, but there is a huge comment section, so if you ask there surely people will respond.

According to your(very good) link is this's (at least for the manufacturer drivers) a windows exclusive feature.
"On the Linux side, there haven't been any AMD patches to optimize the Linux kernel around this differing of CCD characteristics for cache vs. frequency so that the kernel scheduler would be able to ensure optimized task placement."

Reddit agrees.

Last edited by LoudTechie on 6 Feb 2024 at 4:14 pm UTC

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LoudTechie 6 Feb 2024

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The short answer to your question is: no.

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peta77 6 Feb 2024

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normally you would use "numactl" for such kind of things, also for multi-cpu setup to make sure allocated memory and task aren't assigned to different sockets and they don't switch cores, so cache doesn't need to be refetched, etc.
that's what's usually used in HPC context and does that job quite well.

but i don't know if that requires specific features on the mainboard and/or cpu (or even code changes

) to make it work.. so you'll need to do some research/testing..

good luck!

Last edited by peta77 on 6 Feb 2024 at 8:16 pm UTC

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emphy 7 Feb 2024

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It seems that feral's game mode supports core pinning and parking:

https://github.com/FeralInteractive/gamemode

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Liemaeu 7 Feb 2024

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It seems that feral's game mode supports core pinning and parking:

https://github.com/FeralInteractive/gamemode

Thank you! This is great, I didn't know that. It even autodetects my 7900X3D.

Should I enable parking or pinning? Or is it enabled by default?

Last edited by Liemaeu on 7 Feb 2024 at 1:35 pm UTC

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