AMD Enabling "Fast CPPC" For Even Greater Linux Performance & Power Efficiency On Some CPUs

[mateidibu]

You can check if cppc support is present with "lscpu | grep cppc" on Zen4.
It should be exposed.

These additonal options in the BIOS, like ASROCK has (Prefer Cache, Clock, ...) might not present on ASUS.

Besides that, very interesting addition to the kernel. Im wondering why this came quite late, maybe preparing for the Zen5 Release.
My 7950X3D seems not to have support for it, checking lscpu.

On my Pro WS X570-ACE I've had to enable force enable XAPIC, but not X2APIC because that breaks the acpi tables and results in an error in amd-pstate about a missing _CPC object.

Does "dmesg" show anything about pstate?

[dc740]

if I run $ stress --cpu 1 I see the process joggle between random cores instead of being pinned which is why I suspect CPPC is bust with my ASUS X670-P motherboard.

Same can be observed while compiling with 8 cores (-j8), it looks like there isn't any structure as to which cores are being utilized. Ideally I'd like to see applications share L3 cache inside the same core complex (CCX0: 0-7,16-23 /or/ CCX1: 8-15,24-31) for lowest latency (which should be beneficial to gaming).

lstopo.png















https://i.imgur.com/V2t0oqj.png

Pinning is supported with Feral's gamemode tool:

https://www.phoronix.com/forums/forum/hardware/processors-memory/1451948-feral-s-gamemode-supports-tweaks-for-amd-3d-v-cache

I've tested in on s-tui, some games and even compiling (appending the gamemoderun command in front), and it worked fine for me.

[Wally]

6% perf-per-watt is a pretty nice gain for a laptop use case! Hoping my Framework 13 will support this. 😀