So, I'm reading about some improvements to the new Linux kernel. -Something I use to chase when I was on Linux and part of why I chose Arch initially. Of course I never noticed any of the 'performance improvements'.
-So, I'm thinking... Where are the benchmarks, or quantification of performance improvements?
And then this comment from David Huang seems to nail the reason:
It's really frustrating to see AMD kept shipping code that's not gonna actually work at all.
The 3D V-cache optimizer driver requires x86_sched_itmt_flags() to be returned in x86_die_flags() to function (i.e. let the kernel prioritize threads to 3D V-cache die), otherwise the core prioritizing scheduling would only gonna work within a single CCD rather than selecting the preferred CCD first, then selecting the highest performance cores. 7950X3D definitely needs that, it's also the whole point of this driver. But that flag is only enabled for heterogeneous configurations like Strix Point because AMD added a feature check for X86_FEATURE_AMD_HETEROGENEOUS_CORES there before returning the flag in x86_die_flags().
The whole preferred core scheduling thing on Linux is just a few AMD kernel engineers following Intel's implementation without a clue how they worked, and how to test them to ensure they work as expected.
With Linux, you're trusting your hardware, and homes to hobbyist developers that don't know what they're doing.