On 10/23/2020 12:46 PM, Tom Lendacky wrote: > On 10/23/20 2:03 AM, Peter Zijlstra wrote: >> On Thu, Oct 22, 2020 at 10:10:35PM +0200, Giovanni Gherdovich wrote: >>> * for the AMD EPYC machines we haven't yet implemented frequency invariant >>> accounting, which might explain why schedutil looses to ondemand on all >>> the benchmarks. >> >> Right, I poked the AMD people on that a few times, but nothing seems to >> be forthcoming :/ Tom, any way you could perhaps expedite the matter? > > Adding Nathan to the thread to help out here. > > Thanks, > Tom Thanks Tom, diving in... > >> >> In particular we're looking for some X86_VENDOR_AMD/HYGON code to run in >> >> arch/x86/kernel/smpboot.c:init_freq_invariance() >> >> The main issue is finding a 'max' frequency that is not the absolute max >> turbo boost (this could result in not reaching it very often) but also >> not too low such that we're always clipping. I've started looking into this and have a lead but need to confirm that the frequency value I'm getting is not an absolute max. >> >> And while we're here, IIUC AMD is still using acpi_cpufreq, but AFAIK >> the chips have a CPPC interface which could be used instead. Is there >> any progress on that? >> Correct, AMD uses acpi_cpufreq. The newer AMD chips do have a CPPC interface (not sure how far back 'newer' covers). I'll take a look at schedutil and cppc_cpufreq and the possibility of transitioning to them for AMD. -Nathan
