From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Fontenot, Nathan" Date: Mon, 26 Oct 2020 19:52:37 +0000 Subject: Re: default cpufreq gov, was: [PATCH] sched/fair: check for idle core Message-Id: <0a3abadf-181e-99dd-1304-86a34505dfe8@amd.com> List-Id: References: <1603211879-1064-1-git-send-email-Julia.Lawall@inria.fr> <34115486.YmRjPRKJaA@kreacher> <20201022120213.GG2611@hirez.programming.kicks-ass.net> <1790766.jaFeG3T87Z@kreacher> <20201022122949.GW2628@hirez.programming.kicks-ass.net> <20201022145250.GK32041@suse.de> <20201022152514.GJ2611@hirez.programming.kicks-ass.net> <1603397435.16275.45.camel@suse.com> <20201023070310.GK2611@hirez.programming.kicks-ass.net> <4a0db95a-1ba2-21f5-5c9d-67b9f82ed130@amd.com> In-Reply-To: <4a0db95a-1ba2-21f5-5c9d-67b9f82ed130@amd.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit To: Tom Lendacky , Peter Zijlstra , Giovanni Gherdovich Cc: "Rafael J. Wysocki" , Mel Gorman , Viresh Kumar , Julia Lawall , Ingo Molnar , kernel-janitors@vger.kernel.org, Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Daniel Bristot de Oliveira , linux-kernel@vger.kernel.org, Valentin Schneider , Gilles Muller , srinivas.pandruvada@linux.intel.com, Linux PM , Len Brown , puwen@hygon.cn, yazen.ghannam@amd.com, kim.phillips@amd.com, suravee.suthikulpanit@amd.com 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