From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Subject: Re: [RFC/RFT] [PATCH 02/10] cpufreq: intel_pstate: Conditional frequency invariant accounting Date: Wed, 16 May 2018 09:16:40 +0200 Message-ID: <20180516071640.GU12217@hirez.programming.kicks-ass.net> References: <20180516044911.28797-1-srinivas.pandruvada@linux.intel.com> <20180516044911.28797-3-srinivas.pandruvada@linux.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20180516044911.28797-3-srinivas.pandruvada@linux.intel.com> Sender: linux-kernel-owner@vger.kernel.org To: Srinivas Pandruvada Cc: tglx@linutronix.de, mingo@redhat.com, bp@suse.de, lenb@kernel.org, rjw@rjwysocki.net, mgorman@techsingularity.net, x86@kernel.org, linux-pm@vger.kernel.org, viresh.kumar@linaro.org, juri.lelli@arm.com, linux-kernel@vger.kernel.org List-Id: linux-pm@vger.kernel.org On Tue, May 15, 2018 at 09:49:03PM -0700, Srinivas Pandruvada wrote: > intel_pstate has two operating modes: active and passive. In "active" > mode, the in-built scaling governor is used and in "passive" mode, > the driver can be used with any governor like "schedutil". In "active" > mode the utilization values from schedutil is not used and there is > a requirement from high performance computing use cases, not to read > any APERF/MPERF MSRs. In this case no need to use CPU cycles for > frequency invariant accounting by reading APERF/MPERF MSRs. > With this change frequency invariant account is only enabled in > "passive" mode. WTH is active/passive? Is passive when we select performance governor? Also; you have to explain why using APERF/MPERF is bad in that case. Why do they care if we read those MSRs during the tick?