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Message-ID: <20171220125140.awxsp5r6hhrv7c6j@hirez.programming.kicks-ass.net> Date: Wed, 20 Dec 2017 13:51:40 +0100 From: Peter Zijlstra <peterz@...radead.org> To: Patrick Bellasi <patrick.bellasi@....com> Cc: Juri Lelli <juri.lelli@...hat.com>, mingo@...hat.com, rjw@...ysocki.net, viresh.kumar@...aro.org, linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org, tglx@...utronix.de, vincent.guittot@...aro.org, rostedt@...dmis.org, luca.abeni@...tannapisa.it, claudio@...dence.eu.com, tommaso.cucinotta@...tannapisa.it, bristot@...hat.com, mathieu.poirier@...aro.org, tkjos@...roid.com, joelaf@...gle.com, morten.rasmussen@....com, dietmar.eggemann@....com, alessio.balsini@....com, Juri Lelli <juri.lelli@....com>, Ingo Molnar <mingo@...nel.org>, "Rafael J . Wysocki" <rafael.j.wysocki@...el.com> Subject: Re: [RFC PATCH v2 1/8] sched/cpufreq_schedutil: make use of DEADLINE utilization signal On Tue, Dec 05, 2017 at 04:34:10PM +0000, Patrick Bellasi wrote: > On 05-Dec 16:24, Juri Lelli wrote: > However, I'm not an expert, on those systems can we really set a > minimum guaranteed performance level? If you look at the Intel SDM, Volume 3, 14.4 Hardware-Controlled Performance States (HWP), which is the Intel implementation of ACPI CPPC. You'll see that IA32_HWP_CAPABILITIES has a Guaranteed_Performance field and describes that upon changes to this frequency we will receive notifications (Interrupts). If you then look at IA32_HWP_REQUEST, you'll see a Minimum_Performance field, which we can raise up-to the guaranteed level, and would/should contain the DEADLINE stuff. HWP_REQUEST also includes a Desired_Performance field, which is where we want to be for DL+CFS. Trouble is that cpufreq doesn't yet support the various CPPC fields. So we have this comment here at the input side stating what we'd want to do once cpufreq itself grows the interface bits.
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