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Date: Thu, 6 Sep 2018 17:14:57 -0700 From: Dietmar Eggemann <dietmar.eggemann@....com> To: Quentin Perret <quentin.perret@....com> Cc: peterz@...radead.org, rjw@...ysocki.net, linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org, gregkh@...uxfoundation.org, mingo@...hat.com, morten.rasmussen@....com, chris.redpath@....com, patrick.bellasi@....com, valentin.schneider@....com, vincent.guittot@...aro.org, thara.gopinath@...aro.org, viresh.kumar@...aro.org, tkjos@...gle.com, joel@...lfernandes.org, smuckle@...gle.com, adharmap@...eaurora.org, skannan@...eaurora.org, pkondeti@...eaurora.org, juri.lelli@...hat.com, edubezval@...il.com, srinivas.pandruvada@...ux.intel.com, currojerez@...eup.net, javi.merino@...nel.org Subject: Re: [PATCH v6 04/14] PM / EM: Expose the Energy Model in sysfs On 09/06/2018 07:09 AM, Quentin Perret wrote: > Hi Dietmar, > > On Wednesday 05 Sep 2018 at 23:56:43 (-0700), Dietmar Eggemann wrote: >> On 08/20/2018 02:44 AM, Quentin Perret wrote: >>> Expose the Energy Model (read-only) of all performance domains in sysfs >>> for convenience. To do so, add a kobject to the CPU subsystem under the >>> umbrella of which a kobject for each performance domain is attached. >>> >>> The resulting hierarchy is as follows for a platform with two >>> performance domains for example: >>> >>> /sys/devices/system/cpu/energy_model >>> ├── pd0 >>> │ ├── cost >>> │ ├── cpus >>> │ ├── frequency >>> │ └── power >> >> cpus (cpumask of the perf domain), frequency (OPP's of the perf domain) and >> power (values at those OPP's) are somehow easy to grasp, cost is definitely >> not. >> >> You have this nice description in em_pd_energy() what cost actually is. >> IMHO, might be worth repeating this at least in the patch header here. > > Hmm, this patch introduces the sysfs interface, not the 'cost' field > itself. As long as 'cost' is documented in the patch that introduces it > we should be good no ? I mean this patch header tells you _where_ the > fields of the structure are exposed. _What_ the structure is all about > is a different story. Mmmh, so maybe a EAS related documentation file explaining this interface as well, which can be introduced later is the solution here? I'm just not 100% convinced that those cost values are self-explanatory like the other three items: root@...0:~# ls /sys/devices/system/cpu/energy_model/pd0/ cost cpus frequency power root@...0:~# cat /sys/devices/system/cpu/energy_model/pd0/* 96 129 163 201 245 0-3 533000 999000 1402000 1709000 1844000 28 70 124 187 245 > But yeah, in any case, a reminder shouldn't hurt I guess, if you really > want one :-) Nothing which should hold this patch-set back though.
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