Messages in this thread | | | Subject | Re: Fw: [External] Re: [RFC] Documentation: Add documentation for new performance_profile sysfs class (Also Re: [PATCH 0/4] powercap/dtpm: Add the DTPM framework) | From | Mark Pearson <> | Date | Mon, 19 Oct 2020 14:49:11 -0400 |
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Hi
> On 19/10/2020 14:43, Hans de Goede <hdegoede@redhat.com> wrote: > Hi, > > On 10/18/20 2:31 PM, Rafael J. Wysocki wrote: >> On Sun, Oct 18, 2020 at 11:41 AM Hans de Goede <hdegoede@redhat.com> wrote: >>> >>> Hi, >>> >>> On 10/16/20 4:51 PM, Rafael J. Wysocki wrote: >>>> On Fri, Oct 16, 2020 at 1:11 PM Hans de Goede <hdegoede@redhat.com> wrote: >>>>> >>>>> <note folding the 2 threads we are having on this into one, adding every one from both threads to the Cc> >>>>> >>>>> Hi, >>>>> >>>>> On 10/14/20 5:42 PM, Rafael J. Wysocki wrote: >>>>>> On Wed, Oct 14, 2020 at 4:06 PM Hans de Goede <hdegoede@redhat.com> wrote: >>>>>>> On 10/14/20 3:33 PM, Rafael J. Wysocki wrote: >>>>> >>>>> <snip> >>>>> >>>>>>>> First, a common place to register a DPTF system profile seems to be >>>>>>>> needed and, as I said above, I wouldn't expect more than one such >>>>>>>> thing to be present in the system at any given time, so it may be >>>>>>>> registered along with the list of supported profiles and user space >>>>>>>> will have to understand what they mean. >>>>>>> >>>>>>> Mostly Ack, I would still like to have an enum for DPTF system >>>>>>> profiles in the kernel and have a single piece of code map that >>>>>>> enum to profile names. This enum can then be extended as >>>>>>> necessary, but I want to avoid having one driver use >>>>>>> "Performance" and the other "performance" or one using >>>>>>> "performance-balanced" and the other "balanced-performance", etc. >>>>>>> >>>>>>> With the goal being that new drivers use existing values from >>>>>>> the enum as much as possible, but we extend it where necessary. >>>>>> >>>>>> IOW, just a table of known profile names with specific indices assigned to them. >>>>> >>>>> Yes. >>>>> >>>>>> This sounds reasonable. >>>>>> >>>>>>>> Second, irrespective of the above, it may be useful to have a >>>>>>>> consistent way to pass performance-vs-power preference information >>>>>>>> from user space to different parts of the kernel so as to allow them >>>>>>>> to adjust their operation and this could be done with a system-wide >>>>>>>> power profile attribute IMO. >>>>>>> >>>>>>> I agree, which is why I tried to tackle both things in one go, >>>>>>> but as you said doing both in 1 API is probably not the best idea. >>>>>>> So I believe we should park this second issue for now and revisit it >>>>>>> when we find a need for it. >>>>>> >>>>>> Agreed. >>>>>> >>>>>>> Do you have any specific userspace API in mind for the >>>>>>> DPTF system profile selection? >>>>>> >>>>>> Not really. >>>>> >>>>> So before /sys/power/profile was mentioned, but that seems more like >>>>> a thing which should have a set of fixed possible values, iow that is >>>>> out of scope for this discussion. >>>> >>>> Yes. >>>> >>>>> Since we all seem to agree that this is something which we need >>>>> specifically for DPTF profiles maybe just add: >>>>> >>>>> /sys/power/dptf_current_profile (rw) >>>>> /sys/power/dptf_available_profiles (ro) >>>>> >>>>> (which will only be visible if a dptf-profile handler >>>>> has been registered) ? >>>>> >>>>> Or more generic and thus better (in case other platforms >>>>> later need something similar) I think, mirror the: >>>>> >>>>> /sys/bus/cpu/devices/cpu#/cpufreq/energy_performance_* bits >>>>> for a system-wide energy-performance setting, so we get: >>>>> >>>>> /sys/power/energy_performance_preference >>>>> /sys/power/energy_performance_available_preferences >>>> >>>> But this is not about energy vs performance only in general, is it? >>>> >>>>> (again only visible when applicable) ? >>>>> >>>>> I personally like the second option best. >>>> >>>> But I would put it under /sys/firmware/ instead of /sys/power/ and I >>>> would call it something like platform_profile (and >>>> platform_profile_choices or similar). >>> >>> Currently we only have dirs under /sys/firmware: >>> >>> [hans@x1 ~]$ ls /sys/firmware >>> acpi dmi efi memmap >>> >>> But we do have /sys/firmware/apci/pm_profile: >>> >>> Documentation/ABI/stable/sysfs-acpi-pmprofile >>> >>> What: /sys/firmware/acpi/pm_profile >>> Date: 03-Nov-2011 >>> KernelVersion: v3.2 >>> Contact: linux-acpi@vger.kernel.org >>> Description: The ACPI pm_profile sysfs interface exports the platform >>> power management (and performance) requirement expectations >>> as provided by BIOS. The integer value is directly passed as >>> retrieved from the FADT ACPI table. >>> Values: For possible values see ACPI specification: >>> 5.2.9 Fixed ACPI Description Table (FADT) >>> Field: Preferred_PM_Profile >>> >>> Currently these values are defined by spec: >>> 0 Unspecified >>> 1 Desktop >>> 2 Mobile >>> 3 Workstation >>> 4 Enterprise Server >>> ... >>> >>> Since all platforms which we need this for are ACPI based >>> (and the involved interfaces are also all ACPI interfaces) >>> how about: >>> >>> /sys/firmware/acpi/platform_profile >>> /sys/firmware/acpi/platform_profile_choices >>> >>> ? >>> >>> I think this goes nice together with /sys/firmware/acpi/pm_profile >>> although that is read-only and this is a read/write setting. >>> >>> Rafel, would: >>> >>> /sys/firmware/acpi/platform_profile >>> /sys/firmware/acpi/platform_profile_choices >>> >>> work for you ? >> >> Yes, it would. > > Great. So I think hat means that we have the most important part > for moving forward with this. > > So I guess the plan for this now looks something like this. > > 1. Rewrite my API docs RFC to update it for the new > /sys/firmware/acpi/platform_profile[_choices] > plan (should be easy and a bunch of stuff like the "type" bit can > just be dropped) > > 2. Add code somewhere under drivers/acpi which allows code from else where > to register itself as platform_profile handler/provider. > > Rafael, any suggestions / preference for where this should be added under > drivers/acpi ? In a new .c file perhaps ? > > 3.1 Use the code from 2 to add support for platform-profile selection in > thinkpad_acpi (something for me or Mark Pearson) to do > 3.2 Use the code from 2 to add support for platform-profile selection > to hp-wmi > 3.3 (and to other drivers in the future). > > > An open question is who will take care of 1. and 2. Mark (Pearson) > do you feel up to this? or do you want me to take care of this? > > Regards, > > Hans >
Definitely up for (2) and will happily have a go at number (1).
If there's an example of something similar I can look at for reference that would be helpful :)
Mark
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