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)

[Mark Pearson]

<Note - switched my email address to my more open source non-outlook 
based address>

On 2020-10-16 10:32 a.m., Mark Pearson wrote:
> ------------------------------------------------------------------------
> *From:* Elia Devito <eliadevito@xxxxxxxxx>
> *Sent:* October 16, 2020 10:26
> *To:* Rafael J. Wysocki <rafael@xxxxxxxxxx>; Hans de Goede 
> <hdegoede@xxxxxxxxxx>
> *Cc:* Daniel Lezcano <daniel.lezcano@xxxxxxxxxx>; Srinivas Pandruvada 
> <srinivas.pandruvada@xxxxxxxxxxxxxxx>; Lukasz Luba 
> <lukasz.luba@xxxxxxx>; Linux Kernel Mailing List 
> <linux-kernel@xxxxxxxxxxxxxxx>; Linux PM <linux-pm@xxxxxxxxxxxxxxx>; 
> Zhang, Rui <rui.zhang@xxxxxxxxx>; Bastien Nocera <hadess@xxxxxxxxxx>; 
> Mark Pearson <mpearson@xxxxxxxxxx>; Limonciello, Mario 
> <Mario.Limonciello@xxxxxxxx>; Darren Hart <dvhart@xxxxxxxxxxxxx>; Andy 
> Shevchenko <andy@xxxxxxxxxxxxx>; Mark Gross <mgross@xxxxxxxxxxxxxxx>; 
> Benjamin Berg <bberg@xxxxxxxxxx>; linux-acpi@xxxxxxxxxxxxxxx 
> <linux-acpi@xxxxxxxxxxxxxxx>; platform-driver-x86@xxxxxxxxxxxxxxx 
> <platform-driver-x86@xxxxxxxxxxxxxxx>
> *Subject:* [External] Re: [RFC] Documentation: Add documentation for new 
> performance_profile sysfs class (Also Re: [PATCH 0/4] powercap/dtpm: Add 
> the DTPM framework)
> Hi,
>
> In data venerdì 16 ottobre 2020 13:10:54 CEST, Hans de Goede ha scritto:
> > <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@xxxxxxxxxx> 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.
> >
> > 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
> >
> > (again only visible when applicable) ?
> >
> > I personally like the second option best.
> >
> > Regards,
> >
> > Hans
>
> between the two, the second seems to me more appropriate.
> Considering that the various profiles interact with thermal behaviors 
> what do
> you think of something like:
>
> /sys/power/thermal_profile_available_profiles
> /sys/power/thermal_profile_profile
>
> Regards,
> Elia
I'm good with either but I do find 'profile_profile' slightly awkward to 
say out loud (even though it's logically correct :))

How about just:
/sys/power/platform_profile
/sys/power/platform_profile_available

As it covers the platform as a whole - fans, temperature, power, and 
anything else that ends up getting thrown in?

Mark