Hey Shyam, I misunderstood that CnQF was a single setting, but it looks like it has 4 different levels, right? Unless there's a major malfunction, I don't think that offering to switch between 2 different policies where the difference is how "static" the performance boosts are is very useful, or comprehensible, to end-users. If CnQF only has a single "on" setting, then this could replace the balanced mode for what you call "static slider", so the end-user can still make a choice and have agency on whether the system tries to save power, or increase performance. If CnQF has multiple levels (Turbo, Performance, Balanced and Quiet, right?), then I don't think it's useful to have a sysfs setting to switch it at runtime, which only confuses user-space and the users. BIOS setting and/or kernel command-line option are the way to go. Did I understand this correctly? On Tue, 6 Sept 2022 at 12:00, Shyam Sundar S K <Shyam-sundar.S-k@xxxxxxx> wrote: > > Hi Bastien, Hans > > On 9/1/2022 7:04 PM, Bastien Nocera wrote: > > On Thu, 1 Sept 2022 at 14:44, Hans de Goede <hdegoede@xxxxxxxxxx> wrote: > >> > >> Hi, > >> > >> On 9/1/22 14:24, Bastien Nocera wrote: > >>> On Thu, 1 Sept 2022 at 13:16, Hans de Goede <hdegoede@xxxxxxxxxx> wrote: > >>>> > >>>> Hi, > >>>> > >>>> On 8/23/22 12:29, Shyam Sundar S K wrote: > >>>>> In this series, support for following features has been added. > >>>>> - "Cool n Quiet Framework (CnQF)" is an extension to the static slider, > >>>>> where the system power can be boosted or throttled independent > >>>>> of the selected slider position. > >>>>> - On the fly, the CnQF can be turned on/off via a sysfs knob. > >>>> > >>>> Thank you. I think that before doing a more in detail review > >>>> we first need to agree on the userspace interactions here. > >>>> > >>>> I've added Bastien, the power-profiles-daemon maintainer > >>>> to the Cc for this. > >>>> > >>>> From a quick peek at the patches I see that currently they do > >>>> the following: > >>>> > >>>> Probe time: > >>>> ----------- > >>>> > >>>> 1. If static slider (classic /sys/firmware/acpi/platform_profile) > >>>> is available register as a platform_profile provider > >>>> > >>>> 2. Query if the BIOS tells us that CnQF should be enable by > >>>> default if yes then unregister the platform_profile provider > >>>> and enable CnQF > >>>> > >>>> > >>>> Run time: > >>>> --------- > >>>> > >>>> Allow turning CnQF on/off by writing a sysfs attribute for this. > >>>> > >>>> 1. When CnQF gets enabled unregister the platform_profile provider > >>>> > >>>> 2. When CnQF gets disabled restore the last set profile and > >>>> register the platform_profile provider > >>>> > >>>> > >>>> Questions/remarks: > >>>> > >>>> 1. If you look at 1. and 2. under "Probe time", you will see that > >>>> when the BIOS requests to have CnQF enabled by default that > >>>> userspace will then still shortly see a platform_profile > >>>> provider. This must be fixed IMHO by checking whether to do > >>>> CnQF by default or not before the initial register call. > >>>> > >>>> 2. What about low-power scenarios ? Currently power-profiles-daemon > >>>> will always advertise a low-power mode even when there is no > >>>> platform-profile support, since this is also a hint for other > >>>> parts of the system to try and conserve power. But when this > >>>> mode is enabled we really want the system to also behave as > >>>> if the old static slider mode is active and set to low-power. > >>>> > >>>> Some ideas: > >>>> a) maybe still have the amd-pmf code register a (different) > >>>> platform_profile provider whn in CnQF mode and have it only > >>>> advertise low-power > >>>> > >>>> b) teach power-profiles-daemon about CnQF and have it > >>>> disable CnQF when entering low-power mode? > >>>> > >>>> c) make the CnQF code in PMF take the charge level into > >>>> account and have it not go "full throttle" when the chare > >>>> is below say 25% ? > >>>> > >>>> 3. Bastien, can power-profiles-daemon deal with > >>>> /sys/firmware/acpi/platform_profile disappearing or > >>>> appearing while it is running? > >>> > >>> No, it doesn't. > >>> > >>> It expects the platform_profile file to be available on startup, at > >>> worse with the choices not yet filled in. It doesn't handle the > >>> platform_profile file going away, it doesn't handle the > >>> platform_profile_choices file changing after it's been initially > >>> filled in, and it doesn't support less than one power profile being > >>> made available, and only supports hiding the performance profile if > >>> the platform doesn't support it. > >> > >> Ok, so this means that if we go with these changes as currently > >> proposed that if a user uses the sysfs file to turn CnQF on/off > >> they will need to restart power-profile-daemon. > >> > >> I think that that is acceptable given that the user needs to manually > >> poke things anyway. We should probably document this in the documentation > >> for the sysfs attribute (as well as in newer versions of the p-p-d > >> docs/README). > >> > >>> Some of those things we could change/fix, some other things will not. > >>> If the platform_profile_choices file only contained a single item, > >>> then power-profiles-daemon would just export the "low-power" and > >>> "balanced" profiles to user-space, as it does on unsupported hardware. > >> > >> Right. > >> > >>> The profiles in power-profiles-daemon are supposed to show the user > >>> intent, which having a single setting would effectively nullify. > >> > >> Yes that was my understanding too. > >> > >>> It's unclear to me how CnQF takes user intent into account (it's also > >>> unclear to me how that's a low-power setting rather than a combination > >>> of the existing cool and quiet settings). > >> > >> AMD folks, please correct me if any of the below is wrong: > >> > >> AFAIK even though it is called CnQF it is more like auto-profile > >> selection and as such does not take user intent into account > >> at all. > >> > >> It looks at the workload over a somewhat longer time period (say > >> 5 minutes or so I guess?) and then if that consistently has been > >> quite high, it will select something similar to performance. > >> > >> Where as for a more mixed workload it will select balanced and for > >> a mostly idle machine it will select low-power. > >> > >> I guess this auto feature is best treated the same as unsupported hw. > >> > >>> (it's also > >>> unclear to me how that's a low-power setting rather than a combination > >>> of the existing cool and quiet settings). > >> > >> Even though it is called cool and quiet AFAIK it won't be all that > >> cool and quiet when running a heavy workload. Which is why I wonder > >> how to re-conciliate this with showing low-power in e.g. the > >> GNOME shell system men. Because in essence even if the battery > >> is low the system will still go full-throttle when confronted > >> with a heavy workload. > >> > >> So selecting low-power would result in the screen-dimming which > >> I think is part of that, but the CPU's max power-consumption won't > >> get limited as it would when platform-profiles are supported. > >> > >> So I guess this is indeed very much like how p-p-d behaves > >> on unsupported hw... > >> > >> ### > >> > >> As mentioned I guess one option would be for CnQF to > >> still register a platform_profile provider and then in > >> balanced mode do its CnQF thing and in low-power mode > >> disable CnQF and apply the static-slider low-power settings > >> I think that that would work best from things actual > >> working in a way I would expect the avarage end-user to > >> expect things to work. > >> > >> So p-p-d would then still see platform-profile support > >> in CnQF mode but with only low-power + balanced advertised. > >> > >> Bastien would that work for you? > > > > That's something I can make work, yes. > > > >> AMD folks would that also work for you ? > >> > >> ### > >> > >> I'm also wondering if we are going to still export > >> balanced + low-power modes to userspace in CnQF mode > >> and disable CnQF in low-power mode then if we > >> even need a sysfs knob to turn it on/off at all. > >> > >> I guess the sysfs knob would then still be useful > >> to turn it on on systems where it defaults to off > >> in the BIOS. Might be better to do this as > >> a kernel-cmdline (module-param) then though, then we > >> also avoid the problem of platform_profile support > >> all of a sudden changing underneath's p-p-d's feet. > > > > I would say that, you could probably have CnQF transparently replacing > > the more static "balanced" profile if it is available, and have a > > separate setting to force enable/disable it as a kernel command-line > > for debugging or if the BIOS menu doesn't offer it as an option. > > > > That way the balanced mode would work like a more refined automatic > > profile switcher, and make the default experience better, without the > > disappearing profiles, or the user-space API headaches. > > > > module param would be fine to force load CnQF if the BIOS does not > advertise it. > > But I still think, having a sysfs node would still help to give an > option to the user to "opt-out" of the scenarios where he thinks that > battery can drain out if CnQF is turned on? Or in any case to turn > on/off CnQF on the fly, so that he can still switch back to the > traditional "static slider" based power optimizations. > > Please let me know your thoughts on this? > > Thanks, > Shyam >
