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
