Hi Bastien, On 9/7/22 16:24, Bastien Nocera wrote: > 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? Let me try clarify things: CnQF has 4 levels internally, between which it switches automatically based on the workload of the last 5 minutes. So from a userspace pov CnQF is a single setting which can be toggled on / off. Basically it is a more dynamic balanced mode, so I think it makes sense for the amd-pmf code to always export a platform_profile interface and when CnQF is on then use CnQF for balanced and the static slider settings for low-power / performance. And when CnQF is off, then just use what AMD calls the static slider balanced setting. This way for performance-profile-daemon nothing really changes. This can then be combined with allowing the user to turn CnQF on/off through sysfs as an extra option which p-p-d can ignore (this sysfs file then choses between CnQF and static balanced mode when balance is set through the platform interface). Regards, Hans p.s. Shyam I will reply to your emails in a couple of minutes. > > 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 >> >
