On modern systems CPU/GPU/... performance is often dynamically configurable in the form of e.g. variable clock-speeds and TPD. The performance is often automatically adjusted to the load by some automatic-mechanism (which may very well live outside the kernel). These auto performance-adjustment mechanisms often can be configured with one of several performance-profiles, with either a bias towards low-power consumption (and cool and quiet) or towards performance (and higher power consumption and thermals). Introduce a new performance_profile class/sysfs API which offers a generic API for selecting the performance-profile of these automatic-mechanisms. Cc: Mark Pearson <markpearson@xxxxxxxxxx> Cc: Elia Devito <eliadevito@xxxxxxxxx> Cc: Bastien Nocera <hadess@xxxxxxxxxx> Cc: Benjamin Berg <bberg@xxxxxxxxxx> Cc: linux-pm@xxxxxxxxxxxxxxx Cc: linux-acpi@xxxxxxxxxxxxxxx Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx> --- .../testing/sysfs-class-performance_profile | 104 ++++++++++++++++++ 1 file changed, 104 insertions(+) create mode 100644 Documentation/ABI/testing/sysfs-class-performance_profile diff --git a/Documentation/ABI/testing/sysfs-class-performance_profile b/Documentation/ABI/testing/sysfs-class-performance_profile new file mode 100644 index 000000000000..9c67cae39600 --- /dev/null +++ b/Documentation/ABI/testing/sysfs-class-performance_profile @@ -0,0 +1,104 @@ +Performance-profile selection (e.g. /sys/class/performance_profile/thinkpad_acpi/) + +On modern systems CPU/GPU/... performance is often dynamically configurable +in the form of e.g. variable clock-speeds and TPD. The performance is often +automatically adjusted to the load by some automatic-mechanism (which may +very well live outside the kernel). + +These auto performance-adjustment mechanisms often can be configured with +one of several performance-profiles, with either a bias towards low-power +consumption (and cool and quiet) or towards performance (and higher power +consumption and thermals). + +The purpose of the performance_profile class is to offer a generic sysfs +API for selecting the performance-profile of these automatic-mechanisms. + +Note that this API is only for selecting the performance-profile, it is +NOT a goal of this API to allow monitoring the resulting performance +characteristics. Monitoring performance is best done with device/vendor +specific tools such as e.g. turbostat. + +Specifically when selecting a high-performance profile the actual achieved +performance may be limited by various factors such as: the heat generated by +other components, room temperature, free air flow at the bottom of a laptop, +etc. It is explicitly NOT a goal of this API to let userspace know about +any sub-optimal conditions which are impeding reaching the requested +performance level. + +Since numbers are a rather meaningless way to describe performance-profiles +this API uses strings to describe the various profiles. To make sure that +userspace gets a consistent experience when using this API this API document +defines a fixed set of profile-names. Drivers *must* map their internal +profile representation/names onto this fixed set. + +If for some reason there is no good match when mapping then a new profile-name +may be added. Drivers which wish to introduce new profile-names must: +1. Have very good reasons to do so. +2. Add the new profile-name to this document, so that future drivers which also + have a similar problem can use the same new. Usually new profile-names will + be added to the "extra profile-names" section of this document. But in some + cases the set of standard profile-names may be extended. + +What: /sys/class/performance_profile/<device>/available_profiles +Date: October 2020 +Contact: Hans de Goede <hdegoede@xxxxxxxxxx> +Description: + Reading this file gives a space separated list of profiles + supported for this device. + + Drivers must use the following standard profile-names whenever + possible: + + low-power: Emphasises low power consumption + (and also cool and quiet) + balanced-low-power: Balances between low power consumption + and performance with a slight bias + towards low power + balanced: Balance between low power consumption + and performance + balanced-performance: Balances between performance and low + power consumption with a slight bias + towards performance + performance: Emphasises performance (and may lead to + higher temperatures and fan speeds) + + Userspace may expect drivers to offer at least several of these + standard profile-names! If none of the above are a good match + for some of the drivers profiles, then drivers may use one of + these extra profile-names: + <reserved for future use> + +What: /sys/class/performance_profile/<device>/current_profile +Date: October 2020 +Contact: Hans de Goede <hdegoede@xxxxxxxxxx> +Description: + Reading this file gives the current selected profile for this + device. Writing this file with one of the strings from + available_profiles changes the profile to the new value. + + Reading this file may also return "custom". This is intended for + drivers which have and export multiple knobs influencing + performance. Such drivers may very well still want to offer a + set of profiles for easy of use and to be able to offer a + consistent standard API (this API) to userspace for configuring + their performance. The "custom" value is intended for when a + user has directly configured the knobs (through e.g. some + advanced control-panel for a GPU) and the knob values do not + match any of the presets represented by the + performance-profiles. In this case writing this file will + override the modifications and restore the selected presets. + +What: /sys/class/performance_profile/<device>/type +Date: October 2020 +Contact: Hans de Goede <hdegoede@xxxxxxxxxx> +Description: + Performance-profiles may be system-wide, or for a specific + device (e.g. CPU / GPU). System-wide profiles are typically + used on devices where where a single cooling solution is + shared between all components, such as laptops and NUCs. + + Reading this file indicates the type of the device for which + the thermal-profile is being configured. + + Valid values: "system" + Reserved for future use values: "cpu", "gpu" -- 2.28.0
