diff options
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/ABI/testing/sysfs-devices-system-cpu | 18 | ||||
| -rw-r--r-- | Documentation/admin-guide/pm/intel_epb.rst | 27 |
2 files changed, 45 insertions, 0 deletions
diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu index 9605dbd4b5b5..7f4af7da3fbc 100644 --- a/Documentation/ABI/testing/sysfs-devices-system-cpu +++ b/Documentation/ABI/testing/sysfs-devices-system-cpu @@ -518,3 +518,21 @@ Description: Control Symetric Multi Threading (SMT) If control status is "forceoff" or "notsupported" writes are rejected. + +What: /sys/devices/system/cpu/cpu#/power/energy_perf_bias +Date: March 2019 +Contact: linux-pm@vger.kernel.org +Description: Intel Energy and Performance Bias Hint (EPB) + + EPB for the given CPU in a sliding scale 0 - 15, where a value + of 0 corresponds to a hint preference for highest performance + and a value of 15 corresponds to the maximum energy savings. + + In order to change the EPB value for the CPU, write either + a number in the 0 - 15 sliding scale above, or one of the + strings: "performance", "balance-performance", "normal", + "balance-power", "power" (that represent values reflected by + their meaning), to this attribute. + + This attribute is present for all online CPUs supporting the + Intel EPB feature. diff --git a/Documentation/admin-guide/pm/intel_epb.rst b/Documentation/admin-guide/pm/intel_epb.rst index e9cfa7ec5420..d100849edfc4 100644 --- a/Documentation/admin-guide/pm/intel_epb.rst +++ b/Documentation/admin-guide/pm/intel_epb.rst @@ -4,3 +4,30 @@ Intel Performance and Energy Bias Hint .. kernel-doc:: arch/x86/kernel/cpu/intel_epb.c :doc: overview + +Intel Performance and Energy Bias Attribute in ``sysfs`` +======================================================== + +The Intel Performance and Energy Bias Hint (EPB) value for a given (logical) CPU +can be checked or updated through a ``sysfs`` attribute (file) under +:file:`/sys/devices/system/cpu/cpu<N>/power/`, where the CPU number ``<N>`` +is allocated at the system initialization time: + +``energy_perf_bias`` + Shows the current EPB value for the CPU in a sliding scale 0 - 15, where + a value of 0 corresponds to a hint preference for highest performance + and a value of 15 corresponds to the maximum energy savings. + + In order to update the EPB value for the CPU, this attribute can be + written to, either with a number in the 0 - 15 sliding scale above, or + with one of the strings: "performance", "balance-performance", "normal", + "balance-power", "power" that represent values reflected by their + meaning. + + This attribute is present for all online CPUs supporting the EPB + feature. + +Note that while the EPB interface to the processor is defined at the logical CPU +level, the physical register backing it may be shared by multiple CPUs (for +example, SMT siblings or cores in one package). For this reason, updating the +EPB value for one CPU may cause the EPB values for other CPUs to change. |