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Diffstat (limited to 'Documentation/admin-guide/thermal')
| -rw-r--r-- | Documentation/admin-guide/thermal/index.rst | 1 | ||||
| -rw-r--r-- | Documentation/admin-guide/thermal/intel_thermal_throttle.rst | 91 |
2 files changed, 92 insertions, 0 deletions
diff --git a/Documentation/admin-guide/thermal/index.rst b/Documentation/admin-guide/thermal/index.rst index 193b7b01a87d..e48bc0a1951b 100644 --- a/Documentation/admin-guide/thermal/index.rst +++ b/Documentation/admin-guide/thermal/index.rst @@ -6,3 +6,4 @@ Thermal Subsystem :maxdepth: 1 intel_powerclamp + intel_thermal_throttle diff --git a/Documentation/admin-guide/thermal/intel_thermal_throttle.rst b/Documentation/admin-guide/thermal/intel_thermal_throttle.rst new file mode 100644 index 000000000000..f4fbf9d5a4ec --- /dev/null +++ b/Documentation/admin-guide/thermal/intel_thermal_throttle.rst @@ -0,0 +1,91 @@ +.. SPDX-License-Identifier: GPL-2.0 +.. include:: <isonum.txt> + +======================================= +Intel thermal throttle events reporting +======================================= + +:Author: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> + +Introduction +------------ + +Intel processors have built in automatic and adaptive thermal monitoring +mechanisms that force the processor to reduce its power consumption in order +to operate within predetermined temperature limits. + +Refer to section "THERMAL MONITORING AND PROTECTION" in the "Intel® 64 and +IA-32 Architectures Software Developer’s Manual Volume 3 (3A, 3B, 3C, & 3D): +System Programming Guide" for more details. + +In general, there are two mechanisms to control the core temperature of the +processor. They are called "Thermal Monitor 1 (TM1) and Thermal Monitor 2 (TM2)". + +The status of the temperature sensor that triggers the thermal monitor (TM1/TM2) +is indicated through the "thermal status flag" and "thermal status log flag" in +MSR_IA32_THERM_STATUS for core level and MSR_IA32_PACKAGE_THERM_STATUS for +package level. + +Thermal Status flag, bit 0 — When set, indicates that the processor core +temperature is currently at the trip temperature of the thermal monitor and that +the processor power consumption is being reduced via either TM1 or TM2, depending +on which is enabled. When clear, the flag indicates that the core temperature is +below the thermal monitor trip temperature. This flag is read only. + +Thermal Status Log flag, bit 1 — When set, indicates that the thermal sensor has +tripped since the last power-up or reset or since the last time that software +cleared this flag. This flag is a sticky bit; once set it remains set until +cleared by software or until a power-up or reset of the processor. The default +state is clear. + +It is possible that when user reads MSR_IA32_THERM_STATUS or +MSR_IA32_PACKAGE_THERM_STATUS, TM1/TM2 is not active. In this case, +"Thermal Status flag" will read "0" and the "Thermal Status Log flag" will be set +to show any previous "TM1/TM2" activation. But since it needs to be cleared by +the software, it can't show the number of occurrences of "TM1/TM2" activations. + +Hence, Linux provides counters of how many times the "Thermal Status flag" was +set. Also presents how long the "Thermal Status flag" was active in milliseconds. +Using these counters, users can check if the performance was limited because of +thermal events. It is recommended to read from sysfs instead of directly reading +MSRs as the "Thermal Status Log flag" is reset by the driver to implement rate +control. + +Sysfs Interface +--------------- + +Thermal throttling events are presented for each CPU under +"/sys/devices/system/cpu/cpuX/thermal_throttle/", where "X" is the CPU number. + +All these counters are read-only. They can't be reset to 0. So, they can potentially +overflow after reaching the maximum 64 bit unsigned integer. + +``core_throttle_count`` + Shows the number of times "Thermal Status flag" changed from 0 to 1 for this + CPU since OS boot and thermal vector is initialized. This is a 64 bit counter. + +``package_throttle_count`` + Shows the number of times "Thermal Status flag" changed from 0 to 1 for the + package containing this CPU since OS boot and thermal vector is initialized. + Package status is broadcast to all CPUs; all CPUs in the package increment + this count. This is a 64-bit counter. + +``core_throttle_max_time_ms`` + Shows the maximum amount of time for which "Thermal Status flag" has been + set to 1 for this CPU at the core level since OS boot and thermal vector + is initialized. + +``package_throttle_max_time_ms`` + Shows the maximum amount of time for which "Thermal Status flag" has been + set to 1 for the package containing this CPU since OS boot and thermal + vector is initialized. + +``core_throttle_total_time_ms`` + Shows the cumulative time for which "Thermal Status flag" has been + set to 1 for this CPU for core level since OS boot and thermal vector + is initialized. + +``package_throttle_total_time_ms`` + Shows the cumulative time for which "Thermal Status flag" has been set + to 1 for the package containing this CPU since OS boot and thermal vector + is initialized. |