Based on AMD_ENERGY driver, but with some jiffies added so non-root users can read it safely.
Prefix: 'zenergy'
Addresses used: RAPL MSRs
Datasheets:
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Processor Programming Reference (PPR) for AMD Family 17h Model 01h, Revision B1 Processors
https://developer.amd.com/wp-content/resources/55570-B1_PUB.zip
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Preliminary Processor Programming Reference (PPR) for AMD Family 17h Model 31h, Revision B0 Processors
https://developer.amd.com/wp-content/resources/56176_ppr_Family_17h_Model_71h_B0_pub_Rev_3.06.zip
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Preliminary Processor Programming Reference (PPR) for AMD Family 19h Model 1h, Revision B1 Processors
Author: Naveen Krishna Chatradhi nchatrad@amd.com
The Energy driver exposes the energy counters that are reported via the Running Average Power Limit (RAPL) Model-specific Registers (MSRs) via the hardware monitor (HWMON) sysfs interface.
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Power, Energy and Time Units MSR_RAPL_POWER_UNIT/ C001_0299: shared with all cores in the socket
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Energy consumed by each Core MSR_CORE_ENERGY_STATUS/ C001_029A: 32-bitRO, Accumulator, core-level power reporting
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Energy consumed by Socket MSR_PACKAGE_ENERGY_STATUS/ C001_029B: 32-bitRO, Accumulator, socket-level power reporting, shared with all cores in socket
These registers are updated every 1ms and cleared on reset of the system.
Note: If SMT is enabled, Linux enumerates all threads as cpus. Since, the energy status registers are accessed at core level, reading those registers from the sibling threads would result in duplicate values. Hence, energy counter entries are not populated for the siblings.
Energy information (in Joules) is based on the multiplier, 1/2^ESU; where ESU is an unsigned integer read from MSR_RAPL_POWER_UNIT register. Default value is 10000b, indicating energy status unit is 15.3 micro-Joules increment.
Reported values are scaled as per the formula
scaled value = ((1/2^ESU) * (Raw value) * 1000000UL) in uJoules
Users calculate power for a given domain by calculating dEnergy/dTime for that domain.
Current, Socket energy status register is 32bit, assuming a 240W 2P system, the register would wrap around in
2^32*15.3 e-6/240 * 2 = 547.60833024 secs to wrap(~9 mins)
The Core energy register may wrap around after several days.
To improve the wrap around time, a kernel thread is implemented to accumulate the socket energy counters and one core energy counter per run to a respective 64-bit counter. The kernel thread starts running during probe, wakes up every 100secs and stops running when driver is removed.
Frequency of the accumulator thread is set during the probe based on the chosen energy unit resolution. For example A. fine grain (1.625 micro J) B. course grain (0.125 milli J)
A socket and core energy read would return the current register value added to the respective energy accumulator.
On newer EPYC CPUs with 64bit RAPL energy MSRs, software accumulation of energy counters is not required. Hence, accumulation is enabled only on select EPYC CPUs with 32bit RAPL MSRs.
| Attribute | Label | Description |
|---|---|---|
| energy[X]_input | Ecore[X] energy | X = [0] to [nr_cpus - 1] Measured input core energy |
| energy[X]_input | Esocket[X] energy | X = [nr_cpus] to [nr_socks - 1] Measured input socket energy |
Kernel development packages for the running kernel need to be installed prior to building the Energy module. A Makefile is provided which should work with most kernel source trees.
To build the kernel module:
#> make
To install the kernel module:
#> sudo make modules_install
To clean the kernel module build directory:
#> make clean
If the Energy module was installed you should use the modprobe command to load the module.
#> sudo modprobe zenergy
The Energy module can also be loaded using insmod if the module was not installed:
#> sudo insmod ./zenergy.ko
Building Module with running version of kernel
Add the module to DKMS tree:
#> sudo dkms add ../zenergy
Build the module using DKMS:
#> sudo dkms build -m zenergy/1.0
Install the module using DKMS:
#> sudo dkms install --force zenergy/1.0
Load the module:
#> sudo modprobe zenergy
Building Module with specific version of kernel
Add the module to DKMS tree:
#> sudo dkms add ../zenergy
Build the module using DKMS:
#> sudo dkms build zenergy/1.0 -k linux_version
Install the module using DKMS:
#> sudo dkms install --force zenergy/1.0 -k linux_version
Module is built: /lib/modules/linux_version/updates/dkms/
Notes: It is required to have specific linux verion header in /usr/src
To remove module from dkms tree
#> sudo dkms remove -m zenergy/1.0 --all
#> sudo rm -rf /usr/src/zenergy-1.0/