The project provides the CPUFreq Swift package - a thin wrapper around the CPUFreq Linux interface in sysfs for getting and setting DVFS-related configurations.
Its purpose is to abstract programs from file I/O and data parsing/conversion.
It does not provide core/domain/socket discovery or DVFS management logic.
For Linux kernel documentation on CPUFreq, see: https://www.kernel.org/doc/Documentation/cpu-freq/user-guide.txt
To build, run:
swift build
A simple example of setting DVFS frequencies with the userspace governor:
import CPUFreq // in practice, core IDs could be discovered dynamically using other means... let bindings: [CPUFreq] = [ CPUFreq(cpu: 0), CPUFreq(cpu: 1) ] // populate "availableFreqs" array let availableFreqs: [UInt32] = bindings[0].getScalingAvailableFrequencies()! // won't use that file again, so we can manually close it to free up resources bindings[0].closeFile(file: CPUFreqFile.scalingAvailableFrequencies) // set "userspace" governor on all cores for cpu in bindings { let _ = cpu.setScalingGovernor(governor: "userspace") // again, close the file manually to free up resources cpu.closeFile(file: CPUFreqFile.scalingGovernor) } // do application work, breaking from loop when finished... while (true) { // in practice, a new frequency would be determined dynamically by some scheduling logic... let freq = availableFreqs[0]; for cpu in bindings { let _ = cpu.setScalingSetspeed(freq: freq); } } // once bindings go out of scope, any open files (e.g. CPUFreqFile.scalingSetspeed) are closed automatically
The files scaling_governor, scaling_min_freq, and scaling_max_freq are opened as read/write by default, but may be opened as read-only by specifying readOnly: True as a function parameter when they are first accessed.
The file scaling_setspeed is opened as write-only.
All other files are opened as read-only.
Users are responsible for ensuring that their programs have correct read/write privileges.
Find this and related project sources at the powercap organization on GitHub.
This project originates at: https://github.com/powercap/CPUFreq-Swift
Bug reports and pull requests are welcome.