cpu-usage

cpu-usage (cpu_usage.h) is a tiny public domain library that reads CPU usage per core on Linux. It also measures RAPL package energy (joules and watts), estimates per-process energy, and converts it to CO2e emissions.

The library is self-documented: read cpu_usage.h.

Usage

Everything works with snapshots ("slices"): take one, run something, take another, and compute the difference.

Function	Description
`get_cpu_usage(id, &slice)`	Snapshot a core (or the whole machine)
`calc_cpu_usage(t0, t1)`	Usage % between two snapshots
`get_proc_cpu_usage(pid, &slice)`	Snapshot a process (`pid <= 0` is self)
`get_thread_cpu_usage(pid, tid, &slice)`	Snapshot a thread
`calc_proc_cpu_usage(...)`	Process usage % against the machine
`calc_proc_cpu_usage_per_core(...)`	top-style %, one core = 100%
`get_cpu_count()`	Cores the process may run on
`get_energy_open(&h)`, `close_energy(&h)`	Open/close the RAPL counter
`get_energy_usage(&h, &slice)`	Snapshot package energy
`calc_energy_joules(t0, t1)`, `calc_energy_power(t0, t1)`	Energy and average power
`calc_proc_energy_joules(...)`	Estimated energy of one process
`calc_carbon_emissions(t0, t1, g_per_kwh)`	Grams of CO2e

The *_children variants include waited-for children.

Note The energy counters come from RAPL through the perf power PMU and need root or CAP_PERFMON. RAPL measures the first socket only, and per-process energy is an estimate: package joules times the process's share of CPU time. Run the test with sudo for the energy part.

Usage

See also