Source: schedstat.go in package github.com/prometheus/procfs

Copyright 2019 The Prometheus Authors Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.


package procfs

import (
	"bufio"
	"errors"
	"os"
	"regexp"
	"strconv"
)

var (
	cpuLineRE  = regexp.MustCompile(`cpu(\d+) (\d+) (\d+) (\d+) (\d+) (\d+) (\d+) (\d+) (\d+) (\d+)`)
	procLineRE = regexp.MustCompile(`(\d+) (\d+) (\d+)`)
)

Schedstat contains scheduler statistics from /proc/schedstat See https://www.kernel.org/doc/Documentation/scheduler/sched-stats.txt for a detailed description of what these numbers mean. Note the current kernel documentation claims some of the time units are in jiffies when they are actually in nanoseconds since 2.6.23 with the introduction of CFS. A fix to the documentation is pending. See https://lore.kernel.org/patchwork/project/lkml/list/?series=403473

type Schedstat struct {
	CPUs []*SchedstatCPU
}

SchedstatCPU contains the values from one "cpu<N>" line

type SchedstatCPU struct {
	CPUNum string

	RunningNanoseconds uint64
	WaitingNanoseconds uint64
	RunTimeslices      uint64
}

ProcSchedstat contains the values from /proc/<pid>/schedstat

type ProcSchedstat struct {
	RunningNanoseconds uint64
	WaitingNanoseconds uint64
	RunTimeslices      uint64
}

Schedstat reads data from /proc/schedstat

func (fs FS) Schedstat() (*Schedstat, error) {
	file, err := os.Open(fs.proc.Path("schedstat"))
	if err != nil {
		return nil, err
	}
	defer file.Close()

	stats := &Schedstat{}
	scanner := bufio.NewScanner(file)

	for scanner.Scan() {
		match := cpuLineRE.FindStringSubmatch(scanner.Text())
		if match != nil {
			cpu := &SchedstatCPU{}
			cpu.CPUNum = match[1]

			cpu.RunningNanoseconds, err = strconv.ParseUint(match[8], 10, 64)
			if err != nil {
				continue
			}

			cpu.WaitingNanoseconds, err = strconv.ParseUint(match[9], 10, 64)
			if err != nil {
				continue
			}

			cpu.RunTimeslices, err = strconv.ParseUint(match[10], 10, 64)
			if err != nil {
				continue
			}

			stats.CPUs = append(stats.CPUs, cpu)
		}
	}

	return stats, nil
}

func parseProcSchedstat(contents string) (stats ProcSchedstat, err error) {
	match := procLineRE.FindStringSubmatch(contents)

	if match != nil {
		stats.RunningNanoseconds, err = strconv.ParseUint(match[1], 10, 64)
		if err != nil {
			return
		}

		stats.WaitingNanoseconds, err = strconv.ParseUint(match[2], 10, 64)
		if err != nil {
			return
		}

		stats.RunTimeslices, err = strconv.ParseUint(match[3], 10, 64)
		return
	}

	err = errors.New("could not parse schedstat")
	return