Source: proc_psi.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

The PSI / pressure interface is described at https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/accounting/psi.txt Each resource (cpu, io, memory, ...) is exposed as a single file. Each file may contain up to two lines, one for "some" pressure and one for "full" pressure. Each line contains several averages (over n seconds) and a total in µs. Example io pressure file: > some avg10=0.06 avg60=0.21 avg300=0.99 total=8537362 > full avg10=0.00 avg60=0.13 avg300=0.96 total=8183134


import (
	"bufio"
	"bytes"
	"fmt"
	"io"
	"strings"

	"github.com/prometheus/procfs/internal/util"
)

const lineFormat = "avg10=%f avg60=%f avg300=%f total=%d"

PSILine is a single line of values as returned by /proc/pressure The Avg entries are averages over n seconds, as a percentage The Total line is in microseconds

type PSILine struct {
	Avg10  float64
	Avg60  float64
	Avg300 float64
	Total  uint64
}

PSIStats represent pressure stall information from /proc/pressure Some indicates the share of time in which at least some tasks are stalled Full indicates the share of time in which all non-idle tasks are stalled simultaneously

type PSIStats struct {
	Some *PSILine
	Full *PSILine
}

PSIStatsForResource reads pressure stall information for the specified resource from /proc/pressure/<resource>. At time of writing this can be either "cpu", "memory" or "io".

func (fs FS) PSIStatsForResource(resource string) (PSIStats, error) {
	data, err := util.ReadFileNoStat(fs.proc.Path(fmt.Sprintf("%s/%s", "pressure", resource)))
	if err != nil {
		return PSIStats{}, fmt.Errorf("psi_stats: unavailable for %s", resource)
	}

	return parsePSIStats(resource, bytes.NewReader(data))
}

parsePSIStats parses the specified file for pressure stall information

func parsePSIStats(resource string, r io.Reader) (PSIStats, error) {
	psiStats := PSIStats{}

	scanner := bufio.NewScanner(r)
	for scanner.Scan() {
		l := scanner.Text()
		prefix := strings.Split(l, " ")[0]
		switch prefix {
		case "some":
			psi := PSILine{}
			_, err := fmt.Sscanf(l, fmt.Sprintf("some %s", lineFormat), &psi.Avg10, &psi.Avg60, &psi.Avg300, &psi.Total)
			if err != nil {
				return PSIStats{}, err
			}
			psiStats.Some = &psi
		case "full":
			psi := PSILine{}
			_, err := fmt.Sscanf(l, fmt.Sprintf("full %s", lineFormat), &psi.Avg10, &psi.Avg60, &psi.Avg300, &psi.Total)
			if err != nil {
				return PSIStats{}, err
			}
			psiStats.Full = &psi

If we encounter a line with an unknown prefix, ignore it and move on Should new measurement types be added in the future we'll simply ignore them instead of erroring on retrieval

			continue
		}
	}

	return psiStats, nil