source: code/trunk/vendor/github.com/prometheus/procfs/proc_psi.go@ 822

// 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 %q: %w", resource, err)
        }

        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
                default:
                        // 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
}