1// Copyright 2019 The Prometheus Authors
2// Licensed under the Apache License, Version 2.0 (the "License");
3// you may not use this file except in compliance with the License.
4// You may obtain a copy of the License at
5//
6// http://www.apache.org/licenses/LICENSE-2.0
7//
8// Unless required by applicable law or agreed to in writing, software
9// distributed under the License is distributed on an "AS IS" BASIS,
10// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
11// See the License for the specific language governing permissions and
12// limitations under the License.
13
14package procfs
15
16// The PSI / pressure interface is described at
17//   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/accounting/psi.txt
18// Each resource (cpu, io, memory, ...) is exposed as a single file.
19// Each file may contain up to two lines, one for "some" pressure and one for "full" pressure.
20// Each line contains several averages (over n seconds) and a total in µs.
21//
22// Example io pressure file:
23// > some avg10=0.06 avg60=0.21 avg300=0.99 total=8537362
24// > full avg10=0.00 avg60=0.13 avg300=0.96 total=8183134
25
26import (
27	"bufio"
28	"bytes"
29	"fmt"
30	"io"
31	"strings"
32
33	"github.com/prometheus/procfs/internal/util"
34)
35
36const lineFormat = "avg10=%f avg60=%f avg300=%f total=%d"
37
38// PSILine is a single line of values as returned by /proc/pressure/*
39// The Avg entries are averages over n seconds, as a percentage
40// The Total line is in microseconds
41type PSILine struct {
42	Avg10  float64
43	Avg60  float64
44	Avg300 float64
45	Total  uint64
46}
47
48// PSIStats represent pressure stall information from /proc/pressure/*
49// Some indicates the share of time in which at least some tasks are stalled
50// Full indicates the share of time in which all non-idle tasks are stalled simultaneously
51type PSIStats struct {
52	Some *PSILine
53	Full *PSILine
54}
55
56// PSIStatsForResource reads pressure stall information for the specified
57// resource from /proc/pressure/<resource>. At time of writing this can be
58// either "cpu", "memory" or "io".
59func (fs FS) PSIStatsForResource(resource string) (PSIStats, error) {
60	data, err := util.ReadFileNoStat(fs.proc.Path(fmt.Sprintf("%s/%s", "pressure", resource)))
61	if err != nil {
62		return PSIStats{}, fmt.Errorf("psi_stats: unavailable for %q: %w", resource, err)
63	}
64
65	return parsePSIStats(resource, bytes.NewReader(data))
66}
67
68// parsePSIStats parses the specified file for pressure stall information
69func parsePSIStats(resource string, r io.Reader) (PSIStats, error) {
70	psiStats := PSIStats{}
71
72	scanner := bufio.NewScanner(r)
73	for scanner.Scan() {
74		l := scanner.Text()
75		prefix := strings.Split(l, " ")[0]
76		switch prefix {
77		case "some":
78			psi := PSILine{}
79			_, err := fmt.Sscanf(l, fmt.Sprintf("some %s", lineFormat), &psi.Avg10, &psi.Avg60, &psi.Avg300, &psi.Total)
80			if err != nil {
81				return PSIStats{}, err
82			}
83			psiStats.Some = &psi
84		case "full":
85			psi := PSILine{}
86			_, err := fmt.Sscanf(l, fmt.Sprintf("full %s", lineFormat), &psi.Avg10, &psi.Avg60, &psi.Avg300, &psi.Total)
87			if err != nil {
88				return PSIStats{}, err
89			}
90			psiStats.Full = &psi
91		default:
92			// If we encounter a line with an unknown prefix, ignore it and move on
93			// Should new measurement types be added in the future we'll simply ignore them instead
94			// of erroring on retrieval
95			continue
96		}
97	}
98
99	return psiStats, nil
100}
101