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
6 // http://www.apache.org/licenses/LICENSE-2.0
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.
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.
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
34 const lineFormat = "avg10=%f avg60=%f avg300=%f total=%d"
36 // PSILine is a single line of values as returned by /proc/pressure/*
37 // The Avg entries are averages over n seconds, as a percentage
38 // The Total line is in microseconds
46 // PSIStats represent pressure stall information from /proc/pressure/*
47 // Some indicates the share of time in which at least some tasks are stalled
48 // Full indicates the share of time in which all non-idle tasks are stalled simultaneously
49 type PSIStats struct {
54 // NewPSIStatsForResource reads pressure stall information for the specified
55 // resource. At time of writing this can be either "cpu", "memory" or "io".
56 func NewPSIStatsForResource(resource string) (PSIStats, error) {
57 fs, err := NewFS(DefaultMountPoint)
59 return PSIStats{}, err
62 return fs.NewPSIStatsForResource(resource)
65 // NewPSIStatsForResource reads pressure stall information from /proc/pressure/<resource>
66 func (fs FS) NewPSIStatsForResource(resource string) (PSIStats, error) {
67 file, err := os.Open(fs.Path(fmt.Sprintf("%s/%s", "pressure", resource)))
69 return PSIStats{}, fmt.Errorf("psi_stats: unavailable for %s", resource)
73 return parsePSIStats(resource, file)
76 // parsePSIStats parses the specified file for pressure stall information
77 func parsePSIStats(resource string, file io.Reader) (PSIStats, error) {
78 psiStats := PSIStats{}
79 stats, err := ioutil.ReadAll(file)
81 return psiStats, fmt.Errorf("psi_stats: unable to read data for %s", resource)
84 for _, l := range strings.Split(string(stats), "\n") {
85 prefix := strings.Split(l, " ")[0]
89 _, err := fmt.Sscanf(l, fmt.Sprintf("some %s", lineFormat), &psi.Avg10, &psi.Avg60, &psi.Avg300, &psi.Total)
91 return PSIStats{}, err
96 _, err := fmt.Sscanf(l, fmt.Sprintf("full %s", lineFormat), &psi.Avg10, &psi.Avg60, &psi.Avg300, &psi.Total)
98 return PSIStats{}, err
102 // If we encounter a line with an unknown prefix, ignore it and move on
103 // Should new measurement types be added in the future we'll simply ignore them instead
104 // of erroring on retrieval