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 "fmt" 28 "io" 29 "io/ioutil" 30 "os" 31 "strings" 32) 33 34const lineFormat = "avg10=%f avg60=%f avg300=%f total=%d" 35 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 39type PSILine struct { 40 Avg10 float64 41 Avg60 float64 42 Avg300 float64 43 Total uint64 44} 45 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 49type PSIStats struct { 50 Some *PSILine 51 Full *PSILine 52} 53 54// PSIStatsForResource reads pressure stall information for the specified 55// resource from /proc/pressure/<resource>. At time of writing this can be 56// either "cpu", "memory" or "io". 57func (fs FS) PSIStatsForResource(resource string) (PSIStats, error) { 58 file, err := os.Open(fs.proc.Path(fmt.Sprintf("%s/%s", "pressure", resource))) 59 if err != nil { 60 return PSIStats{}, fmt.Errorf("psi_stats: unavailable for %s", resource) 61 } 62 63 defer file.Close() 64 return parsePSIStats(resource, file) 65} 66 67// parsePSIStats parses the specified file for pressure stall information 68func parsePSIStats(resource string, file io.Reader) (PSIStats, error) { 69 psiStats := PSIStats{} 70 stats, err := ioutil.ReadAll(file) 71 if err != nil { 72 return psiStats, fmt.Errorf("psi_stats: unable to read data for %s", resource) 73 } 74 75 for _, l := range strings.Split(string(stats), "\n") { 76 prefix := strings.Split(l, " ")[0] 77 switch prefix { 78 case "some": 79 psi := PSILine{} 80 _, err := fmt.Sscanf(l, fmt.Sprintf("some %s", lineFormat), &psi.Avg10, &psi.Avg60, &psi.Avg300, &psi.Total) 81 if err != nil { 82 return PSIStats{}, err 83 } 84 psiStats.Some = &psi 85 case "full": 86 psi := PSILine{} 87 _, err := fmt.Sscanf(l, fmt.Sprintf("full %s", lineFormat), &psi.Avg10, &psi.Avg60, &psi.Avg300, &psi.Total) 88 if err != nil { 89 return PSIStats{}, err 90 } 91 psiStats.Full = &psi 92 default: 93 // If we encounter a line with an unknown prefix, ignore it and move on 94 // Should new measurement types be added in the future we'll simply ignore them instead 95 // of erroring on retrieval 96 continue 97 } 98 } 99 100 return psiStats, nil 101} 102