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