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// 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 %s", resource)
}
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
}
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