cubefs

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// Copyright 2019 The Prometheus Authors
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package procfs
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// The PSI / pressure interface is described at
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//   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/accounting/psi.txt
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// Each resource (cpu, io, memory, ...) is exposed as a single file.
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// Each file may contain up to two lines, one for "some" pressure and one for "full" pressure.
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// Each line contains several averages (over n seconds) and a total in µs.
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//
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// Example io pressure file:
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// > some avg10=0.06 avg60=0.21 avg300=0.99 total=8537362
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// > full avg10=0.00 avg60=0.13 avg300=0.96 total=8183134
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import (
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	"bufio"
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	"bytes"
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	"fmt"
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	"io"
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	"strings"
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	"github.com/prometheus/procfs/internal/util"
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)
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const lineFormat = "avg10=%f avg60=%f avg300=%f total=%d"
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// PSILine is a single line of values as returned by `/proc/pressure/*`.
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//
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// The Avg entries are averages over n seconds, as a percentage.
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// The Total line is in microseconds.
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type PSILine struct {
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	Avg10  float64
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	Avg60  float64
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	Avg300 float64
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	Total  uint64
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}
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// PSIStats represent pressure stall information from /proc/pressure/*
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//
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// "Some" indicates the share of time in which at least some tasks are stalled.
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// "Full" indicates the share of time in which all non-idle tasks are stalled simultaneously.
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type PSIStats struct {
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	Some *PSILine
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	Full *PSILine
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}
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// PSIStatsForResource reads pressure stall information for the specified
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// resource from /proc/pressure/<resource>. At time of writing this can be
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// either "cpu", "memory" or "io".
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func (fs FS) PSIStatsForResource(resource string) (PSIStats, error) {
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	data, err := util.ReadFileNoStat(fs.proc.Path(fmt.Sprintf("%s/%s", "pressure", resource)))
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	if err != nil {
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		return PSIStats{}, fmt.Errorf("psi_stats: unavailable for %q: %w", resource, err)
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	}
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	return parsePSIStats(resource, bytes.NewReader(data))
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}
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// parsePSIStats parses the specified file for pressure stall information.
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func parsePSIStats(resource string, r io.Reader) (PSIStats, error) {
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	psiStats := PSIStats{}
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	scanner := bufio.NewScanner(r)
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	for scanner.Scan() {
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		l := scanner.Text()
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		prefix := strings.Split(l, " ")[0]
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		switch prefix {
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		case "some":
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			psi := PSILine{}
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			_, err := fmt.Sscanf(l, fmt.Sprintf("some %s", lineFormat), &psi.Avg10, &psi.Avg60, &psi.Avg300, &psi.Total)
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			if err != nil {
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				return PSIStats{}, err
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			}
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			psiStats.Some = &psi
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		case "full":
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			psi := PSILine{}
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			_, err := fmt.Sscanf(l, fmt.Sprintf("full %s", lineFormat), &psi.Avg10, &psi.Avg60, &psi.Avg300, &psi.Total)
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			if err != nil {
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				return PSIStats{}, err
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			}
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			psiStats.Full = &psi
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		default:
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			// If we encounter a line with an unknown prefix, ignore it and move on
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			// Should new measurement types be added in the future we'll simply ignore them instead
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			// of erroring on retrieval
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			continue
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		}
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	}
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	return psiStats, nil
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}
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