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probe.go
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probe.go
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package scheduler
import (
"bufio"
"fmt"
"os"
"strings"
"time"
)
var (
loadavgFilename = "/proc/loadavg"
statFilename = "/proc/stat"
)
func (p *prober) probe() error {
if err := p.probeLoadavg(); err != nil {
return err
}
if err := p.probeCpu(); err != nil {
return err
}
return nil
}
func (p *prober) probeLoadavg() error {
file, err := os.Open(loadavgFilename)
if err != nil {
return err
}
defer file.Close()
var str string
nScanned, err := fmt.Fscanf(file, "%f %f %f %s",
&p.loadavg.oneMinute, &p.loadavg.fiveMinutes, &p.loadavg.fifteenMinutes,
&str)
if err != nil {
return err
}
if nScanned < 3 {
return fmt.Errorf("only read %d values from %s",
nScanned, loadavgFilename)
}
return nil
}
func (p *prober) probeCpu() error {
file, err := os.Open(statFilename)
if err != nil {
return err
}
defer file.Close()
scanner := bufio.NewScanner(file)
currentTime := time.Now()
lastCpuStats := p.cpuStats
for scanner.Scan() {
if err := p.processStatLine(scanner.Text()); err != nil {
return err
}
}
if err := scanner.Err(); err != nil {
return err
}
if !p.cpuStats.lastProbeTime.IsZero() {
interval := float64(currentTime.Sub(p.cpuStats.lastProbeTime))
p.cpuStats.idleTime.fraction = float64(p.cpuStats.idleTime.value-
lastCpuStats.idleTime.value) / interval
p.cpuStats.iOWaitTime.fraction = float64(p.cpuStats.iOWaitTime.value-
lastCpuStats.iOWaitTime.value) / interval
p.cpuStats.irqTime.fraction = float64(p.cpuStats.irqTime.value-
lastCpuStats.irqTime.value) / interval
p.cpuStats.userNiceTime.fraction = float64(
p.cpuStats.userNiceTime.value-lastCpuStats.userNiceTime.value) /
interval
p.cpuStats.softIrqTime.fraction = float64(p.cpuStats.softIrqTime.value-
lastCpuStats.softIrqTime.value) / interval
p.cpuStats.systemTime.fraction = float64(p.cpuStats.systemTime.value-
lastCpuStats.systemTime.value) / interval
p.cpuStats.userTime.fraction = float64(p.cpuStats.userTime.value-
lastCpuStats.userTime.value) / interval
}
p.cpuStats.lastProbeTime = currentTime
return nil
}
func (p *prober) processStatLine(line string) error {
if strings.HasPrefix(line, "cpu ") {
var user, niced, sys, idle, iowait, irq, softIrq int64
nScanned, err := fmt.Sscanf(line[4:], "%d %d %d %d %d %d %d",
&user, &niced, &sys, &idle, &iowait, &irq, &softIrq)
if err != nil {
return err
}
if nScanned < 7 {
return fmt.Errorf("only read %d values from %s",
nScanned, statFilename)
}
p.cpuStats.idleTime.value = p.tickToDuration(idle)
p.cpuStats.iOWaitTime.value = p.tickToDuration(iowait)
p.cpuStats.irqTime.value = p.tickToDuration(irq)
p.cpuStats.userNiceTime.value = p.tickToDuration(niced)
p.cpuStats.softIrqTime.value = p.tickToDuration(softIrq)
p.cpuStats.systemTime.value = p.tickToDuration(sys)
p.cpuStats.userTime.value = p.tickToDuration(user)
}
return nil
}
func (p *prober) tickToDuration(tick int64) time.Duration {
// TODO(rgooch): Use sysconf(_SC_CLK_TCK).
tickToDuration := time.Millisecond * 10 / time.Duration(p.numCpus)
return time.Duration(tick) * tickToDuration
}