perf.go

package nospike

import (
	"bufio"
	"errors"
	"fmt"
	"io/ioutil"
	"log"
	"os"
	"path/filepath"
	"strconv"
	"syscall"

	"golang.org/x/sys/unix"
)

type Nospike interface {
	AddSelf()
	SetCpuLimit(cpuPercentage float64)
	GetThrottleDelta() uint64
	Dispose()
}

type nospikeInstance struct {
	mountdir      string
	cgId          string
	nrPeriods     uint64
	nrThrottled   uint64
	throttledTime uint64
}

const resolution float64 = 20000

func (c *nospikeInstance) AddSelf() {
	err := ioutil.WriteFile(filepath.Join(c.mountdir, c.cgId, "cgroup.procs"), []byte("0"), 0)
	if err != nil {
		panic(err)
	}
}

func (c *nospikeInstance) SetCpuLimit(cpuPercentage float64) {
	quota := resolution * cpuPercentage / 100
	err := ioutil.WriteFile(filepath.Join(c.mountdir, c.cgId, "cpu.cfs_quota_us"), []byte(strconv.FormatFloat(quota, 'f', 0, 64)), 0)
	if err != nil {
		panic(err)
	}
	err = ioutil.WriteFile(filepath.Join(c.mountdir, c.cgId, "cpu.cfs_period_us"), []byte(strconv.FormatFloat(resolution, 'f', 0, 64)), 0)
	if err != nil {
		panic(err)
	}
}

func (c *nospikeInstance) Dispose() {
	unix.Unmount(c.mountdir, unix.UMOUNT_NOFOLLOW|unix.MNT_FORCE)
	os.Remove(c.mountdir)
}

func (c *nospikeInstance) GetThrottleDelta() uint64 {
	var nrPeriodsOld uint64 = c.nrPeriods
	var nrThrottledOld uint64 = c.nrThrottled
	var throttledTimeOld uint64 = c.throttledTime

	f, err := os.Open(filepath.Join(c.mountdir, c.cgId, "cpu.stat"))
	if err != nil {
		log.Fatal(err)
	}
	defer f.Close()

	scanner := bufio.NewScanner(f)
	for scanner.Scan() {
		var key string
		var val uint64
		cnt, err := fmt.Sscanf(scanner.Text(), "%s %d", &key, &val)
		if err != nil || cnt != 2 {
			continue
		}
		switch key {
		case "nr_periods":
			c.nrPeriods = val
		case "nr_throttled":
			c.nrThrottled = val
		case "throttled_time":
			c.throttledTime = val
		}
	}
	if nrThrottledOld == 0 {
		return 0
	}
	//fmt.Println("time:", c.throttledTime, c.nrThrottled, c.nrPeriods)
	delta := c.throttledTime - throttledTimeOld
	deltap := c.nrPeriods - nrPeriodsOld
	deltat := c.nrThrottled - nrThrottledOld

	_ = delta
	_ = deltap

	return deltat
}

func New(cgId string) (Nospike, error) {
	inst := &nospikeInstance{
		cgId: cgId,
	}
	tmpdir, err := ioutil.TempDir("", "nspmount-*")
	if err != nil {
		return nil, err
	}
	inst.mountdir = tmpdir
	err = unix.Mount("cpu", tmpdir, "cgroup", 0, "cpu")
	if err != nil {
		inst.Dispose()
		return nil, err
	}
	err = os.Mkdir(filepath.Join(tmpdir, cgId), 0)
	if err != nil && errors.Unwrap(err) != syscall.EEXIST {
		inst.Dispose()
		return nil, err
	}
	return inst, nil
}