prof.go

package vinamax2

// provides run-time profiling.

import (
	"io/ioutil"
	"os"
	"os/exec"
	"runtime/pprof"
)

// start CPU profiling, safe to cpu.pprof
func InitCPUProfile() {
	fname := "cpu.pprof"
	f, err := os.Create(fname)
	FatalErr(err)
	err = pprof.StartCPUProfile(f)
	FatalErr(err)
	Log("writing CPU profile to", fname)

	// at exit: exec go tool pprof to generate SVG output
	AtExit(func() {
		pprof.StopCPUProfile()
		me := procSelfExe()
		outfile := fname + ".svg"
		saveCmdOutput(outfile, "go", "tool", "pprof", "-svg", me, fname)
	})
}

// start memory profiling
func InitMemProfile() {
	Log("memory profile enabled")
	AtExit(func() {
		fname := "mem.pprof"
		f, err := os.Create(fname)
		defer f.Close()
		LogErr(err, "memory profile") // during cleanup, should not panic/exit
		Log("writing memory profile to", fname)
		LogErr(pprof.WriteHeapProfile(f), "memory profile")
		me := procSelfExe()
		outfile := fname + ".svg"
		saveCmdOutput(outfile, "go", "tool", "pprof", "-svg", "--inuse_objects", me, fname)
	})
}

// Exec command and write output to outfile.
func saveCmdOutput(outfile string, cmd string, args ...string) {
	Log("exec:", cmd, args, ">", outfile)
	out, err := exec.Command(cmd, args...).Output() // TODO: stderr is ignored
	if err != nil {
		Log("exec ", cmd, args, err, string(out))
	}
	// on error: write anyway, clobbers output file.
	e := ioutil.WriteFile(outfile, out, 0666)
	LogErr(e, "writing", outfile)
}

// path to the executable.
func procSelfExe() string {
	me, err := os.Readlink("/proc/self/exe")
	PanicErr(err)
	return me
}