How does one reliably obtain a cpu profile written to file? I tried
following the instructions in runtime/pprof.go, but the profile file is
most always empty... only on some magical moments can I discover a profile
file being written to disk.
I also tried calling f.Sync() on the file hanlde f, from main (below) every
minute, but that didn't help.
Supposedly the profiler is sampling at 100Hz, but I can't seem to get any
samples.
repro code:
$ cat addack.go
package main
import (
"fmt"
"log"
//"net/http"
_ "net/http/pprof"
"os"
"runtime/pprof"
)
const ProgramName = "profileme"
func main() {
f, err := os.Create(fmt.Sprintf("./addack-cpu-profile.%v", os.Getpid()))
if err != nil {
log.Fatal(err)
}
pprof.StartCPUProfile(f)
defer pprof.StopCPUProfile()
massiveAddack()
}
func massiveAddack() {
m := 0
for {
m = addSub(m)
fmt.Printf("m=%v\n", m)
}
}
func addSub(n int) int {
for i := 0; i < 1000000000; i++ {
n += i * i
}
return n
}
$ go run addack.go
m=3338615082255021824
m=6677230164510043648
m=-8430898826944486144
m=-5092283744689464320
m=-1753668662434442496
m=1584946419820579328
^Csignal: interrupt
$
$ ls -al|grep addack-cpu-profile.31523
-rw-rw-r-- 1 jason staff 0 Feb 7 15:50
addack-cpu-profile.31523 ## hmm.... profile file is always empty
$
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