为什么探查器对我不起作用？

Question

Given the following toy code, I would expect to be able to run

go tool pprof cpu.prof

and get useful information about waster1 and waster2, but when I run top in pprof, all I get is:

Showing nodes accounting for 0, 0% of 0 total
      flat  flat%   sum%        cum   cum%

It is possible the problem is that I am using WSL to run Ubuntu on Windows 10.

Here is the code I am using:

package main

import (
    "fmt"
    "log"
    "os"
    "runtime/pprof"
)

func waster2() int {
    j := 0;
    for i := 0; i < 100; i++ {
        j += waster1()
    }
    return j
}

func waster1() int {
    j := 0;
    for i := 0; i < 10000; i++ {
        j++
    }
    return j
}

func main() {
    f, err := os.Create("cpu.prof")

    if err != nil {
        log.Fatal("could not create CPU profile: ", err)
    }

    if err := pprof.StartCPUProfile(f); err != nil {
        log.Fatal("could not start CPU profile: ", err)
    }

    defer pprof.StopCPUProfile()

    j := waster2()

    fmt.Println(j)
}

Answer 1

Running on windows also produces no samples in the profiler. The following article from the go blog states the following:

When CPU profiling is enabled, the Go program stops about 100 times per second and 
records a sample consisting of the program counters on the currently executing 
goroutine's stack.

When running your code takes less that 2ms, so does not allow the profiler to take samples. Increase your loop count from 100 to 10000 and then you should see some samples in your output.

On another note, remember to close your file f. Like so:

if err != nil {
    log.Fatal("could not create CPU profile: ", err)
}
defer f.Close()