Using profiles to track allocation and release of objects

[Partha Susarla]

v8go has a leakcheck sanitiser for the c++ code. But we can potentially use profiles to track allocation and release of objects within go, based on build tags.

I've created a PR, with profiles for isolate and context creation and disposal to show how these changes will look: #391. This can be used as shown below:

package main

import (
        "fmt"
        "os"
        "runtime/pprof"
        "strings"

        v8 "rogchap.com/v8go"
)

func DumpProfiles() {
        for _, prof := range pprof.Profiles() {
                if strings.HasPrefix(prof.Name(), "rogchap.com") {
                        _ = prof.WriteTo(os.Stdout, 1)
                }
        }
}

func Must[T any](t T, err error) T {
        if err != nil {
                panic(err)
        }
        return t
}

func main() {
        i := v8.NewIsolate()
        var vs []*v8.Value
        Must(v8.NewValue(i, "derp"))
        for j := 0; j < 1000; j++ {
                vs = append(vs, Must(v8.NewValue(i, "derp")))
        }

        fmt.Printf("Profile before Dispose:\n")
        DumpProfiles()

        for j := 1; j < 1000; j++ {
                vs[j].Release()
        }
        i.Dispose()

        fmt.Printf("Profile after Dispose:\n")
        DumpProfiles()
}

Which results in something like this, when compiled without tags:

profile-demo$ go run ./cmd/profile-demo
Profile before Dispose:
Profile after Dispose:

And with the tags, we get profiling output, like so:

profile-demo$ go run -tags v8profile ./cmd/profile-demo
Profile before Dispose:
rogchap.com/v8go/gv8go.Isolate profile: total 1
1 @ 0x8ca645 0x8cc0fc 0x8ce3dd 0x84afa7 0x876581
#       0x8ca644        rogchap.com/v8go.addIsolate+0x44        /home/partha/src/profile-demo/vendor/rogchap.com/v8go/profile.go:17
#       0x8cc0fb        rogchap.com/v8go.NewIsolate+0x9b        /home/partha/src/profile-demo/vendor/rogchap.com/v8go/isolate.go:62
#       0x8ce3dc        main.main+0x1c                          /home/partha/src/profile-demo/cmd/profile-demo/main.go:28
#       0x84afa6        runtime.main+0x206                      /usr/local/go/1.20.3/src/runtime/proc.go:250

1 @ 0x8ca725 0x8cd4d0 0x8cc875 0x8ce3f5 0x84afa7 0x876581
#       0x8ca724        rogchap.com/v8go.addValue+0x44          /home/partha/src/profile-demo/vendor/rogchap.com/v8go/profile.go:25
#       0x8cd4cf        rogchap.com/v8go.NewValue.func1+0x2f    /home/partha/src/profile-demo/vendor/rogchap.com/v8go/value.go:67
#       0x8cc874        rogchap.com/v8go.NewValue+0x2b4         /home/partha/src/profile-demo/vendor/rogchap.com/v8go/value.go:81
#       0x8ce3f4        main.main+0x34                          /home/partha/src/profile-demo/cmd/profile-demo/main.go:30
#       0x84afa6        runtime.main+0x206                      /usr/local/go/1.20.3/src/runtime/proc.go:250

Profile after Dispose:
rogchap.com/v8go/gv8go.Isolate profile: total 0
rogchap.com/v8go/gv8go.Value profile: total 2
1 @ 0x8ca725 0x8cd4d0 0x8cc875 0x8ce3f5 0x84afa7 0x876581
#       0x8ca724        rogchap.com/v8go.addValue+0x44          /home/partha/src/profile-demo/vendor/rogchap.com/v8go/profile.go:25
#       0x8cd4cf        rogchap.com/v8go.NewValue.func1+0x2f    /home/partha/src/profile-demo/vendor/rogchap.com/v8go/value.go:67
#       0x8cc874        rogchap.com/v8go.NewValue+0x2b4         /home/partha/src/profile-demo/vendor/rogchap.com/v8go/value.go:81
#       0x8ce3f4        main.main+0x34                          /home/partha/src/profile-demo/cmd/profile-demo/main.go:30
#       0x84afa6        runtime.main+0x206      

If there is an appetite for it, for both the maintainers and the community, I will work on the PR further to profile value.go as well.