how_to_trace_cgo

Profile cgo with trace

Select use go or cgo in main function.

for i := 0; i < cores; i++ {
    w := worker{id: i, reqCh: reqCh}
    go w.DoGo() // Use GO
    // go w.DoCgo()  // Use cgo
}

Trace profile

Use gotip.

go tool trace has some bugs in Go v1.14.

** install gotip **

$ go get golang.org/dl/gotip
$ gotip download

1. run code

go run main.go

1. open trace.out

gotip tool trace ./trace.out

** Why cgo so fast? **

1. go cost about: 50s

(base) ➜  how_to_trace_cgo git:(how-to-trace) ✗ time ./go.out 
2020/03/07 00:53:39 got res=-9899999998
2020/03/07 00:53:39 got res=-9900000004
2020/03/07 00:53:39 got res=-9900000000
2020/03/07 00:53:39 got res=-9900000002
2020/03/07 00:53:39 got res=-9900000008
2020/03/07 00:53:39 got res=-9900000006
2020/03/07 00:53:39 got res=-9899999994
2020/03/07 00:53:39 got res=-9900000000
2020/03/07 00:53:54 got res=-9899999996
2020/03/07 00:53:54 got res=-9899999992
./go.out  263.80s user 0.76s system 522% cpu 50.656 total

1. go+cgo only cost about: 19.3s

(base) ➜  how_to_trace_cgo git:(how-to-trace) ✗ time ./cgo.out 
2020/03/07 00:54:12 got res=-1310065404
2020/03/07 00:54:12 got res=-1310065410
2020/03/07 00:54:12 got res=-1310065402
2020/03/07 00:54:12 got res=-1310065406
2020/03/07 00:54:12 got res=-1310065408
2020/03/07 00:54:12 got res=-1310065408
2020/03/07 00:54:12 got res=-1310065416
2020/03/07 00:54:12 got res=-1310065412
2020/03/07 00:54:18 got res=-1310065414
2020/03/07 00:54:19 got res=-1310065400
./cgo.out  91.93s user 0.24s system 477% cpu 19.302 total

1. UPDATE If I remove all c code in main.go, even I do not use it, then speedup speed of pure go.

pure go cost about: 24s

(base) ➜  how_to_trace_cgo git:(how-to-trace) ✗ time ./go.out
2020/03/07 01:26:20 got res=-9900000004
2020/03/07 01:26:20 got res=-9900000000
2020/03/07 01:26:20 got res=-9900000000
2020/03/07 01:26:20 got res=-9900000008
2020/03/07 01:26:20 got res=-9899999992
2020/03/07 01:26:20 got res=-9900000006
2020/03/07 01:26:20 got res=-9899999998
2020/03/07 01:26:20 got res=-9900000002
2020/03/07 01:26:29 got res=-9899999996
2020/03/07 01:26:29 got res=-9899999994
./go.out  126.53s user 0.26s system 523% cpu 24.240 total

Trace web:

Cgo trace:

go trace: