Thanks Chris On Monday, October 7, 2019 at 10:40:22 AM UTC-7, Chris Hines wrote: > > I am pretty sure that a "proc" in the trace visualization output is the > same as a "P" in the parlance of the Go runtime scheduler. In the scheduler > an OS thread is an "M" and even when using LockOSThread the locked > goroutine and thread need to be paired up with one of the scheduler's Ps in > order to execute the goroutine's code. There are always GOMAXPROCS # of Ps > in the scheduler. See the comment block starting at line 19 in this code > for more detail. https://golang.org/src/runtime/proc.go > > Hope that helps, > Chris > > On Sunday, October 6, 2019 at 7:47:43 AM UTC-4, Miki Tebeka wrote: >> >> Hi, >> >> I'm trying to understand output of the "go tool trace". I'm using >> runtime.LockOSThread, however the output of the trace tool shows goroutines >> moving between procs (which I *think* are OS threads). What am I missing? >> >> Code: >> package main >> >> import ( >> "fmt" >> "os" >> "runtime" >> "runtime/trace" >> "time" >> ) >> >> func sqrt(val float64) (float64, error) { >> if val < 0.0 { >> return 0.0, fmt.Errorf("sqrt of negative number") >> } >> >> if val == 0.0 { >> return 0.0, nil // shortcut >> } >> >> guess, epsilon := 1.0, 0.00001 >> for i := 0; i < 10000; i++ { >> diff := guess*guess - val >> if diff < 0 { >> diff = -diff >> } >> if diff <= epsilon { >> return guess, nil >> } >> guess = (val/guess + guess) / 2.0 >> } >> >> return 0.0, fmt.Errorf("can't find sqrt of %f", val) >> } >> >> func worker(id int) { >> runtime.LockOSThread() >> i := float64(0) >> for { >> for n := 0; n < 1000000; n++ { >> i += 13.2 >> _, err := sqrt(i) >> if err != nil { >> panic(err) >> } >> } >> runtime.Gosched() >> } >> } >> >> func main() { >> out, err := os.Create("trace.out") >> if err != nil { >> panic(err) >> } >> defer out.Close() >> if err := trace.Start(out); err != nil { >> panic(err) >> } >> defer trace.Stop() >> >> for i := 0; i < runtime.NumCPU(); i++ { >> go worker(i) >> } >> >> time.Sleep(3 * time.Second) >> } >> >> >> What I see in trace: >> >> [image: trace-out.png] >> >> Thanks, >> Miki >> >
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