cmd/go/internal/trace: add function to distinguish goroutines

trace.StartGoroutine will associate the trace information on the context with a new chrome profiler thread id. The chrome profiler doesn't expect multiple trace events to have the same thread id, so this will allow us to display concurrent events on the trace. Updates #38714 Change-Id: I81690861df4f444f14f02a99e0fe551395b660a7 Reviewed-on: https://go-review.googlesource.com/c/go/+/238542 Run-TryBot: Michael Matloob <[email protected]> TryBot-Result: Gobot Gobot <[email protected]> Reviewed-by: Jay Conrod <[email protected]> Reviewed-by: Bryan C. Mills <[email protected]>
golang · Aug 12, 2020 · cfbd1c7 · cfbd1c7
1 parent 2bfa45c
commit cfbd1c7
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Showing 2 changed files with 24 additions and 3 deletions.
diff --git a/go b/go
diff --git a/src/cmd/go/internal/trace/trace.go b/src/cmd/go/internal/trace/trace.go
@@ -33,20 +33,33 @@ func StartSpan(ctx context.Context, name string) (context.Context, *Span) {
 	if !ok {
 		return ctx, nil
 	}
-	childSpan := &Span{t: tc.t, name: name, start: time.Now()}
+	childSpan := &Span{t: tc.t, name: name, tid: tc.tid, start: time.Now()}
 	tc.t.writeEvent(&traceviewer.Event{
 		Name:  childSpan.name,
 		Time:  float64(childSpan.start.UnixNano()) / float64(time.Microsecond),
+		TID:   childSpan.tid,
 		Phase: "B",
 	})
-	ctx = context.WithValue(ctx, traceKey{}, traceContext{tc.t})
+	ctx = context.WithValue(ctx, traceKey{}, traceContext{tc.t, tc.tid})
 	return ctx, childSpan
 }
 
+// Goroutine associates the context with a new Thread ID. The Chrome trace viewer associates each
+// trace event with a thread, and doesn't expect events with the same thread id to happen at the
+// same time.
+func Goroutine(ctx context.Context) context.Context {
+	tc, ok := getTraceContext(ctx)
+	if !ok {
+		return ctx
+	}
+	return context.WithValue(ctx, traceKey{}, traceContext{tc.t, tc.t.getNextTID()})
+}
+
 type Span struct {
 	t *tracer
 
 	name  string
+	tid   uint64
 	start time.Time
 	end   time.Time
 }
@@ -59,12 +72,15 @@ func (s *Span) Done() {
 	s.t.writeEvent(&traceviewer.Event{
 		Name:  s.name,
 		Time:  float64(s.end.UnixNano()) / float64(time.Microsecond),
+		TID:   s.tid,
 		Phase: "E",
 	})
 }
 
 type tracer struct {
 	file chan traceFile // 1-buffered
+
+	nextTID uint64
 }
 
 func (t *tracer) writeEvent(ev *traceviewer.Event) error {
@@ -102,12 +118,17 @@ func (t *tracer) Close() error {
 	return firstErr
 }
 
+func (t *tracer) getNextTID() uint64 {
+	return atomic.AddUint64(&t.nextTID, 1)
+}
+
 // traceKey is the context key for tracing information. It is unexported to prevent collisions with context keys defined in
 // other packages.
 type traceKey struct{}
 
 type traceContext struct {
-	t *tracer
+	t   *tracer
+	tid uint64
 }
 
 // Start starts a trace which writes to the given file.