cmd/trace: fix time scale

Integrate the latest trace-viewer changes.
It now handles nanoseconds without any issues (thanks to @egonelbre!).
So change timestamps from microseconds to nanoseconds.

Change-Id: I010f27effde7e80c9992e6f276f6912354d27df4
Reviewed-on: https://go-review.googlesource.com/11244Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Egon Elbre <egonelbre@gmail.com>

misc/trace/README.md

@@ -2,7 +2,7 @@ This directory contains helper file for trace viewer (`go tool trace`).
 
 `trace_viewer_lean.html` was generated by following
 [instructions](https://github.com/google/trace-viewer/wiki/Embedding)
-on revision `3c695b420a09db9933686fa958f1765c373c372e` using:
+on revision `280626ef607decf36291e290d5f0322b173e8a7f` using:
 ```
 trace-viewer$ ./vulcanize_trace_viewer --config=lean
 trace-viewer$ cp bin/trace_viewer_lean.html $GOROOT/misc/trace/

src/cmd/trace/trace.go

@@ -130,16 +130,17 @@ type frameNode struct {
 }
 
 type ViewerData struct {
-	Events []*ViewerEvent         `json:"traceEvents"`
-	Frames map[string]ViewerFrame `json:"stackFrames"`
+	Events   []*ViewerEvent         `json:"traceEvents"`
+	Frames   map[string]ViewerFrame `json:"stackFrames"`
+	TimeUnit string                 `json:"displayTimeUnit"`
 }
 
 type ViewerEvent struct {
 	Name     string      `json:"name,omitempty"`
 	Phase    string      `json:"ph"`
 	Scope    string      `json:"s,omitempty"`
-	Time     int64       `json:"ts"`
-	Dur      int64       `json:"dur,omitempty"`
+	Time     float64     `json:"ts"`
+	Dur      float64     `json:"dur,omitempty"`
 	Pid      uint64      `json:"pid"`
 	Tid      uint64      `json:"tid"`
 	ID       uint64      `json:"id,omitempty"`
@@ -172,6 +173,7 @@ func generateTrace(params *traceParams) ViewerData {
 	ctx := &traceContext{traceParams: params}
 	ctx.frameTree.children = make(map[uint64]frameNode)
 	ctx.data.Frames = make(map[string]ViewerFrame)
+	ctx.data.TimeUnit = "ns"
 	maxProc := 0
 	gnames := make(map[uint64]string)
 	for _, ev := range ctx.events {
@@ -322,12 +324,9 @@ func (ctx *traceContext) emit(e *ViewerEvent) {
 	ctx.data.Events = append(ctx.data.Events, e)
 }
 
-func (ctx *traceContext) time(ev *trace.Event) int64 {
-	// NOTE: trace viewer wants timestamps in microseconds and it does not
-	// handle fractional timestamps (rounds them). We give it timestamps
-	// in nanoseconds to avoid rounding. See:
-	// https://github.com/google/trace-viewer/issues/624
-	return ev.Ts - ctx.startTime
+func (ctx *traceContext) time(ev *trace.Event) float64 {
+	// Trace viewer wants timestamps in microseconds.
+	return float64(ev.Ts-ctx.startTime) / 1000
 }
 
 func (ctx *traceContext) proc(ev *trace.Event) uint64 {
@@ -408,6 +407,12 @@ func (ctx *traceContext) emitArrow(ev *trace.Event, name string) {
 		return
 	}
 
+	if ev.P == trace.NetpollP || ev.P == trace.TimerP || ev.P == trace.SyscallP {
+		// Trace-viewer discards arrows if they don't start/end inside of a slice or instant.
+		// So emit a fake instant at the start of the arrow.
+		ctx.emitInstant(&trace.Event{P: ev.P, Ts: ev.Ts}, "unblock")
+	}
+
 	ctx.arrowSeq++
 	ctx.emit(&ViewerEvent{Name: name, Phase: "s", Tid: ctx.proc(ev), ID: ctx.arrowSeq, Time: ctx.time(ev), Stack: ctx.stack(ev.Stk)})
 	ctx.emit(&ViewerEvent{Name: name, Phase: "t", Tid: ctx.proc(ev.Link), ID: ctx.arrowSeq, Time: ctx.time(ev.Link)})