cmd/trace: dump thread id on proc start

Augment ProcStart events with OS thread id.
This helps in scheduler locality analysis.

Change-Id: I93fea75d3072cf68de66110d0b59d07101badcb5
Reviewed-on: https://go-review.googlesource.com/7302
Reviewed-by: Keith Randall <khr@golang.org>

4 files changed, 14 insertions, 6 deletions

diff --git a/src/cmd/trace/trace.go b/src/cmd/trace/trace.go
index 41a56b92bb..a572ed8f28 100644
--- a/src/cmd/trace/trace.go
+++ b/src/cmd/trace/trace.go
@@ -391,7 +391,14 @@ func (ctx *traceContext) emitThreadCounters(ev *trace.Event) {
 }
 
 func (ctx *traceContext) emitInstant(ev *trace.Event, name string) {
-	ctx.emit(&ViewerEvent{Name: name, Phase: "I", Scope: "t", Time: ctx.time(ev), Tid: ctx.proc(ev), Stack: ctx.stack(ev.Stk)})
+	var arg interface{}
+	if ev.Type == trace.EvProcStart {
+		type Arg struct {
+			ThreadID uint64
+		}
+		arg = &Arg{ev.Args[0]}
+	}
+	ctx.emit(&ViewerEvent{Name: name, Phase: "I", Scope: "t", Time: ctx.time(ev), Tid: ctx.proc(ev), Stack: ctx.stack(ev.Stk), Arg: arg})
 }
 
 func (ctx *traceContext) emitArrow(ev *trace.Event, name string) {
diff --git a/src/internal/trace/parser.go b/src/internal/trace/parser.go
index 4e5f534d4c..44a2e66cfe 100644
--- a/src/internal/trace/parser.go
+++ b/src/internal/trace/parser.go
@@ -584,7 +584,7 @@ const (
 	EvFrequency      = 2  // contains tracer timer frequency [frequency (ticks per second)]
 	EvStack          = 3  // stack [stack id, number of PCs, array of PCs]
 	EvGomaxprocs     = 4  // current value of GOMAXPROCS [timestamp, GOMAXPROCS, stack id]
-	EvProcStart      = 5  // start of P [timestamp]
+	EvProcStart      = 5  // start of P [timestamp, thread id]
 	EvProcStop       = 6  // stop of P [timestamp]
 	EvGCStart        = 7  // GC start [timestamp, stack id]
 	EvGCDone         = 8  // GC done [timestamp]
@@ -628,7 +628,7 @@ var EventDescriptions = [EvCount]struct {
 	EvFrequency:      {"Frequency", false, []string{"freq"}},
 	EvStack:          {"Stack", false, []string{"id", "siz"}},
 	EvGomaxprocs:     {"Gomaxprocs", true, []string{"procs"}},
-	EvProcStart:      {"ProcStart", false, []string{}},
+	EvProcStart:      {"ProcStart", false, []string{"thread"}},
 	EvProcStop:       {"ProcStop", false, []string{}},
 	EvGCStart:        {"GCStart", true, []string{}},
 	EvGCDone:         {"GCDone", false, []string{}},
diff --git a/src/runtime/pprof/trace_test.go b/src/runtime/pprof/trace_test.go
index efec9a6ba2..c57f4b8db1 100644
--- a/src/runtime/pprof/trace_test.go
+++ b/src/runtime/pprof/trace_test.go
@@ -101,7 +101,7 @@ func TestTraceStress(t *testing.T) {
 		<-done
 		wg.Done()
 	}()
-	time.Sleep(time.Millisecond)
+	time.Sleep(time.Millisecond) // give the goroutine above time to block
 
 	buf := new(bytes.Buffer)
 	if err := StartTrace(buf); err != nil {
@@ -109,6 +109,7 @@ func TestTraceStress(t *testing.T) {
 	}
 
 	procs := runtime.GOMAXPROCS(10)
+	time.Sleep(50 * time.Millisecond) // test proc stop/start events
 
 	go func() {
 		runtime.LockOSThread()
diff --git a/src/runtime/trace.go b/src/runtime/trace.go
index ea35343552..eb3ceb2f38 100644
--- a/src/runtime/trace.go
+++ b/src/runtime/trace.go
@@ -21,7 +21,7 @@ const (
 	traceEvFrequency      = 2  // contains tracer timer frequency [frequency (ticks per second)]
 	traceEvStack          = 3  // stack [stack id, number of PCs, array of PCs]
 	traceEvGomaxprocs     = 4  // current value of GOMAXPROCS [timestamp, GOMAXPROCS, stack id]
-	traceEvProcStart      = 5  // start of P [timestamp]
+	traceEvProcStart      = 5  // start of P [timestamp, thread id]
 	traceEvProcStop       = 6  // stop of P [timestamp]
 	traceEvGCStart        = 7  // GC start [timestamp, stack id]
 	traceEvGCDone         = 8  // GC done [timestamp]
@@ -716,7 +716,7 @@ func traceGomaxprocs(procs int32) {
 }
 
 func traceProcStart() {
-	traceEvent(traceEvProcStart, -1)
+	traceEvent(traceEvProcStart, -1, uint64(getg().m.id))
 }
 
 func traceProcStop(pp *p) {