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go/src/cmd/trace/trace.go
Austin Clements b0392159f6 runtime,cmd/trace: trace GC STW events
Right now we only kind of sort of trace GC STW events. We emit events
around mark termination, but those start well after stopping the world
and end before starting it again, and we don't emit any events for
sweep termination.

Fix this by generalizing EvGCScanStart/EvGCScanDone. These were
already re-purposed to indicate mark termination (despite the names).
This commit renames them to EvGCSTWStart/EvGCSTWDone, adds an argument
to indicate the STW reason, and shuffles the runtime to generate them
right before stopping the world and right after starting the world,
respectively.

These events will make it possible to generate precise minimum mutator
utilization (MMU) graphs and could be useful in detecting
non-preemptible goroutines (e.g., #20792).

Change-Id: If95783f370781d8ef66addd94886028103a7c26f
Reviewed-on: https://go-review.googlesource.com/55411
Reviewed-by: Rick Hudson <rlh@golang.org>
2017-08-29 21:54:55 +00:00

722 lines
20 KiB
Go

// Copyright 2014 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package main
import (
"encoding/json"
"fmt"
"internal/trace"
"log"
"net/http"
"path/filepath"
"runtime"
"strconv"
"strings"
"time"
)
func init() {
http.HandleFunc("/trace", httpTrace)
http.HandleFunc("/jsontrace", httpJsonTrace)
http.HandleFunc("/trace_viewer_html", httpTraceViewerHTML)
}
// httpTrace serves either whole trace (goid==0) or trace for goid goroutine.
func httpTrace(w http.ResponseWriter, r *http.Request) {
_, err := parseEvents()
if err != nil {
http.Error(w, err.Error(), http.StatusInternalServerError)
return
}
if err := r.ParseForm(); err != nil {
http.Error(w, err.Error(), http.StatusInternalServerError)
return
}
html := strings.Replace(templTrace, "{{PARAMS}}", r.Form.Encode(), -1)
w.Write([]byte(html))
}
// See https://github.com/catapult-project/catapult/blob/master/tracing/docs/embedding-trace-viewer.md
// This is almost verbatim copy of:
// https://github.com/catapult-project/catapult/blob/master/tracing/bin/index.html
// on revision 5f9e4c3eaa555bdef18218a89f38c768303b7b6e.
var templTrace = `
<html>
<head>
<link href="/trace_viewer_html" rel="import">
<style type="text/css">
html, body {
box-sizing: border-box;
overflow: hidden;
margin: 0px;
padding: 0;
width: 100%;
height: 100%;
}
#trace-viewer {
width: 100%;
height: 100%;
}
#trace-viewer:focus {
outline: none;
}
</style>
<script>
'use strict';
(function() {
var viewer;
var url;
var model;
function load() {
var req = new XMLHttpRequest();
var is_binary = /[.]gz$/.test(url) || /[.]zip$/.test(url);
req.overrideMimeType('text/plain; charset=x-user-defined');
req.open('GET', url, true);
if (is_binary)
req.responseType = 'arraybuffer';
req.onreadystatechange = function(event) {
if (req.readyState !== 4)
return;
window.setTimeout(function() {
if (req.status === 200)
onResult(is_binary ? req.response : req.responseText);
else
onResultFail(req.status);
}, 0);
};
req.send(null);
}
function onResultFail(err) {
var overlay = new tr.ui.b.Overlay();
overlay.textContent = err + ': ' + url + ' could not be loaded';
overlay.title = 'Failed to fetch data';
overlay.visible = true;
}
function onResult(result) {
model = new tr.Model();
var opts = new tr.importer.ImportOptions();
opts.shiftWorldToZero = false;
var i = new tr.importer.Import(model, opts);
var p = i.importTracesWithProgressDialog([result]);
p.then(onModelLoaded, onImportFail);
}
function onModelLoaded() {
viewer.model = model;
viewer.viewTitle = "trace";
}
function onImportFail() {
var overlay = new tr.ui.b.Overlay();
overlay.textContent = tr.b.normalizeException(err).message;
overlay.title = 'Import error';
overlay.visible = true;
}
document.addEventListener('DOMContentLoaded', function() {
var container = document.createElement('track-view-container');
container.id = 'track_view_container';
viewer = document.createElement('tr-ui-timeline-view');
viewer.track_view_container = container;
viewer.appendChild(container);
viewer.id = 'trace-viewer';
viewer.globalMode = true;
document.body.appendChild(viewer);
url = '/jsontrace?{{PARAMS}}';
load();
});
}());
</script>
</head>
<body>
</body>
</html>
`
// httpTraceViewerHTML serves static part of trace-viewer.
// This URL is queried from templTrace HTML.
func httpTraceViewerHTML(w http.ResponseWriter, r *http.Request) {
http.ServeFile(w, r, filepath.Join(runtime.GOROOT(), "misc", "trace", "trace_viewer_full.html"))
}
// httpJsonTrace serves json trace, requested from within templTrace HTML.
func httpJsonTrace(w http.ResponseWriter, r *http.Request) {
// This is an AJAX handler, so instead of http.Error we use log.Printf to log errors.
events, err := parseEvents()
if err != nil {
log.Printf("failed to parse trace: %v", err)
return
}
params := &traceParams{
events: events,
endTime: int64(1<<63 - 1),
}
if goids := r.FormValue("goid"); goids != "" {
// If goid argument is present, we are rendering a trace for this particular goroutine.
goid, err := strconv.ParseUint(goids, 10, 64)
if err != nil {
log.Printf("failed to parse goid parameter '%v': %v", goids, err)
return
}
analyzeGoroutines(events)
g := gs[goid]
params.gtrace = true
params.startTime = g.StartTime
params.endTime = g.EndTime
params.maing = goid
params.gs = trace.RelatedGoroutines(events, goid)
}
data, err := generateTrace(params)
if err != nil {
log.Printf("failed to generate trace: %v", err)
return
}
if startStr, endStr := r.FormValue("start"), r.FormValue("end"); startStr != "" && endStr != "" {
// If start/end arguments are present, we are rendering a range of the trace.
start, err := strconv.ParseUint(startStr, 10, 64)
if err != nil {
log.Printf("failed to parse start parameter '%v': %v", startStr, err)
return
}
end, err := strconv.ParseUint(endStr, 10, 64)
if err != nil {
log.Printf("failed to parse end parameter '%v': %v", endStr, err)
return
}
if start >= uint64(len(data.Events)) || end <= start || end > uint64(len(data.Events)) {
log.Printf("bogus start/end parameters: %v/%v, trace size %v", start, end, len(data.Events))
return
}
data.Events = append(data.Events[start:end], data.Events[data.footer:]...)
}
err = json.NewEncoder(w).Encode(data)
if err != nil {
log.Printf("failed to serialize trace: %v", err)
return
}
}
type Range struct {
Name string
Start int
End int
}
// splitTrace splits the trace into a number of ranges,
// each resulting in approx 100MB of json output (trace viewer can hardly handle more).
func splitTrace(data ViewerData) []Range {
const rangeSize = 100 << 20
var ranges []Range
cw := new(countingWriter)
enc := json.NewEncoder(cw)
// First calculate size of the mandatory part of the trace.
// This includes stack traces and thread names.
data1 := data
data1.Events = data.Events[data.footer:]
enc.Encode(data1)
auxSize := cw.size
cw.size = 0
// Then calculate size of each individual event and group them into ranges.
for i, start := 0, 0; i < data.footer; i++ {
enc.Encode(data.Events[i])
if cw.size+auxSize > rangeSize || i == data.footer-1 {
ranges = append(ranges, Range{
Name: fmt.Sprintf("%v-%v", time.Duration(data.Events[start].Time*1000), time.Duration(data.Events[i].Time*1000)),
Start: start,
End: i + 1,
})
start = i + 1
cw.size = 0
}
}
if len(ranges) == 1 {
ranges = nil
}
return ranges
}
type countingWriter struct {
size int
}
func (cw *countingWriter) Write(data []byte) (int, error) {
cw.size += len(data)
return len(data), nil
}
type traceParams struct {
events []*trace.Event
gtrace bool
startTime int64
endTime int64
maing uint64
gs map[uint64]bool
}
type traceContext struct {
*traceParams
data ViewerData
frameTree frameNode
frameSeq int
arrowSeq uint64
gcount uint64
heapStats, prevHeapStats heapStats
threadStats, prevThreadStats threadStats
gstates, prevGstates [gStateCount]uint64
}
type heapStats struct {
heapAlloc uint64
nextGC uint64
}
type threadStats struct {
insyscall uint64
prunning uint64
}
type frameNode struct {
id int
children map[uint64]frameNode
}
type gState int
const (
gDead gState = iota
gRunnable
gRunning
gWaiting
gWaitingGC
gStateCount
)
type gInfo struct {
state gState // current state
name string // name chosen for this goroutine at first EvGoStart
start *trace.Event // most recent EvGoStart
markAssist *trace.Event // if non-nil, the mark assist currently running.
}
type ViewerData struct {
Events []*ViewerEvent `json:"traceEvents"`
Frames map[string]ViewerFrame `json:"stackFrames"`
TimeUnit string `json:"displayTimeUnit"`
// This is where mandatory part of the trace starts (e.g. thread names)
footer int
}
type ViewerEvent struct {
Name string `json:"name,omitempty"`
Phase string `json:"ph"`
Scope string `json:"s,omitempty"`
Time float64 `json:"ts"`
Dur float64 `json:"dur,omitempty"`
Pid uint64 `json:"pid"`
Tid uint64 `json:"tid"`
ID uint64 `json:"id,omitempty"`
Stack int `json:"sf,omitempty"`
EndStack int `json:"esf,omitempty"`
Arg interface{} `json:"args,omitempty"`
}
type ViewerFrame struct {
Name string `json:"name"`
Parent int `json:"parent,omitempty"`
}
type NameArg struct {
Name string `json:"name"`
}
type SortIndexArg struct {
Index int `json:"sort_index"`
}
// generateTrace generates json trace for trace-viewer:
// https://github.com/google/trace-viewer
// Trace format is described at:
// https://docs.google.com/document/d/1CvAClvFfyA5R-PhYUmn5OOQtYMH4h6I0nSsKchNAySU/view
// If gtrace=true, generate trace for goroutine goid, otherwise whole trace.
// startTime, endTime determine part of the trace that we are interested in.
// gset restricts goroutines that are included in the resulting trace.
func generateTrace(params *traceParams) (ViewerData, error) {
ctx := &traceContext{traceParams: params}
ctx.frameTree.children = make(map[uint64]frameNode)
ctx.data.Frames = make(map[string]ViewerFrame)
ctx.data.TimeUnit = "ns"
maxProc := 0
ginfos := make(map[uint64]*gInfo)
getGInfo := func(g uint64) *gInfo {
info, ok := ginfos[g]
if !ok {
info = &gInfo{}
ginfos[g] = info
}
return info
}
// Since we make many calls to setGState, we record a sticky
// error in setGStateErr and check it after every event.
var setGStateErr error
setGState := func(ev *trace.Event, g uint64, oldState, newState gState) {
info := getGInfo(g)
if oldState == gWaiting && info.state == gWaitingGC {
// For checking, gWaiting counts as any gWaiting*.
oldState = info.state
}
if info.state != oldState && setGStateErr == nil {
setGStateErr = fmt.Errorf("expected G %d to be in state %d, but got state %d", g, oldState, newState)
}
ctx.gstates[info.state]--
ctx.gstates[newState]++
info.state = newState
}
for _, ev := range ctx.events {
// Handle state transitions before we filter out events.
switch ev.Type {
case trace.EvGoStart, trace.EvGoStartLabel:
setGState(ev, ev.G, gRunnable, gRunning)
info := getGInfo(ev.G)
if info.name == "" {
if len(ev.Stk) > 0 {
info.name = fmt.Sprintf("G%v %s", ev.G, ev.Stk[0].Fn)
} else {
info.name = fmt.Sprintf("G%v", ev.G)
}
}
info.start = ev
case trace.EvProcStart:
ctx.threadStats.prunning++
case trace.EvProcStop:
ctx.threadStats.prunning--
case trace.EvGoCreate:
ctx.gcount++
setGState(ev, ev.Args[0], gDead, gRunnable)
case trace.EvGoEnd:
ctx.gcount--
setGState(ev, ev.G, gRunning, gDead)
case trace.EvGoUnblock:
setGState(ev, ev.Args[0], gWaiting, gRunnable)
case trace.EvGoSysExit:
setGState(ev, ev.G, gWaiting, gRunnable)
ctx.threadStats.insyscall--
case trace.EvGoSysBlock:
setGState(ev, ev.G, gRunning, gWaiting)
ctx.threadStats.insyscall++
case trace.EvGoSched, trace.EvGoPreempt:
setGState(ev, ev.G, gRunning, gRunnable)
case trace.EvGoStop,
trace.EvGoSleep, trace.EvGoBlock, trace.EvGoBlockSend, trace.EvGoBlockRecv,
trace.EvGoBlockSelect, trace.EvGoBlockSync, trace.EvGoBlockCond, trace.EvGoBlockNet:
setGState(ev, ev.G, gRunning, gWaiting)
case trace.EvGoBlockGC:
setGState(ev, ev.G, gRunning, gWaitingGC)
case trace.EvGCMarkAssistStart:
getGInfo(ev.G).markAssist = ev
case trace.EvGCMarkAssistDone:
getGInfo(ev.G).markAssist = nil
case trace.EvGoWaiting:
setGState(ev, ev.G, gRunnable, gWaiting)
case trace.EvGoInSyscall:
// Cancel out the effect of EvGoCreate at the beginning.
setGState(ev, ev.G, gRunnable, gWaiting)
ctx.threadStats.insyscall++
case trace.EvHeapAlloc:
ctx.heapStats.heapAlloc = ev.Args[0]
case trace.EvNextGC:
ctx.heapStats.nextGC = ev.Args[0]
}
if setGStateErr != nil {
return ctx.data, setGStateErr
}
// Ignore events that are from uninteresting goroutines
// or outside of the interesting timeframe.
if ctx.gs != nil && ev.P < trace.FakeP && !ctx.gs[ev.G] {
continue
}
if ev.Ts < ctx.startTime || ev.Ts > ctx.endTime {
continue
}
if ev.P < trace.FakeP && ev.P > maxProc {
maxProc = ev.P
}
// Emit trace objects.
switch ev.Type {
case trace.EvProcStart:
if ctx.gtrace {
continue
}
ctx.emitInstant(ev, "proc start")
case trace.EvProcStop:
if ctx.gtrace {
continue
}
ctx.emitInstant(ev, "proc stop")
case trace.EvGCStart:
ctx.emitSlice(ev, "GC")
case trace.EvGCDone:
case trace.EvGCSTWStart:
if ctx.gtrace {
continue
}
ctx.emitSlice(ev, fmt.Sprintf("STW (%s)", ev.SArgs[0]))
case trace.EvGCSTWDone:
case trace.EvGCMarkAssistStart:
// Mark assists can continue past preemptions, so truncate to the
// whichever comes first. We'll synthesize another slice if
// necessary in EvGoStart.
markFinish := ev.Link
goFinish := getGInfo(ev.G).start.Link
fakeMarkStart := *ev
text := "MARK ASSIST"
if markFinish == nil || markFinish.Ts > goFinish.Ts {
fakeMarkStart.Link = goFinish
text = "MARK ASSIST (unfinished)"
}
ctx.emitSlice(&fakeMarkStart, text)
case trace.EvGCSweepStart:
slice := ctx.emitSlice(ev, "SWEEP")
if done := ev.Link; done != nil && done.Args[0] != 0 {
slice.Arg = struct {
Swept uint64 `json:"Swept bytes"`
Reclaimed uint64 `json:"Reclaimed bytes"`
}{done.Args[0], done.Args[1]}
}
case trace.EvGoStart, trace.EvGoStartLabel:
info := getGInfo(ev.G)
if ev.Type == trace.EvGoStartLabel {
ctx.emitSlice(ev, ev.SArgs[0])
} else {
ctx.emitSlice(ev, info.name)
}
if info.markAssist != nil {
// If we're in a mark assist, synthesize a new slice, ending
// either when the mark assist ends or when we're descheduled.
markFinish := info.markAssist.Link
goFinish := ev.Link
fakeMarkStart := *ev
text := "MARK ASSIST (resumed, unfinished)"
if markFinish != nil && markFinish.Ts < goFinish.Ts {
fakeMarkStart.Link = markFinish
text = "MARK ASSIST (resumed)"
}
ctx.emitSlice(&fakeMarkStart, text)
}
case trace.EvGoCreate:
ctx.emitArrow(ev, "go")
case trace.EvGoUnblock:
ctx.emitArrow(ev, "unblock")
case trace.EvGoSysCall:
ctx.emitInstant(ev, "syscall")
case trace.EvGoSysExit:
ctx.emitArrow(ev, "sysexit")
}
// Emit any counter updates.
ctx.emitThreadCounters(ev)
ctx.emitHeapCounters(ev)
ctx.emitGoroutineCounters(ev)
}
ctx.data.footer = len(ctx.data.Events)
ctx.emit(&ViewerEvent{Name: "process_name", Phase: "M", Pid: 0, Arg: &NameArg{"PROCS"}})
ctx.emit(&ViewerEvent{Name: "process_sort_index", Phase: "M", Pid: 0, Arg: &SortIndexArg{1}})
ctx.emit(&ViewerEvent{Name: "process_name", Phase: "M", Pid: 1, Arg: &NameArg{"STATS"}})
ctx.emit(&ViewerEvent{Name: "process_sort_index", Phase: "M", Pid: 1, Arg: &SortIndexArg{0}})
ctx.emit(&ViewerEvent{Name: "thread_name", Phase: "M", Pid: 0, Tid: trace.GCP, Arg: &NameArg{"GC"}})
ctx.emit(&ViewerEvent{Name: "thread_sort_index", Phase: "M", Pid: 0, Tid: trace.GCP, Arg: &SortIndexArg{-6}})
ctx.emit(&ViewerEvent{Name: "thread_name", Phase: "M", Pid: 0, Tid: trace.NetpollP, Arg: &NameArg{"Network"}})
ctx.emit(&ViewerEvent{Name: "thread_sort_index", Phase: "M", Pid: 0, Tid: trace.NetpollP, Arg: &SortIndexArg{-5}})
ctx.emit(&ViewerEvent{Name: "thread_name", Phase: "M", Pid: 0, Tid: trace.TimerP, Arg: &NameArg{"Timers"}})
ctx.emit(&ViewerEvent{Name: "thread_sort_index", Phase: "M", Pid: 0, Tid: trace.TimerP, Arg: &SortIndexArg{-4}})
ctx.emit(&ViewerEvent{Name: "thread_name", Phase: "M", Pid: 0, Tid: trace.SyscallP, Arg: &NameArg{"Syscalls"}})
ctx.emit(&ViewerEvent{Name: "thread_sort_index", Phase: "M", Pid: 0, Tid: trace.SyscallP, Arg: &SortIndexArg{-3}})
if !ctx.gtrace {
for i := 0; i <= maxProc; i++ {
ctx.emit(&ViewerEvent{Name: "thread_name", Phase: "M", Pid: 0, Tid: uint64(i), Arg: &NameArg{fmt.Sprintf("Proc %v", i)}})
ctx.emit(&ViewerEvent{Name: "thread_sort_index", Phase: "M", Pid: 0, Tid: uint64(i), Arg: &SortIndexArg{i}})
}
}
if ctx.gtrace && ctx.gs != nil {
for k, v := range ginfos {
if !ctx.gs[k] {
continue
}
ctx.emit(&ViewerEvent{Name: "thread_name", Phase: "M", Pid: 0, Tid: k, Arg: &NameArg{v.name}})
}
ctx.emit(&ViewerEvent{Name: "thread_sort_index", Phase: "M", Pid: 0, Tid: ctx.maing, Arg: &SortIndexArg{-2}})
ctx.emit(&ViewerEvent{Name: "thread_sort_index", Phase: "M", Pid: 0, Tid: 0, Arg: &SortIndexArg{-1}})
}
return ctx.data, nil
}
func (ctx *traceContext) emit(e *ViewerEvent) {
ctx.data.Events = append(ctx.data.Events, e)
}
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 {
if ctx.gtrace && ev.P < trace.FakeP {
return ev.G
} else {
return uint64(ev.P)
}
}
func (ctx *traceContext) emitSlice(ev *trace.Event, name string) *ViewerEvent {
sl := &ViewerEvent{
Name: name,
Phase: "X",
Time: ctx.time(ev),
Dur: ctx.time(ev.Link) - ctx.time(ev),
Tid: ctx.proc(ev),
Stack: ctx.stack(ev.Stk),
EndStack: ctx.stack(ev.Link.Stk),
}
ctx.emit(sl)
return sl
}
type heapCountersArg struct {
Allocated uint64
NextGC uint64
}
func (ctx *traceContext) emitHeapCounters(ev *trace.Event) {
if ctx.gtrace {
return
}
if ctx.prevHeapStats == ctx.heapStats {
return
}
diff := uint64(0)
if ctx.heapStats.nextGC > ctx.heapStats.heapAlloc {
diff = ctx.heapStats.nextGC - ctx.heapStats.heapAlloc
}
ctx.emit(&ViewerEvent{Name: "Heap", Phase: "C", Time: ctx.time(ev), Pid: 1, Arg: &heapCountersArg{ctx.heapStats.heapAlloc, diff}})
ctx.prevHeapStats = ctx.heapStats
}
type goroutineCountersArg struct {
Running uint64
Runnable uint64
GCWaiting uint64
}
func (ctx *traceContext) emitGoroutineCounters(ev *trace.Event) {
if ctx.gtrace {
return
}
if ctx.prevGstates == ctx.gstates {
return
}
ctx.emit(&ViewerEvent{Name: "Goroutines", Phase: "C", Time: ctx.time(ev), Pid: 1, Arg: &goroutineCountersArg{ctx.gstates[gRunning], ctx.gstates[gRunnable], ctx.gstates[gWaitingGC]}})
ctx.prevGstates = ctx.gstates
}
type threadCountersArg struct {
Running uint64
InSyscall uint64
}
func (ctx *traceContext) emitThreadCounters(ev *trace.Event) {
if ctx.gtrace {
return
}
if ctx.prevThreadStats == ctx.threadStats {
return
}
ctx.emit(&ViewerEvent{Name: "Threads", Phase: "C", Time: ctx.time(ev), Pid: 1, Arg: &threadCountersArg{ctx.threadStats.prunning, ctx.threadStats.insyscall}})
ctx.prevThreadStats = ctx.threadStats
}
func (ctx *traceContext) emitInstant(ev *trace.Event, name string) {
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) {
if ev.Link == nil {
// The other end of the arrow is not captured in the trace.
// For example, a goroutine was unblocked but was not scheduled before trace stop.
return
}
if ctx.gtrace && (!ctx.gs[ev.Link.G] || ev.Link.Ts < ctx.startTime || ev.Link.Ts > ctx.endTime) {
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)})
}
func (ctx *traceContext) stack(stk []*trace.Frame) int {
return ctx.buildBranch(ctx.frameTree, stk)
}
// buildBranch builds one branch in the prefix tree rooted at ctx.frameTree.
func (ctx *traceContext) buildBranch(parent frameNode, stk []*trace.Frame) int {
if len(stk) == 0 {
return parent.id
}
last := len(stk) - 1
frame := stk[last]
stk = stk[:last]
node, ok := parent.children[frame.PC]
if !ok {
ctx.frameSeq++
node.id = ctx.frameSeq
node.children = make(map[uint64]frameNode)
parent.children[frame.PC] = node
ctx.data.Frames[strconv.Itoa(node.id)] = ViewerFrame{fmt.Sprintf("%v:%v", frame.Fn, frame.Line), parent.id}
}
return ctx.buildBranch(node, stk)
}