src/cmd/trace/pprof.go - go - Git at Google

 // 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.

 // Serving of pprof-like profiles.

 package main

 import (
 	"bufio"
 	"fmt"
 	exec "internal/execabs"
 	"internal/trace"
 	"io"
 	"net/http"
 	"os"
 	"path/filepath"
 	"runtime"
 	"sort"
 	"strconv"
 	"time"

 	"github.com/google/pprof/profile"
 )

 func goCmd() string {
 	var exeSuffix string
 	if runtime.GOOS == "windows" {
 		exeSuffix = ".exe"
 	}
 	path := filepath.Join(runtime.GOROOT(), "bin", "go"+exeSuffix)
 	if _, err := os.Stat(path); err == nil {
 		return path
 	}
 	return "go"
 }

 func init() {
 	http.HandleFunc("/io", serveSVGProfile(pprofByGoroutine(computePprofIO)))
 	http.HandleFunc("/block", serveSVGProfile(pprofByGoroutine(computePprofBlock)))
 	http.HandleFunc("/syscall", serveSVGProfile(pprofByGoroutine(computePprofSyscall)))
 	http.HandleFunc("/sched", serveSVGProfile(pprofByGoroutine(computePprofSched)))

 	http.HandleFunc("/regionio", serveSVGProfile(pprofByRegion(computePprofIO)))
 	http.HandleFunc("/regionblock", serveSVGProfile(pprofByRegion(computePprofBlock)))
 	http.HandleFunc("/regionsyscall", serveSVGProfile(pprofByRegion(computePprofSyscall)))
 	http.HandleFunc("/regionsched", serveSVGProfile(pprofByRegion(computePprofSched)))
 }

 // Record represents one entry in pprof-like profiles.
 type Record struct {
 	stk  []*trace.Frame
 	n    uint64
 	time int64
 }

 // interval represents a time interval in the trace.
 type interval struct {
 	begin, end int64 // nanoseconds.
 }

 func pprofByGoroutine(compute func(io.Writer, map[uint64][]interval, []*trace.Event) error) func(w io.Writer, r *http.Request) error {
 	return func(w io.Writer, r *http.Request) error {
 		id := r.FormValue("id")
 		events, err := parseEvents()
 		if err != nil {
 			return err
 		}
 		gToIntervals, err := pprofMatchingGoroutines(id, events)
 		if err != nil {
 			return err
 		}
 		return compute(w, gToIntervals, events)
 	}
 }

 func pprofByRegion(compute func(io.Writer, map[uint64][]interval, []*trace.Event) error) func(w io.Writer, r *http.Request) error {
 	return func(w io.Writer, r *http.Request) error {
 		filter, err := newRegionFilter(r)
 		if err != nil {
 			return err
 		}
 		gToIntervals, err := pprofMatchingRegions(filter)
 		if err != nil {
 			return err
 		}
 		events, _ := parseEvents()

 		return compute(w, gToIntervals, events)
 	}
 }

 // pprofMatchingGoroutines parses the goroutine type id string (i.e. pc)
 // and returns the ids of goroutines of the matching type and its interval.
 // If the id string is empty, returns nil without an error.
 func pprofMatchingGoroutines(id string, events []*trace.Event) (map[uint64][]interval, error) {
 	if id == "" {
 		return nil, nil
 	}
 	pc, err := strconv.ParseUint(id, 10, 64) // id is string
 	if err != nil {
 		return nil, fmt.Errorf("invalid goroutine type: %v", id)
 	}
 	analyzeGoroutines(events)
 	var res map[uint64][]interval
 	for _, g := range gs {
 		if g.PC != pc {
 			continue
 		}
 		if res == nil {
 			res = make(map[uint64][]interval)
 		}
 		endTime := g.EndTime
 		if g.EndTime == 0 {
 			endTime = lastTimestamp() // the trace doesn't include the goroutine end event. Use the trace end time.
 		}
 		res[g.ID] = []interval{{begin: g.StartTime, end: endTime}}
 	}
 	if len(res) == 0 && id != "" {
 		return nil, fmt.Errorf("failed to find matching goroutines for id: %s", id)
 	}
 	return res, nil
 }

 // pprofMatchingRegions returns the time intervals of matching regions
 // grouped by the goroutine id. If the filter is nil, returns nil without an error.
 func pprofMatchingRegions(filter *regionFilter) (map[uint64][]interval, error) {
 	res, err := analyzeAnnotations()
 	if err != nil {
 		return nil, err
 	}
 	if filter == nil {
 		return nil, nil
 	}

 	gToIntervals := make(map[uint64][]interval)
 	for id, regions := range res.regions {
 		for _, s := range regions {
 			if filter.match(id, s) {
 				gToIntervals[s.G] = append(gToIntervals[s.G], interval{begin: s.firstTimestamp(), end: s.lastTimestamp()})
 			}
 		}
 	}

 	for g, intervals := range gToIntervals {
 		// in order to remove nested regions and
 		// consider only the outermost regions,
 		// first, we sort based on the start time
 		// and then scan through to select only the outermost regions.
 		sort.Slice(intervals, func(i, j int) bool {
 			x := intervals[i].begin
 			y := intervals[j].begin
 			if x == y {
 				return intervals[i].end < intervals[j].end
 			}
 			return x < y
 		})
 		var lastTimestamp int64
 		var n int
 		// select only the outermost regions.
 		for _, i := range intervals {
 			if lastTimestamp <= i.begin {
 				intervals[n] = i // new non-overlapping region starts.
 				lastTimestamp = i.end
 				n++
 			} // otherwise, skip because this region overlaps with a previous region.
 		}
 		gToIntervals[g] = intervals[:n]
 	}
 	return gToIntervals, nil
 }

 // computePprofIO generates IO pprof-like profile (time spent in IO wait, currently only network blocking event).
 func computePprofIO(w io.Writer, gToIntervals map[uint64][]interval, events []*trace.Event) error {
 	prof := make(map[uint64]Record)
 	for _, ev := range events {
 		if ev.Type != trace.EvGoBlockNet || ev.Link == nil || ev.StkID == 0 || len(ev.Stk) == 0 {
 			continue
 		}
 		overlapping := pprofOverlappingDuration(gToIntervals, ev)
 		if overlapping > 0 {
 			rec := prof[ev.StkID]
 			rec.stk = ev.Stk
 			rec.n++
 			rec.time += overlapping.Nanoseconds()
 			prof[ev.StkID] = rec
 		}
 	}
 	return buildProfile(prof).Write(w)
 }

 // computePprofBlock generates blocking pprof-like profile (time spent blocked on synchronization primitives).
 func computePprofBlock(w io.Writer, gToIntervals map[uint64][]interval, events []*trace.Event) error {
 	prof := make(map[uint64]Record)
 	for _, ev := range events {
 		switch ev.Type {
 		case trace.EvGoBlockSend, trace.EvGoBlockRecv, trace.EvGoBlockSelect,
 			trace.EvGoBlockSync, trace.EvGoBlockCond, trace.EvGoBlockGC:
 			// TODO(hyangah): figure out why EvGoBlockGC should be here.
 			// EvGoBlockGC indicates the goroutine blocks on GC assist, not
 			// on synchronization primitives.
 		default:
 			continue
 		}
 		if ev.Link == nil || ev.StkID == 0 || len(ev.Stk) == 0 {
 			continue
 		}
 		overlapping := pprofOverlappingDuration(gToIntervals, ev)
 		if overlapping > 0 {
 			rec := prof[ev.StkID]
 			rec.stk = ev.Stk
 			rec.n++
 			rec.time += overlapping.Nanoseconds()
 			prof[ev.StkID] = rec
 		}
 	}
 	return buildProfile(prof).Write(w)
 }

 // computePprofSyscall generates syscall pprof-like profile (time spent blocked in syscalls).
 func computePprofSyscall(w io.Writer, gToIntervals map[uint64][]interval, events []*trace.Event) error {
 	prof := make(map[uint64]Record)
 	for _, ev := range events {
 		if ev.Type != trace.EvGoSysCall || ev.Link == nil || ev.StkID == 0 || len(ev.Stk) == 0 {
 			continue
 		}
 		overlapping := pprofOverlappingDuration(gToIntervals, ev)
 		if overlapping > 0 {
 			rec := prof[ev.StkID]
 			rec.stk = ev.Stk
 			rec.n++
 			rec.time += overlapping.Nanoseconds()
 			prof[ev.StkID] = rec
 		}
 	}
 	return buildProfile(prof).Write(w)
 }

 // computePprofSched generates scheduler latency pprof-like profile
 // (time between a goroutine become runnable and actually scheduled for execution).
 func computePprofSched(w io.Writer, gToIntervals map[uint64][]interval, events []*trace.Event) error {
 	prof := make(map[uint64]Record)
 	for _, ev := range events {
 		if (ev.Type != trace.EvGoUnblock && ev.Type != trace.EvGoCreate) ||
 			ev.Link == nil || ev.StkID == 0 || len(ev.Stk) == 0 {
 			continue
 		}
 		overlapping := pprofOverlappingDuration(gToIntervals, ev)
 		if overlapping > 0 {
 			rec := prof[ev.StkID]
 			rec.stk = ev.Stk
 			rec.n++
 			rec.time += overlapping.Nanoseconds()
 			prof[ev.StkID] = rec
 		}
 	}
 	return buildProfile(prof).Write(w)
 }

 // pprofOverlappingDuration returns the overlapping duration between
 // the time intervals in gToIntervals and the specified event.
 // If gToIntervals is nil, this simply returns the event's duration.
 func pprofOverlappingDuration(gToIntervals map[uint64][]interval, ev *trace.Event) time.Duration {
 	if gToIntervals == nil { // No filtering.
 		return time.Duration(ev.Link.Ts-ev.Ts) * time.Nanosecond
 	}
 	intervals := gToIntervals[ev.G]
 	if len(intervals) == 0 {
 		return 0
 	}

 	var overlapping time.Duration
 	for _, i := range intervals {
 		if o := overlappingDuration(i.begin, i.end, ev.Ts, ev.Link.Ts); o > 0 {
 			overlapping += o
 		}
 	}
 	return overlapping
 }

 // serveSVGProfile serves pprof-like profile generated by prof as svg.
 func serveSVGProfile(prof func(w io.Writer, r *http.Request) error) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {

 		if r.FormValue("raw") != "" {
 			w.Header().Set("Content-Type", "application/octet-stream")
 			if err := prof(w, r); err != nil {
 				w.Header().Set("Content-Type", "text/plain; charset=utf-8")
 				w.Header().Set("X-Go-Pprof", "1")
 				http.Error(w, fmt.Sprintf("failed to get profile: %v", err), http.StatusInternalServerError)
 				return
 			}
 			return
 		}

 		blockf, err := os.CreateTemp("", "block")
 		if err != nil {
 			http.Error(w, fmt.Sprintf("failed to create temp file: %v", err), http.StatusInternalServerError)
 			return
 		}
 		defer func() {
 			blockf.Close()
 			os.Remove(blockf.Name())
 		}()
 		blockb := bufio.NewWriter(blockf)
 		if err := prof(blockb, r); err != nil {
 			http.Error(w, fmt.Sprintf("failed to generate profile: %v", err), http.StatusInternalServerError)
 			return
 		}
 		if err := blockb.Flush(); err != nil {
 			http.Error(w, fmt.Sprintf("failed to flush temp file: %v", err), http.StatusInternalServerError)
 			return
 		}
 		if err := blockf.Close(); err != nil {
 			http.Error(w, fmt.Sprintf("failed to close temp file: %v", err), http.StatusInternalServerError)
 			return
 		}
 		svgFilename := blockf.Name() + ".svg"
 		if output, err := exec.Command(goCmd(), "tool", "pprof", "-svg", "-output", svgFilename, blockf.Name()).CombinedOutput(); err != nil {
 			http.Error(w, fmt.Sprintf("failed to execute go tool pprof: %v\n%s", err, output), http.StatusInternalServerError)
 			return
 		}
 		defer os.Remove(svgFilename)
 		w.Header().Set("Content-Type", "image/svg+xml")
 		http.ServeFile(w, r, svgFilename)
 	}
 }

 func buildProfile(prof map[uint64]Record) *profile.Profile {
 	p := &profile.Profile{
 		PeriodType: &profile.ValueType{Type: "trace", Unit: "count"},
 		Period:     1,
 		SampleType: []*profile.ValueType{
 			{Type: "contentions", Unit: "count"},
 			{Type: "delay", Unit: "nanoseconds"},
 		},
 	}
 	locs := make(map[uint64]*profile.Location)
 	funcs := make(map[string]*profile.Function)
 	for _, rec := range prof {
 		var sloc []*profile.Location
 		for _, frame := range rec.stk {
 			loc := locs[frame.PC]
 			if loc == nil {
 				fn := funcs[frame.File+frame.Fn]
 				if fn == nil {
 					fn = &profile.Function{
 						ID:         uint64(len(p.Function) + 1),
 						Name:       frame.Fn,
 						SystemName: frame.Fn,
 						Filename:   frame.File,
 					}
 					p.Function = append(p.Function, fn)
 					funcs[frame.File+frame.Fn] = fn
 				}
 				loc = &profile.Location{
 					ID:      uint64(len(p.Location) + 1),
 					Address: frame.PC,
 					Line: []profile.Line{
 						{
 							Function: fn,
 							Line:     int64(frame.Line),
 						},
 					},
 				}
 				p.Location = append(p.Location, loc)
 				locs[frame.PC] = loc
 			}
 			sloc = append(sloc, loc)
 		}
 		p.Sample = append(p.Sample, &profile.Sample{
 			Value:    []int64{int64(rec.n), rec.time},
 			Location: sloc,
 		})
 	}
 	return p
 }
	// 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.

	// Serving of pprof-like profiles.

	package main

	import (
	"bufio"
	"fmt"
	exec "internal/execabs"
	"internal/trace"
	"io"
	"net/http"
	"os"
	"path/filepath"
	"runtime"
	"sort"
	"strconv"
	"time"

	"github.com/google/pprof/profile"
	)

	func goCmd() string {
	var exeSuffix string
	if runtime.GOOS == "windows" {
	exeSuffix = ".exe"
	}
	path := filepath.Join(runtime.GOROOT(), "bin", "go"+exeSuffix)
	if _, err := os.Stat(path); err == nil {
	return path
	}
	return "go"
	}

	func init() {
	http.HandleFunc("/io", serveSVGProfile(pprofByGoroutine(computePprofIO)))
	http.HandleFunc("/block", serveSVGProfile(pprofByGoroutine(computePprofBlock)))
	http.HandleFunc("/syscall", serveSVGProfile(pprofByGoroutine(computePprofSyscall)))
	http.HandleFunc("/sched", serveSVGProfile(pprofByGoroutine(computePprofSched)))

	http.HandleFunc("/regionio", serveSVGProfile(pprofByRegion(computePprofIO)))
	http.HandleFunc("/regionblock", serveSVGProfile(pprofByRegion(computePprofBlock)))
	http.HandleFunc("/regionsyscall", serveSVGProfile(pprofByRegion(computePprofSyscall)))
	http.HandleFunc("/regionsched", serveSVGProfile(pprofByRegion(computePprofSched)))
	}

	// Record represents one entry in pprof-like profiles.
	type Record struct {
	stk []*trace.Frame
	n uint64
	time int64
	}

	// interval represents a time interval in the trace.
	type interval struct {
	begin, end int64 // nanoseconds.
	}

	func pprofByGoroutine(compute func(io.Writer, map[uint64][]interval, []trace.Event) error) func(w io.Writer, r http.Request) error {
	return func(w io.Writer, r *http.Request) error {
	id := r.FormValue("id")
	events, err := parseEvents()
	if err != nil {
	return err
	}
	gToIntervals, err := pprofMatchingGoroutines(id, events)
	if err != nil {
	return err
	}
	return compute(w, gToIntervals, events)
	}
	}

	func pprofByRegion(compute func(io.Writer, map[uint64][]interval, []trace.Event) error) func(w io.Writer, r http.Request) error {
	return func(w io.Writer, r *http.Request) error {
	filter, err := newRegionFilter(r)
	if err != nil {
	return err
	}
	gToIntervals, err := pprofMatchingRegions(filter)
	if err != nil {
	return err
	}
	events, _ := parseEvents()

	return compute(w, gToIntervals, events)
	}
	}

	// pprofMatchingGoroutines parses the goroutine type id string (i.e. pc)
	// and returns the ids of goroutines of the matching type and its interval.
	// If the id string is empty, returns nil without an error.
	func pprofMatchingGoroutines(id string, events []*trace.Event) (map[uint64][]interval, error) {
	if id == "" {
	return nil, nil
	}
	pc, err := strconv.ParseUint(id, 10, 64) // id is string
	if err != nil {
	return nil, fmt.Errorf("invalid goroutine type: %v", id)
	}
	analyzeGoroutines(events)
	var res map[uint64][]interval
	for _, g := range gs {
	if g.PC != pc {
	continue
	}
	if res == nil {
	res = make(map[uint64][]interval)
	}
	endTime := g.EndTime
	if g.EndTime == 0 {
	endTime = lastTimestamp() // the trace doesn't include the goroutine end event. Use the trace end time.
	}
	res[g.ID] = []interval{{begin: g.StartTime, end: endTime}}
	}
	if len(res) == 0 && id != "" {
	return nil, fmt.Errorf("failed to find matching goroutines for id: %s", id)
	}
	return res, nil
	}

	// pprofMatchingRegions returns the time intervals of matching regions
	// grouped by the goroutine id. If the filter is nil, returns nil without an error.
	func pprofMatchingRegions(filter *regionFilter) (map[uint64][]interval, error) {
	res, err := analyzeAnnotations()
	if err != nil {
	return nil, err
	}
	if filter == nil {
	return nil, nil
	}

	gToIntervals := make(map[uint64][]interval)
	for id, regions := range res.regions {
	for _, s := range regions {
	if filter.match(id, s) {
	gToIntervals[s.G] = append(gToIntervals[s.G], interval{begin: s.firstTimestamp(), end: s.lastTimestamp()})
	}
	}
	}

	for g, intervals := range gToIntervals {
	// in order to remove nested regions and
	// consider only the outermost regions,
	// first, we sort based on the start time
	// and then scan through to select only the outermost regions.
	sort.Slice(intervals, func(i, j int) bool {
	x := intervals[i].begin
	y := intervals[j].begin
	if x == y {
	return intervals[i].end < intervals[j].end
	}
	return x < y
	})
	var lastTimestamp int64
	var n int
	// select only the outermost regions.
	for _, i := range intervals {
	if lastTimestamp <= i.begin {
	intervals[n] = i // new non-overlapping region starts.
	lastTimestamp = i.end
	n++
	} // otherwise, skip because this region overlaps with a previous region.
	}
	gToIntervals[g] = intervals[:n]
	}
	return gToIntervals, nil
	}

	// computePprofIO generates IO pprof-like profile (time spent in IO wait, currently only network blocking event).
	func computePprofIO(w io.Writer, gToIntervals map[uint64][]interval, events []*trace.Event) error {
	prof := make(map[uint64]Record)
	for _, ev := range events {
	if ev.Type != trace.EvGoBlockNet \|\| ev.Link == nil \|\| ev.StkID == 0 \|\| len(ev.Stk) == 0 {
	continue
	}
	overlapping := pprofOverlappingDuration(gToIntervals, ev)
	if overlapping > 0 {
	rec := prof[ev.StkID]
	rec.stk = ev.Stk
	rec.n++
	rec.time += overlapping.Nanoseconds()
	prof[ev.StkID] = rec
	}
	}
	return buildProfile(prof).Write(w)
	}

	// computePprofBlock generates blocking pprof-like profile (time spent blocked on synchronization primitives).
	func computePprofBlock(w io.Writer, gToIntervals map[uint64][]interval, events []*trace.Event) error {
	prof := make(map[uint64]Record)
	for _, ev := range events {
	switch ev.Type {
	case trace.EvGoBlockSend, trace.EvGoBlockRecv, trace.EvGoBlockSelect,
	trace.EvGoBlockSync, trace.EvGoBlockCond, trace.EvGoBlockGC:
	// TODO(hyangah): figure out why EvGoBlockGC should be here.
	// EvGoBlockGC indicates the goroutine blocks on GC assist, not
	// on synchronization primitives.
	default:
	continue
	}
	if ev.Link == nil \|\| ev.StkID == 0 \|\| len(ev.Stk) == 0 {
	continue
	}
	overlapping := pprofOverlappingDuration(gToIntervals, ev)
	if overlapping > 0 {
	rec := prof[ev.StkID]
	rec.stk = ev.Stk
	rec.n++
	rec.time += overlapping.Nanoseconds()
	prof[ev.StkID] = rec
	}
	}
	return buildProfile(prof).Write(w)
	}

	// computePprofSyscall generates syscall pprof-like profile (time spent blocked in syscalls).
	func computePprofSyscall(w io.Writer, gToIntervals map[uint64][]interval, events []*trace.Event) error {
	prof := make(map[uint64]Record)
	for _, ev := range events {
	if ev.Type != trace.EvGoSysCall \|\| ev.Link == nil \|\| ev.StkID == 0 \|\| len(ev.Stk) == 0 {
	continue
	}
	overlapping := pprofOverlappingDuration(gToIntervals, ev)
	if overlapping > 0 {
	rec := prof[ev.StkID]
	rec.stk = ev.Stk
	rec.n++
	rec.time += overlapping.Nanoseconds()
	prof[ev.StkID] = rec
	}
	}
	return buildProfile(prof).Write(w)
	}

	// computePprofSched generates scheduler latency pprof-like profile
	// (time between a goroutine become runnable and actually scheduled for execution).
	func computePprofSched(w io.Writer, gToIntervals map[uint64][]interval, events []*trace.Event) error {
	prof := make(map[uint64]Record)
	for _, ev := range events {
	if (ev.Type != trace.EvGoUnblock && ev.Type != trace.EvGoCreate) \|\|
	ev.Link == nil \|\| ev.StkID == 0 \|\| len(ev.Stk) == 0 {
	continue
	}
	overlapping := pprofOverlappingDuration(gToIntervals, ev)
	if overlapping > 0 {
	rec := prof[ev.StkID]
	rec.stk = ev.Stk
	rec.n++
	rec.time += overlapping.Nanoseconds()
	prof[ev.StkID] = rec
	}
	}
	return buildProfile(prof).Write(w)
	}

	// pprofOverlappingDuration returns the overlapping duration between
	// the time intervals in gToIntervals and the specified event.
	// If gToIntervals is nil, this simply returns the event's duration.
	func pprofOverlappingDuration(gToIntervals map[uint64][]interval, ev *trace.Event) time.Duration {
	if gToIntervals == nil { // No filtering.
	return time.Duration(ev.Link.Ts-ev.Ts) * time.Nanosecond
	}
	intervals := gToIntervals[ev.G]
	if len(intervals) == 0 {
	return 0
	}

	var overlapping time.Duration
	for _, i := range intervals {
	if o := overlappingDuration(i.begin, i.end, ev.Ts, ev.Link.Ts); o > 0 {
	overlapping += o
	}
	}
	return overlapping
	}

	// serveSVGProfile serves pprof-like profile generated by prof as svg.
	func serveSVGProfile(prof func(w io.Writer, r *http.Request) error) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {

	if r.FormValue("raw") != "" {
	w.Header().Set("Content-Type", "application/octet-stream")
	if err := prof(w, r); err != nil {
	w.Header().Set("Content-Type", "text/plain; charset=utf-8")
	w.Header().Set("X-Go-Pprof", "1")
	http.Error(w, fmt.Sprintf("failed to get profile: %v", err), http.StatusInternalServerError)
	return
	}
	return
	}

	blockf, err := os.CreateTemp("", "block")
	if err != nil {
	http.Error(w, fmt.Sprintf("failed to create temp file: %v", err), http.StatusInternalServerError)
	return
	}
	defer func() {
	blockf.Close()
	os.Remove(blockf.Name())
	}()
	blockb := bufio.NewWriter(blockf)
	if err := prof(blockb, r); err != nil {
	http.Error(w, fmt.Sprintf("failed to generate profile: %v", err), http.StatusInternalServerError)
	return
	}
	if err := blockb.Flush(); err != nil {
	http.Error(w, fmt.Sprintf("failed to flush temp file: %v", err), http.StatusInternalServerError)
	return
	}
	if err := blockf.Close(); err != nil {
	http.Error(w, fmt.Sprintf("failed to close temp file: %v", err), http.StatusInternalServerError)
	return
	}
	svgFilename := blockf.Name() + ".svg"
	if output, err := exec.Command(goCmd(), "tool", "pprof", "-svg", "-output", svgFilename, blockf.Name()).CombinedOutput(); err != nil {
	http.Error(w, fmt.Sprintf("failed to execute go tool pprof: %v\n%s", err, output), http.StatusInternalServerError)
	return
	}
	defer os.Remove(svgFilename)
	w.Header().Set("Content-Type", "image/svg+xml")
	http.ServeFile(w, r, svgFilename)
	}
	}

	func buildProfile(prof map[uint64]Record) *profile.Profile {
	p := &profile.Profile{
	PeriodType: &profile.ValueType{Type: "trace", Unit: "count"},
	Period: 1,
	SampleType: []*profile.ValueType{
	{Type: "contentions", Unit: "count"},
	{Type: "delay", Unit: "nanoseconds"},
	},
	}
	locs := make(map[uint64]*profile.Location)
	funcs := make(map[string]*profile.Function)
	for _, rec := range prof {
	var sloc []*profile.Location
	for _, frame := range rec.stk {
	loc := locs[frame.PC]
	if loc == nil {
	fn := funcs[frame.File+frame.Fn]
	if fn == nil {
	fn = &profile.Function{
	ID: uint64(len(p.Function) + 1),
	Name: frame.Fn,
	SystemName: frame.Fn,
	Filename: frame.File,
	}
	p.Function = append(p.Function, fn)
	funcs[frame.File+frame.Fn] = fn
	}
	loc = &profile.Location{
	ID: uint64(len(p.Location) + 1),
	Address: frame.PC,
	Line: []profile.Line{
	{
	Function: fn,
	Line: int64(frame.Line),
	},
	},
	}
	p.Location = append(p.Location, loc)
	locs[frame.PC] = loc
	}
	sloc = append(sloc, loc)
	}
	p.Sample = append(p.Sample, &profile.Sample{
	Value: []int64{int64(rec.n), rec.time},
	Location: sloc,
	})
	}
	return p
	}