Source: pprof.go in package runtime/pprof

Package pprof writes runtime profiling data in the format expected by the pprof visualization tool. Profiling a Go program The first step to profiling a Go program is to enable profiling. Support for profiling benchmarks built with the standard testing package is built into go test. For example, the following command runs benchmarks in the current directory and writes the CPU and memory profiles to cpu.prof and mem.prof: go test -cpuprofile cpu.prof -memprofile mem.prof -bench . To add equivalent profiling support to a standalone program, add code like the following to your main function: var cpuprofile = flag.String("cpuprofile", "", "write cpu profile to `file`") var memprofile = flag.String("memprofile", "", "write memory profile to `file`") func main() { flag.Parse() if *cpuprofile != "" { f, err := os.Create(*cpuprofile) if err != nil { log.Fatal("could not create CPU profile: ", err) } defer f.Close() // error handling omitted for example if err := pprof.StartCPUProfile(f); err != nil { log.Fatal("could not start CPU profile: ", err) } defer pprof.StopCPUProfile() } // ... rest of the program ... if *memprofile != "" { f, err := os.Create(*memprofile) if err != nil { log.Fatal("could not create memory profile: ", err) } defer f.Close() // error handling omitted for example runtime.GC() // get up-to-date statistics if err := pprof.WriteHeapProfile(f); err != nil { log.Fatal("could not write memory profile: ", err) } } } There is also a standard HTTP interface to profiling data. Adding the following line will install handlers under the /debug/pprof/ URL to download live profiles: import _ "net/http/pprof" See the net/http/pprof package for more details. Profiles can then be visualized with the pprof tool: go tool pprof cpu.prof There are many commands available from the pprof command line. Commonly used commands include "top", which prints a summary of the top program hot-spots, and "web", which opens an interactive graph of hot-spots and their call graphs. Use "help" for information on all pprof commands. For more information about pprof, see https://github.com/google/pprof/blob/master/doc/README.md.

package pprof

import (
	"bufio"
	"bytes"
	"fmt"
	"io"
	"runtime"
	"sort"
	"strings"
	"sync"
	"text/tabwriter"
	"time"
	"unsafe"
)

BUG(rsc): Profiles are only as good as the kernel support used to generate them. See https://golang.org/issue/13841 for details about known problems.

A Profile is a collection of stack traces showing the call sequences that led to instances of a particular event, such as allocation. Packages can create and maintain their own profiles; the most common use is for tracking resources that must be explicitly closed, such as files or network connections. A Profile's methods can be called from multiple goroutines simultaneously. Each Profile has a unique name. A few profiles are predefined: goroutine - stack traces of all current goroutines heap - a sampling of memory allocations of live objects allocs - a sampling of all past memory allocations threadcreate - stack traces that led to the creation of new OS threads block - stack traces that led to blocking on synchronization primitives mutex - stack traces of holders of contended mutexes These predefined profiles maintain themselves and panic on an explicit Add or Remove method call. The heap profile reports statistics as of the most recently completed garbage collection; it elides more recent allocation to avoid skewing the profile away from live data and toward garbage. If there has been no garbage collection at all, the heap profile reports all known allocations. This exception helps mainly in programs running without garbage collection enabled, usually for debugging purposes. The heap profile tracks both the allocation sites for all live objects in the application memory and for all objects allocated since the program start. Pprof's -inuse_space, -inuse_objects, -alloc_space, and -alloc_objects flags select which to display, defaulting to -inuse_space (live objects, scaled by size). The allocs profile is the same as the heap profile but changes the default pprof display to -alloc_space, the total number of bytes allocated since the program began (including garbage-collected bytes). The CPU profile is not available as a Profile. It has a special API, the StartCPUProfile and StopCPUProfile functions, because it streams output to a writer during profiling.

type Profile struct {
	name  string
	mu    sync.Mutex
	m     map[interface{}][]uintptr
	count func() int
	write func(io.Writer, int) error
}

profiles records all registered profiles.

var profiles struct {
	mu sync.Mutex
	m  map[string]*Profile
}

var goroutineProfile = &Profile{
	name:  "goroutine",
	count: countGoroutine,
	write: writeGoroutine,
}

var threadcreateProfile = &Profile{
	name:  "threadcreate",
	count: countThreadCreate,
	write: writeThreadCreate,
}

var heapProfile = &Profile{
	name:  "heap",
	count: countHeap,
	write: writeHeap,
}

var allocsProfile = &Profile{
	name:  "allocs",
	count: countHeap, // identical to heap profile
	write: writeAlloc,
}

var blockProfile = &Profile{
	name:  "block",
	count: countBlock,
	write: writeBlock,
}

var mutexProfile = &Profile{
	name:  "mutex",
	count: countMutex,
	write: writeMutex,
}

func lockProfiles() {
	profiles.mu.Lock()

Initial built-in profiles.

		profiles.m = map[string]*Profile{
			"goroutine":    goroutineProfile,
			"threadcreate": threadcreateProfile,
			"heap":         heapProfile,
			"allocs":       allocsProfile,
			"block":        blockProfile,
			"mutex":        mutexProfile,
		}
	}
}

func unlockProfiles() {
	profiles.mu.Unlock()
}

NewProfile creates a new profile with the given name. If a profile with that name already exists, NewProfile panics. The convention is to use a 'import/path.' prefix to create separate name spaces for each package. For compatibility with various tools that read pprof data, profile names should not contain spaces.

func NewProfile(name string) *Profile {
	lockProfiles()
	defer unlockProfiles()
	if name == "" {
		panic("pprof: NewProfile with empty name")
	}
	if profiles.m[name] != nil {
		panic("pprof: NewProfile name already in use: " + name)
	}
	p := &Profile{
		name: name,
		m:    map[interface{}][]uintptr{},
	}
	profiles.m[name] = p
	return p
}

Lookup returns the profile with the given name, or nil if no such profile exists.

func Lookup(name string) *Profile {
	lockProfiles()
	defer unlockProfiles()
	return profiles.m[name]
}

Profiles returns a slice of all the known profiles, sorted by name.

func Profiles() []*Profile {
	lockProfiles()
	defer unlockProfiles()

	all := make([]*Profile, 0, len(profiles.m))
	for _, p := range profiles.m {
		all = append(all, p)
	}

	sort.Slice(all, func(i, j int) bool { return all[i].name < all[j].name })
	return all
}

Name returns this profile's name, which can be passed to Lookup to reobtain the profile.

func (p *Profile) Name() string {
	return p.name
}

Count returns the number of execution stacks currently in the profile.

func (p *Profile) Count() int {
	p.mu.Lock()
	defer p.mu.Unlock()
	if p.count != nil {
		return p.count()
	}
	return len(p.m)
}

Add adds the current execution stack to the profile, associated with value. Add stores value in an internal map, so value must be suitable for use as a map key and will not be garbage collected until the corresponding call to Remove. Add panics if the profile already contains a stack for value. The skip parameter has the same meaning as runtime.Caller's skip and controls where the stack trace begins. Passing skip=0 begins the trace in the function calling Add. For example, given this execution stack: Add called from rpc.NewClient called from mypkg.Run called from main.main Passing skip=0 begins the stack trace at the call to Add inside rpc.NewClient. Passing skip=1 begins the stack trace at the call to NewClient inside mypkg.Run.

func (p *Profile) Add(value interface{}, skip int) {
	if p.name == "" {
		panic("pprof: use of uninitialized Profile")
	}
	if p.write != nil {
		panic("pprof: Add called on built-in Profile " + p.name)
	}

	stk := make([]uintptr, 32)
	n := runtime.Callers(skip+1, stk[:])
	stk = stk[:n]

The value for skip is too large, and there's no stack trace to record.

		stk = []uintptr{funcPC(lostProfileEvent)}
	}

	p.mu.Lock()
	defer p.mu.Unlock()
	if p.m[value] != nil {
		panic("pprof: Profile.Add of duplicate value")
	}
	p.m[value] = stk
}

Remove removes the execution stack associated with value from the profile. It is a no-op if the value is not in the profile.

func (p *Profile) Remove(value interface{}) {
	p.mu.Lock()
	defer p.mu.Unlock()
	delete(p.m, value)
}

WriteTo writes a pprof-formatted snapshot of the profile to w. If a write to w returns an error, WriteTo returns that error. Otherwise, WriteTo returns nil. The debug parameter enables additional output. Passing debug=0 writes the gzip-compressed protocol buffer described in https://github.com/google/pprof/tree/master/proto#overview. Passing debug=1 writes the legacy text format with comments translating addresses to function names and line numbers, so that a programmer can read the profile without tools. The predefined profiles may assign meaning to other debug values; for example, when printing the "goroutine" profile, debug=2 means to print the goroutine stacks in the same form that a Go program uses when dying due to an unrecovered panic.

func (p *Profile) WriteTo(w io.Writer, debug int) error {
	if p.name == "" {
		panic("pprof: use of zero Profile")
	}
	if p.write != nil {
		return p.write(w, debug)
	}

Obtain consistent snapshot under lock; then process without lock.

	p.mu.Lock()
	all := make([][]uintptr, 0, len(p.m))
	for _, stk := range p.m {
		all = append(all, stk)
	}
	p.mu.Unlock()

Map order is non-deterministic; make output deterministic.

	sort.Slice(all, func(i, j int) bool {
		t, u := all[i], all[j]
		for k := 0; k < len(t) && k < len(u); k++ {
			if t[k] != u[k] {
				return t[k] < u[k]
			}
		}
		return len(t) < len(u)
	})

	return printCountProfile(w, debug, p.name, stackProfile(all))
}

type stackProfile [][]uintptr

func (x stackProfile) Len() int              { return len(x) }
func (x stackProfile) Stack(i int) []uintptr { return x[i] }
func (x stackProfile) Label(i int) *labelMap { return nil }

A countProfile is a set of stack traces to be printed as counts grouped by stack trace. There are multiple implementations: all that matters is that we can find out how many traces there are and obtain each trace in turn.

type countProfile interface {
	Len() int
	Stack(i int) []uintptr
	Label(i int) *labelMap
}

printCountCycleProfile outputs block profile records (for block or mutex profiles) as the pprof-proto format output. Translations from cycle count to time duration are done because The proto expects count and time (nanoseconds) instead of count and the number of cycles for block, contention profiles. Possible 'scaler' functions are scaleBlockProfile and scaleMutexProfile.

Output profile in protobuf form.

	b := newProfileBuilder(w)
	b.pbValueType(tagProfile_PeriodType, countName, "count")
	b.pb.int64Opt(tagProfile_Period, 1)
	b.pbValueType(tagProfile_SampleType, countName, "count")
	b.pbValueType(tagProfile_SampleType, cycleName, "nanoseconds")

	cpuGHz := float64(runtime_cyclesPerSecond()) / 1e9

	values := []int64{0, 0}
	var locs []uint64
	for _, r := range records {
		count, nanosec := scaler(r.Count, float64(r.Cycles)/cpuGHz)
		values[0] = count

For count profiles, all stack addresses are return PCs, which is what appendLocsForStack expects.

		locs = b.appendLocsForStack(locs[:0], r.Stack())
		b.pbSample(values, locs, nil)
	}
	b.build()
	return nil
}

printCountProfile prints a countProfile at the specified debug level. The profile will be in compressed proto format unless debug is nonzero.

Build count of each stack.

	var buf bytes.Buffer
	key := func(stk []uintptr, lbls *labelMap) string {
		buf.Reset()
		fmt.Fprintf(&buf, "@")
		for _, pc := range stk {
			fmt.Fprintf(&buf, " %#x", pc)
		}
		if lbls != nil {
			buf.WriteString("\n# labels: ")
			buf.WriteString(lbls.String())
		}
		return buf.String()
	}
	count := map[string]int{}
	index := map[string]int{}
	var keys []string
	n := p.Len()
	for i := 0; i < n; i++ {
		k := key(p.Stack(i), p.Label(i))
		if count[k] == 0 {
			index[k] = i
			keys = append(keys, k)
		}
		count[k]++
	}

	sort.Sort(&keysByCount{keys, count})

Print debug profile in legacy format

		tw := tabwriter.NewWriter(w, 1, 8, 1, '\t', 0)
		fmt.Fprintf(tw, "%s profile: total %d\n", name, p.Len())
		for _, k := range keys {
			fmt.Fprintf(tw, "%d %s\n", count[k], k)
			printStackRecord(tw, p.Stack(index[k]), false)
		}
		return tw.Flush()
	}

Output profile in protobuf form.

	b := newProfileBuilder(w)
	b.pbValueType(tagProfile_PeriodType, name, "count")
	b.pb.int64Opt(tagProfile_Period, 1)
	b.pbValueType(tagProfile_SampleType, name, "count")

	values := []int64{0}
	var locs []uint64
	for _, k := range keys {

For count profiles, all stack addresses are return PCs, which is what appendLocsForStack expects.

		locs = b.appendLocsForStack(locs[:0], p.Stack(index[k]))
		idx := index[k]
		var labels func()
		if p.Label(idx) != nil {
			labels = func() {
				for k, v := range *p.Label(idx) {
					b.pbLabel(tagSample_Label, k, v, 0)
				}
			}
		}
		b.pbSample(values, locs, labels)
	}
	b.build()
	return nil
}

keysByCount sorts keys with higher counts first, breaking ties by key string order.

type keysByCount struct {
	keys  []string
	count map[string]int
}

func (x *keysByCount) Len() int      { return len(x.keys) }
func (x *keysByCount) Swap(i, j int) { x.keys[i], x.keys[j] = x.keys[j], x.keys[i] }
func (x *keysByCount) Less(i, j int) bool {
	ki, kj := x.keys[i], x.keys[j]
	ci, cj := x.count[ki], x.count[kj]
	if ci != cj {
		return ci > cj
	}
	return ki < kj
}

printStackRecord prints the function + source line information for a single stack trace.

func printStackRecord(w io.Writer, stk []uintptr, allFrames bool) {
	show := allFrames
	frames := runtime.CallersFrames(stk)
	for {
		frame, more := frames.Next()
		name := frame.Function
		if name == "" {
			show = true
			fmt.Fprintf(w, "#\t%#x\n", frame.PC)

Hide runtime.goexit and any runtime functions at the beginning. This is useful mainly for allocation traces.

			show = true
			fmt.Fprintf(w, "#\t%#x\t%s+%#x\t%s:%d\n", frame.PC, name, frame.PC-frame.Entry, frame.File, frame.Line)
		}
		if !more {
			break
		}
	}

We didn't print anything; do it again, and this time include runtime functions.

		printStackRecord(w, stk, true)
		return
	}
	fmt.Fprintf(w, "\n")
}

Interface to system profiles.

WriteHeapProfile is shorthand for Lookup("heap").WriteTo(w, 0). It is preserved for backwards compatibility.

func WriteHeapProfile(w io.Writer) error {
	return writeHeap(w, 0)
}

countHeap returns the number of records in the heap profile.

func countHeap() int {
	n, _ := runtime.MemProfile(nil, true)
	return n
}

writeHeap writes the current runtime heap profile to w.

func writeHeap(w io.Writer, debug int) error {
	return writeHeapInternal(w, debug, "")
}

writeAlloc writes the current runtime heap profile to w with the total allocation space as the default sample type.

func writeAlloc(w io.Writer, debug int) error {
	return writeHeapInternal(w, debug, "alloc_space")
}

func writeHeapInternal(w io.Writer, debug int, defaultSampleType string) error {
	var memStats *runtime.MemStats

Read mem stats first, so that our other allocations do not appear in the statistics.

		memStats = new(runtime.MemStats)
		runtime.ReadMemStats(memStats)
	}

Find out how many records there are (MemProfile(nil, true)), allocate that many records, and get the data. There's a race—more records might be added between the two calls—so allocate a few extra records for safety and also try again if we're very unlucky. The loop should only execute one iteration in the common case.

	var p []runtime.MemProfileRecord
	n, ok := runtime.MemProfile(nil, true)

Allocate room for a slightly bigger profile, in case a few more entries have been added since the call to MemProfile.

		p = make([]runtime.MemProfileRecord, n+50)
		n, ok = runtime.MemProfile(p, true)
		if ok {
			p = p[0:n]
			break

Profile grew; try again.

	}

	if debug == 0 {
		return writeHeapProto(w, p, int64(runtime.MemProfileRate), defaultSampleType)
	}

	sort.Slice(p, func(i, j int) bool { return p[i].InUseBytes() > p[j].InUseBytes() })

	b := bufio.NewWriter(w)
	tw := tabwriter.NewWriter(b, 1, 8, 1, '\t', 0)
	w = tw

	var total runtime.MemProfileRecord
	for i := range p {
		r := &p[i]
		total.AllocBytes += r.AllocBytes
		total.AllocObjects += r.AllocObjects
		total.FreeBytes += r.FreeBytes
		total.FreeObjects += r.FreeObjects
	}

Technically the rate is MemProfileRate not 2*MemProfileRate, but early versions of the C++ heap profiler reported 2*MemProfileRate, so that's what pprof has come to expect.

	fmt.Fprintf(w, "heap profile: %d: %d [%d: %d] @ heap/%d\n",
		total.InUseObjects(), total.InUseBytes(),
		total.AllocObjects, total.AllocBytes,
		2*runtime.MemProfileRate)

	for i := range p {
		r := &p[i]
		fmt.Fprintf(w, "%d: %d [%d: %d] @",
			r.InUseObjects(), r.InUseBytes(),
			r.AllocObjects, r.AllocBytes)
		for _, pc := range r.Stack() {
			fmt.Fprintf(w, " %#x", pc)
		}
		fmt.Fprintf(w, "\n")
		printStackRecord(w, r.Stack(), false)
	}

Print memstats information too. Pprof will ignore, but useful for people

	s := memStats
	fmt.Fprintf(w, "\n# runtime.MemStats\n")
	fmt.Fprintf(w, "# Alloc = %d\n", s.Alloc)
	fmt.Fprintf(w, "# TotalAlloc = %d\n", s.TotalAlloc)
	fmt.Fprintf(w, "# Sys = %d\n", s.Sys)
	fmt.Fprintf(w, "# Lookups = %d\n", s.Lookups)
	fmt.Fprintf(w, "# Mallocs = %d\n", s.Mallocs)
	fmt.Fprintf(w, "# Frees = %d\n", s.Frees)

	fmt.Fprintf(w, "# HeapAlloc = %d\n", s.HeapAlloc)
	fmt.Fprintf(w, "# HeapSys = %d\n", s.HeapSys)
	fmt.Fprintf(w, "# HeapIdle = %d\n", s.HeapIdle)
	fmt.Fprintf(w, "# HeapInuse = %d\n", s.HeapInuse)
	fmt.Fprintf(w, "# HeapReleased = %d\n", s.HeapReleased)
	fmt.Fprintf(w, "# HeapObjects = %d\n", s.HeapObjects)

	fmt.Fprintf(w, "# Stack = %d / %d\n", s.StackInuse, s.StackSys)
	fmt.Fprintf(w, "# MSpan = %d / %d\n", s.MSpanInuse, s.MSpanSys)
	fmt.Fprintf(w, "# MCache = %d / %d\n", s.MCacheInuse, s.MCacheSys)
	fmt.Fprintf(w, "# BuckHashSys = %d\n", s.BuckHashSys)
	fmt.Fprintf(w, "# GCSys = %d\n", s.GCSys)
	fmt.Fprintf(w, "# OtherSys = %d\n", s.OtherSys)

	fmt.Fprintf(w, "# NextGC = %d\n", s.NextGC)
	fmt.Fprintf(w, "# LastGC = %d\n", s.LastGC)
	fmt.Fprintf(w, "# PauseNs = %d\n", s.PauseNs)
	fmt.Fprintf(w, "# PauseEnd = %d\n", s.PauseEnd)
	fmt.Fprintf(w, "# NumGC = %d\n", s.NumGC)
	fmt.Fprintf(w, "# NumForcedGC = %d\n", s.NumForcedGC)
	fmt.Fprintf(w, "# GCCPUFraction = %v\n", s.GCCPUFraction)
	fmt.Fprintf(w, "# DebugGC = %v\n", s.DebugGC)

Also flush out MaxRSS on supported platforms.

	addMaxRSS(w)

	tw.Flush()
	return b.Flush()
}

countThreadCreate returns the size of the current ThreadCreateProfile.

func countThreadCreate() int {
	n, _ := runtime.ThreadCreateProfile(nil)
	return n
}

writeThreadCreate writes the current runtime ThreadCreateProfile to w.

Until https://golang.org/issues/6104 is addressed, wrap ThreadCreateProfile because there's no point in tracking labels when we don't get any stack-traces.

	return writeRuntimeProfile(w, debug, "threadcreate", func(p []runtime.StackRecord, _ []unsafe.Pointer) (n int, ok bool) {
		return runtime.ThreadCreateProfile(p)
	})
}

countGoroutine returns the number of goroutines.

func countGoroutine() int {
	return runtime.NumGoroutine()
}

runtime_goroutineProfileWithLabels is defined in runtime/mprof.go

func runtime_goroutineProfileWithLabels(p []runtime.StackRecord, labels []unsafe.Pointer) (n int, ok bool)

writeGoroutine writes the current runtime GoroutineProfile to w.

func writeGoroutine(w io.Writer, debug int) error {
	if debug >= 2 {
		return writeGoroutineStacks(w)
	}
	return writeRuntimeProfile(w, debug, "goroutine", runtime_goroutineProfileWithLabels)
}

We don't know how big the buffer needs to be to collect all the goroutines. Start with 1 MB and try a few times, doubling each time. Give up and use a truncated trace if 64 MB is not enough.

	buf := make([]byte, 1<<20)
	for i := 0; ; i++ {
		n := runtime.Stack(buf, true)
		if n < len(buf) {
			buf = buf[:n]
			break
		}

Filled 64 MB - stop there.

			break
		}
		buf = make([]byte, 2*len(buf))
	}
	_, err := w.Write(buf)
	return err
}

Find out how many records there are (fetch(nil)), allocate that many records, and get the data. There's a race—more records might be added between the two calls—so allocate a few extra records for safety and also try again if we're very unlucky. The loop should only execute one iteration in the common case.

	var p []runtime.StackRecord
	var labels []unsafe.Pointer
	n, ok := fetch(nil, nil)

Allocate room for a slightly bigger profile, in case a few more entries have been added since the call to ThreadProfile.

		p = make([]runtime.StackRecord, n+10)
		labels = make([]unsafe.Pointer, n+10)
		n, ok = fetch(p, labels)
		if ok {
			p = p[0:n]
			break

Profile grew; try again.

	}

	return printCountProfile(w, debug, name, &runtimeProfile{p, labels})
}

type runtimeProfile struct {
	stk    []runtime.StackRecord
	labels []unsafe.Pointer
}

func (p *runtimeProfile) Len() int              { return len(p.stk) }
func (p *runtimeProfile) Stack(i int) []uintptr { return p.stk[i].Stack() }
func (p *runtimeProfile) Label(i int) *labelMap { return (*labelMap)(p.labels[i]) }

var cpu struct {
	sync.Mutex
	profiling bool
	done      chan bool
}

StartCPUProfile enables CPU profiling for the current process. While profiling, the profile will be buffered and written to w. StartCPUProfile returns an error if profiling is already enabled. On Unix-like systems, StartCPUProfile does not work by default for Go code built with -buildmode=c-archive or -buildmode=c-shared. StartCPUProfile relies on the SIGPROF signal, but that signal will be delivered to the main program's SIGPROF signal handler (if any) not to the one used by Go. To make it work, call os/signal.Notify for syscall.SIGPROF, but note that doing so may break any profiling being done by the main program.

The runtime routines allow a variable profiling rate, but in practice operating systems cannot trigger signals at more than about 500 Hz, and our processing of the signal is not cheap (mostly getting the stack trace). 100 Hz is a reasonable choice: it is frequent enough to produce useful data, rare enough not to bog down the system, and a nice round number to make it easy to convert sample counts to seconds. Instead of requiring each client to specify the frequency, we hard code it.

	const hz = 100

	cpu.Lock()
	defer cpu.Unlock()
	if cpu.done == nil {
		cpu.done = make(chan bool)

Double-check.

	if cpu.profiling {
		return fmt.Errorf("cpu profiling already in use")
	}
	cpu.profiling = true
	runtime.SetCPUProfileRate(hz)
	go profileWriter(w)
	return nil
}

readProfile, provided by the runtime, returns the next chunk of binary CPU profiling stack trace data, blocking until data is available. If profiling is turned off and all the profile data accumulated while it was on has been returned, readProfile returns eof=true. The caller must save the returned data and tags before calling readProfile again.

func readProfile() (data []uint64, tags []unsafe.Pointer, eof bool)

func profileWriter(w io.Writer) {
	b := newProfileBuilder(w)
	var err error
	for {
		time.Sleep(100 * time.Millisecond)
		data, tags, eof := readProfile()
		if e := b.addCPUData(data, tags); e != nil && err == nil {
			err = e
		}
		if eof {
			break
		}
	}

The runtime should never produce an invalid or truncated profile. It drops records that can't fit into its log buffers.

		panic("runtime/pprof: converting profile: " + err.Error())
	}
	b.build()
	cpu.done <- true
}

StopCPUProfile stops the current CPU profile, if any. StopCPUProfile only returns after all the writes for the profile have completed.

func StopCPUProfile() {
	cpu.Lock()
	defer cpu.Unlock()

	if !cpu.profiling {
		return
	}
	cpu.profiling = false
	runtime.SetCPUProfileRate(0)
	<-cpu.done
}

countBlock returns the number of records in the blocking profile.

func countBlock() int {
	n, _ := runtime.BlockProfile(nil)
	return n
}

countMutex returns the number of records in the mutex profile.

func countMutex() int {
	n, _ := runtime.MutexProfile(nil)
	return n
}

writeBlock writes the current blocking profile to w.

func writeBlock(w io.Writer, debug int) error {
	var p []runtime.BlockProfileRecord
	n, ok := runtime.BlockProfile(nil)
	for {
		p = make([]runtime.BlockProfileRecord, n+50)
		n, ok = runtime.BlockProfile(p)
		if ok {
			p = p[:n]
			break
		}
	}

	sort.Slice(p, func(i, j int) bool { return p[i].Cycles > p[j].Cycles })

	if debug <= 0 {
		return printCountCycleProfile(w, "contentions", "delay", scaleBlockProfile, p)
	}

	b := bufio.NewWriter(w)
	tw := tabwriter.NewWriter(w, 1, 8, 1, '\t', 0)
	w = tw

	fmt.Fprintf(w, "--- contention:\n")
	fmt.Fprintf(w, "cycles/second=%v\n", runtime_cyclesPerSecond())
	for i := range p {
		r := &p[i]
		fmt.Fprintf(w, "%v %v @", r.Cycles, r.Count)
		for _, pc := range r.Stack() {
			fmt.Fprintf(w, " %#x", pc)
		}
		fmt.Fprint(w, "\n")
		if debug > 0 {
			printStackRecord(w, r.Stack(), true)
		}
	}

	if tw != nil {
		tw.Flush()
	}
	return b.Flush()
}

Do nothing. The current way of block profile sampling makes it hard to compute the unsampled number. The legacy block profile parse doesn't attempt to scale or unsample.

	return cnt, ns
}

writeMutex writes the current mutex profile to w.

TODO(pjw): too much common code with writeBlock. FIX!

	var p []runtime.BlockProfileRecord
	n, ok := runtime.MutexProfile(nil)
	for {
		p = make([]runtime.BlockProfileRecord, n+50)
		n, ok = runtime.MutexProfile(p)
		if ok {
			p = p[:n]
			break
		}
	}

	sort.Slice(p, func(i, j int) bool { return p[i].Cycles > p[j].Cycles })

	if debug <= 0 {
		return printCountCycleProfile(w, "contentions", "delay", scaleMutexProfile, p)
	}

	b := bufio.NewWriter(w)
	tw := tabwriter.NewWriter(w, 1, 8, 1, '\t', 0)
	w = tw

	fmt.Fprintf(w, "--- mutex:\n")
	fmt.Fprintf(w, "cycles/second=%v\n", runtime_cyclesPerSecond())
	fmt.Fprintf(w, "sampling period=%d\n", runtime.SetMutexProfileFraction(-1))
	for i := range p {
		r := &p[i]
		fmt.Fprintf(w, "%v %v @", r.Cycles, r.Count)
		for _, pc := range r.Stack() {
			fmt.Fprintf(w, " %#x", pc)
		}
		fmt.Fprint(w, "\n")
		if debug > 0 {
			printStackRecord(w, r.Stack(), true)
		}
	}

	if tw != nil {
		tw.Flush()
	}
	return b.Flush()
}

func scaleMutexProfile(cnt int64, ns float64) (int64, float64) {
	period := runtime.SetMutexProfileFraction(-1)
	return cnt * int64(period), ns * float64(period)
}