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Source file src/runtime/pprof/pprof.go

Documentation: runtime/pprof

     1  // Copyright 2010 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  // Package pprof writes runtime profiling data in the format expected
     6  // by the pprof visualization tool.
     7  //
     8  // Profiling a Go program
     9  //
    10  // The first step to profiling a Go program is to enable profiling.
    11  // Support for profiling benchmarks built with the standard testing
    12  // package is built into go test. For example, the following command
    13  // runs benchmarks in the current directory and writes the CPU and
    14  // memory profiles to cpu.prof and mem.prof:
    15  //
    16  //     go test -cpuprofile cpu.prof -memprofile mem.prof -bench .
    17  //
    18  // To add equivalent profiling support to a standalone program, add
    19  // code like the following to your main function:
    20  //
    21  //    var cpuprofile = flag.String("cpuprofile", "", "write cpu profile to `file`")
    22  //    var memprofile = flag.String("memprofile", "", "write memory profile to `file`")
    23  //
    24  //    func main() {
    25  //        flag.Parse()
    26  //        if *cpuprofile != "" {
    27  //            f, err := os.Create(*cpuprofile)
    28  //            if err != nil {
    29  //                log.Fatal("could not create CPU profile: ", err)
    30  //            }
    31  //            defer f.Close() // error handling omitted for example
    32  //            if err := pprof.StartCPUProfile(f); err != nil {
    33  //                log.Fatal("could not start CPU profile: ", err)
    34  //            }
    35  //            defer pprof.StopCPUProfile()
    36  //        }
    37  //
    38  //        // ... rest of the program ...
    39  //
    40  //        if *memprofile != "" {
    41  //            f, err := os.Create(*memprofile)
    42  //            if err != nil {
    43  //                log.Fatal("could not create memory profile: ", err)
    44  //            }
    45  //            defer f.Close() // error handling omitted for example
    46  //            runtime.GC() // get up-to-date statistics
    47  //            if err := pprof.WriteHeapProfile(f); err != nil {
    48  //                log.Fatal("could not write memory profile: ", err)
    49  //            }
    50  //        }
    51  //    }
    52  //
    53  // There is also a standard HTTP interface to profiling data. Adding
    54  // the following line will install handlers under the /debug/pprof/
    55  // URL to download live profiles:
    56  //
    57  //    import _ "net/http/pprof"
    58  //
    59  // See the net/http/pprof package for more details.
    60  //
    61  // Profiles can then be visualized with the pprof tool:
    62  //
    63  //    go tool pprof cpu.prof
    64  //
    65  // There are many commands available from the pprof command line.
    66  // Commonly used commands include "top", which prints a summary of the
    67  // top program hot-spots, and "web", which opens an interactive graph
    68  // of hot-spots and their call graphs. Use "help" for information on
    69  // all pprof commands.
    70  //
    71  // For more information about pprof, see
    72  // https://github.com/google/pprof/blob/master/doc/README.md.
    73  package pprof
    74  
    75  import (
    76  	"bufio"
    77  	"bytes"
    78  	"fmt"
    79  	"io"
    80  	"runtime"
    81  	"sort"
    82  	"strings"
    83  	"sync"
    84  	"text/tabwriter"
    85  	"time"
    86  	"unsafe"
    87  )
    88  
    89  // BUG(rsc): Profiles are only as good as the kernel support used to generate them.
    90  // See https://golang.org/issue/13841 for details about known problems.
    91  
    92  // A Profile is a collection of stack traces showing the call sequences
    93  // that led to instances of a particular event, such as allocation.
    94  // Packages can create and maintain their own profiles; the most common
    95  // use is for tracking resources that must be explicitly closed, such as files
    96  // or network connections.
    97  //
    98  // A Profile's methods can be called from multiple goroutines simultaneously.
    99  //
   100  // Each Profile has a unique name. A few profiles are predefined:
   101  //
   102  //	goroutine    - stack traces of all current goroutines
   103  //	heap         - a sampling of memory allocations of live objects
   104  //	allocs       - a sampling of all past memory allocations
   105  //	threadcreate - stack traces that led to the creation of new OS threads
   106  //	block        - stack traces that led to blocking on synchronization primitives
   107  //	mutex        - stack traces of holders of contended mutexes
   108  //
   109  // These predefined profiles maintain themselves and panic on an explicit
   110  // Add or Remove method call.
   111  //
   112  // The heap profile reports statistics as of the most recently completed
   113  // garbage collection; it elides more recent allocation to avoid skewing
   114  // the profile away from live data and toward garbage.
   115  // If there has been no garbage collection at all, the heap profile reports
   116  // all known allocations. This exception helps mainly in programs running
   117  // without garbage collection enabled, usually for debugging purposes.
   118  //
   119  // The heap profile tracks both the allocation sites for all live objects in
   120  // the application memory and for all objects allocated since the program start.
   121  // Pprof's -inuse_space, -inuse_objects, -alloc_space, and -alloc_objects
   122  // flags select which to display, defaulting to -inuse_space (live objects,
   123  // scaled by size).
   124  //
   125  // The allocs profile is the same as the heap profile but changes the default
   126  // pprof display to -alloc_space, the total number of bytes allocated since
   127  // the program began (including garbage-collected bytes).
   128  //
   129  // The CPU profile is not available as a Profile. It has a special API,
   130  // the StartCPUProfile and StopCPUProfile functions, because it streams
   131  // output to a writer during profiling.
   132  //
   133  type Profile struct {
   134  	name  string
   135  	mu    sync.Mutex
   136  	m     map[interface{}][]uintptr
   137  	count func() int
   138  	write func(io.Writer, int) error
   139  }
   140  
   141  // profiles records all registered profiles.
   142  var profiles struct {
   143  	mu sync.Mutex
   144  	m  map[string]*Profile
   145  }
   146  
   147  var goroutineProfile = &Profile{
   148  	name:  "goroutine",
   149  	count: countGoroutine,
   150  	write: writeGoroutine,
   151  }
   152  
   153  var threadcreateProfile = &Profile{
   154  	name:  "threadcreate",
   155  	count: countThreadCreate,
   156  	write: writeThreadCreate,
   157  }
   158  
   159  var heapProfile = &Profile{
   160  	name:  "heap",
   161  	count: countHeap,
   162  	write: writeHeap,
   163  }
   164  
   165  var allocsProfile = &Profile{
   166  	name:  "allocs",
   167  	count: countHeap, // identical to heap profile
   168  	write: writeAlloc,
   169  }
   170  
   171  var blockProfile = &Profile{
   172  	name:  "block",
   173  	count: countBlock,
   174  	write: writeBlock,
   175  }
   176  
   177  var mutexProfile = &Profile{
   178  	name:  "mutex",
   179  	count: countMutex,
   180  	write: writeMutex,
   181  }
   182  
   183  func lockProfiles() {
   184  	profiles.mu.Lock()
   185  	if profiles.m == nil {
   186  		// Initial built-in profiles.
   187  		profiles.m = map[string]*Profile{
   188  			"goroutine":    goroutineProfile,
   189  			"threadcreate": threadcreateProfile,
   190  			"heap":         heapProfile,
   191  			"allocs":       allocsProfile,
   192  			"block":        blockProfile,
   193  			"mutex":        mutexProfile,
   194  		}
   195  	}
   196  }
   197  
   198  func unlockProfiles() {
   199  	profiles.mu.Unlock()
   200  }
   201  
   202  // NewProfile creates a new profile with the given name.
   203  // If a profile with that name already exists, NewProfile panics.
   204  // The convention is to use a 'import/path.' prefix to create
   205  // separate name spaces for each package.
   206  // For compatibility with various tools that read pprof data,
   207  // profile names should not contain spaces.
   208  func NewProfile(name string) *Profile {
   209  	lockProfiles()
   210  	defer unlockProfiles()
   211  	if name == "" {
   212  		panic("pprof: NewProfile with empty name")
   213  	}
   214  	if profiles.m[name] != nil {
   215  		panic("pprof: NewProfile name already in use: " + name)
   216  	}
   217  	p := &Profile{
   218  		name: name,
   219  		m:    map[interface{}][]uintptr{},
   220  	}
   221  	profiles.m[name] = p
   222  	return p
   223  }
   224  
   225  // Lookup returns the profile with the given name, or nil if no such profile exists.
   226  func Lookup(name string) *Profile {
   227  	lockProfiles()
   228  	defer unlockProfiles()
   229  	return profiles.m[name]
   230  }
   231  
   232  // Profiles returns a slice of all the known profiles, sorted by name.
   233  func Profiles() []*Profile {
   234  	lockProfiles()
   235  	defer unlockProfiles()
   236  
   237  	all := make([]*Profile, 0, len(profiles.m))
   238  	for _, p := range profiles.m {
   239  		all = append(all, p)
   240  	}
   241  
   242  	sort.Slice(all, func(i, j int) bool { return all[i].name < all[j].name })
   243  	return all
   244  }
   245  
   246  // Name returns this profile's name, which can be passed to Lookup to reobtain the profile.
   247  func (p *Profile) Name() string {
   248  	return p.name
   249  }
   250  
   251  // Count returns the number of execution stacks currently in the profile.
   252  func (p *Profile) Count() int {
   253  	p.mu.Lock()
   254  	defer p.mu.Unlock()
   255  	if p.count != nil {
   256  		return p.count()
   257  	}
   258  	return len(p.m)
   259  }
   260  
   261  // Add adds the current execution stack to the profile, associated with value.
   262  // Add stores value in an internal map, so value must be suitable for use as
   263  // a map key and will not be garbage collected until the corresponding
   264  // call to Remove. Add panics if the profile already contains a stack for value.
   265  //
   266  // The skip parameter has the same meaning as runtime.Caller's skip
   267  // and controls where the stack trace begins. Passing skip=0 begins the
   268  // trace in the function calling Add. For example, given this
   269  // execution stack:
   270  //
   271  //	Add
   272  //	called from rpc.NewClient
   273  //	called from mypkg.Run
   274  //	called from main.main
   275  //
   276  // Passing skip=0 begins the stack trace at the call to Add inside rpc.NewClient.
   277  // Passing skip=1 begins the stack trace at the call to NewClient inside mypkg.Run.
   278  //
   279  func (p *Profile) Add(value interface{}, skip int) {
   280  	if p.name == "" {
   281  		panic("pprof: use of uninitialized Profile")
   282  	}
   283  	if p.write != nil {
   284  		panic("pprof: Add called on built-in Profile " + p.name)
   285  	}
   286  
   287  	stk := make([]uintptr, 32)
   288  	n := runtime.Callers(skip+1, stk[:])
   289  	stk = stk[:n]
   290  	if len(stk) == 0 {
   291  		// The value for skip is too large, and there's no stack trace to record.
   292  		stk = []uintptr{funcPC(lostProfileEvent)}
   293  	}
   294  
   295  	p.mu.Lock()
   296  	defer p.mu.Unlock()
   297  	if p.m[value] != nil {
   298  		panic("pprof: Profile.Add of duplicate value")
   299  	}
   300  	p.m[value] = stk
   301  }
   302  
   303  // Remove removes the execution stack associated with value from the profile.
   304  // It is a no-op if the value is not in the profile.
   305  func (p *Profile) Remove(value interface{}) {
   306  	p.mu.Lock()
   307  	defer p.mu.Unlock()
   308  	delete(p.m, value)
   309  }
   310  
   311  // WriteTo writes a pprof-formatted snapshot of the profile to w.
   312  // If a write to w returns an error, WriteTo returns that error.
   313  // Otherwise, WriteTo returns nil.
   314  //
   315  // The debug parameter enables additional output.
   316  // Passing debug=0 writes the gzip-compressed protocol buffer described
   317  // in https://github.com/google/pprof/tree/master/proto#overview.
   318  // Passing debug=1 writes the legacy text format with comments
   319  // translating addresses to function names and line numbers, so that a
   320  // programmer can read the profile without tools.
   321  //
   322  // The predefined profiles may assign meaning to other debug values;
   323  // for example, when printing the "goroutine" profile, debug=2 means to
   324  // print the goroutine stacks in the same form that a Go program uses
   325  // when dying due to an unrecovered panic.
   326  func (p *Profile) WriteTo(w io.Writer, debug int) error {
   327  	if p.name == "" {
   328  		panic("pprof: use of zero Profile")
   329  	}
   330  	if p.write != nil {
   331  		return p.write(w, debug)
   332  	}
   333  
   334  	// Obtain consistent snapshot under lock; then process without lock.
   335  	p.mu.Lock()
   336  	all := make([][]uintptr, 0, len(p.m))
   337  	for _, stk := range p.m {
   338  		all = append(all, stk)
   339  	}
   340  	p.mu.Unlock()
   341  
   342  	// Map order is non-deterministic; make output deterministic.
   343  	sort.Slice(all, func(i, j int) bool {
   344  		t, u := all[i], all[j]
   345  		for k := 0; k < len(t) && k < len(u); k++ {
   346  			if t[k] != u[k] {
   347  				return t[k] < u[k]
   348  			}
   349  		}
   350  		return len(t) < len(u)
   351  	})
   352  
   353  	return printCountProfile(w, debug, p.name, stackProfile(all))
   354  }
   355  
   356  type stackProfile [][]uintptr
   357  
   358  func (x stackProfile) Len() int              { return len(x) }
   359  func (x stackProfile) Stack(i int) []uintptr { return x[i] }
   360  func (x stackProfile) Label(i int) *labelMap { return nil }
   361  
   362  // A countProfile is a set of stack traces to be printed as counts
   363  // grouped by stack trace. There are multiple implementations:
   364  // all that matters is that we can find out how many traces there are
   365  // and obtain each trace in turn.
   366  type countProfile interface {
   367  	Len() int
   368  	Stack(i int) []uintptr
   369  	Label(i int) *labelMap
   370  }
   371  
   372  // printCountCycleProfile outputs block profile records (for block or mutex profiles)
   373  // as the pprof-proto format output. Translations from cycle count to time duration
   374  // are done because The proto expects count and time (nanoseconds) instead of count
   375  // and the number of cycles for block, contention profiles.
   376  // Possible 'scaler' functions are scaleBlockProfile and scaleMutexProfile.
   377  func printCountCycleProfile(w io.Writer, countName, cycleName string, scaler func(int64, float64) (int64, float64), records []runtime.BlockProfileRecord) error {
   378  	// Output profile in protobuf form.
   379  	b := newProfileBuilder(w)
   380  	b.pbValueType(tagProfile_PeriodType, countName, "count")
   381  	b.pb.int64Opt(tagProfile_Period, 1)
   382  	b.pbValueType(tagProfile_SampleType, countName, "count")
   383  	b.pbValueType(tagProfile_SampleType, cycleName, "nanoseconds")
   384  
   385  	cpuGHz := float64(runtime_cyclesPerSecond()) / 1e9
   386  
   387  	values := []int64{0, 0}
   388  	var locs []uint64
   389  	for _, r := range records {
   390  		count, nanosec := scaler(r.Count, float64(r.Cycles)/cpuGHz)
   391  		values[0] = count
   392  		values[1] = int64(nanosec)
   393  		// For count profiles, all stack addresses are
   394  		// return PCs, which is what appendLocsForStack expects.
   395  		locs = b.appendLocsForStack(locs[:0], r.Stack())
   396  		b.pbSample(values, locs, nil)
   397  	}
   398  	b.build()
   399  	return nil
   400  }
   401  
   402  // printCountProfile prints a countProfile at the specified debug level.
   403  // The profile will be in compressed proto format unless debug is nonzero.
   404  func printCountProfile(w io.Writer, debug int, name string, p countProfile) error {
   405  	// Build count of each stack.
   406  	var buf bytes.Buffer
   407  	key := func(stk []uintptr, lbls *labelMap) string {
   408  		buf.Reset()
   409  		fmt.Fprintf(&buf, "@")
   410  		for _, pc := range stk {
   411  			fmt.Fprintf(&buf, " %#x", pc)
   412  		}
   413  		if lbls != nil {
   414  			buf.WriteString("\n# labels: ")
   415  			buf.WriteString(lbls.String())
   416  		}
   417  		return buf.String()
   418  	}
   419  	count := map[string]int{}
   420  	index := map[string]int{}
   421  	var keys []string
   422  	n := p.Len()
   423  	for i := 0; i < n; i++ {
   424  		k := key(p.Stack(i), p.Label(i))
   425  		if count[k] == 0 {
   426  			index[k] = i
   427  			keys = append(keys, k)
   428  		}
   429  		count[k]++
   430  	}
   431  
   432  	sort.Sort(&keysByCount{keys, count})
   433  
   434  	if debug > 0 {
   435  		// Print debug profile in legacy format
   436  		tw := tabwriter.NewWriter(w, 1, 8, 1, '\t', 0)
   437  		fmt.Fprintf(tw, "%s profile: total %d\n", name, p.Len())
   438  		for _, k := range keys {
   439  			fmt.Fprintf(tw, "%d %s\n", count[k], k)
   440  			printStackRecord(tw, p.Stack(index[k]), false)
   441  		}
   442  		return tw.Flush()
   443  	}
   444  
   445  	// Output profile in protobuf form.
   446  	b := newProfileBuilder(w)
   447  	b.pbValueType(tagProfile_PeriodType, name, "count")
   448  	b.pb.int64Opt(tagProfile_Period, 1)
   449  	b.pbValueType(tagProfile_SampleType, name, "count")
   450  
   451  	values := []int64{0}
   452  	var locs []uint64
   453  	for _, k := range keys {
   454  		values[0] = int64(count[k])
   455  		// For count profiles, all stack addresses are
   456  		// return PCs, which is what appendLocsForStack expects.
   457  		locs = b.appendLocsForStack(locs[:0], p.Stack(index[k]))
   458  		idx := index[k]
   459  		var labels func()
   460  		if p.Label(idx) != nil {
   461  			labels = func() {
   462  				for k, v := range *p.Label(idx) {
   463  					b.pbLabel(tagSample_Label, k, v, 0)
   464  				}
   465  			}
   466  		}
   467  		b.pbSample(values, locs, labels)
   468  	}
   469  	b.build()
   470  	return nil
   471  }
   472  
   473  // keysByCount sorts keys with higher counts first, breaking ties by key string order.
   474  type keysByCount struct {
   475  	keys  []string
   476  	count map[string]int
   477  }
   478  
   479  func (x *keysByCount) Len() int      { return len(x.keys) }
   480  func (x *keysByCount) Swap(i, j int) { x.keys[i], x.keys[j] = x.keys[j], x.keys[i] }
   481  func (x *keysByCount) Less(i, j int) bool {
   482  	ki, kj := x.keys[i], x.keys[j]
   483  	ci, cj := x.count[ki], x.count[kj]
   484  	if ci != cj {
   485  		return ci > cj
   486  	}
   487  	return ki < kj
   488  }
   489  
   490  // printStackRecord prints the function + source line information
   491  // for a single stack trace.
   492  func printStackRecord(w io.Writer, stk []uintptr, allFrames bool) {
   493  	show := allFrames
   494  	frames := runtime.CallersFrames(stk)
   495  	for {
   496  		frame, more := frames.Next()
   497  		name := frame.Function
   498  		if name == "" {
   499  			show = true
   500  			fmt.Fprintf(w, "#\t%#x\n", frame.PC)
   501  		} else if name != "runtime.goexit" && (show || !strings.HasPrefix(name, "runtime.")) {
   502  			// Hide runtime.goexit and any runtime functions at the beginning.
   503  			// This is useful mainly for allocation traces.
   504  			show = true
   505  			fmt.Fprintf(w, "#\t%#x\t%s+%#x\t%s:%d\n", frame.PC, name, frame.PC-frame.Entry, frame.File, frame.Line)
   506  		}
   507  		if !more {
   508  			break
   509  		}
   510  	}
   511  	if !show {
   512  		// We didn't print anything; do it again,
   513  		// and this time include runtime functions.
   514  		printStackRecord(w, stk, true)
   515  		return
   516  	}
   517  	fmt.Fprintf(w, "\n")
   518  }
   519  
   520  // Interface to system profiles.
   521  
   522  // WriteHeapProfile is shorthand for Lookup("heap").WriteTo(w, 0).
   523  // It is preserved for backwards compatibility.
   524  func WriteHeapProfile(w io.Writer) error {
   525  	return writeHeap(w, 0)
   526  }
   527  
   528  // countHeap returns the number of records in the heap profile.
   529  func countHeap() int {
   530  	n, _ := runtime.MemProfile(nil, true)
   531  	return n
   532  }
   533  
   534  // writeHeap writes the current runtime heap profile to w.
   535  func writeHeap(w io.Writer, debug int) error {
   536  	return writeHeapInternal(w, debug, "")
   537  }
   538  
   539  // writeAlloc writes the current runtime heap profile to w
   540  // with the total allocation space as the default sample type.
   541  func writeAlloc(w io.Writer, debug int) error {
   542  	return writeHeapInternal(w, debug, "alloc_space")
   543  }
   544  
   545  func writeHeapInternal(w io.Writer, debug int, defaultSampleType string) error {
   546  	var memStats *runtime.MemStats
   547  	if debug != 0 {
   548  		// Read mem stats first, so that our other allocations
   549  		// do not appear in the statistics.
   550  		memStats = new(runtime.MemStats)
   551  		runtime.ReadMemStats(memStats)
   552  	}
   553  
   554  	// Find out how many records there are (MemProfile(nil, true)),
   555  	// allocate that many records, and get the data.
   556  	// There's a race—more records might be added between
   557  	// the two calls—so allocate a few extra records for safety
   558  	// and also try again if we're very unlucky.
   559  	// The loop should only execute one iteration in the common case.
   560  	var p []runtime.MemProfileRecord
   561  	n, ok := runtime.MemProfile(nil, true)
   562  	for {
   563  		// Allocate room for a slightly bigger profile,
   564  		// in case a few more entries have been added
   565  		// since the call to MemProfile.
   566  		p = make([]runtime.MemProfileRecord, n+50)
   567  		n, ok = runtime.MemProfile(p, true)
   568  		if ok {
   569  			p = p[0:n]
   570  			break
   571  		}
   572  		// Profile grew; try again.
   573  	}
   574  
   575  	if debug == 0 {
   576  		return writeHeapProto(w, p, int64(runtime.MemProfileRate), defaultSampleType)
   577  	}
   578  
   579  	sort.Slice(p, func(i, j int) bool { return p[i].InUseBytes() > p[j].InUseBytes() })
   580  
   581  	b := bufio.NewWriter(w)
   582  	tw := tabwriter.NewWriter(b, 1, 8, 1, '\t', 0)
   583  	w = tw
   584  
   585  	var total runtime.MemProfileRecord
   586  	for i := range p {
   587  		r := &p[i]
   588  		total.AllocBytes += r.AllocBytes
   589  		total.AllocObjects += r.AllocObjects
   590  		total.FreeBytes += r.FreeBytes
   591  		total.FreeObjects += r.FreeObjects
   592  	}
   593  
   594  	// Technically the rate is MemProfileRate not 2*MemProfileRate,
   595  	// but early versions of the C++ heap profiler reported 2*MemProfileRate,
   596  	// so that's what pprof has come to expect.
   597  	fmt.Fprintf(w, "heap profile: %d: %d [%d: %d] @ heap/%d\n",
   598  		total.InUseObjects(), total.InUseBytes(),
   599  		total.AllocObjects, total.AllocBytes,
   600  		2*runtime.MemProfileRate)
   601  
   602  	for i := range p {
   603  		r := &p[i]
   604  		fmt.Fprintf(w, "%d: %d [%d: %d] @",
   605  			r.InUseObjects(), r.InUseBytes(),
   606  			r.AllocObjects, r.AllocBytes)
   607  		for _, pc := range r.Stack() {
   608  			fmt.Fprintf(w, " %#x", pc)
   609  		}
   610  		fmt.Fprintf(w, "\n")
   611  		printStackRecord(w, r.Stack(), false)
   612  	}
   613  
   614  	// Print memstats information too.
   615  	// Pprof will ignore, but useful for people
   616  	s := memStats
   617  	fmt.Fprintf(w, "\n# runtime.MemStats\n")
   618  	fmt.Fprintf(w, "# Alloc = %d\n", s.Alloc)
   619  	fmt.Fprintf(w, "# TotalAlloc = %d\n", s.TotalAlloc)
   620  	fmt.Fprintf(w, "# Sys = %d\n", s.Sys)
   621  	fmt.Fprintf(w, "# Lookups = %d\n", s.Lookups)
   622  	fmt.Fprintf(w, "# Mallocs = %d\n", s.Mallocs)
   623  	fmt.Fprintf(w, "# Frees = %d\n", s.Frees)
   624  
   625  	fmt.Fprintf(w, "# HeapAlloc = %d\n", s.HeapAlloc)
   626  	fmt.Fprintf(w, "# HeapSys = %d\n", s.HeapSys)
   627  	fmt.Fprintf(w, "# HeapIdle = %d\n", s.HeapIdle)
   628  	fmt.Fprintf(w, "# HeapInuse = %d\n", s.HeapInuse)
   629  	fmt.Fprintf(w, "# HeapReleased = %d\n", s.HeapReleased)
   630  	fmt.Fprintf(w, "# HeapObjects = %d\n", s.HeapObjects)
   631  
   632  	fmt.Fprintf(w, "# Stack = %d / %d\n", s.StackInuse, s.StackSys)
   633  	fmt.Fprintf(w, "# MSpan = %d / %d\n", s.MSpanInuse, s.MSpanSys)
   634  	fmt.Fprintf(w, "# MCache = %d / %d\n", s.MCacheInuse, s.MCacheSys)
   635  	fmt.Fprintf(w, "# BuckHashSys = %d\n", s.BuckHashSys)
   636  	fmt.Fprintf(w, "# GCSys = %d\n", s.GCSys)
   637  	fmt.Fprintf(w, "# OtherSys = %d\n", s.OtherSys)
   638  
   639  	fmt.Fprintf(w, "# NextGC = %d\n", s.NextGC)
   640  	fmt.Fprintf(w, "# LastGC = %d\n", s.LastGC)
   641  	fmt.Fprintf(w, "# PauseNs = %d\n", s.PauseNs)
   642  	fmt.Fprintf(w, "# PauseEnd = %d\n", s.PauseEnd)
   643  	fmt.Fprintf(w, "# NumGC = %d\n", s.NumGC)
   644  	fmt.Fprintf(w, "# NumForcedGC = %d\n", s.NumForcedGC)
   645  	fmt.Fprintf(w, "# GCCPUFraction = %v\n", s.GCCPUFraction)
   646  	fmt.Fprintf(w, "# DebugGC = %v\n", s.DebugGC)
   647  
   648  	// Also flush out MaxRSS on supported platforms.
   649  	addMaxRSS(w)
   650  
   651  	tw.Flush()
   652  	return b.Flush()
   653  }
   654  
   655  // countThreadCreate returns the size of the current ThreadCreateProfile.
   656  func countThreadCreate() int {
   657  	n, _ := runtime.ThreadCreateProfile(nil)
   658  	return n
   659  }
   660  
   661  // writeThreadCreate writes the current runtime ThreadCreateProfile to w.
   662  func writeThreadCreate(w io.Writer, debug int) error {
   663  	// Until https://golang.org/issues/6104 is addressed, wrap
   664  	// ThreadCreateProfile because there's no point in tracking labels when we
   665  	// don't get any stack-traces.
   666  	return writeRuntimeProfile(w, debug, "threadcreate", func(p []runtime.StackRecord, _ []unsafe.Pointer) (n int, ok bool) {
   667  		return runtime.ThreadCreateProfile(p)
   668  	})
   669  }
   670  
   671  // countGoroutine returns the number of goroutines.
   672  func countGoroutine() int {
   673  	return runtime.NumGoroutine()
   674  }
   675  
   676  // runtime_goroutineProfileWithLabels is defined in runtime/mprof.go
   677  func runtime_goroutineProfileWithLabels(p []runtime.StackRecord, labels []unsafe.Pointer) (n int, ok bool)
   678  
   679  // writeGoroutine writes the current runtime GoroutineProfile to w.
   680  func writeGoroutine(w io.Writer, debug int) error {
   681  	if debug >= 2 {
   682  		return writeGoroutineStacks(w)
   683  	}
   684  	return writeRuntimeProfile(w, debug, "goroutine", runtime_goroutineProfileWithLabels)
   685  }
   686  
   687  func writeGoroutineStacks(w io.Writer) error {
   688  	// We don't know how big the buffer needs to be to collect
   689  	// all the goroutines. Start with 1 MB and try a few times, doubling each time.
   690  	// Give up and use a truncated trace if 64 MB is not enough.
   691  	buf := make([]byte, 1<<20)
   692  	for i := 0; ; i++ {
   693  		n := runtime.Stack(buf, true)
   694  		if n < len(buf) {
   695  			buf = buf[:n]
   696  			break
   697  		}
   698  		if len(buf) >= 64<<20 {
   699  			// Filled 64 MB - stop there.
   700  			break
   701  		}
   702  		buf = make([]byte, 2*len(buf))
   703  	}
   704  	_, err := w.Write(buf)
   705  	return err
   706  }
   707  
   708  func writeRuntimeProfile(w io.Writer, debug int, name string, fetch func([]runtime.StackRecord, []unsafe.Pointer) (int, bool)) error {
   709  	// Find out how many records there are (fetch(nil)),
   710  	// allocate that many records, and get the data.
   711  	// There's a race—more records might be added between
   712  	// the two calls—so allocate a few extra records for safety
   713  	// and also try again if we're very unlucky.
   714  	// The loop should only execute one iteration in the common case.
   715  	var p []runtime.StackRecord
   716  	var labels []unsafe.Pointer
   717  	n, ok := fetch(nil, nil)
   718  	for {
   719  		// Allocate room for a slightly bigger profile,
   720  		// in case a few more entries have been added
   721  		// since the call to ThreadProfile.
   722  		p = make([]runtime.StackRecord, n+10)
   723  		labels = make([]unsafe.Pointer, n+10)
   724  		n, ok = fetch(p, labels)
   725  		if ok {
   726  			p = p[0:n]
   727  			break
   728  		}
   729  		// Profile grew; try again.
   730  	}
   731  
   732  	return printCountProfile(w, debug, name, &runtimeProfile{p, labels})
   733  }
   734  
   735  type runtimeProfile struct {
   736  	stk    []runtime.StackRecord
   737  	labels []unsafe.Pointer
   738  }
   739  
   740  func (p *runtimeProfile) Len() int              { return len(p.stk) }
   741  func (p *runtimeProfile) Stack(i int) []uintptr { return p.stk[i].Stack() }
   742  func (p *runtimeProfile) Label(i int) *labelMap { return (*labelMap)(p.labels[i]) }
   743  
   744  var cpu struct {
   745  	sync.Mutex
   746  	profiling bool
   747  	done      chan bool
   748  }
   749  
   750  // StartCPUProfile enables CPU profiling for the current process.
   751  // While profiling, the profile will be buffered and written to w.
   752  // StartCPUProfile returns an error if profiling is already enabled.
   753  //
   754  // On Unix-like systems, StartCPUProfile does not work by default for
   755  // Go code built with -buildmode=c-archive or -buildmode=c-shared.
   756  // StartCPUProfile relies on the SIGPROF signal, but that signal will
   757  // be delivered to the main program's SIGPROF signal handler (if any)
   758  // not to the one used by Go. To make it work, call os/signal.Notify
   759  // for syscall.SIGPROF, but note that doing so may break any profiling
   760  // being done by the main program.
   761  func StartCPUProfile(w io.Writer) error {
   762  	// The runtime routines allow a variable profiling rate,
   763  	// but in practice operating systems cannot trigger signals
   764  	// at more than about 500 Hz, and our processing of the
   765  	// signal is not cheap (mostly getting the stack trace).
   766  	// 100 Hz is a reasonable choice: it is frequent enough to
   767  	// produce useful data, rare enough not to bog down the
   768  	// system, and a nice round number to make it easy to
   769  	// convert sample counts to seconds. Instead of requiring
   770  	// each client to specify the frequency, we hard code it.
   771  	const hz = 100
   772  
   773  	cpu.Lock()
   774  	defer cpu.Unlock()
   775  	if cpu.done == nil {
   776  		cpu.done = make(chan bool)
   777  	}
   778  	// Double-check.
   779  	if cpu.profiling {
   780  		return fmt.Errorf("cpu profiling already in use")
   781  	}
   782  	cpu.profiling = true
   783  	runtime.SetCPUProfileRate(hz)
   784  	go profileWriter(w)
   785  	return nil
   786  }
   787  
   788  // readProfile, provided by the runtime, returns the next chunk of
   789  // binary CPU profiling stack trace data, blocking until data is available.
   790  // If profiling is turned off and all the profile data accumulated while it was
   791  // on has been returned, readProfile returns eof=true.
   792  // The caller must save the returned data and tags before calling readProfile again.
   793  func readProfile() (data []uint64, tags []unsafe.Pointer, eof bool)
   794  
   795  func profileWriter(w io.Writer) {
   796  	b := newProfileBuilder(w)
   797  	var err error
   798  	for {
   799  		time.Sleep(100 * time.Millisecond)
   800  		data, tags, eof := readProfile()
   801  		if e := b.addCPUData(data, tags); e != nil && err == nil {
   802  			err = e
   803  		}
   804  		if eof {
   805  			break
   806  		}
   807  	}
   808  	if err != nil {
   809  		// The runtime should never produce an invalid or truncated profile.
   810  		// It drops records that can't fit into its log buffers.
   811  		panic("runtime/pprof: converting profile: " + err.Error())
   812  	}
   813  	b.build()
   814  	cpu.done <- true
   815  }
   816  
   817  // StopCPUProfile stops the current CPU profile, if any.
   818  // StopCPUProfile only returns after all the writes for the
   819  // profile have completed.
   820  func StopCPUProfile() {
   821  	cpu.Lock()
   822  	defer cpu.Unlock()
   823  
   824  	if !cpu.profiling {
   825  		return
   826  	}
   827  	cpu.profiling = false
   828  	runtime.SetCPUProfileRate(0)
   829  	<-cpu.done
   830  }
   831  
   832  // countBlock returns the number of records in the blocking profile.
   833  func countBlock() int {
   834  	n, _ := runtime.BlockProfile(nil)
   835  	return n
   836  }
   837  
   838  // countMutex returns the number of records in the mutex profile.
   839  func countMutex() int {
   840  	n, _ := runtime.MutexProfile(nil)
   841  	return n
   842  }
   843  
   844  // writeBlock writes the current blocking profile to w.
   845  func writeBlock(w io.Writer, debug int) error {
   846  	var p []runtime.BlockProfileRecord
   847  	n, ok := runtime.BlockProfile(nil)
   848  	for {
   849  		p = make([]runtime.BlockProfileRecord, n+50)
   850  		n, ok = runtime.BlockProfile(p)
   851  		if ok {
   852  			p = p[:n]
   853  			break
   854  		}
   855  	}
   856  
   857  	sort.Slice(p, func(i, j int) bool { return p[i].Cycles > p[j].Cycles })
   858  
   859  	if debug <= 0 {
   860  		return printCountCycleProfile(w, "contentions", "delay", scaleBlockProfile, p)
   861  	}
   862  
   863  	b := bufio.NewWriter(w)
   864  	tw := tabwriter.NewWriter(w, 1, 8, 1, '\t', 0)
   865  	w = tw
   866  
   867  	fmt.Fprintf(w, "--- contention:\n")
   868  	fmt.Fprintf(w, "cycles/second=%v\n", runtime_cyclesPerSecond())
   869  	for i := range p {
   870  		r := &p[i]
   871  		fmt.Fprintf(w, "%v %v @", r.Cycles, r.Count)
   872  		for _, pc := range r.Stack() {
   873  			fmt.Fprintf(w, " %#x", pc)
   874  		}
   875  		fmt.Fprint(w, "\n")
   876  		if debug > 0 {
   877  			printStackRecord(w, r.Stack(), true)
   878  		}
   879  	}
   880  
   881  	if tw != nil {
   882  		tw.Flush()
   883  	}
   884  	return b.Flush()
   885  }
   886  
   887  func scaleBlockProfile(cnt int64, ns float64) (int64, float64) {
   888  	// Do nothing.
   889  	// The current way of block profile sampling makes it
   890  	// hard to compute the unsampled number. The legacy block
   891  	// profile parse doesn't attempt to scale or unsample.
   892  	return cnt, ns
   893  }
   894  
   895  // writeMutex writes the current mutex profile to w.
   896  func writeMutex(w io.Writer, debug int) error {
   897  	// TODO(pjw): too much common code with writeBlock. FIX!
   898  	var p []runtime.BlockProfileRecord
   899  	n, ok := runtime.MutexProfile(nil)
   900  	for {
   901  		p = make([]runtime.BlockProfileRecord, n+50)
   902  		n, ok = runtime.MutexProfile(p)
   903  		if ok {
   904  			p = p[:n]
   905  			break
   906  		}
   907  	}
   908  
   909  	sort.Slice(p, func(i, j int) bool { return p[i].Cycles > p[j].Cycles })
   910  
   911  	if debug <= 0 {
   912  		return printCountCycleProfile(w, "contentions", "delay", scaleMutexProfile, p)
   913  	}
   914  
   915  	b := bufio.NewWriter(w)
   916  	tw := tabwriter.NewWriter(w, 1, 8, 1, '\t', 0)
   917  	w = tw
   918  
   919  	fmt.Fprintf(w, "--- mutex:\n")
   920  	fmt.Fprintf(w, "cycles/second=%v\n", runtime_cyclesPerSecond())
   921  	fmt.Fprintf(w, "sampling period=%d\n", runtime.SetMutexProfileFraction(-1))
   922  	for i := range p {
   923  		r := &p[i]
   924  		fmt.Fprintf(w, "%v %v @", r.Cycles, r.Count)
   925  		for _, pc := range r.Stack() {
   926  			fmt.Fprintf(w, " %#x", pc)
   927  		}
   928  		fmt.Fprint(w, "\n")
   929  		if debug > 0 {
   930  			printStackRecord(w, r.Stack(), true)
   931  		}
   932  	}
   933  
   934  	if tw != nil {
   935  		tw.Flush()
   936  	}
   937  	return b.Flush()
   938  }
   939  
   940  func scaleMutexProfile(cnt int64, ns float64) (int64, float64) {
   941  	period := runtime.SetMutexProfileFraction(-1)
   942  	return cnt * int64(period), ns * float64(period)
   943  }
   944  
   945  func runtime_cyclesPerSecond() int64
   946  

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