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/main/doc/README.md.
    73  package pprof
    74  
    75  import (
    76  	"bufio"
    77  	"fmt"
    78  	"internal/abi"
    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  // [Profile.Add] or [Profile.Remove] method call.
   111  //
   112  // The CPU profile is not available as a Profile. It has a special API,
   113  // the [StartCPUProfile] and [StopCPUProfile] functions, because it streams
   114  // output to a writer during profiling.
   115  //
   116  // # Heap profile
   117  //
   118  // The heap profile reports statistics as of the most recently completed
   119  // garbage collection; it elides more recent allocation to avoid skewing
   120  // the profile away from live data and toward garbage.
   121  // If there has been no garbage collection at all, the heap profile reports
   122  // all known allocations. This exception helps mainly in programs running
   123  // without garbage collection enabled, usually for debugging purposes.
   124  //
   125  // The heap profile tracks both the allocation sites for all live objects in
   126  // the application memory and for all objects allocated since the program start.
   127  // Pprof's -inuse_space, -inuse_objects, -alloc_space, and -alloc_objects
   128  // flags select which to display, defaulting to -inuse_space (live objects,
   129  // scaled by size).
   130  //
   131  // # Allocs profile
   132  //
   133  // The allocs profile is the same as the heap profile but changes the default
   134  // pprof display to -alloc_space, the total number of bytes allocated since
   135  // the program began (including garbage-collected bytes).
   136  //
   137  // # Block profile
   138  //
   139  // The block profile tracks time spent blocked on synchronization primitives,
   140  // such as [sync.Mutex], [sync.RWMutex], [sync.WaitGroup], [sync.Cond], and
   141  // channel send/receive/select.
   142  //
   143  // Stack traces correspond to the location that blocked (for example,
   144  // [sync.Mutex.Lock]).
   145  //
   146  // Sample values correspond to cumulative time spent blocked at that stack
   147  // trace, subject to time-based sampling specified by
   148  // [runtime.SetBlockProfileRate].
   149  //
   150  // # Mutex profile
   151  //
   152  // The mutex profile tracks contention on mutexes, such as [sync.Mutex],
   153  // [sync.RWMutex], and runtime-internal locks.
   154  //
   155  // Stack traces correspond to the end of the critical section causing
   156  // contention. For example, a lock held for a long time while other goroutines
   157  // are waiting to acquire the lock will report contention when the lock is
   158  // finally unlocked (that is, at [sync.Mutex.Unlock]).
   159  //
   160  // Sample values correspond to the approximate cumulative time other goroutines
   161  // spent blocked waiting for the lock, subject to event-based sampling
   162  // specified by [runtime.SetMutexProfileFraction]. For example, if a caller
   163  // holds a lock for 1s while 5 other goroutines are waiting for the entire
   164  // second to acquire the lock, its unlock call stack will report 5s of
   165  // contention.
   166  //
   167  // Runtime-internal locks are always reported at the location
   168  // "runtime._LostContendedRuntimeLock". More detailed stack traces for
   169  // runtime-internal locks can be obtained by setting
   170  // `GODEBUG=runtimecontentionstacks=1` (see package [runtime] docs for
   171  // caveats).
   172  type Profile struct {
   173  	name  string
   174  	mu    sync.Mutex
   175  	m     map[any][]uintptr
   176  	count func() int
   177  	write func(io.Writer, int) error
   178  }
   179  
   180  // profiles records all registered profiles.
   181  var profiles struct {
   182  	mu sync.Mutex
   183  	m  map[string]*Profile
   184  }
   185  
   186  var goroutineProfile = &Profile{
   187  	name:  "goroutine",
   188  	count: countGoroutine,
   189  	write: writeGoroutine,
   190  }
   191  
   192  var threadcreateProfile = &Profile{
   193  	name:  "threadcreate",
   194  	count: countThreadCreate,
   195  	write: writeThreadCreate,
   196  }
   197  
   198  var heapProfile = &Profile{
   199  	name:  "heap",
   200  	count: countHeap,
   201  	write: writeHeap,
   202  }
   203  
   204  var allocsProfile = &Profile{
   205  	name:  "allocs",
   206  	count: countHeap, // identical to heap profile
   207  	write: writeAlloc,
   208  }
   209  
   210  var blockProfile = &Profile{
   211  	name:  "block",
   212  	count: countBlock,
   213  	write: writeBlock,
   214  }
   215  
   216  var mutexProfile = &Profile{
   217  	name:  "mutex",
   218  	count: countMutex,
   219  	write: writeMutex,
   220  }
   221  
   222  func lockProfiles() {
   223  	profiles.mu.Lock()
   224  	if profiles.m == nil {
   225  		// Initial built-in profiles.
   226  		profiles.m = map[string]*Profile{
   227  			"goroutine":    goroutineProfile,
   228  			"threadcreate": threadcreateProfile,
   229  			"heap":         heapProfile,
   230  			"allocs":       allocsProfile,
   231  			"block":        blockProfile,
   232  			"mutex":        mutexProfile,
   233  		}
   234  	}
   235  }
   236  
   237  func unlockProfiles() {
   238  	profiles.mu.Unlock()
   239  }
   240  
   241  // NewProfile creates a new profile with the given name.
   242  // If a profile with that name already exists, NewProfile panics.
   243  // The convention is to use a 'import/path.' prefix to create
   244  // separate name spaces for each package.
   245  // For compatibility with various tools that read pprof data,
   246  // profile names should not contain spaces.
   247  func NewProfile(name string) *Profile {
   248  	lockProfiles()
   249  	defer unlockProfiles()
   250  	if name == "" {
   251  		panic("pprof: NewProfile with empty name")
   252  	}
   253  	if profiles.m[name] != nil {
   254  		panic("pprof: NewProfile name already in use: " + name)
   255  	}
   256  	p := &Profile{
   257  		name: name,
   258  		m:    map[any][]uintptr{},
   259  	}
   260  	profiles.m[name] = p
   261  	return p
   262  }
   263  
   264  // Lookup returns the profile with the given name, or nil if no such profile exists.
   265  func Lookup(name string) *Profile {
   266  	lockProfiles()
   267  	defer unlockProfiles()
   268  	return profiles.m[name]
   269  }
   270  
   271  // Profiles returns a slice of all the known profiles, sorted by name.
   272  func Profiles() []*Profile {
   273  	lockProfiles()
   274  	defer unlockProfiles()
   275  
   276  	all := make([]*Profile, 0, len(profiles.m))
   277  	for _, p := range profiles.m {
   278  		all = append(all, p)
   279  	}
   280  
   281  	sort.Slice(all, func(i, j int) bool { return all[i].name < all[j].name })
   282  	return all
   283  }
   284  
   285  // Name returns this profile's name, which can be passed to [Lookup] to reobtain the profile.
   286  func (p *Profile) Name() string {
   287  	return p.name
   288  }
   289  
   290  // Count returns the number of execution stacks currently in the profile.
   291  func (p *Profile) Count() int {
   292  	p.mu.Lock()
   293  	defer p.mu.Unlock()
   294  	if p.count != nil {
   295  		return p.count()
   296  	}
   297  	return len(p.m)
   298  }
   299  
   300  // Add adds the current execution stack to the profile, associated with value.
   301  // Add stores value in an internal map, so value must be suitable for use as
   302  // a map key and will not be garbage collected until the corresponding
   303  // call to [Profile.Remove]. Add panics if the profile already contains a stack for value.
   304  //
   305  // The skip parameter has the same meaning as [runtime.Caller]'s skip
   306  // and controls where the stack trace begins. Passing skip=0 begins the
   307  // trace in the function calling Add. For example, given this
   308  // execution stack:
   309  //
   310  //	Add
   311  //	called from rpc.NewClient
   312  //	called from mypkg.Run
   313  //	called from main.main
   314  //
   315  // Passing skip=0 begins the stack trace at the call to Add inside rpc.NewClient.
   316  // Passing skip=1 begins the stack trace at the call to NewClient inside mypkg.Run.
   317  func (p *Profile) Add(value any, skip int) {
   318  	if p.name == "" {
   319  		panic("pprof: use of uninitialized Profile")
   320  	}
   321  	if p.write != nil {
   322  		panic("pprof: Add called on built-in Profile " + p.name)
   323  	}
   324  
   325  	stk := make([]uintptr, 32)
   326  	n := runtime.Callers(skip+1, stk[:])
   327  	stk = stk[:n]
   328  	if len(stk) == 0 {
   329  		// The value for skip is too large, and there's no stack trace to record.
   330  		stk = []uintptr{abi.FuncPCABIInternal(lostProfileEvent)}
   331  	}
   332  
   333  	p.mu.Lock()
   334  	defer p.mu.Unlock()
   335  	if p.m[value] != nil {
   336  		panic("pprof: Profile.Add of duplicate value")
   337  	}
   338  	p.m[value] = stk
   339  }
   340  
   341  // Remove removes the execution stack associated with value from the profile.
   342  // It is a no-op if the value is not in the profile.
   343  func (p *Profile) Remove(value any) {
   344  	p.mu.Lock()
   345  	defer p.mu.Unlock()
   346  	delete(p.m, value)
   347  }
   348  
   349  // WriteTo writes a pprof-formatted snapshot of the profile to w.
   350  // If a write to w returns an error, WriteTo returns that error.
   351  // Otherwise, WriteTo returns nil.
   352  //
   353  // The debug parameter enables additional output.
   354  // Passing debug=0 writes the gzip-compressed protocol buffer described
   355  // in https://github.com/google/pprof/tree/master/proto#overview.
   356  // Passing debug=1 writes the legacy text format with comments
   357  // translating addresses to function names and line numbers, so that a
   358  // programmer can read the profile without tools.
   359  //
   360  // The predefined profiles may assign meaning to other debug values;
   361  // for example, when printing the "goroutine" profile, debug=2 means to
   362  // print the goroutine stacks in the same form that a Go program uses
   363  // when dying due to an unrecovered panic.
   364  func (p *Profile) WriteTo(w io.Writer, debug int) error {
   365  	if p.name == "" {
   366  		panic("pprof: use of zero Profile")
   367  	}
   368  	if p.write != nil {
   369  		return p.write(w, debug)
   370  	}
   371  
   372  	// Obtain consistent snapshot under lock; then process without lock.
   373  	p.mu.Lock()
   374  	all := make([][]uintptr, 0, len(p.m))
   375  	for _, stk := range p.m {
   376  		all = append(all, stk)
   377  	}
   378  	p.mu.Unlock()
   379  
   380  	// Map order is non-deterministic; make output deterministic.
   381  	sort.Slice(all, func(i, j int) bool {
   382  		t, u := all[i], all[j]
   383  		for k := 0; k < len(t) && k < len(u); k++ {
   384  			if t[k] != u[k] {
   385  				return t[k] < u[k]
   386  			}
   387  		}
   388  		return len(t) < len(u)
   389  	})
   390  
   391  	return printCountProfile(w, debug, p.name, stackProfile(all))
   392  }
   393  
   394  type stackProfile [][]uintptr
   395  
   396  func (x stackProfile) Len() int              { return len(x) }
   397  func (x stackProfile) Stack(i int) []uintptr { return x[i] }
   398  func (x stackProfile) Label(i int) *labelMap { return nil }
   399  
   400  // A countProfile is a set of stack traces to be printed as counts
   401  // grouped by stack trace. There are multiple implementations:
   402  // all that matters is that we can find out how many traces there are
   403  // and obtain each trace in turn.
   404  type countProfile interface {
   405  	Len() int
   406  	Stack(i int) []uintptr
   407  	Label(i int) *labelMap
   408  }
   409  
   410  // printCountCycleProfile outputs block profile records (for block or mutex profiles)
   411  // as the pprof-proto format output. Translations from cycle count to time duration
   412  // are done because The proto expects count and time (nanoseconds) instead of count
   413  // and the number of cycles for block, contention profiles.
   414  func printCountCycleProfile(w io.Writer, countName, cycleName string, records []runtime.BlockProfileRecord) error {
   415  	// Output profile in protobuf form.
   416  	b := newProfileBuilder(w)
   417  	b.pbValueType(tagProfile_PeriodType, countName, "count")
   418  	b.pb.int64Opt(tagProfile_Period, 1)
   419  	b.pbValueType(tagProfile_SampleType, countName, "count")
   420  	b.pbValueType(tagProfile_SampleType, cycleName, "nanoseconds")
   421  
   422  	cpuGHz := float64(runtime_cyclesPerSecond()) / 1e9
   423  
   424  	values := []int64{0, 0}
   425  	var locs []uint64
   426  	for _, r := range records {
   427  		values[0] = r.Count
   428  		values[1] = int64(float64(r.Cycles) / cpuGHz)
   429  		// For count profiles, all stack addresses are
   430  		// return PCs, which is what appendLocsForStack expects.
   431  		locs = b.appendLocsForStack(locs[:0], r.Stack())
   432  		b.pbSample(values, locs, nil)
   433  	}
   434  	b.build()
   435  	return nil
   436  }
   437  
   438  // printCountProfile prints a countProfile at the specified debug level.
   439  // The profile will be in compressed proto format unless debug is nonzero.
   440  func printCountProfile(w io.Writer, debug int, name string, p countProfile) error {
   441  	// Build count of each stack.
   442  	var buf strings.Builder
   443  	key := func(stk []uintptr, lbls *labelMap) string {
   444  		buf.Reset()
   445  		fmt.Fprintf(&buf, "@")
   446  		for _, pc := range stk {
   447  			fmt.Fprintf(&buf, " %#x", pc)
   448  		}
   449  		if lbls != nil {
   450  			buf.WriteString("\n# labels: ")
   451  			buf.WriteString(lbls.String())
   452  		}
   453  		return buf.String()
   454  	}
   455  	count := map[string]int{}
   456  	index := map[string]int{}
   457  	var keys []string
   458  	n := p.Len()
   459  	for i := 0; i < n; i++ {
   460  		k := key(p.Stack(i), p.Label(i))
   461  		if count[k] == 0 {
   462  			index[k] = i
   463  			keys = append(keys, k)
   464  		}
   465  		count[k]++
   466  	}
   467  
   468  	sort.Sort(&keysByCount{keys, count})
   469  
   470  	if debug > 0 {
   471  		// Print debug profile in legacy format
   472  		tw := tabwriter.NewWriter(w, 1, 8, 1, '\t', 0)
   473  		fmt.Fprintf(tw, "%s profile: total %d\n", name, p.Len())
   474  		for _, k := range keys {
   475  			fmt.Fprintf(tw, "%d %s\n", count[k], k)
   476  			printStackRecord(tw, p.Stack(index[k]), false)
   477  		}
   478  		return tw.Flush()
   479  	}
   480  
   481  	// Output profile in protobuf form.
   482  	b := newProfileBuilder(w)
   483  	b.pbValueType(tagProfile_PeriodType, name, "count")
   484  	b.pb.int64Opt(tagProfile_Period, 1)
   485  	b.pbValueType(tagProfile_SampleType, name, "count")
   486  
   487  	values := []int64{0}
   488  	var locs []uint64
   489  	for _, k := range keys {
   490  		values[0] = int64(count[k])
   491  		// For count profiles, all stack addresses are
   492  		// return PCs, which is what appendLocsForStack expects.
   493  		locs = b.appendLocsForStack(locs[:0], p.Stack(index[k]))
   494  		idx := index[k]
   495  		var labels func()
   496  		if p.Label(idx) != nil {
   497  			labels = func() {
   498  				for k, v := range *p.Label(idx) {
   499  					b.pbLabel(tagSample_Label, k, v, 0)
   500  				}
   501  			}
   502  		}
   503  		b.pbSample(values, locs, labels)
   504  	}
   505  	b.build()
   506  	return nil
   507  }
   508  
   509  // keysByCount sorts keys with higher counts first, breaking ties by key string order.
   510  type keysByCount struct {
   511  	keys  []string
   512  	count map[string]int
   513  }
   514  
   515  func (x *keysByCount) Len() int      { return len(x.keys) }
   516  func (x *keysByCount) Swap(i, j int) { x.keys[i], x.keys[j] = x.keys[j], x.keys[i] }
   517  func (x *keysByCount) Less(i, j int) bool {
   518  	ki, kj := x.keys[i], x.keys[j]
   519  	ci, cj := x.count[ki], x.count[kj]
   520  	if ci != cj {
   521  		return ci > cj
   522  	}
   523  	return ki < kj
   524  }
   525  
   526  // printStackRecord prints the function + source line information
   527  // for a single stack trace.
   528  func printStackRecord(w io.Writer, stk []uintptr, allFrames bool) {
   529  	show := allFrames
   530  	frames := runtime.CallersFrames(stk)
   531  	for {
   532  		frame, more := frames.Next()
   533  		name := frame.Function
   534  		if name == "" {
   535  			show = true
   536  			fmt.Fprintf(w, "#\t%#x\n", frame.PC)
   537  		} else if name != "runtime.goexit" && (show || !strings.HasPrefix(name, "runtime.")) {
   538  			// Hide runtime.goexit and any runtime functions at the beginning.
   539  			// This is useful mainly for allocation traces.
   540  			show = true
   541  			fmt.Fprintf(w, "#\t%#x\t%s+%#x\t%s:%d\n", frame.PC, name, frame.PC-frame.Entry, frame.File, frame.Line)
   542  		}
   543  		if !more {
   544  			break
   545  		}
   546  	}
   547  	if !show {
   548  		// We didn't print anything; do it again,
   549  		// and this time include runtime functions.
   550  		printStackRecord(w, stk, true)
   551  		return
   552  	}
   553  	fmt.Fprintf(w, "\n")
   554  }
   555  
   556  // Interface to system profiles.
   557  
   558  // WriteHeapProfile is shorthand for [Lookup]("heap").WriteTo(w, 0).
   559  // It is preserved for backwards compatibility.
   560  func WriteHeapProfile(w io.Writer) error {
   561  	return writeHeap(w, 0)
   562  }
   563  
   564  // countHeap returns the number of records in the heap profile.
   565  func countHeap() int {
   566  	n, _ := runtime.MemProfile(nil, true)
   567  	return n
   568  }
   569  
   570  // writeHeap writes the current runtime heap profile to w.
   571  func writeHeap(w io.Writer, debug int) error {
   572  	return writeHeapInternal(w, debug, "")
   573  }
   574  
   575  // writeAlloc writes the current runtime heap profile to w
   576  // with the total allocation space as the default sample type.
   577  func writeAlloc(w io.Writer, debug int) error {
   578  	return writeHeapInternal(w, debug, "alloc_space")
   579  }
   580  
   581  func writeHeapInternal(w io.Writer, debug int, defaultSampleType string) error {
   582  	var memStats *runtime.MemStats
   583  	if debug != 0 {
   584  		// Read mem stats first, so that our other allocations
   585  		// do not appear in the statistics.
   586  		memStats = new(runtime.MemStats)
   587  		runtime.ReadMemStats(memStats)
   588  	}
   589  
   590  	// Find out how many records there are (MemProfile(nil, true)),
   591  	// allocate that many records, and get the data.
   592  	// There's a race—more records might be added between
   593  	// the two calls—so allocate a few extra records for safety
   594  	// and also try again if we're very unlucky.
   595  	// The loop should only execute one iteration in the common case.
   596  	var p []runtime.MemProfileRecord
   597  	n, ok := runtime.MemProfile(nil, true)
   598  	for {
   599  		// Allocate room for a slightly bigger profile,
   600  		// in case a few more entries have been added
   601  		// since the call to MemProfile.
   602  		p = make([]runtime.MemProfileRecord, n+50)
   603  		n, ok = runtime.MemProfile(p, true)
   604  		if ok {
   605  			p = p[0:n]
   606  			break
   607  		}
   608  		// Profile grew; try again.
   609  	}
   610  
   611  	if debug == 0 {
   612  		return writeHeapProto(w, p, int64(runtime.MemProfileRate), defaultSampleType)
   613  	}
   614  
   615  	sort.Slice(p, func(i, j int) bool { return p[i].InUseBytes() > p[j].InUseBytes() })
   616  
   617  	b := bufio.NewWriter(w)
   618  	tw := tabwriter.NewWriter(b, 1, 8, 1, '\t', 0)
   619  	w = tw
   620  
   621  	var total runtime.MemProfileRecord
   622  	for i := range p {
   623  		r := &p[i]
   624  		total.AllocBytes += r.AllocBytes
   625  		total.AllocObjects += r.AllocObjects
   626  		total.FreeBytes += r.FreeBytes
   627  		total.FreeObjects += r.FreeObjects
   628  	}
   629  
   630  	// Technically the rate is MemProfileRate not 2*MemProfileRate,
   631  	// but early versions of the C++ heap profiler reported 2*MemProfileRate,
   632  	// so that's what pprof has come to expect.
   633  	rate := 2 * runtime.MemProfileRate
   634  
   635  	// pprof reads a profile with alloc == inuse as being a "2-column" profile
   636  	// (objects and bytes, not distinguishing alloc from inuse),
   637  	// but then such a profile can't be merged using pprof *.prof with
   638  	// other 4-column profiles where alloc != inuse.
   639  	// The easiest way to avoid this bug is to adjust allocBytes so it's never == inuseBytes.
   640  	// pprof doesn't use these header values anymore except for checking equality.
   641  	inUseBytes := total.InUseBytes()
   642  	allocBytes := total.AllocBytes
   643  	if inUseBytes == allocBytes {
   644  		allocBytes++
   645  	}
   646  
   647  	fmt.Fprintf(w, "heap profile: %d: %d [%d: %d] @ heap/%d\n",
   648  		total.InUseObjects(), inUseBytes,
   649  		total.AllocObjects, allocBytes,
   650  		rate)
   651  
   652  	for i := range p {
   653  		r := &p[i]
   654  		fmt.Fprintf(w, "%d: %d [%d: %d] @",
   655  			r.InUseObjects(), r.InUseBytes(),
   656  			r.AllocObjects, r.AllocBytes)
   657  		for _, pc := range r.Stack() {
   658  			fmt.Fprintf(w, " %#x", pc)
   659  		}
   660  		fmt.Fprintf(w, "\n")
   661  		printStackRecord(w, r.Stack(), false)
   662  	}
   663  
   664  	// Print memstats information too.
   665  	// Pprof will ignore, but useful for people
   666  	s := memStats
   667  	fmt.Fprintf(w, "\n# runtime.MemStats\n")
   668  	fmt.Fprintf(w, "# Alloc = %d\n", s.Alloc)
   669  	fmt.Fprintf(w, "# TotalAlloc = %d\n", s.TotalAlloc)
   670  	fmt.Fprintf(w, "# Sys = %d\n", s.Sys)
   671  	fmt.Fprintf(w, "# Lookups = %d\n", s.Lookups)
   672  	fmt.Fprintf(w, "# Mallocs = %d\n", s.Mallocs)
   673  	fmt.Fprintf(w, "# Frees = %d\n", s.Frees)
   674  
   675  	fmt.Fprintf(w, "# HeapAlloc = %d\n", s.HeapAlloc)
   676  	fmt.Fprintf(w, "# HeapSys = %d\n", s.HeapSys)
   677  	fmt.Fprintf(w, "# HeapIdle = %d\n", s.HeapIdle)
   678  	fmt.Fprintf(w, "# HeapInuse = %d\n", s.HeapInuse)
   679  	fmt.Fprintf(w, "# HeapReleased = %d\n", s.HeapReleased)
   680  	fmt.Fprintf(w, "# HeapObjects = %d\n", s.HeapObjects)
   681  
   682  	fmt.Fprintf(w, "# Stack = %d / %d\n", s.StackInuse, s.StackSys)
   683  	fmt.Fprintf(w, "# MSpan = %d / %d\n", s.MSpanInuse, s.MSpanSys)
   684  	fmt.Fprintf(w, "# MCache = %d / %d\n", s.MCacheInuse, s.MCacheSys)
   685  	fmt.Fprintf(w, "# BuckHashSys = %d\n", s.BuckHashSys)
   686  	fmt.Fprintf(w, "# GCSys = %d\n", s.GCSys)
   687  	fmt.Fprintf(w, "# OtherSys = %d\n", s.OtherSys)
   688  
   689  	fmt.Fprintf(w, "# NextGC = %d\n", s.NextGC)
   690  	fmt.Fprintf(w, "# LastGC = %d\n", s.LastGC)
   691  	fmt.Fprintf(w, "# PauseNs = %d\n", s.PauseNs)
   692  	fmt.Fprintf(w, "# PauseEnd = %d\n", s.PauseEnd)
   693  	fmt.Fprintf(w, "# NumGC = %d\n", s.NumGC)
   694  	fmt.Fprintf(w, "# NumForcedGC = %d\n", s.NumForcedGC)
   695  	fmt.Fprintf(w, "# GCCPUFraction = %v\n", s.GCCPUFraction)
   696  	fmt.Fprintf(w, "# DebugGC = %v\n", s.DebugGC)
   697  
   698  	// Also flush out MaxRSS on supported platforms.
   699  	addMaxRSS(w)
   700  
   701  	tw.Flush()
   702  	return b.Flush()
   703  }
   704  
   705  // countThreadCreate returns the size of the current ThreadCreateProfile.
   706  func countThreadCreate() int {
   707  	n, _ := runtime.ThreadCreateProfile(nil)
   708  	return n
   709  }
   710  
   711  // writeThreadCreate writes the current runtime ThreadCreateProfile to w.
   712  func writeThreadCreate(w io.Writer, debug int) error {
   713  	// Until https://golang.org/issues/6104 is addressed, wrap
   714  	// ThreadCreateProfile because there's no point in tracking labels when we
   715  	// don't get any stack-traces.
   716  	return writeRuntimeProfile(w, debug, "threadcreate", func(p []runtime.StackRecord, _ []unsafe.Pointer) (n int, ok bool) {
   717  		return runtime.ThreadCreateProfile(p)
   718  	})
   719  }
   720  
   721  // countGoroutine returns the number of goroutines.
   722  func countGoroutine() int {
   723  	return runtime.NumGoroutine()
   724  }
   725  
   726  // runtime_goroutineProfileWithLabels is defined in runtime/mprof.go
   727  func runtime_goroutineProfileWithLabels(p []runtime.StackRecord, labels []unsafe.Pointer) (n int, ok bool)
   728  
   729  // writeGoroutine writes the current runtime GoroutineProfile to w.
   730  func writeGoroutine(w io.Writer, debug int) error {
   731  	if debug >= 2 {
   732  		return writeGoroutineStacks(w)
   733  	}
   734  	return writeRuntimeProfile(w, debug, "goroutine", runtime_goroutineProfileWithLabels)
   735  }
   736  
   737  func writeGoroutineStacks(w io.Writer) error {
   738  	// We don't know how big the buffer needs to be to collect
   739  	// all the goroutines. Start with 1 MB and try a few times, doubling each time.
   740  	// Give up and use a truncated trace if 64 MB is not enough.
   741  	buf := make([]byte, 1<<20)
   742  	for i := 0; ; i++ {
   743  		n := runtime.Stack(buf, true)
   744  		if n < len(buf) {
   745  			buf = buf[:n]
   746  			break
   747  		}
   748  		if len(buf) >= 64<<20 {
   749  			// Filled 64 MB - stop there.
   750  			break
   751  		}
   752  		buf = make([]byte, 2*len(buf))
   753  	}
   754  	_, err := w.Write(buf)
   755  	return err
   756  }
   757  
   758  func writeRuntimeProfile(w io.Writer, debug int, name string, fetch func([]runtime.StackRecord, []unsafe.Pointer) (int, bool)) error {
   759  	// Find out how many records there are (fetch(nil)),
   760  	// allocate that many records, and get the data.
   761  	// There's a race—more records might be added between
   762  	// the two calls—so allocate a few extra records for safety
   763  	// and also try again if we're very unlucky.
   764  	// The loop should only execute one iteration in the common case.
   765  	var p []runtime.StackRecord
   766  	var labels []unsafe.Pointer
   767  	n, ok := fetch(nil, nil)
   768  	for {
   769  		// Allocate room for a slightly bigger profile,
   770  		// in case a few more entries have been added
   771  		// since the call to ThreadProfile.
   772  		p = make([]runtime.StackRecord, n+10)
   773  		labels = make([]unsafe.Pointer, n+10)
   774  		n, ok = fetch(p, labels)
   775  		if ok {
   776  			p = p[0:n]
   777  			break
   778  		}
   779  		// Profile grew; try again.
   780  	}
   781  
   782  	return printCountProfile(w, debug, name, &runtimeProfile{p, labels})
   783  }
   784  
   785  type runtimeProfile struct {
   786  	stk    []runtime.StackRecord
   787  	labels []unsafe.Pointer
   788  }
   789  
   790  func (p *runtimeProfile) Len() int              { return len(p.stk) }
   791  func (p *runtimeProfile) Stack(i int) []uintptr { return p.stk[i].Stack() }
   792  func (p *runtimeProfile) Label(i int) *labelMap { return (*labelMap)(p.labels[i]) }
   793  
   794  var cpu struct {
   795  	sync.Mutex
   796  	profiling bool
   797  	done      chan bool
   798  }
   799  
   800  // StartCPUProfile enables CPU profiling for the current process.
   801  // While profiling, the profile will be buffered and written to w.
   802  // StartCPUProfile returns an error if profiling is already enabled.
   803  //
   804  // On Unix-like systems, StartCPUProfile does not work by default for
   805  // Go code built with -buildmode=c-archive or -buildmode=c-shared.
   806  // StartCPUProfile relies on the SIGPROF signal, but that signal will
   807  // be delivered to the main program's SIGPROF signal handler (if any)
   808  // not to the one used by Go. To make it work, call [os/signal.Notify]
   809  // for [syscall.SIGPROF], but note that doing so may break any profiling
   810  // being done by the main program.
   811  func StartCPUProfile(w io.Writer) error {
   812  	// The runtime routines allow a variable profiling rate,
   813  	// but in practice operating systems cannot trigger signals
   814  	// at more than about 500 Hz, and our processing of the
   815  	// signal is not cheap (mostly getting the stack trace).
   816  	// 100 Hz is a reasonable choice: it is frequent enough to
   817  	// produce useful data, rare enough not to bog down the
   818  	// system, and a nice round number to make it easy to
   819  	// convert sample counts to seconds. Instead of requiring
   820  	// each client to specify the frequency, we hard code it.
   821  	const hz = 100
   822  
   823  	cpu.Lock()
   824  	defer cpu.Unlock()
   825  	if cpu.done == nil {
   826  		cpu.done = make(chan bool)
   827  	}
   828  	// Double-check.
   829  	if cpu.profiling {
   830  		return fmt.Errorf("cpu profiling already in use")
   831  	}
   832  	cpu.profiling = true
   833  	runtime.SetCPUProfileRate(hz)
   834  	go profileWriter(w)
   835  	return nil
   836  }
   837  
   838  // readProfile, provided by the runtime, returns the next chunk of
   839  // binary CPU profiling stack trace data, blocking until data is available.
   840  // If profiling is turned off and all the profile data accumulated while it was
   841  // on has been returned, readProfile returns eof=true.
   842  // The caller must save the returned data and tags before calling readProfile again.
   843  func readProfile() (data []uint64, tags []unsafe.Pointer, eof bool)
   844  
   845  func profileWriter(w io.Writer) {
   846  	b := newProfileBuilder(w)
   847  	var err error
   848  	for {
   849  		time.Sleep(100 * time.Millisecond)
   850  		data, tags, eof := readProfile()
   851  		if e := b.addCPUData(data, tags); e != nil && err == nil {
   852  			err = e
   853  		}
   854  		if eof {
   855  			break
   856  		}
   857  	}
   858  	if err != nil {
   859  		// The runtime should never produce an invalid or truncated profile.
   860  		// It drops records that can't fit into its log buffers.
   861  		panic("runtime/pprof: converting profile: " + err.Error())
   862  	}
   863  	b.build()
   864  	cpu.done <- true
   865  }
   866  
   867  // StopCPUProfile stops the current CPU profile, if any.
   868  // StopCPUProfile only returns after all the writes for the
   869  // profile have completed.
   870  func StopCPUProfile() {
   871  	cpu.Lock()
   872  	defer cpu.Unlock()
   873  
   874  	if !cpu.profiling {
   875  		return
   876  	}
   877  	cpu.profiling = false
   878  	runtime.SetCPUProfileRate(0)
   879  	<-cpu.done
   880  }
   881  
   882  // countBlock returns the number of records in the blocking profile.
   883  func countBlock() int {
   884  	n, _ := runtime.BlockProfile(nil)
   885  	return n
   886  }
   887  
   888  // countMutex returns the number of records in the mutex profile.
   889  func countMutex() int {
   890  	n, _ := runtime.MutexProfile(nil)
   891  	return n
   892  }
   893  
   894  // writeBlock writes the current blocking profile to w.
   895  func writeBlock(w io.Writer, debug int) error {
   896  	return writeProfileInternal(w, debug, "contention", runtime.BlockProfile)
   897  }
   898  
   899  // writeMutex writes the current mutex profile to w.
   900  func writeMutex(w io.Writer, debug int) error {
   901  	return writeProfileInternal(w, debug, "mutex", runtime.MutexProfile)
   902  }
   903  
   904  // writeProfileInternal writes the current blocking or mutex profile depending on the passed parameters.
   905  func writeProfileInternal(w io.Writer, debug int, name string, runtimeProfile func([]runtime.BlockProfileRecord) (int, bool)) error {
   906  	var p []runtime.BlockProfileRecord
   907  	n, ok := runtimeProfile(nil)
   908  	for {
   909  		p = make([]runtime.BlockProfileRecord, n+50)
   910  		n, ok = runtimeProfile(p)
   911  		if ok {
   912  			p = p[:n]
   913  			break
   914  		}
   915  	}
   916  
   917  	sort.Slice(p, func(i, j int) bool { return p[i].Cycles > p[j].Cycles })
   918  
   919  	if debug <= 0 {
   920  		return printCountCycleProfile(w, "contentions", "delay", p)
   921  	}
   922  
   923  	b := bufio.NewWriter(w)
   924  	tw := tabwriter.NewWriter(w, 1, 8, 1, '\t', 0)
   925  	w = tw
   926  
   927  	fmt.Fprintf(w, "--- %v:\n", name)
   928  	fmt.Fprintf(w, "cycles/second=%v\n", runtime_cyclesPerSecond())
   929  	if name == "mutex" {
   930  		fmt.Fprintf(w, "sampling period=%d\n", runtime.SetMutexProfileFraction(-1))
   931  	}
   932  	for i := range p {
   933  		r := &p[i]
   934  		fmt.Fprintf(w, "%v %v @", r.Cycles, r.Count)
   935  		for _, pc := range r.Stack() {
   936  			fmt.Fprintf(w, " %#x", pc)
   937  		}
   938  		fmt.Fprint(w, "\n")
   939  		if debug > 0 {
   940  			printStackRecord(w, r.Stack(), true)
   941  		}
   942  	}
   943  
   944  	if tw != nil {
   945  		tw.Flush()
   946  	}
   947  	return b.Flush()
   948  }
   949  
   950  func runtime_cyclesPerSecond() int64
   951  

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