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() 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() 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 prints only the hexadecimal addresses that pprof needs. 317 // Passing debug=1 adds comments translating addresses to function names 318 // and line numbers, so that a programmer can read the profile without tools. 319 // 320 // The predefined profiles may assign meaning to other debug values; 321 // for example, when printing the "goroutine" profile, debug=2 means to 322 // print the goroutine stacks in the same form that a Go program uses 323 // when dying due to an unrecovered panic. 324 func (p *Profile) WriteTo(w io.Writer, debug int) error { 325 if p.name == "" { 326 panic("pprof: use of zero Profile") 327 } 328 if p.write != nil { 329 return p.write(w, debug) 330 } 331 332 // Obtain consistent snapshot under lock; then process without lock. 333 p.mu.Lock() 334 all := make([][]uintptr, 0, len(p.m)) 335 for _, stk := range p.m { 336 all = append(all, stk) 337 } 338 p.mu.Unlock() 339 340 // Map order is non-deterministic; make output deterministic. 341 sort.Slice(all, func(i, j int) bool { 342 t, u := all[i], all[j] 343 for k := 0; k < len(t) && k < len(u); k++ { 344 if t[k] != u[k] { 345 return t[k] < u[k] 346 } 347 } 348 return len(t) < len(u) 349 }) 350 351 return printCountProfile(w, debug, p.name, stackProfile(all)) 352 } 353 354 type stackProfile [][]uintptr 355 356 func (x stackProfile) Len() int { return len(x) } 357 func (x stackProfile) Stack(i int) []uintptr { return x[i] } 358 359 // A countProfile is a set of stack traces to be printed as counts 360 // grouped by stack trace. There are multiple implementations: 361 // all that matters is that we can find out how many traces there are 362 // and obtain each trace in turn. 363 type countProfile interface { 364 Len() int 365 Stack(i int) []uintptr 366 } 367 368 // printCountCycleProfile outputs block profile records (for block or mutex profiles) 369 // as the pprof-proto format output. Translations from cycle count to time duration 370 // are done because The proto expects count and time (nanoseconds) instead of count 371 // and the number of cycles for block, contention profiles. 372 // Possible 'scaler' functions are scaleBlockProfile and scaleMutexProfile. 373 func printCountCycleProfile(w io.Writer, countName, cycleName string, scaler func(int64, float64) (int64, float64), records []runtime.BlockProfileRecord) error { 374 // Output profile in protobuf form. 375 b := newProfileBuilder(w) 376 b.pbValueType(tagProfile_PeriodType, countName, "count") 377 b.pb.int64Opt(tagProfile_Period, 1) 378 b.pbValueType(tagProfile_SampleType, countName, "count") 379 b.pbValueType(tagProfile_SampleType, cycleName, "nanoseconds") 380 381 cpuGHz := float64(runtime_cyclesPerSecond()) / 1e9 382 383 values := []int64{0, 0} 384 var locs []uint64 385 for _, r := range records { 386 count, nanosec := scaler(r.Count, float64(r.Cycles)/cpuGHz) 387 values[0] = count 388 values[1] = int64(nanosec) 389 locs = locs[:0] 390 for _, addr := range r.Stack() { 391 // For count profiles, all stack addresses are 392 // return PCs, which is what locForPC expects. 393 l := b.locForPC(addr) 394 if l == 0 { // runtime.goexit 395 continue 396 } 397 locs = append(locs, l) 398 } 399 b.pbSample(values, locs, nil) 400 } 401 b.build() 402 return nil 403 } 404 405 // printCountProfile prints a countProfile at the specified debug level. 406 // The profile will be in compressed proto format unless debug is nonzero. 407 func printCountProfile(w io.Writer, debug int, name string, p countProfile) error { 408 // Build count of each stack. 409 var buf bytes.Buffer 410 key := func(stk []uintptr) string { 411 buf.Reset() 412 fmt.Fprintf(&buf, "@") 413 for _, pc := range stk { 414 fmt.Fprintf(&buf, " %#x", pc) 415 } 416 return buf.String() 417 } 418 count := map[string]int{} 419 index := map[string]int{} 420 var keys []string 421 n := p.Len() 422 for i := 0; i < n; i++ { 423 k := key(p.Stack(i)) 424 if count[k] == 0 { 425 index[k] = i 426 keys = append(keys, k) 427 } 428 count[k]++ 429 } 430 431 sort.Sort(&keysByCount{keys, count}) 432 433 if debug > 0 { 434 // Print debug profile in legacy format 435 tw := tabwriter.NewWriter(w, 1, 8, 1, '\t', 0) 436 fmt.Fprintf(tw, "%s profile: total %d\n", name, p.Len()) 437 for _, k := range keys { 438 fmt.Fprintf(tw, "%d %s\n", count[k], k) 439 printStackRecord(tw, p.Stack(index[k]), false) 440 } 441 return tw.Flush() 442 } 443 444 // Output profile in protobuf form. 445 b := newProfileBuilder(w) 446 b.pbValueType(tagProfile_PeriodType, name, "count") 447 b.pb.int64Opt(tagProfile_Period, 1) 448 b.pbValueType(tagProfile_SampleType, name, "count") 449 450 values := []int64{0} 451 var locs []uint64 452 for _, k := range keys { 453 values[0] = int64(count[k]) 454 locs = locs[:0] 455 for _, addr := range p.Stack(index[k]) { 456 // For count profiles, all stack addresses are 457 // return PCs, which is what locForPC expects. 458 l := b.locForPC(addr) 459 if l == 0 { // runtime.goexit 460 continue 461 } 462 locs = append(locs, l) 463 } 464 b.pbSample(values, locs, nil) 465 } 466 b.build() 467 return nil 468 } 469 470 // keysByCount sorts keys with higher counts first, breaking ties by key string order. 471 type keysByCount struct { 472 keys []string 473 count map[string]int 474 } 475 476 func (x *keysByCount) Len() int { return len(x.keys) } 477 func (x *keysByCount) Swap(i, j int) { x.keys[i], x.keys[j] = x.keys[j], x.keys[i] } 478 func (x *keysByCount) Less(i, j int) bool { 479 ki, kj := x.keys[i], x.keys[j] 480 ci, cj := x.count[ki], x.count[kj] 481 if ci != cj { 482 return ci > cj 483 } 484 return ki < kj 485 } 486 487 // printStackRecord prints the function + source line information 488 // for a single stack trace. 489 func printStackRecord(w io.Writer, stk []uintptr, allFrames bool) { 490 show := allFrames 491 frames := runtime.CallersFrames(stk) 492 for { 493 frame, more := frames.Next() 494 name := frame.Function 495 if name == "" { 496 show = true 497 fmt.Fprintf(w, "#\t%#x\n", frame.PC) 498 } else if name != "runtime.goexit" && (show || !strings.HasPrefix(name, "runtime.")) { 499 // Hide runtime.goexit and any runtime functions at the beginning. 500 // This is useful mainly for allocation traces. 501 show = true 502 fmt.Fprintf(w, "#\t%#x\t%s+%#x\t%s:%d\n", frame.PC, name, frame.PC-frame.Entry, frame.File, frame.Line) 503 } 504 if !more { 505 break 506 } 507 } 508 if !show { 509 // We didn't print anything; do it again, 510 // and this time include runtime functions. 511 printStackRecord(w, stk, true) 512 return 513 } 514 fmt.Fprintf(w, "\n") 515 } 516 517 // Interface to system profiles. 518 519 // WriteHeapProfile is shorthand for Lookup("heap").WriteTo(w, 0). 520 // It is preserved for backwards compatibility. 521 func WriteHeapProfile(w io.Writer) error { 522 return writeHeap(w, 0) 523 } 524 525 // countHeap returns the number of records in the heap profile. 526 func countHeap() int { 527 n, _ := runtime.MemProfile(nil, true) 528 return n 529 } 530 531 // writeHeap writes the current runtime heap profile to w. 532 func writeHeap(w io.Writer, debug int) error { 533 return writeHeapInternal(w, debug, "") 534 } 535 536 // writeAlloc writes the current runtime heap profile to w 537 // with the total allocation space as the default sample type. 538 func writeAlloc(w io.Writer, debug int) error { 539 return writeHeapInternal(w, debug, "alloc_space") 540 } 541 542 func writeHeapInternal(w io.Writer, debug int, defaultSampleType string) error { 543 var memStats *runtime.MemStats 544 if debug != 0 { 545 // Read mem stats first, so that our other allocations 546 // do not appear in the statistics. 547 memStats = new(runtime.MemStats) 548 runtime.ReadMemStats(memStats) 549 } 550 551 // Find out how many records there are (MemProfile(nil, true)), 552 // allocate that many records, and get the data. 553 // There's a race—more records might be added between 554 // the two calls—so allocate a few extra records for safety 555 // and also try again if we're very unlucky. 556 // The loop should only execute one iteration in the common case. 557 var p []runtime.MemProfileRecord 558 n, ok := runtime.MemProfile(nil, true) 559 for { 560 // Allocate room for a slightly bigger profile, 561 // in case a few more entries have been added 562 // since the call to MemProfile. 563 p = make([]runtime.MemProfileRecord, n+50) 564 n, ok = runtime.MemProfile(p, true) 565 if ok { 566 p = p[0:n] 567 break 568 } 569 // Profile grew; try again. 570 } 571 572 if debug == 0 { 573 return writeHeapProto(w, p, int64(runtime.MemProfileRate), defaultSampleType) 574 } 575 576 sort.Slice(p, func(i, j int) bool { return p[i].InUseBytes() > p[j].InUseBytes() }) 577 578 b := bufio.NewWriter(w) 579 tw := tabwriter.NewWriter(b, 1, 8, 1, '\t', 0) 580 w = tw 581 582 var total runtime.MemProfileRecord 583 for i := range p { 584 r := &p[i] 585 total.AllocBytes += r.AllocBytes 586 total.AllocObjects += r.AllocObjects 587 total.FreeBytes += r.FreeBytes 588 total.FreeObjects += r.FreeObjects 589 } 590 591 // Technically the rate is MemProfileRate not 2*MemProfileRate, 592 // but early versions of the C++ heap profiler reported 2*MemProfileRate, 593 // so that's what pprof has come to expect. 594 fmt.Fprintf(w, "heap profile: %d: %d [%d: %d] @ heap/%d\n", 595 total.InUseObjects(), total.InUseBytes(), 596 total.AllocObjects, total.AllocBytes, 597 2*runtime.MemProfileRate) 598 599 for i := range p { 600 r := &p[i] 601 fmt.Fprintf(w, "%d: %d [%d: %d] @", 602 r.InUseObjects(), r.InUseBytes(), 603 r.AllocObjects, r.AllocBytes) 604 for _, pc := range r.Stack() { 605 fmt.Fprintf(w, " %#x", pc) 606 } 607 fmt.Fprintf(w, "\n") 608 printStackRecord(w, r.Stack(), false) 609 } 610 611 // Print memstats information too. 612 // Pprof will ignore, but useful for people 613 s := memStats 614 fmt.Fprintf(w, "\n# runtime.MemStats\n") 615 fmt.Fprintf(w, "# Alloc = %d\n", s.Alloc) 616 fmt.Fprintf(w, "# TotalAlloc = %d\n", s.TotalAlloc) 617 fmt.Fprintf(w, "# Sys = %d\n", s.Sys) 618 fmt.Fprintf(w, "# Lookups = %d\n", s.Lookups) 619 fmt.Fprintf(w, "# Mallocs = %d\n", s.Mallocs) 620 fmt.Fprintf(w, "# Frees = %d\n", s.Frees) 621 622 fmt.Fprintf(w, "# HeapAlloc = %d\n", s.HeapAlloc) 623 fmt.Fprintf(w, "# HeapSys = %d\n", s.HeapSys) 624 fmt.Fprintf(w, "# HeapIdle = %d\n", s.HeapIdle) 625 fmt.Fprintf(w, "# HeapInuse = %d\n", s.HeapInuse) 626 fmt.Fprintf(w, "# HeapReleased = %d\n", s.HeapReleased) 627 fmt.Fprintf(w, "# HeapObjects = %d\n", s.HeapObjects) 628 629 fmt.Fprintf(w, "# Stack = %d / %d\n", s.StackInuse, s.StackSys) 630 fmt.Fprintf(w, "# MSpan = %d / %d\n", s.MSpanInuse, s.MSpanSys) 631 fmt.Fprintf(w, "# MCache = %d / %d\n", s.MCacheInuse, s.MCacheSys) 632 fmt.Fprintf(w, "# BuckHashSys = %d\n", s.BuckHashSys) 633 fmt.Fprintf(w, "# GCSys = %d\n", s.GCSys) 634 fmt.Fprintf(w, "# OtherSys = %d\n", s.OtherSys) 635 636 fmt.Fprintf(w, "# NextGC = %d\n", s.NextGC) 637 fmt.Fprintf(w, "# LastGC = %d\n", s.LastGC) 638 fmt.Fprintf(w, "# PauseNs = %d\n", s.PauseNs) 639 fmt.Fprintf(w, "# PauseEnd = %d\n", s.PauseEnd) 640 fmt.Fprintf(w, "# NumGC = %d\n", s.NumGC) 641 fmt.Fprintf(w, "# NumForcedGC = %d\n", s.NumForcedGC) 642 fmt.Fprintf(w, "# GCCPUFraction = %v\n", s.GCCPUFraction) 643 fmt.Fprintf(w, "# DebugGC = %v\n", s.DebugGC) 644 645 tw.Flush() 646 return b.Flush() 647 } 648 649 // countThreadCreate returns the size of the current ThreadCreateProfile. 650 func countThreadCreate() int { 651 n, _ := runtime.ThreadCreateProfile(nil) 652 return n 653 } 654 655 // writeThreadCreate writes the current runtime ThreadCreateProfile to w. 656 func writeThreadCreate(w io.Writer, debug int) error { 657 return writeRuntimeProfile(w, debug, "threadcreate", runtime.ThreadCreateProfile) 658 } 659 660 // countGoroutine returns the number of goroutines. 661 func countGoroutine() int { 662 return runtime.NumGoroutine() 663 } 664 665 // writeGoroutine writes the current runtime GoroutineProfile to w. 666 func writeGoroutine(w io.Writer, debug int) error { 667 if debug >= 2 { 668 return writeGoroutineStacks(w) 669 } 670 return writeRuntimeProfile(w, debug, "goroutine", runtime.GoroutineProfile) 671 } 672 673 func writeGoroutineStacks(w io.Writer) error { 674 // We don't know how big the buffer needs to be to collect 675 // all the goroutines. Start with 1 MB and try a few times, doubling each time. 676 // Give up and use a truncated trace if 64 MB is not enough. 677 buf := make([]byte, 1<<20) 678 for i := 0; ; i++ { 679 n := runtime.Stack(buf, true) 680 if n < len(buf) { 681 buf = buf[:n] 682 break 683 } 684 if len(buf) >= 64<<20 { 685 // Filled 64 MB - stop there. 686 break 687 } 688 buf = make([]byte, 2*len(buf)) 689 } 690 _, err := w.Write(buf) 691 return err 692 } 693 694 func writeRuntimeProfile(w io.Writer, debug int, name string, fetch func([]runtime.StackRecord) (int, bool)) error { 695 // Find out how many records there are (fetch(nil)), 696 // allocate that many records, and get the data. 697 // There's a race—more records might be added between 698 // the two calls—so allocate a few extra records for safety 699 // and also try again if we're very unlucky. 700 // The loop should only execute one iteration in the common case. 701 var p []runtime.StackRecord 702 n, ok := fetch(nil) 703 for { 704 // Allocate room for a slightly bigger profile, 705 // in case a few more entries have been added 706 // since the call to ThreadProfile. 707 p = make([]runtime.StackRecord, n+10) 708 n, ok = fetch(p) 709 if ok { 710 p = p[0:n] 711 break 712 } 713 // Profile grew; try again. 714 } 715 716 return printCountProfile(w, debug, name, runtimeProfile(p)) 717 } 718 719 type runtimeProfile []runtime.StackRecord 720 721 func (p runtimeProfile) Len() int { return len(p) } 722 func (p runtimeProfile) Stack(i int) []uintptr { return p[i].Stack() } 723 724 var cpu struct { 725 sync.Mutex 726 profiling bool 727 done chan bool 728 } 729 730 // StartCPUProfile enables CPU profiling for the current process. 731 // While profiling, the profile will be buffered and written to w. 732 // StartCPUProfile returns an error if profiling is already enabled. 733 // 734 // On Unix-like systems, StartCPUProfile does not work by default for 735 // Go code built with -buildmode=c-archive or -buildmode=c-shared. 736 // StartCPUProfile relies on the SIGPROF signal, but that signal will 737 // be delivered to the main program's SIGPROF signal handler (if any) 738 // not to the one used by Go. To make it work, call os/signal.Notify 739 // for syscall.SIGPROF, but note that doing so may break any profiling 740 // being done by the main program. 741 func StartCPUProfile(w io.Writer) error { 742 // The runtime routines allow a variable profiling rate, 743 // but in practice operating systems cannot trigger signals 744 // at more than about 500 Hz, and our processing of the 745 // signal is not cheap (mostly getting the stack trace). 746 // 100 Hz is a reasonable choice: it is frequent enough to 747 // produce useful data, rare enough not to bog down the 748 // system, and a nice round number to make it easy to 749 // convert sample counts to seconds. Instead of requiring 750 // each client to specify the frequency, we hard code it. 751 const hz = 100 752 753 cpu.Lock() 754 defer cpu.Unlock() 755 if cpu.done == nil { 756 cpu.done = make(chan bool) 757 } 758 // Double-check. 759 if cpu.profiling { 760 return fmt.Errorf("cpu profiling already in use") 761 } 762 cpu.profiling = true 763 runtime.SetCPUProfileRate(hz) 764 go profileWriter(w) 765 return nil 766 } 767 768 // readProfile, provided by the runtime, returns the next chunk of 769 // binary CPU profiling stack trace data, blocking until data is available. 770 // If profiling is turned off and all the profile data accumulated while it was 771 // on has been returned, readProfile returns eof=true. 772 // The caller must save the returned data and tags before calling readProfile again. 773 func readProfile() (data []uint64, tags []unsafe.Pointer, eof bool) 774 775 func profileWriter(w io.Writer) { 776 b := newProfileBuilder(w) 777 var err error 778 for { 779 time.Sleep(100 * time.Millisecond) 780 data, tags, eof := readProfile() 781 if e := b.addCPUData(data, tags); e != nil && err == nil { 782 err = e 783 } 784 if eof { 785 break 786 } 787 } 788 if err != nil { 789 // The runtime should never produce an invalid or truncated profile. 790 // It drops records that can't fit into its log buffers. 791 panic("runtime/pprof: converting profile: " + err.Error()) 792 } 793 b.build() 794 cpu.done <- true 795 } 796 797 // StopCPUProfile stops the current CPU profile, if any. 798 // StopCPUProfile only returns after all the writes for the 799 // profile have completed. 800 func StopCPUProfile() { 801 cpu.Lock() 802 defer cpu.Unlock() 803 804 if !cpu.profiling { 805 return 806 } 807 cpu.profiling = false 808 runtime.SetCPUProfileRate(0) 809 <-cpu.done 810 } 811 812 // countBlock returns the number of records in the blocking profile. 813 func countBlock() int { 814 n, _ := runtime.BlockProfile(nil) 815 return n 816 } 817 818 // countMutex returns the number of records in the mutex profile. 819 func countMutex() int { 820 n, _ := runtime.MutexProfile(nil) 821 return n 822 } 823 824 // writeBlock writes the current blocking profile to w. 825 func writeBlock(w io.Writer, debug int) error { 826 var p []runtime.BlockProfileRecord 827 n, ok := runtime.BlockProfile(nil) 828 for { 829 p = make([]runtime.BlockProfileRecord, n+50) 830 n, ok = runtime.BlockProfile(p) 831 if ok { 832 p = p[:n] 833 break 834 } 835 } 836 837 sort.Slice(p, func(i, j int) bool { return p[i].Cycles > p[j].Cycles }) 838 839 if debug <= 0 { 840 return printCountCycleProfile(w, "contentions", "delay", scaleBlockProfile, p) 841 } 842 843 b := bufio.NewWriter(w) 844 tw := tabwriter.NewWriter(w, 1, 8, 1, '\t', 0) 845 w = tw 846 847 fmt.Fprintf(w, "--- contention:\n") 848 fmt.Fprintf(w, "cycles/second=%v\n", runtime_cyclesPerSecond()) 849 for i := range p { 850 r := &p[i] 851 fmt.Fprintf(w, "%v %v @", r.Cycles, r.Count) 852 for _, pc := range r.Stack() { 853 fmt.Fprintf(w, " %#x", pc) 854 } 855 fmt.Fprint(w, "\n") 856 if debug > 0 { 857 printStackRecord(w, r.Stack(), true) 858 } 859 } 860 861 if tw != nil { 862 tw.Flush() 863 } 864 return b.Flush() 865 } 866 867 func scaleBlockProfile(cnt int64, ns float64) (int64, float64) { 868 // Do nothing. 869 // The current way of block profile sampling makes it 870 // hard to compute the unsampled number. The legacy block 871 // profile parse doesn't attempt to scale or unsample. 872 return cnt, ns 873 } 874 875 // writeMutex writes the current mutex profile to w. 876 func writeMutex(w io.Writer, debug int) error { 877 // TODO(pjw): too much common code with writeBlock. FIX! 878 var p []runtime.BlockProfileRecord 879 n, ok := runtime.MutexProfile(nil) 880 for { 881 p = make([]runtime.BlockProfileRecord, n+50) 882 n, ok = runtime.MutexProfile(p) 883 if ok { 884 p = p[:n] 885 break 886 } 887 } 888 889 sort.Slice(p, func(i, j int) bool { return p[i].Cycles > p[j].Cycles }) 890 891 if debug <= 0 { 892 return printCountCycleProfile(w, "contentions", "delay", scaleMutexProfile, p) 893 } 894 895 b := bufio.NewWriter(w) 896 tw := tabwriter.NewWriter(w, 1, 8, 1, '\t', 0) 897 w = tw 898 899 fmt.Fprintf(w, "--- mutex:\n") 900 fmt.Fprintf(w, "cycles/second=%v\n", runtime_cyclesPerSecond()) 901 fmt.Fprintf(w, "sampling period=%d\n", runtime.SetMutexProfileFraction(-1)) 902 for i := range p { 903 r := &p[i] 904 fmt.Fprintf(w, "%v %v @", r.Cycles, r.Count) 905 for _, pc := range r.Stack() { 906 fmt.Fprintf(w, " %#x", pc) 907 } 908 fmt.Fprint(w, "\n") 909 if debug > 0 { 910 printStackRecord(w, r.Stack(), true) 911 } 912 } 913 914 if tw != nil { 915 tw.Flush() 916 } 917 return b.Flush() 918 } 919 920 func scaleMutexProfile(cnt int64, ns float64) (int64, float64) { 921 period := runtime.SetMutexProfileFraction(-1) 922 return cnt * int64(period), ns * float64(period) 923 } 924 925 func runtime_cyclesPerSecond() int64 926
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