1// Copyright 2009 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 5package testing 6 7import ( 8 "flag" 9 "fmt" 10 "internal/race" 11 "internal/sysinfo" 12 "io" 13 "math" 14 "os" 15 "runtime" 16 "sort" 17 "strconv" 18 "strings" 19 "sync" 20 "sync/atomic" 21 "time" 22 "unicode" 23) 24 25func initBenchmarkFlags() { 26 matchBenchmarks = flag.String("test.bench", "", "run only benchmarks matching `regexp`") 27 benchmarkMemory = flag.Bool("test.benchmem", false, "print memory allocations for benchmarks") 28 flag.Var(&benchTime, "test.benchtime", "run each benchmark for duration `d`") 29} 30 31var ( 32 matchBenchmarks *string 33 benchmarkMemory *bool 34 35 benchTime = durationOrCountFlag{d: 1 * time.Second} // changed during test of testing package 36) 37 38type durationOrCountFlag struct { 39 d time.Duration 40 n int 41 allowZero bool 42} 43 44func (f *durationOrCountFlag) String() string { 45 if f.n > 0 { 46 return fmt.Sprintf("%dx", f.n) 47 } 48 return f.d.String() 49} 50 51func (f *durationOrCountFlag) Set(s string) error { 52 if strings.HasSuffix(s, "x") { 53 n, err := strconv.ParseInt(s[:len(s)-1], 10, 0) 54 if err != nil || n < 0 || (!f.allowZero && n == 0) { 55 return fmt.Errorf("invalid count") 56 } 57 *f = durationOrCountFlag{n: int(n)} 58 return nil 59 } 60 d, err := time.ParseDuration(s) 61 if err != nil || d < 0 || (!f.allowZero && d == 0) { 62 return fmt.Errorf("invalid duration") 63 } 64 *f = durationOrCountFlag{d: d} 65 return nil 66} 67 68// Global lock to ensure only one benchmark runs at a time. 69var benchmarkLock sync.Mutex 70 71// Used for every benchmark for measuring memory. 72var memStats runtime.MemStats 73 74// InternalBenchmark is an internal type but exported because it is cross-package; 75// it is part of the implementation of the "go test" command. 76type InternalBenchmark struct { 77 Name string 78 F func(b *B) 79} 80 81// B is a type passed to Benchmark functions to manage benchmark 82// timing and to specify the number of iterations to run. 83// 84// A benchmark ends when its Benchmark function returns or calls any of the methods 85// FailNow, Fatal, Fatalf, SkipNow, Skip, or Skipf. Those methods must be called 86// only from the goroutine running the Benchmark function. 87// The other reporting methods, such as the variations of Log and Error, 88// may be called simultaneously from multiple goroutines. 89// 90// Like in tests, benchmark logs are accumulated during execution 91// and dumped to standard output when done. Unlike in tests, benchmark logs 92// are always printed, so as not to hide output whose existence may be 93// affecting benchmark results. 94type B struct { 95 common 96 importPath string // import path of the package containing the benchmark 97 context *benchContext 98 N int 99 previousN int // number of iterations in the previous run 100 previousDuration time.Duration // total duration of the previous run 101 benchFunc func(b *B) 102 benchTime durationOrCountFlag 103 bytes int64 104 missingBytes bool // one of the subbenchmarks does not have bytes set. 105 timerOn bool 106 showAllocResult bool 107 result BenchmarkResult 108 parallelism int // RunParallel creates parallelism*GOMAXPROCS goroutines 109 // The initial states of memStats.Mallocs and memStats.TotalAlloc. 110 startAllocs uint64 111 startBytes uint64 112 // The net total of this test after being run. 113 netAllocs uint64 114 netBytes uint64 115 // Extra metrics collected by ReportMetric. 116 extra map[string]float64 117} 118 119// StartTimer starts timing a test. This function is called automatically 120// before a benchmark starts, but it can also be used to resume timing after 121// a call to StopTimer. 122func (b *B) StartTimer() { 123 if !b.timerOn { 124 runtime.ReadMemStats(&memStats) 125 b.startAllocs = memStats.Mallocs 126 b.startBytes = memStats.TotalAlloc 127 b.start = time.Now() 128 b.timerOn = true 129 } 130} 131 132// StopTimer stops timing a test. This can be used to pause the timer 133// while performing complex initialization that you don't 134// want to measure. 135func (b *B) StopTimer() { 136 if b.timerOn { 137 b.duration += time.Since(b.start) 138 runtime.ReadMemStats(&memStats) 139 b.netAllocs += memStats.Mallocs - b.startAllocs 140 b.netBytes += memStats.TotalAlloc - b.startBytes 141 b.timerOn = false 142 } 143} 144 145// ResetTimer zeroes the elapsed benchmark time and memory allocation counters 146// and deletes user-reported metrics. 147// It does not affect whether the timer is running. 148func (b *B) ResetTimer() { 149 if b.extra == nil { 150 // Allocate the extra map before reading memory stats. 151 // Pre-size it to make more allocation unlikely. 152 b.extra = make(map[string]float64, 16) 153 } else { 154 for k := range b.extra { 155 delete(b.extra, k) 156 } 157 } 158 if b.timerOn { 159 runtime.ReadMemStats(&memStats) 160 b.startAllocs = memStats.Mallocs 161 b.startBytes = memStats.TotalAlloc 162 b.start = time.Now() 163 } 164 b.duration = 0 165 b.netAllocs = 0 166 b.netBytes = 0 167} 168 169// SetBytes records the number of bytes processed in a single operation. 170// If this is called, the benchmark will report ns/op and MB/s. 171func (b *B) SetBytes(n int64) { b.bytes = n } 172 173// ReportAllocs enables malloc statistics for this benchmark. 174// It is equivalent to setting -test.benchmem, but it only affects the 175// benchmark function that calls ReportAllocs. 176func (b *B) ReportAllocs() { 177 b.showAllocResult = true 178} 179 180// runN runs a single benchmark for the specified number of iterations. 181func (b *B) runN(n int) { 182 benchmarkLock.Lock() 183 defer benchmarkLock.Unlock() 184 defer b.runCleanup(normalPanic) 185 // Try to get a comparable environment for each run 186 // by clearing garbage from previous runs. 187 runtime.GC() 188 b.raceErrors = -race.Errors() 189 b.N = n 190 b.parallelism = 1 191 b.ResetTimer() 192 b.StartTimer() 193 b.benchFunc(b) 194 b.StopTimer() 195 b.previousN = n 196 b.previousDuration = b.duration 197 b.raceErrors += race.Errors() 198 if b.raceErrors > 0 { 199 b.Errorf("race detected during execution of benchmark") 200 } 201} 202 203func min(x, y int64) int64 { 204 if x > y { 205 return y 206 } 207 return x 208} 209 210func max(x, y int64) int64 { 211 if x < y { 212 return y 213 } 214 return x 215} 216 217// run1 runs the first iteration of benchFunc. It reports whether more 218// iterations of this benchmarks should be run. 219func (b *B) run1() bool { 220 if ctx := b.context; ctx != nil { 221 // Extend maxLen, if needed. 222 if n := len(b.name) + ctx.extLen + 1; n > ctx.maxLen { 223 ctx.maxLen = n + 8 // Add additional slack to avoid too many jumps in size. 224 } 225 } 226 go func() { 227 // Signal that we're done whether we return normally 228 // or by FailNow's runtime.Goexit. 229 defer func() { 230 b.signal <- true 231 }() 232 233 b.runN(1) 234 }() 235 <-b.signal 236 if b.failed { 237 fmt.Fprintf(b.w, "--- FAIL: %s\n%s", b.name, b.output) 238 return false 239 } 240 // Only print the output if we know we are not going to proceed. 241 // Otherwise it is printed in processBench. 242 b.mu.RLock() 243 finished := b.finished 244 b.mu.RUnlock() 245 if atomic.LoadInt32(&b.hasSub) != 0 || finished { 246 tag := "BENCH" 247 if b.skipped { 248 tag = "SKIP" 249 } 250 if b.chatty != nil && (len(b.output) > 0 || finished) { 251 b.trimOutput() 252 fmt.Fprintf(b.w, "--- %s: %s\n%s", tag, b.name, b.output) 253 } 254 return false 255 } 256 return true 257} 258 259var labelsOnce sync.Once 260 261// run executes the benchmark in a separate goroutine, including all of its 262// subbenchmarks. b must not have subbenchmarks. 263func (b *B) run() { 264 labelsOnce.Do(func() { 265 fmt.Fprintf(b.w, "goos: %s\n", runtime.GOOS) 266 fmt.Fprintf(b.w, "goarch: %s\n", runtime.GOARCH) 267 if b.importPath != "" { 268 fmt.Fprintf(b.w, "pkg: %s\n", b.importPath) 269 } 270 if cpu := sysinfo.CPU.Name(); cpu != "" { 271 fmt.Fprintf(b.w, "cpu: %s\n", cpu) 272 } 273 }) 274 if b.context != nil { 275 // Running go test --test.bench 276 b.context.processBench(b) // Must call doBench. 277 } else { 278 // Running func Benchmark. 279 b.doBench() 280 } 281} 282 283func (b *B) doBench() BenchmarkResult { 284 go b.launch() 285 <-b.signal 286 return b.result 287} 288 289// launch launches the benchmark function. It gradually increases the number 290// of benchmark iterations until the benchmark runs for the requested benchtime. 291// launch is run by the doBench function as a separate goroutine. 292// run1 must have been called on b. 293func (b *B) launch() { 294 // Signal that we're done whether we return normally 295 // or by FailNow's runtime.Goexit. 296 defer func() { 297 b.signal <- true 298 }() 299 300 // Run the benchmark for at least the specified amount of time. 301 if b.benchTime.n > 0 { 302 // We already ran a single iteration in run1. 303 // If -benchtime=1x was requested, use that result. 304 // See https://golang.org/issue/32051. 305 if b.benchTime.n > 1 { 306 b.runN(b.benchTime.n) 307 } 308 } else { 309 d := b.benchTime.d 310 for n := int64(1); !b.failed && b.duration < d && n < 1e9; { 311 last := n 312 // Predict required iterations. 313 goalns := d.Nanoseconds() 314 prevIters := int64(b.N) 315 prevns := b.duration.Nanoseconds() 316 if prevns <= 0 { 317 // Round up, to avoid div by zero. 318 prevns = 1 319 } 320 // Order of operations matters. 321 // For very fast benchmarks, prevIters ~= prevns. 322 // If you divide first, you get 0 or 1, 323 // which can hide an order of magnitude in execution time. 324 // So multiply first, then divide. 325 n = goalns * prevIters / prevns 326 // Run more iterations than we think we'll need (1.2x). 327 n += n / 5 328 // Don't grow too fast in case we had timing errors previously. 329 n = min(n, 100*last) 330 // Be sure to run at least one more than last time. 331 n = max(n, last+1) 332 // Don't run more than 1e9 times. (This also keeps n in int range on 32 bit platforms.) 333 n = min(n, 1e9) 334 b.runN(int(n)) 335 } 336 } 337 b.result = BenchmarkResult{b.N, b.duration, b.bytes, b.netAllocs, b.netBytes, b.extra} 338} 339 340// ReportMetric adds "n unit" to the reported benchmark results. 341// If the metric is per-iteration, the caller should divide by b.N, 342// and by convention units should end in "/op". 343// ReportMetric overrides any previously reported value for the same unit. 344// ReportMetric panics if unit is the empty string or if unit contains 345// any whitespace. 346// If unit is a unit normally reported by the benchmark framework itself 347// (such as "allocs/op"), ReportMetric will override that metric. 348// Setting "ns/op" to 0 will suppress that built-in metric. 349func (b *B) ReportMetric(n float64, unit string) { 350 if unit == "" { 351 panic("metric unit must not be empty") 352 } 353 if strings.IndexFunc(unit, unicode.IsSpace) >= 0 { 354 panic("metric unit must not contain whitespace") 355 } 356 b.extra[unit] = n 357} 358 359// BenchmarkResult contains the results of a benchmark run. 360type BenchmarkResult struct { 361 N int // The number of iterations. 362 T time.Duration // The total time taken. 363 Bytes int64 // Bytes processed in one iteration. 364 MemAllocs uint64 // The total number of memory allocations. 365 MemBytes uint64 // The total number of bytes allocated. 366 367 // Extra records additional metrics reported by ReportMetric. 368 Extra map[string]float64 369} 370 371// NsPerOp returns the "ns/op" metric. 372func (r BenchmarkResult) NsPerOp() int64 { 373 if v, ok := r.Extra["ns/op"]; ok { 374 return int64(v) 375 } 376 if r.N <= 0 { 377 return 0 378 } 379 return r.T.Nanoseconds() / int64(r.N) 380} 381 382// mbPerSec returns the "MB/s" metric. 383func (r BenchmarkResult) mbPerSec() float64 { 384 if v, ok := r.Extra["MB/s"]; ok { 385 return v 386 } 387 if r.Bytes <= 0 || r.T <= 0 || r.N <= 0 { 388 return 0 389 } 390 return (float64(r.Bytes) * float64(r.N) / 1e6) / r.T.Seconds() 391} 392 393// AllocsPerOp returns the "allocs/op" metric, 394// which is calculated as r.MemAllocs / r.N. 395func (r BenchmarkResult) AllocsPerOp() int64 { 396 if v, ok := r.Extra["allocs/op"]; ok { 397 return int64(v) 398 } 399 if r.N <= 0 { 400 return 0 401 } 402 return int64(r.MemAllocs) / int64(r.N) 403} 404 405// AllocedBytesPerOp returns the "B/op" metric, 406// which is calculated as r.MemBytes / r.N. 407func (r BenchmarkResult) AllocedBytesPerOp() int64 { 408 if v, ok := r.Extra["B/op"]; ok { 409 return int64(v) 410 } 411 if r.N <= 0 { 412 return 0 413 } 414 return int64(r.MemBytes) / int64(r.N) 415} 416 417// String returns a summary of the benchmark results. 418// It follows the benchmark result line format from 419// https://golang.org/design/14313-benchmark-format, not including the 420// benchmark name. 421// Extra metrics override built-in metrics of the same name. 422// String does not include allocs/op or B/op, since those are reported 423// by MemString. 424func (r BenchmarkResult) String() string { 425 buf := new(strings.Builder) 426 fmt.Fprintf(buf, "%8d", r.N) 427 428 // Get ns/op as a float. 429 ns, ok := r.Extra["ns/op"] 430 if !ok { 431 ns = float64(r.T.Nanoseconds()) / float64(r.N) 432 } 433 if ns != 0 { 434 buf.WriteByte('\t') 435 prettyPrint(buf, ns, "ns/op") 436 } 437 438 if mbs := r.mbPerSec(); mbs != 0 { 439 fmt.Fprintf(buf, "\t%7.2f MB/s", mbs) 440 } 441 442 // Print extra metrics that aren't represented in the standard 443 // metrics. 444 var extraKeys []string 445 for k := range r.Extra { 446 switch k { 447 case "ns/op", "MB/s", "B/op", "allocs/op": 448 // Built-in metrics reported elsewhere. 449 continue 450 } 451 extraKeys = append(extraKeys, k) 452 } 453 sort.Strings(extraKeys) 454 for _, k := range extraKeys { 455 buf.WriteByte('\t') 456 prettyPrint(buf, r.Extra[k], k) 457 } 458 return buf.String() 459} 460 461func prettyPrint(w io.Writer, x float64, unit string) { 462 // Print all numbers with 10 places before the decimal point 463 // and small numbers with four sig figs. Field widths are 464 // chosen to fit the whole part in 10 places while aligning 465 // the decimal point of all fractional formats. 466 var format string 467 switch y := math.Abs(x); { 468 case y == 0 || y >= 999.95: 469 format = "%10.0f %s" 470 case y >= 99.995: 471 format = "%12.1f %s" 472 case y >= 9.9995: 473 format = "%13.2f %s" 474 case y >= 0.99995: 475 format = "%14.3f %s" 476 case y >= 0.099995: 477 format = "%15.4f %s" 478 case y >= 0.0099995: 479 format = "%16.5f %s" 480 case y >= 0.00099995: 481 format = "%17.6f %s" 482 default: 483 format = "%18.7f %s" 484 } 485 fmt.Fprintf(w, format, x, unit) 486} 487 488// MemString returns r.AllocedBytesPerOp and r.AllocsPerOp in the same format as 'go test'. 489func (r BenchmarkResult) MemString() string { 490 return fmt.Sprintf("%8d B/op\t%8d allocs/op", 491 r.AllocedBytesPerOp(), r.AllocsPerOp()) 492} 493 494// benchmarkName returns full name of benchmark including procs suffix. 495func benchmarkName(name string, n int) string { 496 if n != 1 { 497 return fmt.Sprintf("%s-%d", name, n) 498 } 499 return name 500} 501 502type benchContext struct { 503 match *matcher 504 505 maxLen int // The largest recorded benchmark name. 506 extLen int // Maximum extension length. 507} 508 509// RunBenchmarks is an internal function but exported because it is cross-package; 510// it is part of the implementation of the "go test" command. 511func RunBenchmarks(matchString func(pat, str string) (bool, error), benchmarks []InternalBenchmark) { 512 runBenchmarks("", matchString, benchmarks) 513} 514 515func runBenchmarks(importPath string, matchString func(pat, str string) (bool, error), benchmarks []InternalBenchmark) bool { 516 // If no flag was specified, don't run benchmarks. 517 if len(*matchBenchmarks) == 0 { 518 return true 519 } 520 // Collect matching benchmarks and determine longest name. 521 maxprocs := 1 522 for _, procs := range cpuList { 523 if procs > maxprocs { 524 maxprocs = procs 525 } 526 } 527 ctx := &benchContext{ 528 match: newMatcher(matchString, *matchBenchmarks, "-test.bench"), 529 extLen: len(benchmarkName("", maxprocs)), 530 } 531 var bs []InternalBenchmark 532 for _, Benchmark := range benchmarks { 533 if _, matched, _ := ctx.match.fullName(nil, Benchmark.Name); matched { 534 bs = append(bs, Benchmark) 535 benchName := benchmarkName(Benchmark.Name, maxprocs) 536 if l := len(benchName) + ctx.extLen + 1; l > ctx.maxLen { 537 ctx.maxLen = l 538 } 539 } 540 } 541 main := &B{ 542 common: common{ 543 name: "Main", 544 w: os.Stdout, 545 bench: true, 546 }, 547 importPath: importPath, 548 benchFunc: func(b *B) { 549 for _, Benchmark := range bs { 550 b.Run(Benchmark.Name, Benchmark.F) 551 } 552 }, 553 benchTime: benchTime, 554 context: ctx, 555 } 556 if Verbose() { 557 main.chatty = newChattyPrinter(main.w) 558 } 559 main.runN(1) 560 return !main.failed 561} 562 563// processBench runs bench b for the configured CPU counts and prints the results. 564func (ctx *benchContext) processBench(b *B) { 565 for i, procs := range cpuList { 566 for j := uint(0); j < *count; j++ { 567 runtime.GOMAXPROCS(procs) 568 benchName := benchmarkName(b.name, procs) 569 570 // If it's chatty, we've already printed this information. 571 if b.chatty == nil { 572 fmt.Fprintf(b.w, "%-*s\t", ctx.maxLen, benchName) 573 } 574 // Recompute the running time for all but the first iteration. 575 if i > 0 || j > 0 { 576 b = &B{ 577 common: common{ 578 signal: make(chan bool), 579 name: b.name, 580 w: b.w, 581 chatty: b.chatty, 582 bench: true, 583 }, 584 benchFunc: b.benchFunc, 585 benchTime: b.benchTime, 586 } 587 b.run1() 588 } 589 r := b.doBench() 590 if b.failed { 591 // The output could be very long here, but probably isn't. 592 // We print it all, regardless, because we don't want to trim the reason 593 // the benchmark failed. 594 fmt.Fprintf(b.w, "--- FAIL: %s\n%s", benchName, b.output) 595 continue 596 } 597 results := r.String() 598 if b.chatty != nil { 599 fmt.Fprintf(b.w, "%-*s\t", ctx.maxLen, benchName) 600 } 601 if *benchmarkMemory || b.showAllocResult { 602 results += "\t" + r.MemString() 603 } 604 fmt.Fprintln(b.w, results) 605 // Unlike with tests, we ignore the -chatty flag and always print output for 606 // benchmarks since the output generation time will skew the results. 607 if len(b.output) > 0 { 608 b.trimOutput() 609 fmt.Fprintf(b.w, "--- BENCH: %s\n%s", benchName, b.output) 610 } 611 if p := runtime.GOMAXPROCS(-1); p != procs { 612 fmt.Fprintf(os.Stderr, "testing: %s left GOMAXPROCS set to %d\n", benchName, p) 613 } 614 } 615 } 616} 617 618// Run benchmarks f as a subbenchmark with the given name. It reports 619// whether there were any failures. 620// 621// A subbenchmark is like any other benchmark. A benchmark that calls Run at 622// least once will not be measured itself and will be called once with N=1. 623func (b *B) Run(name string, f func(b *B)) bool { 624 // Since b has subbenchmarks, we will no longer run it as a benchmark itself. 625 // Release the lock and acquire it on exit to ensure locks stay paired. 626 atomic.StoreInt32(&b.hasSub, 1) 627 benchmarkLock.Unlock() 628 defer benchmarkLock.Lock() 629 630 benchName, ok, partial := b.name, true, false 631 if b.context != nil { 632 benchName, ok, partial = b.context.match.fullName(&b.common, name) 633 } 634 if !ok { 635 return true 636 } 637 var pc [maxStackLen]uintptr 638 n := runtime.Callers(2, pc[:]) 639 sub := &B{ 640 common: common{ 641 signal: make(chan bool), 642 name: benchName, 643 parent: &b.common, 644 level: b.level + 1, 645 creator: pc[:n], 646 w: b.w, 647 chatty: b.chatty, 648 bench: true, 649 }, 650 importPath: b.importPath, 651 benchFunc: f, 652 benchTime: b.benchTime, 653 context: b.context, 654 } 655 if partial { 656 // Partial name match, like -bench=X/Y matching BenchmarkX. 657 // Only process sub-benchmarks, if any. 658 atomic.StoreInt32(&sub.hasSub, 1) 659 } 660 661 if b.chatty != nil { 662 labelsOnce.Do(func() { 663 fmt.Printf("goos: %s\n", runtime.GOOS) 664 fmt.Printf("goarch: %s\n", runtime.GOARCH) 665 if b.importPath != "" { 666 fmt.Printf("pkg: %s\n", b.importPath) 667 } 668 if cpu := sysinfo.CPU.Name(); cpu != "" { 669 fmt.Printf("cpu: %s\n", cpu) 670 } 671 }) 672 673 fmt.Println(benchName) 674 } 675 676 if sub.run1() { 677 sub.run() 678 } 679 b.add(sub.result) 680 return !sub.failed 681} 682 683// add simulates running benchmarks in sequence in a single iteration. It is 684// used to give some meaningful results in case func Benchmark is used in 685// combination with Run. 686func (b *B) add(other BenchmarkResult) { 687 r := &b.result 688 // The aggregated BenchmarkResults resemble running all subbenchmarks as 689 // in sequence in a single benchmark. 690 r.N = 1 691 r.T += time.Duration(other.NsPerOp()) 692 if other.Bytes == 0 { 693 // Summing Bytes is meaningless in aggregate if not all subbenchmarks 694 // set it. 695 b.missingBytes = true 696 r.Bytes = 0 697 } 698 if !b.missingBytes { 699 r.Bytes += other.Bytes 700 } 701 r.MemAllocs += uint64(other.AllocsPerOp()) 702 r.MemBytes += uint64(other.AllocedBytesPerOp()) 703} 704 705// trimOutput shortens the output from a benchmark, which can be very long. 706func (b *B) trimOutput() { 707 // The output is likely to appear multiple times because the benchmark 708 // is run multiple times, but at least it will be seen. This is not a big deal 709 // because benchmarks rarely print, but just in case, we trim it if it's too long. 710 const maxNewlines = 10 711 for nlCount, j := 0, 0; j < len(b.output); j++ { 712 if b.output[j] == '\n' { 713 nlCount++ 714 if nlCount >= maxNewlines { 715 b.output = append(b.output[:j], "\n\t... [output truncated]\n"...) 716 break 717 } 718 } 719 } 720} 721 722// A PB is used by RunParallel for running parallel benchmarks. 723type PB struct { 724 globalN *uint64 // shared between all worker goroutines iteration counter 725 grain uint64 // acquire that many iterations from globalN at once 726 cache uint64 // local cache of acquired iterations 727 bN uint64 // total number of iterations to execute (b.N) 728} 729 730// Next reports whether there are more iterations to execute. 731func (pb *PB) Next() bool { 732 if pb.cache == 0 { 733 n := atomic.AddUint64(pb.globalN, pb.grain) 734 if n <= pb.bN { 735 pb.cache = pb.grain 736 } else if n < pb.bN+pb.grain { 737 pb.cache = pb.bN + pb.grain - n 738 } else { 739 return false 740 } 741 } 742 pb.cache-- 743 return true 744} 745 746// RunParallel runs a benchmark in parallel. 747// It creates multiple goroutines and distributes b.N iterations among them. 748// The number of goroutines defaults to GOMAXPROCS. To increase parallelism for 749// non-CPU-bound benchmarks, call SetParallelism before RunParallel. 750// RunParallel is usually used with the go test -cpu flag. 751// 752// The body function will be run in each goroutine. It should set up any 753// goroutine-local state and then iterate until pb.Next returns false. 754// It should not use the StartTimer, StopTimer, or ResetTimer functions, 755// because they have global effect. It should also not call Run. 756func (b *B) RunParallel(body func(*PB)) { 757 if b.N == 0 { 758 return // Nothing to do when probing. 759 } 760 // Calculate grain size as number of iterations that take ~100µs. 761 // 100µs is enough to amortize the overhead and provide sufficient 762 // dynamic load balancing. 763 grain := uint64(0) 764 if b.previousN > 0 && b.previousDuration > 0 { 765 grain = 1e5 * uint64(b.previousN) / uint64(b.previousDuration) 766 } 767 if grain < 1 { 768 grain = 1 769 } 770 // We expect the inner loop and function call to take at least 10ns, 771 // so do not do more than 100µs/10ns=1e4 iterations. 772 if grain > 1e4 { 773 grain = 1e4 774 } 775 776 n := uint64(0) 777 numProcs := b.parallelism * runtime.GOMAXPROCS(0) 778 var wg sync.WaitGroup 779 wg.Add(numProcs) 780 for p := 0; p < numProcs; p++ { 781 go func() { 782 defer wg.Done() 783 pb := &PB{ 784 globalN: &n, 785 grain: grain, 786 bN: uint64(b.N), 787 } 788 body(pb) 789 }() 790 } 791 wg.Wait() 792 if n <= uint64(b.N) && !b.Failed() { 793 b.Fatal("RunParallel: body exited without pb.Next() == false") 794 } 795} 796 797// SetParallelism sets the number of goroutines used by RunParallel to p*GOMAXPROCS. 798// There is usually no need to call SetParallelism for CPU-bound benchmarks. 799// If p is less than 1, this call will have no effect. 800func (b *B) SetParallelism(p int) { 801 if p >= 1 { 802 b.parallelism = p 803 } 804} 805 806// Benchmark benchmarks a single function. It is useful for creating 807// custom benchmarks that do not use the "go test" command. 808// 809// If f depends on testing flags, then Init must be used to register 810// those flags before calling Benchmark and before calling flag.Parse. 811// 812// If f calls Run, the result will be an estimate of running all its 813// subbenchmarks that don't call Run in sequence in a single benchmark. 814func Benchmark(f func(b *B)) BenchmarkResult { 815 b := &B{ 816 common: common{ 817 signal: make(chan bool), 818 w: discard{}, 819 }, 820 benchFunc: f, 821 benchTime: benchTime, 822 } 823 if b.run1() { 824 b.run() 825 } 826 return b.result 827} 828 829type discard struct{} 830 831func (discard) Write(b []byte) (n int, err error) { return len(b), nil } 832