// Copyright 2009 The Go Authors. All rights reserved. // Use of this source code is governed by a BSD-style // license that can be found in the LICENSE file. package testing import ( "flag" "fmt" "internal/sysinfo" "io" "math" "os" "runtime" "slices" "strconv" "strings" "sync" "sync/atomic" "time" "unicode" ) func initBenchmarkFlags() { matchBenchmarks = flag.String("test.bench", "", "run only benchmarks matching `regexp`") benchmarkMemory = flag.Bool("test.benchmem", false, "print memory allocations for benchmarks") flag.Var(&benchTime, "test.benchtime", "run each benchmark for duration `d` or N times if `d` is of the form Nx") } var ( matchBenchmarks *string benchmarkMemory *bool benchTime = durationOrCountFlag{d: 1 * time.Second} // changed during test of testing package ) type durationOrCountFlag struct { d time.Duration n int allowZero bool } func (f *durationOrCountFlag) String() string { if f.n > 0 { return fmt.Sprintf("%dx", f.n) } return f.d.String() } func (f *durationOrCountFlag) Set(s string) error { if strings.HasSuffix(s, "x") { n, err := strconv.ParseInt(s[:len(s)-1], 10, 0) if err != nil || n < 0 || (!f.allowZero && n == 0) { return fmt.Errorf("invalid count") } *f = durationOrCountFlag{n: int(n)} return nil } d, err := time.ParseDuration(s) if err != nil || d < 0 || (!f.allowZero && d == 0) { return fmt.Errorf("invalid duration") } *f = durationOrCountFlag{d: d} return nil } // Global lock to ensure only one benchmark runs at a time. var benchmarkLock sync.Mutex // Used for every benchmark for measuring memory. var memStats runtime.MemStats // InternalBenchmark is an internal type but exported because it is cross-package; // it is part of the implementation of the "go test" command. type InternalBenchmark struct { Name string F func(b *B) } // B is a type passed to [Benchmark] functions to manage benchmark // timing and to specify the number of iterations to run. // // A benchmark ends when its Benchmark function returns or calls any of the methods // FailNow, Fatal, Fatalf, SkipNow, Skip, or Skipf. Those methods must be called // only from the goroutine running the Benchmark function. // The other reporting methods, such as the variations of Log and Error, // may be called simultaneously from multiple goroutines. // // Like in tests, benchmark logs are accumulated during execution // and dumped to standard output when done. Unlike in tests, benchmark logs // are always printed, so as not to hide output whose existence may be // affecting benchmark results. type B struct { common importPath string // import path of the package containing the benchmark context *benchContext N int previousN int // number of iterations in the previous run previousDuration time.Duration // total duration of the previous run benchFunc func(b *B) benchTime durationOrCountFlag bytes int64 missingBytes bool // one of the subbenchmarks does not have bytes set. timerOn bool showAllocResult bool result BenchmarkResult parallelism int // RunParallel creates parallelism*GOMAXPROCS goroutines // The initial states of memStats.Mallocs and memStats.TotalAlloc. startAllocs uint64 startBytes uint64 // The net total of this test after being run. netAllocs uint64 netBytes uint64 // Extra metrics collected by ReportMetric. extra map[string]float64 } // StartTimer starts timing a test. This function is called automatically // before a benchmark starts, but it can also be used to resume timing after // a call to [B.StopTimer]. func (b *B) StartTimer() { if !b.timerOn { runtime.ReadMemStats(&memStats) b.startAllocs = memStats.Mallocs b.startBytes = memStats.TotalAlloc b.start = highPrecisionTimeNow() b.timerOn = true } } // StopTimer stops timing a test. This can be used to pause the timer // while performing complex initialization that you don't // want to measure. func (b *B) StopTimer() { if b.timerOn { b.duration += highPrecisionTimeSince(b.start) runtime.ReadMemStats(&memStats) b.netAllocs += memStats.Mallocs - b.startAllocs b.netBytes += memStats.TotalAlloc - b.startBytes b.timerOn = false } } // ResetTimer zeroes the elapsed benchmark time and memory allocation counters // and deletes user-reported metrics. // It does not affect whether the timer is running. func (b *B) ResetTimer() { if b.extra == nil { // Allocate the extra map before reading memory stats. // Pre-size it to make more allocation unlikely. b.extra = make(map[string]float64, 16) } else { clear(b.extra) } if b.timerOn { runtime.ReadMemStats(&memStats) b.startAllocs = memStats.Mallocs b.startBytes = memStats.TotalAlloc b.start = highPrecisionTimeNow() } b.duration = 0 b.netAllocs = 0 b.netBytes = 0 } // SetBytes records the number of bytes processed in a single operation. // If this is called, the benchmark will report ns/op and MB/s. func (b *B) SetBytes(n int64) { b.bytes = n } // ReportAllocs enables malloc statistics for this benchmark. // It is equivalent to setting -test.benchmem, but it only affects the // benchmark function that calls ReportAllocs. func (b *B) ReportAllocs() { b.showAllocResult = true } // runN runs a single benchmark for the specified number of iterations. func (b *B) runN(n int) { benchmarkLock.Lock() defer benchmarkLock.Unlock() defer func() { b.runCleanup(normalPanic) b.checkRaces() }() // Try to get a comparable environment for each run // by clearing garbage from previous runs. runtime.GC() b.resetRaces() b.N = n b.parallelism = 1 b.ResetTimer() b.StartTimer() b.benchFunc(b) b.StopTimer() b.previousN = n b.previousDuration = b.duration } // run1 runs the first iteration of benchFunc. It reports whether more // iterations of this benchmarks should be run. func (b *B) run1() bool { if ctx := b.context; ctx != nil { // Extend maxLen, if needed. if n := len(b.name) + ctx.extLen + 1; n > ctx.maxLen { ctx.maxLen = n + 8 // Add additional slack to avoid too many jumps in size. } } go func() { // Signal that we're done whether we return normally // or by FailNow's runtime.Goexit. defer func() { b.signal <- true }() b.runN(1) }() <-b.signal if b.failed { fmt.Fprintf(b.w, "%s--- FAIL: %s\n%s", b.chatty.prefix(), b.name, b.output) return false } // Only print the output if we know we are not going to proceed. // Otherwise it is printed in processBench. b.mu.RLock() finished := b.finished b.mu.RUnlock() if b.hasSub.Load() || finished { tag := "BENCH" if b.skipped { tag = "SKIP" } if b.chatty != nil && (len(b.output) > 0 || finished) { b.trimOutput() fmt.Fprintf(b.w, "%s--- %s: %s\n%s", b.chatty.prefix(), tag, b.name, b.output) } return false } return true } var labelsOnce sync.Once // run executes the benchmark in a separate goroutine, including all of its // subbenchmarks. b must not have subbenchmarks. func (b *B) run() { labelsOnce.Do(func() { fmt.Fprintf(b.w, "goos: %s\n", runtime.GOOS) fmt.Fprintf(b.w, "goarch: %s\n", runtime.GOARCH) if b.importPath != "" { fmt.Fprintf(b.w, "pkg: %s\n", b.importPath) } if cpu := sysinfo.CPUName(); cpu != "" { fmt.Fprintf(b.w, "cpu: %s\n", cpu) } }) if b.context != nil { // Running go test --test.bench b.context.processBench(b) // Must call doBench. } else { // Running func Benchmark. b.doBench() } } func (b *B) doBench() BenchmarkResult { go b.launch() <-b.signal return b.result } // launch launches the benchmark function. It gradually increases the number // of benchmark iterations until the benchmark runs for the requested benchtime. // launch is run by the doBench function as a separate goroutine. // run1 must have been called on b. func (b *B) launch() { // Signal that we're done whether we return normally // or by FailNow's runtime.Goexit. defer func() { b.signal <- true }() // Run the benchmark for at least the specified amount of time. if b.benchTime.n > 0 { // We already ran a single iteration in run1. // If -benchtime=1x was requested, use that result. // See https://golang.org/issue/32051. if b.benchTime.n > 1 { b.runN(b.benchTime.n) } } else { d := b.benchTime.d for n := int64(1); !b.failed && b.duration < d && n < 1e9; { last := n // Predict required iterations. goalns := d.Nanoseconds() prevIters := int64(b.N) prevns := b.duration.Nanoseconds() if prevns <= 0 { // Round up, to avoid div by zero. prevns = 1 } // Order of operations matters. // For very fast benchmarks, prevIters ~= prevns. // If you divide first, you get 0 or 1, // which can hide an order of magnitude in execution time. // So multiply first, then divide. n = goalns * prevIters / prevns // Run more iterations than we think we'll need (1.2x). n += n / 5 // Don't grow too fast in case we had timing errors previously. n = min(n, 100*last) // Be sure to run at least one more than last time. n = max(n, last+1) // Don't run more than 1e9 times. (This also keeps n in int range on 32 bit platforms.) n = min(n, 1e9) b.runN(int(n)) } } b.result = BenchmarkResult{b.N, b.duration, b.bytes, b.netAllocs, b.netBytes, b.extra} } // Elapsed returns the measured elapsed time of the benchmark. // The duration reported by Elapsed matches the one measured by // [B.StartTimer], [B.StopTimer], and [B.ResetTimer]. func (b *B) Elapsed() time.Duration { d := b.duration if b.timerOn { d += highPrecisionTimeSince(b.start) } return d } // ReportMetric adds "n unit" to the reported benchmark results. // If the metric is per-iteration, the caller should divide by b.N, // and by convention units should end in "/op". // ReportMetric overrides any previously reported value for the same unit. // ReportMetric panics if unit is the empty string or if unit contains // any whitespace. // If unit is a unit normally reported by the benchmark framework itself // (such as "allocs/op"), ReportMetric will override that metric. // Setting "ns/op" to 0 will suppress that built-in metric. func (b *B) ReportMetric(n float64, unit string) { if unit == "" { panic("metric unit must not be empty") } if strings.IndexFunc(unit, unicode.IsSpace) >= 0 { panic("metric unit must not contain whitespace") } b.extra[unit] = n } // BenchmarkResult contains the results of a benchmark run. type BenchmarkResult struct { N int // The number of iterations. T time.Duration // The total time taken. Bytes int64 // Bytes processed in one iteration. MemAllocs uint64 // The total number of memory allocations. MemBytes uint64 // The total number of bytes allocated. // Extra records additional metrics reported by ReportMetric. Extra map[string]float64 } // NsPerOp returns the "ns/op" metric. func (r BenchmarkResult) NsPerOp() int64 { if v, ok := r.Extra["ns/op"]; ok { return int64(v) } if r.N <= 0 { return 0 } return r.T.Nanoseconds() / int64(r.N) } // mbPerSec returns the "MB/s" metric. func (r BenchmarkResult) mbPerSec() float64 { if v, ok := r.Extra["MB/s"]; ok { return v } if r.Bytes <= 0 || r.T <= 0 || r.N <= 0 { return 0 } return (float64(r.Bytes) * float64(r.N) / 1e6) / r.T.Seconds() } // AllocsPerOp returns the "allocs/op" metric, // which is calculated as r.MemAllocs / r.N. func (r BenchmarkResult) AllocsPerOp() int64 { if v, ok := r.Extra["allocs/op"]; ok { return int64(v) } if r.N <= 0 { return 0 } return int64(r.MemAllocs) / int64(r.N) } // AllocedBytesPerOp returns the "B/op" metric, // which is calculated as r.MemBytes / r.N. func (r BenchmarkResult) AllocedBytesPerOp() int64 { if v, ok := r.Extra["B/op"]; ok { return int64(v) } if r.N <= 0 { return 0 } return int64(r.MemBytes) / int64(r.N) } // String returns a summary of the benchmark results. // It follows the benchmark result line format from // https://golang.org/design/14313-benchmark-format, not including the // benchmark name. // Extra metrics override built-in metrics of the same name. // String does not include allocs/op or B/op, since those are reported // by [BenchmarkResult.MemString]. func (r BenchmarkResult) String() string { buf := new(strings.Builder) fmt.Fprintf(buf, "%8d", r.N) // Get ns/op as a float. ns, ok := r.Extra["ns/op"] if !ok { ns = float64(r.T.Nanoseconds()) / float64(r.N) } if ns != 0 { buf.WriteByte('\t') prettyPrint(buf, ns, "ns/op") } if mbs := r.mbPerSec(); mbs != 0 { fmt.Fprintf(buf, "\t%7.2f MB/s", mbs) } // Print extra metrics that aren't represented in the standard // metrics. var extraKeys []string for k := range r.Extra { switch k { case "ns/op", "MB/s", "B/op", "allocs/op": // Built-in metrics reported elsewhere. continue } extraKeys = append(extraKeys, k) } slices.Sort(extraKeys) for _, k := range extraKeys { buf.WriteByte('\t') prettyPrint(buf, r.Extra[k], k) } return buf.String() } func prettyPrint(w io.Writer, x float64, unit string) { // Print all numbers with 10 places before the decimal point // and small numbers with four sig figs. Field widths are // chosen to fit the whole part in 10 places while aligning // the decimal point of all fractional formats. var format string switch y := math.Abs(x); { case y == 0 || y >= 999.95: format = "%10.0f %s" case y >= 99.995: format = "%12.1f %s" case y >= 9.9995: format = "%13.2f %s" case y >= 0.99995: format = "%14.3f %s" case y >= 0.099995: format = "%15.4f %s" case y >= 0.0099995: format = "%16.5f %s" case y >= 0.00099995: format = "%17.6f %s" default: format = "%18.7f %s" } fmt.Fprintf(w, format, x, unit) } // MemString returns r.AllocedBytesPerOp and r.AllocsPerOp in the same format as 'go test'. func (r BenchmarkResult) MemString() string { return fmt.Sprintf("%8d B/op\t%8d allocs/op", r.AllocedBytesPerOp(), r.AllocsPerOp()) } // benchmarkName returns full name of benchmark including procs suffix. func benchmarkName(name string, n int) string { if n != 1 { return fmt.Sprintf("%s-%d", name, n) } return name } type benchContext struct { match *matcher maxLen int // The largest recorded benchmark name. extLen int // Maximum extension length. } // RunBenchmarks is an internal function but exported because it is cross-package; // it is part of the implementation of the "go test" command. func RunBenchmarks(matchString func(pat, str string) (bool, error), benchmarks []InternalBenchmark) { runBenchmarks("", matchString, benchmarks) } func runBenchmarks(importPath string, matchString func(pat, str string) (bool, error), benchmarks []InternalBenchmark) bool { // If no flag was specified, don't run benchmarks. if len(*matchBenchmarks) == 0 { return true } // Collect matching benchmarks and determine longest name. maxprocs := 1 for _, procs := range cpuList { if procs > maxprocs { maxprocs = procs } } ctx := &benchContext{ match: newMatcher(matchString, *matchBenchmarks, "-test.bench", *skip), extLen: len(benchmarkName("", maxprocs)), } var bs []InternalBenchmark for _, Benchmark := range benchmarks { if _, matched, _ := ctx.match.fullName(nil, Benchmark.Name); matched { bs = append(bs, Benchmark) benchName := benchmarkName(Benchmark.Name, maxprocs) if l := len(benchName) + ctx.extLen + 1; l > ctx.maxLen { ctx.maxLen = l } } } main := &B{ common: common{ name: "Main", w: os.Stdout, bench: true, }, importPath: importPath, benchFunc: func(b *B) { for _, Benchmark := range bs { b.Run(Benchmark.Name, Benchmark.F) } }, benchTime: benchTime, context: ctx, } if Verbose() { main.chatty = newChattyPrinter(main.w) } main.runN(1) return !main.failed } // processBench runs bench b for the configured CPU counts and prints the results. func (ctx *benchContext) processBench(b *B) { for i, procs := range cpuList { for j := uint(0); j < *count; j++ { runtime.GOMAXPROCS(procs) benchName := benchmarkName(b.name, procs) // If it's chatty, we've already printed this information. if b.chatty == nil { fmt.Fprintf(b.w, "%-*s\t", ctx.maxLen, benchName) } // Recompute the running time for all but the first iteration. if i > 0 || j > 0 { b = &B{ common: common{ signal: make(chan bool), name: b.name, w: b.w, chatty: b.chatty, bench: true, }, benchFunc: b.benchFunc, benchTime: b.benchTime, } b.run1() } r := b.doBench() if b.failed { // The output could be very long here, but probably isn't. // We print it all, regardless, because we don't want to trim the reason // the benchmark failed. fmt.Fprintf(b.w, "%s--- FAIL: %s\n%s", b.chatty.prefix(), benchName, b.output) continue } results := r.String() if b.chatty != nil { fmt.Fprintf(b.w, "%-*s\t", ctx.maxLen, benchName) } if *benchmarkMemory || b.showAllocResult { results += "\t" + r.MemString() } fmt.Fprintln(b.w, results) // Unlike with tests, we ignore the -chatty flag and always print output for // benchmarks since the output generation time will skew the results. if len(b.output) > 0 { b.trimOutput() fmt.Fprintf(b.w, "%s--- BENCH: %s\n%s", b.chatty.prefix(), benchName, b.output) } if p := runtime.GOMAXPROCS(-1); p != procs { fmt.Fprintf(os.Stderr, "testing: %s left GOMAXPROCS set to %d\n", benchName, p) } if b.chatty != nil && b.chatty.json { b.chatty.Updatef("", "=== NAME %s\n", "") } } } } // If hideStdoutForTesting is true, Run does not print the benchName. // This avoids a spurious print during 'go test' on package testing itself, // which invokes b.Run in its own tests (see sub_test.go). var hideStdoutForTesting = false // Run benchmarks f as a subbenchmark with the given name. It reports // whether there were any failures. // // A subbenchmark is like any other benchmark. A benchmark that calls Run at // least once will not be measured itself and will be called once with N=1. func (b *B) Run(name string, f func(b *B)) bool { // Since b has subbenchmarks, we will no longer run it as a benchmark itself. // Release the lock and acquire it on exit to ensure locks stay paired. b.hasSub.Store(true) benchmarkLock.Unlock() defer benchmarkLock.Lock() benchName, ok, partial := b.name, true, false if b.context != nil { benchName, ok, partial = b.context.match.fullName(&b.common, name) } if !ok { return true } var pc [maxStackLen]uintptr n := runtime.Callers(2, pc[:]) sub := &B{ common: common{ signal: make(chan bool), name: benchName, parent: &b.common, level: b.level + 1, creator: pc[:n], w: b.w, chatty: b.chatty, bench: true, }, importPath: b.importPath, benchFunc: f, benchTime: b.benchTime, context: b.context, } if partial { // Partial name match, like -bench=X/Y matching BenchmarkX. // Only process sub-benchmarks, if any. sub.hasSub.Store(true) } if b.chatty != nil { labelsOnce.Do(func() { fmt.Printf("goos: %s\n", runtime.GOOS) fmt.Printf("goarch: %s\n", runtime.GOARCH) if b.importPath != "" { fmt.Printf("pkg: %s\n", b.importPath) } if cpu := sysinfo.CPUName(); cpu != "" { fmt.Printf("cpu: %s\n", cpu) } }) if !hideStdoutForTesting { if b.chatty.json { b.chatty.Updatef(benchName, "=== RUN %s\n", benchName) } fmt.Println(benchName) } } if sub.run1() { sub.run() } b.add(sub.result) return !sub.failed } // add simulates running benchmarks in sequence in a single iteration. It is // used to give some meaningful results in case func Benchmark is used in // combination with Run. func (b *B) add(other BenchmarkResult) { r := &b.result // The aggregated BenchmarkResults resemble running all subbenchmarks as // in sequence in a single benchmark. r.N = 1 r.T += time.Duration(other.NsPerOp()) if other.Bytes == 0 { // Summing Bytes is meaningless in aggregate if not all subbenchmarks // set it. b.missingBytes = true r.Bytes = 0 } if !b.missingBytes { r.Bytes += other.Bytes } r.MemAllocs += uint64(other.AllocsPerOp()) r.MemBytes += uint64(other.AllocedBytesPerOp()) } // trimOutput shortens the output from a benchmark, which can be very long. func (b *B) trimOutput() { // The output is likely to appear multiple times because the benchmark // is run multiple times, but at least it will be seen. This is not a big deal // because benchmarks rarely print, but just in case, we trim it if it's too long. const maxNewlines = 10 for nlCount, j := 0, 0; j < len(b.output); j++ { if b.output[j] == '\n' { nlCount++ if nlCount >= maxNewlines { b.output = append(b.output[:j], "\n\t... [output truncated]\n"...) break } } } } // A PB is used by RunParallel for running parallel benchmarks. type PB struct { globalN *atomic.Uint64 // shared between all worker goroutines iteration counter grain uint64 // acquire that many iterations from globalN at once cache uint64 // local cache of acquired iterations bN uint64 // total number of iterations to execute (b.N) } // Next reports whether there are more iterations to execute. func (pb *PB) Next() bool { if pb.cache == 0 { n := pb.globalN.Add(pb.grain) if n <= pb.bN { pb.cache = pb.grain } else if n < pb.bN+pb.grain { pb.cache = pb.bN + pb.grain - n } else { return false } } pb.cache-- return true } // RunParallel runs a benchmark in parallel. // It creates multiple goroutines and distributes b.N iterations among them. // The number of goroutines defaults to GOMAXPROCS. To increase parallelism for // non-CPU-bound benchmarks, call [B.SetParallelism] before RunParallel. // RunParallel is usually used with the go test -cpu flag. // // The body function will be run in each goroutine. It should set up any // goroutine-local state and then iterate until pb.Next returns false. // It should not use the [B.StartTimer], [B.StopTimer], or [B.ResetTimer] functions, // because they have global effect. It should also not call [B.Run]. // // RunParallel reports ns/op values as wall time for the benchmark as a whole, // not the sum of wall time or CPU time over each parallel goroutine. func (b *B) RunParallel(body func(*PB)) { if b.N == 0 { return // Nothing to do when probing. } // Calculate grain size as number of iterations that take ~100µs. // 100µs is enough to amortize the overhead and provide sufficient // dynamic load balancing. grain := uint64(0) if b.previousN > 0 && b.previousDuration > 0 { grain = 1e5 * uint64(b.previousN) / uint64(b.previousDuration) } if grain < 1 { grain = 1 } // We expect the inner loop and function call to take at least 10ns, // so do not do more than 100µs/10ns=1e4 iterations. if grain > 1e4 { grain = 1e4 } var n atomic.Uint64 numProcs := b.parallelism * runtime.GOMAXPROCS(0) var wg sync.WaitGroup wg.Add(numProcs) for p := 0; p < numProcs; p++ { go func() { defer wg.Done() pb := &PB{ globalN: &n, grain: grain, bN: uint64(b.N), } body(pb) }() } wg.Wait() if n.Load() <= uint64(b.N) && !b.Failed() { b.Fatal("RunParallel: body exited without pb.Next() == false") } } // SetParallelism sets the number of goroutines used by [B.RunParallel] to p*GOMAXPROCS. // There is usually no need to call SetParallelism for CPU-bound benchmarks. // If p is less than 1, this call will have no effect. func (b *B) SetParallelism(p int) { if p >= 1 { b.parallelism = p } } // Benchmark benchmarks a single function. It is useful for creating // custom benchmarks that do not use the "go test" command. // // If f depends on testing flags, then [Init] must be used to register // those flags before calling Benchmark and before calling [flag.Parse]. // // If f calls Run, the result will be an estimate of running all its // subbenchmarks that don't call Run in sequence in a single benchmark. func Benchmark(f func(b *B)) BenchmarkResult { b := &B{ common: common{ signal: make(chan bool), w: discard{}, }, benchFunc: f, benchTime: benchTime, } if b.run1() { b.run() } return b.result } type discard struct{} func (discard) Write(b []byte) (n int, err error) { return len(b), nil }