// 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/race"
"os"
"runtime"
"sync"
"sync/atomic"
"time"
)
var matchBenchmarks = flag.String("test.bench", "", "run only benchmarks matching `regexp`")
var benchTime = flag.Duration("test.benchtime", 1*time.Second, "run each benchmark for duration `d`")
var benchmarkMemory = flag.Bool("test.benchmem", false, "print memory allocations for benchmarks")
// 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
// An internal type but exported because it is cross-package; 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 error 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
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 time.Duration
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
}
// StartTimer starts timing a test. This function is called automatically
// before a benchmark starts, but it can also used to resume timing after
// a call to StopTimer.
func (b *B) StartTimer() {
if !b.timerOn {
runtime.ReadMemStats(&memStats)
b.startAllocs = memStats.Mallocs
b.startBytes = memStats.TotalAlloc
b.start = time.Now()
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 += time.Now().Sub(b.start)
runtime.ReadMemStats(&memStats)
b.netAllocs += memStats.Mallocs - b.startAllocs
b.netBytes += memStats.TotalAlloc - b.startBytes
b.timerOn = false
}
}
// ResetTimer zeros the elapsed benchmark time and memory allocation counters.
// It does not affect whether the timer is running.
func (b *B) ResetTimer() {
if b.timerOn {
runtime.ReadMemStats(&memStats)
b.startAllocs = memStats.Mallocs
b.startBytes = memStats.TotalAlloc
b.start = time.Now()
}
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
}
func (b *B) nsPerOp() int64 {
if b.N <= 0 {
return 0
}
return b.duration.Nanoseconds() / int64(b.N)
}
// runN runs a single benchmark for the specified number of iterations.
func (b *B) runN(n int) {
benchmarkLock.Lock()
defer benchmarkLock.Unlock()
// Try to get a comparable environment for each run
// by clearing garbage from previous runs.
runtime.GC()
b.raceErrors = -race.Errors()
b.N = n
b.parallelism = 1
b.ResetTimer()
b.StartTimer()
b.benchFunc(b)
b.StopTimer()
b.previousN = n
b.previousDuration = b.duration
b.raceErrors += race.Errors()
if b.raceErrors > 0 {
b.Errorf("race detected during execution of benchmark")
}
}
func min(x, y int) int {
if x > y {
return y
}
return x
}
func max(x, y int) int {
if x < y {
return y
}
return x
}
// roundDown10 rounds a number down to the nearest power of 10.
func roundDown10(n int) int {
var tens = 0
// tens = floor(log_10(n))
for n >= 10 {
n = n / 10
tens++
}
// result = 10^tens
result := 1
for i := 0; i < tens; i++ {
result *= 10
}
return result
}
// roundUp rounds x up to a number of the form [1eX, 2eX, 3eX, 5eX].
func roundUp(n int) int {
base := roundDown10(n)
switch {
case n <= base:
return base
case n <= (2 * base):
return 2 * base
case n <= (3 * base):
return 3 * base
case n <= (5 * base):
return 5 * base
default:
return 10 * base
}
}
// run1 runs the first iteration of benchFunc. It returns 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, "--- FAIL: %s\n%s", 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.
if atomic.LoadInt32(&b.hasSub) != 0 || b.finished {
tag := "BENCH"
if b.skipped {
tag = "SKIP"
}
if b.chatty && (len(b.output) > 0 || b.finished) {
b.trimOutput()
fmt.Fprintf(b.w, "--- %s: %s\n%s", tag, b.name, b.output)
}
return false
}
return true
}
// run executes the benchmark in a separate goroutine, including all of its
// subbenchmarks. b must not have subbenchmarks.
func (b *B) run() BenchmarkResult {
if b.context != nil {
// Running go test --test.bench
b.context.processBench(b) // Must call doBench.
} else {
// Running func Benchmark.
b.doBench()
}
return b.result
}
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.
d := b.benchTime
for n := 1; !b.failed && b.duration < d && n < 1e9; {
last := n
// Predict required iterations.
n = int(d.Nanoseconds())
if nsop := b.nsPerOp(); nsop != 0 {
n /= int(nsop)
}
// Run more iterations than we think we'll need (1.2x).
// Don't grow too fast in case we had timing errors previously.
// Be sure to run at least one more than last time.
n = max(min(n+n/5, 100*last), last+1)
// Round up to something easy to read.
n = roundUp(n)
b.runN(n)
}
b.result = BenchmarkResult{b.N, b.duration, b.bytes, b.netAllocs, b.netBytes}
}
// 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.
}
func (r BenchmarkResult) NsPerOp() int64 {
if r.N <= 0 {
return 0
}
return r.T.Nanoseconds() / int64(r.N)
}
func (r BenchmarkResult) mbPerSec() float64 {
if r.Bytes <= 0 || r.T <= 0 || r.N <= 0 {
return 0
}
return (float64(r.Bytes) * float64(r.N) / 1e6) / r.T.Seconds()
}
func (r BenchmarkResult) AllocsPerOp() int64 {
if r.N <= 0 {
return 0
}
return int64(r.MemAllocs) / int64(r.N)
}
func (r BenchmarkResult) AllocedBytesPerOp() int64 {
if r.N <= 0 {
return 0
}
return int64(r.MemBytes) / int64(r.N)
}
func (r BenchmarkResult) String() string {
mbs := r.mbPerSec()
mb := ""
if mbs != 0 {
mb = fmt.Sprintf("\t%7.2f MB/s", mbs)
}
nsop := r.NsPerOp()
ns := fmt.Sprintf("%10d ns/op", nsop)
if r.N > 0 && nsop < 100 {
// The format specifiers here make sure that
// the ones digits line up for all three possible formats.
if nsop < 10 {
ns = fmt.Sprintf("%13.2f ns/op", float64(r.T.Nanoseconds())/float64(r.N))
} else {
ns = fmt.Sprintf("%12.1f ns/op", float64(r.T.Nanoseconds())/float64(r.N))
}
}
return fmt.Sprintf("%8d\t%s%s", r.N, ns, mb)
}
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.
}
// An internal function but exported because it is cross-package; 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(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"),
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,
chatty: *chatty,
},
benchFunc: func(b *B) {
for _, Benchmark := range bs {
b.Run(Benchmark.Name, Benchmark.F)
}
},
benchTime: *benchTime,
context: ctx,
}
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 {
runtime.GOMAXPROCS(procs)
benchName := benchmarkName(b.name, procs)
fmt.Fprintf(b.w, "%-*s\t", ctx.maxLen, benchName)
// Recompute the running time for all but the first iteration.
if i > 0 {
b = &B{
common: common{
signal: make(chan bool),
name: b.name,
w: b.w,
chatty: b.chatty,
},
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, "--- FAIL: %s\n%s", benchName, b.output)
continue
}
results := r.String()
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, "--- BENCH: %s\n%s", benchName, b.output)
}
if p := runtime.GOMAXPROCS(-1); p != procs {
fmt.Fprintf(os.Stderr, "testing: %s left GOMAXPROCS set to %d\n", benchName, p)
}
}
}
// 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.
//
// Run may be called simultaneously from multiple goroutines, but all such
// calls must happen before the outer benchmark function for b returns.
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.
atomic.StoreInt32(&b.hasSub, 1)
benchmarkLock.Unlock()
defer benchmarkLock.Lock()
benchName, ok := b.name, true
if b.context != nil {
benchName, ok = b.context.match.fullName(&b.common, name)
}
if !ok {
return true
}
sub := &B{
common: common{
signal: make(chan bool),
name: benchName,
parent: &b.common,
level: b.level + 1,
w: b.w,
chatty: b.chatty,
},
benchFunc: f,
benchTime: b.benchTime,
context: b.context,
}
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 *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 := atomic.AddUint64(pb.globalN, 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 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 StartTimer, StopTimer, or ResetTimer functions,
// because they have global effect. It should also not call Run.
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
}
n := uint64(0)
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 <= uint64(b.N) && !b.Failed() {
b.Fatal("RunParallel: body exited without pb.Next() == false")
}
}
// SetParallelism sets the number of goroutines used by 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. Useful for creating
// custom benchmarks that do not use the "go test" command.
//
// 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() {
return BenchmarkResult{}
}
return b.run()
}
type discard struct{}
func (discard) Write(b []byte) (n int, err error) { return len(b), nil }