// 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"
"os"
"runtime"
"sync"
"sync/atomic"
"time"
)
var matchBenchmarks = flag.String("test.bench", "", "regular expression to select benchmarks to run")
var benchTime = flag.Duration("test.benchtime", 1*time.Second, "approximate run time for each benchmark")
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.
type B struct {
common
N int
previousN int // number of iterations in the previous run
previousDuration time.Duration // total duration of the previous run
benchmark InternalBenchmark
bytes int64
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.N = n
b.parallelism = 1
b.ResetTimer()
b.StartTimer()
b.benchmark.F(b)
b.StopTimer()
b.previousN = n
b.previousDuration = b.duration
}
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
}
}
// run times the benchmark function in a separate goroutine.
func (b *B) run() 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.
// It prints timing information in this form
// testing.BenchmarkHello 100000 19 ns/op
// launch is run by the run function as a separate goroutine.
func (b *B) launch() {
// Run the benchmark for a single iteration in case it's expensive.
n := 1
// Signal that we're done whether we return normally
// or by FailNow's runtime.Goexit.
defer func() {
b.signal <- b
}()
b.runN(n)
// Run the benchmark for at least the specified amount of time.
d := *benchTime
for !b.failed && b.duration < d && n < 1e9 {
last := n
// Predict required iterations.
if b.nsPerOp() == 0 {
n = 1e9
} else {
n = int(d.Nanoseconds() / b.nsPerOp())
}
// 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
}
// 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) {
// If no flag was specified, don't run benchmarks.
if len(*matchBenchmarks) == 0 {
return
}
// Collect matching benchmarks and determine longest name.
maxprocs := 1
for _, procs := range cpuList {
if procs > maxprocs {
maxprocs = procs
}
}
maxlen := 0
var bs []InternalBenchmark
for _, Benchmark := range benchmarks {
matched, err := matchString(*matchBenchmarks, Benchmark.Name)
if err != nil {
fmt.Fprintf(os.Stderr, "testing: invalid regexp for -test.bench: %s\n", err)
os.Exit(1)
}
if matched {
bs = append(bs, Benchmark)
benchName := benchmarkName(Benchmark.Name, maxprocs)
if l := len(benchName); l > maxlen {
maxlen = l
}
}
}
for _, Benchmark := range bs {
for _, procs := range cpuList {
runtime.GOMAXPROCS(procs)
b := &B{
common: common{
signal: make(chan interface{}),
},
benchmark: Benchmark,
}
benchName := benchmarkName(Benchmark.Name, procs)
fmt.Printf("%-*s\t", maxlen, benchName)
r := b.run()
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.Printf("--- FAIL: %s\n%s", benchName, b.output)
continue
}
results := r.String()
if *benchmarkMemory || b.showAllocResult {
results += "\t" + r.MemString()
}
fmt.Println(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.Printf("--- 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)
}
}
}
}
// 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.
func (b *B) RunParallel(body func(*PB)) {
// 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.
func Benchmark(f func(b *B)) BenchmarkResult {
b := &B{
common: common{
signal: make(chan interface{}),
},
benchmark: InternalBenchmark{"", f},
}
return b.run()
}