Fix benchtime too long leads timeout :

1. handles overflows
2. add an unit test

Author: lkxiaolou

src/testing/benchmark.go

@@ -323,10 +323,17 @@ func (b *B) launch() {
 			// 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)
+			// Can't restore goalns means overflows.
+			if n*prevns/prevIters != goalns {
+				// Overflows means need to be executed many many times,
+				// otherwise it is easy to be timeout.
+				n = 100 * last
+			} else {
+				// 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.)

src/testing/benchmark_test.go

@@ -2,15 +2,14 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-package testing_test
+package testing
 
 import (
 	"bytes"
 	"runtime"
 	"sort"
 	"strings"
 	"sync/atomic"
-	"testing"
 	"text/template"
 	"time"
 )
@@ -32,19 +31,19 @@ var prettyPrintTests = []struct {
 	{0.0000999949999, "         0.0001000 x"},
 }
 
-func TestPrettyPrint(t *testing.T) {
+func TestPrettyPrint(t *T) {
 	for _, tt := range prettyPrintTests {
 		buf := new(strings.Builder)
-		testing.PrettyPrint(buf, tt.v, "x")
+		PrettyPrint(buf, tt.v, "x")
 		if tt.expected != buf.String() {
 			t.Errorf("prettyPrint(%v): expected %q, actual %q", tt.v, tt.expected, buf.String())
 		}
 	}
 }
 
-func TestResultString(t *testing.T) {
+func TestResultString(t *T) {
 	// Test fractional ns/op handling
-	r := testing.BenchmarkResult{
+	r := BenchmarkResult{
 		N: 100,
 		T: 240 * time.Nanosecond,
 	}
@@ -68,15 +67,15 @@ func TestResultString(t *testing.T) {
 	}
 }
 
-func TestRunParallel(t *testing.T) {
-	if testing.Short() {
+func TestRunParallel(t *T) {
+	if Short() {
 		t.Skip("skipping in short mode")
 	}
-	testing.Benchmark(func(b *testing.B) {
+	Benchmark(func(b *B) {
 		procs := uint32(0)
 		iters := uint64(0)
 		b.SetParallelism(3)
-		b.RunParallel(func(pb *testing.PB) {
+		b.RunParallel(func(pb *PB) {
 			atomic.AddUint32(&procs, 1)
 			for pb.Next() {
 				atomic.AddUint64(&iters, 1)
@@ -91,9 +90,9 @@ func TestRunParallel(t *testing.T) {
 	})
 }
 
-func TestRunParallelFail(t *testing.T) {
-	testing.Benchmark(func(b *testing.B) {
-		b.RunParallel(func(pb *testing.PB) {
+func TestRunParallelFail(t *T) {
+	Benchmark(func(b *B) {
+		b.RunParallel(func(pb *PB) {
 			// The function must be able to log/abort
 			// w/o crashing/deadlocking the whole benchmark.
 			b.Log("log")
@@ -102,9 +101,9 @@ func TestRunParallelFail(t *testing.T) {
 	})
 }
 
-func TestRunParallelFatal(t *testing.T) {
-	testing.Benchmark(func(b *testing.B) {
-		b.RunParallel(func(pb *testing.PB) {
+func TestRunParallelFatal(t *T) {
+	Benchmark(func(b *B) {
+		b.RunParallel(func(pb *PB) {
 			for pb.Next() {
 				if b.N > 1 {
 					b.Fatal("error")
@@ -114,9 +113,9 @@ func TestRunParallelFatal(t *testing.T) {
 	})
 }
 
-func TestRunParallelSkipNow(t *testing.T) {
-	testing.Benchmark(func(b *testing.B) {
-		b.RunParallel(func(pb *testing.PB) {
+func TestRunParallelSkipNow(t *T) {
+	Benchmark(func(b *B) {
+		b.RunParallel(func(pb *PB) {
 			for pb.Next() {
 				if b.N > 1 {
 					b.SkipNow()
@@ -128,11 +127,11 @@ func TestRunParallelSkipNow(t *testing.T) {
 
 func ExampleB_RunParallel() {
 	// Parallel benchmark for text/template.Template.Execute on a single object.
-	testing.Benchmark(func(b *testing.B) {
+	Benchmark(func(b *B) {
 		templ := template.Must(template.New("test").Parse("Hello, {{.}}!"))
 		// RunParallel will create GOMAXPROCS goroutines
 		// and distribute work among them.
-		b.RunParallel(func(pb *testing.PB) {
+		b.RunParallel(func(pb *PB) {
 			// Each goroutine has its own bytes.Buffer.
 			var buf bytes.Buffer
 			for pb.Next() {
@@ -144,8 +143,8 @@ func ExampleB_RunParallel() {
 	})
 }
 
-func TestReportMetric(t *testing.T) {
-	res := testing.Benchmark(func(b *testing.B) {
+func TestReportMetric(t *T) {
+	res := Benchmark(func(b *B) {
 		b.ReportMetric(12345, "ns/op")
 		b.ReportMetric(0.2, "frobs/op")
 	})
@@ -164,7 +163,7 @@ func TestReportMetric(t *testing.T) {
 func ExampleB_ReportMetric() {
 	// This reports a custom benchmark metric relevant to a
 	// specific algorithm (in this case, sorting).
-	testing.Benchmark(func(b *testing.B) {
+	Benchmark(func(b *B) {
 		var compares int64
 		for i := 0; i < b.N; i++ {
 			s := []int{5, 4, 3, 2, 1}
@@ -178,3 +177,23 @@ func ExampleB_ReportMetric() {
 		b.ReportMetric(float64(compares)/float64(b.N), "compares/op")
 	})
 }
+
+func TestBenchmarkLaunch(t *T) {
+	tmp := benchTime
+	t.cleanups = append(t.cleanups, func() {
+		t.Logf("reset benchTime")
+		benchTime = tmp
+	})
+	// Set a long benchtime.
+	benchTime = durationOrCountFlag{
+		d: 150 * time.Second,
+	}
+	var try int32 = 0
+	Benchmark(func(b *B) {
+		c := atomic.AddInt32(&try, 1)
+		t.Logf("try %d %d\n", c, b.N)
+		if c > 6 {
+			t.Fatalf("benchmark try to many times %d", c)
+		}
+	})
+}