testing: change -test.benchtime to a flag.Duration.

Fixes #3902.

R=golang-dev, minux.ma, rsc, r
CC=golang-dev
https://golang.org/cl/6611059

misc/zsh/go

@@ -88,7 +88,7 @@ __go_tool_complete() {
         "-cpu[values of GOMAXPROCS to use]:number list" \
         "-run[run tests and examples matching regexp]:regexp" \
         "-bench[run benchmarks matching regexp]:regexp" \
-        "-benchtime[run each benchmark during n seconds]:duration" \
+        "-benchtime[run each benchmark until taking this long]:duration" \
         "-timeout[kill test after that duration]:duration" \
         "-cpuprofile[write CPU profile to file]:file:_files" \
         "-memprofile[write heap profile to file]:file:_files" \

src/cmd/go/doc.go

@@ -708,8 +708,8 @@ directory containing the package sources, has its own flags:
 	-test.timeout t
 		If a test runs longer than t, panic.
 
-	-test.benchtime n
+	-test.benchtime t
-		Run enough iterations of each benchmark to take n seconds.
+		Run enough iterations of each benchmark to take t.
 		The default is 1 second.
 
 	-test.cpu 1,2,4

src/cmd/go/test.go

@@ -138,8 +138,8 @@ directory containing the package sources, has its own flags:
 	-test.timeout t
 		If a test runs longer than t, panic.
 
-	-test.benchtime n
+	-test.benchtime t
-		Run enough iterations of each benchmark to take n seconds.
+		Run enough iterations of each benchmark to take t.
 		The default is 1 second.
 
 	-test.cpu 1,2,4

src/cmd/go/testflag.go

@@ -26,7 +26,7 @@ var usageMessage = `Usage of go test:
   // These flags can be passed with or without a "test." prefix: -v or -test.v.
   -bench="": passes -test.bench to test
   -benchmem=false: print memory allocation statistics for benchmarks
-  -benchtime=1: passes -test.benchtime to test
+  -benchtime=1s: passes -test.benchtime to test
   -cpu="": passes -test.cpu to test
   -cpuprofile="": passes -test.cpuprofile to test
   -memprofile="": passes -test.memprofile to test

src/pkg/go/doc/testdata/benchmark.go

@@ -13,7 +13,7 @@ import (
 )
 
 var matchBenchmarks = flag.String("test.bench", "", "regular expression to select benchmarks to run")
-var benchTime = flag.Float64("test.benchtime", 1, "approximate run time for each benchmark, in seconds")
+var benchTime = flag.Duration("test.benchtime", 1*time.Second, "approximate run time for each benchmark")
 
 // An internal type but exported because it is cross-package; part of the implementation
 // of go test.
@@ -151,7 +151,7 @@ func (b *B) launch() {
 
 	b.runN(n)
 	// Run the benchmark for at least the specified amount of time.
-	d := time.Duration(*benchTime * float64(time.Second))
+	d := *benchTime
 	for !b.failed && b.duration < d && n < 1e9 {
 		last := n
 		// Predict iterations/sec.

src/pkg/go/doc/testdata/testing.1.golden

@@ -45,7 +45,7 @@ VARIABLES
 	)
 
 	// 
-	var benchTime = flag.Float64("test.benchtime", 1, "approximate run time for each benchmark, in seconds")
+	var benchTime = flag.Duration("test.benchtime", 1*time.Second, "approximate run time for each benchmark")
 
 	// 
 	var matchBenchmarks = flag.String("test.bench", "", "regular expression to select benchmarks to run")

src/pkg/net/http/serve_test.go

@@ -1378,7 +1378,7 @@ func benchmarkClientServerParallel(b *testing.B, conc int) {
 //
 // For use like:
 //   $ go test -c
-//   $ ./http.test -test.run=XX -test.bench=BenchmarkServer -test.benchtime=15 -test.cpuprofile=http.prof
+//   $ ./http.test -test.run=XX -test.bench=BenchmarkServer -test.benchtime=15s -test.cpuprofile=http.prof
 //   $ go tool pprof http.test http.prof
 //   (pprof) web
 func BenchmarkServer(b *testing.B) {

src/pkg/testing/benchmark.go

@@ -14,7 +14,7 @@ import (
 )
 
 var matchBenchmarks = flag.String("test.bench", "", "regular expression to select benchmarks to run")
-var benchTime = flag.Float64("test.benchtime", 1, "approximate run time for each benchmark, in seconds")
+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.
@@ -178,7 +178,7 @@ func (b *B) launch() {
 
 	b.runN(n)
 	// Run the benchmark for at least the specified amount of time.
-	d := time.Duration(*benchTime * float64(time.Second))
+	d := *benchTime
 	for !b.failed && b.duration < d && n < 1e9 {
 		last := n
 		// Predict iterations/sec.

test/fixedbugs/bug369.go

@@ -38,9 +38,9 @@ func BenchmarkSlowNonASCII(b *testing.B) {
 }
 
 func main() {
-	os.Args = []string{os.Args[0], "-test.benchtime=0.1"}
+	os.Args = []string{os.Args[0], "-test.benchtime=100ms"}
 	flag.Parse()
-	
+
 	rslow := testing.Benchmark(BenchmarkSlowNonASCII)
 	rfast := testing.Benchmark(BenchmarkFastNonASCII)
 	tslow := rslow.NsPerOp()