testing: pad benchmark names to align results

Fixes #8780

Change-Id: I09cf01ff9722eed49086992a12774f2de81d16f2
Reviewed-on: https://go-review.googlesource.com/2840
Reviewed-by: Andrew Gerrand <adg@golang.org>

diff --git a/src/testing/benchmark.go b/src/testing/benchmark.go
index ffd5376844a8e3da837560cd9a8574a891ce7ecc..62e696d2214133222257178052432ac11fb8f845 100644 (file)
--- a/src/testing/benchmark.go
+++ b/src/testing/benchmark.go
@@ -280,6 +280,14 @@ func (r BenchmarkResult) MemString() string {
                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) {
@@ -287,15 +295,30 @@ func RunBenchmarks(matchString func(pat, str string) (bool, error), 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 {
-                       continue
+               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{
@@ -304,11 +327,8 @@ func RunBenchmarks(matchString func(pat, str string) (bool, error), benchmarks [
                                },
                                benchmark: Benchmark,
                        }
-                       benchName := Benchmark.Name
-                       if procs != 1 {
-                               benchName = fmt.Sprintf("%s-%d", Benchmark.Name, procs)
-                       }
-                       fmt.Printf("%s\t", benchName)
+                       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.