testing: compute MB/s in benchmarks

R=r
https://golang.org/cl/166060

diff --git a/src/pkg/testing/benchmark.go b/src/pkg/testing/benchmark.go
index b6e100686d7006e52bf8a264af229aae3d7f99d8..b552a132015820bd6baa416225ff0e1a1a1f12cc 100644 (file)
--- a/src/pkg/testing/benchmark.go
+++ b/src/pkg/testing/benchmark.go
@@ -26,6 +26,7 @@ type B struct {
        N               int;
        benchmark       Benchmark;
        ns              int64;
+       bytes           int64;
        start           int64;
 }
 
@@ -50,6 +51,10 @@ func (b *B) ResetTimer() {
        b.ns = 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 }
+
 func (b *B) nsPerOp() int64 {
        if b.N <= 0 {
                return 0
@@ -125,7 +130,12 @@ func (b *B) run() {
                n = roundUp(n);
                b.runN(n);
        }
-       fmt.Printf("%s\t%d\t%10d ns/op\n", b.benchmark.Name, b.N, b.nsPerOp());
+       ns := b.nsPerOp();
+       mb := "";
+       if ns > 0 && b.bytes > 0 {
+               mb = fmt.Sprintf("\t%7.2f MB/s", (float64(b.bytes)/1e6)/(float64(ns)/1e9))
+       }
+       fmt.Printf("%s\t%8d\t%10d ns/op%s\n", b.benchmark.Name, b.N, b.nsPerOp(), mb);
 }
 
 // An internal function but exported because it is cross-package; part of the implementation