testing: parallelize tests over count

Currently all package tests are executed once
with Parallel tests executed in parallel.
Then this process is repeated count*cpu times.
Tests are not parallelized over count*cpu.
Parallelizing over cpu is not possible as
GOMAXPROCS is a global setting. But it is
possible for count.

Parallelize over count.

Brings down testing of my package with -count=100
form 10s to 0.3s.

Change-Id: I76d8322adeb8c5c6e70b99af690291fd69d6402a
Reviewed-on: https://go-review.googlesource.com/44830
Run-TryBot: Dmitry Vyukov <dvyukov@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/testing/benchmark.go

@@ -427,11 +427,12 @@ func runBenchmarks(importPath string, matchString func(pat, str string) (bool, e
 // processBench runs bench b for the configured CPU counts and prints the results.
 func (ctx *benchContext) processBench(b *B) {
 	for i, procs := range cpuList {
+		for j := uint(0); j < *count; j++ {
 			runtime.GOMAXPROCS(procs)
 			benchName := benchmarkName(b.name, procs)
 			fmt.Fprintf(b.w, "%-*s\t", ctx.maxLen, benchName)
 			// Recompute the running time for all but the first iteration.
-		if i > 0 {
+			if i > 0 || j > 0 {
 				b = &B{
 					common: common{
 						signal: make(chan bool),
@@ -467,6 +468,7 @@ func (ctx *benchContext) processBench(b *B) {
 				fmt.Fprintf(os.Stderr, "testing: %s left GOMAXPROCS set to %d\n", benchName, p)
 			}
 		}
+	}
 }
 
 // Run benchmarks f as a subbenchmark with the given name. It reports

src/testing/testing.go

@@ -991,6 +991,7 @@ func runTests(matchString func(pat, str string) (bool, error), tests []InternalT
 	ok = true
 	for _, procs := range cpuList {
 		runtime.GOMAXPROCS(procs)
+		for i := uint(0); i < *count; i++ {
 			ctx := newTestContext(*parallel, newMatcher(matchString, *match, "-test.run"))
 			t := &T{
 				common: common{
@@ -1013,6 +1014,7 @@ func runTests(matchString func(pat, str string) (bool, error), tests []InternalT
 			ok = ok && !t.Failed()
 			ran = ran || t.ran
 		}
+	}
 	return ran, ok
 }
 
@@ -1167,13 +1169,9 @@ func parseCpuList() {
 			fmt.Fprintf(os.Stderr, "testing: invalid value %q for -test.cpu\n", val)
 			os.Exit(1)
 		}
-		for i := uint(0); i < *count; i++ {
 		cpuList = append(cpuList, cpu)
 	}
-	}
 	if cpuList == nil {
-		for i := uint(0); i < *count; i++ {
 		cpuList = append(cpuList, runtime.GOMAXPROCS(-1))
 	}
-	}
 }