Closed
Description
What version of Go are you using (go version
)?
$ go version go version devel +8266570ba7 Fri Sep 25 19:10:05 2020 +0000 darwin/amd64
Does this issue reproduce with the latest release?
Yes. 1.15.2
What operating system and processor architecture are you using (go env
)?
go env
Output
$ go env GO111MODULE="" GOARCH="amd64" GOBIN="" GOCACHE="/Users/changkun/Library/Caches/go-build" GOENV="/Users/changkun/Library/Application Support/go/env" GOEXE="" GOFLAGS="" GOHOSTARCH="amd64" GOHOSTOS="darwin" GOINSECURE="" GOMODCACHE="/Users/changkun/go/pkg/mod" GONOPROXY="" GONOSUMDB="" GOOS="darwin" GOPATH="/Users/changkun/go" GOPRIVATE="" GOPROXY="https://proxy.golang.org,direct" GOROOT="/Users/changkun/dev/godev/go-gerrit" GOSUMDB="sum.golang.org" GOTMPDIR="" GOTOOLDIR="/Users/changkun/dev/godev/go-gerrit/pkg/tool/darwin_amd64" GCCGO="gccgo" AR="ar" CC="clang" CXX="clang++" CGO_ENABLED="1" GOMOD="/Users/changkun/dev/godev/tests/issue_27217/go.mod" CGO_CFLAGS="-g -O2" CGO_CPPFLAGS="" CGO_CXXFLAGS="-g -O2" CGO_FFLAGS="-g -O2" CGO_LDFLAGS="-g -O2" PKG_CONFIG="pkg-config" GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/jd/vym7tt9s2_379d4ccjcj1xrw0000gn/T/go-build781391859=/tmp/go-build -gno-record-gcc-switches -fno-common"
What did you do?
// main_test.go
func BenchmarkAtomic(b *testing.B) {
var v int32
atomic.StoreInt32(&v, 0)
b.Run("with-timer", func(b *testing.B) {
for i := 0; i < b.N; i++ {
b.StopTimer()
b.StartTimer()
atomic.AddInt32(&v, 1)
}
})
atomic.StoreInt32(&v, 0)
b.Run("w/o-timer", func(b *testing.B) {
for i := 0; i < b.N; i++ {
atomic.AddInt32(&v, 1)
}
})
}
Run benchmarks with the following command:
$ go test -run=none -bench=. -benchtime=1000x -count=20 | tee b.txt && benchstat b.txt
What did you expect to see?
Similar results for the with-timer
and w/o-timer
benchmarks
What did you see instead?
name time/op
Atomic/with-timer-6 63.0ns ±12%
Atomic/w/o-timer-6 4.90ns ± 1%