What version of Go are you using (go version)?
$ go version
go version go1.11 linux/amd64
Applies to earlier versions as well
Does this issue reproduce with the latest release?
Yes
What operating system and processor architecture are you using (go env)?
go env Output
$ go env
GOARCH="amd64"
GOBIN=""
GOCACHE="/root/.cache/go-build"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/go"
GOPROXY=""
GORACE=""
GOROOT="/usr/local/go"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/linux_amd64"
GCCGO="gccgo"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD=""
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 -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build896591388=/tmp/go-build -gno-record-gcc-switches"
What did you do?
Using the following test file:
package bechmarkperf
import (
"strconv"
"testing"
"time"
)
func BenchmarkSleepSerial(b *testing.B) {
for i := 0; i < b.N; i++ {
sleepFunc()
}
}
func BenchmarkSleepParallel(b *testing.B) {
for i := 1; i <= 8; i *= 2 {
b.Run(strconv.Itoa(i), func(b *testing.B) {
b.SetParallelism(i)
b.RunParallel(func(pb *testing.PB) {
for pb.Next() {
sleepFunc()
}
})
})
}
}
func sleepFunc() {
time.Sleep(1 * time.Millisecond)
}
Running in parallel, results were ~1ms / for ns/op. This mean that doubling threadcount would halve ns/op.
What did you expect to see?
ns/op hold the same and not go below 1ms.
What did you see instead?
When running with 128 goroutines, go the following output:
BenchmarkSleepParallel/8-16 100000 12024 ns/op 0 B/op 0 allocs/op
This is reporting that the benchmark process is taking well under 1ms (which is the sleep duration above).
What version of Go are you using (
go version)?Applies to earlier versions as well
Does this issue reproduce with the latest release?
Yes
What operating system and processor architecture are you using (
go env)?go envOutputWhat did you do?
Using the following test file:
Running in parallel, results were ~1ms / for
ns/op. This mean that doubling threadcount would halve ns/op.What did you expect to see?
ns/op hold the same and not go below 1ms.
What did you see instead?
When running with 128 goroutines, go the following output:
This is reporting that the benchmark process is taking well under 1ms (which is the sleep duration above).