I'm playing around with benchmarks in Go and I have a simple function that just sleeps for 5 Nanoseconds, however when I run a benchmark test it shows 298.1 ns/op. I'm curious why is that. Shouldn't it be 5 ns/op?
Go version:
go version go1.19 linux/amd64
The code:
package andrei
import (
"testing"
"time"
)
func Hi() {
time.Sleep(5 * time.Nanosecond)
}
func BenchmarkHi(b *testing.B) {
for i := 0; i < b.N; i++ {
Hi()
}
}
The results:
$ go test -run none -bench . -benchmem ./andrei
goos: linux
goarch: amd64
pkg: andrei/andrei
cpu: 11th Gen Intel(R) Core(TM) i7-1165G7 @ 2.80GHz
BenchmarkHi-8 3861392 298.1 ns/op 0 B/op 0 allocs/op
PASS
ok andrei/andrei 1.470s
time.Sleep only guarantees that it will sleep at least as long as the argument. How long it actually sleeps depends on your operating system and other factors.
On Windows, it sleeps at least 1.9ms. On my MacBook, I get 408 ns/op, and you are seeing 298.1 ns/op.
You can find out more details about this problem in this ticket in the Go github repository: