hrtime
Package hrtime implements high-resolution timing functions and benchmarking utilities.
hrtime
relies on using the best timing mechanism on a particular system. At the moment, for Windows it is using Performance Counters and on other platforms standard time.Now
(since it's good enough).
Package also supports using hardware time stamp counters (TSC). They offer better accuracy and on some platforms correspond to the processor cycles. However, they are not supported on all platforms.
For example measuring time.Sleep
on Mac and Windows.
Example
package main
import (
"fmt"
"time"
"github.com/loov/hrtime"
)
func main() {
start := hrtime.Now()
time.Sleep(1000 * time.Nanosecond)
fmt.Println(hrtime.Since(start))
const numberOfExperiments = 4096
bench := hrtime.NewBenchmark(numberOfExperiments)
for bench.Next() {
time.Sleep(1000 * time.Nanosecond)
}
fmt.Println(bench.Histogram(10))
}
Output on Mac:
12ยตs
avg 14.5ยตs; min 2ยตs; p50 12ยตs; max 74ยตs;
p90 22ยตs; p99 44ยตs; p999 69ยตs; p9999 74ยตs;
2ยตs [ 229] โโโ
10ยตs [3239] โโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโ
20ยตs [ 483] โโโโโโ
30ยตs [ 80] โ
40ยตs [ 39] โ
50ยตs [ 17] โ
60ยตs [ 6]
70ยตs [ 3]
80ยตs [ 0]
90ยตs [ 0]
Output on Windows:
1.5155ms
avg 1.49ms; min 576ยตs; p50 1.17ms; max 2.47ms;
p90 2.02ms; p99 2.3ms; p999 2.37ms; p9999 2.47ms;
577ยตs [ 1]
600ยตs [ 57] โโ
800ยตs [ 599] โโโโโโโโโโโโโโโโโ
1ms [1399] โโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโโ
1.2ms [ 35] โ
1.4ms [ 7]
1.6ms [ 91] โโโ
1.8ms [ 995] โโโโโโโโโโโโโโโโโโโโโโโโโโโโ
2ms [ 778] โโโโโโโโโโโโโโโโโโโโโโ
2.2ms [ 134] โโโโ
A full explanation why it outputs this is out of the scope of this document. However, all sleep instructions have a specified granularity and time.Sleep
actual sleeping time is requested time ยฑ sleep granularity
. There are also other explanations to that behavior.
Benchmarking
hrtime/hrtesting
can be used to supplement existing benchmarks with more details:
package hrtesting_test
import (
"fmt"
"runtime"
"testing"
"github.com/loov/hrtime/hrtesting"
)
func BenchmarkReport(b *testing.B) {
bench := hrtesting.NewBenchmark(b)
defer bench.Report()
for bench.Next() {
r := fmt.Sprintf("hello, world %d", 123)
runtime.KeepAlive(r)
}
}