mirror of
https://github.com/golang/go
synced 2024-11-25 09:47:57 -07:00
d073677569
Fixes #4008. Run a background goroutine that wastes CPU to trick the power management into raising the CPU frequency which, by side effect, makes sleep more accurate on arm. === RUN TestParallelSleep --- PASS: TestParallelSleep (1.30 seconds) _cgo_gotypes.go:772: sleep(1) slept for 1.000458s R=minux.ma, r CC=golang-dev https://golang.org/cl/6498060
72 lines
1.5 KiB
Go
72 lines
1.5 KiB
Go
// Copyright 2011 The Go Authors. All rights reserved.
|
|
// Use of this source code is governed by a BSD-style
|
|
// license that can be found in the LICENSE file.
|
|
|
|
package cgotest
|
|
|
|
/*
|
|
#include <unistd.h>
|
|
|
|
unsigned int sleep(unsigned int seconds);
|
|
|
|
extern void BackgroundSleep(int);
|
|
void twoSleep(int);
|
|
*/
|
|
import "C"
|
|
|
|
import (
|
|
"runtime"
|
|
"testing"
|
|
"time"
|
|
)
|
|
|
|
var sleepDone = make(chan bool)
|
|
|
|
func parallelSleep(n int) {
|
|
C.twoSleep(C.int(n))
|
|
<-sleepDone
|
|
}
|
|
|
|
//export BackgroundSleep
|
|
func BackgroundSleep(n int) {
|
|
go func() {
|
|
C.sleep(C.uint(n))
|
|
sleepDone <- true
|
|
}()
|
|
}
|
|
|
|
// wasteCPU starts a background goroutine to waste CPU
|
|
// to cause the power management to raise the CPU frequency.
|
|
// On ARM this has the side effect of making sleep more accurate.
|
|
func wasteCPU() chan struct{} {
|
|
done := make(chan struct{})
|
|
go func() {
|
|
for {
|
|
select {
|
|
case <-done:
|
|
return
|
|
default:
|
|
}
|
|
}
|
|
}()
|
|
// pause for a short amount of time to allow the
|
|
// power management to recognise load has risen.
|
|
<-time.After(300 * time.Millisecond)
|
|
return done
|
|
}
|
|
|
|
func testParallelSleep(t *testing.T) {
|
|
defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(2))
|
|
defer close(wasteCPU())
|
|
|
|
sleepSec := 1
|
|
start := time.Now()
|
|
parallelSleep(sleepSec)
|
|
dt := time.Since(start)
|
|
t.Logf("sleep(%d) slept for %v", sleepSec, dt)
|
|
// bug used to run sleeps in serial, producing a 2*sleepSec-second delay.
|
|
if dt >= time.Duration(sleepSec)*1300*time.Millisecond {
|
|
t.Fatalf("parallel %d-second sleeps slept for %f seconds", sleepSec, dt.Seconds())
|
|
}
|
|
}
|