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https://github.com/golang/go
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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.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package cgotest
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/*
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#include <unistd.h>
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unsigned int sleep(unsigned int seconds);
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extern void BackgroundSleep(int);
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void twoSleep(int);
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*/
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import "C"
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import (
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"runtime"
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"testing"
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"time"
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)
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var sleepDone = make(chan bool)
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func parallelSleep(n int) {
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C.twoSleep(C.int(n))
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<-sleepDone
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}
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//export BackgroundSleep
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func BackgroundSleep(n int) {
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go func() {
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C.sleep(C.uint(n))
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sleepDone <- true
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}()
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}
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// wasteCPU starts a background goroutine to waste CPU
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// to cause the power management to raise the CPU frequency.
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// On ARM this has the side effect of making sleep more accurate.
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func wasteCPU() chan struct{} {
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done := make(chan struct{})
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go func() {
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for {
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select {
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case <-done:
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return
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default:
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}
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}
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}()
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// pause for a short amount of time to allow the
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// power management to recognise load has risen.
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<-time.After(300 * time.Millisecond)
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return done
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}
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func testParallelSleep(t *testing.T) {
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defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(2))
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defer close(wasteCPU())
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sleepSec := 1
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start := time.Now()
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parallelSleep(sleepSec)
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dt := time.Since(start)
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t.Logf("sleep(%d) slept for %v", sleepSec, dt)
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// bug used to run sleeps in serial, producing a 2*sleepSec-second delay.
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if dt >= time.Duration(sleepSec)*1300*time.Millisecond {
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t.Fatalf("parallel %d-second sleeps slept for %f seconds", sleepSec, dt.Seconds())
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}
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}
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