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time: add Ticker.Reset

This CL implements Ticker.Reset method in time package.

Benchmark:
name                 time/op
TickerReset-12       6.41µs ±10%
TickerResetNaive-12  95.7µs ±12%

Fixes #33184

Change-Id: I12c651f81e452541bcbbc748b45f038aae1f8dae
Reviewed-on: https://go-review.googlesource.com/c/go/+/217362
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
This commit is contained in:
Changkun Ou 2020-02-03 14:42:32 +01:00 committed by Ian Lance Taylor
parent ebe49b2c29
commit 6e5652bebe
6 changed files with 55 additions and 3 deletions

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@ -1 +1,2 @@
pkg testing, method (*T) Deadline() (time.Time, bool)
pkg time, method (*Ticker) Reset(Duration)

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@ -80,3 +80,13 @@ TODO
<p>
TODO
</p>
<dl id="time"><dt><a href="/pkg/time/">time</a></dt>
<dd>
<p><!-- golang.org/issue/33184 -->
The new method
<a href="/pkg/time#Ticker.Reset"><code>Ticker.Reset</code></a>
supports changing the duration of a ticker.
</p>
</dd>
</dl><!-- time -->

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@ -233,6 +233,12 @@ func resetTimer(t *timer, when int64) {
resettimer(t, when)
}
// modTimer modifies an existing timer.
//go:linkname modTimer time.modTimer
func modTimer(t *timer, when, period int64, f func(interface{}, uintptr), arg interface{}, seq uintptr) {
modtimer(t, when, period, f, arg, seq)
}
// Go runtime.
// Ready the goroutine arg.
@ -402,7 +408,7 @@ func dodeltimer0(pp *p) bool {
}
// modtimer modifies an existing timer.
// This is called by the netpoll code.
// This is called by the netpoll code or time.Ticker.Reset.
func modtimer(t *timer, when, period int64, f func(interface{}, uintptr), arg interface{}, seq uintptr) {
if when < 0 {
when = maxWhen

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@ -39,6 +39,7 @@ func when(d Duration) int64 {
func startTimer(*runtimeTimer)
func stopTimer(*runtimeTimer) bool
func resetTimer(*runtimeTimer, int64)
func modTimer(t *runtimeTimer, when, period int64, f func(interface{}, uintptr), arg interface{}, seq uintptr)
// The Timer type represents a single event.
// When the Timer expires, the current time will be sent on C,

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@ -46,6 +46,15 @@ func (t *Ticker) Stop() {
stopTimer(&t.r)
}
// Reset stops a ticker and resets its period to the specified duration.
// The next tick will arrive after the new period elapses.
func (t *Ticker) Reset(d Duration) {
if t.r.f == nil {
panic("time: Reset called on uninitialized Ticker")
}
modTimer(&t.r, when(d), int64(d), t.r.f, t.r.arg, t.r.seq)
}
// Tick is a convenience wrapper for NewTicker providing access to the ticking
// channel only. While Tick is useful for clients that have no need to shut down
// the Ticker, be aware that without a way to shut it down the underlying

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@ -36,13 +36,17 @@ func TestTicker(t *testing.T) {
for i := 0; i < 5; i++ {
ticker := NewTicker(delta)
t0 := Now()
for i := 0; i < count; i++ {
for i := 0; i < count/2; i++ {
<-ticker.C
}
ticker.Reset(delta * 2)
for i := count / 2; i < count; i++ {
<-ticker.C
}
ticker.Stop()
t1 := Now()
dt := t1.Sub(t0)
target := delta * Duration(count)
target := 3 * delta * Duration(count/2)
slop := target * 2 / 10
if dt < target-slop || dt > target+slop {
errs = append(errs, fmt.Sprintf("%d %s ticks took %s, expected [%s,%s]", count, delta, dt, target-slop, target+slop))
@ -118,3 +122,24 @@ func BenchmarkTicker(b *testing.B) {
ticker.Stop()
})
}
func BenchmarkTickerReset(b *testing.B) {
benchmark(b, func(n int) {
ticker := NewTicker(Nanosecond)
for i := 0; i < n; i++ {
ticker.Reset(Nanosecond * 2)
}
ticker.Stop()
})
}
func BenchmarkTickerResetNaive(b *testing.B) {
benchmark(b, func(n int) {
ticker := NewTicker(Nanosecond)
for i := 0; i < n; i++ {
ticker.Stop()
ticker = NewTicker(Nanosecond * 2)
}
ticker.Stop()
})
}