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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>
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@ -1 +1,2 @@
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pkg testing, method (*T) Deadline() (time.Time, bool)
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pkg time, method (*Ticker) Reset(Duration)
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@ -80,3 +80,13 @@ TODO
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<p>
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TODO
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</p>
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<dl id="time"><dt><a href="/pkg/time/">time</a></dt>
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<dd>
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<p><!-- golang.org/issue/33184 -->
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The new method
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<a href="/pkg/time#Ticker.Reset"><code>Ticker.Reset</code></a>
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supports changing the duration of a ticker.
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</p>
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</dd>
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</dl><!-- time -->
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@ -233,6 +233,12 @@ func resetTimer(t *timer, when int64) {
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resettimer(t, when)
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}
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// modTimer modifies an existing timer.
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//go:linkname modTimer time.modTimer
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func modTimer(t *timer, when, period int64, f func(interface{}, uintptr), arg interface{}, seq uintptr) {
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modtimer(t, when, period, f, arg, seq)
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}
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// Go runtime.
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// Ready the goroutine arg.
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@ -402,7 +408,7 @@ func dodeltimer0(pp *p) bool {
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}
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// modtimer modifies an existing timer.
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// This is called by the netpoll code.
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// This is called by the netpoll code or time.Ticker.Reset.
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func modtimer(t *timer, when, period int64, f func(interface{}, uintptr), arg interface{}, seq uintptr) {
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if when < 0 {
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when = maxWhen
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@ -39,6 +39,7 @@ func when(d Duration) int64 {
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func startTimer(*runtimeTimer)
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func stopTimer(*runtimeTimer) bool
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func resetTimer(*runtimeTimer, int64)
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func modTimer(t *runtimeTimer, when, period int64, f func(interface{}, uintptr), arg interface{}, seq uintptr)
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// The Timer type represents a single event.
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// When the Timer expires, the current time will be sent on C,
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@ -46,6 +46,15 @@ func (t *Ticker) Stop() {
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stopTimer(&t.r)
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}
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// Reset stops a ticker and resets its period to the specified duration.
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// The next tick will arrive after the new period elapses.
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func (t *Ticker) Reset(d Duration) {
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if t.r.f == nil {
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panic("time: Reset called on uninitialized Ticker")
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}
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modTimer(&t.r, when(d), int64(d), t.r.f, t.r.arg, t.r.seq)
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}
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// Tick is a convenience wrapper for NewTicker providing access to the ticking
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// channel only. While Tick is useful for clients that have no need to shut down
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// 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) {
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for i := 0; i < 5; i++ {
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ticker := NewTicker(delta)
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t0 := Now()
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for i := 0; i < count; i++ {
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for i := 0; i < count/2; i++ {
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<-ticker.C
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}
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ticker.Reset(delta * 2)
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for i := count / 2; i < count; i++ {
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<-ticker.C
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}
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ticker.Stop()
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t1 := Now()
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dt := t1.Sub(t0)
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target := delta * Duration(count)
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target := 3 * delta * Duration(count/2)
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slop := target * 2 / 10
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if dt < target-slop || dt > target+slop {
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errs = append(errs, fmt.Sprintf("%d %s ticks took %s, expected [%s,%s]", count, delta, dt, target-slop, target+slop))
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@ -118,3 +122,24 @@ func BenchmarkTicker(b *testing.B) {
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ticker.Stop()
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})
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}
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func BenchmarkTickerReset(b *testing.B) {
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benchmark(b, func(n int) {
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ticker := NewTicker(Nanosecond)
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for i := 0; i < n; i++ {
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ticker.Reset(Nanosecond * 2)
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}
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ticker.Stop()
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})
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}
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func BenchmarkTickerResetNaive(b *testing.B) {
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benchmark(b, func(n int) {
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ticker := NewTicker(Nanosecond)
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for i := 0; i < n; i++ {
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ticker.Stop()
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ticker = NewTicker(Nanosecond * 2)
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}
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ticker.Stop()
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})
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}
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