Fix unfair comparison to unbuffered channels in sleep_test.go.

Consider the following benchmark, which is equivalent to
BenchmarkSleeperWaitOnSingleSelect with names changed to more closely reflect
the behavior of BenchmarkGoWaitOnSingleSelect:

	var (
		empty     Sleeper
		emptyCond Waker
		full      Sleeper
		fullCond  Waker
	)
	empty.AddWaker(&emptyCond)
	full.AddWaker(&fullCond)
	go func() {
		for i := 0; i < b.N; i++ {
			empty.Fetch(true)
			fullCond.Assert()
		}
	}()
	for i := 0; i < b.N; i++ {
		emptyCond.Assert()
		full.Fetch(true)
	}

The unfairness arises because runtime.chansend and runtime.chanrecv don't
actually work this way. If runtime.chansend blocks, it has already enqueued the
element to be sent on runtime.hchan.sendq, which runtime.chanrecv dequeues
before calling goready(); in sleep-like terms, by the time empty.Fetch()
returns, fullCond.Assert() has already happened and been fetched by the other
goroutine. The same property applies to runtime.chanrecv/runtime.hchan.recvq.
This property has no correspondence to the actual usage of the sleep package,
so change the channel benchmarks to explicitly exchange control using buffered
channels instead. Also remove some stale comments and align the syncevent
benchmarks with the sleep ones.

BenchmarkSleeperWaitOnSingleSelect
BenchmarkSleeperWaitOnSingleSelect-12    	 2118603	       472.5 ns/op
BenchmarkGoWaitOnSingleSelect
BenchmarkGoWaitOnSingleSelect-12         	 2224262	       517.7 ns/op
BenchmarkSleeperWaitOnMultiSelect
BenchmarkSleeperWaitOnMultiSelect-12     	 2630569	       459.8 ns/op
BenchmarkGoWaitOnMultiSelect
BenchmarkGoWaitOnMultiSelect-12          	  807918	      1312 ns/op

BenchmarkWaiterPingPong
BenchmarkWaiterPingPong-12          	 2955579	       385.8 ns/op
BenchmarkSleeperPingPong
BenchmarkSleeperPingPong-12         	 2454367	       474.3 ns/op
BenchmarkChannelPingPong
BenchmarkChannelPingPong-12         	 2302662	       513.5 ns/op
BenchmarkWaiterPingPongMulti
BenchmarkWaiterPingPongMulti-12     	 3023676	       388.8 ns/op
BenchmarkSleeperPingPongMulti
BenchmarkSleeperPingPongMulti-12    	 2574064	       471.5 ns/op
BenchmarkChannelPingPongMulti
BenchmarkChannelPingPongMulti-12    	 1000000	      1088 ns/op

PiperOrigin-RevId: 407760956

0 files changed, 0 insertions, 0 deletions