fastlane

Fast multi-producer / single-consumer channels for Go.

A fastlane channel works similar to a standard Go channel with the following exceptions:

• It does not have a close method. A sender must send the receiver a custom close message.
• It's unbounded and has no buffering. Sending a message is a non-blocking O(1) operation.
• There can be multiple goroutines that call Send, but only one for Recv.

Just like standard Go channels, a fastlane channel guarantees order preservation and has no data loss.

Getting Started

Installing

To start using fastlane, install Go and run go get:

$ go get -u github.com/tidwall/fastlane

This will retrieve the library.

Usage

There're only two functions Send and Recv.

// chan.go
package main

import "github.com/tidwall/fastlane"

func main() {
	var ch fastlane.Chan

	go func() { ch.Send("ping") }()

	v := ch.Recv()
	println(v.(string))
}

$ go run chan.go 
ping

Channel types

There's currently three types of channels, Chan for interface{}, ChanUint64 for uint64, and ChanPointer for unsafe.Pointer.

The ChanUint64 and ChanPointer often perform better than the generic Chan and should be used when possible.

Here's a simple wrapper for creating a channel for sending a custom type as a pointer:

type MyType struct {
	Hiya string
}

type MyChan struct{ base fastlane.ChanPointer }

func (ch *MyChan) Send(value *MyType) {
	ch.base.Send(unsafe.Pointer(value))
}
func (ch *MyChan) Recv() *MyType {
	return (*MyType)(ch.base.Recv())
}

var ch MyChan

go func() { ch.Send(&MyType{Hiya: "howdy!"}) }()

v := ch.Recv()
println(v.Hiya)

Performance

The benchmark tests the speed of consuming integers from 100 producers.
go version go1.10.1

$ go test -run none -bench .

MacBook Pro 15" 2.8 GHz Intel Core i7 (darwin/amd64)

Benchmark100ProducerFastlaneChan-8       	20000000	        85.9 ns/op
Benchmark100ProducerGoChan100-8          	 3000000	       569 ns/op
Benchmark100ProducerGoChan10-8           	 2000000	       728 ns/op
Benchmark100ProducerGoChanUnbuffered-8   	 2000000	       686 ns/op

Mac mini i7-3615QM CPU @ 2.30GHz (linux/amd64)

Benchmark100ProducerFastlaneChan-8       	20000000	       101 ns/op
Benchmark100ProducerGoChan100-8          	 3000000	       424 ns/op
Benchmark100ProducerGoChan10-8           	 2000000	       586 ns/op
Benchmark100ProducerGoChanUnbuffered-8   	 2000000	       790 ns/op

Raspberry Pi 3 (linux/arm64)

Benchmark100ProducerFastlaneChan-4       	10000000	       179 ns/op
Benchmark100ProducerGoChan100-4          	 2000000	       976 ns/op
Benchmark100ProducerGoChan10-4           	 1000000	      1043 ns/op
Benchmark100ProducerGoChanUnbuffered-4   	 1000000	      1093 ns/op

Raspberry Pi 3 (linux/arm)

Benchmark100ProducerFastlaneChan-4       	 5000000	       279 ns/op
Benchmark100ProducerGoChan100-4          	 1000000	      1345 ns/op
Benchmark100ProducerGoChan10-4           	 1000000	      1371 ns/op
Benchmark100ProducerGoChanUnbuffered-4   	 1000000	      1635 ns/op

Contact

Josh Baker @tidwall

License

fastlane source code is available under the MIT License.