英文:
What is channel buffer size?
问题
我正在尝试创建一个异步通道，我一直在查看http://golang.org/ref/spec#Making_slices_maps_and_channels。
c := make(chan int, 10) // 缓冲大小为10的通道
缓冲大小为10是什么意思？具体来说，缓冲大小表示/限制了什么？
英文:
I'm trying to create an asynchronous channel and I've been looking at http://golang.org/ref/spec#Making_slices_maps_and_channels.
c := make(chan int, 10) // channel with a buffer size of 10
What does it mean that the buffer size is 10? What specifically does the buffer size represent/limit?
答案1
得分: 203
缓冲区大小是指在发送阻塞之前可以发送到通道的元素数量。默认情况下，通道的缓冲区大小为0（使用make(chan int)可以得到这个）。这意味着每次发送都会阻塞，直到另一个goroutine从通道接收。缓冲区大小为1的通道可以容纳1个元素，直到发送阻塞，所以你会得到：
c := make(chan int, 1)
c <- 1 // 不会阻塞
c <- 2 // 阻塞，直到另一个goroutine从通道接收
英文:
The buffer size is the number of elements that can be sent to the channel without the send blocking. By default, a channel has a buffer size of 0 (you get this with make(chan int)). This means that every single send will block until another goroutine receives from the channel. A channel of buffer size 1 can hold 1 element until sending blocks, so you'd get
c := make(chan int, 1)
c <- 1 // doesn't block
c <- 2 // blocks until another goroutine receives from the channel
答案2
得分: 21
以下代码演示了无缓冲通道的阻塞：
// 若要查看差异，请将0更改为1
c := make(chan struct{}, 0)
go func() {
time.Sleep(2 * time.Second)
<-c
}()
start := time.Now()
c <- struct{}{} // 如果通道大小为0，则阻塞
elapsed := time.Since(start)
fmt.Printf("Elapsed: %v\n", elapsed)
您可以在此处尝试运行代码（https://play.golang.org/p/KHkrkxCVdQ）。
英文:
The following code illustrates the blocking of unbuffered channel:
// to see the diff, change 0 to 1
c := make(chan struct{}, 0)
go func() {
time.Sleep(2 * time.Second)
<-c
}()
start := time.Now()
c <- struct{}{} // block, if channel size is 0
elapsed := time.Since(start)
fmt.Printf("Elapsed: %v\n", elapsed)
You may play with the code here.
答案3
得分: 2
package main
import (
"fmt"
"time"
)
func receiver(ch <-chan int) {
time.Sleep(500 * time.Millisecond)
msg := <-ch
fmt.Printf("从通道接收到消息 %d\n", msg)
}
func main() {
start := time.Now()
zero_buffer_ch := make(chan int, 0)
go receiver(zero_buffer_ch)
zero_buffer_ch <- 444
elapsed := time.Since(start)
fmt.Printf("使用零缓冲通道的时间: %v\n", elapsed)
restart := time.Now()
non_zero_buffer_ch := make(chan int, 1)
go receiver(non_zero_buffer_ch)
non_zero_buffer_ch <- 4444
reelapsed := time.Since(restart)
fmt.Printf("使用非零缓冲通道的时间: %v\n", reelapsed)
}
英文:
package main
import (
"fmt"
"time"
)
func receiver(ch <-chan int) {
time.Sleep(500 * time.Millisecond)
msg := <-ch
fmt.Printf("receive messages %d from the channel\n", msg)
}
func main() {
start := time.Now()
zero_buffer_ch := make(chan int, 0)
go receiver(zero_buffer_ch)
zero_buffer_ch <- 444
elapsed := time.Since(start)
fmt.Printf("Elapsed using zero_buffer channel: %v\n", elapsed)
restart := time.Now()
non_zero_buffer_ch := make(chan int, 1)
go receiver(non_zero_buffer_ch)
non_zero_buffer_ch <- 4444
reelapsed := time.Since(restart)
fmt.Printf("Elapsed using non zero_buffer channel: %v\n", reelapsed)
}
result:
receive messages 444 from the channel
Elapsed using zero_buffer channel: 505.6729ms
Elapsed using non zero_buffer channel: 0s
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