插座＆QUOT;冲洗＆QUOT;通过暂时使无延迟 [英] Socket "Flush" by temporarily enabling NoDelay

问题描述

我在C＃中的HTTP服务器的实现。 使用 AB 我发现了一个奇怪的性能问题。 每个请求了5毫秒保活关，但40毫秒，保活的！

I have an implementation of an HTTP server in C#. Using ab I discovered a weird performance issue. Each request took 5 ms with Keep-Alive Off but 40 ms with Keep-Alive on!

该testpage生成到一个字节[]，它使用一个单一的socket.Send呼叫被发送的答复。

The testpage is generated into a single byte[] which get sent as reply using a single socket.Send call.

原因是，据我可以告诉在TCP堆栈使用Nagle算法。

The cause is as far as I can tell Nagle's algorithm used in the TCP stack.

到目前为止，我现在用的是无需等待在每个HTTP请求的高端物业服务。

So far I am using the NoDelay property in the end of every HTTP request served.

socket.NoDelay = true;
socket.NoDelay = false;

这确实解决了问题了。但我没有文档备份我的发现。

Which does solve the problem for now. But I have no documentation to backup my discovery.

这是在Linux /单系统测试。

This was tested on a linux/mono system.

有冲洗TCP连接的标准方式？

<一个href="http://stackoverflow.com/questions/1781766/paste-httpserver-and-slowdown-with-http-1-1-keep-alive-tested-with-httperf-and-a/1795352#1795352">This答案是解决同样的问题。这里的区别是，我希望只是暂时禁用该算法。

This answer is addressing the same issue. The difference here is that I am looking to only temporarily disabling the algorithm.

推荐答案

我测试了使用Wireshark。不幸的是，

I tested this with Wireshark. Unfortunately,

socket.NoDelay = true;
socket.NoDelay = false;

没有效果。同样，

has no effect. Similarly,

socket.NoDelay = true;
socket.Send(new byte[0]);
socket.NoDelay = false;

也没有任何影响。从观察到的行为，看来，无延迟属性只影响下次调用发送与非空缓冲区。换句话说，你必须无延迟之前发送一些实际的数据会产生什么影响。

also has no effect. From observed behaviour, it appears that the NoDelay property only affects the next call to Send with a non-empty buffer. In other words, you have to send some actual data before NoDelay will have any effect.

所以，我的结论是没有办法明确刷新插槽，如果你不想发送任何额外的数据。

Therefore, I conclude that there is no way to explicitly flush the socket if you don’t want to send any extra data.

不过，既然你正在编写一个HTTP服务器，你可以使用一些小技巧：

However, since you are writing an HTTP server, you may be able to use a few tricks:

• 对于使用传输编码处理的请求：分块，您可以将尾流的标志（在\ r \ N0 \ r \ñ\ r \ N）使用无需等待= TRUE 。
• 如果您是从本地文件系统提供的文件，你就会知道文件结束的时候，所以你可以设置无需等待= TRUE 刚刚发送的最后一块了。
• 对于使用内容编码处理的请求：GZIP ，你可以设置无延迟=真正的结束之前使用gzip流; gzip的流将前实际完成和关闭发送一些最后一位。

• For requests that are served using Transfer-Encoding: chunked, you can send the end-of-stream marker (the "\r\n0\r\n\r\n") with NoDelay = true.
• If you are serving a file from the local filesystem, you will know when the file ends, so you could set NoDelay = true just before sending the last chunk.
• For requests that are served using Content-Encoding: gzip, you can set NoDelay = true just before closing the gzip stream; the gzip stream will send some last bits before actually finishing and closing.

我当然要加上面的我的HTTP服务器现在：）

I’m certainly going to add the above to my HTTP server now :)

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