开年来的第一份工作，就是在最新的内核上打补丁。
可没想到Nagle算法也被我冲进了去年的垃圾桶里。
在网上找了一些资料，理论很快被消化，但看了看内核的实现，久久没能动弹。坐了一天，才摸索出来点什么，觉得需要一份代码解释TCP-Nagle的版本说明，这样和Nagle算法的黑盒解释，才能对TCP-Nagle有全面的理解。
于是，有了本文。
Nagle算法
RFC对Nagle算法解释
Nagle’s algorithm, named after John Nagle, is a means of improving the efficiency of TCP/IP networks
by reducing the number of packets that need to be sent over the network.
Nagle’s algorithm works by combining a number of small outgoing messages, and sending them
all at once. Specifically, as long as there is a sent packet for which the sender has received no
acknowledgment, the sender should keep buffering its output until it has a full packet’s worth of output,
so that output can be sent all at once.
Nagle’s algorithm purposefully delays transmission, increasing bandwidth efficiency at the expense of latency.
中文意思是：TCP-Nagle避免发送大量的小包（阻塞小包，粘合成大包），减少传输次数，但会有延迟的牺牲。
至于为什么会这样，大佬的文章已经有详细的展开，最后会贴上链接，欢迎去阅读。
TCP-Nagle的逻辑
if there is new data to sendif the window size >= MSS and available data is >= MSSsend complete MSS segment nowelseif there is unconfirmed data still in the pipeenqueue data in the buffer until an acknowledge is receivedelsesend data immediatelyend ifend if
end if
TCP-Nagle 图解
Nagle图解完全依赖最新的内核实现。