一个简单的规则，当我应该使用Java NIO的直接缓冲区网络I / O？ [英] A simple rule of when I should use direct buffers with Java NIO for network I/O?

问题描述

有自然礼物的人能以简单直接的方式解释复杂的事情吗？为了获得最佳性能，当我在使用Java NIO进行网络I / O时，应该使用直接ByteBuffers还是常规ByteBuffers？

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例如：我应该读一个堆缓冲区并从那里解析它，做许多get（）（逐字节）或者我应该把它读入一个直接缓冲区并从直接缓冲区解析？

为了获得最佳性能，当我使用Java NIO进行网络I / O时，应该使用直接ByteBuffers和普通ByteBuffers？ p>

直接缓冲区有许多优点

• 避免在Java和本机内存之间传递的数据的额外副本。


• 如果重新使用，只有使用的页面变成真正的内存。这意味着你可以使他们比他们需要的更大，他们只浪费虚拟内存。


• 您可以有效地访问本地字节顺序的多字节基元。 （基本上一个机器码指令）

如果我读入堆缓冲区并从那里解析，做许多get（）（逐字节）或者我应该读它到一个直接缓冲区并从直接缓冲区解析？

你一次读一个字节，你可能没有多大的优势。但是，使用直接字节缓冲区，您可以一次读取2或4个字节，并一次有效地解析多个字节。

] [selectors]

如果你正在解析实时数据，我会避免使用选择器。我发现使用阻塞NIO或忙等待NIO可以给你最低的延迟性能（假设你有一个相对较少的连接数，例如高达20）

Can someone with the natural gift to explain complex things in an easy and straightforward way address this question? To acquire the best performance when should I use direct ByteBuffers versus regular ByteBuffers when doing network I/O with Java NIO?

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For example: Should I read into a heap buffer and parse it from there, doing many get() (byte by byte) OR should I read it into a direct buffer and parse from the direct buffer?

解决方案

To acquire the best performance when should I use direct ByteBuffers versus regular ByteBuffers when doing network I/O with Java NIO?

Direct buffers have a number of advantages

• The avoid an extra copy of data passed between Java and native memory.
• If they are re-used, only the page used are turning into real memory. This means you can make them much larger than they need to me and they only waste virtual memory.
• You can access multi-byte primitives in native byte order efficiently. (Basically one machine code instruction)

Should I read into a heap buffer and parse it from there, doing many get() (byte by byte) OR should I read it into a direct buffer and parse from the direct buffer?

If you are reading a byte at a time, you may not get much advantage. However, with a direct byte buffer you can read 2 or 4 bytes at a time and effectively parse multiple bytes at once.

[real time] [selectors]

If you are parsing real time data, I would avoid using selectors. I have found using blocking NIO or busy waiting NIO can give you the lowest latency performance (assuming you have a relatively small number of connections e.g. up to 20)

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