问题描述
我认为mmap并不像使用虚拟内存那么快，它仍然具有硬盘I / O.
I think mmap is not fast as using virtual memory, it still has harddisk I/O.
但互联网上有很多人说它很快，但没有理由。
But many people on Internet say it's fast, but no reason.
在我的测试中，我使用BufferedReader和MappedByteBuffer读取文件，第一个更快。
In my test, I read a file using BufferedReader andMappedByteBuffer, the first one is faster.
推荐答案
MappedByteBuffer 适合读取不按顺序读取的二进制文件。
A MappedByteBuffer is suitable for reading binary files that are not read sequentially.
一个示例是读取包含
树数据结构的数据库索引文件，其中文件偏移量到文件的其他部分。在这个
的情况下，你不断在文件中寻找前进和后退，并且
读取数据和
我的测试显示使用 MappedByteBuffer 比使用
RandomAccessFile 快得多。
An example is reading a database index file containingtree data-structures with file offsets to other parts of the file. In thiscase, you are continually seeking forwards and backwards in the file andreading data andmy tests showed that using a MappedByteBuffer was much faster than using aRandomAccessFile.
按顺序读取文本文件或二进制文件 BufferedReader
或 BufferedInputStream 效率很高。使用
a内存映射文件通常没有优势，管理内存映射
的开销可能会使 MappedByteBuffer 慢于 BufferedReader 或 BufferedInputStream 。
Reading a text file or binary file sequentially with a BufferedReaderor BufferedInputStream is efficient. There is normally no advantage in usinga memory mapped file for this and the overhead of managing the memory mappingwill probably make a MappedByteBuffer slower than a BufferedReader or BufferedInputStream.
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