在接收管道数据的应用程序中使用mmap（）？

Question

Is it possible to use mmap() in a C++ application on Linux which must receive piped input from a file and if so, is this faster than reading individual/page_amount bytes from the stream?

I'm not sure mmap() is possible because piping involves a stream whereas wouldnt mmap() require all of the data availale immediately?

Answer 1

You can not mmap a stream because data in a stream buffer is intended to be read only once. Also the length of receivable data is indeterminable at runtime. Your best bet is to mmap a sufficient amount of memory and then use it as a receiving buffer.

If you are using stdio functions to read data form your stream then the chunk size won't matter. The library will automatically choose the most optimal one (often one page at a time). But if you intend to use read then reading in chunks of pages will give you the best performance.