Demo: Copy a File Using an mmap Buffer

The fourth and last variant of the file-copy program. This one skips the allocator and asks the kernel for the buffer directly, with mmap(): an anonymous mapping, with no file behind it, that becomes a new area of the process address space and is handed back with munmap().

Together with the teaching assistant you will fill in the TODOs in copy_file.c, build it and copy a file, then run the malloc variant and this one under strace and compare what reaches the kernel. The question to leave with: if malloc() ends up calling mmap() for a buffer this size anyway, what does calling it yourself buy, and what does it cost?