优化内存空间，提升读写速度
文章链接:https://codemouse.online/archives/2020-03-28201251posix_fadvise与fallocate#include <fcntl.h> int posix_fadvise(int fd, off_t offset, off_t len, int advice);int fallocate(int fd, int mode, off_t offset, off_t len);advice的参数：标签描述
