zero-copy

1 Preface Some time ago, I was involved in locating a problem with Tomcat that involved a sendfile system call. I suddenly thought of some of my previous experience with Java, and knew that there was a lot of open source software in the Java space that applied zero-copy to improve its performance, so I came up with this article. Look at these familiar software, have you ever understood the technical points behind their application:

Zero-copy in the Linux operating system Let’s start with the general I/O process of Linux This is a procedure that reads from a disk file and writes to it via socket, and the corresponding system call is as follows. read(file, tmp_buf, len); write(socket, tmp_buf, len); The program uses the read() system call to change the system from user state to kernel state, and the data from the disk is read into the kernel buffer by means of DMA (Direct memory access).