ZeroCopyÜbertragungen

ZeroCopyÜbertragungen, also known as zero-copy operations, are a technique in computer programming that aims to improve the efficiency of data transfer by minimizing or eliminating data copying between user space and kernel space. Traditionally, when data is transferred between an application and the operating system kernel, it involves multiple copies. For instance, reading a file and sending it over a network typically involves copying the data from the disk into a kernel buffer, then from the kernel buffer into a user-space buffer, and finally from the user-space buffer back into a kernel buffer for network transmission.

Zero-copy techniques circumvent these intermediate copies. Instead of moving the data, they allow the kernel to directly access or transfer data without it ever entering the application's address space. This can be achieved through various mechanisms. Memory mapping (mmap) is one common approach, where a file is mapped directly into the process's virtual address space, allowing the application to operate on the file's contents as if they were in memory, with the kernel handling the actual I/O operations. Another method is using `sendfile()` system calls, which enable the kernel to transfer data directly from a file descriptor to another, such as a socket, bypassing user space entirely.

The primary benefit of zero-copy is reduced CPU overhead and memory bandwidth usage, leading to significant performance improvements, especially in high-throughput applications like web servers and file transfer services. By avoiding redundant data movement, zero-copy operations can decrease latency and increase the overall system performance. However, implementing zero-copy can sometimes introduce complexity into application logic, as the application might not have direct access to the data in the same way it would with traditional copy-based methods.