C++ epoll select poll

Epoll, select, and poll are all I/O multiplexing mechanisms used in Linux to handle multiple I/O operations with a single thread. They allow a program to wait for multiple I/O operations without blocking, thus improving the overall efficiency of the program.

Select is the oldest mechanism and is available on most Unix-like systems. It works by monitoring a set of file descriptors and notifying the program when an I/O operation is ready to be performed. However, select has several limitations, including a maximum limit on the number of file descriptors it can monitor and poor performance when monitoring large numbers of file descriptors.

Poll is a more recent mechanism that is similar to select but has some improvements, including a higher limit on the number of file descriptors it can monitor and better performance when monitoring large numbers of file descriptors. However, like select, poll still suffers from poor performance when monitoring a large number of file descriptors.

Epoll is the newest and most advanced mechanism, introduced in Linux 2.5.44. It uses a scalable event notification mechanism and can handle a large number of file descriptors efficiently. Unlike select and poll, epoll is not limited by the maximum number of file descriptors it can monitor, making it the preferred mechanism for high-performance applications that need to monitor a large number of file descriptors.