How does epoll work?
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How does epoll work?
epoll stands for event poll and is a Linux specific construct. It allows for a process to monitor multiple file descriptors and get notifications when I/O is possible on them. It allows for both edge-triggered as well as level-triggered notifications.
What is epoll in socket programming?
The epoll API performs a similar task to poll(2): monitoring multiple file descriptors to see if I/O is possible on any of them. The epoll API can be used either as an edge-triggered or a level-triggered interface and scales well to large numbers of watched file descriptors.
What is an epoll file descriptor?
From Wikipedia, the free encyclopedia. epoll is a Linux kernel system call for a scalable I/O event notification mechanism, first introduced in version 2.5. 44 of the Linux kernel. Its function is to monitor multiple file descriptors to see whether I/O is possible on any of them.
How does Linux select work?
select() works by blocking until something happens on a file descriptor (aka a socket). What’s ‘something’? Data coming in or being able to write to a file descriptor — you tell select() what you want to be woken up by. You fill up a fd_set structure with some macros.
Why is epoll faster?
By being entirely event-based and by using a long-lasting set of fd’s and a ready list, epoll can avoid ever taking O(n) time for an operation, where n is the number of file descriptors being monitored.
How do you use epoll?
- Step 1: Create epoll file descriptor. First I’ll go through the process of just creating and closing an epoll instance.
- Step 2: Add file descriptors for epoll to watch. The next thing to do is tell epoll what file descriptors to watch and what kinds of events to watch for.
- Step 3: Profit. That’s right!
What is the difference between polling and selecting?
select() only uses (at maximum) three bits of data per file descriptor, while poll() typically uses 64 bits per file descriptor. In each syscall invoke poll() thus needs to copy a lot more over to kernel space. A small win for select().