¿Cómo funciona kcola?

How does kqueue work?

Kqueue provides efficient input and output event pipelines between the kernel and userland. Thus, it is possible to modify event filters as well as receive pending events while using only a single system call to kevent(2) per main event loop iteration.

The kevent() system call is used to register events with the queue, and return any pending events to the user. The changelist argument is a pointer to an array of kevent structures, as defined in . All changes contained in the changelist are applied before any pending events are read from the queue.

The Proposed Linux kevent API. The proposed Linux kevent API is a new unified event handling interface, similar in spirit to completion ports and the FreeBSD/ OS X kqueue interface.

Kqueue allows one to batch modify watcher states and to retrieve watcher states in a single system call. With epoll, you have to call a system call for every modification. Kqueue also allows one to watch for things like filesystem changes and process state changes, epoll is limited to socket/pipe I/O only.

1 Answer

1. Create an epoll instance with epoll_create(2) or the more recent variant epoll_create1(2) .
2. Register interest in file descriptors with epoll_ctl(2) .
3. Call epoll_wait(2) to wait for an I/O event, possibly blocking the calling thread until some event is available.

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.

I/O multiplexing means what it says – allowing the programmer to examine and block on multiple I/O streams (or other “synchronizing” events), being notified whenever any one of the streams is active so that it can process data on that stream.

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.

The Go network stack already makes use of epoll and kqueue: https://golang.org/s… | Hacker News.

performance: select & poll vs epoll So using epoll really is a lot faster once you have more than 10 or so file descriptors to monitor.

Multiplexing essentially means reading from or writing to multiple file descriptors simultaneously. The FD_ZERO() macro clears the specified set, and should be used every time before calling select(). The FD_SET() macro adds a file descriptor to a given set.