IO::Epoll(3pm) User Contributed Perl Documentation IO::Epoll(3pm)

IO::Epoll - Scalable IO Multiplexing for Linux 2.5.44 and higher

    # Low level interface
    use IO::Epoll;
    $epfd = epoll_create(10);
    epoll_ctl($epfd, EPOLL_CTL_ADD, fileno STDIN, EPOLLIN) >= 0
        || die "epoll_ctl: $!\n";
    epoll_ctl($epfd, ...);
    $events = epoll_wait($epfd, 10, 1000); # Max 10 events returned, 1s timeout
    # High level IO::Poll emulation layer
    use IO::EPoll qw(:compat);
    $poll = new IO::Epoll;
    $poll->mask($input_handle => POLLIN);
    $poll->mask($output_handle => POLLOUT);
    $poll->poll($timeout);
    $ev = $poll->events($input);

The epoll(4) subsystem is a new, (currently) Linux-specific variant of poll(2). It is designed to offer O(1) scalability over large numbers of watched file descriptors. You will need at least version 2.5.44 of Linux to use this module, and you might need to upgrade your C library.

The epoll(2) API comprises four system calls: epoll_create(2), epoll_ctl(2), epoll_wait(2) and epoll_pwait(2). "IO::Epoll" provides a low-level API which closely matches the underlying system calls. It also provides a higher-level layer designed to emulate the behavior of "IO::Poll" and "IO::Ppoll".

Create a new "epoll" file descriptor by requesting the kernel allocate an event backing store dimensioned for "size" descriptors. The size is not the maximum size of the backing store but just a hint to the kernel about how to dimension internal structures. The returned file descriptor will be used for all the subsequent calls to the "epoll" interface. The file descriptor returned by "epoll_create" must be closed by using "POSIX::close".

    $epfd = epoll_create(15);
    ...
    POSIX::close($epfd);

When successful, "epoll_create" returns a positive integer identifying the descriptor. When an error occurs, "epoll_create" returns -1 and errno is set appropriately.

Control an "epoll" descriptor, $epfd, by requesting the operation op be performed on the target file descriptor, fd.

  $ret = epoll_ctl($epfd, $op, $fd, $eventmask)

$epfd is an "epoll" descriptor returned from "epoll_create".

$op is one of "EPOLL_CTL_ADD", "EPOLL_CTL_MOD" or "EPOLL_CTL_DEL".

$fd is the file desciptor to be watched.

$eventmask is a bitmask of events defined by "EPOLLIN", "EPOLLOUT", etc.

When successful, "epoll_ctl" returns 0. When an error occurs, "epoll_ctl" returns -1 and errno is set appropriately.

Wait for events on the "epoll" file descriptor $epfd.

  $ret = epoll_wait($epfd, $maxevents, $timeout)

$epfd is an "epoll" descriptor returned from "epoll_create".

$maxevents is an integer specifying the maximum number of events to be returned.

$timeout is a timeout, in milliseconds

When successful, "epoll_wait" returns a reference to an array of events. Each event is a two element array, the first element being the file descriptor which triggered the event, and the second is the mask of event types triggered. For example, if "epoll_wait" returned the following data structure:

    [
      [ 0, EPOLLIN ],
      [ 6, EPOLLOUT | EPOLLIN ]
    ]

then file descriptor 0 would be ready for reading, and fd 4 would be ready for both reading and writing.

On error, "epoll_wait" returns undef and sets "errno" appropriately.

Wait for events on the "epoll" file descriptor $epfd.

  $ret = epoll_pwait($epfd, $maxevents, $timeout, $sigmask)

Identical to "epoll_wait", except that the kernel will atomically swap the current signal mask for the process to that supplied in $sigmask, wait for events, then restore it to what it was originally. The $sigmask parameter should be undef, or an instance of "POSIX::SigSet".

IO::Epoll provides an object oriented API designed to be a drop-in replacement for IO::Poll. See the documentation for that module for more information.

If EVENT_MASK is given, then, if EVENT_MASK is non-zero, IO is added to the list of file descriptors and the next call to poll will check for any event specified in EVENT_MASK. If EVENT_MASK is zero then IO will be removed from the list of file descriptors.

If EVENT_MASK is not given then the return value will be the current event mask value for IO.

Call the system level poll routine. If TIMEOUT is not specified then the call will block. Returns the number of handles which had events happen, or -1 on error. TIMEOUT is in seconds and may be fractional.
Returns the event mask which represents the events that happend on IO during the last call to "poll".
Remove IO from the list of file descriptors for the next poll.
Returns a list of handles. If EVENT_MASK is not given then a list of all handles known will be returned. If EVENT_MASK is given then a list of handles will be returned which had one of the events specified by EVENT_MASK happen during the last call ti "poll"

IO::Epoll also provides methods compatible with IO::Ppoll. When any of these methods are called, the IO::Epoll object switches up to IO::Ppoll-compatible mode, and will use the epoll_pwait(2) system call when the "poll" method is invoked.

Returns the "POSIX::SigSet" object in which the signal mask is stored. Since this is a reference to the object used in the call to epoll_pwait(2), any modifications made to it will be reflected in the signal mask given to the system call.
Adds the given signals to the signal mask. These signals will be blocked during the "poll" call.
Removes the given signals from the signal mask. These signals will not be blocked during the "poll" call, and may be delivered while "poll" is waiting.
Tests if the given signal is present in the signal mask.

Exported by default:

  EPOLLERR
  EPOLLET
  EPOLLHUP
  EPOLLIN
  EPOLLMSG
  EPOLLOUT
  EPOLLPRI
  EPOLLRDBAND
  EPOLLRDNORM
  EPOLLWRBAND
  EPOLLWRNORM
  EPOLL_CTL_ADD
  EPOLL_CTL_DEL
  EPOLL_CTL_MOD

Exported by the :compat tag:

  POLLNVAL
  POLLIN
  POLLOUT
  POLLERR
  POLLHUP
  POLLPRI
  POLLRDNORM
  POLLWRNORM
  POLLRDBAND
  POLLWRBAND

"IO::Poll" "IO::Select" "IO::Ppoll" epoll(4) epoll_create(2) epoll_ctl(2) epoll_wait(2) epoll_pwait(2)

Bruce J Keeler, <bruce@gridpoint.com>

The "IO::Poll" compatibility code borrows heavily from the "IO::Poll" code itself, which was written by Graham Barr.

Copyright (C) 2004 by Bruce J. Keeler Portions Copyright (C) 1997-8 Graham Barr <gbarr@pobox.com>

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

2024-03-31 perl v5.38.2