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.

mask ( IO [, EVENT_MASK ] )

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.

poll ( [ TIMEOUT ] )

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.

events ( IO )

Returns the event mask which represents the events that happend on IO during the last call to poll.

remove ( IO )

Remove IO from the list of file descriptors for the next poll.

handles( [ EVENT_MASK ] )

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.

sigmask

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.

sigmask_add ( SIGNALS )

Adds the given signals to the signal mask. These signals will be blocked during the poll call.

sigmask_del ( SIGNALS )

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.

sigmask_ismember ( SIGNAL )

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.