NAME

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

SYNOPSIS

# 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);

DESCRIPTION

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 three system calls: epoll_create(2), epoll_ctl(2) and epoll_wait(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.

LOW-LEVEL API

epoll_create

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.

epoll_ctl

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.

epoll_wait

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.

HIGH LEVEL API

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.

METHODS

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.

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

Exportable constants

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

SEE ALSO

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

AUTHOR

Bruce J Keeler, <bruce@gridpoint.com>

CREDITS

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

COPYRIGHT AND LICENSE

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.

cpanm IO::Epoll

perl -MCPAN -e shell
install IO::Epoll