AnyEvent::Loop(3pm) User Contributed Perl Documentation AnyEvent::Loop(3pm)
NAME
AnyEvent::Loop - AnyEvent's Pure-Perl event loop
SYNOPSIS
use AnyEvent;
# use AnyEvent::Loop;
# this module gets loaded automatically when no other loop can be found
# Explicit use:
use AnyEvent::Loop;
use AnyEvent;
...
AnyEvent::Loop::run; # run the event loop
DESCRIPTION
This module provides an event loop for AnyEvent in case no other event
loop could be found or loaded. You don't have to do anything to make it
work with AnyEvent except by possibly loading it before creating the
first AnyEvent watcher.
This module is not some loop abstracion used by AnyEvent, but just
another event loop like EV or Glib, just written in pure perl and
delivered with AnyEvent, so AnyEvent always works, even in the absence
of any other backend.
If you want to use this module instead of autoloading a potentially
better event loop you can simply load it (and no other event loops)
before creating the first watcher.
As for performance, this module is on par with (and usually faster
than) most select/poll-based C event modules such as Event or Glib (it
does not even come close to EV, though), with respect to I/O watchers.
Timers are handled less optimally, but for many common tasks, it is
still on par with event loops written in C.
This event loop has been optimised for the following use cases:
monotonic clock is available
This module will use the POSIX monotonic clock option (if it can be
detected at runtime) or the POSIX "times" function (if the
resolution is at least 100Hz), in which case it will not suffer
adversely from time jumps.
If no monotonic clock is available, this module will not attempt to
correct for time jumps in any way.
The clock chosen will be reported if the environment variable
$PERL_ANYEVENT_VERBOSE is set to 8 or higher.
any number of watchers on one fd
Supporting a large number of watchers per fd is purely a dirty
benchmark optimisation not relevant in practise. The more common
case of having one watcher per fd/poll combo is special-cased,
however, and therefore fast, too.
relatively few active fds per "select" call
This module expects that only a tiny amount of fds is active at any
one time. This is relatively typical of larger servers (but not the
case where "select" traditionally is fast), at the expense of the
"dense activity case" where most of the fds are active (which suits
"select").
The optimal implementation of the "dense" case is not much faster,
though, so the module should behave very well in most cases,
subject to the bad scalability of "select" in the presence of a
large number of inactive file descriptors.
lots of timer changes/iteration, or none at all
This module sorts the timer list using perl's "sort", even though a
total ordering is not required for timers internally.
This sorting is expensive, but means sorting can be avoided unless
the timer list has changed in a way that requires a new sort.
This means that adding lots of timers is very efficient, as well as
not changing the timers. Advancing timers (e.g. recreating a
timeout watcher on activity) is also relatively efficient, for
example, if you have a large number of timeout watchers that time
out after 10 seconds, then the timer list will be sorted only once
every 10 seconds.
This should not have much of an impact unless you have hundreds or
thousands of timers, though, or your timers have very small
timeouts.
FUNCTIONS
The only user-visible functions provided by this module loop related -
watchers are created via the normal AnyEvent mechanisms.
AnyEvent::Loop::run
Run the event loop, usually the last thing done in the main program
when you want to use the pure-perl backend.
AnyEvent::Loop::one_event
Blocks until at least one new event has been received by the
operating system, whether or not it was AnyEvent-related.
SEE ALSO
AnyEvent.
AUTHOR
Marc Lehmann <schmorp@schmorp.de>
http://anyevent.schmorp.de
perl v5.36.0 2022-10-20 AnyEvent::Loop(3pm)
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