[ViewVC] Diff of: cvs/AnyEvent/lib/AnyEvent.pm

Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.56 by root, Thu Apr 24 03:10:03 2008 UTC vs.
Revision 1.100 by elmex, Sun Apr 27 19:15:43 2008 UTC

…		…
1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent - provide framework for multiple event loops	3	AnyEvent - provide framework for multiple event loops
4		4
5	EV, Event, Coro::EV, Coro::Event, Glib, Tk, Perl, Event::Lib, Qt - various supported event loops	5	EV, Event, Coro::EV, Coro::Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event loops
6		6
7	=head1 SYNOPSIS	7	=head1 SYNOPSIS
8		8
9	use AnyEvent;	9	use AnyEvent;
10		10
66		66
67	Of course, if you want lots of policy (this can arguably be somewhat	67	Of course, if you want lots of policy (this can arguably be somewhat
68	useful) and you want to force your users to use the one and only event	68	useful) and you want to force your users to use the one and only event
69	model, you should I<not> use this module.	69	model, you should I<not> use this module.
70		70
		71	#TODO#
		72
		73	Net::IRC3
		74	AnyEvent::HTTPD
		75	AnyEvent::DNS
		76	IO::AnyEvent
		77	Net::FPing
		78	Net::XMPP2
		79	Coro
		80
		81	AnyEvent::IRC
		82	AnyEvent::HTTPD
		83	AnyEvent::DNS
		84	AnyEvent::Handle
		85	AnyEvent::Socket
		86	AnyEvent::FPing
		87	AnyEvent::XMPP
		88	AnyEvent::SNMP
		89	Coro
71		90
72	=head1 DESCRIPTION	91	=head1 DESCRIPTION
73		92
74	L<AnyEvent> provides an identical interface to multiple event loops. This	93	L<AnyEvent> provides an identical interface to multiple event loops. This
75	allows module authors to utilise an event loop without forcing module	94	allows module authors to utilise an event loop without forcing module
…		…
80	module.	99	module.
81		100
82	During the first call of any watcher-creation method, the module tries	101	During the first call of any watcher-creation method, the module tries
83	to detect the currently loaded event loop by probing whether one of the	102	to detect the currently loaded event loop by probing whether one of the
84	following modules is already loaded: L<Coro::EV>, L<Coro::Event>, L<EV>,	103	following modules is already loaded: L<Coro::EV>, L<Coro::Event>, L<EV>,
85	L<Event>, L<Glib>, L<Tk>. The first one found is used. If none are found,	104	L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,
86	the module tries to load these modules in the stated order. The first one	105	L<POE>. The first one found is used. If none are found, the module tries
		106	to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl
		107	adaptor should always succeed) in the order given. The first one that can
87	that can be successfully loaded will be used. If, after this, still none	108	be successfully loaded will be used. If, after this, still none could be
88	could be found, AnyEvent will fall back to a pure-perl event loop, which	109	found, AnyEvent will fall back to a pure-perl event loop, which is not
89	is not very efficient, but should work everywhere.	110	very efficient, but should work everywhere.
90		111
91	Because AnyEvent first checks for modules that are already loaded, loading	112	Because AnyEvent first checks for modules that are already loaded, loading
92	an event model explicitly before first using AnyEvent will likely make	113	an event model explicitly before first using AnyEvent will likely make
93	that model the default. For example:	114	that model the default. For example:
94		115
…		…
134		155
135	Note that C<my $w; $w => combination. This is necessary because in Perl,	156	Note that C<my $w; $w => combination. This is necessary because in Perl,
136	my variables are only visible after the statement in which they are	157	my variables are only visible after the statement in which they are
137	declared.	158	declared.
138		159
139	=head2 IO WATCHERS	160	=head2 I/O WATCHERS
140		161
141	You can create an I/O watcher by calling the C<< AnyEvent->io >> method	162	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
142	with the following mandatory key-value pairs as arguments:	163	with the following mandatory key-value pairs as arguments:
143		164
144	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch for	165	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch
145	events. C<poll> must be a string that is either C<r> or C<w>, which	166	for events. C<poll> must be a string that is either C<r> or C<w>,
146	creates a watcher waiting for "r"eadable or "w"ritable events,	167	which creates a watcher waiting for "r"eadable or "w"ritable events,
147	respectively. C<cb> is the callback to invoke each time the file handle	168	respectively. C<cb> is the callback to invoke each time the file handle
148	becomes ready.	169	becomes ready.
149		170
150	As long as the I/O watcher exists it will keep the file descriptor or a	171	Although the callback might get passed parameters, their value and
151	copy of it alive/open.	172	presence is undefined and you cannot rely on them. Portable AnyEvent
		173	callbacks cannot use arguments passed to I/O watcher callbacks.
152		174
		175	The I/O watcher might use the underlying file descriptor or a copy of it.
153	It is not allowed to close a file handle as long as any watcher is active	176	You must not close a file handle as long as any watcher is active on the
154	on the underlying file descriptor.	177	underlying file descriptor.
155		178
156	Some event loops issue spurious readyness notifications, so you should	179	Some event loops issue spurious readyness notifications, so you should
157	always use non-blocking calls when reading/writing from/to your file	180	always use non-blocking calls when reading/writing from/to your file
158	handles.	181	handles.
159		182
…		…
170		193
171	You can create a time watcher by calling the C<< AnyEvent->timer >>	194	You can create a time watcher by calling the C<< AnyEvent->timer >>
172	method with the following mandatory arguments:	195	method with the following mandatory arguments:
173		196
174	C<after> specifies after how many seconds (fractional values are	197	C<after> specifies after how many seconds (fractional values are
175	supported) should the timer activate. C<cb> the callback to invoke in that	198	supported) the callback should be invoked. C<cb> is the callback to invoke
176	case.	199	in that case.
		200
		201	Although the callback might get passed parameters, their value and
		202	presence is undefined and you cannot rely on them. Portable AnyEvent
		203	callbacks cannot use arguments passed to time watcher callbacks.
177		204
178	The timer callback will be invoked at most once: if you want a repeating	205	The timer callback will be invoked at most once: if you want a repeating
179	timer you have to create a new watcher (this is a limitation by both Tk	206	timer you have to create a new watcher (this is a limitation by both Tk
180	and Glib).	207	and Glib).
181		208
…		…
206		233
207	There are two ways to handle timers: based on real time (relative, "fire	234	There are two ways to handle timers: based on real time (relative, "fire
208	in 10 seconds") and based on wallclock time (absolute, "fire at 12	235	in 10 seconds") and based on wallclock time (absolute, "fire at 12
209	o'clock").	236	o'clock").
210		237
211	While most event loops expect timers to specified in a relative way, they use	238	While most event loops expect timers to specified in a relative way, they
212	absolute time internally. This makes a difference when your clock "jumps",	239	use absolute time internally. This makes a difference when your clock
213	for example, when ntp decides to set your clock backwards from the wrong 2014-01-01 to	240	"jumps", for example, when ntp decides to set your clock backwards from
214	2008-01-01, a watcher that you created to fire "after" a second might actually take	241	the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to
215	six years to finally fire.	242	fire "after" a second might actually take six years to finally fire.
216		243
217	AnyEvent cannot compensate for this. The only event loop that is conscious	244	AnyEvent cannot compensate for this. The only event loop that is conscious
218	about these issues is L<EV>, which offers both relative (ev_timer) and	245	about these issues is L<EV>, which offers both relative (ev_timer, based
219	absolute (ev_periodic) timers.	246	on true relative time) and absolute (ev_periodic, based on wallclock time)
		247	timers.
220		248
221	AnyEvent always prefers relative timers, if available, matching the	249	AnyEvent always prefers relative timers, if available, matching the
222	AnyEvent API.	250	AnyEvent API.
223		251
224	=head2 SIGNAL WATCHERS	252	=head2 SIGNAL WATCHERS
225		253
226	You can watch for signals using a signal watcher, C<signal> is the signal	254	You can watch for signals using a signal watcher, C<signal> is the signal
227	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to	255	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to
228	be invoked whenever a signal occurs.	256	be invoked whenever a signal occurs.
229		257
		258	Although the callback might get passed parameters, their value and
		259	presence is undefined and you cannot rely on them. Portable AnyEvent
		260	callbacks cannot use arguments passed to signal watcher callbacks.
		261
230	Multiple signals occurances can be clumped together into one callback	262	Multiple signal occurances can be clumped together into one callback
231	invocation, and callback invocation will be synchronous. synchronous means	263	invocation, and callback invocation will be synchronous. synchronous means
232	that it might take a while until the signal gets handled by the process,	264	that it might take a while until the signal gets handled by the process,
233	but it is guarenteed not to interrupt any other callbacks.	265	but it is guarenteed not to interrupt any other callbacks.
234		266
235	The main advantage of using these watchers is that you can share a signal	267	The main advantage of using these watchers is that you can share a signal
…		…
248		280
249	The child process is specified by the C<pid> argument (if set to C<0>, it	281	The child process is specified by the C<pid> argument (if set to C<0>, it
250	watches for any child process exit). The watcher will trigger as often	282	watches for any child process exit). The watcher will trigger as often
251	as status change for the child are received. This works by installing a	283	as status change for the child are received. This works by installing a
252	signal handler for C<SIGCHLD>. The callback will be called with the pid	284	signal handler for C<SIGCHLD>. The callback will be called with the pid
253	and exit status (as returned by waitpid).	285	and exit status (as returned by waitpid), so unlike other watcher types,
		286	you I<can> rely on child watcher callback arguments.
254		287
255	Example: wait for pid 1333	288	There is a slight catch to child watchers, however: you usually start them
		289	I<after> the child process was created, and this means the process could
		290	have exited already (and no SIGCHLD will be sent anymore).
		291
		292	Not all event models handle this correctly (POE doesn't), but even for
		293	event models that I<do> handle this correctly, they usually need to be
		294	loaded before the process exits (i.e. before you fork in the first place).
		295
		296	This means you cannot create a child watcher as the very first thing in an
		297	AnyEvent program, you I<have> to create at least one watcher before you
		298	C<fork> the child (alternatively, you can call C<AnyEvent::detect>).
		299
		300	Example: fork a process and wait for it
		301
		302	my $done = AnyEvent->condvar;
		303
		304	AnyEvent::detect; # force event module to be initialised
		305
		306	my $pid = fork or exit 5;
256		307
257	my $w = AnyEvent->child (	308	my $w = AnyEvent->child (
258	pid => 1333,	309	pid => $pid,
259	cb => sub {	310	cb => sub {
260	my ($pid, $status) = @_;	311	my ($pid, $status) = @_;
261	warn "pid $pid exited with status $status";	312	warn "pid $pid exited with status $status";
		313	$done->broadcast;
262	},	314	},
263	);	315	);
		316
		317	# do something else, then wait for process exit
		318	$done->wait;
264		319
265	=head2 CONDITION VARIABLES	320	=head2 CONDITION VARIABLES
266		321
267	Condition variables can be created by calling the C<< AnyEvent->condvar >>	322	Condition variables can be created by calling the C<< AnyEvent->condvar >>
268	method without any arguments.	323	method without any arguments.
…		…
356	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.	411	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
357	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.	412	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
358	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).	413	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
359	AnyEvent::Impl::Event based on Event, second best choice.	414	AnyEvent::Impl::Event based on Event, second best choice.
360	AnyEvent::Impl::Glib based on Glib, third-best choice.	415	AnyEvent::Impl::Glib based on Glib, third-best choice.
		416	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
361	AnyEvent::Impl::Tk based on Tk, very bad choice.	417	AnyEvent::Impl::Tk based on Tk, very bad choice.
362	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
363	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).	418	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
364	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.	419	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		420	AnyEvent::Impl::POE based on POE, not generic enough for full support.
		421
		422	There is no support for WxWidgets, as WxWidgets has no support for
		423	watching file handles. However, you can use WxWidgets through the
		424	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
		425	second, which was considered to be too horrible to even consider for
		426	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
		427	it's adaptor.
		428
		429	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
		430	autodetecting them.
365		431
366	=item AnyEvent::detect	432	=item AnyEvent::detect
367		433
368	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	434	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
369	if necessary. You should only call this function right before you would	435	if necessary. You should only call this function right before you would
…		…
411		477
412	You can chose to use a rather inefficient pure-perl implementation by	478	You can chose to use a rather inefficient pure-perl implementation by
413	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	479	loading the C<AnyEvent::Impl::Perl> module, which gives you similar
414	behaviour everywhere, but letting AnyEvent chose is generally better.	480	behaviour everywhere, but letting AnyEvent chose is generally better.
415		481
		482	=head1 OTHER MODULES
		483
		484	L<AnyEvent> itself comes with useful utility modules:
		485
		486	To make it easier to do non-blocking IO the modules L<AnyEvent::Handle>
		487	and L<AnyEvent::Socket> are provided. L<AnyEvent::Handle> provides
		488	read and write buffers and manages watchers for reads and writes.
		489	L<AnyEvent::Socket> provides means to do non-blocking connects.
		490
		491	Aside from those there are these modules that support AnyEvent (and use it
		492	for non-blocking IO):
		493
		494	=over 4
		495
		496	=item L<AnyEvent::FastPing>
		497
		498	=item L<Net::IRC3>
		499
		500	=item L<Net::XMPP2>
		501
		502	=back
		503
416	=cut	504	=cut
417		505
418	package AnyEvent;	506	package AnyEvent;
419		507
420	no warnings;	508	no warnings;
421	use strict;	509	use strict;
422		510
423	use Carp;	511	use Carp;
424		512
425	our $VERSION = '3.12';	513	our $VERSION = '3.3';
426	our $MODEL;	514	our $MODEL;
427		515
428	our $AUTOLOAD;	516	our $AUTOLOAD;
429	our @ISA;	517	our @ISA;
430		518
…		…
437	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],	525	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
438	[EV:: => AnyEvent::Impl::EV::],	526	[EV:: => AnyEvent::Impl::EV::],
439	[Event:: => AnyEvent::Impl::Event::],	527	[Event:: => AnyEvent::Impl::Event::],
440	[Glib:: => AnyEvent::Impl::Glib::],	528	[Glib:: => AnyEvent::Impl::Glib::],
441	[Tk:: => AnyEvent::Impl::Tk::],	529	[Tk:: => AnyEvent::Impl::Tk::],
		530	[Wx:: => AnyEvent::Impl::POE::],
		531	[Prima:: => AnyEvent::Impl::POE::],
442	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	532	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
443	);	533	# everything below here will not be autoprobed as the pureperl backend should work everywhere
444	my @models_detect = (	534	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
445	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program	535	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
446	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy	536	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
447	);	537	);
448		538
449	our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);	539	our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);
450		540
451	sub detect() {	541	sub detect() {
…		…
455	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	545	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
456	my $model = "AnyEvent::Impl::$1";	546	my $model = "AnyEvent::Impl::$1";
457	if (eval "require $model") {	547	if (eval "require $model") {
458	$MODEL = $model;	548	$MODEL = $model;
459	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;	549	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;
		550	} else {
		551	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;
460	}	552	}
461	}	553	}
462		554
463	# check for already loaded models	555	# check for already loaded models
464	unless ($MODEL) {	556	unless ($MODEL) {
465	for (@REGISTRY, @models, @models_detect) {	557	for (@REGISTRY, @models) {
466	my ($package, $model) = @$_;	558	my ($package, $model) = @$_;
467	if (${"$package\::VERSION"} > 0) {	559	if (${"$package\::VERSION"} > 0) {
468	if (eval "require $model") {	560	if (eval "require $model") {
469	$MODEL = $model;	561	$MODEL = $model;
470	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;	562	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;
…		…
657		749
658	=over 4	750	=over 4
659		751
660	=item C<PERL_ANYEVENT_VERBOSE>	752	=item C<PERL_ANYEVENT_VERBOSE>
661		753
		754	By default, AnyEvent will be completely silent except in fatal
		755	conditions. You can set this environment variable to make AnyEvent more
		756	talkative.
		757
		758	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		759	conditions, such as not being able to load the event model specified by
		760	C<PERL_ANYEVENT_MODEL>.
		761
662	When set to C<2> or higher, cause AnyEvent to report to STDERR which event	762	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
663	model it chooses.	763	model it chooses.
664		764
665	=item C<PERL_ANYEVENT_MODEL>	765	=item C<PERL_ANYEVENT_MODEL>
666		766
…		…
680		780
681	=back	781	=back
682		782
683	=head1 EXAMPLE PROGRAM	783	=head1 EXAMPLE PROGRAM
684		784
685	The following program uses an IO watcher to read data from STDIN, a timer	785	The following program uses an I/O watcher to read data from STDIN, a timer
686	to display a message once per second, and a condition variable to quit the	786	to display a message once per second, and a condition variable to quit the
687	program when the user enters quit:	787	program when the user enters quit:
688		788
689	use AnyEvent;	789	use AnyEvent;
690		790
…		…
834	$quit->broadcast;	934	$quit->broadcast;
835	});	935	});
836		936
837	$quit->wait;	937	$quit->wait;
838		938
		939
		940	=head1 BENCHMARKS
		941
		942	To give you an idea of the performance and overheads that AnyEvent adds
		943	over the event loops themselves and to give you an impression of the speed
		944	of various event loops I prepared some benchmarks.
		945
		946	=head2 BENCHMARKING ANYEVENT OVERHEAD
		947
		948	Here is a benchmark of various supported event models used natively and
		949	through anyevent. The benchmark creates a lot of timers (with a zero
		950	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
		951	which it is), lets them fire exactly once and destroys them again.
		952
		953	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
		954	distribution.
		955
		956	=head3 Explanation of the columns
		957
		958	I<watcher> is the number of event watchers created/destroyed. Since
		959	different event models feature vastly different performances, each event
		960	loop was given a number of watchers so that overall runtime is acceptable
		961	and similar between tested event loop (and keep them from crashing): Glib
		962	would probably take thousands of years if asked to process the same number
		963	of watchers as EV in this benchmark.
		964
		965	I<bytes> is the number of bytes (as measured by the resident set size,
		966	RSS) consumed by each watcher. This method of measuring captures both C
		967	and Perl-based overheads.
		968
		969	I<create> is the time, in microseconds (millionths of seconds), that it
		970	takes to create a single watcher. The callback is a closure shared between
		971	all watchers, to avoid adding memory overhead. That means closure creation
		972	and memory usage is not included in the figures.
		973
		974	I<invoke> is the time, in microseconds, used to invoke a simple
		975	callback. The callback simply counts down a Perl variable and after it was
		976	invoked "watcher" times, it would C<< ->broadcast >> a condvar once to
		977	signal the end of this phase.
		978
		979	I<destroy> is the time, in microseconds, that it takes to destroy a single
		980	watcher.
		981
		982	=head3 Results
		983
		984	name watchers bytes create invoke destroy comment
		985	EV/EV 400000 244 0.56 0.46 0.31 EV native interface
		986	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers
		987	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal
		988	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation
		989	Event/Event 16000 516 31.88 31.30 0.85 Event native interface
		990	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers
		991	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour
		992	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers
		993	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event
		994	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select
		995
		996	=head3 Discussion
		997
		998	The benchmark does I<not> measure scalability of the event loop very
		999	well. For example, a select-based event loop (such as the pure perl one)
		1000	can never compete with an event loop that uses epoll when the number of
		1001	file descriptors grows high. In this benchmark, all events become ready at
		1002	the same time, so select/poll-based implementations get an unnatural speed
		1003	boost.
		1004
		1005	Also, note that the number of watchers usually has a nonlinear effect on
		1006	overall speed, that is, creating twice as many watchers doesn't take twice
		1007	the time - usually it takes longer. This puts event loops tested with a
		1008	higher number of watchers at a disadvantage.
		1009
		1010	To put the range of results into perspective, consider that on the
		1011	benchmark machine, handling an event takes roughly 1600 CPU cycles with
		1012	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
		1013	cycles with POE.
		1014
		1015	C<EV> is the sole leader regarding speed and memory use, which are both
		1016	maximal/minimal, respectively. Even when going through AnyEvent, it uses
		1017	far less memory than any other event loop and is still faster than Event
		1018	natively.
		1019
		1020	The pure perl implementation is hit in a few sweet spots (both the
		1021	constant timeout and the use of a single fd hit optimisations in the perl
		1022	interpreter and the backend itself). Nevertheless this shows that it
		1023	adds very little overhead in itself. Like any select-based backend its
		1024	performance becomes really bad with lots of file descriptors (and few of
		1025	them active), of course, but this was not subject of this benchmark.
		1026
		1027	The C<Event> module has a relatively high setup and callback invocation
		1028	cost, but overall scores in on the third place.
		1029
		1030	C<Glib>'s memory usage is quite a bit higher, but it features a
		1031	faster callback invocation and overall ends up in the same class as
		1032	C<Event>. However, Glib scales extremely badly, doubling the number of
		1033	watchers increases the processing time by more than a factor of four,
		1034	making it completely unusable when using larger numbers of watchers
		1035	(note that only a single file descriptor was used in the benchmark, so
		1036	inefficiencies of C<poll> do not account for this).
		1037
		1038	The C<Tk> adaptor works relatively well. The fact that it crashes with
		1039	more than 2000 watchers is a big setback, however, as correctness takes
		1040	precedence over speed. Nevertheless, its performance is surprising, as the
		1041	file descriptor is dup()ed for each watcher. This shows that the dup()
		1042	employed by some adaptors is not a big performance issue (it does incur a
		1043	hidden memory cost inside the kernel which is not reflected in the figures
		1044	above).
		1045
		1046	C<POE>, regardless of underlying event loop (whether using its pure
		1047	perl select-based backend or the Event module, the POE-EV backend
		1048	couldn't be tested because it wasn't working) shows abysmal performance
		1049	and memory usage: Watchers use almost 30 times as much memory as
		1050	EV watchers, and 10 times as much memory as Event (the high memory
		1051	requirements are caused by requiring a session for each watcher). Watcher
		1052	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		1053	implementation. The design of the POE adaptor class in AnyEvent can not
		1054	really account for this, as session creation overhead is small compared
		1055	to execution of the state machine, which is coded pretty optimally within
		1056	L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow.
		1057
		1058	=head3 Summary
		1059
		1060	=over 4
		1061
		1062	=item * Using EV through AnyEvent is faster than any other event loop
		1063	(even when used without AnyEvent), but most event loops have acceptable
		1064	performance with or without AnyEvent.
		1065
		1066	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
		1067	the actual event loop, only with extremely fast event loops such as EV
		1068	adds AnyEvent significant overhead.
		1069
		1070	=item * You should avoid POE like the plague if you want performance or
		1071	reasonable memory usage.
		1072
		1073	=back
		1074
		1075	=head2 BENCHMARKING THE LARGE SERVER CASE
		1076
		1077	This benchmark atcually benchmarks the event loop itself. It works by
		1078	creating a number of "servers": each server consists of a socketpair, a
		1079	timeout watcher that gets reset on activity (but never fires), and an I/O
		1080	watcher waiting for input on one side of the socket. Each time the socket
		1081	watcher reads a byte it will write that byte to a random other "server".
		1082
		1083	The effect is that there will be a lot of I/O watchers, only part of which
		1084	are active at any one point (so there is a constant number of active
		1085	fds for each loop iterstaion, but which fds these are is random). The
		1086	timeout is reset each time something is read because that reflects how
		1087	most timeouts work (and puts extra pressure on the event loops).
		1088
		1089	In this benchmark, we use 10000 socketpairs (20000 sockets), of which 100
		1090	(1%) are active. This mirrors the activity of large servers with many
		1091	connections, most of which are idle at any one point in time.
		1092
		1093	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
		1094	distribution.
		1095
		1096	=head3 Explanation of the columns
		1097
		1098	I<sockets> is the number of sockets, and twice the number of "servers" (as
		1099	each server has a read and write socket end).
		1100
		1101	I<create> is the time it takes to create a socketpair (which is
		1102	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
		1103
		1104	I<request>, the most important value, is the time it takes to handle a
		1105	single "request", that is, reading the token from the pipe and forwarding
		1106	it to another server. This includes deleting the old timeout and creating
		1107	a new one that moves the timeout into the future.
		1108
		1109	=head3 Results
		1110
		1111	name sockets create request
		1112	EV 20000 69.01 11.16
		1113	Perl 20000 73.32 35.87
		1114	Event 20000 212.62 257.32
		1115	Glib 20000 651.16 1896.30
		1116	POE 20000 349.67 12317.24 uses POE::Loop::Event
		1117
		1118	=head3 Discussion
		1119
		1120	This benchmark I<does> measure scalability and overall performance of the
		1121	particular event loop.
		1122
		1123	EV is again fastest. Since it is using epoll on my system, the setup time
		1124	is relatively high, though.
		1125
		1126	Perl surprisingly comes second. It is much faster than the C-based event
		1127	loops Event and Glib.
		1128
		1129	Event suffers from high setup time as well (look at its code and you will
		1130	understand why). Callback invocation also has a high overhead compared to
		1131	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
		1132	uses select or poll in basically all documented configurations.
		1133
		1134	Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It
		1135	clearly fails to perform with many filehandles or in busy servers.
		1136
		1137	POE is still completely out of the picture, taking over 1000 times as long
		1138	as EV, and over 100 times as long as the Perl implementation, even though
		1139	it uses a C-based event loop in this case.
		1140
		1141	=head3 Summary
		1142
		1143	=over 4
		1144
		1145	=item * The pure perl implementation performs extremely well, considering
		1146	that it uses select.
		1147
		1148	=item * Avoid Glib or POE in large projects where performance matters.
		1149
		1150	=back
		1151
		1152	=head2 BENCHMARKING SMALL SERVERS
		1153
		1154	While event loops should scale (and select-based ones do not...) even to
		1155	large servers, most programs we (or I :) actually write have only a few
		1156	I/O watchers.
		1157
		1158	In this benchmark, I use the same benchmark program as in the large server
		1159	case, but it uses only eight "servers", of which three are active at any
		1160	one time. This should reflect performance for a small server relatively
		1161	well.
		1162
		1163	The columns are identical to the previous table.
		1164
		1165	=head3 Results
		1166
		1167	name sockets create request
		1168	EV 16 20.00 6.54
		1169	Perl 16 25.75 12.62
		1170	Event 16 81.27 35.86
		1171	Glib 16 32.63 15.48
		1172	POE 16 261.87 276.28 uses POE::Loop::Event
		1173
		1174	=head3 Discussion
		1175
		1176	The benchmark tries to test the performance of a typical small
		1177	server. While knowing how various event loops perform is interesting, keep
		1178	in mind that their overhead in this case is usually not as important, due
		1179	to the small absolute number of watchers (that is, you need efficiency and
		1180	speed most when you have lots of watchers, not when you only have a few of
		1181	them).
		1182
		1183	EV is again fastest.
		1184
		1185	The C-based event loops Event and Glib come in second this time, as the
		1186	overhead of running an iteration is much smaller in C than in Perl (little
		1187	code to execute in the inner loop, and perl's function calling overhead is
		1188	high, and updating all the data structures is costly).
		1189
		1190	The pure perl event loop is much slower, but still competitive.
		1191
		1192	POE also performs much better in this case, but is is still far behind the
		1193	others.
		1194
		1195	=head3 Summary
		1196
		1197	=over 4
		1198
		1199	=item * C-based event loops perform very well with small number of
		1200	watchers, as the management overhead dominates.
		1201
		1202	=back
		1203
		1204
839	=head1 FORK	1205	=head1 FORK
840		1206
841	Most event libraries are not fork-safe. The ones who are usually are	1207	Most event libraries are not fork-safe. The ones who are usually are
842	because they are so inefficient. Only L<EV> is fully fork-aware.	1208	because they are so inefficient. Only L<EV> is fully fork-aware.
843		1209
844	If you have to fork, you must either do so I<before> creating your first	1210	If you have to fork, you must either do so I<before> creating your first
845	watcher OR you must not use AnyEvent at all in the child.	1211	watcher OR you must not use AnyEvent at all in the child.
		1212
846		1213
847	=head1 SECURITY CONSIDERATIONS	1214	=head1 SECURITY CONSIDERATIONS
848		1215
849	AnyEvent can be forced to load any event model via	1216	AnyEvent can be forced to load any event model via
850	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to	1217	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
…		…
858		1225
859	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	1226	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
860		1227
861	use AnyEvent;	1228	use AnyEvent;
862		1229
		1230
863	=head1 SEE ALSO	1231	=head1 SEE ALSO
864		1232
865	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	1233	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,
866	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,	1234	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,
867	L<Event::Lib>, L<Qt>.	1235	L<Event::Lib>, L<Qt>, L<POE>.
868		1236
869	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	1237	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,
870	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,	1238	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,
871	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,	1239	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,
872	L<AnyEvent::Impl::Qt>.	1240	L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.
873		1241
874	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	1242	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.
		1243
875		1244
876	=head1 AUTHOR	1245	=head1 AUTHOR
877		1246
878	Marc Lehmann <schmorp@schmorp.de>	1247	Marc Lehmann <schmorp@schmorp.de>
879	http://home.schmorp.de/	1248	http://home.schmorp.de/

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Comparing AnyEvent/lib/AnyEvent.pm (file contents): Revision 1.56 by root, Thu Apr 24 03:10:03 2008 UTC vs. Revision 1.100 by elmex, Sun Apr 27 19:15:43 2008 UTC

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Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.56 by root, Thu Apr 24 03:10:03 2008 UTC vs.
Revision 1.100 by elmex, Sun Apr 27 19:15:43 2008 UTC