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

Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.55 by root, Wed Apr 23 11:25:42 2008 UTC vs.
Revision 1.98 by root, Sun Apr 27 16:31:48 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 - 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	File handles will be kept alive, so as long as the watcher exists, the	171	Although the callback might get passed parameters, their value and
151	file handle exists, too.	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.
…		…
353		408
354	The known classes so far are:	409	The known classes so far are:
355		410
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, also best choice).	413	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
359	AnyEvent::Impl::Event based on Event, also 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.	418	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
363	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.
364		431
365	=item AnyEvent::detect	432	=item AnyEvent::detect
366		433
367	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	434	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
368	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
…		…
419	no warnings;	486	no warnings;
420	use strict;	487	use strict;
421		488
422	use Carp;	489	use Carp;
423		490
424	our $VERSION = '3.12';	491	our $VERSION = '3.3';
425	our $MODEL;	492	our $MODEL;
426		493
427	our $AUTOLOAD;	494	our $AUTOLOAD;
428	our @ISA;	495	our @ISA;
429		496
…		…
436	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],	503	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
437	[EV:: => AnyEvent::Impl::EV::],	504	[EV:: => AnyEvent::Impl::EV::],
438	[Event:: => AnyEvent::Impl::Event::],	505	[Event:: => AnyEvent::Impl::Event::],
439	[Glib:: => AnyEvent::Impl::Glib::],	506	[Glib:: => AnyEvent::Impl::Glib::],
440	[Tk:: => AnyEvent::Impl::Tk::],	507	[Tk:: => AnyEvent::Impl::Tk::],
		508	[Wx:: => AnyEvent::Impl::POE::],
		509	[Prima:: => AnyEvent::Impl::POE::],
441	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	510	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
		511	# everything below here will not be autoprobed as the pureperl backend should work everywhere
442	[Event::Lib:: => AnyEvent::Impl::EventLib::],	512	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		513	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		514	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
443	);	515	);
444		516
445	our %method = map +($_ => 1), qw(io timer condvar broadcast wait signal one_event DESTROY);	517	our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);
446		518
447	sub detect() {	519	sub detect() {
448	unless ($MODEL) {	520	unless ($MODEL) {
449	no strict 'refs';	521	no strict 'refs';
450		522
451	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	523	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
452	my $model = "AnyEvent::Impl::$1";	524	my $model = "AnyEvent::Impl::$1";
453	if (eval "require $model") {	525	if (eval "require $model") {
454	$MODEL = $model;	526	$MODEL = $model;
455	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;	527	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;
		528	} else {
		529	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;
456	}	530	}
457	}	531	}
458		532
459	# check for already loaded models	533	# check for already loaded models
460	unless ($MODEL) {	534	unless ($MODEL) {
…		…
653		727
654	=over 4	728	=over 4
655		729
656	=item C<PERL_ANYEVENT_VERBOSE>	730	=item C<PERL_ANYEVENT_VERBOSE>
657		731
		732	By default, AnyEvent will be completely silent except in fatal
		733	conditions. You can set this environment variable to make AnyEvent more
		734	talkative.
		735
		736	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		737	conditions, such as not being able to load the event model specified by
		738	C<PERL_ANYEVENT_MODEL>.
		739
658	When set to C<2> or higher, cause AnyEvent to report to STDERR which event	740	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
659	model it chooses.	741	model it chooses.
660		742
661	=item C<PERL_ANYEVENT_MODEL>	743	=item C<PERL_ANYEVENT_MODEL>
662		744
…		…
676		758
677	=back	759	=back
678		760
679	=head1 EXAMPLE PROGRAM	761	=head1 EXAMPLE PROGRAM
680		762
681	The following program uses an IO watcher to read data from STDIN, a timer	763	The following program uses an I/O watcher to read data from STDIN, a timer
682	to display a message once per second, and a condition variable to quit the	764	to display a message once per second, and a condition variable to quit the
683	program when the user enters quit:	765	program when the user enters quit:
684		766
685	use AnyEvent;	767	use AnyEvent;
686		768
…		…
830	$quit->broadcast;	912	$quit->broadcast;
831	});	913	});
832		914
833	$quit->wait;	915	$quit->wait;
834		916
		917
		918	=head1 BENCHMARKS
		919
		920	To give you an idea of the performance and overheads that AnyEvent adds
		921	over the event loops themselves and to give you an impression of the speed
		922	of various event loops I prepared some benchmarks.
		923
		924	=head2 BENCHMARKING ANYEVENT OVERHEAD
		925
		926	Here is a benchmark of various supported event models used natively and
		927	through anyevent. The benchmark creates a lot of timers (with a zero
		928	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
		929	which it is), lets them fire exactly once and destroys them again.
		930
		931	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
		932	distribution.
		933
		934	=head3 Explanation of the columns
		935
		936	I<watcher> is the number of event watchers created/destroyed. Since
		937	different event models feature vastly different performances, each event
		938	loop was given a number of watchers so that overall runtime is acceptable
		939	and similar between tested event loop (and keep them from crashing): Glib
		940	would probably take thousands of years if asked to process the same number
		941	of watchers as EV in this benchmark.
		942
		943	I<bytes> is the number of bytes (as measured by the resident set size,
		944	RSS) consumed by each watcher. This method of measuring captures both C
		945	and Perl-based overheads.
		946
		947	I<create> is the time, in microseconds (millionths of seconds), that it
		948	takes to create a single watcher. The callback is a closure shared between
		949	all watchers, to avoid adding memory overhead. That means closure creation
		950	and memory usage is not included in the figures.
		951
		952	I<invoke> is the time, in microseconds, used to invoke a simple
		953	callback. The callback simply counts down a Perl variable and after it was
		954	invoked "watcher" times, it would C<< ->broadcast >> a condvar once to
		955	signal the end of this phase.
		956
		957	I<destroy> is the time, in microseconds, that it takes to destroy a single
		958	watcher.
		959
		960	=head3 Results
		961
		962	name watchers bytes create invoke destroy comment
		963	EV/EV 400000 244 0.56 0.46 0.31 EV native interface
		964	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers
		965	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal
		966	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation
		967	Event/Event 16000 516 31.88 31.30 0.85 Event native interface
		968	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers
		969	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour
		970	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers
		971	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event
		972	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select
		973
		974	=head3 Discussion
		975
		976	The benchmark does I<not> measure scalability of the event loop very
		977	well. For example, a select-based event loop (such as the pure perl one)
		978	can never compete with an event loop that uses epoll when the number of
		979	file descriptors grows high. In this benchmark, all events become ready at
		980	the same time, so select/poll-based implementations get an unnatural speed
		981	boost.
		982
		983	Also, note that the number of watchers usually has a nonlinear effect on
		984	overall speed, that is, creating twice as many watchers doesn't take twice
		985	the time - usually it takes longer. This puts event loops tested with a
		986	higher number of watchers at a disadvantage.
		987
		988	To put the range of results into perspective, consider that on the
		989	benchmark machine, handling an event takes roughly 1600 CPU cycles with
		990	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
		991	cycles with POE.
		992
		993	C<EV> is the sole leader regarding speed and memory use, which are both
		994	maximal/minimal, respectively. Even when going through AnyEvent, it uses
		995	far less memory than any other event loop and is still faster than Event
		996	natively.
		997
		998	The pure perl implementation is hit in a few sweet spots (both the
		999	constant timeout and the use of a single fd hit optimisations in the perl
		1000	interpreter and the backend itself). Nevertheless this shows that it
		1001	adds very little overhead in itself. Like any select-based backend its
		1002	performance becomes really bad with lots of file descriptors (and few of
		1003	them active), of course, but this was not subject of this benchmark.
		1004
		1005	The C<Event> module has a relatively high setup and callback invocation
		1006	cost, but overall scores in on the third place.
		1007
		1008	C<Glib>'s memory usage is quite a bit higher, but it features a
		1009	faster callback invocation and overall ends up in the same class as
		1010	C<Event>. However, Glib scales extremely badly, doubling the number of
		1011	watchers increases the processing time by more than a factor of four,
		1012	making it completely unusable when using larger numbers of watchers
		1013	(note that only a single file descriptor was used in the benchmark, so
		1014	inefficiencies of C<poll> do not account for this).
		1015
		1016	The C<Tk> adaptor works relatively well. The fact that it crashes with
		1017	more than 2000 watchers is a big setback, however, as correctness takes
		1018	precedence over speed. Nevertheless, its performance is surprising, as the
		1019	file descriptor is dup()ed for each watcher. This shows that the dup()
		1020	employed by some adaptors is not a big performance issue (it does incur a
		1021	hidden memory cost inside the kernel which is not reflected in the figures
		1022	above).
		1023
		1024	C<POE>, regardless of underlying event loop (whether using its pure
		1025	perl select-based backend or the Event module, the POE-EV backend
		1026	couldn't be tested because it wasn't working) shows abysmal performance
		1027	and memory usage: Watchers use almost 30 times as much memory as
		1028	EV watchers, and 10 times as much memory as Event (the high memory
		1029	requirements are caused by requiring a session for each watcher). Watcher
		1030	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		1031	implementation. The design of the POE adaptor class in AnyEvent can not
		1032	really account for this, as session creation overhead is small compared
		1033	to execution of the state machine, which is coded pretty optimally within
		1034	L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow.
		1035
		1036	=head3 Summary
		1037
		1038	=over 4
		1039
		1040	=item * Using EV through AnyEvent is faster than any other event loop
		1041	(even when used without AnyEvent), but most event loops have acceptable
		1042	performance with or without AnyEvent.
		1043
		1044	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
		1045	the actual event loop, only with extremely fast event loops such as EV
		1046	adds AnyEvent significant overhead.
		1047
		1048	=item * You should avoid POE like the plague if you want performance or
		1049	reasonable memory usage.
		1050
		1051	=back
		1052
		1053	=head2 BENCHMARKING THE LARGE SERVER CASE
		1054
		1055	This benchmark atcually benchmarks the event loop itself. It works by
		1056	creating a number of "servers": each server consists of a socketpair, a
		1057	timeout watcher that gets reset on activity (but never fires), and an I/O
		1058	watcher waiting for input on one side of the socket. Each time the socket
		1059	watcher reads a byte it will write that byte to a random other "server".
		1060
		1061	The effect is that there will be a lot of I/O watchers, only part of which
		1062	are active at any one point (so there is a constant number of active
		1063	fds for each loop iterstaion, but which fds these are is random). The
		1064	timeout is reset each time something is read because that reflects how
		1065	most timeouts work (and puts extra pressure on the event loops).
		1066
		1067	In this benchmark, we use 10000 socketpairs (20000 sockets), of which 100
		1068	(1%) are active. This mirrors the activity of large servers with many
		1069	connections, most of which are idle at any one point in time.
		1070
		1071	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
		1072	distribution.
		1073
		1074	=head3 Explanation of the columns
		1075
		1076	I<sockets> is the number of sockets, and twice the number of "servers" (as
		1077	each server has a read and write socket end).
		1078
		1079	I<create> is the time it takes to create a socketpair (which is
		1080	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
		1081
		1082	I<request>, the most important value, is the time it takes to handle a
		1083	single "request", that is, reading the token from the pipe and forwarding
		1084	it to another server. This includes deleting the old timeout and creating
		1085	a new one that moves the timeout into the future.
		1086
		1087	=head3 Results
		1088
		1089	name sockets create request
		1090	EV 20000 69.01 11.16
		1091	Perl 20000 75.28 112.76
		1092	Event 20000 212.62 257.32
		1093	Glib 20000 651.16 1896.30
		1094	POE 20000 349.67 12317.24 uses POE::Loop::Event
		1095
		1096	=head3 Discussion
		1097
		1098	This benchmark I<does> measure scalability and overall performance of the
		1099	particular event loop.
		1100
		1101	EV is again fastest. Since it is using epoll on my system, the setup time
		1102	is relatively high, though.
		1103
		1104	Perl surprisingly comes second. It is much faster than the C-based event
		1105	loops Event and Glib.
		1106
		1107	Event suffers from high setup time as well (look at its code and you will
		1108	understand why). Callback invocation also has a high overhead compared to
		1109	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
		1110	uses select or poll in basically all documented configurations.
		1111
		1112	Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It
		1113	clearly fails to perform with many filehandles or in busy servers.
		1114
		1115	POE is still completely out of the picture, taking over 1000 times as long
		1116	as EV, and over 100 times as long as the Perl implementation, even though
		1117	it uses a C-based event loop in this case.
		1118
		1119	=head3 Summary
		1120
		1121	=over 4
		1122
		1123	=item * The pure perl implementation performs extremely well, considering
		1124	that it uses select.
		1125
		1126	=item * Avoid Glib or POE in large projects where performance matters.
		1127
		1128	=back
		1129
		1130	=head2 BENCHMARKING SMALL SERVERS
		1131
		1132	While event loops should scale (and select-based ones do not...) even to
		1133	large servers, most programs we (or I :) actually write have only a few
		1134	I/O watchers.
		1135
		1136	In this benchmark, I use the same benchmark program as in the large server
		1137	case, but it uses only eight "servers", of which three are active at any
		1138	one time. This should reflect performance for a small server relatively
		1139	well.
		1140
		1141	The columns are identical to the previous table.
		1142
		1143	=head3 Results
		1144
		1145	name sockets create request
		1146	EV 16 20.00 6.54
		1147	Event 16 81.27 35.86
		1148	Glib 16 32.63 15.48
		1149	Perl 16 24.62 162.37
		1150	POE 16 261.87 276.28 uses POE::Loop::Event
		1151
		1152	=head3 Discussion
		1153
		1154	The benchmark tries to test the performance of a typical small
		1155	server. While knowing how various event loops perform is interesting, keep
		1156	in mind that their overhead in this case is usually not as important, due
		1157	to the small absolute number of watchers (that is, you need efficiency and
		1158	speed most when you have lots of watchers, not when you only have a few of
		1159	them).
		1160
		1161	EV is again fastest.
		1162
		1163	The C-based event loops Event and Glib come in second this time, as the
		1164	overhead of running an iteration is much smaller in C than in Perl (little
		1165	code to execute in the inner loop, and perl's function calling overhead is
		1166	high, and updating all the data structures is costly).
		1167
		1168	The pure perl event loop is much slower, but still competitive.
		1169
		1170	POE also performs much better in this case, but is is still far behind the
		1171	others.
		1172
		1173	=head3 Summary
		1174
		1175	=over 4
		1176
		1177	=item * C-based event loops perform very well with small number of
		1178	watchers, as the management overhead dominates.
		1179
		1180	=back
		1181
		1182
835	=head1 FORK	1183	=head1 FORK
836		1184
837	Most event libraries are not fork-safe. The ones who are usually are	1185	Most event libraries are not fork-safe. The ones who are usually are
838	because they are so inefficient. Only L<EV> is fully fork-aware.	1186	because they are so inefficient. Only L<EV> is fully fork-aware.
839		1187
840	If you have to fork, you must either do so I<before> creating your first	1188	If you have to fork, you must either do so I<before> creating your first
841	watcher OR you must not use AnyEvent at all in the child.	1189	watcher OR you must not use AnyEvent at all in the child.
		1190
842		1191
843	=head1 SECURITY CONSIDERATIONS	1192	=head1 SECURITY CONSIDERATIONS
844		1193
845	AnyEvent can be forced to load any event model via	1194	AnyEvent can be forced to load any event model via
846	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to	1195	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
…		…
854		1203
855	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	1204	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
856		1205
857	use AnyEvent;	1206	use AnyEvent;
858		1207
		1208
859	=head1 SEE ALSO	1209	=head1 SEE ALSO
860		1210
861	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	1211	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,
862	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,	1212	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,
863	L<Event::Lib>.	1213	L<Event::Lib>, L<Qt>, L<POE>.
864		1214
865	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	1215	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,
866	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,	1216	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,
867	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>.	1217	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,
		1218	L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.
868		1219
869	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	1220	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.
		1221
870		1222
871	=head1 AUTHOR	1223	=head1 AUTHOR
872		1224
873	Marc Lehmann <schmorp@schmorp.de>	1225	Marc Lehmann <schmorp@schmorp.de>
874	http://home.schmorp.de/	1226	http://home.schmorp.de/

Diff Legend

-–
+Removed lines
-+
+Added lines
-<
+Changed lines
->
+Changed lines

Comparing AnyEvent/lib/AnyEvent.pm (file contents): Revision 1.55 by root, Wed Apr 23 11:25:42 2008 UTC vs. Revision 1.98 by root, Sun Apr 27 16:31:48 2008 UTC

Diff Legend

Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.55 by root, Wed Apr 23 11:25:42 2008 UTC vs.
Revision 1.98 by root, Sun Apr 27 16:31:48 2008 UTC