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

Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.71 by root, Fri Apr 25 07:29:42 2008 UTC vs.
Revision 1.102 by root, Sun Apr 27 21:16:26 2008 UTC

…		…
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
72	=head1 DESCRIPTION	71	=head1 DESCRIPTION
73		72
74	L<AnyEvent> provides an identical interface to multiple event loops. This	73	L<AnyEvent> provides an identical interface to multiple event loops. This
75	allows module authors to utilise an event loop without forcing module	74	allows module authors to utilise an event loop without forcing module
76	users to use the same event loop (as only a single event loop can coexist	75	users to use the same event loop (as only a single event loop can coexist
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80	module.	79	module.
81		80
82	During the first call of any watcher-creation method, the module tries	81	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	82	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>,	83	following modules is already loaded: L<Coro::EV>, L<Coro::Event>, L<EV>,
85	L<Event>, L<Glib>, L<Tk>, L<AnyEvent::Impl::Perl>, L<Event::Lib>, L<Qt>,	84	L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,
86	L<POE>. The first one found is used. If none are found, the module tries	85	L<POE>. The first one found is used. If none are found, the module tries
87	to load these modules (excluding Event::Lib, Qt and POE as the pure perl	86	to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl
88	adaptor should always succeed) in the order given. The first one that can	87	adaptor should always succeed) in the order given. The first one that can
89	be successfully loaded will be used. If, after this, still none could be	88	be successfully loaded will be used. If, after this, still none could be
90	found, AnyEvent will fall back to a pure-perl event loop, which is not	89	found, AnyEvent will fall back to a pure-perl event loop, which is not
91	very efficient, but should work everywhere.	90	very efficient, but should work everywhere.
92		91
…		…
136		135
137	Note that C<my $w; $w => combination. This is necessary because in Perl,	136	Note that C<my $w; $w => combination. This is necessary because in Perl,
138	my variables are only visible after the statement in which they are	137	my variables are only visible after the statement in which they are
139	declared.	138	declared.
140		139
141	=head2 IO WATCHERS	140	=head2 I/O WATCHERS
142		141
143	You can create an I/O watcher by calling the C<< AnyEvent->io >> method	142	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
144	with the following mandatory key-value pairs as arguments:	143	with the following mandatory key-value pairs as arguments:
145		144
146	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch for	145	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch
147	events. C<poll> must be a string that is either C<r> or C<w>, which	146	for events. C<poll> must be a string that is either C<r> or C<w>,
148	creates a watcher waiting for "r"eadable or "w"ritable events,	147	which creates a watcher waiting for "r"eadable or "w"ritable events,
149	respectively. C<cb> is the callback to invoke each time the file handle	148	respectively. C<cb> is the callback to invoke each time the file handle
150	becomes ready.	149	becomes ready.
151		150
152	As long as the I/O watcher exists it will keep the file descriptor or a	151	Although the callback might get passed parameters, their value and
153	copy of it alive/open.	152	presence is undefined and you cannot rely on them. Portable AnyEvent
		153	callbacks cannot use arguments passed to I/O watcher callbacks.
154		154
		155	The I/O watcher might use the underlying file descriptor or a copy of it.
155	It is not allowed to close a file handle as long as any watcher is active	156	You must not close a file handle as long as any watcher is active on the
156	on the underlying file descriptor.	157	underlying file descriptor.
157		158
158	Some event loops issue spurious readyness notifications, so you should	159	Some event loops issue spurious readyness notifications, so you should
159	always use non-blocking calls when reading/writing from/to your file	160	always use non-blocking calls when reading/writing from/to your file
160	handles.	161	handles.
161		162
…		…
172		173
173	You can create a time watcher by calling the C<< AnyEvent->timer >>	174	You can create a time watcher by calling the C<< AnyEvent->timer >>
174	method with the following mandatory arguments:	175	method with the following mandatory arguments:
175		176
176	C<after> specifies after how many seconds (fractional values are	177	C<after> specifies after how many seconds (fractional values are
177	supported) should the timer activate. C<cb> the callback to invoke in that	178	supported) the callback should be invoked. C<cb> is the callback to invoke
178	case.	179	in that case.
		180
		181	Although the callback might get passed parameters, their value and
		182	presence is undefined and you cannot rely on them. Portable AnyEvent
		183	callbacks cannot use arguments passed to time watcher callbacks.
179		184
180	The timer callback will be invoked at most once: if you want a repeating	185	The timer callback will be invoked at most once: if you want a repeating
181	timer you have to create a new watcher (this is a limitation by both Tk	186	timer you have to create a new watcher (this is a limitation by both Tk
182	and Glib).	187	and Glib).
183		188
…		…
228		233
229	You can watch for signals using a signal watcher, C<signal> is the signal	234	You can watch for signals using a signal watcher, C<signal> is the signal
230	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to	235	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to
231	be invoked whenever a signal occurs.	236	be invoked whenever a signal occurs.
232		237
		238	Although the callback might get passed parameters, their value and
		239	presence is undefined and you cannot rely on them. Portable AnyEvent
		240	callbacks cannot use arguments passed to signal watcher callbacks.
		241
233	Multiple signal occurances can be clumped together into one callback	242	Multiple signal occurances can be clumped together into one callback
234	invocation, and callback invocation will be synchronous. synchronous means	243	invocation, and callback invocation will be synchronous. synchronous means
235	that it might take a while until the signal gets handled by the process,	244	that it might take a while until the signal gets handled by the process,
236	but it is guarenteed not to interrupt any other callbacks.	245	but it is guarenteed not to interrupt any other callbacks.
237		246
…		…
251		260
252	The child process is specified by the C<pid> argument (if set to C<0>, it	261	The child process is specified by the C<pid> argument (if set to C<0>, it
253	watches for any child process exit). The watcher will trigger as often	262	watches for any child process exit). The watcher will trigger as often
254	as status change for the child are received. This works by installing a	263	as status change for the child are received. This works by installing a
255	signal handler for C<SIGCHLD>. The callback will be called with the pid	264	signal handler for C<SIGCHLD>. The callback will be called with the pid
256	and exit status (as returned by waitpid).	265	and exit status (as returned by waitpid), so unlike other watcher types,
		266	you I<can> rely on child watcher callback arguments.
257		267
258	Example: wait for pid 1333	268	There is a slight catch to child watchers, however: you usually start them
		269	I<after> the child process was created, and this means the process could
		270	have exited already (and no SIGCHLD will be sent anymore).
		271
		272	Not all event models handle this correctly (POE doesn't), but even for
		273	event models that I<do> handle this correctly, they usually need to be
		274	loaded before the process exits (i.e. before you fork in the first place).
		275
		276	This means you cannot create a child watcher as the very first thing in an
		277	AnyEvent program, you I<have> to create at least one watcher before you
		278	C<fork> the child (alternatively, you can call C<AnyEvent::detect>).
		279
		280	Example: fork a process and wait for it
		281
		282	my $done = AnyEvent->condvar;
		283
		284	AnyEvent::detect; # force event module to be initialised
		285
		286	my $pid = fork or exit 5;
259		287
260	my $w = AnyEvent->child (	288	my $w = AnyEvent->child (
261	pid => 1333,	289	pid => $pid,
262	cb => sub {	290	cb => sub {
263	my ($pid, $status) = @_;	291	my ($pid, $status) = @_;
264	warn "pid $pid exited with status $status";	292	warn "pid $pid exited with status $status";
		293	$done->broadcast;
265	},	294	},
266	);	295	);
		296
		297	# do something else, then wait for process exit
		298	$done->wait;
267		299
268	=head2 CONDITION VARIABLES	300	=head2 CONDITION VARIABLES
269		301
270	Condition variables can be created by calling the C<< AnyEvent->condvar >>	302	Condition variables can be created by calling the C<< AnyEvent->condvar >>
271	method without any arguments.	303	method without any arguments.
…		…
359	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.	391	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
360	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.	392	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
361	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).	393	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
362	AnyEvent::Impl::Event based on Event, second best choice.	394	AnyEvent::Impl::Event based on Event, second best choice.
363	AnyEvent::Impl::Glib based on Glib, third-best choice.	395	AnyEvent::Impl::Glib based on Glib, third-best choice.
		396	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
364	AnyEvent::Impl::Tk based on Tk, very bad choice.	397	AnyEvent::Impl::Tk based on Tk, very bad choice.
365	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
366	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).	398	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
367	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.	399	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
368	AnyEvent::Impl::POE based on POE, not generic enough for full support.	400	AnyEvent::Impl::POE based on POE, not generic enough for full support.
369		401
370	There is no support for WxWidgets, as WxWidgets has no support for	402	There is no support for WxWidgets, as WxWidgets has no support for
…		…
424	might chose the wrong one unless you load the correct one yourself.	456	might chose the wrong one unless you load the correct one yourself.
425		457
426	You can chose to use a rather inefficient pure-perl implementation by	458	You can chose to use a rather inefficient pure-perl implementation by
427	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	459	loading the C<AnyEvent::Impl::Perl> module, which gives you similar
428	behaviour everywhere, but letting AnyEvent chose is generally better.	460	behaviour everywhere, but letting AnyEvent chose is generally better.
		461
		462	=head1 OTHER MODULES
		463
		464	The following is a non-exhaustive list of additional modules that use
		465	AnyEvent and can therefore be mixed easily with other AnyEvent modules
		466	in the same program. Some of the modules come with AnyEvent, some are
		467	available via CPAN.
		468
		469	=over 4
		470
		471	=item L<AnyEvent::Util>
		472
		473	Contains various utility functions that replace often-used but blocking
		474	functions such as C<inet_aton> by event-/callback-based versions.
		475
		476	=item L<AnyEvent::Handle>
		477
		478	Provide read and write buffers and manages watchers for reads and writes.
		479
		480	=item L<AnyEvent::Socket>
		481
		482	Provides a means to do non-blocking connects, accepts etc.
		483
		484	=item L<AnyEvent::HTTPD>
		485
		486	Provides a simple web application server framework.
		487
		488	=item L<AnyEvent::DNS>
		489
		490	Provides asynchronous DNS resolver capabilities, beyond what
		491	L<AnyEvent::Util> offers.
		492
		493	=item L<AnyEvent::FastPing>
		494
		495	The fastest ping in the west.
		496
		497	=item L<Net::IRC3>
		498
		499	AnyEvent based IRC client module family.
		500
		501	=item L<Net::XMPP2>
		502
		503	AnyEvent based XMPP (Jabber protocol) module family.
		504
		505	=item L<Net::FCP>
		506
		507	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
		508	of AnyEvent.
		509
		510	=item L<Event::ExecFlow>
		511
		512	High level API for event-based execution flow control.
		513
		514	=item L<Coro>
		515
		516	Has special support for AnyEvent.
		517
		518	=item L<IO::Lambda>
		519
		520	The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
		521
		522	=item L<IO::AIO>
		523
		524	Truly asynchronous I/O, should be in the toolbox of every event
		525	programmer. Can be trivially made to use AnyEvent.
		526
		527	=item L<BDB>
		528
		529	Truly asynchronous Berkeley DB access. Can be trivially made to use
		530	AnyEvent.
		531
		532	=back
429		533
430	=cut	534	=cut
431		535
432	package AnyEvent;	536	package AnyEvent;
433		537
…		…
706		810
707	=back	811	=back
708		812
709	=head1 EXAMPLE PROGRAM	813	=head1 EXAMPLE PROGRAM
710		814
711	The following program uses an IO watcher to read data from STDIN, a timer	815	The following program uses an I/O watcher to read data from STDIN, a timer
712	to display a message once per second, and a condition variable to quit the	816	to display a message once per second, and a condition variable to quit the
713	program when the user enters quit:	817	program when the user enters quit:
714		818
715	use AnyEvent;	819	use AnyEvent;
716		820
…		…
861	});	965	});
862		966
863	$quit->wait;	967	$quit->wait;
864		968
865		969
866	=head1 BENCHMARK	970	=head1 BENCHMARKS
867		971
868	To give you an idea of the performance and overheads that AnyEvent adds	972	To give you an idea of the performance and overheads that AnyEvent adds
869	over the event loops themselves (and to give you an impression of the	973	over the event loops themselves and to give you an impression of the speed
870	speed of various event loops), here is a benchmark of various supported	974	of various event loops I prepared some benchmarks.
871	event models natively and with anyevent. The benchmark creates a lot of	975
872	timers (with a zero timeout) and io watchers (watching STDOUT, a pty, to	976	=head2 BENCHMARKING ANYEVENT OVERHEAD
		977
		978	Here is a benchmark of various supported event models used natively and
		979	through anyevent. The benchmark creates a lot of timers (with a zero
		980	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
873	become writable, which it is), lets them fire exactly once and destroys	981	which it is), lets them fire exactly once and destroys them again.
874	them again.
875		982
		983	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
		984	distribution.
		985
876	=head2 Explanation of the columns	986	=head3 Explanation of the columns
877		987
878	I<watcher> is the number of event watchers created/destroyed. Since	988	I<watcher> is the number of event watchers created/destroyed. Since
879	different event models feature vastly different performances, each event	989	different event models feature vastly different performances, each event
880	loop was given a number of watchers so that overall runtime is acceptable	990	loop was given a number of watchers so that overall runtime is acceptable
881	and similar between tested event loop (and keep them from crashing): Glib	991	and similar between tested event loop (and keep them from crashing): Glib
…		…
897	signal the end of this phase.	1007	signal the end of this phase.
898		1008
899	I<destroy> is the time, in microseconds, that it takes to destroy a single	1009	I<destroy> is the time, in microseconds, that it takes to destroy a single
900	watcher.	1010	watcher.
901		1011
902	=head2 Results	1012	=head3 Results
903		1013
904	name watcher bytes create invoke destroy comment	1014	name watchers bytes create invoke destroy comment
905	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	1015	EV/EV 400000 244 0.56 0.46 0.31 EV native interface
906	EV/Any 100000 610 3.52 0.91 0.75 EV + AnyEvent watchers	1016	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers
907	CoroEV/Any 100000 610 3.49 0.92 0.75 coroutines + Coro::Signal	1017	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal
908	Perl/Any 16000 654 4.64 1.22 0.77 pure perl implementation	1018	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation
909	Event/Event 16000 523 28.05 21.38 0.86 Event native interface	1019	Event/Event 16000 516 31.88 31.30 0.85 Event native interface
910	Event/Any 16000 943 34.43 20.48 1.39 Event + AnyEvent watchers	1020	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers
911	Glib/Any 16000 1357 96.99 12.55 55.51 quadratic behaviour	1021	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour
912	Tk/Any 2000 1855 27.01 66.61 14.03 SEGV with >> 2000 watchers	1022	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers
913	POE/Event 2000 6644 108.15 768.19 14.33 via POE::Loop::Event	1023	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event
914	POE/Select 2000 6343 94.69 807.65 562.69 via POE::Loop::Select	1024	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select
915		1025
916	=head2 Discussion	1026	=head3 Discussion
917		1027
918	The benchmark does I<not> measure scalability of the event loop very	1028	The benchmark does I<not> measure scalability of the event loop very
919	well. For example, a select-based event loop (such as the pure perl one)	1029	well. For example, a select-based event loop (such as the pure perl one)
920	can never compete with an event loop that uses epoll when the number of	1030	can never compete with an event loop that uses epoll when the number of
921	file descriptors grows high. In this benchmark, only a single filehandle	1031	file descriptors grows high. In this benchmark, all events become ready at
922	is used (although some of the AnyEvent adaptors dup() its file descriptor	1032	the same time, so select/poll-based implementations get an unnatural speed
923	to worka round bugs).	1033	boost.
		1034
		1035	Also, note that the number of watchers usually has a nonlinear effect on
		1036	overall speed, that is, creating twice as many watchers doesn't take twice
		1037	the time - usually it takes longer. This puts event loops tested with a
		1038	higher number of watchers at a disadvantage.
		1039
		1040	To put the range of results into perspective, consider that on the
		1041	benchmark machine, handling an event takes roughly 1600 CPU cycles with
		1042	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
		1043	cycles with POE.
924		1044
925	C<EV> is the sole leader regarding speed and memory use, which are both	1045	C<EV> is the sole leader regarding speed and memory use, which are both
926	maximal/minimal, respectively. Even when going through AnyEvent, there is	1046	maximal/minimal, respectively. Even when going through AnyEvent, it uses
927	only one event loop that uses less memory (the C<Event> module natively), and	1047	far less memory than any other event loop and is still faster than Event
928	no faster event model, not event C<Event> natively.	1048	natively.
929		1049
930	The pure perl implementation is hit in a few sweet spots (both the	1050	The pure perl implementation is hit in a few sweet spots (both the
931	zero timeout and the use of a single fd hit optimisations in the perl	1051	constant timeout and the use of a single fd hit optimisations in the perl
932	interpreter and the backend itself). Nevertheless tis shows that it	1052	interpreter and the backend itself). Nevertheless this shows that it
933	adds very little overhead in itself. Like any select-based backend its	1053	adds very little overhead in itself. Like any select-based backend its
934	performance becomes really bad with lots of file descriptors, of course,	1054	performance becomes really bad with lots of file descriptors (and few of
935	but this was not subjetc of this benchmark.	1055	them active), of course, but this was not subject of this benchmark.
936		1056
937	The C<Event> module has a relatively high setup and callback invocation cost,	1057	The C<Event> module has a relatively high setup and callback invocation
938	but overall scores on the third place.	1058	cost, but overall scores in on the third place.
939		1059
940	C<Glib>'s memory usage is quite a bit bit higher, features a faster	1060	C<Glib>'s memory usage is quite a bit higher, but it features a
941	callback invocation and overall lands in the same class as C<Event>.	1061	faster callback invocation and overall ends up in the same class as
		1062	C<Event>. However, Glib scales extremely badly, doubling the number of
		1063	watchers increases the processing time by more than a factor of four,
		1064	making it completely unusable when using larger numbers of watchers
		1065	(note that only a single file descriptor was used in the benchmark, so
		1066	inefficiencies of C<poll> do not account for this).
942		1067
943	The C<Tk> adaptor works relatively well, the fact that it crashes with	1068	The C<Tk> adaptor works relatively well. The fact that it crashes with
944	more than 2000 watchers is a big setback, however, as correctness takes	1069	more than 2000 watchers is a big setback, however, as correctness takes
945	precedence over speed. Nevertheless, its performance is surprising, as the	1070	precedence over speed. Nevertheless, its performance is surprising, as the
946	file descriptor is dup()ed for each watcher. This shows that the dup()	1071	file descriptor is dup()ed for each watcher. This shows that the dup()
947	employed by some adaptors is not a big performance issue (it does incur a	1072	employed by some adaptors is not a big performance issue (it does incur a
948	hidden memory cost inside the kernel, though).	1073	hidden memory cost inside the kernel which is not reflected in the figures
		1074	above).
949		1075
950	C<POE>, regardless of backend (wether using its pure perl select-based	1076	C<POE>, regardless of underlying event loop (whether using its pure
951	backend or the Event backend) shows abysmal performance and memory	1077	perl select-based backend or the Event module, the POE-EV backend
		1078	couldn't be tested because it wasn't working) shows abysmal performance
952	usage: Watchers use almost 30 times as much memory as EV watchers, and 10	1079	and memory usage: Watchers use almost 30 times as much memory as
953	times as much memory as both Event or EV via AnyEvent. Watcher invocation	1080	EV watchers, and 10 times as much memory as Event (the high memory
954	is almost 700 times slower as with AnyEvent's pure perl implementation.	1081	requirements are caused by requiring a session for each watcher). Watcher
		1082	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		1083	implementation. The design of the POE adaptor class in AnyEvent can not
		1084	really account for this, as session creation overhead is small compared
		1085	to execution of the state machine, which is coded pretty optimally within
		1086	L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow.
955		1087
		1088	=head3 Summary
		1089
		1090	=over 4
		1091
956	Summary: using EV through AnyEvent is faster than any other event	1092	=item * Using EV through AnyEvent is faster than any other event loop
957	loop. The overhead AnyEvent adds can be very small, and you should avoid	1093	(even when used without AnyEvent), but most event loops have acceptable
958	POE like the plague if you want performance or reasonable memory usage.	1094	performance with or without AnyEvent.
		1095
		1096	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
		1097	the actual event loop, only with extremely fast event loops such as EV
		1098	adds AnyEvent significant overhead.
		1099
		1100	=item * You should avoid POE like the plague if you want performance or
		1101	reasonable memory usage.
		1102
		1103	=back
		1104
		1105	=head2 BENCHMARKING THE LARGE SERVER CASE
		1106
		1107	This benchmark atcually benchmarks the event loop itself. It works by
		1108	creating a number of "servers": each server consists of a socketpair, a
		1109	timeout watcher that gets reset on activity (but never fires), and an I/O
		1110	watcher waiting for input on one side of the socket. Each time the socket
		1111	watcher reads a byte it will write that byte to a random other "server".
		1112
		1113	The effect is that there will be a lot of I/O watchers, only part of which
		1114	are active at any one point (so there is a constant number of active
		1115	fds for each loop iterstaion, but which fds these are is random). The
		1116	timeout is reset each time something is read because that reflects how
		1117	most timeouts work (and puts extra pressure on the event loops).
		1118
		1119	In this benchmark, we use 10000 socketpairs (20000 sockets), of which 100
		1120	(1%) are active. This mirrors the activity of large servers with many
		1121	connections, most of which are idle at any one point in time.
		1122
		1123	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
		1124	distribution.
		1125
		1126	=head3 Explanation of the columns
		1127
		1128	I<sockets> is the number of sockets, and twice the number of "servers" (as
		1129	each server has a read and write socket end).
		1130
		1131	I<create> is the time it takes to create a socketpair (which is
		1132	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
		1133
		1134	I<request>, the most important value, is the time it takes to handle a
		1135	single "request", that is, reading the token from the pipe and forwarding
		1136	it to another server. This includes deleting the old timeout and creating
		1137	a new one that moves the timeout into the future.
		1138
		1139	=head3 Results
		1140
		1141	name sockets create request
		1142	EV 20000 69.01 11.16
		1143	Perl 20000 73.32 35.87
		1144	Event 20000 212.62 257.32
		1145	Glib 20000 651.16 1896.30
		1146	POE 20000 349.67 12317.24 uses POE::Loop::Event
		1147
		1148	=head3 Discussion
		1149
		1150	This benchmark I<does> measure scalability and overall performance of the
		1151	particular event loop.
		1152
		1153	EV is again fastest. Since it is using epoll on my system, the setup time
		1154	is relatively high, though.
		1155
		1156	Perl surprisingly comes second. It is much faster than the C-based event
		1157	loops Event and Glib.
		1158
		1159	Event suffers from high setup time as well (look at its code and you will
		1160	understand why). Callback invocation also has a high overhead compared to
		1161	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
		1162	uses select or poll in basically all documented configurations.
		1163
		1164	Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It
		1165	clearly fails to perform with many filehandles or in busy servers.
		1166
		1167	POE is still completely out of the picture, taking over 1000 times as long
		1168	as EV, and over 100 times as long as the Perl implementation, even though
		1169	it uses a C-based event loop in this case.
		1170
		1171	=head3 Summary
		1172
		1173	=over 4
		1174
		1175	=item * The pure perl implementation performs extremely well, considering
		1176	that it uses select.
		1177
		1178	=item * Avoid Glib or POE in large projects where performance matters.
		1179
		1180	=back
		1181
		1182	=head2 BENCHMARKING SMALL SERVERS
		1183
		1184	While event loops should scale (and select-based ones do not...) even to
		1185	large servers, most programs we (or I :) actually write have only a few
		1186	I/O watchers.
		1187
		1188	In this benchmark, I use the same benchmark program as in the large server
		1189	case, but it uses only eight "servers", of which three are active at any
		1190	one time. This should reflect performance for a small server relatively
		1191	well.
		1192
		1193	The columns are identical to the previous table.
		1194
		1195	=head3 Results
		1196
		1197	name sockets create request
		1198	EV 16 20.00 6.54
		1199	Perl 16 25.75 12.62
		1200	Event 16 81.27 35.86
		1201	Glib 16 32.63 15.48
		1202	POE 16 261.87 276.28 uses POE::Loop::Event
		1203
		1204	=head3 Discussion
		1205
		1206	The benchmark tries to test the performance of a typical small
		1207	server. While knowing how various event loops perform is interesting, keep
		1208	in mind that their overhead in this case is usually not as important, due
		1209	to the small absolute number of watchers (that is, you need efficiency and
		1210	speed most when you have lots of watchers, not when you only have a few of
		1211	them).
		1212
		1213	EV is again fastest.
		1214
		1215	Perl again comes second. It is noticably faster than the C-based event
		1216	loops Event and Glib, although the difference is too small to really
		1217	matter.
		1218
		1219	POE also performs much better in this case, but is is still far behind the
		1220	others.
		1221
		1222	=head3 Summary
		1223
		1224	=over 4
		1225
		1226	=item * C-based event loops perform very well with small number of
		1227	watchers, as the management overhead dominates.
		1228
		1229	=back
959		1230
960		1231
961	=head1 FORK	1232	=head1 FORK
962		1233
963	Most event libraries are not fork-safe. The ones who are usually are	1234	Most event libraries are not fork-safe. The ones who are usually are

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Comparing AnyEvent/lib/AnyEvent.pm (file contents): Revision 1.71 by root, Fri Apr 25 07:29:42 2008 UTC vs. Revision 1.102 by root, Sun Apr 27 21:16:26 2008 UTC

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Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.71 by root, Fri Apr 25 07:29:42 2008 UTC vs.
Revision 1.102 by root, Sun Apr 27 21:16:26 2008 UTC