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

Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.76 by root, Fri Apr 25 08:41:38 2008 UTC vs.
Revision 1.100 by elmex, Sun Apr 27 19:15:43 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	#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>, L<AnyEvent::Impl::Perl>, L<Event::Lib>, L<Qt>,	104	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	105	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	106	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	107	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	108	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	109	found, AnyEvent will fall back to a pure-perl event loop, which is not
91	very efficient, but should work everywhere.	110	very efficient, but should work everywhere.
92		111
…		…
136		155
137	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,
138	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
139	declared.	158	declared.
140		159
141	=head2 IO WATCHERS	160	=head2 I/O WATCHERS
142		161
143	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
144	with the following mandatory key-value pairs as arguments:	163	with the following mandatory key-value pairs as arguments:
145		164
146	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
147	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>,
148	creates a watcher waiting for "r"eadable or "w"ritable events,	167	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	168	respectively. C<cb> is the callback to invoke each time the file handle
150	becomes ready.	169	becomes ready.
151		170
152	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
153	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.
154		174
		175	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	176	You must not close a file handle as long as any watcher is active on the
156	on the underlying file descriptor.	177	underlying file descriptor.
157		178
158	Some event loops issue spurious readyness notifications, so you should	179	Some event loops issue spurious readyness notifications, so you should
159	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
160	handles.	181	handles.
161		182
…		…
172		193
173	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 >>
174	method with the following mandatory arguments:	195	method with the following mandatory arguments:
175		196
176	C<after> specifies after how many seconds (fractional values are	197	C<after> specifies after how many seconds (fractional values are
177	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
178	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.
179		204
180	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
181	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
182	and Glib).	207	and Glib).
183		208
…		…
228		253
229	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
230	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
231	be invoked whenever a signal occurs.	256	be invoked whenever a signal occurs.
232		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
233	Multiple signal occurances can be clumped together into one callback	262	Multiple signal occurances can be clumped together into one callback
234	invocation, and callback invocation will be synchronous. synchronous means	263	invocation, and callback invocation will be synchronous. synchronous means
235	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,
236	but it is guarenteed not to interrupt any other callbacks.	265	but it is guarenteed not to interrupt any other callbacks.
237		266
…		…
251		280
252	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
253	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
254	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
255	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
256	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.
257		287
258	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;
259		307
260	my $w = AnyEvent->child (	308	my $w = AnyEvent->child (
261	pid => 1333,	309	pid => $pid,
262	cb => sub {	310	cb => sub {
263	my ($pid, $status) = @_;	311	my ($pid, $status) = @_;
264	warn "pid $pid exited with status $status";	312	warn "pid $pid exited with status $status";
		313	$done->broadcast;
265	},	314	},
266	);	315	);
		316
		317	# do something else, then wait for process exit
		318	$done->wait;
267		319
268	=head2 CONDITION VARIABLES	320	=head2 CONDITION VARIABLES
269		321
270	Condition variables can be created by calling the C<< AnyEvent->condvar >>	322	Condition variables can be created by calling the C<< AnyEvent->condvar >>
271	method without any arguments.	323	method without any arguments.
…		…
359	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.	411	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
360	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.	412	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
361	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).
362	AnyEvent::Impl::Event based on Event, second best choice.	414	AnyEvent::Impl::Event based on Event, second best choice.
363	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.
364	AnyEvent::Impl::Tk based on Tk, very bad choice.	417	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).	418	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
367	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.	419	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
368	AnyEvent::Impl::POE based on POE, not generic enough for full support.	420	AnyEvent::Impl::POE based on POE, not generic enough for full support.
369		421
370	There is no support for WxWidgets, as WxWidgets has no support for	422	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.	476	might chose the wrong one unless you load the correct one yourself.
425		477
426	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
427	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	479	loading the C<AnyEvent::Impl::Perl> module, which gives you similar
428	behaviour everywhere, but letting AnyEvent chose is generally better.	480	behaviour everywhere, but letting AnyEvent chose is generally better.
		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
429		503
430	=cut	504	=cut
431		505
432	package AnyEvent;	506	package AnyEvent;
433		507
…		…
706		780
707	=back	781	=back
708		782
709	=head1 EXAMPLE PROGRAM	783	=head1 EXAMPLE PROGRAM
710		784
711	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
712	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
713	program when the user enters quit:	787	program when the user enters quit:
714		788
715	use AnyEvent;	789	use AnyEvent;
716		790
…		…
861	});	935	});
862		936
863	$quit->wait;	937	$quit->wait;
864		938
865		939
866	=head1 BENCHMARK	940	=head1 BENCHMARKS
867		941
868	To give you an idea of the performance and overheads that AnyEvent adds	942	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	943	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	944	of various event loops I prepared some benchmarks.
871	event models natively and with anyevent. The benchmark creates a lot of	945
872	timers (with a zero timeout) and io watchers (watching STDOUT, a pty, to	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,
873	become writable, which it is), lets them fire exactly once and destroys	951	which it is), lets them fire exactly once and destroys them again.
874	them again.
875		952
		953	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
		954	distribution.
		955
876	=head2 Explanation of the columns	956	=head3 Explanation of the columns
877		957
878	I<watcher> is the number of event watchers created/destroyed. Since	958	I<watcher> is the number of event watchers created/destroyed. Since
879	different event models feature vastly different performances, each event	959	different event models feature vastly different performances, each event
880	loop was given a number of watchers so that overall runtime is acceptable	960	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	961	and similar between tested event loop (and keep them from crashing): Glib
…		…
897	signal the end of this phase.	977	signal the end of this phase.
898		978
899	I<destroy> is the time, in microseconds, that it takes to destroy a single	979	I<destroy> is the time, in microseconds, that it takes to destroy a single
900	watcher.	980	watcher.
901		981
902	=head2 Results	982	=head3 Results
903		983
904	name watchers bytes create invoke destroy comment	984	name watchers bytes create invoke destroy comment
905	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	985	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	986	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	987	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal
908	Perl/Any 100000 513 4.91 0.92 1.15 pure perl implementation	988	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	989	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	990	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	991	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	992	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	993	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	994	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select
915		995
916	=head2 Discussion	996	=head3 Discussion
917		997
918	The benchmark does I<not> measure scalability of the event loop very	998	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)	999	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	1000	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	1001	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	1002	the same time, so select/poll-based implementations get an unnatural speed
923	to worka round bugs).	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.
924		1014
925	C<EV> is the sole leader regarding speed and memory use, which are both	1015	C<EV> is the sole leader regarding speed and memory use, which are both
926	maximal/minimal, respectively. Even when going through AnyEvent, there are	1016	maximal/minimal, respectively. Even when going through AnyEvent, it uses
927	only two event loops that use slightly less memory (the C<Event> module	1017	far less memory than any other event loop and is still faster than Event
928	natively and the pure perl backend), and no faster event models, not even	1018	natively.
929	C<Event> natively.
930		1019
931	The pure perl implementation is hit in a few sweet spots (both the	1020	The pure perl implementation is hit in a few sweet spots (both the
932	zero timeout and the use of a single fd hit optimisations in the perl	1021	constant timeout and the use of a single fd hit optimisations in the perl
933	interpreter and the backend itself). Nevertheless tis shows that it	1022	interpreter and the backend itself). Nevertheless this shows that it
934	adds very little overhead in itself. Like any select-based backend its	1023	adds very little overhead in itself. Like any select-based backend its
935	performance becomes really bad with lots of file descriptors, of course,	1024	performance becomes really bad with lots of file descriptors (and few of
936	but this was not subject of this benchmark.	1025	them active), of course, but this was not subject of this benchmark.
937		1026
938	The C<Event> module has a relatively high setup and callback invocation cost,	1027	The C<Event> module has a relatively high setup and callback invocation
939	but overall scores on the third place.	1028	cost, but overall scores in on the third place.
940		1029
941	C<Glib>'s memory usage is quite a bit bit higher, but it features a	1030	C<Glib>'s memory usage is quite a bit higher, but it features a
942	faster callback invocation and overall ends up in the same class as	1031	faster callback invocation and overall ends up in the same class as
943	C<Event>. However, Glib scales extremely badly, doubling the number of	1032	C<Event>. However, Glib scales extremely badly, doubling the number of
944	watchers increases the processing time by more than a factor of four,	1033	watchers increases the processing time by more than a factor of four,
945	making it completely unusable when using larger numbers of watchers	1034	making it completely unusable when using larger numbers of watchers
946	(note that only a single file descriptor was used in the benchmark, so	1035	(note that only a single file descriptor was used in the benchmark, so
…		…
949	The C<Tk> adaptor works relatively well. The fact that it crashes with	1038	The C<Tk> adaptor works relatively well. The fact that it crashes with
950	more than 2000 watchers is a big setback, however, as correctness takes	1039	more than 2000 watchers is a big setback, however, as correctness takes
951	precedence over speed. Nevertheless, its performance is surprising, as the	1040	precedence over speed. Nevertheless, its performance is surprising, as the
952	file descriptor is dup()ed for each watcher. This shows that the dup()	1041	file descriptor is dup()ed for each watcher. This shows that the dup()
953	employed by some adaptors is not a big performance issue (it does incur a	1042	employed by some adaptors is not a big performance issue (it does incur a
954	hidden memory cost inside the kernel, though, that is not reflected in the	1043	hidden memory cost inside the kernel which is not reflected in the figures
955	figures above).	1044	above).
956		1045
957	C<POE>, regardless of underlying event loop (wether using its pure perl	1046	C<POE>, regardless of underlying event loop (whether using its pure
958	select-based backend or the Event module) shows abysmal performance and	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
959	memory usage: Watchers use almost 30 times as much memory as EV watchers,	1049	and memory usage: Watchers use almost 30 times as much memory as
960	and 10 times as much memory as both Event or EV via AnyEvent. Watcher	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
961	invocation is almost 700 times slower than with AnyEvent's pure perl	1052	invocation speed is almost 900 times slower than with AnyEvent's pure perl
962	implementation. The design of the POE adaptor class in AnyEvent can not	1053	implementation. The design of the POE adaptor class in AnyEvent can not
963	really account for this, as session creation overhead is small compared	1054	really account for this, as session creation overhead is small compared
964	to execution of the state machine, which is coded pretty optimally within	1055	to execution of the state machine, which is coded pretty optimally within
965	L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow.	1056	L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow.
966		1057
967	=head2 Summary	1058	=head3 Summary
968		1059
		1060	=over 4
		1061
969	Using EV through AnyEvent is faster than any other event loop, but most	1062	=item * Using EV through AnyEvent is faster than any other event loop
970	event loops have acceptable performance with or without AnyEvent.	1063	(even when used without AnyEvent), but most event loops have acceptable
		1064	performance with or without AnyEvent.
971		1065
972	The overhead AnyEvent adds is usually much smaller than the overhead of	1066	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
973	the actual event loop, only with extremely fast event loops such as the EV	1067	the actual event loop, only with extremely fast event loops such as EV
974	adds AnyEvent significant overhead.	1068	adds AnyEvent significant overhead.
975		1069
976	And you should simply avoid POE like the plague if you want performance or	1070	=item * You should avoid POE like the plague if you want performance or
977	reasonable memory usage.	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
978		1203
979		1204
980	=head1 FORK	1205	=head1 FORK
981		1206
982	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

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Comparing AnyEvent/lib/AnyEvent.pm (file contents): Revision 1.76 by root, Fri Apr 25 08:41:38 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 1.76 by root, Fri Apr 25 08:41:38 2008 UTC vs.
Revision 1.100 by elmex, Sun Apr 27 19:15:43 2008 UTC