[ViewVC] Diff of: cvs/Coro/Coro.pm

Comparing Coro/Coro.pm (file contents):
Revision 1.256 by root, Wed Jun 17 21:38:23 2009 UTC vs.
Revision 1.272 by root, Tue Nov 24 06:13:01 2009 UTC

…		…
40	points in your program, so locking and parallel access are rarely an	40	points in your program, so locking and parallel access are rarely an
41	issue, making thread programming much safer and easier than using other	41	issue, making thread programming much safer and easier than using other
42	thread models.	42	thread models.
43		43
44	Unlike the so-called "Perl threads" (which are not actually real threads	44	Unlike the so-called "Perl threads" (which are not actually real threads
45	but only the windows process emulation ported to unix, and as such act	45	but only the windows process emulation (see section of same name for more
46	as processes), Coro provides a full shared address space, which makes	46	details) ported to unix, and as such act as processes), Coro provides
47	communication between threads very easy. And Coro's threads are fast,	47	a full shared address space, which makes communication between threads
48	too: disabling the Windows process emulation code in your perl and using	48	very easy. And Coro's threads are fast, too: disabling the Windows
49	Coro can easily result in a two to four times speed increase for your	49	process emulation code in your perl and using Coro can easily result in
50	programs. A parallel matrix multiplication benchmark runs over 300 times	50	a two to four times speed increase for your programs. A parallel matrix
51	faster on a single core than perl's pseudo-threads on a quad core using	51	multiplication benchmark runs over 300 times faster on a single core than
52	all four cores.	52	perl's pseudo-threads on a quad core using all four cores.
53		53
54	Coro achieves that by supporting multiple running interpreters that share	54	Coro achieves that by supporting multiple running interpreters that share
55	data, which is especially useful to code pseudo-parallel processes and	55	data, which is especially useful to code pseudo-parallel processes and
56	for event-based programming, such as multiple HTTP-GET requests running	56	for event-based programming, such as multiple HTTP-GET requests running
57	concurrently. See L<Coro::AnyEvent> to learn more on how to integrate Coro	57	concurrently. See L<Coro::AnyEvent> to learn more on how to integrate Coro
…		…
67		67
68	=cut	68	=cut
69		69
70	package Coro;	70	package Coro;
71		71
72	use strict qw(vars subs);	72	use common::sense;
73	no warnings "uninitialized";	73
		74	use Carp ();
74		75
75	use Guard ();	76	use Guard ();
76		77
77	use Coro::State;	78	use Coro::State;
78		79
…		…
80		81
81	our $idle; # idle handler	82	our $idle; # idle handler
82	our $main; # main coro	83	our $main; # main coro
83	our $current; # current coro	84	our $current; # current coro
84		85
85	our $VERSION = 5.132;	86	our $VERSION = 5.2;
86		87
87	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);	88	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub rouse_cb rouse_wait);
88	our %EXPORT_TAGS = (	89	our %EXPORT_TAGS = (
89	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],	90	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
90	);	91	);
91	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));	92	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
92		93
…		…
123		124
124	This variable is mainly useful to integrate Coro into event loops. It is	125	This variable is mainly useful to integrate Coro into event loops. It is
125	usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is	126	usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is
126	pretty low-level functionality.	127	pretty low-level functionality.
127		128
128	This variable stores either a Coro object or a callback.	129	This variable stores a Coro object that is put into the ready queue when
		130	there are no other ready threads (without invoking any ready hooks).
129		131
130	If it is a callback, the it is called whenever the scheduler finds no	132	The default implementation dies with "FATAL: deadlock detected.", followed
131	ready coros to run. The default implementation prints "FATAL:	133	by a thread listing, because the program has no other way to continue.
132	deadlock detected" and exits, because the program has no other way to
133	continue.
134
135	If it is a coro object, then this object will be readied (without
136	invoking any ready hooks, however) when the scheduler finds no other ready
137	coros to run.
138		134
139	This hook is overwritten by modules such as C<Coro::EV> and	135	This hook is overwritten by modules such as C<Coro::EV> and
140	C<Coro::AnyEvent> to wait on an external event that hopefully wake up a	136	C<Coro::AnyEvent> to wait on an external event that hopefully wake up a
141	coro so the scheduler can run it.	137	coro so the scheduler can run it.
142		138
143	Note that the callback I<must not>, under any circumstances, block
144	the current coro. Normally, this is achieved by having an "idle
145	coro" that calls the event loop and then blocks again, and then
146	readying that coro in the idle handler, or by simply placing the idle
147	coro in this variable.
148
149	See L<Coro::Event> or L<Coro::AnyEvent> for examples of using this	139	See L<Coro::EV> or L<Coro::AnyEvent> for examples of using this technique.
150	technique.
151		140
152	Please note that if your callback recursively invokes perl (e.g. for event
153	handlers), then it must be prepared to be called recursively itself.
154
155	=cut	141	=cut
156		142
157	$idle = sub {	143	$idle = new Coro sub {
158	require Carp;	144	require Coro::Debug;
159	Carp::croak ("FATAL: deadlock detected");	145	die "FATAL: deadlock detected.\n"
		146	. Coro::Debug::ps_listing ();
160	};	147	};
161		148
162	# this coro is necessary because a coro	149	# this coro is necessary because a coro
163	# cannot destroy itself.	150	# cannot destroy itself.
164	our @destroy;	151	our @destroy;
…		…
206	Example: Create a new coro that just prints its arguments.	193	Example: Create a new coro that just prints its arguments.
207		194
208	async {	195	async {
209	print "@_\n";	196	print "@_\n";
210	} 1,2,3,4;	197	} 1,2,3,4;
211
212	=cut
213
214	sub async(&@) {
215	my $coro = new Coro @_;
216	$coro->ready;
217	$coro
218	}
219		198
220	=item async_pool { ... } [@args...]	199	=item async_pool { ... } [@args...]
221		200
222	Similar to C<async>, but uses a coro pool, so you should not call	201	Similar to C<async>, but uses a coro pool, so you should not call
223	terminate or join on it (although you are allowed to), and you get a	202	terminate or join on it (although you are allowed to), and you get a
…		…
280	=item schedule	259	=item schedule
281		260
282	Calls the scheduler. The scheduler will find the next coro that is	261	Calls the scheduler. The scheduler will find the next coro that is
283	to be run from the ready queue and switches to it. The next coro	262	to be run from the ready queue and switches to it. The next coro
284	to be run is simply the one with the highest priority that is longest	263	to be run is simply the one with the highest priority that is longest
285	in its ready queue. If there is no coro ready, it will clal the	264	in its ready queue. If there is no coro ready, it will call the
286	C<$Coro::idle> hook.	265	C<$Coro::idle> hook.
287		266
288	Please note that the current coro will I<not> be put into the ready	267	Please note that the current coro will I<not> be put into the ready
289	queue, so calling this function usually means you will never be called	268	queue, so calling this function usually means you will never be called
290	again unless something else (e.g. an event handler) calls C<< ->ready >>,	269	again unless something else (e.g. an event handler) calls C<< ->ready >>,
…		…
736	unshift @unblock_queue, [$cb, @_];	715	unshift @unblock_queue, [$cb, @_];
737	$unblock_scheduler->ready;	716	$unblock_scheduler->ready;
738	}	717	}
739	}	718	}
740		719
741	=item $cb = Coro::rouse_cb	720	=item $cb = rouse_cb
742		721
743	Create and return a "rouse callback". That's a code reference that,	722	Create and return a "rouse callback". That's a code reference that,
744	when called, will remember a copy of its arguments and notify the owner	723	when called, will remember a copy of its arguments and notify the owner
745	coro of the callback.	724	coro of the callback.
746		725
747	See the next function.	726	See the next function.
748		727
749	=item @args = Coro::rouse_wait [$cb]	728	=item @args = rouse_wait [$cb]
750		729
751	Wait for the specified rouse callback (or the last one that was created in	730	Wait for the specified rouse callback (or the last one that was created in
752	this coro).	731	this coro).
753		732
754	As soon as the callback is invoked (or when the callback was invoked	733	As soon as the callback is invoked (or when the callback was invoked
755	before C<rouse_wait>), it will return the arguments originally passed to	734	before C<rouse_wait>), it will return the arguments originally passed to
756	the rouse callback.	735	the rouse callback. In scalar context, that means you get the I<last>
		736	argument, just as if C<rouse_wait> had a C<return ($a1, $a2, $a3...)>
		737	statement at the end.
757		738
758	See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.	739	See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.
759		740
760	=back	741	=back
761		742
…		…
849	the windows process emulation enabled under unix roughly halves perl	830	the windows process emulation enabled under unix roughly halves perl
850	performance, even when not used.	831	performance, even when not used.
851		832
852	=item coro switching is not signal safe	833	=item coro switching is not signal safe
853		834
854	You must not switch to another coro from within a signal handler	835	You must not switch to another coro from within a signal handler (only
855	(only relevant with %SIG - most event libraries provide safe signals).	836	relevant with %SIG - most event libraries provide safe signals), I<unless>
		837	you are sure you are not interrupting a Coro function.
856		838
857	That means you I<MUST NOT> call any function that might "block" the	839	That means you I<MUST NOT> call any function that might "block" the
858	current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or	840	current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
859	anything that calls those. Everything else, including calling C<ready>,	841	anything that calls those. Everything else, including calling C<ready>,
860	works.	842	works.
861		843
862	=back	844	=back
863		845
864		846
		847	=head1 WINDOWS PROCESS EMULATION
		848
		849	A great many people seem to be confused about ithreads (for example, Chip
		850	Salzenberg called me unintelligent, incapable, stupid and gullible,
		851	while in the same mail making rather confused statements about perl
		852	ithreads (for example, that memory or files would be shared), showing his
		853	lack of understanding of this area - if it is hard to understand for Chip,
		854	it is probably not obvious to everybody).
		855
		856	What follows is an ultra-condensed version of my talk about threads in
		857	scripting languages given onthe perl workshop 2009:
		858
		859	The so-called "ithreads" were originally implemented for two reasons:
		860	first, to (badly) emulate unix processes on native win32 perls, and
		861	secondly, to replace the older, real thread model ("5.005-threads").
		862
		863	It does that by using threads instead of OS processes. The difference
		864	between processes and threads is that threads share memory (and other
		865	state, such as files) between threads within a single process, while
		866	processes do not share anything (at least not semantically). That
		867	means that modifications done by one thread are seen by others, while
		868	modifications by one process are not seen by other processes.
		869
		870	The "ithreads" work exactly like that: when creating a new ithreads
		871	process, all state is copied (memory is copied physically, files and code
		872	is copied logically). Afterwards, it isolates all modifications. On UNIX,
		873	the same behaviour can be achieved by using operating system processes,
		874	except that UNIX typically uses hardware built into the system to do this
		875	efficiently, while the windows process emulation emulates this hardware in
		876	software (rather efficiently, but of course it is still much slower than
		877	dedicated hardware).
		878
		879	As mentioned before, loading code, modifying code, modifying data
		880	structures and so on is only visible in the ithreads process doing the
		881	modification, not in other ithread processes within the same OS process.
		882
		883	This is why "ithreads" do not implement threads for perl at all, only
		884	processes. What makes it so bad is that on non-windows platforms, you can
		885	actually take advantage of custom hardware for this purpose (as evidenced
		886	by the forks module, which gives you the (i-) threads API, just much
		887	faster).
		888
		889	Sharing data is in the i-threads model is done by transfering data
		890	structures between threads using copying semantics, which is very slow -
		891	shared data simply does not exist. Benchmarks using i-threads which are
		892	communication-intensive show extremely bad behaviour with i-threads (in
		893	fact, so bad that Coro, which cannot take direct advantage of multiple
		894	CPUs, is often orders of magnitude faster because it shares data using
		895	real threads, refer to my talk for details).
		896
		897	As summary, i-threads use threads to implement processes, while
		898	the compatible forks module uses processes to emulate, uhm,
		899	processes. I-threads slow down every perl program when enabled, and
		900	outside of windows, serve no (or little) practical purpose, but
		901	disadvantages every single-threaded Perl program.
		902
		903	This is the reason that I try to avoid the name "ithreads", as it is
		904	misleading as it implies that it implements some kind of thread model for
		905	perl, and prefer the name "windows process emulation", which describes the
		906	actual use and behaviour of it much better.
		907
865	=head1 SEE ALSO	908	=head1 SEE ALSO
866		909
867	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.	910	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
868		911
869	Debugging: L<Coro::Debug>.	912	Debugging: L<Coro::Debug>.

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Comparing Coro/Coro.pm (file contents): Revision 1.256 by root, Wed Jun 17 21:38:23 2009 UTC vs. Revision 1.272 by root, Tue Nov 24 06:13:01 2009 UTC

Diff Legend

Comparing Coro/Coro.pm (file contents):
Revision 1.256 by root, Wed Jun 17 21:38:23 2009 UTC vs.
Revision 1.272 by root, Tue Nov 24 06:13:01 2009 UTC