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

Comparing Coro/Coro.pm (file contents):
Revision 1.250 by root, Wed Dec 17 04:57:07 2008 UTC vs.
Revision 1.282 by root, Sun Dec 26 16:23:51 2010 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 = 5.13;	86	our $VERSION = 5.25;
86		87
87	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);	88	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub rouse_cb rouse_wait);
88	our %EXPORT_TAGS = (	89	our %EXPORT_TAGS = (
89	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],	90	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
90	);	91	);
91	our @EXPORT_OK = (@{$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	# \|\|= because other modules could have provided their own by now
158	require Carp;	144	$idle \|\|= new Coro sub {
159	Carp::croak ("FATAL: deadlock detected");	145	require Coro::Debug;
		146	die "FATAL: deadlock detected.\n"
		147	. Coro::Debug::ps_listing ();
160	};	148	};
161		149
162	# this coro is necessary because a coro	150	# this coro is necessary because a coro
163	# cannot destroy itself.	151	# cannot destroy itself.
164	our @destroy;	152	our @destroy;
…		…
206	Example: Create a new coro that just prints its arguments.	194	Example: Create a new coro that just prints its arguments.
207		195
208	async {	196	async {
209	print "@_\n";	197	print "@_\n";
210	} 1,2,3,4;	198	} 1,2,3,4;
211
212	=cut
213
214	sub async(&@) {
215	my $coro = new Coro @_;
216	$coro->ready;
217	$coro
218	}
219		199
220	=item async_pool { ... } [@args...]	200	=item async_pool { ... } [@args...]
221		201
222	Similar to C<async>, but uses a coro pool, so you should not call	202	Similar to C<async>, but uses a coro pool, so you should not call
223	terminate or join on it (although you are allowed to), and you get a	203	terminate or join on it (although you are allowed to), and you get a
…		…
280	=item schedule	260	=item schedule
281		261
282	Calls the scheduler. The scheduler will find the next coro that is	262	Calls the scheduler. The scheduler will find the next coro that is
283	to be run from the ready queue and switches to it. The next coro	263	to be run from the ready queue and switches to it. The next coro
284	to be run is simply the one with the highest priority that is longest	264	to be run is simply the one with the highest priority that is longest
285	in its ready queue. If there is no coro ready, it will clal the	265	in its ready queue. If there is no coro ready, it will call the
286	C<$Coro::idle> hook.	266	C<$Coro::idle> hook.
287		267
288	Please note that the current coro will I<not> be put into the ready	268	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	269	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 >>,	270	again unless something else (e.g. an event handler) calls C<< ->ready >>,
…		…
338		318
339	These functions implement the same concept as C<dynamic-wind> in scheme	319	These functions implement the same concept as C<dynamic-wind> in scheme
340	does, and are useful when you want to localise some resource to a specific	320	does, and are useful when you want to localise some resource to a specific
341	coro.	321	coro.
342		322
343	They slow down coro switching considerably for coros that use	323	They slow down thread switching considerably for coros that use them
344	them (But coro switching is still reasonably fast if the handlers are	324	(about 40% for a BLOCK with a single assignment, so thread switching is
345	fast).	325	still reasonably fast if the handlers are fast).
346		326
347	These functions are best understood by an example: The following function	327	These functions are best understood by an example: The following function
348	will change the current timezone to "Antarctica/South_Pole", which	328	will change the current timezone to "Antarctica/South_Pole", which
349	requires a call to C<tzset>, but by using C<on_enter> and C<on_leave>,	329	requires a call to C<tzset>, but by using C<on_enter> and C<on_leave>,
350	which remember/change the current timezone and restore the previous	330	which remember/change the current timezone and restore the previous
351	value, respectively, the timezone is only changes for the coro that	331	value, respectively, the timezone is only changed for the coro that
352	installed those handlers.	332	installed those handlers.
353		333
354	use POSIX qw(tzset);	334	use POSIX qw(tzset);
355		335
356	async {	336	async {
…		…
373	};	353	};
374		354
375	This can be used to localise about any resource (locale, uid, current	355	This can be used to localise about any resource (locale, uid, current
376	working directory etc.) to a block, despite the existance of other	356	working directory etc.) to a block, despite the existance of other
377	coros.	357	coros.
		358
		359	Another interesting example implements time-sliced multitasking using
		360	interval timers (this could obviously be optimised, but does the job):
		361
		362	# "timeslice" the given block
		363	sub timeslice(&) {
		364	use Time::HiRes ();
		365
		366	Coro::on_enter {
		367	# on entering the thread, we set an VTALRM handler to cede
		368	$SIG{VTALRM} = sub { cede };
		369	# and then start the interval timer
		370	Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0.01, 0.01;
		371	};
		372	Coro::on_leave {
		373	# on leaving the thread, we stop the interval timer again
		374	Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0, 0;
		375	};
		376
		377	&{+shift};
		378	}
		379
		380	# use like this:
		381	timeslice {
		382	# The following is an endless loop that would normally
		383	# monopolise the process. Since it runs in a timesliced
		384	# environment, it will regularly cede to other threads.
		385	while () { }
		386	};
		387
378		388
379	=item killall	389	=item killall
380		390
381	Kills/terminates/cancels all coros except the currently running one.	391	Kills/terminates/cancels all coros except the currently running one.
382		392
…		…
603	Sets (or gets in case the argument is missing) the description for this	613	Sets (or gets in case the argument is missing) the description for this
604	coro. This is just a free-form string you can associate with a	614	coro. This is just a free-form string you can associate with a
605	coro.	615	coro.
606		616
607	This method simply sets the C<< $coro->{desc} >> member to the given	617	This method simply sets the C<< $coro->{desc} >> member to the given
608	string. You can modify this member directly if you wish.	618	string. You can modify this member directly if you wish, and in fact, this
		619	is often preferred to indicate major processing states that cna then be
		620	seen for example in a L<Coro::Debug> session:
		621
		622	sub my_long_function {
		623	local $Coro::current->{desc} = "now in my_long_function";
		624	...
		625	$Coro::current->{desc} = "my_long_function: phase 1";
		626	...
		627	$Coro::current->{desc} = "my_long_function: phase 2";
		628	...
		629	}
609		630
610	=cut	631	=cut
611		632
612	sub desc {	633	sub desc {
613	my $old = $_[0]{desc};	634	my $old = $_[0]{desc};
…		…
650	returning a new coderef. Unblocking means that calling the new coderef	671	returning a new coderef. Unblocking means that calling the new coderef
651	will return immediately without blocking, returning nothing, while the	672	will return immediately without blocking, returning nothing, while the
652	original code ref will be called (with parameters) from within another	673	original code ref will be called (with parameters) from within another
653	coro.	674	coro.
654		675
655	The reason this function exists is that many event libraries (such as the	676	The reason this function exists is that many event libraries (such as
656	venerable L<Event\|Event> module) are not thread-safe (a weaker form	677	the venerable L<Event\|Event> module) are not thread-safe (a weaker form
657	of reentrancy). This means you must not block within event callbacks,	678	of reentrancy). This means you must not block within event callbacks,
658	otherwise you might suffer from crashes or worse. The only event library	679	otherwise you might suffer from crashes or worse. The only event library
659	currently known that is safe to use without C<unblock_sub> is L<EV>.	680	currently known that is safe to use without C<unblock_sub> is L<EV> (but
		681	you might still run into deadlocks if all event loops are blocked).
		682
		683	Coro will try to catch you when you block in the event loop
		684	("FATAL:$Coro::IDLE blocked itself"), but this is just best effort and
		685	only works when you do not run your own event loop.
660		686
661	This function allows your callbacks to block by executing them in another	687	This function allows your callbacks to block by executing them in another
662	coro where it is safe to block. One example where blocking is handy	688	coro where it is safe to block. One example where blocking is handy
663	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to	689	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
664	disk, for example.	690	disk, for example.
…		…
706	unshift @unblock_queue, [$cb, @_];	732	unshift @unblock_queue, [$cb, @_];
707	$unblock_scheduler->ready;	733	$unblock_scheduler->ready;
708	}	734	}
709	}	735	}
710		736
711	=item $cb = Coro::rouse_cb	737	=item $cb = rouse_cb
712		738
713	Create and return a "rouse callback". That's a code reference that,	739	Create and return a "rouse callback". That's a code reference that,
714	when called, will remember a copy of its arguments and notify the owner	740	when called, will remember a copy of its arguments and notify the owner
715	coro of the callback.	741	coro of the callback.
716		742
717	See the next function.	743	See the next function.
718		744
719	=item @args = Coro::rouse_wait [$cb]	745	=item @args = rouse_wait [$cb]
720		746
721	Wait for the specified rouse callback (or the last one that was created in	747	Wait for the specified rouse callback (or the last one that was created in
722	this coro).	748	this coro).
723		749
724	As soon as the callback is invoked (or when the callback was invoked	750	As soon as the callback is invoked (or when the callback was invoked
725	before C<rouse_wait>), it will return the arguments originally passed to	751	before C<rouse_wait>), it will return the arguments originally passed to
726	the rouse callback.	752	the rouse callback. In scalar context, that means you get the I<last>
		753	argument, just as if C<rouse_wait> had a C<return ($a1, $a2, $a3...)>
		754	statement at the end.
727		755
728	See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.	756	See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.
729		757
730	=back	758	=back
731		759
…		…
819	the windows process emulation enabled under unix roughly halves perl	847	the windows process emulation enabled under unix roughly halves perl
820	performance, even when not used.	848	performance, even when not used.
821		849
822	=item coro switching is not signal safe	850	=item coro switching is not signal safe
823		851
824	You must not switch to another coro from within a signal handler	852	You must not switch to another coro from within a signal handler (only
825	(only relevant with %SIG - most event libraries provide safe signals).	853	relevant with %SIG - most event libraries provide safe signals), I<unless>
		854	you are sure you are not interrupting a Coro function.
826		855
827	That means you I<MUST NOT> call any function that might "block" the	856	That means you I<MUST NOT> call any function that might "block" the
828	current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or	857	current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
829	anything that calls those. Everything else, including calling C<ready>,	858	anything that calls those. Everything else, including calling C<ready>,
830	works.	859	works.
831		860
832	=back	861	=back
833		862
834		863
		864	=head1 WINDOWS PROCESS EMULATION
		865
		866	A great many people seem to be confused about ithreads (for example, Chip
		867	Salzenberg called me unintelligent, incapable, stupid and gullible,
		868	while in the same mail making rather confused statements about perl
		869	ithreads (for example, that memory or files would be shared), showing his
		870	lack of understanding of this area - if it is hard to understand for Chip,
		871	it is probably not obvious to everybody).
		872
		873	What follows is an ultra-condensed version of my talk about threads in
		874	scripting languages given on the perl workshop 2009:
		875
		876	The so-called "ithreads" were originally implemented for two reasons:
		877	first, to (badly) emulate unix processes on native win32 perls, and
		878	secondly, to replace the older, real thread model ("5.005-threads").
		879
		880	It does that by using threads instead of OS processes. The difference
		881	between processes and threads is that threads share memory (and other
		882	state, such as files) between threads within a single process, while
		883	processes do not share anything (at least not semantically). That
		884	means that modifications done by one thread are seen by others, while
		885	modifications by one process are not seen by other processes.
		886
		887	The "ithreads" work exactly like that: when creating a new ithreads
		888	process, all state is copied (memory is copied physically, files and code
		889	is copied logically). Afterwards, it isolates all modifications. On UNIX,
		890	the same behaviour can be achieved by using operating system processes,
		891	except that UNIX typically uses hardware built into the system to do this
		892	efficiently, while the windows process emulation emulates this hardware in
		893	software (rather efficiently, but of course it is still much slower than
		894	dedicated hardware).
		895
		896	As mentioned before, loading code, modifying code, modifying data
		897	structures and so on is only visible in the ithreads process doing the
		898	modification, not in other ithread processes within the same OS process.
		899
		900	This is why "ithreads" do not implement threads for perl at all, only
		901	processes. What makes it so bad is that on non-windows platforms, you can
		902	actually take advantage of custom hardware for this purpose (as evidenced
		903	by the forks module, which gives you the (i-) threads API, just much
		904	faster).
		905
		906	Sharing data is in the i-threads model is done by transfering data
		907	structures between threads using copying semantics, which is very slow -
		908	shared data simply does not exist. Benchmarks using i-threads which are
		909	communication-intensive show extremely bad behaviour with i-threads (in
		910	fact, so bad that Coro, which cannot take direct advantage of multiple
		911	CPUs, is often orders of magnitude faster because it shares data using
		912	real threads, refer to my talk for details).
		913
		914	As summary, i-threads use threads to implement processes, while
		915	the compatible forks module uses processes to emulate, uhm,
		916	processes. I-threads slow down every perl program when enabled, and
		917	outside of windows, serve no (or little) practical purpose, but
		918	disadvantages every single-threaded Perl program.
		919
		920	This is the reason that I try to avoid the name "ithreads", as it is
		921	misleading as it implies that it implements some kind of thread model for
		922	perl, and prefer the name "windows process emulation", which describes the
		923	actual use and behaviour of it much better.
		924
835	=head1 SEE ALSO	925	=head1 SEE ALSO
836		926
837	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.	927	Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
838		928
839	Debugging: L<Coro::Debug>.	929	Debugging: L<Coro::Debug>.

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Comparing Coro/Coro.pm (file contents): Revision 1.250 by root, Wed Dec 17 04:57:07 2008 UTC vs. Revision 1.282 by root, Sun Dec 26 16:23:51 2010 UTC

Diff Legend

Comparing Coro/Coro.pm (file contents):
Revision 1.250 by root, Wed Dec 17 04:57:07 2008 UTC vs.
Revision 1.282 by root, Sun Dec 26 16:23:51 2010 UTC