… | |
… | |
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 = 5.14; |
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 |
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|
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 |
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133 | continue. |
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134 | |
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135 | If it is a coro object, then this object will be readied (without |
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136 | invoking any ready hooks, however) when the scheduler finds no other ready |
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137 | coros to run. |
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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 |
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144 | the current coro. Normally, this is achieved by having an "idle |
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145 | coro" that calls the event loop and then blocks again, and then |
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146 | readying that coro in the idle handler, or by simply placing the idle |
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147 | coro in this variable. |
|
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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 |
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153 | handlers), then it must be prepared to be called recursively itself. |
|
|
154 | |
|
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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 | |
|
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212 | =cut |
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|
213 | |
|
|
214 | sub async(&@) { |
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215 | my $coro = new Coro @_; |
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216 | $coro->ready; |
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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 >>, |
… | |
… | |
633 | 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 |
634 | 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 |
635 | coro. |
615 | coro. |
636 | |
616 | |
637 | 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 |
638 | 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 | } |
639 | |
630 | |
640 | =cut |
631 | =cut |
641 | |
632 | |
642 | sub desc { |
633 | sub desc { |
643 | my $old = $_[0]{desc}; |
634 | my $old = $_[0]{desc}; |
… | |
… | |
685 | The reason this function exists is that many event libraries (such as the |
676 | The reason this function exists is that many event libraries (such as the |
686 | venerable L<Event|Event> module) are not thread-safe (a weaker form |
677 | venerable L<Event|Event> module) are not thread-safe (a weaker form |
687 | of reentrancy). This means you must not block within event callbacks, |
678 | of reentrancy). This means you must not block within event callbacks, |
688 | otherwise you might suffer from crashes or worse. The only event library |
679 | otherwise you might suffer from crashes or worse. The only event library |
689 | currently known that is safe to use without C<unblock_sub> is L<EV>. |
680 | currently known that is safe to use without C<unblock_sub> is L<EV>. |
|
|
681 | |
|
|
682 | Coro will try to catch you when you block in the event loop |
|
|
683 | ("FATAL:$Coro::IDLE blocked itself"), but this is just best effort and |
|
|
684 | only works when you do not run your own event loop. |
690 | |
685 | |
691 | This function allows your callbacks to block by executing them in another |
686 | This function allows your callbacks to block by executing them in another |
692 | coro where it is safe to block. One example where blocking is handy |
687 | coro where it is safe to block. One example where blocking is handy |
693 | is when you use the L<Coro::AIO|Coro::AIO> functions to save results to |
688 | is when you use the L<Coro::AIO|Coro::AIO> functions to save results to |
694 | disk, for example. |
689 | disk, for example. |
… | |
… | |
736 | unshift @unblock_queue, [$cb, @_]; |
731 | unshift @unblock_queue, [$cb, @_]; |
737 | $unblock_scheduler->ready; |
732 | $unblock_scheduler->ready; |
738 | } |
733 | } |
739 | } |
734 | } |
740 | |
735 | |
741 | =item $cb = Coro::rouse_cb |
736 | =item $cb = rouse_cb |
742 | |
737 | |
743 | Create and return a "rouse callback". That's a code reference that, |
738 | Create and return a "rouse callback". That's a code reference that, |
744 | when called, will remember a copy of its arguments and notify the owner |
739 | when called, will remember a copy of its arguments and notify the owner |
745 | coro of the callback. |
740 | coro of the callback. |
746 | |
741 | |
747 | See the next function. |
742 | See the next function. |
748 | |
743 | |
749 | =item @args = Coro::rouse_wait [$cb] |
744 | =item @args = rouse_wait [$cb] |
750 | |
745 | |
751 | Wait for the specified rouse callback (or the last one that was created in |
746 | Wait for the specified rouse callback (or the last one that was created in |
752 | this coro). |
747 | this coro). |
753 | |
748 | |
754 | As soon as the callback is invoked (or when the callback was invoked |
749 | As soon as the callback is invoked (or when the callback was invoked |
755 | before C<rouse_wait>), it will return the arguments originally passed to |
750 | before C<rouse_wait>), it will return the arguments originally passed to |
756 | the rouse callback. |
751 | the rouse callback. In scalar context, that means you get the I<last> |
|
|
752 | argument, just as if C<rouse_wait> had a C<return ($a1, $a2, $a3...)> |
|
|
753 | statement at the end. |
757 | |
754 | |
758 | See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example. |
755 | See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example. |
759 | |
756 | |
760 | =back |
757 | =back |
761 | |
758 | |
… | |
… | |
849 | the windows process emulation enabled under unix roughly halves perl |
846 | the windows process emulation enabled under unix roughly halves perl |
850 | performance, even when not used. |
847 | performance, even when not used. |
851 | |
848 | |
852 | =item coro switching is not signal safe |
849 | =item coro switching is not signal safe |
853 | |
850 | |
854 | You must not switch to another coro from within a signal handler |
851 | You must not switch to another coro from within a signal handler (only |
855 | (only relevant with %SIG - most event libraries provide safe signals). |
852 | relevant with %SIG - most event libraries provide safe signals), I<unless> |
|
|
853 | you are sure you are not interrupting a Coro function. |
856 | |
854 | |
857 | That means you I<MUST NOT> call any function that might "block" the |
855 | 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 |
856 | current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or |
859 | anything that calls those. Everything else, including calling C<ready>, |
857 | anything that calls those. Everything else, including calling C<ready>, |
860 | works. |
858 | works. |
861 | |
859 | |
862 | =back |
860 | =back |
863 | |
861 | |
864 | |
862 | |
|
|
863 | =head1 WINDOWS PROCESS EMULATION |
|
|
864 | |
|
|
865 | A great many people seem to be confused about ithreads (for example, Chip |
|
|
866 | Salzenberg called me unintelligent, incapable, stupid and gullible, |
|
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867 | while in the same mail making rather confused statements about perl |
|
|
868 | ithreads (for example, that memory or files would be shared), showing his |
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869 | lack of understanding of this area - if it is hard to understand for Chip, |
|
|
870 | it is probably not obvious to everybody). |
|
|
871 | |
|
|
872 | What follows is an ultra-condensed version of my talk about threads in |
|
|
873 | scripting languages given on the perl workshop 2009: |
|
|
874 | |
|
|
875 | The so-called "ithreads" were originally implemented for two reasons: |
|
|
876 | first, to (badly) emulate unix processes on native win32 perls, and |
|
|
877 | secondly, to replace the older, real thread model ("5.005-threads"). |
|
|
878 | |
|
|
879 | It does that by using threads instead of OS processes. The difference |
|
|
880 | between processes and threads is that threads share memory (and other |
|
|
881 | state, such as files) between threads within a single process, while |
|
|
882 | processes do not share anything (at least not semantically). That |
|
|
883 | means that modifications done by one thread are seen by others, while |
|
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884 | modifications by one process are not seen by other processes. |
|
|
885 | |
|
|
886 | The "ithreads" work exactly like that: when creating a new ithreads |
|
|
887 | process, all state is copied (memory is copied physically, files and code |
|
|
888 | is copied logically). Afterwards, it isolates all modifications. On UNIX, |
|
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889 | the same behaviour can be achieved by using operating system processes, |
|
|
890 | except that UNIX typically uses hardware built into the system to do this |
|
|
891 | efficiently, while the windows process emulation emulates this hardware in |
|
|
892 | software (rather efficiently, but of course it is still much slower than |
|
|
893 | dedicated hardware). |
|
|
894 | |
|
|
895 | As mentioned before, loading code, modifying code, modifying data |
|
|
896 | structures and so on is only visible in the ithreads process doing the |
|
|
897 | modification, not in other ithread processes within the same OS process. |
|
|
898 | |
|
|
899 | This is why "ithreads" do not implement threads for perl at all, only |
|
|
900 | processes. What makes it so bad is that on non-windows platforms, you can |
|
|
901 | actually take advantage of custom hardware for this purpose (as evidenced |
|
|
902 | by the forks module, which gives you the (i-) threads API, just much |
|
|
903 | faster). |
|
|
904 | |
|
|
905 | Sharing data is in the i-threads model is done by transfering data |
|
|
906 | structures between threads using copying semantics, which is very slow - |
|
|
907 | shared data simply does not exist. Benchmarks using i-threads which are |
|
|
908 | communication-intensive show extremely bad behaviour with i-threads (in |
|
|
909 | fact, so bad that Coro, which cannot take direct advantage of multiple |
|
|
910 | CPUs, is often orders of magnitude faster because it shares data using |
|
|
911 | real threads, refer to my talk for details). |
|
|
912 | |
|
|
913 | As summary, i-threads *use* threads to implement processes, while |
|
|
914 | the compatible forks module *uses* processes to emulate, uhm, |
|
|
915 | processes. I-threads slow down every perl program when enabled, and |
|
|
916 | outside of windows, serve no (or little) practical purpose, but |
|
|
917 | disadvantages every single-threaded Perl program. |
|
|
918 | |
|
|
919 | This is the reason that I try to avoid the name "ithreads", as it is |
|
|
920 | misleading as it implies that it implements some kind of thread model for |
|
|
921 | perl, and prefer the name "windows process emulation", which describes the |
|
|
922 | actual use and behaviour of it much better. |
|
|
923 | |
865 | =head1 SEE ALSO |
924 | =head1 SEE ALSO |
866 | |
925 | |
867 | Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>. |
926 | Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>. |
868 | |
927 | |
869 | Debugging: L<Coro::Debug>. |
928 | Debugging: L<Coro::Debug>. |