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Comparing AnyEvent-Fork/Fork.pm (file contents):
Revision 1.33 by root, Sat Apr 6 09:34:11 2013 UTC vs.
Revision 1.37 by root, Sat Apr 6 20:06:39 2013 UTC

591 591
592If you want to execute some code (that isn't in a module) to take over the 592If you want to execute some code (that isn't in a module) to take over the
593process, you should compile a function via C<eval> first, and then call 593process, you should compile a function via C<eval> first, and then call
594it via C<run>. This also gives you access to any arguments passed via the 594it via C<run>. This also gives you access to any arguments passed via the
595C<send_xxx> methods, such as file handles. See the L<use AnyEvent::Fork as 595C<send_xxx> methods, such as file handles. See the L<use AnyEvent::Fork as
596a faster fork+exec> example. 596a faster fork+exec> example to see it in action.
597 597
598Returns the process object for easy chaining of method calls. 598Returns the process object for easy chaining of method calls.
599 599
600=cut 600=cut
601 601
627=item $proc = $proc->send_fh ($handle, ...) 627=item $proc = $proc->send_fh ($handle, ...)
628 628
629Send one or more file handles (I<not> file descriptors) to the process, 629Send one or more file handles (I<not> file descriptors) to the process,
630to prepare a call to C<run>. 630to prepare a call to C<run>.
631 631
632The process object keeps a reference to the handles until this is done, 632The process object keeps a reference to the handles until they have
633so you must not explicitly close the handles. This is most easily 633been passed over to the process, so you must not explicitly close the
634accomplished by simply not storing the file handles anywhere after passing 634handles. This is most easily accomplished by simply not storing the file
635them to this method. 635handles anywhere after passing them to this method - when AnyEvent::Fork
636is finished using them, perl will automatically close them.
636 637
637Returns the process object for easy chaining of method calls. 638Returns the process object for easy chaining of method calls.
638 639
639Example: pass a file handle to a process, and release it without 640Example: pass a file handle to a process, and release it without
640closing. It will be closed automatically when it is no longer used. 641closing. It will be closed automatically when it is no longer used.
656} 657}
657 658
658=item $proc = $proc->send_arg ($string, ...) 659=item $proc = $proc->send_arg ($string, ...)
659 660
660Send one or more argument strings to the process, to prepare a call to 661Send one or more argument strings to the process, to prepare a call to
661C<run>. The strings can be any octet string. 662C<run>. The strings can be any octet strings.
662 663
663The protocol is optimised to pass a moderate number of relatively short 664The protocol is optimised to pass a moderate number of relatively short
664strings - while you can pass up to 4GB of data in one go, this is more 665strings - while you can pass up to 4GB of data in one go, this is more
665meant to pass some ID information or other startup info, not big chunks of 666meant to pass some ID information or other startup info, not big chunks of
666data. 667data.
682Enter the function specified by the function name in C<$func> in the 683Enter the function specified by the function name in C<$func> in the
683process. The function is called with the communication socket as first 684process. The function is called with the communication socket as first
684argument, followed by all file handles and string arguments sent earlier 685argument, followed by all file handles and string arguments sent earlier
685via C<send_fh> and C<send_arg> methods, in the order they were called. 686via C<send_fh> and C<send_arg> methods, in the order they were called.
686 687
688The process object becomes unusable on return from this function - any
689further method calls result in undefined behaviour.
690
687The function name should be fully qualified, but if it isn't, it will be 691The function name should be fully qualified, but if it isn't, it will be
688looked up in the main package. 692looked up in the C<main> package.
689 693
690If the called function returns, doesn't exist, or any error occurs, the 694If the called function returns, doesn't exist, or any error occurs, the
691process exits. 695process exits.
692 696
693Preparing the process is done in the background - when all commands have 697Preparing the process is done in the background - when all commands have
694been sent, the callback is invoked with the local communications socket 698been sent, the callback is invoked with the local communications socket
695as argument. At this point you can start using the socket in any way you 699as argument. At this point you can start using the socket in any way you
696like. 700like.
697
698The process object becomes unusable on return from this function - any
699further method calls result in undefined behaviour.
700 701
701If the communication socket isn't used, it should be closed on both sides, 702If the communication socket isn't used, it should be closed on both sides,
702to save on kernel memory. 703to save on kernel memory.
703 704
704The socket is non-blocking in the parent, and blocking in the newly 705The socket is non-blocking in the parent, and blocking in the newly
779 479 vfork+execs per second, using AnyEvent::Fork->new_exec 780 479 vfork+execs per second, using AnyEvent::Fork->new_exec
780 781
781So how can C<< AnyEvent->new >> be faster than a standard fork, even 782So how can C<< AnyEvent->new >> be faster than a standard fork, even
782though it uses the same operations, but adds a lot of overhead? 783though it uses the same operations, but adds a lot of overhead?
783 784
784The difference is simply the process size: forking the 6MB process takes 785The difference is simply the process size: forking the 5MB process takes
785so much longer than forking the 2.5MB template process that the overhead 786so much longer than forking the 2.5MB template process that the extra
786introduced is canceled out. 787overhead introduced is canceled out.
787 788
788If the benchmark process grows, the normal fork becomes even slower: 789If the benchmark process grows, the normal fork becomes even slower:
789 790
790 1340 new processes, manual fork in a 20MB process 791 1340 new processes, manual fork of a 20MB process
791 731 new processes, manual fork in a 200MB process 792 731 new processes, manual fork of a 200MB process
792 235 new processes, manual fork in a 2000MB process 793 235 new processes, manual fork of a 2000MB process
793 794
794What that means (to me) is that I can use this module without having a 795What that means (to me) is that I can use this module without having a bad
795very bad conscience because of the extra overhead required to start new 796conscience because of the extra overhead required to start new processes.
796processes.
797 797
798=head1 TYPICAL PROBLEMS 798=head1 TYPICAL PROBLEMS
799 799
800This section lists typical problems that remain. I hope by recognising 800This section lists typical problems that remain. I hope by recognising
801them, most can be avoided. 801them, most can be avoided.
802 802
803=over 4 803=over 4
804 804
805=item "leaked" file descriptors for exec'ed processes 805=item leaked file descriptors for exec'ed processes
806 806
807POSIX systems inherit file descriptors by default when exec'ing a new 807POSIX systems inherit file descriptors by default when exec'ing a new
808process. While perl itself laudably sets the close-on-exec flags on new 808process. While perl itself laudably sets the close-on-exec flags on new
809file handles, most C libraries don't care, and even if all cared, it's 809file handles, most C libraries don't care, and even if all cared, it's
810often not possible to set the flag in a race-free manner. 810often not possible to set the flag in a race-free manner.
830libraries or the code that leaks those file descriptors. 830libraries or the code that leaks those file descriptors.
831 831
832Fortunately, most of these leaked descriptors do no harm, other than 832Fortunately, most of these leaked descriptors do no harm, other than
833sitting on some resources. 833sitting on some resources.
834 834
835=item "leaked" file descriptors for fork'ed processes 835=item leaked file descriptors for fork'ed processes
836 836
837Normally, L<AnyEvent::Fork> does start new processes by exec'ing them, 837Normally, L<AnyEvent::Fork> does start new processes by exec'ing them,
838which closes file descriptors not marked for being inherited. 838which closes file descriptors not marked for being inherited.
839 839
840However, L<AnyEvent::Fork::Early> and L<AnyEvent::Fork::Template> offer 840However, L<AnyEvent::Fork::Early> and L<AnyEvent::Fork::Template> offer
849 849
850The solution is to either not load these modules before use'ing 850The solution is to either not load these modules before use'ing
851L<AnyEvent::Fork::Early> or L<AnyEvent::Fork::Template>, or to delay 851L<AnyEvent::Fork::Early> or L<AnyEvent::Fork::Template>, or to delay
852initialising them, for example, by calling C<init Gtk2> manually. 852initialising them, for example, by calling C<init Gtk2> manually.
853 853
854=item exit runs destructors 854=item exiting calls object destructors
855 855
856This only applies to users of Lc<AnyEvent::Fork:Early> and 856This only applies to users of Lc<AnyEvent::Fork:Early> and
857L<AnyEvent::Fork::Template>. 857L<AnyEvent::Fork::Template>.
858 858
859When a process created by AnyEvent::Fork exits, it might do so by calling 859When a process created by AnyEvent::Fork exits, it might do so by calling
881to make it so, mostly due to the bloody broken perl that nobody seems to 881to make it so, mostly due to the bloody broken perl that nobody seems to
882care about. The fork emulation is a bad joke - I have yet to see something 882care about. The fork emulation is a bad joke - I have yet to see something
883useful that you can do with it without running into memory corruption 883useful that you can do with it without running into memory corruption
884issues or other braindamage. Hrrrr. 884issues or other braindamage. Hrrrr.
885 885
886Cygwin perl is not supported at the moment, as it should implement fd 886Cygwin perl is not supported at the moment due to some hilarious
887passing, but doesn't, and rolling my own is hard, as cygwin doesn't 887shortcomings of its API - see L<IO::FDPoll> for more details.
888support enough functionality to do it.
889 888
890=head1 SEE ALSO 889=head1 SEE ALSO
891 890
892L<AnyEvent::Fork::Early> (to avoid executing a perl interpreter), 891L<AnyEvent::Fork::Early> (to avoid executing a perl interpreter),
893L<AnyEvent::Fork::Template> (to create a process by forking the main 892L<AnyEvent::Fork::Template> (to create a process by forking the main

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