… | |
… | |
599 | |
599 | |
600 | =item $cv->begin ([group callback]) |
600 | =item $cv->begin ([group callback]) |
601 | |
601 | |
602 | =item $cv->end |
602 | =item $cv->end |
603 | |
603 | |
604 | These two methods are EXPERIMENTAL and MIGHT CHANGE. |
|
|
605 | |
|
|
606 | These two methods can be used to combine many transactions/events into |
604 | These two methods can be used to combine many transactions/events into |
607 | one. For example, a function that pings many hosts in parallel might want |
605 | one. For example, a function that pings many hosts in parallel might want |
608 | to use a condition variable for the whole process. |
606 | to use a condition variable for the whole process. |
609 | |
607 | |
610 | Every call to C<< ->begin >> will increment a counter, and every call to |
608 | Every call to C<< ->begin >> will increment a counter, and every call to |
611 | C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end |
609 | C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end |
612 | >>, the (last) callback passed to C<begin> will be executed. That callback |
610 | >>, the (last) callback passed to C<begin> will be executed. That callback |
613 | is I<supposed> to call C<< ->send >>, but that is not required. If no |
611 | is I<supposed> to call C<< ->send >>, but that is not required. If no |
614 | callback was set, C<send> will be called without any arguments. |
612 | callback was set, C<send> will be called without any arguments. |
615 | |
613 | |
616 | Let's clarify this with the ping example: |
614 | You can think of C<< $cv->send >> giving you an OR condition (one call |
|
|
615 | sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND |
|
|
616 | condition (all C<begin> calls must be C<end>'ed before the condvar sends). |
|
|
617 | |
|
|
618 | Let's start with a simple example: you have two I/O watchers (for example, |
|
|
619 | STDOUT and STDERR for a program), and you want to wait for both streams to |
|
|
620 | close before activating a condvar: |
|
|
621 | |
|
|
622 | my $cv = AnyEvent->condvar; |
|
|
623 | |
|
|
624 | $cv->begin; # first watcher |
|
|
625 | my $w1 = AnyEvent->io (fh => $fh1, cb => sub { |
|
|
626 | defined sysread $fh1, my $buf, 4096 |
|
|
627 | or $cv->end; |
|
|
628 | }); |
|
|
629 | |
|
|
630 | $cv->begin; # second watcher |
|
|
631 | my $w2 = AnyEvent->io (fh => $fh2, cb => sub { |
|
|
632 | defined sysread $fh2, my $buf, 4096 |
|
|
633 | or $cv->end; |
|
|
634 | }); |
|
|
635 | |
|
|
636 | $cv->recv; |
|
|
637 | |
|
|
638 | This works because for every event source (EOF on file handle), there is |
|
|
639 | one call to C<begin>, so the condvar waits for all calls to C<end> before |
|
|
640 | sending. |
|
|
641 | |
|
|
642 | The ping example mentioned above is slightly more complicated, as the |
|
|
643 | there are results to be passwd back, and the number of tasks that are |
|
|
644 | begung can potentially be zero: |
617 | |
645 | |
618 | my $cv = AnyEvent->condvar; |
646 | my $cv = AnyEvent->condvar; |
619 | |
647 | |
620 | my %result; |
648 | my %result; |
621 | $cv->begin (sub { $cv->send (\%result) }); |
649 | $cv->begin (sub { $cv->send (\%result) }); |
… | |
… | |
641 | loop, which serves two important purposes: first, it sets the callback |
669 | loop, which serves two important purposes: first, it sets the callback |
642 | to be called once the counter reaches C<0>, and second, it ensures that |
670 | to be called once the counter reaches C<0>, and second, it ensures that |
643 | C<send> is called even when C<no> hosts are being pinged (the loop |
671 | C<send> is called even when C<no> hosts are being pinged (the loop |
644 | doesn't execute once). |
672 | doesn't execute once). |
645 | |
673 | |
646 | This is the general pattern when you "fan out" into multiple subrequests: |
674 | This is the general pattern when you "fan out" into multiple (but |
647 | use an outer C<begin>/C<end> pair to set the callback and ensure C<end> |
675 | potentially none) subrequests: use an outer C<begin>/C<end> pair to set |
648 | is called at least once, and then, for each subrequest you start, call |
676 | the callback and ensure C<end> is called at least once, and then, for each |
649 | C<begin> and for each subrequest you finish, call C<end>. |
677 | subrequest you start, call C<begin> and for each subrequest you finish, |
|
|
678 | call C<end>. |
650 | |
679 | |
651 | =back |
680 | =back |
652 | |
681 | |
653 | =head3 METHODS FOR CONSUMERS |
682 | =head3 METHODS FOR CONSUMERS |
654 | |
683 | |
… | |
… | |
939 | no warnings; |
968 | no warnings; |
940 | use strict qw(vars subs); |
969 | use strict qw(vars subs); |
941 | |
970 | |
942 | use Carp; |
971 | use Carp; |
943 | |
972 | |
944 | our $VERSION = 4.412; |
973 | our $VERSION = 4.452; |
945 | our $MODEL; |
974 | our $MODEL; |
946 | |
975 | |
947 | our $AUTOLOAD; |
976 | our $AUTOLOAD; |
948 | our @ISA; |
977 | our @ISA; |
949 | |
978 | |
… | |
… | |
1695 | EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers |
1724 | EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers |
1696 | CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal |
1725 | CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal |
1697 | Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation |
1726 | Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation |
1698 | Event/Event 16000 517 32.20 31.80 0.81 Event native interface |
1727 | Event/Event 16000 517 32.20 31.80 0.81 Event native interface |
1699 | Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers |
1728 | Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers |
|
|
1729 | IOAsync/Any 16000 989 38.10 32.77 11.13 via IO::Async::Loop::IO_Poll |
|
|
1730 | IOAsync/Any 16000 990 37.59 29.50 10.61 via IO::Async::Loop::Epoll |
1700 | Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour |
1731 | Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour |
1701 | Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers |
1732 | Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers |
1702 | POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event |
1733 | POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event |
1703 | POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select |
1734 | POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select |
1704 | |
1735 | |
… | |
… | |
1733 | performance becomes really bad with lots of file descriptors (and few of |
1764 | performance becomes really bad with lots of file descriptors (and few of |
1734 | them active), of course, but this was not subject of this benchmark. |
1765 | them active), of course, but this was not subject of this benchmark. |
1735 | |
1766 | |
1736 | The C<Event> module has a relatively high setup and callback invocation |
1767 | The C<Event> module has a relatively high setup and callback invocation |
1737 | cost, but overall scores in on the third place. |
1768 | cost, but overall scores in on the third place. |
|
|
1769 | |
|
|
1770 | C<IO::Async> performs admirably well, about on par with C<Event>, even |
|
|
1771 | when using its pure perl backend. |
1738 | |
1772 | |
1739 | C<Glib>'s memory usage is quite a bit higher, but it features a |
1773 | C<Glib>'s memory usage is quite a bit higher, but it features a |
1740 | faster callback invocation and overall ends up in the same class as |
1774 | faster callback invocation and overall ends up in the same class as |
1741 | C<Event>. However, Glib scales extremely badly, doubling the number of |
1775 | C<Event>. However, Glib scales extremely badly, doubling the number of |
1742 | watchers increases the processing time by more than a factor of four, |
1776 | watchers increases the processing time by more than a factor of four, |
… | |
… | |
1820 | it to another server. This includes deleting the old timeout and creating |
1854 | it to another server. This includes deleting the old timeout and creating |
1821 | a new one that moves the timeout into the future. |
1855 | a new one that moves the timeout into the future. |
1822 | |
1856 | |
1823 | =head3 Results |
1857 | =head3 Results |
1824 | |
1858 | |
1825 | name sockets create request |
1859 | name sockets create request |
1826 | EV 20000 69.01 11.16 |
1860 | EV 20000 69.01 11.16 |
1827 | Perl 20000 73.32 35.87 |
1861 | Perl 20000 73.32 35.87 |
|
|
1862 | IOAsync 20000 157.00 98.14 epoll |
|
|
1863 | IOAsync 20000 159.31 616.06 poll |
1828 | Event 20000 212.62 257.32 |
1864 | Event 20000 212.62 257.32 |
1829 | Glib 20000 651.16 1896.30 |
1865 | Glib 20000 651.16 1896.30 |
1830 | POE 20000 349.67 12317.24 uses POE::Loop::Event |
1866 | POE 20000 349.67 12317.24 uses POE::Loop::Event |
1831 | |
1867 | |
1832 | =head3 Discussion |
1868 | =head3 Discussion |
1833 | |
1869 | |
1834 | This benchmark I<does> measure scalability and overall performance of the |
1870 | This benchmark I<does> measure scalability and overall performance of the |
1835 | particular event loop. |
1871 | particular event loop. |
… | |
… | |
1837 | EV is again fastest. Since it is using epoll on my system, the setup time |
1873 | EV is again fastest. Since it is using epoll on my system, the setup time |
1838 | is relatively high, though. |
1874 | is relatively high, though. |
1839 | |
1875 | |
1840 | Perl surprisingly comes second. It is much faster than the C-based event |
1876 | Perl surprisingly comes second. It is much faster than the C-based event |
1841 | loops Event and Glib. |
1877 | loops Event and Glib. |
|
|
1878 | |
|
|
1879 | IO::Async performs very well when using its epoll backend, and still quite |
|
|
1880 | good compared to Glib when using its pure perl backend. |
1842 | |
1881 | |
1843 | Event suffers from high setup time as well (look at its code and you will |
1882 | Event suffers from high setup time as well (look at its code and you will |
1844 | understand why). Callback invocation also has a high overhead compared to |
1883 | understand why). Callback invocation also has a high overhead compared to |
1845 | the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event |
1884 | the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event |
1846 | uses select or poll in basically all documented configurations. |
1885 | uses select or poll in basically all documented configurations. |