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Comparing IO-AIO/AIO.pm (file contents):
Revision 1.85 by root, Sat Oct 28 01:40:30 2006 UTC vs.
Revision 1.86 by root, Sat Oct 28 23:32:29 2006 UTC

… …
82Although the module will work with in the presence of other (Perl-) 82Although the module will work with in the presence of other (Perl-)
83threads, it is currently not reentrant in any way, so use appropriate 83threads, it is currently not reentrant in any way, so use appropriate
84locking yourself, always call C<poll_cb> from within the same thread, or 84locking yourself, always call C<poll_cb> from within the same thread, or
85never call C<poll_cb> (or other C<aio_> functions) recursively. 85never call C<poll_cb> (or other C<aio_> functions) recursively.
86 86
87=head2 EXAMPLE
88
89This is a simple example that uses the Event module and loads
90F</etc/passwd> asynchronously:
91
92 use Fcntl;
93 use Event;
94 use IO::AIO;
95
96 # register the IO::AIO callback with Event
97 Event->io (fd => IO::AIO::poll_fileno,
98 poll => 'r',
99 cb => \&IO::AIO::poll_cb);
100
101 # queue the request to open /etc/passwd
102 aio_open "/etc/passwd", O_RDONLY, 0, sub {
103 my $fh = $_[0]
104 or die "error while opening: $!";
105
106 # stat'ing filehandles is generally non-blocking
107 my $size = -s $fh;
108
109 # queue a request to read the file
110 my $contents;
111 aio_read $fh, 0, $size, $contents, 0, sub {
112 $_[0] == $size
113 or die "short read: $!";
114
115 close $fh;
116
117 # file contents now in $contents
118 print $contents;
119
120 # exit event loop and program
121 Event::unloop;
122 };
123 };
124
125 # possibly queue up other requests, or open GUI windows,
126 # check for sockets etc. etc.
127
128 # process events as long as there are some:
129 Event::loop;
130
87=head1 REQUEST ANATOMY AND LIFETIME 131=head1 REQUEST ANATOMY AND LIFETIME
88 132
89Every C<aio_*> function creates a request. which is a C data structure not 133Every C<aio_*> function creates a request. which is a C data structure not
90directly visible to Perl. 134directly visible to Perl.
91 135
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142use strict 'vars'; 186use strict 'vars';
143 187
144use base 'Exporter'; 188use base 'Exporter';
145 189
146BEGIN { 190BEGIN {
147 our $VERSION = '2.0'; 191 our $VERSION = '2.1';
148 192
149 our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat 193 our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat
150 aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink 194 aio_lstat aio_unlink aio_rmdir aio_readdir aio_scandir aio_symlink
151 aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move 195 aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move
152 aio_copy aio_group aio_nop aio_mknod); 196 aio_copy aio_group aio_nop aio_mknod);
153 our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice)); 197 our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
154 our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush 198 our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
155 min_parallel max_parallel nreqs nready npending); 199 min_parallel max_parallel max_idle
200 nreqs nready npending nthreads
201 max_poll_time max_poll_reqs);
156 202
157 @IO::AIO::GRP::ISA = 'IO::AIO::REQ'; 203 @IO::AIO::GRP::ISA = 'IO::AIO::REQ';
158 204
159 require XSLoader; 205 require XSLoader;
160 XSLoader::load ("IO::AIO", $VERSION); 206 XSLoader::load ("IO::AIO", $VERSION);
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347Asynchronously unlink (delete) a file and call the callback with the 393Asynchronously unlink (delete) a file and call the callback with the
348result code. 394result code.
349 395
350=item aio_mknod $path, $mode, $dev, $callback->($status) 396=item aio_mknod $path, $mode, $dev, $callback->($status)
351 397
398[EXPERIMENTAL]
399
352Asynchronously create a device node (or fifo). See mknod(2). 400Asynchronously create a device node (or fifo). See mknod(2).
353 401
354The only portable (POSIX) way of calling this function is: 402The only (POSIX-) portable way of calling this function is:
355 403
356 aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ... 404 aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...
357 405
358=item aio_link $srcpath, $dstpath, $callback->($status) 406=item aio_link $srcpath, $dstpath, $callback->($status)
359 407
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845 893
846=back 894=back
847 895
848=head2 SUPPORT FUNCTIONS 896=head2 SUPPORT FUNCTIONS
849 897
898=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
899
850=over 4 900=over 4
851 901
852=item $fileno = IO::AIO::poll_fileno 902=item $fileno = IO::AIO::poll_fileno
853 903
854Return the I<request result pipe file descriptor>. This filehandle must be 904Return the I<request result pipe file descriptor>. This filehandle must be
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858 908
859See C<poll_cb> for an example. 909See C<poll_cb> for an example.
860 910
861=item IO::AIO::poll_cb 911=item IO::AIO::poll_cb
862 912
863Process all outstanding events on the result pipe. You have to call this 913Process some outstanding events on the result pipe. You have to call this
864regularly. Returns the number of events processed. Returns immediately 914regularly. Returns the number of events processed. Returns immediately
865when no events are outstanding. 915when no events are outstanding. The amount of events processed depends on
916the settings of C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
866 917
867If not all requests were processed for whatever reason, the filehandle 918If not all requests were processed for whatever reason, the filehandle
868will still be ready when C<poll_cb> returns. 919will still be ready when C<poll_cb> returns.
869 920
870Example: Install an Event watcher that automatically calls 921Example: Install an Event watcher that automatically calls
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872 923
873 Event->io (fd => IO::AIO::poll_fileno, 924 Event->io (fd => IO::AIO::poll_fileno,
874 poll => 'r', async => 1, 925 poll => 'r', async => 1,
875 cb => \&IO::AIO::poll_cb); 926 cb => \&IO::AIO::poll_cb);
876 927
877=item IO::AIO::poll_some $max_requests 928=item IO::AIO::max_poll_reqs $nreqs
878 929
879Similar to C<poll_cb>, but only processes up to C<$max_requests> requests 930=item IO::AIO::max_poll_time $seconds
880at a time.
881 931
882Useful if you want to ensure some level of interactiveness when perl is 932These set the maximum number of requests (default C<0>, meaning infinity)
883not fast enough to process all requests in time. 933that are being processed by C<IO::AIO::poll_cb> in one call, respectively
934the maximum amount of time (default C<0>, meaning infinity) spent in
935C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
936of time C<poll_cb> is allowed to use).
937
938Setting these is useful if you want to ensure some level of
939interactiveness when perl is not fast enough to process all requests in
940time.
941
942For interactive programs, values such as C<0.01> to C<0.1> should be fine.
884 943
885Example: Install an Event watcher that automatically calls 944Example: Install an Event watcher that automatically calls
886IO::AIO::poll_some with low priority, to ensure that other parts of the 945IO::AIO::poll_some with low priority, to ensure that other parts of the
887program get the CPU sometimes even under high AIO load. 946program get the CPU sometimes even under high AIO load.
888 947
948 # try not to spend much more than 0.1s in poll_cb
949 IO::AIO::max_poll_time 0.1;
950
951 # use a low priority so other tasks have priority
889 Event->io (fd => IO::AIO::poll_fileno, 952 Event->io (fd => IO::AIO::poll_fileno,
890 poll => 'r', nice => 1, 953 poll => 'r', nice => 1,
891 cb => sub { IO::AIO::poll_some 256 }); 954 cb => &IO::AIO::poll_cb);
892 955
893=item IO::AIO::poll_wait 956=item IO::AIO::poll_wait
894 957
895Wait till the result filehandle becomes ready for reading (simply does a 958Wait till the result filehandle becomes ready for reading (simply does a
896C<select> on the filehandle. This is useful if you want to synchronously wait 959C<select> on the filehandle. This is useful if you want to synchronously
897for some requests to finish). 960wait for some requests to finish).
898 961
899See C<nreqs> for an example. 962See C<nreqs> for an example.
900 963
964=item IO::AIO::poll
965
966Waits until some requests have been handled.
967
968Strictly equivalent to:
969
970 IO::AIO::poll_wait, IO::AIO::poll_cb
971 if IO::AIO::nreqs;
972
901=item IO::AIO::nreqs 973=item IO::AIO::flush
902 974
903Returns the number of requests currently in the ready, execute or pending 975Wait till all outstanding AIO requests have been handled.
904states (i.e. for which their callback has not been invoked yet).
905 976
906Example: wait till there are no outstanding requests anymore: 977Strictly equivalent to:
907 978
908 IO::AIO::poll_wait, IO::AIO::poll_cb 979 IO::AIO::poll_wait, IO::AIO::poll_cb
909 while IO::AIO::nreqs; 980 while IO::AIO::nreqs;
910 981
911=item IO::AIO::nready 982=head3 CONTROLLING THE NUMBER OF THREADS
912
913Returns the number of requests currently in the ready state (not yet
914executed).
915
916=item IO::AIO::npending
917
918Returns the number of requests currently in the pending state (executed,
919but not yet processed by poll_cb).
920
921=item IO::AIO::flush
922
923Wait till all outstanding AIO requests have been handled.
924
925Strictly equivalent to:
926
927 IO::AIO::poll_wait, IO::AIO::poll_cb
928 while IO::AIO::nreqs;
929
930=item IO::AIO::poll
931
932Waits until some requests have been handled.
933
934Strictly equivalent to:
935
936 IO::AIO::poll_wait, IO::AIO::poll_cb
937 if IO::AIO::nreqs;
938 983
939=item IO::AIO::min_parallel $nthreads 984=item IO::AIO::min_parallel $nthreads
940 985
941Set the minimum number of AIO threads to C<$nthreads>. The current 986Set the minimum number of AIO threads to C<$nthreads>. The current
942default is C<8>, which means eight asynchronous operations can execute 987default is C<8>, which means eight asynchronous operations can execute
943concurrently at any one time (the number of outstanding requests, 988concurrently at any one time (the number of outstanding requests,
944however, is unlimited). 989however, is unlimited).
945 990
946IO::AIO starts threads only on demand, when an AIO request is queued and 991IO::AIO starts threads only on demand, when an AIO request is queued and
947no free thread exists. 992no free thread exists. Please note that queueing up a hundred requests can
993create demand for a hundred threads, even if it turns out that everything
994is in the cache and could have been processed faster by a single thread.
948 995
949It is recommended to keep the number of threads relatively low, as some 996It is recommended to keep the number of threads relatively low, as some
950Linux kernel versions will scale negatively with the number of threads 997Linux kernel versions will scale negatively with the number of threads
951(higher parallelity => MUCH higher latency). With current Linux 2.6 998(higher parallelity => MUCH higher latency). With current Linux 2.6
952versions, 4-32 threads should be fine. 999versions, 4-32 threads should be fine.
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966This module automatically runs C<max_parallel 0> at program end, to ensure 1013This module automatically runs C<max_parallel 0> at program end, to ensure
967that all threads are killed and that there are no outstanding requests. 1014that all threads are killed and that there are no outstanding requests.
968 1015
969Under normal circumstances you don't need to call this function. 1016Under normal circumstances you don't need to call this function.
970 1017
1018=item IO::AIO::max_idle $nthreads
1019
1020Limit the number of threads (default: 4) that are allowed to idle (i.e.,
1021threads that did not get a request to process within 10 seconds). That
1022means if a thread becomes idle while C<$nthreads> other threads are also
1023idle, it will free its resources and exit.
1024
1025This is useful when you allow a large number of threads (e.g. 100 or 1000)
1026to allow for extremely high load situations, but want to free resources
1027under normal circumstances (1000 threads can easily consume 30MB of RAM).
1028
1029The default is probably ok in most situations, especially if thread
1030creation is fast. If thread creation is very slow on your system you might
1031want to use larger values.
1032
971=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs 1033=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs
972 1034
973This is a very bad function to use in interactive programs because it 1035This is a very bad function to use in interactive programs because it
974blocks, and a bad way to reduce concurrency because it is inexact: Better 1036blocks, and a bad way to reduce concurrency because it is inexact: Better
975use an C<aio_group> together with a feed callback. 1037use an C<aio_group> together with a feed callback.
… …
983number of outstanding requests. 1045number of outstanding requests.
984 1046
985You can still queue as many requests as you want. Therefore, 1047You can still queue as many requests as you want. Therefore,
986C<max_oustsanding> is mainly useful in simple scripts (with low values) or 1048C<max_oustsanding> is mainly useful in simple scripts (with low values) or
987as a stop gap to shield against fatal memory overflow (with large values). 1049as a stop gap to shield against fatal memory overflow (with large values).
1050
1051=head3 STATISTICAL INFORMATION
1052
1053=item IO::AIO::nreqs
1054
1055Returns the number of requests currently in the ready, execute or pending
1056states (i.e. for which their callback has not been invoked yet).
1057
1058Example: wait till there are no outstanding requests anymore:
1059
1060 IO::AIO::poll_wait, IO::AIO::poll_cb
1061 while IO::AIO::nreqs;
1062
1063=item IO::AIO::nready
1064
1065Returns the number of requests currently in the ready state (not yet
1066executed).
1067
1068=item IO::AIO::npending
1069
1070Returns the number of requests currently in the pending state (executed,
1071but not yet processed by poll_cb).
988 1072
989=back 1073=back
990 1074
991=cut 1075=cut
992 1076

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