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Revision 1.85 by root, Sat Oct 28 01:40:30 2006 UTC vs.
Revision 1.87 by root, Sun Oct 29 00:52:02 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
… …
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", $VERSION);
161} 207}
162 208
163=head1 FUNCTIONS 209=head1 FUNCTIONS
164 210
165=head2 AIO FUNCTIONS 211=head2 AIO REQUEST FUNCTIONS
166 212
167All the C<aio_*> calls are more or less thin wrappers around the syscall 213All the C<aio_*> calls are more or less thin wrappers around the syscall
168with the same name (sans C<aio_>). The arguments are similar or identical, 214with the same name (sans C<aio_>). The arguments are similar or identical,
169and they all accept an additional (and optional) C<$callback> argument 215and they all accept an additional (and optional) C<$callback> argument
170which must be a code reference. This code reference will get called with 216which must be a code reference. This code reference will get called with
… …
173syscall has been executed asynchronously. 219syscall has been executed asynchronously.
174 220
175All functions expecting a filehandle keep a copy of the filehandle 221All functions expecting a filehandle keep a copy of the filehandle
176internally until the request has finished. 222internally until the request has finished.
177 223
178All requests return objects of type L<IO::AIO::REQ> that allow further 224All functions return request objects of type L<IO::AIO::REQ> that allow
179manipulation of those requests while they are in-flight. 225further manipulation of those requests while they are in-flight.
180 226
181The pathnames you pass to these routines I<must> be absolute and 227The pathnames you pass to these routines I<must> be absolute and
182encoded in byte form. The reason for the former is that at the time the 228encoded as octets. The reason for the former is that at the time the
183request is being executed, the current working directory could have 229request is being executed, the current working directory could have
184changed. Alternatively, you can make sure that you never change the 230changed. Alternatively, you can make sure that you never change the
185current working directory. 231current working directory anywhere in the program and then use relative
232paths.
186 233
187To encode pathnames to byte form, either make sure you either: a) 234To encode pathnames as octets, either make sure you either: a) always pass
188always pass in filenames you got from outside (command line, readdir 235in filenames you got from outside (command line, readdir etc.) without
189etc.), b) are ASCII or ISO 8859-1, c) use the Encode module and encode 236tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode
190your pathnames to the locale (or other) encoding in effect in the user 237your pathnames to the locale (or other) encoding in effect in the user
191environment, d) use Glib::filename_from_unicode on unicode filenames or e) 238environment, d) use Glib::filename_from_unicode on unicode filenames or e)
192use something else. 239use something else to ensure your scalar has the correct contents.
240
241This works, btw. independent of the internal UTF-8 bit, which IO::AIO
242handles correctly wether it is set or not.
193 243
194=over 4 244=over 4
195 245
196=item $prev_pri = aioreq_pri [$pri] 246=item $prev_pri = aioreq_pri [$pri]
197 247
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220 }; 270 };
221 271
222=item aioreq_nice $pri_adjust 272=item aioreq_nice $pri_adjust
223 273
224Similar to C<aioreq_pri>, but subtracts the given value from the current 274Similar to C<aioreq_pri>, but subtracts the given value from the current
225priority, so effects are cumulative. 275priority, so the effect is cumulative.
226 276
227=item aio_open $pathname, $flags, $mode, $callback->($fh) 277=item aio_open $pathname, $flags, $mode, $callback->($fh)
228 278
229Asynchronously open or create a file and call the callback with a newly 279Asynchronously open or create a file and call the callback with a newly
230created filehandle for the file. 280created filehandle for the file.
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347Asynchronously unlink (delete) a file and call the callback with the 397Asynchronously unlink (delete) a file and call the callback with the
348result code. 398result code.
349 399
350=item aio_mknod $path, $mode, $dev, $callback->($status) 400=item aio_mknod $path, $mode, $dev, $callback->($status)
351 401
402[EXPERIMENTAL]
403
352Asynchronously create a device node (or fifo). See mknod(2). 404Asynchronously create a device node (or fifo). See mknod(2).
353 405
354The only portable (POSIX) way of calling this function is: 406The only (POSIX-) portable way of calling this function is:
355 407
356 aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ... 408 aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...
357 409
358=item aio_link $srcpath, $dstpath, $callback->($status) 410=item aio_link $srcpath, $dstpath, $callback->($status)
359 411
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845 897
846=back 898=back
847 899
848=head2 SUPPORT FUNCTIONS 900=head2 SUPPORT FUNCTIONS
849 901
902=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
903
850=over 4 904=over 4
851 905
852=item $fileno = IO::AIO::poll_fileno 906=item $fileno = IO::AIO::poll_fileno
853 907
854Return the I<request result pipe file descriptor>. This filehandle must be 908Return the I<request result pipe file descriptor>. This filehandle must be
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858 912
859See C<poll_cb> for an example. 913See C<poll_cb> for an example.
860 914
861=item IO::AIO::poll_cb 915=item IO::AIO::poll_cb
862 916
863Process all outstanding events on the result pipe. You have to call this 917Process some outstanding events on the result pipe. You have to call this
864regularly. Returns the number of events processed. Returns immediately 918regularly. Returns the number of events processed. Returns immediately
865when no events are outstanding. 919when no events are outstanding. The amount of events processed depends on
920the settings of C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
866 921
867If not all requests were processed for whatever reason, the filehandle 922If not all requests were processed for whatever reason, the filehandle
868will still be ready when C<poll_cb> returns. 923will still be ready when C<poll_cb> returns.
869 924
870Example: Install an Event watcher that automatically calls 925Example: Install an Event watcher that automatically calls
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872 927
873 Event->io (fd => IO::AIO::poll_fileno, 928 Event->io (fd => IO::AIO::poll_fileno,
874 poll => 'r', async => 1, 929 poll => 'r', async => 1,
875 cb => \&IO::AIO::poll_cb); 930 cb => \&IO::AIO::poll_cb);
876 931
877=item IO::AIO::poll_some $max_requests 932=item IO::AIO::max_poll_reqs $nreqs
878 933
879Similar to C<poll_cb>, but only processes up to C<$max_requests> requests 934=item IO::AIO::max_poll_time $seconds
880at a time.
881 935
882Useful if you want to ensure some level of interactiveness when perl is 936These set the maximum number of requests (default C<0>, meaning infinity)
883not fast enough to process all requests in time. 937that are being processed by C<IO::AIO::poll_cb> in one call, respectively
938the maximum amount of time (default C<0>, meaning infinity) spent in
939C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
940of time C<poll_cb> is allowed to use).
941
942Setting these is useful if you want to ensure some level of
943interactiveness when perl is not fast enough to process all requests in
944time.
945
946For interactive programs, values such as C<0.01> to C<0.1> should be fine.
884 947
885Example: Install an Event watcher that automatically calls 948Example: Install an Event watcher that automatically calls
886IO::AIO::poll_some with low priority, to ensure that other parts of the 949IO::AIO::poll_some with low priority, to ensure that other parts of the
887program get the CPU sometimes even under high AIO load. 950program get the CPU sometimes even under high AIO load.
888 951
952 # try not to spend much more than 0.1s in poll_cb
953 IO::AIO::max_poll_time 0.1;
954
955 # use a low priority so other tasks have priority
889 Event->io (fd => IO::AIO::poll_fileno, 956 Event->io (fd => IO::AIO::poll_fileno,
890 poll => 'r', nice => 1, 957 poll => 'r', nice => 1,
891 cb => sub { IO::AIO::poll_some 256 }); 958 cb => &IO::AIO::poll_cb);
892 959
893=item IO::AIO::poll_wait 960=item IO::AIO::poll_wait
894 961
895Wait till the result filehandle becomes ready for reading (simply does a 962Wait 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 963C<select> on the filehandle. This is useful if you want to synchronously
897for some requests to finish). 964wait for some requests to finish).
898 965
899See C<nreqs> for an example. 966See C<nreqs> for an example.
900 967
968=item IO::AIO::poll
969
970Waits until some requests have been handled.
971
972Strictly equivalent to:
973
974 IO::AIO::poll_wait, IO::AIO::poll_cb
975 if IO::AIO::nreqs;
976
901=item IO::AIO::nreqs 977=item IO::AIO::flush
902 978
903Returns the number of requests currently in the ready, execute or pending 979Wait till all outstanding AIO requests have been handled.
904states (i.e. for which their callback has not been invoked yet).
905 980
906Example: wait till there are no outstanding requests anymore: 981Strictly equivalent to:
907 982
908 IO::AIO::poll_wait, IO::AIO::poll_cb 983 IO::AIO::poll_wait, IO::AIO::poll_cb
909 while IO::AIO::nreqs; 984 while IO::AIO::nreqs;
910 985
911=item IO::AIO::nready 986=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;
938 987
939=item IO::AIO::min_parallel $nthreads 988=item IO::AIO::min_parallel $nthreads
940 989
941Set the minimum number of AIO threads to C<$nthreads>. The current 990Set the minimum number of AIO threads to C<$nthreads>. The current
942default is C<8>, which means eight asynchronous operations can execute 991default is C<8>, which means eight asynchronous operations can execute
943concurrently at any one time (the number of outstanding requests, 992concurrently at any one time (the number of outstanding requests,
944however, is unlimited). 993however, is unlimited).
945 994
946IO::AIO starts threads only on demand, when an AIO request is queued and 995IO::AIO starts threads only on demand, when an AIO request is queued and
947no free thread exists. 996no free thread exists. Please note that queueing up a hundred requests can
997create demand for a hundred threads, even if it turns out that everything
998is in the cache and could have been processed faster by a single thread.
948 999
949It is recommended to keep the number of threads relatively low, as some 1000It is recommended to keep the number of threads relatively low, as some
950Linux kernel versions will scale negatively with the number of threads 1001Linux kernel versions will scale negatively with the number of threads
951(higher parallelity => MUCH higher latency). With current Linux 2.6 1002(higher parallelity => MUCH higher latency). With current Linux 2.6
952versions, 4-32 threads should be fine. 1003versions, 4-32 threads should be fine.
… …
966This module automatically runs C<max_parallel 0> at program end, to ensure 1017This module automatically runs C<max_parallel 0> at program end, to ensure
967that all threads are killed and that there are no outstanding requests. 1018that all threads are killed and that there are no outstanding requests.
968 1019
969Under normal circumstances you don't need to call this function. 1020Under normal circumstances you don't need to call this function.
970 1021
1022=item IO::AIO::max_idle $nthreads
1023
1024Limit the number of threads (default: 4) that are allowed to idle (i.e.,
1025threads that did not get a request to process within 10 seconds). That
1026means if a thread becomes idle while C<$nthreads> other threads are also
1027idle, it will free its resources and exit.
1028
1029This is useful when you allow a large number of threads (e.g. 100 or 1000)
1030to allow for extremely high load situations, but want to free resources
1031under normal circumstances (1000 threads can easily consume 30MB of RAM).
1032
1033The default is probably ok in most situations, especially if thread
1034creation is fast. If thread creation is very slow on your system you might
1035want to use larger values.
1036
971=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs 1037=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs
972 1038
973This is a very bad function to use in interactive programs because it 1039This 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 1040blocks, and a bad way to reduce concurrency because it is inexact: Better
975use an C<aio_group> together with a feed callback. 1041use an C<aio_group> together with a feed callback.
… …
983number of outstanding requests. 1049number of outstanding requests.
984 1050
985You can still queue as many requests as you want. Therefore, 1051You can still queue as many requests as you want. Therefore,
986C<max_oustsanding> is mainly useful in simple scripts (with low values) or 1052C<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). 1053as a stop gap to shield against fatal memory overflow (with large values).
1054
1055=head3 STATISTICAL INFORMATION
1056
1057=item IO::AIO::nreqs
1058
1059Returns the number of requests currently in the ready, execute or pending
1060states (i.e. for which their callback has not been invoked yet).
1061
1062Example: wait till there are no outstanding requests anymore:
1063
1064 IO::AIO::poll_wait, IO::AIO::poll_cb
1065 while IO::AIO::nreqs;
1066
1067=item IO::AIO::nready
1068
1069Returns the number of requests currently in the ready state (not yet
1070executed).
1071
1072=item IO::AIO::npending
1073
1074Returns the number of requests currently in the pending state (executed,
1075but not yet processed by poll_cb).
988 1076
989=back 1077=back
990 1078
991=cut 1079=cut
992 1080

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