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Revision 1.85 by root, Sat Oct 28 01:40:30 2006 UTC vs.
Revision 1.89 by root, Sun Oct 29 11:03:18 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
… …
132Request has reached the end of its lifetime and holds no resources anymore 176Request has reached the end of its lifetime and holds no resources anymore
133(except possibly for the Perl object, but its connection to the actual 177(except possibly for the Perl object, but its connection to the actual
134aio request is severed and calling its methods will either do nothing or 178aio request is severed and calling its methods will either do nothing or
135result in a runtime error). 179result in a runtime error).
136 180
181=back
182
137=cut 183=cut
138 184
139package IO::AIO; 185package IO::AIO;
140 186
141no warnings; 187no warnings;
142use strict 'vars'; 188use strict 'vars';
143 189
144use base 'Exporter'; 190use base 'Exporter';
145 191
146BEGIN { 192BEGIN {
147 our $VERSION = '2.0'; 193 our $VERSION = '2.1';
148 194
149 our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat 195 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 196 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 197 aio_fsync aio_fdatasync aio_readahead aio_rename aio_link aio_move
152 aio_copy aio_group aio_nop aio_mknod); 198 aio_copy aio_group aio_nop aio_mknod);
153 our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice)); 199 our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
154 our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush 200 our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
155 min_parallel max_parallel nreqs nready npending); 201 min_parallel max_parallel max_idle
202 nreqs nready npending nthreads
203 max_poll_time max_poll_reqs);
156 204
157 @IO::AIO::GRP::ISA = 'IO::AIO::REQ'; 205 @IO::AIO::GRP::ISA = 'IO::AIO::REQ';
158 206
159 require XSLoader; 207 require XSLoader;
160 XSLoader::load ("IO::AIO", $VERSION); 208 XSLoader::load ("IO::AIO", $VERSION);
161} 209}
162 210
163=head1 FUNCTIONS 211=head1 FUNCTIONS
164 212
165=head2 AIO FUNCTIONS 213=head2 AIO REQUEST FUNCTIONS
166 214
167All the C<aio_*> calls are more or less thin wrappers around the syscall 215All the C<aio_*> calls are more or less thin wrappers around the syscall
168with the same name (sans C<aio_>). The arguments are similar or identical, 216with the same name (sans C<aio_>). The arguments are similar or identical,
169and they all accept an additional (and optional) C<$callback> argument 217and they all accept an additional (and optional) C<$callback> argument
170which must be a code reference. This code reference will get called with 218which must be a code reference. This code reference will get called with
… …
173syscall has been executed asynchronously. 221syscall has been executed asynchronously.
174 222
175All functions expecting a filehandle keep a copy of the filehandle 223All functions expecting a filehandle keep a copy of the filehandle
176internally until the request has finished. 224internally until the request has finished.
177 225
178All requests return objects of type L<IO::AIO::REQ> that allow further 226All functions return request objects of type L<IO::AIO::REQ> that allow
179manipulation of those requests while they are in-flight. 227further manipulation of those requests while they are in-flight.
180 228
181The pathnames you pass to these routines I<must> be absolute and 229The 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 230encoded as octets. The reason for the former is that at the time the
183request is being executed, the current working directory could have 231request is being executed, the current working directory could have
184changed. Alternatively, you can make sure that you never change the 232changed. Alternatively, you can make sure that you never change the
185current working directory. 233current working directory anywhere in the program and then use relative
234paths.
186 235
187To encode pathnames to byte form, either make sure you either: a) 236To encode pathnames as octets, either make sure you either: a) always pass
188always pass in filenames you got from outside (command line, readdir 237in 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 238tinkering, 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 239your pathnames to the locale (or other) encoding in effect in the user
191environment, d) use Glib::filename_from_unicode on unicode filenames or e) 240environment, d) use Glib::filename_from_unicode on unicode filenames or e)
192use something else. 241use something else to ensure your scalar has the correct contents.
242
243This works, btw. independent of the internal UTF-8 bit, which IO::AIO
244handles correctly wether it is set or not.
193 245
194=over 4 246=over 4
195 247
196=item $prev_pri = aioreq_pri [$pri] 248=item $prev_pri = aioreq_pri [$pri]
197 249
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220 }; 272 };
221 273
222=item aioreq_nice $pri_adjust 274=item aioreq_nice $pri_adjust
223 275
224Similar to C<aioreq_pri>, but subtracts the given value from the current 276Similar to C<aioreq_pri>, but subtracts the given value from the current
225priority, so effects are cumulative. 277priority, so the effect is cumulative.
226 278
227=item aio_open $pathname, $flags, $mode, $callback->($fh) 279=item aio_open $pathname, $flags, $mode, $callback->($fh)
228 280
229Asynchronously open or create a file and call the callback with a newly 281Asynchronously open or create a file and call the callback with a newly
230created filehandle for the file. 282created filehandle for the file.
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347Asynchronously unlink (delete) a file and call the callback with the 399Asynchronously unlink (delete) a file and call the callback with the
348result code. 400result code.
349 401
350=item aio_mknod $path, $mode, $dev, $callback->($status) 402=item aio_mknod $path, $mode, $dev, $callback->($status)
351 403
404[EXPERIMENTAL]
405
352Asynchronously create a device node (or fifo). See mknod(2). 406Asynchronously create a device node (or fifo). See mknod(2).
353 407
354The only portable (POSIX) way of calling this function is: 408The only (POSIX-) portable way of calling this function is:
355 409
356 aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ... 410 aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...
357 411
358=item aio_link $srcpath, $dstpath, $callback->($status) 412=item aio_link $srcpath, $dstpath, $callback->($status)
359 413
… …
845 899
846=back 900=back
847 901
848=head2 SUPPORT FUNCTIONS 902=head2 SUPPORT FUNCTIONS
849 903
904=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
905
850=over 4 906=over 4
851 907
852=item $fileno = IO::AIO::poll_fileno 908=item $fileno = IO::AIO::poll_fileno
853 909
854Return the I<request result pipe file descriptor>. This filehandle must be 910Return the I<request result pipe file descriptor>. This filehandle must be
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858 914
859See C<poll_cb> for an example. 915See C<poll_cb> for an example.
860 916
861=item IO::AIO::poll_cb 917=item IO::AIO::poll_cb
862 918
863Process all outstanding events on the result pipe. You have to call this 919Process some outstanding events on the result pipe. You have to call this
864regularly. Returns the number of events processed. Returns immediately 920regularly. Returns the number of events processed. Returns immediately
865when no events are outstanding. 921when no events are outstanding. The amount of events processed depends on
922the settings of C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
866 923
867If not all requests were processed for whatever reason, the filehandle 924If not all requests were processed for whatever reason, the filehandle
868will still be ready when C<poll_cb> returns. 925will still be ready when C<poll_cb> returns.
869 926
870Example: Install an Event watcher that automatically calls 927Example: Install an Event watcher that automatically calls
… …
872 929
873 Event->io (fd => IO::AIO::poll_fileno, 930 Event->io (fd => IO::AIO::poll_fileno,
874 poll => 'r', async => 1, 931 poll => 'r', async => 1,
875 cb => \&IO::AIO::poll_cb); 932 cb => \&IO::AIO::poll_cb);
876 933
877=item IO::AIO::poll_some $max_requests 934=item IO::AIO::max_poll_reqs $nreqs
878 935
879Similar to C<poll_cb>, but only processes up to C<$max_requests> requests 936=item IO::AIO::max_poll_time $seconds
880at a time.
881 937
882Useful if you want to ensure some level of interactiveness when perl is 938These set the maximum number of requests (default C<0>, meaning infinity)
883not fast enough to process all requests in time. 939that are being processed by C<IO::AIO::poll_cb> in one call, respectively
940the maximum amount of time (default C<0>, meaning infinity) spent in
941C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
942of time C<poll_cb> is allowed to use).
943
944Setting C<max_poll_time> to a non-zero value creates an overhead of one
945syscall per request processed, which is not normally a problem unless your
946callbacks are really really fast or your OS is really really slow (I am
947not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
948
949Setting these is useful if you want to ensure some level of
950interactiveness when perl is not fast enough to process all requests in
951time.
952
953For interactive programs, values such as C<0.01> to C<0.1> should be fine.
884 954
885Example: Install an Event watcher that automatically calls 955Example: Install an Event watcher that automatically calls
886IO::AIO::poll_some with low priority, to ensure that other parts of the 956IO::AIO::poll_cb with low priority, to ensure that other parts of the
887program get the CPU sometimes even under high AIO load. 957program get the CPU sometimes even under high AIO load.
888 958
959 # try not to spend much more than 0.1s in poll_cb
960 IO::AIO::max_poll_time 0.1;
961
962 # use a low priority so other tasks have priority
889 Event->io (fd => IO::AIO::poll_fileno, 963 Event->io (fd => IO::AIO::poll_fileno,
890 poll => 'r', nice => 1, 964 poll => 'r', nice => 1,
891 cb => sub { IO::AIO::poll_some 256 }); 965 cb => &IO::AIO::poll_cb);
892 966
893=item IO::AIO::poll_wait 967=item IO::AIO::poll_wait
894 968
895Wait till the result filehandle becomes ready for reading (simply does a 969Wait 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 970C<select> on the filehandle. This is useful if you want to synchronously
897for some requests to finish). 971wait for some requests to finish).
898 972
899See C<nreqs> for an example. 973See C<nreqs> for an example.
900 974
975=item IO::AIO::poll
976
977Waits until some requests have been handled.
978
979Strictly equivalent to:
980
981 IO::AIO::poll_wait, IO::AIO::poll_cb
982 if IO::AIO::nreqs;
983
901=item IO::AIO::nreqs 984=item IO::AIO::flush
902 985
903Returns the number of requests currently in the ready, execute or pending 986Wait till all outstanding AIO requests have been handled.
904states (i.e. for which their callback has not been invoked yet).
905 987
906Example: wait till there are no outstanding requests anymore: 988Strictly equivalent to:
907 989
908 IO::AIO::poll_wait, IO::AIO::poll_cb 990 IO::AIO::poll_wait, IO::AIO::poll_cb
909 while IO::AIO::nreqs; 991 while IO::AIO::nreqs;
910 992
911=item IO::AIO::nready 993=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;
938 994
939=item IO::AIO::min_parallel $nthreads 995=item IO::AIO::min_parallel $nthreads
940 996
941Set the minimum number of AIO threads to C<$nthreads>. The current 997Set the minimum number of AIO threads to C<$nthreads>. The current
942default is C<8>, which means eight asynchronous operations can execute 998default is C<8>, which means eight asynchronous operations can execute
943concurrently at any one time (the number of outstanding requests, 999concurrently at any one time (the number of outstanding requests,
944however, is unlimited). 1000however, is unlimited).
945 1001
946IO::AIO starts threads only on demand, when an AIO request is queued and 1002IO::AIO starts threads only on demand, when an AIO request is queued and
947no free thread exists. 1003no free thread exists. Please note that queueing up a hundred requests can
1004create demand for a hundred threads, even if it turns out that everything
1005is in the cache and could have been processed faster by a single thread.
948 1006
949It is recommended to keep the number of threads relatively low, as some 1007It is recommended to keep the number of threads relatively low, as some
950Linux kernel versions will scale negatively with the number of threads 1008Linux kernel versions will scale negatively with the number of threads
951(higher parallelity => MUCH higher latency). With current Linux 2.6 1009(higher parallelity => MUCH higher latency). With current Linux 2.6
952versions, 4-32 threads should be fine. 1010versions, 4-32 threads should be fine.
… …
966This module automatically runs C<max_parallel 0> at program end, to ensure 1024This module automatically runs C<max_parallel 0> at program end, to ensure
967that all threads are killed and that there are no outstanding requests. 1025that all threads are killed and that there are no outstanding requests.
968 1026
969Under normal circumstances you don't need to call this function. 1027Under normal circumstances you don't need to call this function.
970 1028
1029=item IO::AIO::max_idle $nthreads
1030
1031Limit the number of threads (default: 4) that are allowed to idle (i.e.,
1032threads that did not get a request to process within 10 seconds). That
1033means if a thread becomes idle while C<$nthreads> other threads are also
1034idle, it will free its resources and exit.
1035
1036This is useful when you allow a large number of threads (e.g. 100 or 1000)
1037to allow for extremely high load situations, but want to free resources
1038under normal circumstances (1000 threads can easily consume 30MB of RAM).
1039
1040The default is probably ok in most situations, especially if thread
1041creation is fast. If thread creation is very slow on your system you might
1042want to use larger values.
1043
971=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs 1044=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs
972 1045
973This is a very bad function to use in interactive programs because it 1046This 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 1047blocks, and a bad way to reduce concurrency because it is inexact: Better
975use an C<aio_group> together with a feed callback. 1048use an C<aio_group> together with a feed callback.
… …
983number of outstanding requests. 1056number of outstanding requests.
984 1057
985You can still queue as many requests as you want. Therefore, 1058You can still queue as many requests as you want. Therefore,
986C<max_oustsanding> is mainly useful in simple scripts (with low values) or 1059C<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). 1060as a stop gap to shield against fatal memory overflow (with large values).
1061
1062=head3 STATISTICAL INFORMATION
1063
1064=item IO::AIO::nreqs
1065
1066Returns the number of requests currently in the ready, execute or pending
1067states (i.e. for which their callback has not been invoked yet).
1068
1069Example: wait till there are no outstanding requests anymore:
1070
1071 IO::AIO::poll_wait, IO::AIO::poll_cb
1072 while IO::AIO::nreqs;
1073
1074=item IO::AIO::nready
1075
1076Returns the number of requests currently in the ready state (not yet
1077executed).
1078
1079=item IO::AIO::npending
1080
1081Returns the number of requests currently in the pending state (executed,
1082but not yet processed by poll_cb).
988 1083
989=back 1084=back
990 1085
991=cut 1086=cut
992 1087

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