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50 50
51=head1 DESCRIPTION 51=head1 DESCRIPTION
52 52
53This module implements asynchronous I/O using whatever means your 53This module implements asynchronous I/O using whatever means your
54operating system supports. 54operating system supports.
55
56Asynchronous means that operations that can normally block your program
57(e.g. reading from disk) will be done asynchronously: the operation
58will still block, but you can do something else in the meantime. This
59is extremely useful for programs that need to stay interactive even
60when doing heavy I/O (GUI programs, high performance network servers
61etc.), but can also be used to easily do operations in parallel that are
62normally done sequentially, e.g. stat'ing many files, which is much faster
63on a RAID volume or over NFS when you do a number of stat operations
64concurrently.
65
66While this works on all types of file descriptors (for example sockets),
67using these functions on file descriptors that support nonblocking
68operation (again, sockets, pipes etc.) is very inefficient. Use an event
69loop for that (such as the L<Event|Event> module): IO::AIO will naturally
70fit into such an event loop itself.
55 71
56In this version, a number of threads are started that execute your 72In this version, a number of threads are started that execute your
57requests and signal their completion. You don't need thread support 73requests and signal their completion. You don't need thread support
58in perl, and the threads created by this module will not be visible 74in perl, and the threads created by this module will not be visible
59to perl. In the future, this module might make use of the native aio 75to perl. In the future, this module might make use of the native aio
60functions available on many operating systems. However, they are often 76functions available on many operating systems. However, they are often
61not well-supported or restricted (Linux doesn't allow them on normal 77not well-supported or restricted (GNU/Linux doesn't allow them on normal
62files currently, for example), and they would only support aio_read and 78files currently, for example), and they would only support aio_read and
63aio_write, so the remaining functionality would have to be implemented 79aio_write, so the remaining functionality would have to be implemented
64using threads anyway. 80using threads anyway.
65 81
66Although the module will work with in the presence of other (Perl-) 82Although the module will work with in the presence of other (Perl-)
67threads, it is currently not reentrant in any way, so use appropriate 83threads, it is currently not reentrant in any way, so use appropriate
68locking 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
69never call C<poll_cb> (or other C<aio_> functions) recursively. 85never call C<poll_cb> (or other C<aio_> functions) recursively.
70 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
71=head1 REQUEST ANATOMY AND LIFETIME 131=head1 REQUEST ANATOMY AND LIFETIME
72 132
73Every 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
74directly visible to Perl. 134directly visible to Perl.
75 135
… …
126use strict 'vars'; 186use strict 'vars';
127 187
128use base 'Exporter'; 188use base 'Exporter';
129 189
130BEGIN { 190BEGIN {
131 our $VERSION = '2.0'; 191 our $VERSION = '2.1';
132 192
133 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
134 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
135 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
136 aio_group aio_nop); 196 aio_copy aio_group aio_nop aio_mknod);
137 our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice)); 197 our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
138 our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush 198 our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
139 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);
140 202
141 @IO::AIO::GRP::ISA = 'IO::AIO::REQ'; 203 @IO::AIO::GRP::ISA = 'IO::AIO::REQ';
142 204
143 require XSLoader; 205 require XSLoader;
144 XSLoader::load ("IO::AIO", $VERSION); 206 XSLoader::load ("IO::AIO", $VERSION);
145} 207}
146 208
147=head1 FUNCTIONS 209=head1 FUNCTIONS
148 210
149=head2 AIO FUNCTIONS 211=head2 AIO REQUEST FUNCTIONS
150 212
151All the C<aio_*> calls are more or less thin wrappers around the syscall 213All the C<aio_*> calls are more or less thin wrappers around the syscall
152with the same name (sans C<aio_>). The arguments are similar or identical, 214with the same name (sans C<aio_>). The arguments are similar or identical,
153and they all accept an additional (and optional) C<$callback> argument 215and they all accept an additional (and optional) C<$callback> argument
154which 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
… …
157syscall has been executed asynchronously. 219syscall has been executed asynchronously.
158 220
159All functions expecting a filehandle keep a copy of the filehandle 221All functions expecting a filehandle keep a copy of the filehandle
160internally until the request has finished. 222internally until the request has finished.
161 223
162All 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
163manipulation of those requests while they are in-flight. 225further manipulation of those requests while they are in-flight.
164 226
165The pathnames you pass to these routines I<must> be absolute and 227The pathnames you pass to these routines I<must> be absolute and
166encoded 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
167request is being executed, the current working directory could have 229request is being executed, the current working directory could have
168changed. Alternatively, you can make sure that you never change the 230changed. Alternatively, you can make sure that you never change the
169current working directory. 231current working directory anywhere in the program and then use relative
232paths.
170 233
171To encode pathnames to byte form, either make sure you either: a) 234To encode pathnames as octets, either make sure you either: a) always pass
172always pass in filenames you got from outside (command line, readdir 235in filenames you got from outside (command line, readdir etc.) without
173etc.), 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
174your 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
175environment, d) use Glib::filename_from_unicode on unicode filenames or e) 238environment, d) use Glib::filename_from_unicode on unicode filenames or e)
176use 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.
177 243
178=over 4 244=over 4
179 245
180=item $prev_pri = aioreq_pri [$pri] 246=item $prev_pri = aioreq_pri [$pri]
181 247
… …
204 }; 270 };
205 271
206=item aioreq_nice $pri_adjust 272=item aioreq_nice $pri_adjust
207 273
208Similar 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
209priority, so effects are cumulative. 275priority, so the effect is cumulative.
210 276
211=item aio_open $pathname, $flags, $mode, $callback->($fh) 277=item aio_open $pathname, $flags, $mode, $callback->($fh)
212 278
213Asynchronously 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
214created filehandle for the file. 280created filehandle for the file.
… …
264 330
265 aio_read $fh, 7, 15, $buffer, 0, sub { 331 aio_read $fh, 7, 15, $buffer, 0, sub {
266 $_[0] > 0 or die "read error: $!"; 332 $_[0] > 0 or die "read error: $!";
267 print "read $_[0] bytes: <$buffer>\n"; 333 print "read $_[0] bytes: <$buffer>\n";
268 }; 334 };
269
270=item aio_move $srcpath, $dstpath, $callback->($status)
271
272Try to move the I<file> (directories not supported as either source or
273destination) from C<$srcpath> to C<$dstpath> and call the callback with
274the C<0> (error) or C<-1> ok.
275
276This is a composite request that tries to rename(2) the file first. If
277rename files with C<EXDEV>, it creates the destination file with mode 0200
278and copies the contents of the source file into it using C<aio_sendfile>,
279followed by restoring atime, mtime, access mode and uid/gid, in that
280order, and unlinking the C<$srcpath>.
281
282If an error occurs, the partial destination file will be unlinked, if
283possible, except when setting atime, mtime, access mode and uid/gid, where
284errors are being ignored.
285
286=cut
287
288sub aio_move($$$) {
289 my ($src, $dst, $cb) = @_;
290
291 my $pri = aioreq_pri;
292 my $grp = aio_group $cb;
293
294 aioreq_pri $pri;
295 add $grp aio_rename $src, $dst, sub {
296 if ($_[0] && $! == EXDEV) {
297 aioreq_pri $pri;
298 add $grp aio_open $src, O_RDONLY, 0, sub {
299 if (my $src_fh = $_[0]) {
300 my @stat = stat $src_fh;
301
302 aioreq_pri $pri;
303 add $grp aio_open $dst, O_WRONLY, 0200, sub {
304 if (my $dst_fh = $_[0]) {
305 aioreq_pri $pri;
306 add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
307 close $src_fh;
308
309 if ($_[0] == $stat[7]) {
310 utime $stat[8], $stat[9], $dst;
311 chmod $stat[2] & 07777, $dst_fh;
312 chown $stat[4], $stat[5], $dst_fh;
313 close $dst_fh;
314
315 aioreq_pri $pri;
316 add $grp aio_unlink $src, sub {
317 $grp->result ($_[0]);
318 };
319 } else {
320 my $errno = $!;
321 aioreq_pri $pri;
322 add $grp aio_unlink $dst, sub {
323 $! = $errno;
324 $grp->result (-1);
325 };
326 }
327 };
328 } else {
329 $grp->result (-1);
330 }
331 },
332
333 } else {
334 $grp->result (-1);
335 }
336 };
337 } else {
338 $grp->result ($_[0]);
339 }
340 };
341
342 $grp
343}
344 335
345=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval) 336=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
346 337
347Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts 338Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
348reading at byte offset C<$in_offset>, and starts writing at the current 339reading at byte offset C<$in_offset>, and starts writing at the current
… …
404=item aio_unlink $pathname, $callback->($status) 395=item aio_unlink $pathname, $callback->($status)
405 396
406Asynchronously unlink (delete) a file and call the callback with the 397Asynchronously unlink (delete) a file and call the callback with the
407result code. 398result code.
408 399
400=item aio_mknod $path, $mode, $dev, $callback->($status)
401
402[EXPERIMENTAL]
403
404Asynchronously create a device node (or fifo). See mknod(2).
405
406The only (POSIX-) portable way of calling this function is:
407
408 aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...
409
409=item aio_link $srcpath, $dstpath, $callback->($status) 410=item aio_link $srcpath, $dstpath, $callback->($status)
410 411
411Asynchronously create a new link to the existing object at C<$srcpath> at 412Asynchronously create a new link to the existing object at C<$srcpath> at
412the path C<$dstpath> and call the callback with the result code. 413the path C<$dstpath> and call the callback with the result code.
413 414
… …
432directory (i.e. opendir + readdir + closedir). The entries will not be 433directory (i.e. opendir + readdir + closedir). The entries will not be
433sorted, and will B<NOT> include the C<.> and C<..> entries. 434sorted, and will B<NOT> include the C<.> and C<..> entries.
434 435
435The callback a single argument which is either C<undef> or an array-ref 436The callback a single argument which is either C<undef> or an array-ref
436with the filenames. 437with the filenames.
438
439=item aio_copy $srcpath, $dstpath, $callback->($status)
440
441Try to copy the I<file> (directories not supported as either source or
442destination) from C<$srcpath> to C<$dstpath> and call the callback with
443the C<0> (error) or C<-1> ok.
444
445This is a composite request that it creates the destination file with
446mode 0200 and copies the contents of the source file into it using
447C<aio_sendfile>, followed by restoring atime, mtime, access mode and
448uid/gid, in that order.
449
450If an error occurs, the partial destination file will be unlinked, if
451possible, except when setting atime, mtime, access mode and uid/gid, where
452errors are being ignored.
453
454=cut
455
456sub aio_copy($$;$) {
457 my ($src, $dst, $cb) = @_;
458
459 my $pri = aioreq_pri;
460 my $grp = aio_group $cb;
461
462 aioreq_pri $pri;
463 add $grp aio_open $src, O_RDONLY, 0, sub {
464 if (my $src_fh = $_[0]) {
465 my @stat = stat $src_fh;
466
467 aioreq_pri $pri;
468 add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
469 if (my $dst_fh = $_[0]) {
470 aioreq_pri $pri;
471 add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
472 if ($_[0] == $stat[7]) {
473 $grp->result (0);
474 close $src_fh;
475
476 # those should not normally block. should. should.
477 utime $stat[8], $stat[9], $dst;
478 chmod $stat[2] & 07777, $dst_fh;
479 chown $stat[4], $stat[5], $dst_fh;
480 close $dst_fh;
481 } else {
482 $grp->result (-1);
483 close $src_fh;
484 close $dst_fh;
485
486 aioreq $pri;
487 add $grp aio_unlink $dst;
488 }
489 };
490 } else {
491 $grp->result (-1);
492 }
493 },
494
495 } else {
496 $grp->result (-1);
497 }
498 };
499
500 $grp
501}
502
503=item aio_move $srcpath, $dstpath, $callback->($status)
504
505Try to move the I<file> (directories not supported as either source or
506destination) from C<$srcpath> to C<$dstpath> and call the callback with
507the C<0> (error) or C<-1> ok.
508
509This is a composite request that tries to rename(2) the file first. If
510rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if
511that is successful, unlinking the C<$srcpath>.
512
513=cut
514
515sub aio_move($$;$) {
516 my ($src, $dst, $cb) = @_;
517
518 my $pri = aioreq_pri;
519 my $grp = aio_group $cb;
520
521 aioreq_pri $pri;
522 add $grp aio_rename $src, $dst, sub {
523 if ($_[0] && $! == EXDEV) {
524 aioreq_pri $pri;
525 add $grp aio_copy $src, $dst, sub {
526 $grp->result ($_[0]);
527
528 if (!$_[0]) {
529 aioreq_pri $pri;
530 add $grp aio_unlink $src;
531 }
532 };
533 } else {
534 $grp->result ($_[0]);
535 }
536 };
537
538 $grp
539}
437 540
438=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs) 541=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
439 542
440Scans a directory (similar to C<aio_readdir>) but additionally tries to 543Scans a directory (similar to C<aio_readdir>) but additionally tries to
441efficiently separate the entries of directory C<$path> into two sets of 544efficiently separate the entries of directory C<$path> into two sets of
… …
794 897
795=back 898=back
796 899
797=head2 SUPPORT FUNCTIONS 900=head2 SUPPORT FUNCTIONS
798 901
902=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
903
799=over 4 904=over 4
800 905
801=item $fileno = IO::AIO::poll_fileno 906=item $fileno = IO::AIO::poll_fileno
802 907
803Return the I<request result pipe file descriptor>. This filehandle must be 908Return the I<request result pipe file descriptor>. This filehandle must be
… …
807 912
808See C<poll_cb> for an example. 913See C<poll_cb> for an example.
809 914
810=item IO::AIO::poll_cb 915=item IO::AIO::poll_cb
811 916
812Process 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
813regularly. Returns the number of events processed. Returns immediately 918regularly. Returns the number of events processed. Returns immediately
814when 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>.
815 921
816If not all requests were processed for whatever reason, the filehandle 922If not all requests were processed for whatever reason, the filehandle
817will still be ready when C<poll_cb> returns. 923will still be ready when C<poll_cb> returns.
818 924
819Example: Install an Event watcher that automatically calls 925Example: Install an Event watcher that automatically calls
… …
821 927
822 Event->io (fd => IO::AIO::poll_fileno, 928 Event->io (fd => IO::AIO::poll_fileno,
823 poll => 'r', async => 1, 929 poll => 'r', async => 1,
824 cb => \&IO::AIO::poll_cb); 930 cb => \&IO::AIO::poll_cb);
825 931
826=item IO::AIO::poll_some $max_requests 932=item IO::AIO::max_poll_reqs $nreqs
827 933
828Similar to C<poll_cb>, but only processes up to C<$max_requests> requests 934=item IO::AIO::max_poll_time $seconds
829at a time.
830 935
831Useful if you want to ensure some level of interactiveness when perl is 936These set the maximum number of requests (default C<0>, meaning infinity)
832not 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.
833 947
834Example: Install an Event watcher that automatically calls 948Example: Install an Event watcher that automatically calls
835IO::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
836program get the CPU sometimes even under high AIO load. 950program get the CPU sometimes even under high AIO load.
837 951
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
838 Event->io (fd => IO::AIO::poll_fileno, 956 Event->io (fd => IO::AIO::poll_fileno,
839 poll => 'r', nice => 1, 957 poll => 'r', nice => 1,
840 cb => sub { IO::AIO::poll_some 256 }); 958 cb => &IO::AIO::poll_cb);
841 959
842=item IO::AIO::poll_wait 960=item IO::AIO::poll_wait
843 961
844Wait till the result filehandle becomes ready for reading (simply does a 962Wait till the result filehandle becomes ready for reading (simply does a
845C<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
846for some requests to finish). 964wait for some requests to finish).
847 965
848See C<nreqs> for an example. 966See C<nreqs> for an example.
849 967
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
850=item IO::AIO::nreqs 977=item IO::AIO::flush
851 978
852Returns the number of requests currently in the ready, execute or pending 979Wait till all outstanding AIO requests have been handled.
853states (i.e. for which their callback has not been invoked yet).
854 980
855Example: wait till there are no outstanding requests anymore: 981Strictly equivalent to:
856 982
857 IO::AIO::poll_wait, IO::AIO::poll_cb 983 IO::AIO::poll_wait, IO::AIO::poll_cb
858 while IO::AIO::nreqs; 984 while IO::AIO::nreqs;
859 985
860=item IO::AIO::nready 986=head3 CONTROLLING THE NUMBER OF THREADS
861
862Returns the number of requests currently in the ready state (not yet
863executed).
864
865=item IO::AIO::npending
866
867Returns the number of requests currently in the pending state (executed,
868but not yet processed by poll_cb).
869
870=item IO::AIO::flush
871
872Wait till all outstanding AIO requests have been handled.
873
874Strictly equivalent to:
875
876 IO::AIO::poll_wait, IO::AIO::poll_cb
877 while IO::AIO::nreqs;
878
879=item IO::AIO::poll
880
881Waits until some requests have been handled.
882
883Strictly equivalent to:
884
885 IO::AIO::poll_wait, IO::AIO::poll_cb
886 if IO::AIO::nreqs;
887 987
888=item IO::AIO::min_parallel $nthreads 988=item IO::AIO::min_parallel $nthreads
889 989
890Set the minimum number of AIO threads to C<$nthreads>. The current 990Set the minimum number of AIO threads to C<$nthreads>. The current
891default is C<8>, which means eight asynchronous operations can execute 991default is C<8>, which means eight asynchronous operations can execute
892concurrently at any one time (the number of outstanding requests, 992concurrently at any one time (the number of outstanding requests,
893however, is unlimited). 993however, is unlimited).
894 994
895IO::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
896no 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.
897 999
898It 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
899Linux kernel versions will scale negatively with the number of threads 1001Linux kernel versions will scale negatively with the number of threads
900(higher parallelity => MUCH higher latency). With current Linux 2.6 1002(higher parallelity => MUCH higher latency). With current Linux 2.6
901versions, 4-32 threads should be fine. 1003versions, 4-32 threads should be fine.
… …
915This 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
916that all threads are killed and that there are no outstanding requests. 1018that all threads are killed and that there are no outstanding requests.
917 1019
918Under normal circumstances you don't need to call this function. 1020Under normal circumstances you don't need to call this function.
919 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
920=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs 1037=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs
921 1038
922This is a very bad function to use in interactive programs because it 1039This is a very bad function to use in interactive programs because it
923blocks, and a bad way to reduce concurrency because it is inexact: Better 1040blocks, and a bad way to reduce concurrency because it is inexact: Better
924use an C<aio_group> together with a feed callback. 1041use an C<aio_group> together with a feed callback.
… …
933 1050
934You can still queue as many requests as you want. Therefore, 1051You can still queue as many requests as you want. Therefore,
935C<max_oustsanding> is mainly useful in simple scripts (with low values) or 1052C<max_oustsanding> is mainly useful in simple scripts (with low values) or
936as a stop gap to shield against fatal memory overflow (with large values). 1053as a stop gap to shield against fatal memory overflow (with large values).
937 1054
1055=head3 STATISTICAL INFORMATION
1056
1057=item IO::AIO::nreqs
1058
1059Returns the number of requests currently in the ready, execute or pending
1060states (i.e. for which their callback has not been invoked yet).
1061
1062Example: wait till there are no outstanding requests anymore:
1063
1064 IO::AIO::poll_wait, IO::AIO::poll_cb
1065 while IO::AIO::nreqs;
1066
1067=item IO::AIO::nready
1068
1069Returns the number of requests currently in the ready state (not yet
1070executed).
1071
1072=item IO::AIO::npending
1073
1074Returns the number of requests currently in the pending state (executed,
1075but not yet processed by poll_cb).
1076
938=back 1077=back
939 1078
940=cut 1079=cut
941 1080
942# support function to convert a fd into a perl filehandle 1081# support function to convert a fd into a perl filehandle
… …
954 1093
955 *$sym 1094 *$sym
956} 1095}
957 1096
958min_parallel 8; 1097min_parallel 8;
1098
1099END {
1100 min_parallel 1;
1101 flush;
1102};
959 1103
9601; 11041;
961 1105
962=head2 FORK BEHAVIOUR 1106=head2 FORK BEHAVIOUR
963 1107

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