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Revision 1.94 by root, Wed Nov 8 02:01:02 2006 UTC

5=head1 SYNOPSIS 5=head1 SYNOPSIS
6 6
7 use IO::AIO; 7 use IO::AIO;
8 8
9 aio_open "/etc/passwd", O_RDONLY, 0, sub { 9 aio_open "/etc/passwd", O_RDONLY, 0, sub {
10 my ($fh) = @_; 10 my $fh = shift
11 or die "/etc/passwd: $!";
11 ... 12 ...
12 }; 13 };
13 14
14 aio_unlink "/tmp/file", sub { }; 15 aio_unlink "/tmp/file", sub { };
15 16
50 51
51=head1 DESCRIPTION 52=head1 DESCRIPTION
52 53
53This module implements asynchronous I/O using whatever means your 54This module implements asynchronous I/O using whatever means your
54operating system supports. 55operating system supports.
56
57Asynchronous means that operations that can normally block your program
58(e.g. reading from disk) will be done asynchronously: the operation
59will still block, but you can do something else in the meantime. This
60is extremely useful for programs that need to stay interactive even
61when doing heavy I/O (GUI programs, high performance network servers
62etc.), but can also be used to easily do operations in parallel that are
63normally done sequentially, e.g. stat'ing many files, which is much faster
64on a RAID volume or over NFS when you do a number of stat operations
65concurrently.
66
67While most of this works on all types of file descriptors (for example
68sockets), using these functions on file descriptors that support
69nonblocking operation (again, sockets, pipes etc.) is very inefficient or
70might not work (aio_read fails on sockets/pipes/fifos). Use an event loop
71for that (such as the L<Event|Event> module): IO::AIO will naturally fit
72into such an event loop itself.
55 73
56In this version, a number of threads are started that execute your 74In this version, a number of threads are started that execute your
57requests and signal their completion. You don't need thread support 75requests and signal their completion. You don't need thread support
58in perl, and the threads created by this module will not be visible 76in 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 77to perl. In the future, this module might make use of the native aio
60functions available on many operating systems. However, they are often 78functions available on many operating systems. However, they are often
61not well-supported or restricted (Linux doesn't allow them on normal 79not well-supported or restricted (GNU/Linux doesn't allow them on normal
62files currently, for example), and they would only support aio_read and 80files currently, for example), and they would only support aio_read and
63aio_write, so the remaining functionality would have to be implemented 81aio_write, so the remaining functionality would have to be implemented
64using threads anyway. 82using threads anyway.
65 83
66Although the module will work with in the presence of other (Perl-) 84Although the module will work with in the presence of other (Perl-)
67threads, it is currently not reentrant in any way, so use appropriate 85threads, it is currently not reentrant in any way, so use appropriate
68locking yourself, always call C<poll_cb> from within the same thread, or 86locking yourself, always call C<poll_cb> from within the same thread, or
69never call C<poll_cb> (or other C<aio_> functions) recursively. 87never call C<poll_cb> (or other C<aio_> functions) recursively.
70 88
89=head2 EXAMPLE
90
91This is a simple example that uses the Event module and loads
92F</etc/passwd> asynchronously:
93
94 use Fcntl;
95 use Event;
96 use IO::AIO;
97
98 # register the IO::AIO callback with Event
99 Event->io (fd => IO::AIO::poll_fileno,
100 poll => 'r',
101 cb => \&IO::AIO::poll_cb);
102
103 # queue the request to open /etc/passwd
104 aio_open "/etc/passwd", O_RDONLY, 0, sub {
105 my $fh = shift
106 or die "error while opening: $!";
107
108 # stat'ing filehandles is generally non-blocking
109 my $size = -s $fh;
110
111 # queue a request to read the file
112 my $contents;
113 aio_read $fh, 0, $size, $contents, 0, sub {
114 $_[0] == $size
115 or die "short read: $!";
116
117 close $fh;
118
119 # file contents now in $contents
120 print $contents;
121
122 # exit event loop and program
123 Event::unloop;
124 };
125 };
126
127 # possibly queue up other requests, or open GUI windows,
128 # check for sockets etc. etc.
129
130 # process events as long as there are some:
131 Event::loop;
132
71=head1 REQUEST ANATOMY AND LIFETIME 133=head1 REQUEST ANATOMY AND LIFETIME
72 134
73Every C<aio_*> function creates a request. which is a C data structure not 135Every C<aio_*> function creates a request. which is a C data structure not
74directly visible to Perl. 136directly visible to Perl.
75 137
116Request has reached the end of its lifetime and holds no resources anymore 178Request has reached the end of its lifetime and holds no resources anymore
117(except possibly for the Perl object, but its connection to the actual 179(except possibly for the Perl object, but its connection to the actual
118aio request is severed and calling its methods will either do nothing or 180aio request is severed and calling its methods will either do nothing or
119result in a runtime error). 181result in a runtime error).
120 182
183=back
184
121=cut 185=cut
122 186
123package IO::AIO; 187package IO::AIO;
124 188
125no warnings; 189no warnings;
126use strict 'vars'; 190use strict 'vars';
127 191
128use base 'Exporter'; 192use base 'Exporter';
129 193
130BEGIN { 194BEGIN {
131 our $VERSION = '2.0'; 195 our $VERSION = '2.2';
132 196
133 our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close aio_stat 197 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 198 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 199 aio_readlink aio_fsync aio_fdatasync aio_readahead aio_rename aio_link
136 aio_group aio_nop); 200 aio_move aio_copy aio_group aio_nop aio_mknod);
137 our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice)); 201 our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
138 our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush 202 our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
139 min_parallel max_parallel nreqs); 203 min_parallel max_parallel max_idle
204 nreqs nready npending nthreads
205 max_poll_time max_poll_reqs);
140 206
141 @IO::AIO::GRP::ISA = 'IO::AIO::REQ'; 207 @IO::AIO::GRP::ISA = 'IO::AIO::REQ';
142 208
143 require XSLoader; 209 require XSLoader;
144 XSLoader::load ("IO::AIO", $VERSION); 210 XSLoader::load ("IO::AIO", $VERSION);
145} 211}
146 212
147=head1 FUNCTIONS 213=head1 FUNCTIONS
148 214
149=head2 AIO FUNCTIONS 215=head2 AIO REQUEST FUNCTIONS
150 216
151All the C<aio_*> calls are more or less thin wrappers around the syscall 217All the C<aio_*> calls are more or less thin wrappers around the syscall
152with the same name (sans C<aio_>). The arguments are similar or identical, 218with the same name (sans C<aio_>). The arguments are similar or identical,
153and they all accept an additional (and optional) C<$callback> argument 219and they all accept an additional (and optional) C<$callback> argument
154which must be a code reference. This code reference will get called with 220which must be a code reference. This code reference will get called with
157syscall has been executed asynchronously. 223syscall has been executed asynchronously.
158 224
159All functions expecting a filehandle keep a copy of the filehandle 225All functions expecting a filehandle keep a copy of the filehandle
160internally until the request has finished. 226internally until the request has finished.
161 227
162All requests return objects of type L<IO::AIO::REQ> that allow further 228All functions return request objects of type L<IO::AIO::REQ> that allow
163manipulation of those requests while they are in-flight. 229further manipulation of those requests while they are in-flight.
164 230
165The pathnames you pass to these routines I<must> be absolute and 231The 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 232encoded as octets. The reason for the former is that at the time the
167request is being executed, the current working directory could have 233request is being executed, the current working directory could have
168changed. Alternatively, you can make sure that you never change the 234changed. Alternatively, you can make sure that you never change the
169current working directory. 235current working directory anywhere in the program and then use relative
236paths.
170 237
171To encode pathnames to byte form, either make sure you either: a) 238To encode pathnames as octets, either make sure you either: a) always pass
172always pass in filenames you got from outside (command line, readdir 239in 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 240tinkering, 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 241your pathnames to the locale (or other) encoding in effect in the user
175environment, d) use Glib::filename_from_unicode on unicode filenames or e) 242environment, d) use Glib::filename_from_unicode on unicode filenames or e)
176use something else. 243use something else to ensure your scalar has the correct contents.
244
245This works, btw. independent of the internal UTF-8 bit, which IO::AIO
246handles correctly wether it is set or not.
177 247
178=over 4 248=over 4
179 249
180=item aioreq_pri $pri 250=item $prev_pri = aioreq_pri [$pri]
181 251
182Sets the priority for the next aio request. The default priority 252Returns the priority value that would be used for the next request and, if
253C<$pri> is given, sets the priority for the next aio request.
254
183is C<0>, the minimum and maximum priorities are C<-4> and C<4>, 255The default priority is C<0>, the minimum and maximum priorities are C<-4>
184respectively. Requests with higher priority will be serviced first. 256and C<4>, respectively. Requests with higher priority will be serviced
257first.
185 258
186The priority will be reset to C<0> after each call to one of the C<aio_> 259The priority will be reset to C<0> after each call to one of the C<aio_*>
187functions. 260functions.
188 261
189Example: open a file with low priority, then read something from it with 262Example: open a file with low priority, then read something from it with
190higher priority so the read request is serviced before other low priority 263higher priority so the read request is serviced before other low priority
191open requests (potentially spamming the cache): 264open requests (potentially spamming the cache):
201 }; 274 };
202 275
203=item aioreq_nice $pri_adjust 276=item aioreq_nice $pri_adjust
204 277
205Similar to C<aioreq_pri>, but subtracts the given value from the current 278Similar to C<aioreq_pri>, but subtracts the given value from the current
206priority, so effects are cumulative. 279priority, so the effect is cumulative.
207 280
208=item aio_open $pathname, $flags, $mode, $callback->($fh) 281=item aio_open $pathname, $flags, $mode, $callback->($fh)
209 282
210Asynchronously open or create a file and call the callback with a newly 283Asynchronously open or create a file and call the callback with a newly
211created filehandle for the file. 284created filehandle for the file.
261 334
262 aio_read $fh, 7, 15, $buffer, 0, sub { 335 aio_read $fh, 7, 15, $buffer, 0, sub {
263 $_[0] > 0 or die "read error: $!"; 336 $_[0] > 0 or die "read error: $!";
264 print "read $_[0] bytes: <$buffer>\n"; 337 print "read $_[0] bytes: <$buffer>\n";
265 }; 338 };
266
267=item aio_move $srcpath, $dstpath, $callback->($status)
268
269Try to move the I<file> (directories not supported as either source or
270destination) from C<$srcpath> to C<$dstpath> and call the callback with
271the C<0> (error) or C<-1> ok.
272
273This is a composite request that tries to rename(2) the file first. If
274rename files with C<EXDEV>, it creates the destination file with mode 0200
275and copies the contents of the source file into it using C<aio_sendfile>,
276followed by restoring atime, mtime, access mode and uid/gid, in that
277order, and unlinking the C<$srcpath>.
278
279If an error occurs, the partial destination file will be unlinked, if
280possible, except when setting atime, mtime, access mode and uid/gid, where
281errors are being ignored.
282
283=cut
284
285sub aio_move($$$) {
286 my ($src, $dst, $cb) = @_;
287
288 my $grp = aio_group $cb;
289
290 add $grp aio_rename $src, $dst, sub {
291 if ($_[0] && $! == EXDEV) {
292 add $grp aio_open $src, O_RDONLY, 0, sub {
293 if (my $src_fh = $_[0]) {
294 my @stat = stat $src_fh;
295
296 add $grp aio_open $dst, O_WRONLY, 0200, sub {
297 if (my $dst_fh = $_[0]) {
298 add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
299 close $src_fh;
300
301 if ($_[0] == $stat[7]) {
302 utime $stat[8], $stat[9], $dst;
303 chmod $stat[2] & 07777, $dst_fh;
304 chown $stat[4], $stat[5], $dst_fh;
305 close $dst_fh;
306
307 add $grp aio_unlink $src, sub {
308 $grp->result ($_[0]);
309 };
310 } else {
311 my $errno = $!;
312 add $grp aio_unlink $dst, sub {
313 $! = $errno;
314 $grp->result (-1);
315 };
316 }
317 };
318 } else {
319 $grp->result (-1);
320 }
321 },
322
323 } else {
324 $grp->result (-1);
325 }
326 };
327 } else {
328 $grp->result ($_[0]);
329 }
330 };
331
332 $grp
333}
334 339
335=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval) 340=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
336 341
337Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts 342Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
338reading at byte offset C<$in_offset>, and starts writing at the current 343reading at byte offset C<$in_offset>, and starts writing at the current
394=item aio_unlink $pathname, $callback->($status) 399=item aio_unlink $pathname, $callback->($status)
395 400
396Asynchronously unlink (delete) a file and call the callback with the 401Asynchronously unlink (delete) a file and call the callback with the
397result code. 402result code.
398 403
404=item aio_mknod $path, $mode, $dev, $callback->($status)
405
406[EXPERIMENTAL]
407
408Asynchronously create a device node (or fifo). See mknod(2).
409
410The only (POSIX-) portable way of calling this function is:
411
412 aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...
413
399=item aio_link $srcpath, $dstpath, $callback->($status) 414=item aio_link $srcpath, $dstpath, $callback->($status)
400 415
401Asynchronously create a new link to the existing object at C<$srcpath> at 416Asynchronously create a new link to the existing object at C<$srcpath> at
402the path C<$dstpath> and call the callback with the result code. 417the path C<$dstpath> and call the callback with the result code.
403 418
404=item aio_symlink $srcpath, $dstpath, $callback->($status) 419=item aio_symlink $srcpath, $dstpath, $callback->($status)
405 420
406Asynchronously create a new symbolic link to the existing object at C<$srcpath> at 421Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
407the path C<$dstpath> and call the callback with the result code. 422the path C<$dstpath> and call the callback with the result code.
423
424=item aio_readlink $path, $callback->($link)
425
426Asynchronously read the symlink specified by C<$path> and pass it to
427the callback. If an error occurs, nothing or undef gets passed to the
428callback.
408 429
409=item aio_rename $srcpath, $dstpath, $callback->($status) 430=item aio_rename $srcpath, $dstpath, $callback->($status)
410 431
411Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as 432Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
412rename(2) and call the callback with the result code. 433rename(2) and call the callback with the result code.
422directory (i.e. opendir + readdir + closedir). The entries will not be 443directory (i.e. opendir + readdir + closedir). The entries will not be
423sorted, and will B<NOT> include the C<.> and C<..> entries. 444sorted, and will B<NOT> include the C<.> and C<..> entries.
424 445
425The callback a single argument which is either C<undef> or an array-ref 446The callback a single argument which is either C<undef> or an array-ref
426with the filenames. 447with the filenames.
448
449=item aio_copy $srcpath, $dstpath, $callback->($status)
450
451Try to copy the I<file> (directories not supported as either source or
452destination) from C<$srcpath> to C<$dstpath> and call the callback with
453the C<0> (error) or C<-1> ok.
454
455This is a composite request that it creates the destination file with
456mode 0200 and copies the contents of the source file into it using
457C<aio_sendfile>, followed by restoring atime, mtime, access mode and
458uid/gid, in that order.
459
460If an error occurs, the partial destination file will be unlinked, if
461possible, except when setting atime, mtime, access mode and uid/gid, where
462errors are being ignored.
463
464=cut
465
466sub aio_copy($$;$) {
467 my ($src, $dst, $cb) = @_;
468
469 my $pri = aioreq_pri;
470 my $grp = aio_group $cb;
471
472 aioreq_pri $pri;
473 add $grp aio_open $src, O_RDONLY, 0, sub {
474 if (my $src_fh = $_[0]) {
475 my @stat = stat $src_fh;
476
477 aioreq_pri $pri;
478 add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
479 if (my $dst_fh = $_[0]) {
480 aioreq_pri $pri;
481 add $grp aio_sendfile $dst_fh, $src_fh, 0, $stat[7], sub {
482 if ($_[0] == $stat[7]) {
483 $grp->result (0);
484 close $src_fh;
485
486 # those should not normally block. should. should.
487 utime $stat[8], $stat[9], $dst;
488 chmod $stat[2] & 07777, $dst_fh;
489 chown $stat[4], $stat[5], $dst_fh;
490 close $dst_fh;
491 } else {
492 $grp->result (-1);
493 close $src_fh;
494 close $dst_fh;
495
496 aioreq $pri;
497 add $grp aio_unlink $dst;
498 }
499 };
500 } else {
501 $grp->result (-1);
502 }
503 },
504
505 } else {
506 $grp->result (-1);
507 }
508 };
509
510 $grp
511}
512
513=item aio_move $srcpath, $dstpath, $callback->($status)
514
515Try to move the I<file> (directories not supported as either source or
516destination) from C<$srcpath> to C<$dstpath> and call the callback with
517the C<0> (error) or C<-1> ok.
518
519This is a composite request that tries to rename(2) the file first. If
520rename files with C<EXDEV>, it copies the file with C<aio_copy> and, if
521that is successful, unlinking the C<$srcpath>.
522
523=cut
524
525sub aio_move($$;$) {
526 my ($src, $dst, $cb) = @_;
527
528 my $pri = aioreq_pri;
529 my $grp = aio_group $cb;
530
531 aioreq_pri $pri;
532 add $grp aio_rename $src, $dst, sub {
533 if ($_[0] && $! == EXDEV) {
534 aioreq_pri $pri;
535 add $grp aio_copy $src, $dst, sub {
536 $grp->result ($_[0]);
537
538 if (!$_[0]) {
539 aioreq_pri $pri;
540 add $grp aio_unlink $src;
541 }
542 };
543 } else {
544 $grp->result ($_[0]);
545 }
546 };
547
548 $grp
549}
427 550
428=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs) 551=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
429 552
430Scans a directory (similar to C<aio_readdir>) but additionally tries to 553Scans a directory (similar to C<aio_readdir>) but additionally tries to
431efficiently separate the entries of directory C<$path> into two sets of 554efficiently separate the entries of directory C<$path> into two sets of
433recurse into (everything else, including symlinks to directories). 556recurse into (everything else, including symlinks to directories).
434 557
435C<aio_scandir> is a composite request that creates of many sub requests_ 558C<aio_scandir> is a composite request that creates of many sub requests_
436C<$maxreq> specifies the maximum number of outstanding aio requests that 559C<$maxreq> specifies the maximum number of outstanding aio requests that
437this function generates. If it is C<< <= 0 >>, then a suitable default 560this function generates. If it is C<< <= 0 >>, then a suitable default
438will be chosen (currently 6). 561will be chosen (currently 4).
439 562
440On error, the callback is called without arguments, otherwise it receives 563On error, the callback is called without arguments, otherwise it receives
441two array-refs with path-relative entry names. 564two array-refs with path-relative entry names.
442 565
443Example: 566Example:
480=cut 603=cut
481 604
482sub aio_scandir($$$) { 605sub aio_scandir($$$) {
483 my ($path, $maxreq, $cb) = @_; 606 my ($path, $maxreq, $cb) = @_;
484 607
608 my $pri = aioreq_pri;
609
485 my $grp = aio_group $cb; 610 my $grp = aio_group $cb;
486 611
487 $maxreq = 6 if $maxreq <= 0; 612 $maxreq = 4 if $maxreq <= 0;
488 613
489 # stat once 614 # stat once
615 aioreq_pri $pri;
490 add $grp aio_stat $path, sub { 616 add $grp aio_stat $path, sub {
491 return $grp->result () if $_[0]; 617 return $grp->result () if $_[0];
492 my $now = time; 618 my $now = time;
493 my $hash1 = join ":", (stat _)[0,1,3,7,9]; 619 my $hash1 = join ":", (stat _)[0,1,3,7,9];
494 620
495 # read the directory entries 621 # read the directory entries
622 aioreq_pri $pri;
496 add $grp aio_readdir $path, sub { 623 add $grp aio_readdir $path, sub {
497 my $entries = shift 624 my $entries = shift
498 or return $grp->result (); 625 or return $grp->result ();
499 626
500 # stat the dir another time 627 # stat the dir another time
628 aioreq_pri $pri;
501 add $grp aio_stat $path, sub { 629 add $grp aio_stat $path, sub {
502 my $hash2 = join ":", (stat _)[0,1,3,7,9]; 630 my $hash2 = join ":", (stat _)[0,1,3,7,9];
503 631
504 my $ndirs; 632 my $ndirs;
505 633
529 limit $statgrp $maxreq; 657 limit $statgrp $maxreq;
530 feed $statgrp sub { 658 feed $statgrp sub {
531 return unless @$entries; 659 return unless @$entries;
532 my $entry = pop @$entries; 660 my $entry = pop @$entries;
533 661
662 aioreq_pri $pri;
534 add $statgrp aio_stat "$path/$entry/.", sub { 663 add $statgrp aio_stat "$path/$entry/.", sub {
535 if ($_[0] < 0) { 664 if ($_[0] < 0) {
536 push @nondirs, $entry; 665 push @nondirs, $entry;
537 } else { 666 } else {
538 # need to check for real directory 667 # need to check for real directory
668 aioreq_pri $pri;
539 add $statgrp aio_lstat "$path/$entry", sub { 669 add $statgrp aio_lstat "$path/$entry", sub {
540 if (-d _) { 670 if (-d _) {
541 push @dirs, $entry; 671 push @dirs, $entry;
542 672
543 unless (--$ndirs) { 673 unless (--$ndirs) {
714itself. Useful when you queued a lot of events but got a result early. 844itself. Useful when you queued a lot of events but got a result early.
715 845
716=item $grp->result (...) 846=item $grp->result (...)
717 847
718Set the result value(s) that will be passed to the group callback when all 848Set the result value(s) that will be passed to the group callback when all
719subrequests have finished. By default, no argument will be passed. 849subrequests have finished and set thre groups errno to the current value
850of errno (just like calling C<errno> without an error number). By default,
851no argument will be passed and errno is zero.
852
853=item $grp->errno ([$errno])
854
855Sets the group errno value to C<$errno>, or the current value of errno
856when the argument is missing.
857
858Every aio request has an associated errno value that is restored when
859the callback is invoked. This method lets you change this value from its
860default (0).
861
862Calling C<result> will also set errno, so make sure you either set C<$!>
863before the call to C<result>, or call c<errno> after it.
720 864
721=item feed $grp $callback->($grp) 865=item feed $grp $callback->($grp)
722 866
723Sets a feeder/generator on this group: every group can have an attached 867Sets a feeder/generator on this group: every group can have an attached
724generator that generates requests if idle. The idea behind this is that, 868generator that generates requests if idle. The idea behind this is that,
763 907
764=back 908=back
765 909
766=head2 SUPPORT FUNCTIONS 910=head2 SUPPORT FUNCTIONS
767 911
912=head3 EVENT PROCESSING AND EVENT LOOP INTEGRATION
913
768=over 4 914=over 4
769 915
770=item $fileno = IO::AIO::poll_fileno 916=item $fileno = IO::AIO::poll_fileno
771 917
772Return the I<request result pipe file descriptor>. This filehandle must be 918Return the I<request result pipe file descriptor>. This filehandle must be
776 922
777See C<poll_cb> for an example. 923See C<poll_cb> for an example.
778 924
779=item IO::AIO::poll_cb 925=item IO::AIO::poll_cb
780 926
781Process all outstanding events on the result pipe. You have to call this 927Process some outstanding events on the result pipe. You have to call this
782regularly. Returns the number of events processed. Returns immediately 928regularly. Returns the number of events processed. Returns immediately
783when no events are outstanding. 929when no events are outstanding. The amount of events processed depends on
930the settings of C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
931
932If not all requests were processed for whatever reason, the filehandle
933will still be ready when C<poll_cb> returns.
784 934
785Example: Install an Event watcher that automatically calls 935Example: Install an Event watcher that automatically calls
786IO::AIO::poll_cb with high priority: 936IO::AIO::poll_cb with high priority:
787 937
788 Event->io (fd => IO::AIO::poll_fileno, 938 Event->io (fd => IO::AIO::poll_fileno,
789 poll => 'r', async => 1, 939 poll => 'r', async => 1,
790 cb => \&IO::AIO::poll_cb); 940 cb => \&IO::AIO::poll_cb);
791 941
942=item IO::AIO::max_poll_reqs $nreqs
943
944=item IO::AIO::max_poll_time $seconds
945
946These set the maximum number of requests (default C<0>, meaning infinity)
947that are being processed by C<IO::AIO::poll_cb> in one call, respectively
948the maximum amount of time (default C<0>, meaning infinity) spent in
949C<IO::AIO::poll_cb> to process requests (more correctly the mininum amount
950of time C<poll_cb> is allowed to use).
951
952Setting C<max_poll_time> to a non-zero value creates an overhead of one
953syscall per request processed, which is not normally a problem unless your
954callbacks are really really fast or your OS is really really slow (I am
955not mentioning Solaris here). Using C<max_poll_reqs> incurs no overhead.
956
957Setting these is useful if you want to ensure some level of
958interactiveness when perl is not fast enough to process all requests in
959time.
960
961For interactive programs, values such as C<0.01> to C<0.1> should be fine.
962
963Example: Install an Event watcher that automatically calls
964IO::AIO::poll_cb with low priority, to ensure that other parts of the
965program get the CPU sometimes even under high AIO load.
966
967 # try not to spend much more than 0.1s in poll_cb
968 IO::AIO::max_poll_time 0.1;
969
970 # use a low priority so other tasks have priority
971 Event->io (fd => IO::AIO::poll_fileno,
972 poll => 'r', nice => 1,
973 cb => &IO::AIO::poll_cb);
974
792=item IO::AIO::poll_wait 975=item IO::AIO::poll_wait
793 976
977If there are any outstanding requests and none of them in the result
794Wait till the result filehandle becomes ready for reading (simply does a 978phase, wait till the result filehandle becomes ready for reading (simply
795C<select> on the filehandle. This is useful if you want to synchronously wait 979does a C<select> on the filehandle. This is useful if you want to
796for some requests to finish). 980synchronously wait for some requests to finish).
797 981
798See C<nreqs> for an example. 982See C<nreqs> for an example.
799 983
984=item IO::AIO::poll
985
986Waits until some requests have been handled.
987
988Returns the number of requests processed, but is otherwise strictly
989equivalent to:
990
991 IO::AIO::poll_wait, IO::AIO::poll_cb
992
800=item IO::AIO::nreqs 993=item IO::AIO::flush
801 994
802Returns the number of requests currently outstanding (i.e. for which their 995Wait till all outstanding AIO requests have been handled.
803callback has not been invoked yet).
804 996
805Example: wait till there are no outstanding requests anymore: 997Strictly equivalent to:
806 998
807 IO::AIO::poll_wait, IO::AIO::poll_cb 999 IO::AIO::poll_wait, IO::AIO::poll_cb
808 while IO::AIO::nreqs; 1000 while IO::AIO::nreqs;
809 1001
810=item IO::AIO::flush 1002=head3 CONTROLLING THE NUMBER OF THREADS
811
812Wait till all outstanding AIO requests have been handled.
813
814Strictly equivalent to:
815
816 IO::AIO::poll_wait, IO::AIO::poll_cb
817 while IO::AIO::nreqs;
818
819=item IO::AIO::poll
820
821Waits until some requests have been handled.
822
823Strictly equivalent to:
824
825 IO::AIO::poll_wait, IO::AIO::poll_cb
826 if IO::AIO::nreqs;
827 1003
828=item IO::AIO::min_parallel $nthreads 1004=item IO::AIO::min_parallel $nthreads
829 1005
830Set the minimum number of AIO threads to C<$nthreads>. The current 1006Set the minimum number of AIO threads to C<$nthreads>. The current
831default is C<8>, which means eight asynchronous operations can execute 1007default is C<8>, which means eight asynchronous operations can execute
832concurrently at any one time (the number of outstanding requests, 1008concurrently at any one time (the number of outstanding requests,
833however, is unlimited). 1009however, is unlimited).
834 1010
835IO::AIO starts threads only on demand, when an AIO request is queued and 1011IO::AIO starts threads only on demand, when an AIO request is queued and
836no free thread exists. 1012no free thread exists. Please note that queueing up a hundred requests can
1013create demand for a hundred threads, even if it turns out that everything
1014is in the cache and could have been processed faster by a single thread.
837 1015
838It is recommended to keep the number of threads relatively low, as some 1016It is recommended to keep the number of threads relatively low, as some
839Linux kernel versions will scale negatively with the number of threads 1017Linux kernel versions will scale negatively with the number of threads
840(higher parallelity => MUCH higher latency). With current Linux 2.6 1018(higher parallelity => MUCH higher latency). With current Linux 2.6
841versions, 4-32 threads should be fine. 1019versions, 4-32 threads should be fine.
855This module automatically runs C<max_parallel 0> at program end, to ensure 1033This module automatically runs C<max_parallel 0> at program end, to ensure
856that all threads are killed and that there are no outstanding requests. 1034that all threads are killed and that there are no outstanding requests.
857 1035
858Under normal circumstances you don't need to call this function. 1036Under normal circumstances you don't need to call this function.
859 1037
1038=item IO::AIO::max_idle $nthreads
1039
1040Limit the number of threads (default: 4) that are allowed to idle (i.e.,
1041threads that did not get a request to process within 10 seconds). That
1042means if a thread becomes idle while C<$nthreads> other threads are also
1043idle, it will free its resources and exit.
1044
1045This is useful when you allow a large number of threads (e.g. 100 or 1000)
1046to allow for extremely high load situations, but want to free resources
1047under normal circumstances (1000 threads can easily consume 30MB of RAM).
1048
1049The default is probably ok in most situations, especially if thread
1050creation is fast. If thread creation is very slow on your system you might
1051want to use larger values.
1052
860=item $oldnreqs = IO::AIO::max_outstanding $nreqs 1053=item $oldmaxreqs = IO::AIO::max_outstanding $maxreqs
861 1054
862[REMOVED] 1055This is a very bad function to use in interactive programs because it
1056blocks, and a bad way to reduce concurrency because it is inexact: Better
1057use an C<aio_group> together with a feed callback.
863 1058
864Pre-2.x versions used max_outstanding for a crude request queue length limit.
865
866In 2.x+ you are advised to use a group and a feeder to limit
867concurrency. The max_outstanding feature ran very unstable (endless
868recursions causing segfaults, bad interaction with groups etc.) and was
869removed.
870
871I am deeply sorry, but I am still on the hunt for a good limiting interface.
872
873Original description was as follows:
874
875Sets the maximum number of outstanding requests to C<$nreqs>. If you try 1059Sets the maximum number of outstanding requests to C<$nreqs>. If you
876to queue up more than this number of requests, the caller will block until 1060to queue up more than this number of requests, the next call to the
877some requests have been handled. 1061C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
1062function will block until the limit is no longer exceeded.
1063
1064The default value is very large, so there is no practical limit on the
1065number of outstanding requests.
1066
1067You can still queue as many requests as you want. Therefore,
1068C<max_oustsanding> is mainly useful in simple scripts (with low values) or
1069as a stop gap to shield against fatal memory overflow (with large values).
1070
1071=head3 STATISTICAL INFORMATION
1072
1073=item IO::AIO::nreqs
1074
1075Returns the number of requests currently in the ready, execute or pending
1076states (i.e. for which their callback has not been invoked yet).
1077
1078Example: wait till there are no outstanding requests anymore:
1079
1080 IO::AIO::poll_wait, IO::AIO::poll_cb
1081 while IO::AIO::nreqs;
1082
1083=item IO::AIO::nready
1084
1085Returns the number of requests currently in the ready state (not yet
1086executed).
1087
1088=item IO::AIO::npending
1089
1090Returns the number of requests currently in the pending state (executed,
1091but not yet processed by poll_cb).
878 1092
879=back 1093=back
880 1094
881=cut 1095=cut
882 1096
897} 1111}
898 1112
899min_parallel 8; 1113min_parallel 8;
900 1114
901END { 1115END {
902 max_parallel 0; 1116 min_parallel 1;
903} 1117 flush;
1118};
904 1119
9051; 11201;
906 1121
907=head2 FORK BEHAVIOUR 1122=head2 FORK BEHAVIOUR
908 1123

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