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Revision 1.151 by root, Fri Jun 12 00:43:16 2009 UTC vs.
Revision 1.199 by root, Wed Jun 29 12:46:36 2011 UTC

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4 4
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", IO::AIO::O_RDONLY, 0, sub {
10 my $fh = shift 10 my $fh = shift
11 or die "/etc/passwd: $!"; 11 or die "/etc/passwd: $!";
12 ... 12 ...
13 }; 13 };
14 14
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26 $req->cancel; # cancel request if still in queue 26 $req->cancel; # cancel request if still in queue
27 27
28 my $grp = aio_group sub { print "all stats done\n" }; 28 my $grp = aio_group sub { print "all stats done\n" };
29 add $grp aio_stat "..." for ...; 29 add $grp aio_stat "..." for ...;
30 30
31 # AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
32 use AnyEvent::AIO;
33
34 # EV integration
35 my $w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
36
37 # Event integration
38 Event->io (fd => IO::AIO::poll_fileno,
39 poll => 'r',
40 cb => \&IO::AIO::poll_cb);
41
42 # Glib/Gtk2 integration
43 add_watch Glib::IO IO::AIO::poll_fileno,
44 in => sub { IO::AIO::poll_cb; 1 };
45
46 # Tk integration
47 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
48 readable => \&IO::AIO::poll_cb);
49
50 # Danga::Socket integration
51 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
52 \&IO::AIO::poll_cb);
53
54=head1 DESCRIPTION 31=head1 DESCRIPTION
55 32
56This module implements asynchronous I/O using whatever means your 33This module implements asynchronous I/O using whatever means your
57operating system supports. 34operating system supports. It is implemented as an interface to C<libeio>
35(L<http://software.schmorp.de/pkg/libeio.html>).
58 36
59Asynchronous means that operations that can normally block your program 37Asynchronous means that operations that can normally block your program
60(e.g. reading from disk) will be done asynchronously: the operation 38(e.g. reading from disk) will be done asynchronously: the operation
61will still block, but you can do something else in the meantime. This 39will still block, but you can do something else in the meantime. This
62is extremely useful for programs that need to stay interactive even 40is extremely useful for programs that need to stay interactive even
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66on a RAID volume or over NFS when you do a number of stat operations 44on a RAID volume or over NFS when you do a number of stat operations
67concurrently. 45concurrently.
68 46
69While most of this works on all types of file descriptors (for 47While most of this works on all types of file descriptors (for
70example sockets), using these functions on file descriptors that 48example sockets), using these functions on file descriptors that
71support nonblocking operation (again, sockets, pipes etc.) is very 49support nonblocking operation (again, sockets, pipes etc.) is
72inefficient. Use an event loop for that (such as the L<Event|Event> 50very inefficient. Use an event loop for that (such as the L<EV>
73module): IO::AIO will naturally fit into such an event loop itself. 51module): IO::AIO will naturally fit into such an event loop itself.
74 52
75In this version, a number of threads are started that execute your 53In this version, a number of threads are started that execute your
76requests and signal their completion. You don't need thread support 54requests and signal their completion. You don't need thread support
77in perl, and the threads created by this module will not be visible 55in perl, and the threads created by this module will not be visible
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87yourself, always call C<poll_cb> from within the same thread, or never 65yourself, always call C<poll_cb> from within the same thread, or never
88call C<poll_cb> (or other C<aio_> functions) recursively. 66call C<poll_cb> (or other C<aio_> functions) recursively.
89 67
90=head2 EXAMPLE 68=head2 EXAMPLE
91 69
92This is a simple example that uses the Event module and loads 70This is a simple example that uses the EV module and loads
93F</etc/passwd> asynchronously: 71F</etc/passwd> asynchronously:
94 72
95 use Fcntl; 73 use Fcntl;
96 use Event; 74 use EV;
97 use IO::AIO; 75 use IO::AIO;
98 76
99 # register the IO::AIO callback with Event 77 # register the IO::AIO callback with EV
100 Event->io (fd => IO::AIO::poll_fileno, 78 my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
101 poll => 'r',
102 cb => \&IO::AIO::poll_cb);
103 79
104 # queue the request to open /etc/passwd 80 # queue the request to open /etc/passwd
105 aio_open "/etc/passwd", O_RDONLY, 0, sub { 81 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
106 my $fh = shift 82 my $fh = shift
107 or die "error while opening: $!"; 83 or die "error while opening: $!";
108 84
109 # stat'ing filehandles is generally non-blocking 85 # stat'ing filehandles is generally non-blocking
110 my $size = -s $fh; 86 my $size = -s $fh;
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119 95
120 # file contents now in $contents 96 # file contents now in $contents
121 print $contents; 97 print $contents;
122 98
123 # exit event loop and program 99 # exit event loop and program
124 Event::unloop; 100 EV::unloop;
125 }; 101 };
126 }; 102 };
127 103
128 # possibly queue up other requests, or open GUI windows, 104 # possibly queue up other requests, or open GUI windows,
129 # check for sockets etc. etc. 105 # check for sockets etc. etc.
130 106
131 # process events as long as there are some: 107 # process events as long as there are some:
132 Event::loop; 108 EV::loop;
133 109
134=head1 REQUEST ANATOMY AND LIFETIME 110=head1 REQUEST ANATOMY AND LIFETIME
135 111
136Every C<aio_*> function creates a request. which is a C data structure not 112Every C<aio_*> function creates a request. which is a C data structure not
137directly visible to Perl. 113directly visible to Perl.
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187 163
188package IO::AIO; 164package IO::AIO;
189 165
190use Carp (); 166use Carp ();
191 167
192no warnings; 168use common::sense;
193use strict 'vars';
194 169
195use base 'Exporter'; 170use base 'Exporter';
196 171
197BEGIN { 172BEGIN {
198 our $VERSION = '3.2'; 173 our $VERSION = '3.92';
199 174
200 our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close 175 our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close
201 aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir aio_readdirx 176 aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir aio_readdirx
202 aio_scandir aio_symlink aio_readlink aio_sync aio_fsync 177 aio_scandir aio_symlink aio_readlink aio_sync aio_fsync
203 aio_fdatasync aio_sync_file_range aio_pathsync aio_readahead 178 aio_fdatasync aio_sync_file_range aio_pathsync aio_readahead
204 aio_rename aio_link aio_move aio_copy aio_group 179 aio_rename aio_link aio_move aio_copy aio_group
205 aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown 180 aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown
206 aio_chmod aio_utime aio_truncate); 181 aio_chmod aio_utime aio_truncate
182 aio_msync aio_mtouch aio_mlock aio_mlockall
183 aio_statvfs);
207 184
208 our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice)); 185 our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
209 our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush 186 our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
210 min_parallel max_parallel max_idle 187 min_parallel max_parallel max_idle idle_timeout
211 nreqs nready npending nthreads 188 nreqs nready npending nthreads
212 max_poll_time max_poll_reqs); 189 max_poll_time max_poll_reqs
190 sendfile fadvise madvise
191 mmap munmap munlock munlockall);
213 192
214 push @AIO_REQ, qw(aio_busy); # not exported 193 push @AIO_REQ, qw(aio_busy); # not exported
215 194
216 @IO::AIO::GRP::ISA = 'IO::AIO::REQ'; 195 @IO::AIO::GRP::ISA = 'IO::AIO::REQ';
217 196
218 require XSLoader; 197 require XSLoader;
219 XSLoader::load ("IO::AIO", $VERSION); 198 XSLoader::load ("IO::AIO", $VERSION);
220} 199}
221 200
222=head1 FUNCTIONS 201=head1 FUNCTIONS
202
203=head2 QUICK OVERVIEW
204
205This section simply lists the prototypes of the most important functions
206for quick reference. See the following sections for function-by-function
207documentation.
208
209 aio_open $pathname, $flags, $mode, $callback->($fh)
210 aio_close $fh, $callback->($status)
211 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
212 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
213 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
214 aio_readahead $fh,$offset,$length, $callback->($retval)
215 aio_stat $fh_or_path, $callback->($status)
216 aio_lstat $fh, $callback->($status)
217 aio_statvfs $fh_or_path, $callback->($statvfs)
218 aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
219 aio_chown $fh_or_path, $uid, $gid, $callback->($status)
220 aio_truncate $fh_or_path, $offset, $callback->($status)
221 aio_chmod $fh_or_path, $mode, $callback->($status)
222 aio_unlink $pathname, $callback->($status)
223 aio_mknod $path, $mode, $dev, $callback->($status)
224 aio_link $srcpath, $dstpath, $callback->($status)
225 aio_symlink $srcpath, $dstpath, $callback->($status)
226 aio_readlink $path, $callback->($link)
227 aio_rename $srcpath, $dstpath, $callback->($status)
228 aio_mkdir $pathname, $mode, $callback->($status)
229 aio_rmdir $pathname, $callback->($status)
230 aio_readdir $pathname, $callback->($entries)
231 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
232 IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
233 IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
234 aio_load $path, $data, $callback->($status)
235 aio_copy $srcpath, $dstpath, $callback->($status)
236 aio_move $srcpath, $dstpath, $callback->($status)
237 aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
238 aio_rmtree $path, $callback->($status)
239 aio_sync $callback->($status)
240 aio_fsync $fh, $callback->($status)
241 aio_fdatasync $fh, $callback->($status)
242 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
243 aio_pathsync $path, $callback->($status)
244 aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
245 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
246 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
247 aio_mlockall $flags, $callback->($status)
248 aio_group $callback->(...)
249 aio_nop $callback->()
250
251 $prev_pri = aioreq_pri [$pri]
252 aioreq_nice $pri_adjust
253
254 IO::AIO::poll_wait
255 IO::AIO::poll_cb
256 IO::AIO::poll
257 IO::AIO::flush
258 IO::AIO::max_poll_reqs $nreqs
259 IO::AIO::max_poll_time $seconds
260 IO::AIO::min_parallel $nthreads
261 IO::AIO::max_parallel $nthreads
262 IO::AIO::max_idle $nthreads
263 IO::AIO::idle_timeout $seconds
264 IO::AIO::max_outstanding $maxreqs
265 IO::AIO::nreqs
266 IO::AIO::nready
267 IO::AIO::npending
268
269 IO::AIO::sendfile $ofh, $ifh, $offset, $count
270 IO::AIO::fadvise $fh, $offset, $len, $advice
271 IO::AIO::madvise $scalar, $offset, $length, $advice
272 IO::AIO::mprotect $scalar, $offset, $length, $protect
273 IO::AIO::munlock $scalar, $offset = 0, $length = undef
274 IO::AIO::munlockall
223 275
224=head2 AIO REQUEST FUNCTIONS 276=head2 AIO REQUEST FUNCTIONS
225 277
226All the C<aio_*> calls are more or less thin wrappers around the syscall 278All the C<aio_*> calls are more or less thin wrappers around the syscall
227with the same name (sans C<aio_>). The arguments are similar or identical, 279with the same name (sans C<aio_>). The arguments are similar or identical,
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307by the umask in effect then the request is being executed, so better never 359by the umask in effect then the request is being executed, so better never
308change the umask. 360change the umask.
309 361
310Example: 362Example:
311 363
312 aio_open "/etc/passwd", O_RDONLY, 0, sub { 364 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
313 if ($_[0]) { 365 if ($_[0]) {
314 print "open successful, fh is $_[0]\n"; 366 print "open successful, fh is $_[0]\n";
315 ... 367 ...
316 } else { 368 } else {
317 die "open failed: $!\n"; 369 die "open failed: $!\n";
318 } 370 }
319 }; 371 };
320 372
373In addition to all the common open modes/flags (C<O_RDONLY>, C<O_WRONLY>,
374C<O_RDWR>, C<O_CREAT>, C<O_TRUNC>, C<O_EXCL> and C<O_APPEND>), the
375following POSIX and non-POSIX constants are available (missing ones on
376your system are, as usual, C<0>):
377
378C<O_ASYNC>, C<O_DIRECT>, C<O_NOATIME>, C<O_CLOEXEC>, C<O_NOCTTY>, C<O_NOFOLLOW>,
379C<O_NONBLOCK>, C<O_EXEC>, C<O_SEARCH>, C<O_DIRECTORY>, C<O_DSYNC>,
380C<O_RSYNC>, C<O_SYNC> and C<O_TTY_INIT>.
381
321 382
322=item aio_close $fh, $callback->($status) 383=item aio_close $fh, $callback->($status)
323 384
324Asynchronously close a file and call the callback with the result 385Asynchronously close a file and call the callback with the result
325code. 386code.
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375 436
376Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts 437Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
377reading at byte offset C<$in_offset>, and starts writing at the current 438reading at byte offset C<$in_offset>, and starts writing at the current
378file offset of C<$out_fh>. Because of that, it is not safe to issue more 439file offset of C<$out_fh>. Because of that, it is not safe to issue more
379than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each 440than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
380other. 441other. The same C<$in_fh> works fine though, as this function does not
442move or use the file offset of C<$in_fh>.
381 443
444Please note that C<aio_sendfile> can read more bytes from C<$in_fh> than
445are written, and there is no way to find out how many more bytes have been
446read from C<aio_sendfile> alone, as C<aio_sendfile> only provides the
447number of bytes written to C<$out_fh>. Only if the result value equals
448C<$length> one can assume that C<$length> bytes have been read.
449
450Unlike with other C<aio_> functions, it makes a lot of sense to use
451C<aio_sendfile> on non-blocking sockets, as long as one end (typically
452the C<$in_fh>) is a file - the file I/O will then be asynchronous, while
453the socket I/O will be non-blocking. Note, however, that you can run
454into a trap where C<aio_sendfile> reads some data with readahead, then
455fails to write all data, and when the socket is ready the next time, the
456data in the cache is already lost, forcing C<aio_sendfile> to again hit
457the disk. Explicit C<aio_read> + C<aio_write> let's you better control
458resource usage.
459
382This call tries to make use of a native C<sendfile> syscall to provide 460This call tries to make use of a native C<sendfile>-like syscall to
383zero-copy operation. For this to work, C<$out_fh> should refer to a 461provide zero-copy operation. For this to work, C<$out_fh> should refer to
384socket, and C<$in_fh> should refer to mmap'able file. 462a socket, and C<$in_fh> should refer to an mmap'able file.
385 463
386If the native sendfile call fails or is not implemented, it will be 464If a native sendfile cannot be found or it fails with C<ENOSYS>,
387emulated, so you can call C<aio_sendfile> on any type of filehandle 465C<EINVAL>, C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or
466C<ENOTSOCK>, it will be emulated, so you can call C<aio_sendfile> on any
388regardless of the limitations of the operating system. 467type of filehandle regardless of the limitations of the operating system.
389 468
390Please note, however, that C<aio_sendfile> can read more bytes from 469As native sendfile syscalls (as practically any non-POSIX interface hacked
391C<$in_fh> than are written, and there is no way to find out how many 470together in a hurry to improve benchmark numbers) tend to be rather buggy
392bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only 471on many systems, this implementation tries to work around some known bugs
393provides the number of bytes written to C<$out_fh>. Only if the result 472in Linux and FreeBSD kernels (probably others, too), but that might fail,
394value equals C<$length> one can assume that C<$length> bytes have been 473so you really really should check the return value of C<aio_sendfile> -
395read. 474fewre bytes than expected might have been transferred.
396 475
397 476
398=item aio_readahead $fh,$offset,$length, $callback->($retval) 477=item aio_readahead $fh,$offset,$length, $callback->($retval)
399 478
400C<aio_readahead> populates the page cache with data from a file so that 479C<aio_readahead> populates the page cache with data from a file so that
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423 502
424Currently, the stats are always 64-bit-stats, i.e. instead of returning an 503Currently, the stats are always 64-bit-stats, i.e. instead of returning an
425error when stat'ing a large file, the results will be silently truncated 504error when stat'ing a large file, the results will be silently truncated
426unless perl itself is compiled with large file support. 505unless perl itself is compiled with large file support.
427 506
507To help interpret the mode and dev/rdev stat values, IO::AIO offers the
508following constants and functions (if not implemented, the constants will
509be C<0> and the functions will either C<croak> or fall back on traditional
510behaviour).
511
512C<S_IFMT>, C<S_IFIFO>, C<S_IFCHR>, C<S_IFBLK>, C<S_IFLNK>, C<S_IFREG>,
513C<S_IFDIR>, C<S_IFWHT>, C<S_IFSOCK>, C<IO::AIO::major $dev_t>,
514C<IO::AIO::minor $dev_t>, C<IO::AIO::makedev $major, $minor>.
515
428Example: Print the length of F</etc/passwd>: 516Example: Print the length of F</etc/passwd>:
429 517
430 aio_stat "/etc/passwd", sub { 518 aio_stat "/etc/passwd", sub {
431 $_[0] and die "stat failed: $!"; 519 $_[0] and die "stat failed: $!";
432 print "size is ", -s _, "\n"; 520 print "size is ", -s _, "\n";
433 }; 521 };
434 522
435 523
524=item aio_statvfs $fh_or_path, $callback->($statvfs)
525
526Works like the POSIX C<statvfs> or C<fstatvfs> syscalls, depending on
527whether a file handle or path was passed.
528
529On success, the callback is passed a hash reference with the following
530members: C<bsize>, C<frsize>, C<blocks>, C<bfree>, C<bavail>, C<files>,
531C<ffree>, C<favail>, C<fsid>, C<flag> and C<namemax>. On failure, C<undef>
532is passed.
533
534The following POSIX IO::AIO::ST_* constants are defined: C<ST_RDONLY> and
535C<ST_NOSUID>.
536
537The following non-POSIX IO::AIO::ST_* flag masks are defined to
538their correct value when available, or to C<0> on systems that do
539not support them: C<ST_NODEV>, C<ST_NOEXEC>, C<ST_SYNCHRONOUS>,
540C<ST_MANDLOCK>, C<ST_WRITE>, C<ST_APPEND>, C<ST_IMMUTABLE>, C<ST_NOATIME>,
541C<ST_NODIRATIME> and C<ST_RELATIME>.
542
543Example: stat C</wd> and dump out the data if successful.
544
545 aio_statvfs "/wd", sub {
546 my $f = $_[0]
547 or die "statvfs: $!";
548
549 use Data::Dumper;
550 say Dumper $f;
551 };
552
553 # result:
554 {
555 bsize => 1024,
556 bfree => 4333064312,
557 blocks => 10253828096,
558 files => 2050765568,
559 flag => 4096,
560 favail => 2042092649,
561 bavail => 4333064312,
562 ffree => 2042092649,
563 namemax => 255,
564 frsize => 1024,
565 fsid => 1810
566 }
567
568
436=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status) 569=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
437 570
438Works like perl's C<utime> function (including the special case of $atime 571Works like perl's C<utime> function (including the special case of $atime
439and $mtime being undef). Fractional times are supported if the underlying 572and $mtime being undef). Fractional times are supported if the underlying
440syscalls support them. 573syscalls support them.
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488 621
489The only (POSIX-) portable way of calling this function is: 622The only (POSIX-) portable way of calling this function is:
490 623
491 aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ... 624 aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...
492 625
626See C<aio_stat> for info about some potentially helpful extra constants
627and functions.
493 628
494=item aio_link $srcpath, $dstpath, $callback->($status) 629=item aio_link $srcpath, $dstpath, $callback->($status)
495 630
496Asynchronously create a new link to the existing object at C<$srcpath> at 631Asynchronously create a new link to the existing object at C<$srcpath> at
497the path C<$dstpath> and call the callback with the result code. 632the path C<$dstpath> and call the callback with the result code.
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550 685
551=over 4 686=over 4
552 687
553=item IO::AIO::READDIR_DENTS 688=item IO::AIO::READDIR_DENTS
554 689
555When this flag is off, then the callback gets an arrayref with of names 690When this flag is off, then the callback gets an arrayref consisting of
556only (as with C<aio_readdir>), otherwise it gets an arrayref with 691names only (as with C<aio_readdir>), otherwise it gets an arrayref with
557C<[$name, $type, $inode]> arrayrefs, each describing a single directory 692C<[$name, $type, $inode]> arrayrefs, each describing a single directory
558entry in more detail. 693entry in more detail.
559 694
560C<$name> is the name of the entry. 695C<$name> is the name of the entry.
561 696
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568C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need to 703C<IO::AIO::DT_UNKNOWN> means just that: readdir does not know. If you need to
569know, you have to run stat yourself. Also, for speed reasons, the C<$type> 704know, you have to run stat yourself. Also, for speed reasons, the C<$type>
570scalars are read-only: you can not modify them. 705scalars are read-only: you can not modify them.
571 706
572C<$inode> is the inode number (which might not be exact on systems with 64 707C<$inode> is the inode number (which might not be exact on systems with 64
573bit inode numbers and 32 bit perls). On systems that do not deliver the 708bit inode numbers and 32 bit perls). This field has unspecified content on
574inode information, this will always be zero. 709systems that do not deliver the inode information.
575 710
576=item IO::AIO::READDIR_DIRS_FIRST 711=item IO::AIO::READDIR_DIRS_FIRST
577 712
578When this flag is set, then the names will be returned in an order where 713When this flag is set, then the names will be returned in an order where
579likely directories come first. This is useful when you need to quickly 714likely directories come first, in optimal stat order. This is useful when
580find directories, or you want to find all directories while avoiding to 715you need to quickly find directories, or you want to find all directories
581stat() each entry. 716while avoiding to stat() each entry.
582 717
583If the system returns type information in readdir, then this is used 718If the system returns type information in readdir, then this is used
584to find directories directly. Otherwise, likely directories are files 719to find directories directly. Otherwise, likely directories are names
585beginning with ".", or otherwise files with no dots, of which files with 720beginning with ".", or otherwise names with no dots, of which names with
586short names are tried first. 721short names are tried first.
587 722
588=item IO::AIO::READDIR_STAT_ORDER 723=item IO::AIO::READDIR_STAT_ORDER
589 724
590When this flag is set, then the names will be returned in an order 725When this flag is set, then the names will be returned in an order
… …
635 770
636=item aio_copy $srcpath, $dstpath, $callback->($status) 771=item aio_copy $srcpath, $dstpath, $callback->($status)
637 772
638Try to copy the I<file> (directories not supported as either source or 773Try to copy the I<file> (directories not supported as either source or
639destination) from C<$srcpath> to C<$dstpath> and call the callback with 774destination) from C<$srcpath> to C<$dstpath> and call the callback with
640the C<0> (error) or C<-1> ok. 775a status of C<0> (ok) or C<-1> (error, see C<$!>).
641 776
642This is a composite request that creates the destination file with 777This is a composite request that creates the destination file with
643mode 0200 and copies the contents of the source file into it using 778mode 0200 and copies the contents of the source file into it using
644C<aio_sendfile>, followed by restoring atime, mtime, access mode and 779C<aio_sendfile>, followed by restoring atime, mtime, access mode and
645uid/gid, in that order. 780uid/gid, in that order.
… …
657 my $grp = aio_group $cb; 792 my $grp = aio_group $cb;
658 793
659 aioreq_pri $pri; 794 aioreq_pri $pri;
660 add $grp aio_open $src, O_RDONLY, 0, sub { 795 add $grp aio_open $src, O_RDONLY, 0, sub {
661 if (my $src_fh = $_[0]) { 796 if (my $src_fh = $_[0]) {
662 my @stat = stat $src_fh; # hmm, might bock over nfs? 797 my @stat = stat $src_fh; # hmm, might block over nfs?
663 798
664 aioreq_pri $pri; 799 aioreq_pri $pri;
665 add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub { 800 add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
666 if (my $dst_fh = $_[0]) { 801 if (my $dst_fh = $_[0]) {
667 aioreq_pri $pri; 802 aioreq_pri $pri;
… …
714 849
715=item aio_move $srcpath, $dstpath, $callback->($status) 850=item aio_move $srcpath, $dstpath, $callback->($status)
716 851
717Try to move the I<file> (directories not supported as either source or 852Try to move the I<file> (directories not supported as either source or
718destination) from C<$srcpath> to C<$dstpath> and call the callback with 853destination) from C<$srcpath> to C<$dstpath> and call the callback with
719the C<0> (error) or C<-1> ok. 854a status of C<0> (ok) or C<-1> (error, see C<$!>).
720 855
721This is a composite request that tries to rename(2) the file first; if 856This is a composite request that tries to rename(2) the file first; if
722rename fails with C<EXDEV>, it copies the file with C<aio_copy> and, if 857rename fails with C<EXDEV>, it copies the file with C<aio_copy> and, if
723that is successful, unlinks the C<$srcpath>. 858that is successful, unlinks the C<$srcpath>.
724 859
… …
735 if ($_[0] && $! == EXDEV) { 870 if ($_[0] && $! == EXDEV) {
736 aioreq_pri $pri; 871 aioreq_pri $pri;
737 add $grp aio_copy $src, $dst, sub { 872 add $grp aio_copy $src, $dst, sub {
738 $grp->result ($_[0]); 873 $grp->result ($_[0]);
739 874
740 if (!$_[0]) { 875 unless ($_[0]) {
741 aioreq_pri $pri; 876 aioreq_pri $pri;
742 add $grp aio_unlink $src; 877 add $grp aio_unlink $src;
743 } 878 }
744 }; 879 };
745 } else { 880 } else {
… …
958(E.g. rename). This might not work on all operating systems or have any 1093(E.g. rename). This might not work on all operating systems or have any
959specific effect, but usually it makes sure that directory changes get 1094specific effect, but usually it makes sure that directory changes get
960written to disc. It works for anything that can be opened for read-only, 1095written to disc. It works for anything that can be opened for read-only,
961not just directories. 1096not just directories.
962 1097
1098Future versions of this function might fall back to other methods when
1099C<fsync> on the directory fails (such as calling C<sync>).
1100
963Passes C<0> when everything went ok, and C<-1> on error. 1101Passes C<0> when everything went ok, and C<-1> on error.
964 1102
965=cut 1103=cut
966 1104
967sub aio_pathsync($;$) { 1105sub aio_pathsync($;$) {
… …
987 }; 1125 };
988 1126
989 $grp 1127 $grp
990} 1128}
991 1129
1130=item aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
1131
1132This is a rather advanced IO::AIO call, which only works on mmap(2)ed
1133scalars (see the C<IO::AIO::mmap> function, although it also works on data
1134scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the
1135scalar must only be modified in-place while an aio operation is pending on
1136it).
1137
1138It calls the C<msync> function of your OS, if available, with the memory
1139area starting at C<$offset> in the string and ending C<$length> bytes
1140later. If C<$length> is negative, counts from the end, and if C<$length>
1141is C<undef>, then it goes till the end of the string. The flags can be
1142a combination of C<IO::AIO::MS_ASYNC>, C<IO::AIO::MS_INVALIDATE> and
1143C<IO::AIO::MS_SYNC>.
1144
1145=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
1146
1147This is a rather advanced IO::AIO call, which works best on mmap(2)ed
1148scalars.
1149
1150It touches (reads or writes) all memory pages in the specified
1151range inside the scalar. All caveats and parameters are the same
1152as for C<aio_msync>, above, except for flags, which must be either
1153C<0> (which reads all pages and ensures they are instantiated) or
1154C<IO::AIO::MT_MODIFY>, which modifies the memory page s(by reading and
1155writing an octet from it, which dirties the page).
1156
1157=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
1158
1159This is a rather advanced IO::AIO call, which works best on mmap(2)ed
1160scalars.
1161
1162It reads in all the pages of the underlying storage into memory (if any)
1163and locks them, so they are not getting swapped/paged out or removed.
1164
1165If C<$length> is undefined, then the scalar will be locked till the end.
1166
1167On systems that do not implement C<mlock>, this function returns C<-1>
1168and sets errno to C<ENOSYS>.
1169
1170Note that the corresponding C<munlock> is synchronous and is
1171documented under L<MISCELLANEOUS FUNCTIONS>.
1172
1173Example: open a file, mmap and mlock it - both will be undone when
1174C<$data> gets destroyed.
1175
1176 open my $fh, "<", $path or die "$path: $!";
1177 my $data;
1178 IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
1179 aio_mlock $data; # mlock in background
1180
1181=item aio_mlockall $flags, $callback->($status)
1182
1183Calls the C<mlockall> function with the given C<$flags> (a combination of
1184C<IO::AIO::MCL_CURRENT> and C<IO::AIO::MCL_FUTURE>).
1185
1186On systems that do not implement C<mlockall>, this function returns C<-1>
1187and sets errno to C<ENOSYS>.
1188
1189Note that the corresponding C<munlockall> is synchronous and is
1190documented under L<MISCELLANEOUS FUNCTIONS>.
1191
1192Example: asynchronously lock all current and future pages into memory.
1193
1194 aio_mlockall IO::AIO::MCL_FUTURE;
1195
992=item aio_group $callback->(...) 1196=item aio_group $callback->(...)
993 1197
994This is a very special aio request: Instead of doing something, it is a 1198This is a very special aio request: Instead of doing something, it is a
995container for other aio requests, which is useful if you want to bundle 1199container for other aio requests, which is useful if you want to bundle
996many requests into a single, composite, request with a definite callback 1200many requests into a single, composite, request with a definite callback
… …
1131=item $grp->cancel_subs 1335=item $grp->cancel_subs
1132 1336
1133Cancel all subrequests and clears any feeder, but not the group request 1337Cancel all subrequests and clears any feeder, but not the group request
1134itself. Useful when you queued a lot of events but got a result early. 1338itself. Useful when you queued a lot of events but got a result early.
1135 1339
1340The group request will finish normally (you cannot add requests to the
1341group).
1342
1136=item $grp->result (...) 1343=item $grp->result (...)
1137 1344
1138Set the result value(s) that will be passed to the group callback when all 1345Set the result value(s) that will be passed to the group callback when all
1139subrequests have finished and set the groups errno to the current value 1346subrequests have finished and set the groups errno to the current value
1140of errno (just like calling C<errno> without an error number). By default, 1347of errno (just like calling C<errno> without an error number). By default,
… …
1208=over 4 1415=over 4
1209 1416
1210=item $fileno = IO::AIO::poll_fileno 1417=item $fileno = IO::AIO::poll_fileno
1211 1418
1212Return the I<request result pipe file descriptor>. This filehandle must be 1419Return the I<request result pipe file descriptor>. This filehandle must be
1213polled for reading by some mechanism outside this module (e.g. Event or 1420polled for reading by some mechanism outside this module (e.g. EV, Glib,
1214select, see below or the SYNOPSIS). If the pipe becomes readable you have 1421select and so on, see below or the SYNOPSIS). If the pipe becomes readable
1215to call C<poll_cb> to check the results. 1422you have to call C<poll_cb> to check the results.
1216 1423
1217See C<poll_cb> for an example. 1424See C<poll_cb> for an example.
1218 1425
1219=item IO::AIO::poll_cb 1426=item IO::AIO::poll_cb
1220 1427
1221Process some outstanding events on the result pipe. You have to call this 1428Process some outstanding events on the result pipe. You have to call
1222regularly. Returns C<0> if all events could be processed, or C<-1> if it 1429this regularly. Returns C<0> if all events could be processed (or there
1223returned earlier for whatever reason. Returns immediately when no events 1430were no events to process), or C<-1> if it returned earlier for whatever
1224are outstanding. The amount of events processed depends on the settings of 1431reason. Returns immediately when no events are outstanding. The amount of
1225C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>. 1432events processed depends on the settings of C<IO::AIO::max_poll_req> and
1433C<IO::AIO::max_poll_time>.
1226 1434
1227If not all requests were processed for whatever reason, the filehandle 1435If not all requests were processed for whatever reason, the filehandle
1228will still be ready when C<poll_cb> returns, so normally you don't have to 1436will still be ready when C<poll_cb> returns, so normally you don't have to
1229do anything special to have it called later. 1437do anything special to have it called later.
1230 1438
1439Apart from calling C<IO::AIO::poll_cb> when the event filehandle becomes
1440ready, it can be beneficial to call this function from loops which submit
1441a lot of requests, to make sure the results get processed when they become
1442available and not just when the loop is finished and the event loop takes
1443over again. This function returns very fast when there are no outstanding
1444requests.
1445
1231Example: Install an Event watcher that automatically calls 1446Example: Install an Event watcher that automatically calls
1232IO::AIO::poll_cb with high priority: 1447IO::AIO::poll_cb with high priority (more examples can be found in the
1448SYNOPSIS section, at the top of this document):
1233 1449
1234 Event->io (fd => IO::AIO::poll_fileno, 1450 Event->io (fd => IO::AIO::poll_fileno,
1235 poll => 'r', async => 1, 1451 poll => 'r', async => 1,
1236 cb => \&IO::AIO::poll_cb); 1452 cb => \&IO::AIO::poll_cb);
1453
1454=item IO::AIO::poll_wait
1455
1456If there are any outstanding requests and none of them in the result
1457phase, wait till the result filehandle becomes ready for reading (simply
1458does a C<select> on the filehandle. This is useful if you want to
1459synchronously wait for some requests to finish).
1460
1461See C<nreqs> for an example.
1462
1463=item IO::AIO::poll
1464
1465Waits until some requests have been handled.
1466
1467Returns the number of requests processed, but is otherwise strictly
1468equivalent to:
1469
1470 IO::AIO::poll_wait, IO::AIO::poll_cb
1471
1472=item IO::AIO::flush
1473
1474Wait till all outstanding AIO requests have been handled.
1475
1476Strictly equivalent to:
1477
1478 IO::AIO::poll_wait, IO::AIO::poll_cb
1479 while IO::AIO::nreqs;
1237 1480
1238=item IO::AIO::max_poll_reqs $nreqs 1481=item IO::AIO::max_poll_reqs $nreqs
1239 1482
1240=item IO::AIO::max_poll_time $seconds 1483=item IO::AIO::max_poll_time $seconds
1241 1484
… …
1266 # use a low priority so other tasks have priority 1509 # use a low priority so other tasks have priority
1267 Event->io (fd => IO::AIO::poll_fileno, 1510 Event->io (fd => IO::AIO::poll_fileno,
1268 poll => 'r', nice => 1, 1511 poll => 'r', nice => 1,
1269 cb => &IO::AIO::poll_cb); 1512 cb => &IO::AIO::poll_cb);
1270 1513
1271=item IO::AIO::poll_wait
1272
1273If there are any outstanding requests and none of them in the result
1274phase, wait till the result filehandle becomes ready for reading (simply
1275does a C<select> on the filehandle. This is useful if you want to
1276synchronously wait for some requests to finish).
1277
1278See C<nreqs> for an example.
1279
1280=item IO::AIO::poll
1281
1282Waits until some requests have been handled.
1283
1284Returns the number of requests processed, but is otherwise strictly
1285equivalent to:
1286
1287 IO::AIO::poll_wait, IO::AIO::poll_cb
1288
1289=item IO::AIO::flush
1290
1291Wait till all outstanding AIO requests have been handled.
1292
1293Strictly equivalent to:
1294
1295 IO::AIO::poll_wait, IO::AIO::poll_cb
1296 while IO::AIO::nreqs;
1297
1298=back 1514=back
1299 1515
1300=head3 CONTROLLING THE NUMBER OF THREADS 1516=head3 CONTROLLING THE NUMBER OF THREADS
1301 1517
1302=over 1518=over
… …
1335 1551
1336Under normal circumstances you don't need to call this function. 1552Under normal circumstances you don't need to call this function.
1337 1553
1338=item IO::AIO::max_idle $nthreads 1554=item IO::AIO::max_idle $nthreads
1339 1555
1340Limit the number of threads (default: 4) that are allowed to idle (i.e., 1556Limit the number of threads (default: 4) that are allowed to idle
1341threads that did not get a request to process within 10 seconds). That 1557(i.e., threads that did not get a request to process within the idle
1342means if a thread becomes idle while C<$nthreads> other threads are also 1558timeout (default: 10 seconds). That means if a thread becomes idle while
1343idle, it will free its resources and exit. 1559C<$nthreads> other threads are also idle, it will free its resources and
1560exit.
1344 1561
1345This is useful when you allow a large number of threads (e.g. 100 or 1000) 1562This is useful when you allow a large number of threads (e.g. 100 or 1000)
1346to allow for extremely high load situations, but want to free resources 1563to allow for extremely high load situations, but want to free resources
1347under normal circumstances (1000 threads can easily consume 30MB of RAM). 1564under normal circumstances (1000 threads can easily consume 30MB of RAM).
1348 1565
1349The default is probably ok in most situations, especially if thread 1566The default is probably ok in most situations, especially if thread
1350creation is fast. If thread creation is very slow on your system you might 1567creation is fast. If thread creation is very slow on your system you might
1351want to use larger values. 1568want to use larger values.
1352 1569
1570=item IO::AIO::idle_timeout $seconds
1571
1572Sets the minimum idle timeout (default 10) after which worker threads are
1573allowed to exit. SEe C<IO::AIO::max_idle>.
1574
1353=item IO::AIO::max_outstanding $maxreqs 1575=item IO::AIO::max_outstanding $maxreqs
1576
1577Sets the maximum number of outstanding requests to C<$nreqs>. If
1578you do queue up more than this number of requests, the next call to
1579C<IO::AIO::poll_cb> (and other functions calling C<poll_cb>, such as
1580C<IO::AIO::flush> or C<IO::AIO::poll>) will block until the limit is no
1581longer exceeded.
1582
1583In other words, this setting does not enforce a queue limit, but can be
1584used to make poll functions block if the limit is exceeded.
1354 1585
1355This is a very bad function to use in interactive programs because it 1586This is a very bad function to use in interactive programs because it
1356blocks, and a bad way to reduce concurrency because it is inexact: Better 1587blocks, and a bad way to reduce concurrency because it is inexact: Better
1357use an C<aio_group> together with a feed callback. 1588use an C<aio_group> together with a feed callback.
1358 1589
1359Sets the maximum number of outstanding requests to C<$nreqs>. If you 1590It's main use is in scripts without an event loop - when you want to stat
1360do queue up more than this number of requests, the next call to the 1591a lot of files, you can write somehting like this:
1361C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
1362function will block until the limit is no longer exceeded.
1363 1592
1364The default value is very large, so there is no practical limit on the 1593 IO::AIO::max_outstanding 32;
1365number of outstanding requests.
1366 1594
1367You can still queue as many requests as you want. Therefore, 1595 for my $path (...) {
1368C<max_outstanding> is mainly useful in simple scripts (with low values) or 1596 aio_stat $path , ...;
1369as a stop gap to shield against fatal memory overflow (with large values). 1597 IO::AIO::poll_cb;
1598 }
1599
1600 IO::AIO::flush;
1601
1602The call to C<poll_cb> inside the loop will normally return instantly, but
1603as soon as more thna C<32> reqeusts are in-flight, it will block until
1604some requests have been handled. This keeps the loop from pushing a large
1605number of C<aio_stat> requests onto the queue.
1606
1607The default value for C<max_outstanding> is very large, so there is no
1608practical limit on the number of outstanding requests.
1370 1609
1371=back 1610=back
1372 1611
1373=head3 STATISTICAL INFORMATION 1612=head3 STATISTICAL INFORMATION
1374 1613
… …
1394Returns the number of requests currently in the pending state (executed, 1633Returns the number of requests currently in the pending state (executed,
1395but not yet processed by poll_cb). 1634but not yet processed by poll_cb).
1396 1635
1397=back 1636=back
1398 1637
1638=head3 MISCELLANEOUS FUNCTIONS
1639
1640IO::AIO implements some functions that might be useful, but are not
1641asynchronous.
1642
1643=over 4
1644
1645=item IO::AIO::sendfile $ofh, $ifh, $offset, $count
1646
1647Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,
1648but is blocking (this makes most sense if you know the input data is
1649likely cached already and the output filehandle is set to non-blocking
1650operations).
1651
1652Returns the number of bytes copied, or C<-1> on error.
1653
1654=item IO::AIO::fadvise $fh, $offset, $len, $advice
1655
1656Simply calls the C<posix_fadvise> function (see its
1657manpage for details). The following advice constants are
1658avaiable: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,
1659C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,
1660C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.
1661
1662On systems that do not implement C<posix_fadvise>, this function returns
1663ENOSYS, otherwise the return value of C<posix_fadvise>.
1664
1665=item IO::AIO::madvise $scalar, $offset, $len, $advice
1666
1667Simply calls the C<posix_madvise> function (see its
1668manpage for details). The following advice constants are
1669avaiable: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,
1670C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>, C<IO::AIO::MADV_DONTNEED>.
1671
1672On systems that do not implement C<posix_madvise>, this function returns
1673ENOSYS, otherwise the return value of C<posix_madvise>.
1674
1675=item IO::AIO::mprotect $scalar, $offset, $len, $protect
1676
1677Simply calls the C<mprotect> function on the preferably AIO::mmap'ed
1678$scalar (see its manpage for details). The following protect
1679constants are avaiable: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,
1680C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.
1681
1682On systems that do not implement C<mprotect>, this function returns
1683ENOSYS, otherwise the return value of C<mprotect>.
1684
1685=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
1686
1687Memory-maps a file (or anonymous memory range) and attaches it to the
1688given C<$scalar>, which will act like a string scalar.
1689
1690The only operations allowed on the scalar are C<substr>/C<vec> that don't
1691change the string length, and most read-only operations such as copying it
1692or searching it with regexes and so on.
1693
1694Anything else is unsafe and will, at best, result in memory leaks.
1695
1696The memory map associated with the C<$scalar> is automatically removed
1697when the C<$scalar> is destroyed, or when the C<IO::AIO::mmap> or
1698C<IO::AIO::munmap> functions are called.
1699
1700This calls the C<mmap>(2) function internally. See your system's manual
1701page for details on the C<$length>, C<$prot> and C<$flags> parameters.
1702
1703The C<$length> must be larger than zero and smaller than the actual
1704filesize.
1705
1706C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,
1707C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,
1708
1709C<$flags> can be a combination of C<IO::AIO::MAP_SHARED> or
1710C<IO::AIO::MAP_PRIVATE>, or a number of system-specific flags (when
1711not available, the are defined as 0): C<IO::AIO::MAP_ANONYMOUS>
1712(which is set to C<MAP_ANON> if your system only provides this
1713constant), C<IO::AIO::MAP_HUGETLB>, C<IO::AIO::MAP_LOCKED>,
1714C<IO::AIO::MAP_NORESERVE>, C<IO::AIO::MAP_POPULATE> or
1715C<IO::AIO::MAP_NONBLOCK>
1716
1717If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.
1718
1719C<$offset> is the offset from the start of the file - it generally must be
1720a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.
1721
1722Example:
1723
1724 use Digest::MD5;
1725 use IO::AIO;
1726
1727 open my $fh, "<verybigfile"
1728 or die "$!";
1729
1730 IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
1731 or die "verybigfile: $!";
1732
1733 my $fast_md5 = md5 $data;
1734
1735=item IO::AIO::munmap $scalar
1736
1737Removes a previous mmap and undefines the C<$scalar>.
1738
1739=item IO::AIO::munlock $scalar, $offset = 0, $length = undef
1740
1741Calls the C<munlock> function, undoing the effects of a previous
1742C<aio_mlock> call (see its description for details).
1743
1744=item IO::AIO::munlockall
1745
1746Calls the C<munlockall> function.
1747
1748On systems that do not implement C<munlockall>, this function returns
1749ENOSYS, otherwise the return value of C<munlockall>.
1750
1751=back
1752
1399=cut 1753=cut
1400 1754
1401min_parallel 8; 1755min_parallel 8;
1402 1756
1403END { flush } 1757END { flush }
1404 1758
14051; 17591;
1406 1760
1761=head1 EVENT LOOP INTEGRATION
1762
1763It is recommended to use L<AnyEvent::AIO> to integrate IO::AIO
1764automatically into many event loops:
1765
1766 # AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
1767 use AnyEvent::AIO;
1768
1769You can also integrate IO::AIO manually into many event loops, here are
1770some examples of how to do this:
1771
1772 # EV integration
1773 my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
1774
1775 # Event integration
1776 Event->io (fd => IO::AIO::poll_fileno,
1777 poll => 'r',
1778 cb => \&IO::AIO::poll_cb);
1779
1780 # Glib/Gtk2 integration
1781 add_watch Glib::IO IO::AIO::poll_fileno,
1782 in => sub { IO::AIO::poll_cb; 1 };
1783
1784 # Tk integration
1785 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
1786 readable => \&IO::AIO::poll_cb);
1787
1788 # Danga::Socket integration
1789 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
1790 \&IO::AIO::poll_cb);
1791
1407=head2 FORK BEHAVIOUR 1792=head2 FORK BEHAVIOUR
1408 1793
1409This module should do "the right thing" when the process using it forks: 1794Usage of pthreads in a program changes the semantics of fork
1795considerably. Specifically, only async-safe functions can be called after
1796fork. Perl doesn't know about this, so in general, you cannot call fork
1797with defined behaviour in perl. IO::AIO uses pthreads, so this applies,
1798but many other extensions and (for inexplicable reasons) perl itself often
1799is linked against pthreads, so this limitation applies.
1410 1800
1411Before the fork, IO::AIO enters a quiescent state where no requests 1801Some operating systems have extensions that allow safe use of fork, and
1412can be added in other threads and no results will be processed. After 1802this module should do "the right thing" on those, and tries on others. At
1413the fork the parent simply leaves the quiescent state and continues 1803the time of this writing (2011) only GNU/Linux supports these extensions
1414request/result processing, while the child frees the request/result queue 1804to POSIX.
1415(so that the requests started before the fork will only be handled in the
1416parent). Threads will be started on demand until the limit set in the
1417parent process has been reached again.
1418
1419In short: the parent will, after a short pause, continue as if fork had
1420not been called, while the child will act as if IO::AIO has not been used
1421yet.
1422 1805
1423=head2 MEMORY USAGE 1806=head2 MEMORY USAGE
1424 1807
1425Per-request usage: 1808Per-request usage:
1426 1809

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