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Revision 1.202 by root, Tue Jul 5 14:02:15 2011 UTC vs.
Revision 1.209 by root, Tue Sep 27 00:41:51 2011 UTC

… …
168use common::sense; 168use common::sense;
169 169
170use base 'Exporter'; 170use base 'Exporter';
171 171
172BEGIN { 172BEGIN {
173 our $VERSION = '3.93'; 173 our $VERSION = '4.0';
174 174
175 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
176 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
177 aio_scandir aio_symlink aio_readlink aio_realpath aio_sync aio_fsync 177 aio_scandir aio_symlink aio_readlink aio_realpath aio_sync
178 aio_fdatasync aio_sync_file_range aio_pathsync aio_readahead 178 aio_fsync aio_syncfs aio_fdatasync aio_sync_file_range aio_fallocate
179 aio_pathsync aio_readahead
179 aio_rename aio_link aio_move aio_copy aio_group 180 aio_rename aio_link aio_move aio_copy aio_group
180 aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown 181 aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown
181 aio_chmod aio_utime aio_truncate 182 aio_chmod aio_utime aio_truncate
182 aio_msync aio_mtouch aio_mlock aio_mlockall 183 aio_msync aio_mtouch aio_mlock aio_mlockall
183 aio_statvfs); 184 aio_statvfs
185 aio_wd);
184 186
185 our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice)); 187 our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
186 our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush 188 our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
187 min_parallel max_parallel max_idle idle_timeout 189 min_parallel max_parallel max_idle idle_timeout
188 nreqs nready npending nthreads 190 nreqs nready npending nthreads
… …
204 206
205This section simply lists the prototypes of the most important functions 207This section simply lists the prototypes of the most important functions
206for quick reference. See the following sections for function-by-function 208for quick reference. See the following sections for function-by-function
207documentation. 209documentation.
208 210
211 aio_wd $pathname, $callback->($wd)
209 aio_open $pathname, $flags, $mode, $callback->($fh) 212 aio_open $pathname, $flags, $mode, $callback->($fh)
210 aio_close $fh, $callback->($status) 213 aio_close $fh, $callback->($status)
211 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval) 214 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
212 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval) 215 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
213 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval) 216 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
… …
218 aio_utime $fh_or_path, $atime, $mtime, $callback->($status) 221 aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
219 aio_chown $fh_or_path, $uid, $gid, $callback->($status) 222 aio_chown $fh_or_path, $uid, $gid, $callback->($status)
220 aio_truncate $fh_or_path, $offset, $callback->($status) 223 aio_truncate $fh_or_path, $offset, $callback->($status)
221 aio_chmod $fh_or_path, $mode, $callback->($status) 224 aio_chmod $fh_or_path, $mode, $callback->($status)
222 aio_unlink $pathname, $callback->($status) 225 aio_unlink $pathname, $callback->($status)
223 aio_mknod $path, $mode, $dev, $callback->($status) 226 aio_mknod $pathname, $mode, $dev, $callback->($status)
224 aio_link $srcpath, $dstpath, $callback->($status) 227 aio_link $srcpath, $dstpath, $callback->($status)
225 aio_symlink $srcpath, $dstpath, $callback->($status) 228 aio_symlink $srcpath, $dstpath, $callback->($status)
226 aio_readlink $path, $callback->($link) 229 aio_readlink $pathname, $callback->($link)
227 aio_realpath $path, $callback->($link) 230 aio_realpath $pathname, $callback->($link)
228 aio_rename $srcpath, $dstpath, $callback->($status) 231 aio_rename $srcpath, $dstpath, $callback->($status)
229 aio_mkdir $pathname, $mode, $callback->($status) 232 aio_mkdir $pathname, $mode, $callback->($status)
230 aio_rmdir $pathname, $callback->($status) 233 aio_rmdir $pathname, $callback->($status)
231 aio_readdir $pathname, $callback->($entries) 234 aio_readdir $pathname, $callback->($entries)
232 aio_readdirx $pathname, $flags, $callback->($entries, $flags) 235 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
233 IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST 236 IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
234 IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN 237 IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
235 aio_load $path, $data, $callback->($status) 238 aio_load $pathname, $data, $callback->($status)
236 aio_copy $srcpath, $dstpath, $callback->($status) 239 aio_copy $srcpath, $dstpath, $callback->($status)
237 aio_move $srcpath, $dstpath, $callback->($status) 240 aio_move $srcpath, $dstpath, $callback->($status)
238 aio_scandir $path, $maxreq, $callback->($dirs, $nondirs) 241 aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
239 aio_rmtree $path, $callback->($status) 242 aio_rmtree $pathname, $callback->($status)
240 aio_sync $callback->($status) 243 aio_sync $callback->($status)
244 aio_syncfs $fh, $callback->($status)
241 aio_fsync $fh, $callback->($status) 245 aio_fsync $fh, $callback->($status)
242 aio_fdatasync $fh, $callback->($status) 246 aio_fdatasync $fh, $callback->($status)
243 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status) 247 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
244 aio_pathsync $path, $callback->($status) 248 aio_pathsync $pathname, $callback->($status)
245 aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status) 249 aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
246 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status) 250 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
247 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status) 251 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
248 aio_mlockall $flags, $callback->($status) 252 aio_mlockall $flags, $callback->($status)
249 aio_group $callback->(...) 253 aio_group $callback->(...)
… …
288internally until the request has finished. 292internally until the request has finished.
289 293
290All functions return request objects of type L<IO::AIO::REQ> that allow 294All functions return request objects of type L<IO::AIO::REQ> that allow
291further manipulation of those requests while they are in-flight. 295further manipulation of those requests while they are in-flight.
292 296
293The pathnames you pass to these routines I<must> be absolute and 297The pathnames you pass to these routines I<should> be absolute. The
294encoded as octets. The reason for the former is that at the time the 298reason for this is that at the time the request is being executed, the
295request is being executed, the current working directory could have 299current working directory could have changed. Alternatively, you can make
296changed. Alternatively, you can make sure that you never change the 300sure that you never change the current working directory anywhere in
297current working directory anywhere in the program and then use relative 301the program and then use relative paths. Lastly, you can take advantage
298paths. 302of IO::AIOs working directory abstraction - see the description of the
303C<IO::AIO::WD> class later in this document.
299 304
300To encode pathnames as octets, either make sure you either: a) always pass 305To encode pathnames as octets, either make sure you either: a) always pass
301in filenames you got from outside (command line, readdir etc.) without 306in filenames you got from outside (command line, readdir etc.) without
302tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode 307tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode
303your pathnames to the locale (or other) encoding in effect in the user 308your pathnames to the locale (or other) encoding in effect in the user
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612 617
613Asynchronously unlink (delete) a file and call the callback with the 618Asynchronously unlink (delete) a file and call the callback with the
614result code. 619result code.
615 620
616 621
617=item aio_mknod $path, $mode, $dev, $callback->($status) 622=item aio_mknod $pathname, $mode, $dev, $callback->($status)
618 623
619[EXPERIMENTAL] 624[EXPERIMENTAL]
620 625
621Asynchronously create a device node (or fifo). See mknod(2). 626Asynchronously create a device node (or fifo). See mknod(2).
622 627
623The only (POSIX-) portable way of calling this function is: 628The only (POSIX-) portable way of calling this function is:
624 629
625 aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ... 630 aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
626 631
627See C<aio_stat> for info about some potentially helpful extra constants 632See C<aio_stat> for info about some potentially helpful extra constants
628and functions. 633and functions.
629 634
630=item aio_link $srcpath, $dstpath, $callback->($status) 635=item aio_link $srcpath, $dstpath, $callback->($status)
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637 642
638Asynchronously create a new symbolic link to the existing object at C<$srcpath> at 643Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
639the path C<$dstpath> and call the callback with the result code. 644the path C<$dstpath> and call the callback with the result code.
640 645
641 646
642=item aio_readlink $path, $callback->($link) 647=item aio_readlink $pathname, $callback->($link)
643 648
644Asynchronously read the symlink specified by C<$path> and pass it to 649Asynchronously read the symlink specified by C<$path> and pass it to
645the callback. If an error occurs, nothing or undef gets passed to the 650the callback. If an error occurs, nothing or undef gets passed to the
646callback. 651callback.
647 652
648 653
649=item aio_realpath $path, $callback->($path) 654=item aio_realpath $pathname, $callback->($path)
650 655
651Asynchronously make the path absolute and resolve any symlinks in 656Asynchronously make the path absolute and resolve any symlinks in
652C<$path>. The resulting path only consists of directories (Same as 657C<$path>. The resulting path only consists of directories (Same as
653L<Cwd::realpath>). 658L<Cwd::realpath>).
654 659
… …
685array-ref with the filenames. 690array-ref with the filenames.
686 691
687 692
688=item aio_readdirx $pathname, $flags, $callback->($entries, $flags) 693=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)
689 694
690Quite similar to C<aio_readdir>, but the C<$flags> argument allows to tune 695Quite similar to C<aio_readdir>, but the C<$flags> argument allows one to
691behaviour and output format. In case of an error, C<$entries> will be 696tune behaviour and output format. In case of an error, C<$entries> will be
692C<undef>. 697C<undef>.
693 698
694The flags are a combination of the following constants, ORed together (the 699The flags are a combination of the following constants, ORed together (the
695flags will also be passed to the callback, possibly modified): 700flags will also be passed to the callback, possibly modified):
696 701
… …
743 748
744=item IO::AIO::READDIR_FOUND_UNKNOWN 749=item IO::AIO::READDIR_FOUND_UNKNOWN
745 750
746This flag should not be set when calling C<aio_readdirx>. Instead, it 751This flag should not be set when calling C<aio_readdirx>. Instead, it
747is being set by C<aio_readdirx>, when any of the C<$type>'s found were 752is being set by C<aio_readdirx>, when any of the C<$type>'s found were
748C<IO::AIO::DT_UNKNOWN>. The absense of this flag therefore indicates that all 753C<IO::AIO::DT_UNKNOWN>. The absence of this flag therefore indicates that all
749C<$type>'s are known, which can be used to speed up some algorithms. 754C<$type>'s are known, which can be used to speed up some algorithms.
750 755
751=back 756=back
752 757
753 758
754=item aio_load $path, $data, $callback->($status) 759=item aio_load $pathname, $data, $callback->($status)
755 760
756This is a composite request that tries to fully load the given file into 761This is a composite request that tries to fully load the given file into
757memory. Status is the same as with aio_read. 762memory. Status is the same as with aio_read.
758 763
759=cut 764=cut
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894 }; 899 };
895 900
896 $grp 901 $grp
897} 902}
898 903
899=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs) 904=item aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
900 905
901Scans a directory (similar to C<aio_readdir>) but additionally tries to 906Scans a directory (similar to C<aio_readdir>) but additionally tries to
902efficiently separate the entries of directory C<$path> into two sets of 907efficiently separate the entries of directory C<$path> into two sets of
903names, directories you can recurse into (directories), and ones you cannot 908names, directories you can recurse into (directories), and ones you cannot
904recurse into (everything else, including symlinks to directories). 909recurse into (everything else, including symlinks to directories).
… …
935Then entries will be sorted into likely directories a non-initial dot 940Then entries will be sorted into likely directories a non-initial dot
936currently) and likely non-directories (see C<aio_readdirx>). Then every 941currently) and likely non-directories (see C<aio_readdirx>). Then every
937entry plus an appended C</.> will be C<stat>'ed, likely directories first, 942entry plus an appended C</.> will be C<stat>'ed, likely directories first,
938in order of their inode numbers. If that succeeds, it assumes that the 943in order of their inode numbers. If that succeeds, it assumes that the
939entry is a directory or a symlink to directory (which will be checked 944entry is a directory or a symlink to directory (which will be checked
940seperately). This is often faster than stat'ing the entry itself because 945separately). This is often faster than stat'ing the entry itself because
941filesystems might detect the type of the entry without reading the inode 946filesystems might detect the type of the entry without reading the inode
942data (e.g. ext2fs filetype feature), even on systems that cannot return 947data (e.g. ext2fs filetype feature), even on systems that cannot return
943the filetype information on readdir. 948the filetype information on readdir.
944 949
945If the known number of directories (link count - 2) has been reached, the 950If the known number of directories (link count - 2) has been reached, the
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1031 }; 1036 };
1032 1037
1033 $grp 1038 $grp
1034} 1039}
1035 1040
1036=item aio_rmtree $path, $callback->($status) 1041=item aio_rmtree $pathname, $callback->($status)
1037 1042
1038Delete a directory tree starting (and including) C<$path>, return the 1043Delete a directory tree starting (and including) C<$path>, return the
1039status of the final C<rmdir> only. This is a composite request that 1044status of the final C<rmdir> only. This is a composite request that
1040uses C<aio_scandir> to recurse into and rmdir directories, and unlink 1045uses C<aio_scandir> to recurse into and rmdir directories, and unlink
1041everything else. 1046everything else.
… …
1083callback with the fdatasync result code. 1088callback with the fdatasync result code.
1084 1089
1085If this call isn't available because your OS lacks it or it couldn't be 1090If this call isn't available because your OS lacks it or it couldn't be
1086detected, it will be emulated by calling C<fsync> instead. 1091detected, it will be emulated by calling C<fsync> instead.
1087 1092
1093=item aio_syncfs $fh, $callback->($status)
1094
1095Asynchronously call the syncfs syscall to sync the filesystem associated
1096to the given filehandle and call the callback with the syncfs result
1097code. If syncfs is not available, calls sync(), but returns C<-1> and sets
1098errno to C<ENOSYS> nevertheless.
1099
1088=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status) 1100=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
1089 1101
1090Sync the data portion of the file specified by C<$offset> and C<$length> 1102Sync the data portion of the file specified by C<$offset> and C<$length>
1091to disk (but NOT the metadata), by calling the Linux-specific 1103to disk (but NOT the metadata), by calling the Linux-specific
1092sync_file_range call. If sync_file_range is not available or it returns 1104sync_file_range call. If sync_file_range is not available or it returns
… …
1095C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>, 1107C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
1096C<IO::AIO::SYNC_FILE_RANGE_WRITE> and 1108C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
1097C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range 1109C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
1098manpage for details. 1110manpage for details.
1099 1111
1100=item aio_pathsync $path, $callback->($status) 1112=item aio_pathsync $pathname, $callback->($status)
1101 1113
1102This request tries to open, fsync and close the given path. This is a 1114This request tries to open, fsync and close the given path. This is a
1103composite request intended to sync directories after directory operations 1115composite request intended to sync directories after directory operations
1104(E.g. rename). This might not work on all operating systems or have any 1116(E.g. rename). This might not work on all operating systems or have any
1105specific effect, but usually it makes sure that directory changes get 1117specific effect, but usually it makes sure that directory changes get
… …
1248immense (it blocks a thread for a long time) so do not use this function 1260immense (it blocks a thread for a long time) so do not use this function
1249except to put your application under artificial I/O pressure. 1261except to put your application under artificial I/O pressure.
1250 1262
1251=back 1263=back
1252 1264
1265
1266=head2 IO::AIO::WD - multiple working directories
1267
1268Your process only has one current working directory, which is used by all
1269threads. This makes it hard to use relative paths (some other component
1270could call C<chdir> at any time, and it is hard to control when the path
1271will be used by IO::AIO).
1272
1273One solution for this is to always use absolute paths. This usually works,
1274but can be quite slow (the kernel has to walk the whole path on every
1275access), and can also be a hassle to implement.
1276
1277Newer POSIX systems have a number of functions (openat, fdopendir,
1278futimensat and so on) that make it possible to specify working directories
1279per operation.
1280
1281For portability, and because the clowns who "designed", or shall I write,
1282perpetrated this new interface were obviously half-drunk, this abstraction
1283cannot be perfect, though.
1284
1285IO::AIO allows you to convert directory paths into a so-called IO::AIO::WD
1286object. This object stores the canonicalised, absolute version of the
1287path, and on systems that allow it, also a directory file descriptor.
1288
1289Everywhere where a pathname is accepted by IO::AIO (e.g. in C<aio_stat>
1290or C<aio_unlink>), one can specify an array reference with an IO::AIO::WD
1291object and a pathname instead. If the pathname is absolute, the
1292IO::AIO::WD objetc is ignored, otherwise the pathname is resolved relative
1293to that IO::AIO::WD object.
1294
1295For example, to get a wd object for F</etc> and then stat F<passwd>
1296inside, you would write:
1297
1298 aio_wd "/etc", sub {
1299 my $etcdir = shift;
1300
1301 # although $etcdir can be undef on error, there is generally no reason
1302 # to check for errors here, as aio_stat will fail with ENOENT
1303 # when $etcdir is undef.
1304
1305 aio_stat [$etcdir, "passwd"], sub {
1306 # yay
1307 };
1308 };
1309
1310This shows that creating an IO::AIO::WD object is itself a potentially
1311blocking operation, which is why it is done asynchronously.
1312
1313As with normal pathnames, IO::AIO keeps a copy of the working directory
1314object and the pathname string, so you could write the following without
1315causing any issues due to C<$path> getting reused:
1316
1317 my $path = [$wd, undef];
1318
1319 for my $name (qw(abc def ghi)) {
1320 $path->[1] = $name;
1321 aio_stat $path, sub {
1322 # ...
1323 };
1324 }
1325
1326There are some caveats: when directories get renamed (or deleted), the
1327pathname string doesn't change, so will point to the new directory (or
1328nowhere at all), while the directory fd, if available on the system,
1329will still point to the original directory. Most functions accepting a
1330pathname will use the directory fd on newer systems, and the string on
1331older systems. Some functions (such as realpath) will always rely on the
1332string form of the pathname.
1333
1334So this fucntionality is mainly useful to get some protection against
1335C<chdir>, to easily get an absolute path out of a relative path for future
1336reference, and to speed up doing many operations in the same directory
1337(e.g. when stat'ing all files in a directory).
1338
1339The following functions implement this working directory abstraction:
1340
1341=over 4
1342
1343=item aio_wd $pathname, $callback->($wd)
1344
1345Asynchonously canonicalise the given pathname and convert it to an
1346IO::AIO::WD object representing it. If possible and supported on the
1347system, also open a directory fd to speed up pathname resolution relative
1348to this working directory.
1349
1350If something goes wrong, then C<undef> is passwd to the callback instead
1351of a working directory object and C<$!> is set appropriately. Since
1352passing C<undef> as working directory component of a pathname fails the
1353request with C<ENOENT>, there is often no need for error checking in the
1354C<aio_wd> callback, as future requests using the value will fail in the
1355expected way.
1356
1357If this call isn't available because your OS lacks it or it couldn't be
1358detected, it will be emulated by calling C<fsync> instead.
1359
1360=item IO::AIO::CWD
1361
1362This is a compiletime constant (object) that represents the process
1363current working directory.
1364
1365Specifying this object as working directory object for a pathname is as
1366if the pathname would be specified directly, without a directory object,
1367e.g., these calls are functionally identical:
1368
1369 aio_stat "somefile", sub { ... };
1370 aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
1371
1372=back
1373
1374
1253=head2 IO::AIO::REQ CLASS 1375=head2 IO::AIO::REQ CLASS
1254 1376
1255All non-aggregate C<aio_*> functions return an object of this class when 1377All non-aggregate C<aio_*> functions return an object of this class when
1256called in non-void context. 1378called in non-void context.
1257 1379
… …
1664 1786
1665=item IO::AIO::fadvise $fh, $offset, $len, $advice 1787=item IO::AIO::fadvise $fh, $offset, $len, $advice
1666 1788
1667Simply calls the C<posix_fadvise> function (see its 1789Simply calls the C<posix_fadvise> function (see its
1668manpage for details). The following advice constants are 1790manpage for details). The following advice constants are
1669avaiable: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>, 1791available: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,
1670C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>, 1792C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,
1671C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>. 1793C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.
1672 1794
1673On systems that do not implement C<posix_fadvise>, this function returns 1795On systems that do not implement C<posix_fadvise>, this function returns
1674ENOSYS, otherwise the return value of C<posix_fadvise>. 1796ENOSYS, otherwise the return value of C<posix_fadvise>.
1675 1797
1676=item IO::AIO::madvise $scalar, $offset, $len, $advice 1798=item IO::AIO::madvise $scalar, $offset, $len, $advice
1677 1799
1678Simply calls the C<posix_madvise> function (see its 1800Simply calls the C<posix_madvise> function (see its
1679manpage for details). The following advice constants are 1801manpage for details). The following advice constants are
1680avaiable: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>, 1802available: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,
1681C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>, C<IO::AIO::MADV_DONTNEED>. 1803C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>, C<IO::AIO::MADV_DONTNEED>.
1682 1804
1683On systems that do not implement C<posix_madvise>, this function returns 1805On systems that do not implement C<posix_madvise>, this function returns
1684ENOSYS, otherwise the return value of C<posix_madvise>. 1806ENOSYS, otherwise the return value of C<posix_madvise>.
1685 1807
1686=item IO::AIO::mprotect $scalar, $offset, $len, $protect 1808=item IO::AIO::mprotect $scalar, $offset, $len, $protect
1687 1809
1688Simply calls the C<mprotect> function on the preferably AIO::mmap'ed 1810Simply calls the C<mprotect> function on the preferably AIO::mmap'ed
1689$scalar (see its manpage for details). The following protect 1811$scalar (see its manpage for details). The following protect
1690constants are avaiable: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>, 1812constants are available: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,
1691C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>. 1813C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.
1692 1814
1693On systems that do not implement C<mprotect>, this function returns 1815On systems that do not implement C<mprotect>, this function returns
1694ENOSYS, otherwise the return value of C<mprotect>. 1816ENOSYS, otherwise the return value of C<mprotect>.
1695 1817
… …
1803=head2 FORK BEHAVIOUR 1925=head2 FORK BEHAVIOUR
1804 1926
1805Usage of pthreads in a program changes the semantics of fork 1927Usage of pthreads in a program changes the semantics of fork
1806considerably. Specifically, only async-safe functions can be called after 1928considerably. Specifically, only async-safe functions can be called after
1807fork. Perl doesn't know about this, so in general, you cannot call fork 1929fork. Perl doesn't know about this, so in general, you cannot call fork
1808with defined behaviour in perl. IO::AIO uses pthreads, so this applies, 1930with defined behaviour in perl if pthreads are involved. IO::AIO uses
1809but many other extensions and (for inexplicable reasons) perl itself often 1931pthreads, so this applies, but many other extensions and (for inexplicable
1810is linked against pthreads, so this limitation applies. 1932reasons) perl itself often is linked against pthreads, so this limitation
1933applies to quite a lot of perls.
1811 1934
1812Some operating systems have extensions that allow safe use of fork, and 1935This module no longer tries to fight your OS, or POSIX. That means IO::AIO
1813this module should do "the right thing" on those, and tries on others. At 1936only works in the process that loaded it. Forking is fully supported, but
1814the time of this writing (2011) only GNU/Linux supports these extensions 1937using IO::AIO in the child is not.
1815to POSIX. 1938
1939You might get around by not I<using> IO::AIO before (or after)
1940forking. You could also try to call the L<IO::AIO::reinit> function in the
1941child:
1942
1943=over 4
1944
1945=item IO::AIO::reinit
1946
1947Abandons all current requests and I/O threads and simply reinitialises all
1948data structures. This is not an operation supported by any standards, but
1949happens to work on GNU/Linux and some newer BSD systems.
1950
1951The only reasonable use for this function is to call it after forking, if
1952C<IO::AIO> was used in the parent. Calling it while IO::AIO is active in
1953the process will result in undefined behaviour. Calling it at any time
1954will also result in any undefined (by POSIX) behaviour.
1955
1956=back
1816 1957
1817=head2 MEMORY USAGE 1958=head2 MEMORY USAGE
1818 1959
1819Per-request usage: 1960Per-request usage:
1820 1961

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