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Revision 1.193 by root, Thu May 26 04:15:37 2011 UTC vs.
Revision 1.223 by root, Fri Apr 6 22:51:02 2012 UTC

… …
168use common::sense; 168use common::sense;
169 169
170use base 'Exporter'; 170use base 'Exporter';
171 171
172BEGIN { 172BEGIN {
173 our $VERSION = '3.8'; 173 our $VERSION = '4.13';
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_seek 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_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 aio_fiemap
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)
214 aio_seek $fh,$offset,$whence, $callback->($offs)
211 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval) 215 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
212 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval) 216 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
213 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval) 217 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
214 aio_readahead $fh,$offset,$length, $callback->($retval) 218 aio_readahead $fh,$offset,$length, $callback->($retval)
215 aio_stat $fh_or_path, $callback->($status) 219 aio_stat $fh_or_path, $callback->($status)
216 aio_lstat $fh, $callback->($status) 220 aio_lstat $fh, $callback->($status)
217 aio_statvfs $fh_or_path, $callback->($statvfs) 221 aio_statvfs $fh_or_path, $callback->($statvfs)
218 aio_utime $fh_or_path, $atime, $mtime, $callback->($status) 222 aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
219 aio_chown $fh_or_path, $uid, $gid, $callback->($status) 223 aio_chown $fh_or_path, $uid, $gid, $callback->($status)
224 aio_chmod $fh_or_path, $mode, $callback->($status)
220 aio_truncate $fh_or_path, $offset, $callback->($status) 225 aio_truncate $fh_or_path, $offset, $callback->($status)
221 aio_chmod $fh_or_path, $mode, $callback->($status)
222 aio_unlink $pathname, $callback->($status) 226 aio_unlink $pathname, $callback->($status)
223 aio_mknod $path, $mode, $dev, $callback->($status) 227 aio_mknod $pathname, $mode, $dev, $callback->($status)
224 aio_link $srcpath, $dstpath, $callback->($status) 228 aio_link $srcpath, $dstpath, $callback->($status)
225 aio_symlink $srcpath, $dstpath, $callback->($status) 229 aio_symlink $srcpath, $dstpath, $callback->($status)
226 aio_readlink $path, $callback->($link) 230 aio_readlink $pathname, $callback->($link)
231 aio_realpath $pathname, $callback->($link)
227 aio_rename $srcpath, $dstpath, $callback->($status) 232 aio_rename $srcpath, $dstpath, $callback->($status)
228 aio_mkdir $pathname, $mode, $callback->($status) 233 aio_mkdir $pathname, $mode, $callback->($status)
229 aio_rmdir $pathname, $callback->($status) 234 aio_rmdir $pathname, $callback->($status)
230 aio_readdir $pathname, $callback->($entries) 235 aio_readdir $pathname, $callback->($entries)
231 aio_readdirx $pathname, $flags, $callback->($entries, $flags) 236 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
232 IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST 237 IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
233 IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN 238 IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
239 aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
234 aio_load $path, $data, $callback->($status) 240 aio_load $pathname, $data, $callback->($status)
235 aio_copy $srcpath, $dstpath, $callback->($status) 241 aio_copy $srcpath, $dstpath, $callback->($status)
236 aio_move $srcpath, $dstpath, $callback->($status) 242 aio_move $srcpath, $dstpath, $callback->($status)
237 aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
238 aio_rmtree $path, $callback->($status) 243 aio_rmtree $pathname, $callback->($status)
239 aio_sync $callback->($status) 244 aio_sync $callback->($status)
245 aio_syncfs $fh, $callback->($status)
240 aio_fsync $fh, $callback->($status) 246 aio_fsync $fh, $callback->($status)
241 aio_fdatasync $fh, $callback->($status) 247 aio_fdatasync $fh, $callback->($status)
242 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status) 248 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
243 aio_pathsync $path, $callback->($status) 249 aio_pathsync $pathname, $callback->($status)
244 aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status) 250 aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
245 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status) 251 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
246 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status) 252 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
247 aio_mlockall $flags, $callback->($status) 253 aio_mlockall $flags, $callback->($status)
248 aio_group $callback->(...) 254 aio_group $callback->(...)
… …
271 IO::AIO::madvise $scalar, $offset, $length, $advice 277 IO::AIO::madvise $scalar, $offset, $length, $advice
272 IO::AIO::mprotect $scalar, $offset, $length, $protect 278 IO::AIO::mprotect $scalar, $offset, $length, $protect
273 IO::AIO::munlock $scalar, $offset = 0, $length = undef 279 IO::AIO::munlock $scalar, $offset = 0, $length = undef
274 IO::AIO::munlockall 280 IO::AIO::munlockall
275 281
276=head2 AIO REQUEST FUNCTIONS 282=head2 API NOTES
277 283
278All the C<aio_*> calls are more or less thin wrappers around the syscall 284All the C<aio_*> calls are more or less thin wrappers around the syscall
279with the same name (sans C<aio_>). The arguments are similar or identical, 285with the same name (sans C<aio_>). The arguments are similar or identical,
280and they all accept an additional (and optional) C<$callback> argument 286and they all accept an additional (and optional) C<$callback> argument
281which must be a code reference. This code reference will get called with 287which must be a code reference. This code reference will be called after
282the syscall return code (e.g. most syscalls return C<-1> on error, unlike 288the syscall has been executed in an asynchronous fashion. The results
283perl, which usually delivers "false") as its sole argument after the given 289of the request will be passed as arguments to the callback (and, if an
284syscall has been executed asynchronously. 290error occured, in C<$!>) - for most requests the syscall return code (e.g.
291most syscalls return C<-1> on error, unlike perl, which usually delivers
292"false").
293
294Some requests (such as C<aio_readdir>) pass the actual results and
295communicate failures by passing C<undef>.
285 296
286All functions expecting a filehandle keep a copy of the filehandle 297All functions expecting a filehandle keep a copy of the filehandle
287internally until the request has finished. 298internally until the request has finished.
288 299
289All functions return request objects of type L<IO::AIO::REQ> that allow 300All functions return request objects of type L<IO::AIO::REQ> that allow
290further manipulation of those requests while they are in-flight. 301further manipulation of those requests while they are in-flight.
291 302
292The pathnames you pass to these routines I<must> be absolute and 303The pathnames you pass to these routines I<should> be absolute. The
293encoded as octets. The reason for the former is that at the time the 304reason for this is that at the time the request is being executed, the
294request is being executed, the current working directory could have 305current working directory could have changed. Alternatively, you can
295changed. Alternatively, you can make sure that you never change the 306make sure that you never change the current working directory anywhere
296current working directory anywhere in the program and then use relative 307in the program and then use relative paths. You can also take advantage
297paths. 308of IO::AIOs working directory abstraction, that lets you specify paths
309relative to some previously-opened "working directory object" - see the
310description of the C<IO::AIO::WD> class later in this document.
298 311
299To encode pathnames as octets, either make sure you either: a) always pass 312To encode pathnames as octets, either make sure you either: a) always pass
300in filenames you got from outside (command line, readdir etc.) without 313in filenames you got from outside (command line, readdir etc.) without
301tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode 314tinkering, b) are in your native filesystem encoding, c) use the Encode
302your pathnames to the locale (or other) encoding in effect in the user 315module and encode your pathnames to the locale (or other) encoding in
303environment, d) use Glib::filename_from_unicode on unicode filenames or e) 316effect in the user environment, d) use Glib::filename_from_unicode on
304use something else to ensure your scalar has the correct contents. 317unicode filenames or e) use something else to ensure your scalar has the
318correct contents.
305 319
306This works, btw. independent of the internal UTF-8 bit, which IO::AIO 320This works, btw. independent of the internal UTF-8 bit, which IO::AIO
307handles correctly whether it is set or not. 321handles correctly whether it is set or not.
322
323=head2 AIO REQUEST FUNCTIONS
308 324
309=over 4 325=over 4
310 326
311=item $prev_pri = aioreq_pri [$pri] 327=item $prev_pri = aioreq_pri [$pri]
312 328
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368 } else { 384 } else {
369 die "open failed: $!\n"; 385 die "open failed: $!\n";
370 } 386 }
371 }; 387 };
372 388
389In addition to all the common open modes/flags (C<O_RDONLY>, C<O_WRONLY>,
390C<O_RDWR>, C<O_CREAT>, C<O_TRUNC>, C<O_EXCL> and C<O_APPEND>), the
391following POSIX and non-POSIX constants are available (missing ones on
392your system are, as usual, C<0>):
393
394C<O_ASYNC>, C<O_DIRECT>, C<O_NOATIME>, C<O_CLOEXEC>, C<O_NOCTTY>, C<O_NOFOLLOW>,
395C<O_NONBLOCK>, C<O_EXEC>, C<O_SEARCH>, C<O_DIRECTORY>, C<O_DSYNC>,
396C<O_RSYNC>, C<O_SYNC> and C<O_TTY_INIT>.
397
373 398
374=item aio_close $fh, $callback->($status) 399=item aio_close $fh, $callback->($status)
375 400
376Asynchronously close a file and call the callback with the result 401Asynchronously close a file and call the callback with the result
377code. 402code.
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385 410
386Or in other words: the file descriptor will be closed, but it will not be 411Or in other words: the file descriptor will be closed, but it will not be
387free for reuse until the perl filehandle is closed. 412free for reuse until the perl filehandle is closed.
388 413
389=cut 414=cut
415
416=item aio_seek $fh, $offset, $whence, $callback->($offs)
417
418Seeks the filehandle to the new C<$offset>, similarly to perl's
419C<sysseek>. The C<$whence> can use the traditional values (C<0> for
420C<IO::AIO::SEEK_SET>, C<1> for C<IO::AIO::SEEK_CUR> or C<2> for
421C<IO::AIO::SEEK_END>).
422
423The resulting absolute offset will be passed to the callback, or C<-1> in
424case of an error.
425
426In theory, the C<$whence> constants could be different than the
427corresponding values from L<Fcntl>, but perl guarantees they are the same,
428so don't panic.
390 429
391=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval) 430=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
392 431
393=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval) 432=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
394 433
… …
427 466
428Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts 467Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
429reading at byte offset C<$in_offset>, and starts writing at the current 468reading at byte offset C<$in_offset>, and starts writing at the current
430file offset of C<$out_fh>. Because of that, it is not safe to issue more 469file offset of C<$out_fh>. Because of that, it is not safe to issue more
431than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each 470than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
432other. 471other. The same C<$in_fh> works fine though, as this function does not
472move or use the file offset of C<$in_fh>.
433 473
434Please note that C<aio_sendfile> can read more bytes from C<$in_fh> than 474Please note that C<aio_sendfile> can read more bytes from C<$in_fh> than
435are written, and there is no way to find out how many bytes have been read 475are written, and there is no way to find out how many more bytes have been
436from C<aio_sendfile> alone, as C<aio_sendfile> only provides the number of 476read from C<aio_sendfile> alone, as C<aio_sendfile> only provides the
437bytes written to C<$out_fh>. Only if the result value equals C<$length> 477number of bytes written to C<$out_fh>. Only if the result value equals
438one can assume that C<$length> bytes have been read. 478C<$length> one can assume that C<$length> bytes have been read.
439 479
440Unlike with other C<aio_> functions, it makes a lot of sense to use 480Unlike with other C<aio_> functions, it makes a lot of sense to use
441C<aio_sendfile> on non-blocking sockets, as long as one end (typically 481C<aio_sendfile> on non-blocking sockets, as long as one end (typically
442the C<$in_fh>) is a file - the file I/O will then be asynchronous, while 482the C<$in_fh>) is a file - the file I/O will then be asynchronous, while
443the socket I/O will be non-blocking. Note, however, that you can run into 483the socket I/O will be non-blocking. Note, however, that you can run
444a trap where C<aio_sendfile> reads some data with readahead, then fails 484into a trap where C<aio_sendfile> reads some data with readahead, then
445to write all data, and when the socket is ready the next time, the data 485fails to write all data, and when the socket is ready the next time, the
446in the cache is already lost, forcing C<aio_sendfile> to again hit the 486data in the cache is already lost, forcing C<aio_sendfile> to again hit
447disk. Explicit C<aio_read> + C<aio_write> let's you control resource usage 487the disk. Explicit C<aio_read> + C<aio_write> let's you better control
448much better. 488resource usage.
449 489
450This call tries to make use of a native C<sendfile> syscall to provide 490This call tries to make use of a native C<sendfile>-like syscall to
451zero-copy operation. For this to work, C<$out_fh> should refer to a 491provide zero-copy operation. For this to work, C<$out_fh> should refer to
452socket, and C<$in_fh> should refer to an mmap'able file. 492a socket, and C<$in_fh> should refer to an mmap'able file.
453 493
454If a native sendfile cannot be found or it fails with C<ENOSYS>, 494If a native sendfile cannot be found or it fails with C<ENOSYS>,
455C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or C<ENOTSOCK>, 495C<EINVAL>, C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or
456it will be emulated, so you can call C<aio_sendfile> on any type of 496C<ENOTSOCK>, it will be emulated, so you can call C<aio_sendfile> on any
457filehandle regardless of the limitations of the operating system. 497type of filehandle regardless of the limitations of the operating system.
498
499As native sendfile syscalls (as practically any non-POSIX interface hacked
500together in a hurry to improve benchmark numbers) tend to be rather buggy
501on many systems, this implementation tries to work around some known bugs
502in Linux and FreeBSD kernels (probably others, too), but that might fail,
503so you really really should check the return value of C<aio_sendfile> -
504fewre bytes than expected might have been transferred.
458 505
459 506
460=item aio_readahead $fh,$offset,$length, $callback->($retval) 507=item aio_readahead $fh,$offset,$length, $callback->($retval)
461 508
462C<aio_readahead> populates the page cache with data from a file so that 509C<aio_readahead> populates the page cache with data from a file so that
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594 641
595Asynchronously unlink (delete) a file and call the callback with the 642Asynchronously unlink (delete) a file and call the callback with the
596result code. 643result code.
597 644
598 645
599=item aio_mknod $path, $mode, $dev, $callback->($status) 646=item aio_mknod $pathname, $mode, $dev, $callback->($status)
600 647
601[EXPERIMENTAL] 648[EXPERIMENTAL]
602 649
603Asynchronously create a device node (or fifo). See mknod(2). 650Asynchronously create a device node (or fifo). See mknod(2).
604 651
605The only (POSIX-) portable way of calling this function is: 652The only (POSIX-) portable way of calling this function is:
606 653
607 aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ... 654 aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
608 655
609See C<aio_stat> for info about some potentially helpful extra constants 656See C<aio_stat> for info about some potentially helpful extra constants
610and functions. 657and functions.
611 658
612=item aio_link $srcpath, $dstpath, $callback->($status) 659=item aio_link $srcpath, $dstpath, $callback->($status)
… …
619 666
620Asynchronously create a new symbolic link to the existing object at C<$srcpath> at 667Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
621the path C<$dstpath> and call the callback with the result code. 668the path C<$dstpath> and call the callback with the result code.
622 669
623 670
624=item aio_readlink $path, $callback->($link) 671=item aio_readlink $pathname, $callback->($link)
625 672
626Asynchronously read the symlink specified by C<$path> and pass it to 673Asynchronously read the symlink specified by C<$path> and pass it to
627the callback. If an error occurs, nothing or undef gets passed to the 674the callback. If an error occurs, nothing or undef gets passed to the
628callback. 675callback.
629 676
630 677
678=item aio_realpath $pathname, $callback->($path)
679
680Asynchronously make the path absolute and resolve any symlinks in
681C<$path>. The resulting path only consists of directories (Same as
682L<Cwd::realpath>).
683
684This request can be used to get the absolute path of the current working
685directory by passing it a path of F<.> (a single dot).
686
687
631=item aio_rename $srcpath, $dstpath, $callback->($status) 688=item aio_rename $srcpath, $dstpath, $callback->($status)
632 689
633Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as 690Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
634rename(2) and call the callback with the result code. 691rename(2) and call the callback with the result code.
635 692
… …
657array-ref with the filenames. 714array-ref with the filenames.
658 715
659 716
660=item aio_readdirx $pathname, $flags, $callback->($entries, $flags) 717=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)
661 718
662Quite similar to C<aio_readdir>, but the C<$flags> argument allows to tune 719Quite similar to C<aio_readdir>, but the C<$flags> argument allows one to
663behaviour and output format. In case of an error, C<$entries> will be 720tune behaviour and output format. In case of an error, C<$entries> will be
664C<undef>. 721C<undef>.
665 722
666The flags are a combination of the following constants, ORed together (the 723The flags are a combination of the following constants, ORed together (the
667flags will also be passed to the callback, possibly modified): 724flags will also be passed to the callback, possibly modified):
668 725
… …
715 772
716=item IO::AIO::READDIR_FOUND_UNKNOWN 773=item IO::AIO::READDIR_FOUND_UNKNOWN
717 774
718This flag should not be set when calling C<aio_readdirx>. Instead, it 775This flag should not be set when calling C<aio_readdirx>. Instead, it
719is being set by C<aio_readdirx>, when any of the C<$type>'s found were 776is being set by C<aio_readdirx>, when any of the C<$type>'s found were
720C<IO::AIO::DT_UNKNOWN>. The absense of this flag therefore indicates that all 777C<IO::AIO::DT_UNKNOWN>. The absence of this flag therefore indicates that all
721C<$type>'s are known, which can be used to speed up some algorithms. 778C<$type>'s are known, which can be used to speed up some algorithms.
722 779
723=back 780=back
724 781
725 782
726=item aio_load $path, $data, $callback->($status) 783=item aio_load $pathname, $data, $callback->($status)
727 784
728This is a composite request that tries to fully load the given file into 785This is a composite request that tries to fully load the given file into
729memory. Status is the same as with aio_read. 786memory. Status is the same as with aio_read.
730 787
731=cut 788=cut
… …
853 if ($_[0] && $! == EXDEV) { 910 if ($_[0] && $! == EXDEV) {
854 aioreq_pri $pri; 911 aioreq_pri $pri;
855 add $grp aio_copy $src, $dst, sub { 912 add $grp aio_copy $src, $dst, sub {
856 $grp->result ($_[0]); 913 $grp->result ($_[0]);
857 914
858 if (!$_[0]) { 915 unless ($_[0]) {
859 aioreq_pri $pri; 916 aioreq_pri $pri;
860 add $grp aio_unlink $src; 917 add $grp aio_unlink $src;
861 } 918 }
862 }; 919 };
863 } else { 920 } else {
… …
866 }; 923 };
867 924
868 $grp 925 $grp
869} 926}
870 927
871=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs) 928=item aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
872 929
873Scans a directory (similar to C<aio_readdir>) but additionally tries to 930Scans a directory (similar to C<aio_readdir>) but additionally tries to
874efficiently separate the entries of directory C<$path> into two sets of 931efficiently separate the entries of directory C<$path> into two sets of
875names, directories you can recurse into (directories), and ones you cannot 932names, directories you can recurse into (directories), and ones you cannot
876recurse into (everything else, including symlinks to directories). 933recurse into (everything else, including symlinks to directories).
… …
907Then entries will be sorted into likely directories a non-initial dot 964Then entries will be sorted into likely directories a non-initial dot
908currently) and likely non-directories (see C<aio_readdirx>). Then every 965currently) and likely non-directories (see C<aio_readdirx>). Then every
909entry plus an appended C</.> will be C<stat>'ed, likely directories first, 966entry plus an appended C</.> will be C<stat>'ed, likely directories first,
910in order of their inode numbers. If that succeeds, it assumes that the 967in order of their inode numbers. If that succeeds, it assumes that the
911entry is a directory or a symlink to directory (which will be checked 968entry is a directory or a symlink to directory (which will be checked
912seperately). This is often faster than stat'ing the entry itself because 969separately). This is often faster than stat'ing the entry itself because
913filesystems might detect the type of the entry without reading the inode 970filesystems might detect the type of the entry without reading the inode
914data (e.g. ext2fs filetype feature), even on systems that cannot return 971data (e.g. ext2fs filetype feature), even on systems that cannot return
915the filetype information on readdir. 972the filetype information on readdir.
916 973
917If the known number of directories (link count - 2) has been reached, the 974If the known number of directories (link count - 2) has been reached, the
… …
933 990
934 my $grp = aio_group $cb; 991 my $grp = aio_group $cb;
935 992
936 $maxreq = 4 if $maxreq <= 0; 993 $maxreq = 4 if $maxreq <= 0;
937 994
938 # stat once 995 # get a wd object
939 aioreq_pri $pri; 996 aioreq_pri $pri;
940 add $grp aio_stat $path, sub { 997 add $grp aio_wd $path, sub {
998 $_[0]
941 return $grp->result () if $_[0]; 999 or return $grp->result ();
942 my $now = time;
943 my $hash1 = join ":", (stat _)[0,1,3,7,9];
944 1000
945 # read the directory entries 1001 my $wd = [shift, "."];
1002
1003 # stat once
946 aioreq_pri $pri; 1004 aioreq_pri $pri;
947 add $grp aio_readdirx $path, READDIR_DIRS_FIRST, sub { 1005 add $grp aio_stat $wd, sub {
948 my $entries = shift
949 or return $grp->result (); 1006 return $grp->result () if $_[0];
1007 my $now = time;
1008 my $hash1 = join ":", (stat _)[0,1,3,7,9];
950 1009
951 # stat the dir another time 1010 # read the directory entries
952 aioreq_pri $pri; 1011 aioreq_pri $pri;
1012 add $grp aio_readdirx $wd, READDIR_DIRS_FIRST, sub {
1013 my $entries = shift
1014 or return $grp->result ();
1015
1016 # stat the dir another time
1017 aioreq_pri $pri;
953 add $grp aio_stat $path, sub { 1018 add $grp aio_stat $wd, sub {
954 my $hash2 = join ":", (stat _)[0,1,3,7,9]; 1019 my $hash2 = join ":", (stat _)[0,1,3,7,9];
955 1020
956 my $ndirs; 1021 my $ndirs;
957 1022
958 # take the slow route if anything looks fishy 1023 # take the slow route if anything looks fishy
959 if ($hash1 ne $hash2 or (stat _)[9] == $now) { 1024 if ($hash1 ne $hash2 or (stat _)[9] == $now) {
960 $ndirs = -1; 1025 $ndirs = -1;
961 } else { 1026 } else {
962 # if nlink == 2, we are finished 1027 # if nlink == 2, we are finished
963 # for non-posix-fs's, we rely on nlink < 2 1028 # for non-posix-fs's, we rely on nlink < 2
964 $ndirs = (stat _)[3] - 2 1029 $ndirs = (stat _)[3] - 2
965 or return $grp->result ([], $entries); 1030 or return $grp->result ([], $entries);
966 } 1031 }
967 1032
968 my (@dirs, @nondirs); 1033 my (@dirs, @nondirs);
969 1034
970 my $statgrp = add $grp aio_group sub { 1035 my $statgrp = add $grp aio_group sub {
971 $grp->result (\@dirs, \@nondirs); 1036 $grp->result (\@dirs, \@nondirs);
972 }; 1037 };
973 1038
974 limit $statgrp $maxreq; 1039 limit $statgrp $maxreq;
975 feed $statgrp sub { 1040 feed $statgrp sub {
976 return unless @$entries; 1041 return unless @$entries;
977 my $entry = shift @$entries; 1042 my $entry = shift @$entries;
978 1043
979 aioreq_pri $pri; 1044 aioreq_pri $pri;
1045 $wd->[1] = "$entry/.";
980 add $statgrp aio_stat "$path/$entry/.", sub { 1046 add $statgrp aio_stat $wd, sub {
981 if ($_[0] < 0) { 1047 if ($_[0] < 0) {
982 push @nondirs, $entry; 1048 push @nondirs, $entry;
983 } else { 1049 } else {
984 # need to check for real directory 1050 # need to check for real directory
985 aioreq_pri $pri; 1051 aioreq_pri $pri;
1052 $wd->[1] = $entry;
986 add $statgrp aio_lstat "$path/$entry", sub { 1053 add $statgrp aio_lstat $wd, sub {
987 if (-d _) { 1054 if (-d _) {
988 push @dirs, $entry; 1055 push @dirs, $entry;
989 1056
990 unless (--$ndirs) { 1057 unless (--$ndirs) {
991 push @nondirs, @$entries; 1058 push @nondirs, @$entries;
992 feed $statgrp; 1059 feed $statgrp;
1060 }
1061 } else {
1062 push @nondirs, $entry;
993 } 1063 }
994 } else {
995 push @nondirs, $entry;
996 } 1064 }
997 } 1065 }
998 } 1066 };
999 }; 1067 };
1000 }; 1068 };
1001 }; 1069 };
1002 }; 1070 };
1003 }; 1071 };
1004 1072
1005 $grp 1073 $grp
1006} 1074}
1007 1075
1008=item aio_rmtree $path, $callback->($status) 1076=item aio_rmtree $pathname, $callback->($status)
1009 1077
1010Delete a directory tree starting (and including) C<$path>, return the 1078Delete a directory tree starting (and including) C<$path>, return the
1011status of the final C<rmdir> only. This is a composite request that 1079status of the final C<rmdir> only. This is a composite request that
1012uses C<aio_scandir> to recurse into and rmdir directories, and unlink 1080uses C<aio_scandir> to recurse into and rmdir directories, and unlink
1013everything else. 1081everything else.
… …
1055callback with the fdatasync result code. 1123callback with the fdatasync result code.
1056 1124
1057If this call isn't available because your OS lacks it or it couldn't be 1125If this call isn't available because your OS lacks it or it couldn't be
1058detected, it will be emulated by calling C<fsync> instead. 1126detected, it will be emulated by calling C<fsync> instead.
1059 1127
1128=item aio_syncfs $fh, $callback->($status)
1129
1130Asynchronously call the syncfs syscall to sync the filesystem associated
1131to the given filehandle and call the callback with the syncfs result
1132code. If syncfs is not available, calls sync(), but returns C<-1> and sets
1133errno to C<ENOSYS> nevertheless.
1134
1060=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status) 1135=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
1061 1136
1062Sync the data portion of the file specified by C<$offset> and C<$length> 1137Sync the data portion of the file specified by C<$offset> and C<$length>
1063to disk (but NOT the metadata), by calling the Linux-specific 1138to disk (but NOT the metadata), by calling the Linux-specific
1064sync_file_range call. If sync_file_range is not available or it returns 1139sync_file_range call. If sync_file_range is not available or it returns
… …
1067C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>, 1142C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
1068C<IO::AIO::SYNC_FILE_RANGE_WRITE> and 1143C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
1069C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range 1144C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
1070manpage for details. 1145manpage for details.
1071 1146
1072=item aio_pathsync $path, $callback->($status) 1147=item aio_pathsync $pathname, $callback->($status)
1073 1148
1074This request tries to open, fsync and close the given path. This is a 1149This request tries to open, fsync and close the given path. This is a
1075composite request intended to sync directories after directory operations 1150composite request intended to sync directories after directory operations
1076(E.g. rename). This might not work on all operating systems or have any 1151(E.g. rename). This might not work on all operating systems or have any
1077specific effect, but usually it makes sure that directory changes get 1152specific effect, but usually it makes sure that directory changes get
… …
1174 1249
1175Example: asynchronously lock all current and future pages into memory. 1250Example: asynchronously lock all current and future pages into memory.
1176 1251
1177 aio_mlockall IO::AIO::MCL_FUTURE; 1252 aio_mlockall IO::AIO::MCL_FUTURE;
1178 1253
1254=item aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
1255
1256Queries the extents of the given file (by calling the Linux FIEMAP ioctl,
1257see L<http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for details). If the
1258C<ioctl> is not available on your OS, then this rquiest will fail with
1259C<ENOSYS>.
1260
1261C<$start> is the starting offset to query extents for, C<$length> is the
1262size of the range to query - if it is C<undef>, then the whole file will
1263be queried.
1264
1265C<$flags> is a combination of flags (C<IO::AIO::FIEMAP_FLAG_SYNC> or
1266C<IO::AIO::FIEMAP_FLAG_XATTR> - C<IO::AIO::FIEMAP_FLAGS_COMPAT> is also
1267exported), and is normally C<0> or C<IO::AIO::FIEMAP_FLAG_SYNC> to query
1268the data portion.
1269
1270C<$count> is the maximum number of extent records to return. If it is
1271C<undef>, then IO::AIO queries all extents of the file. As a very special
1272case, if it is C<0>, then the callback receives the number of extents
1273instead of the extents themselves.
1274
1275If an error occurs, the callback receives no arguments. The special
1276C<errno> value C<IO::AIO::EBADR> is available to test for flag errors.
1277
1278Otherwise, the callback receives an array reference with extent
1279structures. Each extent structure is an array reference itself, with the
1280following members:
1281
1282 [$logical, $physical, $length, $flags]
1283
1284Flags is any combination of the following flag values (typically either C<0>
1285or C<IO::AIO::FIEMAP_EXTENT_LAST>):
1286
1287C<IO::AIO::FIEMAP_EXTENT_LAST>, C<IO::AIO::FIEMAP_EXTENT_UNKNOWN>,
1288C<IO::AIO::FIEMAP_EXTENT_DELALLOC>, C<IO::AIO::FIEMAP_EXTENT_ENCODED>,
1289C<IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED>, C<IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED>,
1290C<IO::AIO::FIEMAP_EXTENT_DATA_INLINE>, C<IO::AIO::FIEMAP_EXTENT_DATA_TAIL>,
1291C<IO::AIO::FIEMAP_EXTENT_UNWRITTEN>, C<IO::AIO::FIEMAP_EXTENT_MERGED> or
1292C<IO::AIO::FIEMAP_EXTENT_SHARED>.
1293
1179=item aio_group $callback->(...) 1294=item aio_group $callback->(...)
1180 1295
1181This is a very special aio request: Instead of doing something, it is a 1296This is a very special aio request: Instead of doing something, it is a
1182container for other aio requests, which is useful if you want to bundle 1297container for other aio requests, which is useful if you want to bundle
1183many requests into a single, composite, request with a definite callback 1298many requests into a single, composite, request with a definite callback
… …
1219like sleep and file handle readable/writable, the overhead this creates is 1334like sleep and file handle readable/writable, the overhead this creates is
1220immense (it blocks a thread for a long time) so do not use this function 1335immense (it blocks a thread for a long time) so do not use this function
1221except to put your application under artificial I/O pressure. 1336except to put your application under artificial I/O pressure.
1222 1337
1223=back 1338=back
1339
1340
1341=head2 IO::AIO::WD - multiple working directories
1342
1343Your process only has one current working directory, which is used by all
1344threads. This makes it hard to use relative paths (some other component
1345could call C<chdir> at any time, and it is hard to control when the path
1346will be used by IO::AIO).
1347
1348One solution for this is to always use absolute paths. This usually works,
1349but can be quite slow (the kernel has to walk the whole path on every
1350access), and can also be a hassle to implement.
1351
1352Newer POSIX systems have a number of functions (openat, fdopendir,
1353futimensat and so on) that make it possible to specify working directories
1354per operation.
1355
1356For portability, and because the clowns who "designed", or shall I write,
1357perpetrated this new interface were obviously half-drunk, this abstraction
1358cannot be perfect, though.
1359
1360IO::AIO allows you to convert directory paths into a so-called IO::AIO::WD
1361object. This object stores the canonicalised, absolute version of the
1362path, and on systems that allow it, also a directory file descriptor.
1363
1364Everywhere where a pathname is accepted by IO::AIO (e.g. in C<aio_stat>
1365or C<aio_unlink>), one can specify an array reference with an IO::AIO::WD
1366object and a pathname instead (or the IO::AIO::WD object alone, which
1367gets interpreted as C<[$wd, "."]>). If the pathname is absolute, the
1368IO::AIO::WD object is ignored, otherwise the pathname is resolved relative
1369to that IO::AIO::WD object.
1370
1371For example, to get a wd object for F</etc> and then stat F<passwd>
1372inside, you would write:
1373
1374 aio_wd "/etc", sub {
1375 my $etcdir = shift;
1376
1377 # although $etcdir can be undef on error, there is generally no reason
1378 # to check for errors here, as aio_stat will fail with ENOENT
1379 # when $etcdir is undef.
1380
1381 aio_stat [$etcdir, "passwd"], sub {
1382 # yay
1383 };
1384 };
1385
1386That C<aio_wd> is a request and not a normal function shows that creating
1387an IO::AIO::WD object is itself a potentially blocking operation, which is
1388why it is done asynchronously.
1389
1390To stat the directory obtained with C<aio_wd> above, one could write
1391either of the following three request calls:
1392
1393 aio_lstat "/etc" , sub { ... # pathname as normal string
1394 aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
1395 aio_lstat $wd , sub { ... # shorthand for the previous
1396
1397As with normal pathnames, IO::AIO keeps a copy of the working directory
1398object and the pathname string, so you could write the following without
1399causing any issues due to C<$path> getting reused:
1400
1401 my $path = [$wd, undef];
1402
1403 for my $name (qw(abc def ghi)) {
1404 $path->[1] = $name;
1405 aio_stat $path, sub {
1406 # ...
1407 };
1408 }
1409
1410There are some caveats: when directories get renamed (or deleted), the
1411pathname string doesn't change, so will point to the new directory (or
1412nowhere at all), while the directory fd, if available on the system,
1413will still point to the original directory. Most functions accepting a
1414pathname will use the directory fd on newer systems, and the string on
1415older systems. Some functions (such as realpath) will always rely on the
1416string form of the pathname.
1417
1418So this fucntionality is mainly useful to get some protection against
1419C<chdir>, to easily get an absolute path out of a relative path for future
1420reference, and to speed up doing many operations in the same directory
1421(e.g. when stat'ing all files in a directory).
1422
1423The following functions implement this working directory abstraction:
1424
1425=over 4
1426
1427=item aio_wd $pathname, $callback->($wd)
1428
1429Asynchonously canonicalise the given pathname and convert it to an
1430IO::AIO::WD object representing it. If possible and supported on the
1431system, also open a directory fd to speed up pathname resolution relative
1432to this working directory.
1433
1434If something goes wrong, then C<undef> is passwd to the callback instead
1435of a working directory object and C<$!> is set appropriately. Since
1436passing C<undef> as working directory component of a pathname fails the
1437request with C<ENOENT>, there is often no need for error checking in the
1438C<aio_wd> callback, as future requests using the value will fail in the
1439expected way.
1440
1441If this call isn't available because your OS lacks it or it couldn't be
1442detected, it will be emulated by calling C<fsync> instead.
1443
1444=item IO::AIO::CWD
1445
1446This is a compiletime constant (object) that represents the process
1447current working directory.
1448
1449Specifying this object as working directory object for a pathname is as
1450if the pathname would be specified directly, without a directory object,
1451e.g., these calls are functionally identical:
1452
1453 aio_stat "somefile", sub { ... };
1454 aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
1455
1456=back
1457
1224 1458
1225=head2 IO::AIO::REQ CLASS 1459=head2 IO::AIO::REQ CLASS
1226 1460
1227All non-aggregate C<aio_*> functions return an object of this class when 1461All non-aggregate C<aio_*> functions return an object of this class when
1228called in non-void context. 1462called in non-void context.
… …
1346 1580
1347Sets a feeder/generator on this group: every group can have an attached 1581Sets a feeder/generator on this group: every group can have an attached
1348generator that generates requests if idle. The idea behind this is that, 1582generator that generates requests if idle. The idea behind this is that,
1349although you could just queue as many requests as you want in a group, 1583although you could just queue as many requests as you want in a group,
1350this might starve other requests for a potentially long time. For example, 1584this might starve other requests for a potentially long time. For example,
1351C<aio_scandir> might generate hundreds of thousands C<aio_stat> requests, 1585C<aio_scandir> might generate hundreds of thousands of C<aio_stat>
1352delaying any later requests for a long time. 1586requests, delaying any later requests for a long time.
1353 1587
1354To avoid this, and allow incremental generation of requests, you can 1588To avoid this, and allow incremental generation of requests, you can
1355instead a group and set a feeder on it that generates those requests. The 1589instead a group and set a feeder on it that generates those requests. The
1356feed callback will be called whenever there are few enough (see C<limit>, 1590feed callback will be called whenever there are few enough (see C<limit>,
1357below) requests active in the group itself and is expected to queue more 1591below) requests active in the group itself and is expected to queue more
… …
1555Sets the minimum idle timeout (default 10) after which worker threads are 1789Sets the minimum idle timeout (default 10) after which worker threads are
1556allowed to exit. SEe C<IO::AIO::max_idle>. 1790allowed to exit. SEe C<IO::AIO::max_idle>.
1557 1791
1558=item IO::AIO::max_outstanding $maxreqs 1792=item IO::AIO::max_outstanding $maxreqs
1559 1793
1794Sets the maximum number of outstanding requests to C<$nreqs>. If
1795you do queue up more than this number of requests, the next call to
1796C<IO::AIO::poll_cb> (and other functions calling C<poll_cb>, such as
1797C<IO::AIO::flush> or C<IO::AIO::poll>) will block until the limit is no
1798longer exceeded.
1799
1800In other words, this setting does not enforce a queue limit, but can be
1801used to make poll functions block if the limit is exceeded.
1802
1560This is a very bad function to use in interactive programs because it 1803This is a very bad function to use in interactive programs because it
1561blocks, and a bad way to reduce concurrency because it is inexact: Better 1804blocks, and a bad way to reduce concurrency because it is inexact: Better
1562use an C<aio_group> together with a feed callback. 1805use an C<aio_group> together with a feed callback.
1563 1806
1564Sets the maximum number of outstanding requests to C<$nreqs>. If you 1807It's main use is in scripts without an event loop - when you want to stat
1565do queue up more than this number of requests, the next call to the 1808a lot of files, you can write somehting like this:
1566C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
1567function will block until the limit is no longer exceeded.
1568 1809
1569The default value is very large, so there is no practical limit on the 1810 IO::AIO::max_outstanding 32;
1570number of outstanding requests.
1571 1811
1572You can still queue as many requests as you want. Therefore, 1812 for my $path (...) {
1573C<max_outstanding> is mainly useful in simple scripts (with low values) or 1813 aio_stat $path , ...;
1574as a stop gap to shield against fatal memory overflow (with large values). 1814 IO::AIO::poll_cb;
1815 }
1816
1817 IO::AIO::flush;
1818
1819The call to C<poll_cb> inside the loop will normally return instantly, but
1820as soon as more thna C<32> reqeusts are in-flight, it will block until
1821some requests have been handled. This keeps the loop from pushing a large
1822number of C<aio_stat> requests onto the queue.
1823
1824The default value for C<max_outstanding> is very large, so there is no
1825practical limit on the number of outstanding requests.
1575 1826
1576=back 1827=back
1577 1828
1578=head3 STATISTICAL INFORMATION 1829=head3 STATISTICAL INFORMATION
1579 1830
… …
1619 1870
1620=item IO::AIO::fadvise $fh, $offset, $len, $advice 1871=item IO::AIO::fadvise $fh, $offset, $len, $advice
1621 1872
1622Simply calls the C<posix_fadvise> function (see its 1873Simply calls the C<posix_fadvise> function (see its
1623manpage for details). The following advice constants are 1874manpage for details). The following advice constants are
1624avaiable: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>, 1875available: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,
1625C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>, 1876C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,
1626C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>. 1877C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.
1627 1878
1628On systems that do not implement C<posix_fadvise>, this function returns 1879On systems that do not implement C<posix_fadvise>, this function returns
1629ENOSYS, otherwise the return value of C<posix_fadvise>. 1880ENOSYS, otherwise the return value of C<posix_fadvise>.
1630 1881
1631=item IO::AIO::madvise $scalar, $offset, $len, $advice 1882=item IO::AIO::madvise $scalar, $offset, $len, $advice
1632 1883
1633Simply calls the C<posix_madvise> function (see its 1884Simply calls the C<posix_madvise> function (see its
1634manpage for details). The following advice constants are 1885manpage for details). The following advice constants are
1635avaiable: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>, 1886available: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,
1636C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>, C<IO::AIO::MADV_DONTNEED>. 1887C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>, C<IO::AIO::MADV_DONTNEED>.
1637 1888
1638On systems that do not implement C<posix_madvise>, this function returns 1889On systems that do not implement C<posix_madvise>, this function returns
1639ENOSYS, otherwise the return value of C<posix_madvise>. 1890ENOSYS, otherwise the return value of C<posix_madvise>.
1640 1891
1641=item IO::AIO::mprotect $scalar, $offset, $len, $protect 1892=item IO::AIO::mprotect $scalar, $offset, $len, $protect
1642 1893
1643Simply calls the C<mprotect> function on the preferably AIO::mmap'ed 1894Simply calls the C<mprotect> function on the preferably AIO::mmap'ed
1644$scalar (see its manpage for details). The following protect 1895$scalar (see its manpage for details). The following protect
1645constants are avaiable: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>, 1896constants are available: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,
1646C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>. 1897C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.
1647 1898
1648On systems that do not implement C<mprotect>, this function returns 1899On systems that do not implement C<mprotect>, this function returns
1649ENOSYS, otherwise the return value of C<mprotect>. 1900ENOSYS, otherwise the return value of C<mprotect>.
1650 1901
… …
1755 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno => 2006 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
1756 \&IO::AIO::poll_cb); 2007 \&IO::AIO::poll_cb);
1757 2008
1758=head2 FORK BEHAVIOUR 2009=head2 FORK BEHAVIOUR
1759 2010
1760This module should do "the right thing" when the process using it forks: 2011Usage of pthreads in a program changes the semantics of fork
2012considerably. Specifically, only async-safe functions can be called after
2013fork. Perl doesn't know about this, so in general, you cannot call fork
2014with defined behaviour in perl if pthreads are involved. IO::AIO uses
2015pthreads, so this applies, but many other extensions and (for inexplicable
2016reasons) perl itself often is linked against pthreads, so this limitation
2017applies to quite a lot of perls.
1761 2018
1762Before the fork, IO::AIO enters a quiescent state where no requests 2019This module no longer tries to fight your OS, or POSIX. That means IO::AIO
1763can be added in other threads and no results will be processed. After 2020only works in the process that loaded it. Forking is fully supported, but
1764the fork the parent simply leaves the quiescent state and continues 2021using IO::AIO in the child is not.
1765request/result processing, while the child frees the request/result queue
1766(so that the requests started before the fork will only be handled in the
1767parent). Threads will be started on demand until the limit set in the
1768parent process has been reached again.
1769 2022
1770In short: the parent will, after a short pause, continue as if fork had 2023You might get around by not I<using> IO::AIO before (or after)
1771not been called, while the child will act as if IO::AIO has not been used 2024forking. You could also try to call the L<IO::AIO::reinit> function in the
1772yet. 2025child:
2026
2027=over 4
2028
2029=item IO::AIO::reinit
2030
2031Abandons all current requests and I/O threads and simply reinitialises all
2032data structures. This is not an operation supported by any standards, but
2033happens to work on GNU/Linux and some newer BSD systems.
2034
2035The only reasonable use for this function is to call it after forking, if
2036C<IO::AIO> was used in the parent. Calling it while IO::AIO is active in
2037the process will result in undefined behaviour. Calling it at any time
2038will also result in any undefined (by POSIX) behaviour.
2039
2040=back
1773 2041
1774=head2 MEMORY USAGE 2042=head2 MEMORY USAGE
1775 2043
1776Per-request usage: 2044Per-request usage:
1777 2045

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