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150 QUICK OVERVIEW 150 QUICK OVERVIEW
151 This section simply lists the prototypes of the most important functions 151 This section simply lists the prototypes of the most important functions
152 for quick reference. See the following sections for function-by-function 152 for quick reference. See the following sections for function-by-function
153 documentation. 153 documentation.
154 154
155 aio_wd $pathname, $callback->($wd)
155 aio_open $pathname, $flags, $mode, $callback->($fh) 156 aio_open $pathname, $flags, $mode, $callback->($fh)
156 aio_close $fh, $callback->($status) 157 aio_close $fh, $callback->($status)
157 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval) 158 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
158 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval) 159 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
159 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval) 160 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
… …
164 aio_utime $fh_or_path, $atime, $mtime, $callback->($status) 165 aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
165 aio_chown $fh_or_path, $uid, $gid, $callback->($status) 166 aio_chown $fh_or_path, $uid, $gid, $callback->($status)
166 aio_truncate $fh_or_path, $offset, $callback->($status) 167 aio_truncate $fh_or_path, $offset, $callback->($status)
167 aio_chmod $fh_or_path, $mode, $callback->($status) 168 aio_chmod $fh_or_path, $mode, $callback->($status)
168 aio_unlink $pathname, $callback->($status) 169 aio_unlink $pathname, $callback->($status)
169 aio_mknod $path, $mode, $dev, $callback->($status) 170 aio_mknod $pathname, $mode, $dev, $callback->($status)
170 aio_link $srcpath, $dstpath, $callback->($status) 171 aio_link $srcpath, $dstpath, $callback->($status)
171 aio_symlink $srcpath, $dstpath, $callback->($status) 172 aio_symlink $srcpath, $dstpath, $callback->($status)
172 aio_readlink $path, $callback->($link) 173 aio_readlink $pathname, $callback->($link)
174 aio_realpath $pathname, $callback->($link)
173 aio_rename $srcpath, $dstpath, $callback->($status) 175 aio_rename $srcpath, $dstpath, $callback->($status)
174 aio_mkdir $pathname, $mode, $callback->($status) 176 aio_mkdir $pathname, $mode, $callback->($status)
175 aio_rmdir $pathname, $callback->($status) 177 aio_rmdir $pathname, $callback->($status)
176 aio_readdir $pathname, $callback->($entries) 178 aio_readdir $pathname, $callback->($entries)
177 aio_readdirx $pathname, $flags, $callback->($entries, $flags) 179 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
178 IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST 180 IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
179 IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN 181 IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
182 aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
180 aio_load $path, $data, $callback->($status) 183 aio_load $pathname, $data, $callback->($status)
181 aio_copy $srcpath, $dstpath, $callback->($status) 184 aio_copy $srcpath, $dstpath, $callback->($status)
182 aio_move $srcpath, $dstpath, $callback->($status) 185 aio_move $srcpath, $dstpath, $callback->($status)
183 aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
184 aio_rmtree $path, $callback->($status) 186 aio_rmtree $pathname, $callback->($status)
185 aio_sync $callback->($status) 187 aio_sync $callback->($status)
188 aio_syncfs $fh, $callback->($status)
186 aio_fsync $fh, $callback->($status) 189 aio_fsync $fh, $callback->($status)
187 aio_fdatasync $fh, $callback->($status) 190 aio_fdatasync $fh, $callback->($status)
188 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status) 191 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
189 aio_pathsync $path, $callback->($status) 192 aio_pathsync $pathname, $callback->($status)
190 aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status) 193 aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
191 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status) 194 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
192 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status) 195 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
193 aio_mlockall $flags, $callback->($status) 196 aio_mlockall $flags, $callback->($status)
194 aio_group $callback->(...) 197 aio_group $callback->(...)
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221 224
222 AIO REQUEST FUNCTIONS 225 AIO REQUEST FUNCTIONS
223 All the "aio_*" calls are more or less thin wrappers around the syscall 226 All the "aio_*" calls are more or less thin wrappers around the syscall
224 with the same name (sans "aio_"). The arguments are similar or 227 with the same name (sans "aio_"). The arguments are similar or
225 identical, and they all accept an additional (and optional) $callback 228 identical, and they all accept an additional (and optional) $callback
226 argument which must be a code reference. This code reference will get 229 argument which must be a code reference. This code reference will be
227 called with the syscall return code (e.g. most syscalls return -1 on
228 error, unlike perl, which usually delivers "false") as its sole argument
229 after the given syscall has been executed asynchronously. 230 called after the syscall has been executed in an asynchronous fashion.
231 The results of the request will be passed as arguments to the callback
232 (and, if an error occured, in $!) - for most requests the syscall return
233 code (e.g. most syscalls return -1 on error, unlike perl, which usually
234 delivers "false").
235
236 Some requests (such as "aio_readdir") pass the actual results and
237 communicate failures by passing "undef".
230 238
231 All functions expecting a filehandle keep a copy of the filehandle 239 All functions expecting a filehandle keep a copy of the filehandle
232 internally until the request has finished. 240 internally until the request has finished.
233 241
234 All functions return request objects of type IO::AIO::REQ that allow 242 All functions return request objects of type IO::AIO::REQ that allow
235 further manipulation of those requests while they are in-flight. 243 further manipulation of those requests while they are in-flight.
236 244
237 The pathnames you pass to these routines *must* be absolute and encoded 245 The pathnames you pass to these routines *should* be absolute. The
238 as octets. The reason for the former is that at the time the request is 246 reason for this is that at the time the request is being executed, the
239 being executed, the current working directory could have changed. 247 current working directory could have changed. Alternatively, you can
240 Alternatively, you can make sure that you never change the current 248 make sure that you never change the current working directory anywhere
241 working directory anywhere in the program and then use relative paths. 249 in the program and then use relative paths. You can also take advantage
250 of IO::AIOs working directory abstraction, that lets you specify paths
251 relative to some previously-opened "working directory object" - see the
252 description of the "IO::AIO::WD" class later in this document.
242 253
243 To encode pathnames as octets, either make sure you either: a) always 254 To encode pathnames as octets, either make sure you either: a) always
244 pass in filenames you got from outside (command line, readdir etc.) 255 pass in filenames you got from outside (command line, readdir etc.)
245 without tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module 256 without tinkering, b) are in your native filesystem encoding, c) use the
246 and encode your pathnames to the locale (or other) encoding in effect in 257 Encode module and encode your pathnames to the locale (or other)
247 the user environment, d) use Glib::filename_from_unicode on unicode 258 encoding in effect in the user environment, d) use
248 filenames or e) use something else to ensure your scalar has the correct 259 Glib::filename_from_unicode on unicode filenames or e) use something
249 contents. 260 else to ensure your scalar has the correct contents.
250 261
251 This works, btw. independent of the internal UTF-8 bit, which IO::AIO 262 This works, btw. independent of the internal UTF-8 bit, which IO::AIO
252 handles correctly whether it is set or not. 263 handles correctly whether it is set or not.
253 264
254 $prev_pri = aioreq_pri [$pri] 265 $prev_pri = aioreq_pri [$pri]
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306 } else { 317 } else {
307 die "open failed: $!\n"; 318 die "open failed: $!\n";
308 } 319 }
309 }; 320 };
310 321
322 In addition to all the common open modes/flags ("O_RDONLY",
323 "O_WRONLY", "O_RDWR", "O_CREAT", "O_TRUNC", "O_EXCL" and
324 "O_APPEND"), the following POSIX and non-POSIX constants are
325 available (missing ones on your system are, as usual, 0):
326
327 "O_ASYNC", "O_DIRECT", "O_NOATIME", "O_CLOEXEC", "O_NOCTTY",
328 "O_NOFOLLOW", "O_NONBLOCK", "O_EXEC", "O_SEARCH", "O_DIRECTORY",
329 "O_DSYNC", "O_RSYNC", "O_SYNC" and "O_TTY_INIT".
330
311 aio_close $fh, $callback->($status) 331 aio_close $fh, $callback->($status)
312 Asynchronously close a file and call the callback with the result 332 Asynchronously close a file and call the callback with the result
313 code. 333 code.
314 334
315 Unfortunately, you can't do this to perl. Perl *insists* very 335 Unfortunately, you can't do this to perl. Perl *insists* very
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358 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval) 378 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
359 Tries to copy $length bytes from $in_fh to $out_fh. It starts 379 Tries to copy $length bytes from $in_fh to $out_fh. It starts
360 reading at byte offset $in_offset, and starts writing at the current 380 reading at byte offset $in_offset, and starts writing at the current
361 file offset of $out_fh. Because of that, it is not safe to issue 381 file offset of $out_fh. Because of that, it is not safe to issue
362 more than one "aio_sendfile" per $out_fh, as they will interfere 382 more than one "aio_sendfile" per $out_fh, as they will interfere
363 with each other. 383 with each other. The same $in_fh works fine though, as this function
384 does not move or use the file offset of $in_fh.
364 385
365 Please note that "aio_sendfile" can read more bytes from $in_fh than 386 Please note that "aio_sendfile" can read more bytes from $in_fh than
366 are written, and there is no way to find out how many bytes have 387 are written, and there is no way to find out how many more bytes
367 been read from "aio_sendfile" alone, as "aio_sendfile" only provides 388 have been read from "aio_sendfile" alone, as "aio_sendfile" only
368 the number of bytes written to $out_fh. Only if the result value 389 provides the number of bytes written to $out_fh. Only if the result
369 equals $length one can assume that $length bytes have been read. 390 value equals $length one can assume that $length bytes have been
391 read.
370 392
371 Unlike with other "aio_" functions, it makes a lot of sense to use 393 Unlike with other "aio_" functions, it makes a lot of sense to use
372 "aio_sendfile" on non-blocking sockets, as long as one end 394 "aio_sendfile" on non-blocking sockets, as long as one end
373 (typically the $in_fh) is a file - the file I/O will then be 395 (typically the $in_fh) is a file - the file I/O will then be
374 asynchronous, while the socket I/O will be non-blocking. Note, 396 asynchronous, while the socket I/O will be non-blocking. Note,
375 however, that you can run into a trap where "aio_sendfile" reads 397 however, that you can run into a trap where "aio_sendfile" reads
376 some data with readahead, then fails to write all data, and when the 398 some data with readahead, then fails to write all data, and when the
377 socket is ready the next time, the data in the cache is already 399 socket is ready the next time, the data in the cache is already
378 lost, forcing "aio_sendfile" to again hit the disk. Explicit 400 lost, forcing "aio_sendfile" to again hit the disk. Explicit
379 "aio_read" + "aio_write" let's you control resource usage much 401 "aio_read" + "aio_write" let's you better control resource usage.
380 better.
381 402
382 This call tries to make use of a native "sendfile" syscall to 403 This call tries to make use of a native "sendfile"-like syscall to
383 provide zero-copy operation. For this to work, $out_fh should refer 404 provide zero-copy operation. For this to work, $out_fh should refer
384 to a socket, and $in_fh should refer to an mmap'able file. 405 to a socket, and $in_fh should refer to an mmap'able file.
385 406
386 If a native sendfile cannot be found or it fails with "ENOSYS", 407 If a native sendfile cannot be found or it fails with "ENOSYS",
387 "ENOTSUP", "EOPNOTSUPP", "EAFNOSUPPORT", "EPROTOTYPE" or "ENOTSOCK", 408 "EINVAL", "ENOTSUP", "EOPNOTSUPP", "EAFNOSUPPORT", "EPROTOTYPE" or
388 it will be emulated, so you can call "aio_sendfile" on any type of 409 "ENOTSOCK", it will be emulated, so you can call "aio_sendfile" on
389 filehandle regardless of the limitations of the operating system. 410 any type of filehandle regardless of the limitations of the
411 operating system.
412
413 As native sendfile syscalls (as practically any non-POSIX interface
414 hacked together in a hurry to improve benchmark numbers) tend to be
415 rather buggy on many systems, this implementation tries to work
416 around some known bugs in Linux and FreeBSD kernels (probably
417 others, too), but that might fail, so you really really should check
418 the return value of "aio_sendfile" - fewre bytes than expected might
419 have been transferred.
390 420
391 aio_readahead $fh,$offset,$length, $callback->($retval) 421 aio_readahead $fh,$offset,$length, $callback->($retval)
392 "aio_readahead" populates the page cache with data from a file so 422 "aio_readahead" populates the page cache with data from a file so
393 that subsequent reads from that file will not block on disk I/O. The 423 that subsequent reads from that file will not block on disk I/O. The
394 $offset argument specifies the starting point from which data is to 424 $offset argument specifies the starting point from which data is to
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512 542
513 aio_unlink $pathname, $callback->($status) 543 aio_unlink $pathname, $callback->($status)
514 Asynchronously unlink (delete) a file and call the callback with the 544 Asynchronously unlink (delete) a file and call the callback with the
515 result code. 545 result code.
516 546
517 aio_mknod $path, $mode, $dev, $callback->($status) 547 aio_mknod $pathname, $mode, $dev, $callback->($status)
518 [EXPERIMENTAL] 548 [EXPERIMENTAL]
519 549
520 Asynchronously create a device node (or fifo). See mknod(2). 550 Asynchronously create a device node (or fifo). See mknod(2).
521 551
522 The only (POSIX-) portable way of calling this function is: 552 The only (POSIX-) portable way of calling this function is:
523 553
524 aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ... 554 aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
525 555
526 See "aio_stat" for info about some potentially helpful extra 556 See "aio_stat" for info about some potentially helpful extra
527 constants and functions. 557 constants and functions.
528 558
529 aio_link $srcpath, $dstpath, $callback->($status) 559 aio_link $srcpath, $dstpath, $callback->($status)
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533 aio_symlink $srcpath, $dstpath, $callback->($status) 563 aio_symlink $srcpath, $dstpath, $callback->($status)
534 Asynchronously create a new symbolic link to the existing object at 564 Asynchronously create a new symbolic link to the existing object at
535 $srcpath at the path $dstpath and call the callback with the result 565 $srcpath at the path $dstpath and call the callback with the result
536 code. 566 code.
537 567
538 aio_readlink $path, $callback->($link) 568 aio_readlink $pathname, $callback->($link)
539 Asynchronously read the symlink specified by $path and pass it to 569 Asynchronously read the symlink specified by $path and pass it to
540 the callback. If an error occurs, nothing or undef gets passed to 570 the callback. If an error occurs, nothing or undef gets passed to
541 the callback. 571 the callback.
572
573 aio_realpath $pathname, $callback->($path)
574 Asynchronously make the path absolute and resolve any symlinks in
575 $path. The resulting path only consists of directories (Same as
576 Cwd::realpath).
577
578 This request can be used to get the absolute path of the current
579 working directory by passing it a path of . (a single dot).
542 580
543 aio_rename $srcpath, $dstpath, $callback->($status) 581 aio_rename $srcpath, $dstpath, $callback->($status)
544 Asynchronously rename the object at $srcpath to $dstpath, just as 582 Asynchronously rename the object at $srcpath to $dstpath, just as
545 rename(2) and call the callback with the result code. 583 rename(2) and call the callback with the result code.
546 584
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560 598
561 The callback is passed a single argument which is either "undef" or 599 The callback is passed a single argument which is either "undef" or
562 an array-ref with the filenames. 600 an array-ref with the filenames.
563 601
564 aio_readdirx $pathname, $flags, $callback->($entries, $flags) 602 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
565 Quite similar to "aio_readdir", but the $flags argument allows to 603 Quite similar to "aio_readdir", but the $flags argument allows one
566 tune behaviour and output format. In case of an error, $entries will 604 to tune behaviour and output format. In case of an error, $entries
567 be "undef". 605 will be "undef".
568 606
569 The flags are a combination of the following constants, ORed 607 The flags are a combination of the following constants, ORed
570 together (the flags will also be passed to the callback, possibly 608 together (the flags will also be passed to the callback, possibly
571 modified): 609 modified):
572 610
573 IO::AIO::READDIR_DENTS 611 IO::AIO::READDIR_DENTS
574 When this flag is off, then the callback gets an arrayref with 612 When this flag is off, then the callback gets an arrayref
575 of names only (as with "aio_readdir"), otherwise it gets an 613 consisting of names only (as with "aio_readdir"), otherwise it
576 arrayref with "[$name, $type, $inode]" arrayrefs, each 614 gets an arrayref with "[$name, $type, $inode]" arrayrefs, each
577 describing a single directory entry in more detail. 615 describing a single directory entry in more detail.
578 616
579 $name is the name of the entry. 617 $name is the name of the entry.
580 618
581 $type is one of the "IO::AIO::DT_xxx" constants: 619 $type is one of the "IO::AIO::DT_xxx" constants:
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594 unspecified content on systems that do not deliver the inode 632 unspecified content on systems that do not deliver the inode
595 information. 633 information.
596 634
597 IO::AIO::READDIR_DIRS_FIRST 635 IO::AIO::READDIR_DIRS_FIRST
598 When this flag is set, then the names will be returned in an 636 When this flag is set, then the names will be returned in an
599 order where likely directories come first. This is useful when 637 order where likely directories come first, in optimal stat
600 you need to quickly find directories, or you want to find all 638 order. This is useful when you need to quickly find directories,
601 directories while avoiding to stat() each entry. 639 or you want to find all directories while avoiding to stat()
640 each entry.
602 641
603 If the system returns type information in readdir, then this is 642 If the system returns type information in readdir, then this is
604 used to find directories directly. Otherwise, likely directories 643 used to find directories directly. Otherwise, likely directories
605 are files beginning with ".", or otherwise files with no dots, 644 are names beginning with ".", or otherwise names with no dots,
606 of which files with short names are tried first. 645 of which names with short names are tried first.
607 646
608 IO::AIO::READDIR_STAT_ORDER 647 IO::AIO::READDIR_STAT_ORDER
609 When this flag is set, then the names will be returned in an 648 When this flag is set, then the names will be returned in an
610 order suitable for stat()'ing each one. That is, when you plan 649 order suitable for stat()'ing each one. That is, when you plan
611 to stat() all files in the given directory, then the returned 650 to stat() all files in the given directory, then the returned
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616 optimal stat order. 655 optimal stat order.
617 656
618 IO::AIO::READDIR_FOUND_UNKNOWN 657 IO::AIO::READDIR_FOUND_UNKNOWN
619 This flag should not be set when calling "aio_readdirx". 658 This flag should not be set when calling "aio_readdirx".
620 Instead, it is being set by "aio_readdirx", when any of the 659 Instead, it is being set by "aio_readdirx", when any of the
621 $type's found were "IO::AIO::DT_UNKNOWN". The absense of this 660 $type's found were "IO::AIO::DT_UNKNOWN". The absence of this
622 flag therefore indicates that all $type's are known, which can 661 flag therefore indicates that all $type's are known, which can
623 be used to speed up some algorithms. 662 be used to speed up some algorithms.
624 663
625 aio_load $path, $data, $callback->($status) 664 aio_load $pathname, $data, $callback->($status)
626 This is a composite request that tries to fully load the given file 665 This is a composite request that tries to fully load the given file
627 into memory. Status is the same as with aio_read. 666 into memory. Status is the same as with aio_read.
628 667
629 aio_copy $srcpath, $dstpath, $callback->($status) 668 aio_copy $srcpath, $dstpath, $callback->($status)
630 Try to copy the *file* (directories not supported as either source 669 Try to copy the *file* (directories not supported as either source
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647 686
648 This is a composite request that tries to rename(2) the file first; 687 This is a composite request that tries to rename(2) the file first;
649 if rename fails with "EXDEV", it copies the file with "aio_copy" 688 if rename fails with "EXDEV", it copies the file with "aio_copy"
650 and, if that is successful, unlinks the $srcpath. 689 and, if that is successful, unlinks the $srcpath.
651 690
652 aio_scandir $path, $maxreq, $callback->($dirs, $nondirs) 691 aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
653 Scans a directory (similar to "aio_readdir") but additionally tries 692 Scans a directory (similar to "aio_readdir") but additionally tries
654 to efficiently separate the entries of directory $path into two sets 693 to efficiently separate the entries of directory $path into two sets
655 of names, directories you can recurse into (directories), and ones 694 of names, directories you can recurse into (directories), and ones
656 you cannot recurse into (everything else, including symlinks to 695 you cannot recurse into (everything else, including symlinks to
657 directories). 696 directories).
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690 Then entries will be sorted into likely directories a non-initial 729 Then entries will be sorted into likely directories a non-initial
691 dot currently) and likely non-directories (see "aio_readdirx"). Then 730 dot currently) and likely non-directories (see "aio_readdirx"). Then
692 every entry plus an appended "/." will be "stat"'ed, likely 731 every entry plus an appended "/." will be "stat"'ed, likely
693 directories first, in order of their inode numbers. If that 732 directories first, in order of their inode numbers. If that
694 succeeds, it assumes that the entry is a directory or a symlink to 733 succeeds, it assumes that the entry is a directory or a symlink to
695 directory (which will be checked seperately). This is often faster 734 directory (which will be checked separately). This is often faster
696 than stat'ing the entry itself because filesystems might detect the 735 than stat'ing the entry itself because filesystems might detect the
697 type of the entry without reading the inode data (e.g. ext2fs 736 type of the entry without reading the inode data (e.g. ext2fs
698 filetype feature), even on systems that cannot return the filetype 737 filetype feature), even on systems that cannot return the filetype
699 information on readdir. 738 information on readdir.
700 739
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706 745
707 It will also likely work on non-POSIX filesystems with reduced 746 It will also likely work on non-POSIX filesystems with reduced
708 efficiency as those tend to return 0 or 1 as link counts, which 747 efficiency as those tend to return 0 or 1 as link counts, which
709 disables the directory counting heuristic. 748 disables the directory counting heuristic.
710 749
711 aio_rmtree $path, $callback->($status) 750 aio_rmtree $pathname, $callback->($status)
712 Delete a directory tree starting (and including) $path, return the 751 Delete a directory tree starting (and including) $path, return the
713 status of the final "rmdir" only. This is a composite request that 752 status of the final "rmdir" only. This is a composite request that
714 uses "aio_scandir" to recurse into and rmdir directories, and unlink 753 uses "aio_scandir" to recurse into and rmdir directories, and unlink
715 everything else. 754 everything else.
716 755
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725 Asynchronously call fdatasync on the given filehandle and call the 764 Asynchronously call fdatasync on the given filehandle and call the
726 callback with the fdatasync result code. 765 callback with the fdatasync result code.
727 766
728 If this call isn't available because your OS lacks it or it couldn't 767 If this call isn't available because your OS lacks it or it couldn't
729 be detected, it will be emulated by calling "fsync" instead. 768 be detected, it will be emulated by calling "fsync" instead.
769
770 aio_syncfs $fh, $callback->($status)
771 Asynchronously call the syncfs syscall to sync the filesystem
772 associated to the given filehandle and call the callback with the
773 syncfs result code. If syncfs is not available, calls sync(), but
774 returns -1 and sets errno to "ENOSYS" nevertheless.
730 775
731 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status) 776 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
732 Sync the data portion of the file specified by $offset and $length 777 Sync the data portion of the file specified by $offset and $length
733 to disk (but NOT the metadata), by calling the Linux-specific 778 to disk (but NOT the metadata), by calling the Linux-specific
734 sync_file_range call. If sync_file_range is not available or it 779 sync_file_range call. If sync_file_range is not available or it
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738 "IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE", 783 "IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE",
739 "IO::AIO::SYNC_FILE_RANGE_WRITE" and 784 "IO::AIO::SYNC_FILE_RANGE_WRITE" and
740 "IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER": refer to the sync_file_range 785 "IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER": refer to the sync_file_range
741 manpage for details. 786 manpage for details.
742 787
743 aio_pathsync $path, $callback->($status) 788 aio_pathsync $pathname, $callback->($status)
744 This request tries to open, fsync and close the given path. This is 789 This request tries to open, fsync and close the given path. This is
745 a composite request intended to sync directories after directory 790 a composite request intended to sync directories after directory
746 operations (E.g. rename). This might not work on all operating 791 operations (E.g. rename). This might not work on all operating
747 systems or have any specific effect, but usually it makes sure that 792 systems or have any specific effect, but usually it makes sure that
748 directory changes get written to disc. It works for anything that 793 directory changes get written to disc. It works for anything that
… …
861 requests like sleep and file handle readable/writable, the overhead 906 requests like sleep and file handle readable/writable, the overhead
862 this creates is immense (it blocks a thread for a long time) so do 907 this creates is immense (it blocks a thread for a long time) so do
863 not use this function except to put your application under 908 not use this function except to put your application under
864 artificial I/O pressure. 909 artificial I/O pressure.
865 910
911 IO::AIO::WD - multiple working directories
912 Your process only has one current working directory, which is used by
913 all threads. This makes it hard to use relative paths (some other
914 component could call "chdir" at any time, and it is hard to control when
915 the path will be used by IO::AIO).
916
917 One solution for this is to always use absolute paths. This usually
918 works, but can be quite slow (the kernel has to walk the whole path on
919 every access), and can also be a hassle to implement.
920
921 Newer POSIX systems have a number of functions (openat, fdopendir,
922 futimensat and so on) that make it possible to specify working
923 directories per operation.
924
925 For portability, and because the clowns who "designed", or shall I
926 write, perpetrated this new interface were obviously half-drunk, this
927 abstraction cannot be perfect, though.
928
929 IO::AIO allows you to convert directory paths into a so-called
930 IO::AIO::WD object. This object stores the canonicalised, absolute
931 version of the path, and on systems that allow it, also a directory file
932 descriptor.
933
934 Everywhere where a pathname is accepted by IO::AIO (e.g. in "aio_stat"
935 or "aio_unlink"), one can specify an array reference with an IO::AIO::WD
936 object and a pathname instead (or the IO::AIO::WD object alone, which
937 gets interpreted as "[$wd, "."]"). If the pathname is absolute, the
938 IO::AIO::WD object is ignored, otherwise the pathname is resolved
939 relative to that IO::AIO::WD object.
940
941 For example, to get a wd object for /etc and then stat passwd inside,
942 you would write:
943
944 aio_wd "/etc", sub {
945 my $etcdir = shift;
946
947 # although $etcdir can be undef on error, there is generally no reason
948 # to check for errors here, as aio_stat will fail with ENOENT
949 # when $etcdir is undef.
950
951 aio_stat [$etcdir, "passwd"], sub {
952 # yay
953 };
954 };
955
956 That "aio_wd" is a request and not a normal function shows that creating
957 an IO::AIO::WD object is itself a potentially blocking operation, which
958 is why it is done asynchronously.
959
960 To stat the directory obtained with "aio_wd" above, one could write
961 either of the following three request calls:
962
963 aio_lstat "/etc" , sub { ... # pathname as normal string
964 aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
965 aio_lstat $wd , sub { ... # shorthand for the previous
966
967 As with normal pathnames, IO::AIO keeps a copy of the working directory
968 object and the pathname string, so you could write the following without
969 causing any issues due to $path getting reused:
970
971 my $path = [$wd, undef];
972
973 for my $name (qw(abc def ghi)) {
974 $path->[1] = $name;
975 aio_stat $path, sub {
976 # ...
977 };
978 }
979
980 There are some caveats: when directories get renamed (or deleted), the
981 pathname string doesn't change, so will point to the new directory (or
982 nowhere at all), while the directory fd, if available on the system,
983 will still point to the original directory. Most functions accepting a
984 pathname will use the directory fd on newer systems, and the string on
985 older systems. Some functions (such as realpath) will always rely on the
986 string form of the pathname.
987
988 So this fucntionality is mainly useful to get some protection against
989 "chdir", to easily get an absolute path out of a relative path for
990 future reference, and to speed up doing many operations in the same
991 directory (e.g. when stat'ing all files in a directory).
992
993 The following functions implement this working directory abstraction:
994
995 aio_wd $pathname, $callback->($wd)
996 Asynchonously canonicalise the given pathname and convert it to an
997 IO::AIO::WD object representing it. If possible and supported on the
998 system, also open a directory fd to speed up pathname resolution
999 relative to this working directory.
1000
1001 If something goes wrong, then "undef" is passwd to the callback
1002 instead of a working directory object and $! is set appropriately.
1003 Since passing "undef" as working directory component of a pathname
1004 fails the request with "ENOENT", there is often no need for error
1005 checking in the "aio_wd" callback, as future requests using the
1006 value will fail in the expected way.
1007
1008 If this call isn't available because your OS lacks it or it couldn't
1009 be detected, it will be emulated by calling "fsync" instead.
1010
1011 IO::AIO::CWD
1012 This is a compiletime constant (object) that represents the process
1013 current working directory.
1014
1015 Specifying this object as working directory object for a pathname is
1016 as if the pathname would be specified directly, without a directory
1017 object, e.g., these calls are functionally identical:
1018
1019 aio_stat "somefile", sub { ... };
1020 aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
1021
866 IO::AIO::REQ CLASS 1022 IO::AIO::REQ CLASS
867 All non-aggregate "aio_*" functions return an object of this class when 1023 All non-aggregate "aio_*" functions return an object of this class when
868 called in non-void context. 1024 called in non-void context.
869 1025
870 cancel $req 1026 cancel $req
… …
969 Sets a feeder/generator on this group: every group can have an 1125 Sets a feeder/generator on this group: every group can have an
970 attached generator that generates requests if idle. The idea behind 1126 attached generator that generates requests if idle. The idea behind
971 this is that, although you could just queue as many requests as you 1127 this is that, although you could just queue as many requests as you
972 want in a group, this might starve other requests for a potentially 1128 want in a group, this might starve other requests for a potentially
973 long time. For example, "aio_scandir" might generate hundreds of 1129 long time. For example, "aio_scandir" might generate hundreds of
974 thousands "aio_stat" requests, delaying any later requests for a 1130 thousands of "aio_stat" requests, delaying any later requests for a
975 long time. 1131 long time.
976 1132
977 To avoid this, and allow incremental generation of requests, you can 1133 To avoid this, and allow incremental generation of requests, you can
978 instead a group and set a feeder on it that generates those 1134 instead a group and set a feeder on it that generates those
979 requests. The feed callback will be called whenever there are few 1135 requests. The feed callback will be called whenever there are few
… …
1022 1178
1023 See "poll_cb" for an example. 1179 See "poll_cb" for an example.
1024 1180
1025 IO::AIO::poll_cb 1181 IO::AIO::poll_cb
1026 Process some outstanding events on the result pipe. You have to call 1182 Process some outstanding events on the result pipe. You have to call
1027 this regularly. Returns 0 if all events could be processed, or -1 if 1183 this regularly. Returns 0 if all events could be processed (or there
1028 it returned earlier for whatever reason. Returns immediately when no 1184 were no events to process), or -1 if it returned earlier for
1029 events are outstanding. The amount of events processed depends on 1185 whatever reason. Returns immediately when no events are outstanding.
1030 the settings of "IO::AIO::max_poll_req" and 1186 The amount of events processed depends on the settings of
1031 "IO::AIO::max_poll_time". 1187 "IO::AIO::max_poll_req" and "IO::AIO::max_poll_time".
1032 1188
1033 If not all requests were processed for whatever reason, the 1189 If not all requests were processed for whatever reason, the
1034 filehandle will still be ready when "poll_cb" returns, so normally 1190 filehandle will still be ready when "poll_cb" returns, so normally
1035 you don't have to do anything special to have it called later. 1191 you don't have to do anything special to have it called later.
1192
1193 Apart from calling "IO::AIO::poll_cb" when the event filehandle
1194 becomes ready, it can be beneficial to call this function from loops
1195 which submit a lot of requests, to make sure the results get
1196 processed when they become available and not just when the loop is
1197 finished and the event loop takes over again. This function returns
1198 very fast when there are no outstanding requests.
1036 1199
1037 Example: Install an Event watcher that automatically calls 1200 Example: Install an Event watcher that automatically calls
1038 IO::AIO::poll_cb with high priority (more examples can be found in 1201 IO::AIO::poll_cb with high priority (more examples can be found in
1039 the SYNOPSIS section, at the top of this document): 1202 the SYNOPSIS section, at the top of this document):
1040 1203
… …
1153 IO::AIO::idle_timeout $seconds 1316 IO::AIO::idle_timeout $seconds
1154 Sets the minimum idle timeout (default 10) after which worker 1317 Sets the minimum idle timeout (default 10) after which worker
1155 threads are allowed to exit. SEe "IO::AIO::max_idle". 1318 threads are allowed to exit. SEe "IO::AIO::max_idle".
1156 1319
1157 IO::AIO::max_outstanding $maxreqs 1320 IO::AIO::max_outstanding $maxreqs
1321 Sets the maximum number of outstanding requests to $nreqs. If you do
1322 queue up more than this number of requests, the next call to
1323 "IO::AIO::poll_cb" (and other functions calling "poll_cb", such as
1324 "IO::AIO::flush" or "IO::AIO::poll") will block until the limit is
1325 no longer exceeded.
1326
1327 In other words, this setting does not enforce a queue limit, but can
1328 be used to make poll functions block if the limit is exceeded.
1329
1158 This is a very bad function to use in interactive programs because 1330 This is a very bad function to use in interactive programs because
1159 it blocks, and a bad way to reduce concurrency because it is 1331 it blocks, and a bad way to reduce concurrency because it is
1160 inexact: Better use an "aio_group" together with a feed callback. 1332 inexact: Better use an "aio_group" together with a feed callback.
1161 1333
1162 Sets the maximum number of outstanding requests to $nreqs. If you do 1334 It's main use is in scripts without an event loop - when you want to
1163 queue up more than this number of requests, the next call to the 1335 stat a lot of files, you can write somehting like this:
1164 "poll_cb" (and "poll_some" and other functions calling "poll_cb")
1165 function will block until the limit is no longer exceeded.
1166 1336
1167 The default value is very large, so there is no practical limit on 1337 IO::AIO::max_outstanding 32;
1338
1339 for my $path (...) {
1340 aio_stat $path , ...;
1341 IO::AIO::poll_cb;
1342 }
1343
1344 IO::AIO::flush;
1345
1346 The call to "poll_cb" inside the loop will normally return
1347 instantly, but as soon as more thna 32 reqeusts are in-flight, it
1348 will block until some requests have been handled. This keeps the
1349 loop from pushing a large number of "aio_stat" requests onto the
1350 queue.
1351
1352 The default value for "max_outstanding" is very large, so there is
1168 the number of outstanding requests. 1353 no practical limit on the number of outstanding requests.
1169
1170 You can still queue as many requests as you want. Therefore,
1171 "max_outstanding" is mainly useful in simple scripts (with low
1172 values) or as a stop gap to shield against fatal memory overflow
1173 (with large values).
1174 1354
1175 STATISTICAL INFORMATION 1355 STATISTICAL INFORMATION
1176 IO::AIO::nreqs 1356 IO::AIO::nreqs
1177 Returns the number of requests currently in the ready, execute or 1357 Returns the number of requests currently in the ready, execute or
1178 pending states (i.e. for which their callback has not been invoked 1358 pending states (i.e. for which their callback has not been invoked
… …
1203 1383
1204 Returns the number of bytes copied, or -1 on error. 1384 Returns the number of bytes copied, or -1 on error.
1205 1385
1206 IO::AIO::fadvise $fh, $offset, $len, $advice 1386 IO::AIO::fadvise $fh, $offset, $len, $advice
1207 Simply calls the "posix_fadvise" function (see its manpage for 1387 Simply calls the "posix_fadvise" function (see its manpage for
1208 details). The following advice constants are avaiable: 1388 details). The following advice constants are available:
1209 "IO::AIO::FADV_NORMAL", "IO::AIO::FADV_SEQUENTIAL", 1389 "IO::AIO::FADV_NORMAL", "IO::AIO::FADV_SEQUENTIAL",
1210 "IO::AIO::FADV_RANDOM", "IO::AIO::FADV_NOREUSE", 1390 "IO::AIO::FADV_RANDOM", "IO::AIO::FADV_NOREUSE",
1211 "IO::AIO::FADV_WILLNEED", "IO::AIO::FADV_DONTNEED". 1391 "IO::AIO::FADV_WILLNEED", "IO::AIO::FADV_DONTNEED".
1212 1392
1213 On systems that do not implement "posix_fadvise", this function 1393 On systems that do not implement "posix_fadvise", this function
1214 returns ENOSYS, otherwise the return value of "posix_fadvise". 1394 returns ENOSYS, otherwise the return value of "posix_fadvise".
1215 1395
1216 IO::AIO::madvise $scalar, $offset, $len, $advice 1396 IO::AIO::madvise $scalar, $offset, $len, $advice
1217 Simply calls the "posix_madvise" function (see its manpage for 1397 Simply calls the "posix_madvise" function (see its manpage for
1218 details). The following advice constants are avaiable: 1398 details). The following advice constants are available:
1219 "IO::AIO::MADV_NORMAL", "IO::AIO::MADV_SEQUENTIAL", 1399 "IO::AIO::MADV_NORMAL", "IO::AIO::MADV_SEQUENTIAL",
1220 "IO::AIO::MADV_RANDOM", "IO::AIO::MADV_WILLNEED", 1400 "IO::AIO::MADV_RANDOM", "IO::AIO::MADV_WILLNEED",
1221 "IO::AIO::MADV_DONTNEED". 1401 "IO::AIO::MADV_DONTNEED".
1222 1402
1223 On systems that do not implement "posix_madvise", this function 1403 On systems that do not implement "posix_madvise", this function
1224 returns ENOSYS, otherwise the return value of "posix_madvise". 1404 returns ENOSYS, otherwise the return value of "posix_madvise".
1225 1405
1226 IO::AIO::mprotect $scalar, $offset, $len, $protect 1406 IO::AIO::mprotect $scalar, $offset, $len, $protect
1227 Simply calls the "mprotect" function on the preferably AIO::mmap'ed 1407 Simply calls the "mprotect" function on the preferably AIO::mmap'ed
1228 $scalar (see its manpage for details). The following protect 1408 $scalar (see its manpage for details). The following protect
1229 constants are avaiable: "IO::AIO::PROT_NONE", "IO::AIO::PROT_READ", 1409 constants are available: "IO::AIO::PROT_NONE", "IO::AIO::PROT_READ",
1230 "IO::AIO::PROT_WRITE", "IO::AIO::PROT_EXEC". 1410 "IO::AIO::PROT_WRITE", "IO::AIO::PROT_EXEC".
1231 1411
1232 On systems that do not implement "mprotect", this function returns 1412 On systems that do not implement "mprotect", this function returns
1233 ENOSYS, otherwise the return value of "mprotect". 1413 ENOSYS, otherwise the return value of "mprotect".
1234 1414
… …
1324 # Danga::Socket integration 1504 # Danga::Socket integration
1325 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno => 1505 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
1326 \&IO::AIO::poll_cb); 1506 \&IO::AIO::poll_cb);
1327 1507
1328 FORK BEHAVIOUR 1508 FORK BEHAVIOUR
1329 This module should do "the right thing" when the process using it forks: 1509 Usage of pthreads in a program changes the semantics of fork
1510 considerably. Specifically, only async-safe functions can be called
1511 after fork. Perl doesn't know about this, so in general, you cannot call
1512 fork with defined behaviour in perl if pthreads are involved. IO::AIO
1513 uses pthreads, so this applies, but many other extensions and (for
1514 inexplicable reasons) perl itself often is linked against pthreads, so
1515 this limitation applies to quite a lot of perls.
1330 1516
1331 Before the fork, IO::AIO enters a quiescent state where no requests can 1517 This module no longer tries to fight your OS, or POSIX. That means
1332 be added in other threads and no results will be processed. After the 1518 IO::AIO only works in the process that loaded it. Forking is fully
1333 fork the parent simply leaves the quiescent state and continues 1519 supported, but using IO::AIO in the child is not.
1334 request/result processing, while the child frees the request/result
1335 queue (so that the requests started before the fork will only be handled
1336 in the parent). Threads will be started on demand until the limit set in
1337 the parent process has been reached again.
1338 1520
1339 In short: the parent will, after a short pause, continue as if fork had 1521 You might get around by not *using* IO::AIO before (or after) forking.
1340 not been called, while the child will act as if IO::AIO has not been 1522 You could also try to call the IO::AIO::reinit function in the child:
1341 used yet. 1523
1524 IO::AIO::reinit
1525 Abandons all current requests and I/O threads and simply
1526 reinitialises all data structures. This is not an operation
1527 supported by any standards, but happens to work on GNU/Linux and
1528 some newer BSD systems.
1529
1530 The only reasonable use for this function is to call it after
1531 forking, if "IO::AIO" was used in the parent. Calling it while
1532 IO::AIO is active in the process will result in undefined behaviour.
1533 Calling it at any time will also result in any undefined (by POSIX)
1534 behaviour.
1342 1535
1343 MEMORY USAGE 1536 MEMORY USAGE
1344 Per-request usage: 1537 Per-request usage:
1345 1538
1346 Each aio request uses - depending on your architecture - around 100-200 1539 Each aio request uses - depending on your architecture - around 100-200

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