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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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204 IO::AIO::max_poll_reqs $nreqs 207 IO::AIO::max_poll_reqs $nreqs
205 IO::AIO::max_poll_time $seconds 208 IO::AIO::max_poll_time $seconds
206 IO::AIO::min_parallel $nthreads 209 IO::AIO::min_parallel $nthreads
207 IO::AIO::max_parallel $nthreads 210 IO::AIO::max_parallel $nthreads
208 IO::AIO::max_idle $nthreads 211 IO::AIO::max_idle $nthreads
212 IO::AIO::idle_timeout $seconds
209 IO::AIO::max_outstanding $maxreqs 213 IO::AIO::max_outstanding $maxreqs
210 IO::AIO::nreqs 214 IO::AIO::nreqs
211 IO::AIO::nready 215 IO::AIO::nready
212 IO::AIO::npending 216 IO::AIO::npending
213 217
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220 224
221 AIO REQUEST FUNCTIONS 225 AIO REQUEST FUNCTIONS
222 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
223 with the same name (sans "aio_"). The arguments are similar or 227 with the same name (sans "aio_"). The arguments are similar or
224 identical, and they all accept an additional (and optional) $callback 228 identical, and they all accept an additional (and optional) $callback
225 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
226 called with the syscall return code (e.g. most syscalls return -1 on
227 error, unlike perl, which usually delivers "false") as its sole argument
228 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".
229 238
230 All functions expecting a filehandle keep a copy of the filehandle 239 All functions expecting a filehandle keep a copy of the filehandle
231 internally until the request has finished. 240 internally until the request has finished.
232 241
233 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
234 further manipulation of those requests while they are in-flight. 243 further manipulation of those requests while they are in-flight.
235 244
236 The pathnames you pass to these routines *must* be absolute and encoded 245 The pathnames you pass to these routines *should* be absolute. The
237 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
238 being executed, the current working directory could have changed. 247 current working directory could have changed. Alternatively, you can
239 Alternatively, you can make sure that you never change the current 248 make sure that you never change the current working directory anywhere
240 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.
241 253
242 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
243 pass in filenames you got from outside (command line, readdir etc.) 255 pass in filenames you got from outside (command line, readdir etc.)
244 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
245 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)
246 the user environment, d) use Glib::filename_from_unicode on unicode 258 encoding in effect in the user environment, d) use
247 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
248 contents. 260 else to ensure your scalar has the correct contents.
249 261
250 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
251 handles correctly whether it is set or not. 263 handles correctly whether it is set or not.
252 264
253 $prev_pri = aioreq_pri [$pri] 265 $prev_pri = aioreq_pri [$pri]
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305 } else { 317 } else {
306 die "open failed: $!\n"; 318 die "open failed: $!\n";
307 } 319 }
308 }; 320 };
309 321
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
310 aio_close $fh, $callback->($status) 331 aio_close $fh, $callback->($status)
311 Asynchronously close a file and call the callback with the result 332 Asynchronously close a file and call the callback with the result
312 code. 333 code.
313 334
314 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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357 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval) 378 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
358 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
359 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
360 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
361 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
362 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.
363 385
386 Please note that "aio_sendfile" can read more bytes from $in_fh than
387 are written, and there is no way to find out how many more bytes
388 have been read from "aio_sendfile" alone, as "aio_sendfile" only
389 provides the number of bytes written to $out_fh. Only if the result
390 value equals $length one can assume that $length bytes have been
391 read.
392
393 Unlike with other "aio_" functions, it makes a lot of sense to use
394 "aio_sendfile" on non-blocking sockets, as long as one end
395 (typically the $in_fh) is a file - the file I/O will then be
396 asynchronous, while the socket I/O will be non-blocking. Note,
397 however, that you can run into a trap where "aio_sendfile" reads
398 some data with readahead, then fails to write all data, and when the
399 socket is ready the next time, the data in the cache is already
400 lost, forcing "aio_sendfile" to again hit the disk. Explicit
401 "aio_read" + "aio_write" let's you better control resource usage.
402
364 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
365 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
366 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.
367 406
368 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",
369 "ENOTSUP", "EOPNOTSUPP", "EAFNOSUPPORT", "EPROTOTYPE" or "ENOTSOCK", 408 "EINVAL", "ENOTSUP", "EOPNOTSUPP", "EAFNOSUPPORT", "EPROTOTYPE" or
370 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
371 filehandle regardless of the limitations of the operating system. 410 any type of filehandle regardless of the limitations of the
411 operating system.
372 412
373 Please note, however, that "aio_sendfile" can read more bytes from 413 As native sendfile syscalls (as practically any non-POSIX interface
374 $in_fh than are written, and there is no way to find out how many 414 hacked together in a hurry to improve benchmark numbers) tend to be
375 bytes have been read from "aio_sendfile" alone, as "aio_sendfile" 415 rather buggy on many systems, this implementation tries to work
376 only provides the number of bytes written to $out_fh. Only if the 416 around some known bugs in Linux and FreeBSD kernels (probably
377 result value equals $length one can assume that $length bytes have 417 others, too), but that might fail, so you really really should check
378 been read. 418 the return value of "aio_sendfile" - fewre bytes than expected might
419 have been transferred.
379 420
380 aio_readahead $fh,$offset,$length, $callback->($retval) 421 aio_readahead $fh,$offset,$length, $callback->($retval)
381 "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
382 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
383 $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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403 444
404 Currently, the stats are always 64-bit-stats, i.e. instead of 445 Currently, the stats are always 64-bit-stats, i.e. instead of
405 returning an error when stat'ing a large file, the results will be 446 returning an error when stat'ing a large file, the results will be
406 silently truncated unless perl itself is compiled with large file 447 silently truncated unless perl itself is compiled with large file
407 support. 448 support.
449
450 To help interpret the mode and dev/rdev stat values, IO::AIO offers
451 the following constants and functions (if not implemented, the
452 constants will be 0 and the functions will either "croak" or fall
453 back on traditional behaviour).
454
455 "S_IFMT", "S_IFIFO", "S_IFCHR", "S_IFBLK", "S_IFLNK", "S_IFREG",
456 "S_IFDIR", "S_IFWHT", "S_IFSOCK", "IO::AIO::major $dev_t",
457 "IO::AIO::minor $dev_t", "IO::AIO::makedev $major, $minor".
408 458
409 Example: Print the length of /etc/passwd: 459 Example: Print the length of /etc/passwd:
410 460
411 aio_stat "/etc/passwd", sub { 461 aio_stat "/etc/passwd", sub {
412 $_[0] and die "stat failed: $!"; 462 $_[0] and die "stat failed: $!";
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492 542
493 aio_unlink $pathname, $callback->($status) 543 aio_unlink $pathname, $callback->($status)
494 Asynchronously unlink (delete) a file and call the callback with the 544 Asynchronously unlink (delete) a file and call the callback with the
495 result code. 545 result code.
496 546
497 aio_mknod $path, $mode, $dev, $callback->($status) 547 aio_mknod $pathname, $mode, $dev, $callback->($status)
498 [EXPERIMENTAL] 548 [EXPERIMENTAL]
499 549
500 Asynchronously create a device node (or fifo). See mknod(2). 550 Asynchronously create a device node (or fifo). See mknod(2).
501 551
502 The only (POSIX-) portable way of calling this function is: 552 The only (POSIX-) portable way of calling this function is:
503 553
504 aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ... 554 aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
555
556 See "aio_stat" for info about some potentially helpful extra
557 constants and functions.
505 558
506 aio_link $srcpath, $dstpath, $callback->($status) 559 aio_link $srcpath, $dstpath, $callback->($status)
507 Asynchronously create a new link to the existing object at $srcpath 560 Asynchronously create a new link to the existing object at $srcpath
508 at the path $dstpath and call the callback with the result code. 561 at the path $dstpath and call the callback with the result code.
509 562
510 aio_symlink $srcpath, $dstpath, $callback->($status) 563 aio_symlink $srcpath, $dstpath, $callback->($status)
511 Asynchronously create a new symbolic link to the existing object at 564 Asynchronously create a new symbolic link to the existing object at
512 $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
513 code. 566 code.
514 567
515 aio_readlink $path, $callback->($link) 568 aio_readlink $pathname, $callback->($link)
516 Asynchronously read the symlink specified by $path and pass it to 569 Asynchronously read the symlink specified by $path and pass it to
517 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
518 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).
519 580
520 aio_rename $srcpath, $dstpath, $callback->($status) 581 aio_rename $srcpath, $dstpath, $callback->($status)
521 Asynchronously rename the object at $srcpath to $dstpath, just as 582 Asynchronously rename the object at $srcpath to $dstpath, just as
522 rename(2) and call the callback with the result code. 583 rename(2) and call the callback with the result code.
523 584
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537 598
538 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
539 an array-ref with the filenames. 600 an array-ref with the filenames.
540 601
541 aio_readdirx $pathname, $flags, $callback->($entries, $flags) 602 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
542 Quite similar to "aio_readdir", but the $flags argument allows to 603 Quite similar to "aio_readdir", but the $flags argument allows one
543 tune behaviour and output format. In case of an error, $entries will 604 to tune behaviour and output format. In case of an error, $entries
544 be "undef". 605 will be "undef".
545 606
546 The flags are a combination of the following constants, ORed 607 The flags are a combination of the following constants, ORed
547 together (the flags will also be passed to the callback, possibly 608 together (the flags will also be passed to the callback, possibly
548 modified): 609 modified):
549 610
550 IO::AIO::READDIR_DENTS 611 IO::AIO::READDIR_DENTS
551 When this flag is off, then the callback gets an arrayref with 612 When this flag is off, then the callback gets an arrayref
552 of names only (as with "aio_readdir"), otherwise it gets an 613 consisting of names only (as with "aio_readdir"), otherwise it
553 arrayref with "[$name, $type, $inode]" arrayrefs, each 614 gets an arrayref with "[$name, $type, $inode]" arrayrefs, each
554 describing a single directory entry in more detail. 615 describing a single directory entry in more detail.
555 616
556 $name is the name of the entry. 617 $name is the name of the entry.
557 618
558 $type is one of the "IO::AIO::DT_xxx" constants: 619 $type is one of the "IO::AIO::DT_xxx" constants:
… …
571 unspecified content on systems that do not deliver the inode 632 unspecified content on systems that do not deliver the inode
572 information. 633 information.
573 634
574 IO::AIO::READDIR_DIRS_FIRST 635 IO::AIO::READDIR_DIRS_FIRST
575 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
576 order where likely directories come first. This is useful when 637 order where likely directories come first, in optimal stat
577 you need to quickly find directories, or you want to find all 638 order. This is useful when you need to quickly find directories,
578 directories while avoiding to stat() each entry. 639 or you want to find all directories while avoiding to stat()
640 each entry.
579 641
580 If the system returns type information in readdir, then this is 642 If the system returns type information in readdir, then this is
581 used to find directories directly. Otherwise, likely directories 643 used to find directories directly. Otherwise, likely directories
582 are files beginning with ".", or otherwise files with no dots, 644 are names beginning with ".", or otherwise names with no dots,
583 of which files with short names are tried first. 645 of which names with short names are tried first.
584 646
585 IO::AIO::READDIR_STAT_ORDER 647 IO::AIO::READDIR_STAT_ORDER
586 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
587 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
588 to stat() all files in the given directory, then the returned 650 to stat() all files in the given directory, then the returned
… …
593 optimal stat order. 655 optimal stat order.
594 656
595 IO::AIO::READDIR_FOUND_UNKNOWN 657 IO::AIO::READDIR_FOUND_UNKNOWN
596 This flag should not be set when calling "aio_readdirx". 658 This flag should not be set when calling "aio_readdirx".
597 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
598 $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
599 flag therefore indicates that all $type's are known, which can 661 flag therefore indicates that all $type's are known, which can
600 be used to speed up some algorithms. 662 be used to speed up some algorithms.
601 663
602 aio_load $path, $data, $callback->($status) 664 aio_load $pathname, $data, $callback->($status)
603 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
604 into memory. Status is the same as with aio_read. 666 into memory. Status is the same as with aio_read.
605 667
606 aio_copy $srcpath, $dstpath, $callback->($status) 668 aio_copy $srcpath, $dstpath, $callback->($status)
607 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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624 686
625 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;
626 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"
627 and, if that is successful, unlinks the $srcpath. 689 and, if that is successful, unlinks the $srcpath.
628 690
629 aio_scandir $path, $maxreq, $callback->($dirs, $nondirs) 691 aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
630 Scans a directory (similar to "aio_readdir") but additionally tries 692 Scans a directory (similar to "aio_readdir") but additionally tries
631 to efficiently separate the entries of directory $path into two sets 693 to efficiently separate the entries of directory $path into two sets
632 of names, directories you can recurse into (directories), and ones 694 of names, directories you can recurse into (directories), and ones
633 you cannot recurse into (everything else, including symlinks to 695 you cannot recurse into (everything else, including symlinks to
634 directories). 696 directories).
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667 Then entries will be sorted into likely directories a non-initial 729 Then entries will be sorted into likely directories a non-initial
668 dot currently) and likely non-directories (see "aio_readdirx"). Then 730 dot currently) and likely non-directories (see "aio_readdirx"). Then
669 every entry plus an appended "/." will be "stat"'ed, likely 731 every entry plus an appended "/." will be "stat"'ed, likely
670 directories first, in order of their inode numbers. If that 732 directories first, in order of their inode numbers. If that
671 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
672 directory (which will be checked seperately). This is often faster 734 directory (which will be checked separately). This is often faster
673 than stat'ing the entry itself because filesystems might detect the 735 than stat'ing the entry itself because filesystems might detect the
674 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
675 filetype feature), even on systems that cannot return the filetype 737 filetype feature), even on systems that cannot return the filetype
676 information on readdir. 738 information on readdir.
677 739
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683 745
684 It will also likely work on non-POSIX filesystems with reduced 746 It will also likely work on non-POSIX filesystems with reduced
685 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
686 disables the directory counting heuristic. 748 disables the directory counting heuristic.
687 749
688 aio_rmtree $path, $callback->($status) 750 aio_rmtree $pathname, $callback->($status)
689 Delete a directory tree starting (and including) $path, return the 751 Delete a directory tree starting (and including) $path, return the
690 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
691 uses "aio_scandir" to recurse into and rmdir directories, and unlink 753 uses "aio_scandir" to recurse into and rmdir directories, and unlink
692 everything else. 754 everything else.
693 755
… …
702 Asynchronously call fdatasync on the given filehandle and call the 764 Asynchronously call fdatasync on the given filehandle and call the
703 callback with the fdatasync result code. 765 callback with the fdatasync result code.
704 766
705 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
706 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.
707 775
708 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status) 776 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
709 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
710 to disk (but NOT the metadata), by calling the Linux-specific 778 to disk (but NOT the metadata), by calling the Linux-specific
711 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
… …
715 "IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE", 783 "IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE",
716 "IO::AIO::SYNC_FILE_RANGE_WRITE" and 784 "IO::AIO::SYNC_FILE_RANGE_WRITE" and
717 "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
718 manpage for details. 786 manpage for details.
719 787
720 aio_pathsync $path, $callback->($status) 788 aio_pathsync $pathname, $callback->($status)
721 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
722 a composite request intended to sync directories after directory 790 a composite request intended to sync directories after directory
723 operations (E.g. rename). This might not work on all operating 791 operations (E.g. rename). This might not work on all operating
724 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
725 directory changes get written to disc. It works for anything that 793 directory changes get written to disc. It works for anything that
… …
838 requests like sleep and file handle readable/writable, the overhead 906 requests like sleep and file handle readable/writable, the overhead
839 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
840 not use this function except to put your application under 908 not use this function except to put your application under
841 artificial I/O pressure. 909 artificial I/O pressure.
842 910
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
843 IO::AIO::REQ CLASS 1022 IO::AIO::REQ CLASS
844 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
845 called in non-void context. 1024 called in non-void context.
846 1025
847 cancel $req 1026 cancel $req
… …
946 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
947 attached generator that generates requests if idle. The idea behind 1126 attached generator that generates requests if idle. The idea behind
948 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
949 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
950 long time. For example, "aio_scandir" might generate hundreds of 1129 long time. For example, "aio_scandir" might generate hundreds of
951 thousands "aio_stat" requests, delaying any later requests for a 1130 thousands of "aio_stat" requests, delaying any later requests for a
952 long time. 1131 long time.
953 1132
954 To avoid this, and allow incremental generation of requests, you can 1133 To avoid this, and allow incremental generation of requests, you can
955 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
956 requests. The feed callback will be called whenever there are few 1135 requests. The feed callback will be called whenever there are few
… …
999 1178
1000 See "poll_cb" for an example. 1179 See "poll_cb" for an example.
1001 1180
1002 IO::AIO::poll_cb 1181 IO::AIO::poll_cb
1003 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
1004 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
1005 it returned earlier for whatever reason. Returns immediately when no 1184 were no events to process), or -1 if it returned earlier for
1006 events are outstanding. The amount of events processed depends on 1185 whatever reason. Returns immediately when no events are outstanding.
1007 the settings of "IO::AIO::max_poll_req" and 1186 The amount of events processed depends on the settings of
1008 "IO::AIO::max_poll_time". 1187 "IO::AIO::max_poll_req" and "IO::AIO::max_poll_time".
1009 1188
1010 If not all requests were processed for whatever reason, the 1189 If not all requests were processed for whatever reason, the
1011 filehandle will still be ready when "poll_cb" returns, so normally 1190 filehandle will still be ready when "poll_cb" returns, so normally
1012 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.
1013 1199
1014 Example: Install an Event watcher that automatically calls 1200 Example: Install an Event watcher that automatically calls
1015 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
1016 the SYNOPSIS section, at the top of this document): 1202 the SYNOPSIS section, at the top of this document):
1017 1203
… …
1111 1297
1112 Under normal circumstances you don't need to call this function. 1298 Under normal circumstances you don't need to call this function.
1113 1299
1114 IO::AIO::max_idle $nthreads 1300 IO::AIO::max_idle $nthreads
1115 Limit the number of threads (default: 4) that are allowed to idle 1301 Limit the number of threads (default: 4) that are allowed to idle
1116 (i.e., threads that did not get a request to process within 10 1302 (i.e., threads that did not get a request to process within the idle
1117 seconds). That means if a thread becomes idle while $nthreads other 1303 timeout (default: 10 seconds). That means if a thread becomes idle
1118 threads are also idle, it will free its resources and exit. 1304 while $nthreads other threads are also idle, it will free its
1305 resources and exit.
1119 1306
1120 This is useful when you allow a large number of threads (e.g. 100 or 1307 This is useful when you allow a large number of threads (e.g. 100 or
1121 1000) to allow for extremely high load situations, but want to free 1308 1000) to allow for extremely high load situations, but want to free
1122 resources under normal circumstances (1000 threads can easily 1309 resources under normal circumstances (1000 threads can easily
1123 consume 30MB of RAM). 1310 consume 30MB of RAM).
1124 1311
1125 The default is probably ok in most situations, especially if thread 1312 The default is probably ok in most situations, especially if thread
1126 creation is fast. If thread creation is very slow on your system you 1313 creation is fast. If thread creation is very slow on your system you
1127 might want to use larger values. 1314 might want to use larger values.
1128 1315
1316 IO::AIO::idle_timeout $seconds
1317 Sets the minimum idle timeout (default 10) after which worker
1318 threads are allowed to exit. SEe "IO::AIO::max_idle".
1319
1129 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
1130 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
1131 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
1132 inexact: Better use an "aio_group" together with a feed callback. 1332 inexact: Better use an "aio_group" together with a feed callback.
1133 1333
1134 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
1135 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:
1136 "poll_cb" (and "poll_some" and other functions calling "poll_cb")
1137 function will block until the limit is no longer exceeded.
1138 1336
1139 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
1140 the number of outstanding requests. 1353 no practical limit on the number of outstanding requests.
1141
1142 You can still queue as many requests as you want. Therefore,
1143 "max_outstanding" is mainly useful in simple scripts (with low
1144 values) or as a stop gap to shield against fatal memory overflow
1145 (with large values).
1146 1354
1147 STATISTICAL INFORMATION 1355 STATISTICAL INFORMATION
1148 IO::AIO::nreqs 1356 IO::AIO::nreqs
1149 Returns the number of requests currently in the ready, execute or 1357 Returns the number of requests currently in the ready, execute or
1150 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
… …
1175 1383
1176 Returns the number of bytes copied, or -1 on error. 1384 Returns the number of bytes copied, or -1 on error.
1177 1385
1178 IO::AIO::fadvise $fh, $offset, $len, $advice 1386 IO::AIO::fadvise $fh, $offset, $len, $advice
1179 Simply calls the "posix_fadvise" function (see its manpage for 1387 Simply calls the "posix_fadvise" function (see its manpage for
1180 details). The following advice constants are avaiable: 1388 details). The following advice constants are available:
1181 "IO::AIO::FADV_NORMAL", "IO::AIO::FADV_SEQUENTIAL", 1389 "IO::AIO::FADV_NORMAL", "IO::AIO::FADV_SEQUENTIAL",
1182 "IO::AIO::FADV_RANDOM", "IO::AIO::FADV_NOREUSE", 1390 "IO::AIO::FADV_RANDOM", "IO::AIO::FADV_NOREUSE",
1183 "IO::AIO::FADV_WILLNEED", "IO::AIO::FADV_DONTNEED". 1391 "IO::AIO::FADV_WILLNEED", "IO::AIO::FADV_DONTNEED".
1184 1392
1185 On systems that do not implement "posix_fadvise", this function 1393 On systems that do not implement "posix_fadvise", this function
1186 returns ENOSYS, otherwise the return value of "posix_fadvise". 1394 returns ENOSYS, otherwise the return value of "posix_fadvise".
1187 1395
1188 IO::AIO::madvise $scalar, $offset, $len, $advice 1396 IO::AIO::madvise $scalar, $offset, $len, $advice
1189 Simply calls the "posix_madvise" function (see its manpage for 1397 Simply calls the "posix_madvise" function (see its manpage for
1190 details). The following advice constants are avaiable: 1398 details). The following advice constants are available:
1191 "IO::AIO::MADV_NORMAL", "IO::AIO::MADV_SEQUENTIAL", 1399 "IO::AIO::MADV_NORMAL", "IO::AIO::MADV_SEQUENTIAL",
1192 "IO::AIO::MADV_RANDOM", "IO::AIO::MADV_WILLNEED", 1400 "IO::AIO::MADV_RANDOM", "IO::AIO::MADV_WILLNEED",
1193 "IO::AIO::MADV_DONTNEED". 1401 "IO::AIO::MADV_DONTNEED".
1194 1402
1195 On systems that do not implement "posix_madvise", this function 1403 On systems that do not implement "posix_madvise", this function
1196 returns ENOSYS, otherwise the return value of "posix_madvise". 1404 returns ENOSYS, otherwise the return value of "posix_madvise".
1197 1405
1198 IO::AIO::mprotect $scalar, $offset, $len, $protect 1406 IO::AIO::mprotect $scalar, $offset, $len, $protect
1199 Simply calls the "mprotect" function on the preferably AIO::mmap'ed 1407 Simply calls the "mprotect" function on the preferably AIO::mmap'ed
1200 $scalar (see its manpage for details). The following protect 1408 $scalar (see its manpage for details). The following protect
1201 constants are avaiable: "IO::AIO::PROT_NONE", "IO::AIO::PROT_READ", 1409 constants are available: "IO::AIO::PROT_NONE", "IO::AIO::PROT_READ",
1202 "IO::AIO::PROT_WRITE", "IO::AIO::PROT_EXEC". 1410 "IO::AIO::PROT_WRITE", "IO::AIO::PROT_EXEC".
1203 1411
1204 On systems that do not implement "mprotect", this function returns 1412 On systems that do not implement "mprotect", this function returns
1205 ENOSYS, otherwise the return value of "mprotect". 1413 ENOSYS, otherwise the return value of "mprotect".
1206 1414
… …
1296 # Danga::Socket integration 1504 # Danga::Socket integration
1297 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno => 1505 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
1298 \&IO::AIO::poll_cb); 1506 \&IO::AIO::poll_cb);
1299 1507
1300 FORK BEHAVIOUR 1508 FORK BEHAVIOUR
1301 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.
1302 1516
1303 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
1304 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
1305 fork the parent simply leaves the quiescent state and continues 1519 supported, but using IO::AIO in the child is not.
1306 request/result processing, while the child frees the request/result
1307 queue (so that the requests started before the fork will only be handled
1308 in the parent). Threads will be started on demand until the limit set in
1309 the parent process has been reached again.
1310 1520
1311 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.
1312 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:
1313 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.
1314 1535
1315 MEMORY USAGE 1536 MEMORY USAGE
1316 Per-request usage: 1537 Per-request usage:
1317 1538
1318 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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