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Revision 1.50 by root, Sun Oct 9 08:24:49 2011 UTC

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2 IO::AIO - Asynchronous Input/Output 2 IO::AIO - Asynchronous Input/Output
3 3
4SYNOPSIS 4SYNOPSIS
5 use IO::AIO; 5 use IO::AIO;
6 6
7 aio_open "/etc/passwd", O_RDONLY, 0, sub { 7 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
8 my $fh = shift 8 my $fh = shift
9 or die "/etc/passwd: $!"; 9 or die "/etc/passwd: $!";
10 ... 10 ...
11 }; 11 };
12 12
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72 72
73 # register the IO::AIO callback with EV 73 # register the IO::AIO callback with EV
74 my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb; 74 my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
75 75
76 # queue the request to open /etc/passwd 76 # queue the request to open /etc/passwd
77 aio_open "/etc/passwd", O_RDONLY, 0, sub { 77 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
78 my $fh = shift 78 my $fh = shift
79 or die "error while opening: $!"; 79 or die "error while opening: $!";
80 80
81 # stat'ing filehandles is generally non-blocking 81 # stat'ing filehandles is generally non-blocking
82 my $size = -s $fh; 82 my $size = -s $fh;
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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)
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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)
195 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
196 aio_mlockall $flags, $callback->($status)
192 aio_group $callback->(...) 197 aio_group $callback->(...)
193 aio_nop $callback->() 198 aio_nop $callback->()
194 199
195 $prev_pri = aioreq_pri [$pri] 200 $prev_pri = aioreq_pri [$pri]
196 aioreq_nice $pri_adjust 201 aioreq_nice $pri_adjust
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202 IO::AIO::max_poll_reqs $nreqs 207 IO::AIO::max_poll_reqs $nreqs
203 IO::AIO::max_poll_time $seconds 208 IO::AIO::max_poll_time $seconds
204 IO::AIO::min_parallel $nthreads 209 IO::AIO::min_parallel $nthreads
205 IO::AIO::max_parallel $nthreads 210 IO::AIO::max_parallel $nthreads
206 IO::AIO::max_idle $nthreads 211 IO::AIO::max_idle $nthreads
212 IO::AIO::idle_timeout $seconds
207 IO::AIO::max_outstanding $maxreqs 213 IO::AIO::max_outstanding $maxreqs
208 IO::AIO::nreqs 214 IO::AIO::nreqs
209 IO::AIO::nready 215 IO::AIO::nready
210 IO::AIO::npending 216 IO::AIO::npending
211 217
212 IO::AIO::sendfile $ofh, $ifh, $offset, $count 218 IO::AIO::sendfile $ofh, $ifh, $offset, $count
213 IO::AIO::fadvise $fh, $offset, $len, $advice 219 IO::AIO::fadvise $fh, $offset, $len, $advice
214 IO::AIO::mlockall $flags 220 IO::AIO::madvise $scalar, $offset, $length, $advice
221 IO::AIO::mprotect $scalar, $offset, $length, $protect
222 IO::AIO::munlock $scalar, $offset = 0, $length = undef
215 IO::AIO::munlockall 223 IO::AIO::munlockall
216 224
217 AIO REQUEST FUNCTIONS 225 AIO REQUEST FUNCTIONS
218 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
219 with the same name (sans "aio_"). The arguments are similar or 227 with the same name (sans "aio_"). The arguments are similar or
220 identical, and they all accept an additional (and optional) $callback 228 identical, and they all accept an additional (and optional) $callback
221 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
222 called with the syscall return code (e.g. most syscalls return -1 on
223 error, unlike perl, which usually delivers "false") as its sole argument
224 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".
225 238
226 All functions expecting a filehandle keep a copy of the filehandle 239 All functions expecting a filehandle keep a copy of the filehandle
227 internally until the request has finished. 240 internally until the request has finished.
228 241
229 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
230 further manipulation of those requests while they are in-flight. 243 further manipulation of those requests while they are in-flight.
231 244
232 The pathnames you pass to these routines *must* be absolute and encoded 245 The pathnames you pass to these routines *should* be absolute. The
233 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
234 being executed, the current working directory could have changed. 247 current working directory could have changed. Alternatively, you can
235 Alternatively, you can make sure that you never change the current 248 make sure that you never change the current working directory anywhere
236 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.
237 253
238 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
239 pass in filenames you got from outside (command line, readdir etc.) 255 pass in filenames you got from outside (command line, readdir etc.)
240 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
241 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)
242 the user environment, d) use Glib::filename_from_unicode on unicode 258 encoding in effect in the user environment, d) use
243 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
244 contents. 260 else to ensure your scalar has the correct contents.
245 261
246 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
247 handles correctly whether it is set or not. 263 handles correctly whether it is set or not.
248 264
249 $prev_pri = aioreq_pri [$pri] 265 $prev_pri = aioreq_pri [$pri]
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292 will be modified by the umask in effect then the request is being 308 will be modified by the umask in effect then the request is being
293 executed, so better never change the umask. 309 executed, so better never change the umask.
294 310
295 Example: 311 Example:
296 312
297 aio_open "/etc/passwd", O_RDONLY, 0, sub { 313 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
298 if ($_[0]) { 314 if ($_[0]) {
299 print "open successful, fh is $_[0]\n"; 315 print "open successful, fh is $_[0]\n";
300 ... 316 ...
301 } else { 317 } else {
302 die "open failed: $!\n"; 318 die "open failed: $!\n";
303 } 319 }
304 }; 320 };
305 321
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
306 aio_close $fh, $callback->($status) 331 aio_close $fh, $callback->($status)
307 Asynchronously close a file and call the callback with the result 332 Asynchronously close a file and call the callback with the result
308 code. 333 code.
309 334
310 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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353 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval) 378 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
354 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
355 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
356 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
357 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
358 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.
359 385
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
360 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
361 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
362 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.
363 406
364 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",
365 "ENOTSUP", "EOPNOTSUPP", "EAFNOSUPPORT", "EPROTOTYPE" or "ENOTSOCK", 408 "EINVAL", "ENOTSUP", "EOPNOTSUPP", "EAFNOSUPPORT", "EPROTOTYPE" or
366 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
367 filehandle regardless of the limitations of the operating system. 410 any type of filehandle regardless of the limitations of the
411 operating system.
368 412
369 Please note, however, that "aio_sendfile" can read more bytes from 413 As native sendfile syscalls (as practically any non-POSIX interface
370 $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
371 bytes have been read from "aio_sendfile" alone, as "aio_sendfile" 415 rather buggy on many systems, this implementation tries to work
372 only provides the number of bytes written to $out_fh. Only if the 416 around some known bugs in Linux and FreeBSD kernels (probably
373 result value equals $length one can assume that $length bytes have 417 others, too), but that might fail, so you really really should check
374 been read. 418 the return value of "aio_sendfile" - fewre bytes than expected might
419 have been transferred.
375 420
376 aio_readahead $fh,$offset,$length, $callback->($retval) 421 aio_readahead $fh,$offset,$length, $callback->($retval)
377 "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
378 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
379 $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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399 444
400 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
401 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
402 silently truncated unless perl itself is compiled with large file 447 silently truncated unless perl itself is compiled with large file
403 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".
404 458
405 Example: Print the length of /etc/passwd: 459 Example: Print the length of /etc/passwd:
406 460
407 aio_stat "/etc/passwd", sub { 461 aio_stat "/etc/passwd", sub {
408 $_[0] and die "stat failed: $!"; 462 $_[0] and die "stat failed: $!";
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488 542
489 aio_unlink $pathname, $callback->($status) 543 aio_unlink $pathname, $callback->($status)
490 Asynchronously unlink (delete) a file and call the callback with the 544 Asynchronously unlink (delete) a file and call the callback with the
491 result code. 545 result code.
492 546
493 aio_mknod $path, $mode, $dev, $callback->($status) 547 aio_mknod $pathname, $mode, $dev, $callback->($status)
494 [EXPERIMENTAL] 548 [EXPERIMENTAL]
495 549
496 Asynchronously create a device node (or fifo). See mknod(2). 550 Asynchronously create a device node (or fifo). See mknod(2).
497 551
498 The only (POSIX-) portable way of calling this function is: 552 The only (POSIX-) portable way of calling this function is:
499 553
500 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.
501 558
502 aio_link $srcpath, $dstpath, $callback->($status) 559 aio_link $srcpath, $dstpath, $callback->($status)
503 Asynchronously create a new link to the existing object at $srcpath 560 Asynchronously create a new link to the existing object at $srcpath
504 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.
505 562
506 aio_symlink $srcpath, $dstpath, $callback->($status) 563 aio_symlink $srcpath, $dstpath, $callback->($status)
507 Asynchronously create a new symbolic link to the existing object at 564 Asynchronously create a new symbolic link to the existing object at
508 $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
509 code. 566 code.
510 567
511 aio_readlink $path, $callback->($link) 568 aio_readlink $pathname, $callback->($link)
512 Asynchronously read the symlink specified by $path and pass it to 569 Asynchronously read the symlink specified by $path and pass it to
513 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
514 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).
515 580
516 aio_rename $srcpath, $dstpath, $callback->($status) 581 aio_rename $srcpath, $dstpath, $callback->($status)
517 Asynchronously rename the object at $srcpath to $dstpath, just as 582 Asynchronously rename the object at $srcpath to $dstpath, just as
518 rename(2) and call the callback with the result code. 583 rename(2) and call the callback with the result code.
519 584
… …
533 598
534 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
535 an array-ref with the filenames. 600 an array-ref with the filenames.
536 601
537 aio_readdirx $pathname, $flags, $callback->($entries, $flags) 602 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
538 Quite similar to "aio_readdir", but the $flags argument allows to 603 Quite similar to "aio_readdir", but the $flags argument allows one
539 tune behaviour and output format. In case of an error, $entries will 604 to tune behaviour and output format. In case of an error, $entries
540 be "undef". 605 will be "undef".
541 606
542 The flags are a combination of the following constants, ORed 607 The flags are a combination of the following constants, ORed
543 together (the flags will also be passed to the callback, possibly 608 together (the flags will also be passed to the callback, possibly
544 modified): 609 modified):
545 610
546 IO::AIO::READDIR_DENTS 611 IO::AIO::READDIR_DENTS
547 When this flag is off, then the callback gets an arrayref with 612 When this flag is off, then the callback gets an arrayref
548 of names only (as with "aio_readdir"), otherwise it gets an 613 consisting of names only (as with "aio_readdir"), otherwise it
549 arrayref with "[$name, $type, $inode]" arrayrefs, each 614 gets an arrayref with "[$name, $type, $inode]" arrayrefs, each
550 describing a single directory entry in more detail. 615 describing a single directory entry in more detail.
551 616
552 $name is the name of the entry. 617 $name is the name of the entry.
553 618
554 $type is one of the "IO::AIO::DT_xxx" constants: 619 $type is one of the "IO::AIO::DT_xxx" constants:
… …
567 unspecified content on systems that do not deliver the inode 632 unspecified content on systems that do not deliver the inode
568 information. 633 information.
569 634
570 IO::AIO::READDIR_DIRS_FIRST 635 IO::AIO::READDIR_DIRS_FIRST
571 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
572 order where likely directories come first. This is useful when 637 order where likely directories come first, in optimal stat
573 you need to quickly find directories, or you want to find all 638 order. This is useful when you need to quickly find directories,
574 directories while avoiding to stat() each entry. 639 or you want to find all directories while avoiding to stat()
640 each entry.
575 641
576 If the system returns type information in readdir, then this is 642 If the system returns type information in readdir, then this is
577 used to find directories directly. Otherwise, likely directories 643 used to find directories directly. Otherwise, likely directories
578 are files beginning with ".", or otherwise files with no dots, 644 are names beginning with ".", or otherwise names with no dots,
579 of which files with short names are tried first. 645 of which names with short names are tried first.
580 646
581 IO::AIO::READDIR_STAT_ORDER 647 IO::AIO::READDIR_STAT_ORDER
582 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
583 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
584 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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589 optimal stat order. 655 optimal stat order.
590 656
591 IO::AIO::READDIR_FOUND_UNKNOWN 657 IO::AIO::READDIR_FOUND_UNKNOWN
592 This flag should not be set when calling "aio_readdirx". 658 This flag should not be set when calling "aio_readdirx".
593 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
594 $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
595 flag therefore indicates that all $type's are known, which can 661 flag therefore indicates that all $type's are known, which can
596 be used to speed up some algorithms. 662 be used to speed up some algorithms.
597 663
598 aio_load $path, $data, $callback->($status) 664 aio_load $pathname, $data, $callback->($status)
599 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
600 into memory. Status is the same as with aio_read. 666 into memory. Status is the same as with aio_read.
601 667
602 aio_copy $srcpath, $dstpath, $callback->($status) 668 aio_copy $srcpath, $dstpath, $callback->($status)
603 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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620 686
621 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;
622 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"
623 and, if that is successful, unlinks the $srcpath. 689 and, if that is successful, unlinks the $srcpath.
624 690
625 aio_scandir $path, $maxreq, $callback->($dirs, $nondirs) 691 aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
626 Scans a directory (similar to "aio_readdir") but additionally tries 692 Scans a directory (similar to "aio_readdir") but additionally tries
627 to efficiently separate the entries of directory $path into two sets 693 to efficiently separate the entries of directory $path into two sets
628 of names, directories you can recurse into (directories), and ones 694 of names, directories you can recurse into (directories), and ones
629 you cannot recurse into (everything else, including symlinks to 695 you cannot recurse into (everything else, including symlinks to
630 directories). 696 directories).
… …
663 Then entries will be sorted into likely directories a non-initial 729 Then entries will be sorted into likely directories a non-initial
664 dot currently) and likely non-directories (see "aio_readdirx"). Then 730 dot currently) and likely non-directories (see "aio_readdirx"). Then
665 every entry plus an appended "/." will be "stat"'ed, likely 731 every entry plus an appended "/." will be "stat"'ed, likely
666 directories first, in order of their inode numbers. If that 732 directories first, in order of their inode numbers. If that
667 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
668 directory (which will be checked seperately). This is often faster 734 directory (which will be checked separately). This is often faster
669 than stat'ing the entry itself because filesystems might detect the 735 than stat'ing the entry itself because filesystems might detect the
670 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
671 filetype feature), even on systems that cannot return the filetype 737 filetype feature), even on systems that cannot return the filetype
672 information on readdir. 738 information on readdir.
673 739
… …
679 745
680 It will also likely work on non-POSIX filesystems with reduced 746 It will also likely work on non-POSIX filesystems with reduced
681 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
682 disables the directory counting heuristic. 748 disables the directory counting heuristic.
683 749
684 aio_rmtree $path, $callback->($status) 750 aio_rmtree $pathname, $callback->($status)
685 Delete a directory tree starting (and including) $path, return the 751 Delete a directory tree starting (and including) $path, return the
686 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
687 uses "aio_scandir" to recurse into and rmdir directories, and unlink 753 uses "aio_scandir" to recurse into and rmdir directories, and unlink
688 everything else. 754 everything else.
689 755
… …
698 Asynchronously call fdatasync on the given filehandle and call the 764 Asynchronously call fdatasync on the given filehandle and call the
699 callback with the fdatasync result code. 765 callback with the fdatasync result code.
700 766
701 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
702 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.
703 775
704 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status) 776 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
705 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
706 to disk (but NOT the metadata), by calling the Linux-specific 778 to disk (but NOT the metadata), by calling the Linux-specific
707 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
… …
711 "IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE", 783 "IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE",
712 "IO::AIO::SYNC_FILE_RANGE_WRITE" and 784 "IO::AIO::SYNC_FILE_RANGE_WRITE" and
713 "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
714 manpage for details. 786 manpage for details.
715 787
716 aio_pathsync $path, $callback->($status) 788 aio_pathsync $pathname, $callback->($status)
717 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
718 a composite request intended to sync directories after directory 790 a composite request intended to sync directories after directory
719 operations (E.g. rename). This might not work on all operating 791 operations (E.g. rename). This might not work on all operating
720 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
721 directory changes get written to disc. It works for anything that 793 directory changes get written to disc. It works for anything that
… …
751 "aio_msync", above, except for flags, which must be either 0 (which 823 "aio_msync", above, except for flags, which must be either 0 (which
752 reads all pages and ensures they are instantiated) or 824 reads all pages and ensures they are instantiated) or
753 "IO::AIO::MT_MODIFY", which modifies the memory page s(by reading 825 "IO::AIO::MT_MODIFY", which modifies the memory page s(by reading
754 and writing an octet from it, which dirties the page). 826 and writing an octet from it, which dirties the page).
755 827
828 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
829 This is a rather advanced IO::AIO call, which works best on
830 mmap(2)ed scalars.
831
832 It reads in all the pages of the underlying storage into memory (if
833 any) and locks them, so they are not getting swapped/paged out or
834 removed.
835
836 If $length is undefined, then the scalar will be locked till the
837 end.
838
839 On systems that do not implement "mlock", this function returns -1
840 and sets errno to "ENOSYS".
841
842 Note that the corresponding "munlock" is synchronous and is
843 documented under "MISCELLANEOUS FUNCTIONS".
844
845 Example: open a file, mmap and mlock it - both will be undone when
846 $data gets destroyed.
847
848 open my $fh, "<", $path or die "$path: $!";
849 my $data;
850 IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
851 aio_mlock $data; # mlock in background
852
853 aio_mlockall $flags, $callback->($status)
854 Calls the "mlockall" function with the given $flags (a combination
855 of "IO::AIO::MCL_CURRENT" and "IO::AIO::MCL_FUTURE").
856
857 On systems that do not implement "mlockall", this function returns
858 -1 and sets errno to "ENOSYS".
859
860 Note that the corresponding "munlockall" is synchronous and is
861 documented under "MISCELLANEOUS FUNCTIONS".
862
863 Example: asynchronously lock all current and future pages into
864 memory.
865
866 aio_mlockall IO::AIO::MCL_FUTURE;
867
756 aio_group $callback->(...) 868 aio_group $callback->(...)
757 This is a very special aio request: Instead of doing something, it 869 This is a very special aio request: Instead of doing something, it
758 is a container for other aio requests, which is useful if you want 870 is a container for other aio requests, which is useful if you want
759 to bundle many requests into a single, composite, request with a 871 to bundle many requests into a single, composite, request with a
760 definite callback and the ability to cancel the whole request with 872 definite callback and the ability to cancel the whole request with
… …
793 While it is theoretically handy to have simple I/O scheduling 905 While it is theoretically handy to have simple I/O scheduling
794 requests like sleep and file handle readable/writable, the overhead 906 requests like sleep and file handle readable/writable, the overhead
795 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
796 not use this function except to put your application under 908 not use this function except to put your application under
797 artificial I/O pressure. 909 artificial I/O pressure.
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 { ... };
798 1021
799 IO::AIO::REQ CLASS 1022 IO::AIO::REQ CLASS
800 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
801 called in non-void context. 1024 called in non-void context.
802 1025
… …
902 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
903 attached generator that generates requests if idle. The idea behind 1126 attached generator that generates requests if idle. The idea behind
904 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
905 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
906 long time. For example, "aio_scandir" might generate hundreds of 1129 long time. For example, "aio_scandir" might generate hundreds of
907 thousands "aio_stat" requests, delaying any later requests for a 1130 thousands of "aio_stat" requests, delaying any later requests for a
908 long time. 1131 long time.
909 1132
910 To avoid this, and allow incremental generation of requests, you can 1133 To avoid this, and allow incremental generation of requests, you can
911 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
912 requests. The feed callback will be called whenever there are few 1135 requests. The feed callback will be called whenever there are few
… …
955 1178
956 See "poll_cb" for an example. 1179 See "poll_cb" for an example.
957 1180
958 IO::AIO::poll_cb 1181 IO::AIO::poll_cb
959 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
960 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
961 it returned earlier for whatever reason. Returns immediately when no 1184 were no events to process), or -1 if it returned earlier for
962 events are outstanding. The amount of events processed depends on 1185 whatever reason. Returns immediately when no events are outstanding.
963 the settings of "IO::AIO::max_poll_req" and 1186 The amount of events processed depends on the settings of
964 "IO::AIO::max_poll_time". 1187 "IO::AIO::max_poll_req" and "IO::AIO::max_poll_time".
965 1188
966 If not all requests were processed for whatever reason, the 1189 If not all requests were processed for whatever reason, the
967 filehandle will still be ready when "poll_cb" returns, so normally 1190 filehandle will still be ready when "poll_cb" returns, so normally
968 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.
969 1199
970 Example: Install an Event watcher that automatically calls 1200 Example: Install an Event watcher that automatically calls
971 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
972 the SYNOPSIS section, at the top of this document): 1202 the SYNOPSIS section, at the top of this document):
973 1203
… …
1067 1297
1068 Under normal circumstances you don't need to call this function. 1298 Under normal circumstances you don't need to call this function.
1069 1299
1070 IO::AIO::max_idle $nthreads 1300 IO::AIO::max_idle $nthreads
1071 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
1072 (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
1073 seconds). That means if a thread becomes idle while $nthreads other 1303 timeout (default: 10 seconds). That means if a thread becomes idle
1074 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.
1075 1306
1076 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
1077 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
1078 resources under normal circumstances (1000 threads can easily 1309 resources under normal circumstances (1000 threads can easily
1079 consume 30MB of RAM). 1310 consume 30MB of RAM).
1080 1311
1081 The default is probably ok in most situations, especially if thread 1312 The default is probably ok in most situations, especially if thread
1082 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
1083 might want to use larger values. 1314 might want to use larger values.
1084 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
1085 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
1086 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
1087 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
1088 inexact: Better use an "aio_group" together with a feed callback. 1332 inexact: Better use an "aio_group" together with a feed callback.
1089 1333
1090 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
1091 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:
1092 "poll_cb" (and "poll_some" and other functions calling "poll_cb")
1093 function will block until the limit is no longer exceeded.
1094 1336
1095 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
1096 the number of outstanding requests. 1353 no practical limit on the number of outstanding requests.
1097
1098 You can still queue as many requests as you want. Therefore,
1099 "max_outstanding" is mainly useful in simple scripts (with low
1100 values) or as a stop gap to shield against fatal memory overflow
1101 (with large values).
1102 1354
1103 STATISTICAL INFORMATION 1355 STATISTICAL INFORMATION
1104 IO::AIO::nreqs 1356 IO::AIO::nreqs
1105 Returns the number of requests currently in the ready, execute or 1357 Returns the number of requests currently in the ready, execute or
1106 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
… …
1130 set to non-blocking operations). 1382 set to non-blocking operations).
1131 1383
1132 Returns the number of bytes copied, or -1 on error. 1384 Returns the number of bytes copied, or -1 on error.
1133 1385
1134 IO::AIO::fadvise $fh, $offset, $len, $advice 1386 IO::AIO::fadvise $fh, $offset, $len, $advice
1135 Simply calls the "posix_fadvise" function (see it's manpage for 1387 Simply calls the "posix_fadvise" function (see its manpage for
1136 details). The following advice constants are avaiable: 1388 details). The following advice constants are available:
1137 "IO::AIO::FADV_NORMAL", "IO::AIO::FADV_SEQUENTIAL", 1389 "IO::AIO::FADV_NORMAL", "IO::AIO::FADV_SEQUENTIAL",
1138 "IO::AIO::FADV_RANDOM", "IO::AIO::FADV_NOREUSE", 1390 "IO::AIO::FADV_RANDOM", "IO::AIO::FADV_NOREUSE",
1139 "IO::AIO::FADV_WILLNEED", "IO::AIO::FADV_DONTNEED". 1391 "IO::AIO::FADV_WILLNEED", "IO::AIO::FADV_DONTNEED".
1140 1392
1141 On systems that do not implement "posix_fadvise", this function 1393 On systems that do not implement "posix_fadvise", this function
1142 returns ENOSYS, otherwise the return value of "posix_fadvise". 1394 returns ENOSYS, otherwise the return value of "posix_fadvise".
1395
1396 IO::AIO::madvise $scalar, $offset, $len, $advice
1397 Simply calls the "posix_madvise" function (see its manpage for
1398 details). The following advice constants are available:
1399 "IO::AIO::MADV_NORMAL", "IO::AIO::MADV_SEQUENTIAL",
1400 "IO::AIO::MADV_RANDOM", "IO::AIO::MADV_WILLNEED",
1401 "IO::AIO::MADV_DONTNEED".
1402
1403 On systems that do not implement "posix_madvise", this function
1404 returns ENOSYS, otherwise the return value of "posix_madvise".
1405
1406 IO::AIO::mprotect $scalar, $offset, $len, $protect
1407 Simply calls the "mprotect" function on the preferably AIO::mmap'ed
1408 $scalar (see its manpage for details). The following protect
1409 constants are available: "IO::AIO::PROT_NONE", "IO::AIO::PROT_READ",
1410 "IO::AIO::PROT_WRITE", "IO::AIO::PROT_EXEC".
1411
1412 On systems that do not implement "mprotect", this function returns
1413 ENOSYS, otherwise the return value of "mprotect".
1143 1414
1144 IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset] 1415 IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
1145 Memory-maps a file (or anonymous memory range) and attaches it to 1416 Memory-maps a file (or anonymous memory range) and attaches it to
1146 the given $scalar, which will act like a string scalar. 1417 the given $scalar, which will act like a string scalar.
1147 1418
… …
1192 my $fast_md5 = md5 $data; 1463 my $fast_md5 = md5 $data;
1193 1464
1194 IO::AIO::munmap $scalar 1465 IO::AIO::munmap $scalar
1195 Removes a previous mmap and undefines the $scalar. 1466 Removes a previous mmap and undefines the $scalar.
1196 1467
1197 IO::AIO::mlockall $flags 1468 IO::AIO::munlock $scalar, $offset = 0, $length = undef
1198 Calls the "mlockall" function with the given $flags (a combination 1469 Calls the "munlock" function, undoing the effects of a previous
1199 of "IO::AIO::MCL_CURRENT" and "IO::AIO::MCL__FUTURE"). 1470 "aio_mlock" call (see its description for details).
1200
1201 On systems that do not implement "mlockall", this function returns
1202 ENOSYS, otherwise the return value of "mlockall".
1203 1471
1204 IO::AIO::munlockall 1472 IO::AIO::munlockall
1205 Calls the "munlockall" function. 1473 Calls the "munlockall" function.
1206 1474
1207 On systems that do not implement "munlockall", this function returns 1475 On systems that do not implement "munlockall", this function returns
… …
1236 # Danga::Socket integration 1504 # Danga::Socket integration
1237 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno => 1505 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
1238 \&IO::AIO::poll_cb); 1506 \&IO::AIO::poll_cb);
1239 1507
1240 FORK BEHAVIOUR 1508 FORK BEHAVIOUR
1241 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.
1242 1516
1243 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
1244 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
1245 fork the parent simply leaves the quiescent state and continues 1519 supported, but using IO::AIO in the child is not.
1246 request/result processing, while the child frees the request/result
1247 queue (so that the requests started before the fork will only be handled
1248 in the parent). Threads will be started on demand until the limit set in
1249 the parent process has been reached again.
1250 1520
1251 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.
1252 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:
1253 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.
1254 1535
1255 MEMORY USAGE 1536 MEMORY USAGE
1256 Per-request usage: 1537 Per-request usage:
1257 1538
1258 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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