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Revision 1.51 by root, Sat Apr 7 00:50:33 2012 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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23 my $req = aio_unlink "/tmp/file", sub { }; 23 my $req = aio_unlink "/tmp/file", sub { };
24 $req->cancel; # cancel request if still in queue 24 $req->cancel; # cancel request if still in queue
25 25
26 my $grp = aio_group sub { print "all stats done\n" }; 26 my $grp = aio_group sub { print "all stats done\n" };
27 add $grp aio_stat "..." for ...; 27 add $grp aio_stat "..." for ...;
28
29 # AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
30 use AnyEvent::AIO;
31
32 # EV integration
33 my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
34
35 # Event integration
36 Event->io (fd => IO::AIO::poll_fileno,
37 poll => 'r',
38 cb => \&IO::AIO::poll_cb);
39
40 # Glib/Gtk2 integration
41 add_watch Glib::IO IO::AIO::poll_fileno,
42 in => sub { IO::AIO::poll_cb; 1 };
43
44 # Tk integration
45 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
46 readable => \&IO::AIO::poll_cb);
47
48 # Danga::Socket integration
49 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
50 \&IO::AIO::poll_cb);
51 28
52DESCRIPTION 29DESCRIPTION
53 This module implements asynchronous I/O using whatever means your 30 This module implements asynchronous I/O using whatever means your
54 operating system supports. It is implemented as an interface to "libeio" 31 operating system supports. It is implemented as an interface to "libeio"
55 (<http://software.schmorp.de/pkg/libeio.html>). 32 (<http://software.schmorp.de/pkg/libeio.html>).
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95 72
96 # register the IO::AIO callback with EV 73 # register the IO::AIO callback with EV
97 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;
98 75
99 # queue the request to open /etc/passwd 76 # queue the request to open /etc/passwd
100 aio_open "/etc/passwd", O_RDONLY, 0, sub { 77 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
101 my $fh = shift 78 my $fh = shift
102 or die "error while opening: $!"; 79 or die "error while opening: $!";
103 80
104 # stat'ing filehandles is generally non-blocking 81 # stat'ing filehandles is generally non-blocking
105 my $size = -s $fh; 82 my $size = -s $fh;
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168 anymore (except possibly for the Perl object, but its connection to 145 anymore (except possibly for the Perl object, but its connection to
169 the actual aio request is severed and calling its methods will 146 the actual aio request is severed and calling its methods will
170 either do nothing or result in a runtime error). 147 either do nothing or result in a runtime error).
171 148
172FUNCTIONS 149FUNCTIONS
173 AIO REQUEST FUNCTIONS 150 QUICK OVERVIEW
151 This section simply lists the prototypes of the most important functions
152 for quick reference. See the following sections for function-by-function
153 documentation.
154
155 aio_wd $pathname, $callback->($wd)
156 aio_open $pathname, $flags, $mode, $callback->($fh)
157 aio_close $fh, $callback->($status)
158 aio_seek $fh,$offset,$whence, $callback->($offs)
159 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
160 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
161 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
162 aio_readahead $fh,$offset,$length, $callback->($retval)
163 aio_stat $fh_or_path, $callback->($status)
164 aio_lstat $fh, $callback->($status)
165 aio_statvfs $fh_or_path, $callback->($statvfs)
166 aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
167 aio_chown $fh_or_path, $uid, $gid, $callback->($status)
168 aio_chmod $fh_or_path, $mode, $callback->($status)
169 aio_truncate $fh_or_path, $offset, $callback->($status)
170 aio_unlink $pathname, $callback->($status)
171 aio_mknod $pathname, $mode, $dev, $callback->($status)
172 aio_link $srcpath, $dstpath, $callback->($status)
173 aio_symlink $srcpath, $dstpath, $callback->($status)
174 aio_readlink $pathname, $callback->($link)
175 aio_realpath $pathname, $callback->($link)
176 aio_rename $srcpath, $dstpath, $callback->($status)
177 aio_mkdir $pathname, $mode, $callback->($status)
178 aio_rmdir $pathname, $callback->($status)
179 aio_readdir $pathname, $callback->($entries)
180 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
181 IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
182 IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
183 aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
184 aio_load $pathname, $data, $callback->($status)
185 aio_copy $srcpath, $dstpath, $callback->($status)
186 aio_move $srcpath, $dstpath, $callback->($status)
187 aio_rmtree $pathname, $callback->($status)
188 aio_sync $callback->($status)
189 aio_syncfs $fh, $callback->($status)
190 aio_fsync $fh, $callback->($status)
191 aio_fdatasync $fh, $callback->($status)
192 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
193 aio_pathsync $pathname, $callback->($status)
194 aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
195 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
196 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
197 aio_mlockall $flags, $callback->($status)
198 aio_group $callback->(...)
199 aio_nop $callback->()
200
201 $prev_pri = aioreq_pri [$pri]
202 aioreq_nice $pri_adjust
203
204 IO::AIO::poll_wait
205 IO::AIO::poll_cb
206 IO::AIO::poll
207 IO::AIO::flush
208 IO::AIO::max_poll_reqs $nreqs
209 IO::AIO::max_poll_time $seconds
210 IO::AIO::min_parallel $nthreads
211 IO::AIO::max_parallel $nthreads
212 IO::AIO::max_idle $nthreads
213 IO::AIO::idle_timeout $seconds
214 IO::AIO::max_outstanding $maxreqs
215 IO::AIO::nreqs
216 IO::AIO::nready
217 IO::AIO::npending
218
219 IO::AIO::sendfile $ofh, $ifh, $offset, $count
220 IO::AIO::fadvise $fh, $offset, $len, $advice
221 IO::AIO::madvise $scalar, $offset, $length, $advice
222 IO::AIO::mprotect $scalar, $offset, $length, $protect
223 IO::AIO::munlock $scalar, $offset = 0, $length = undef
224 IO::AIO::munlockall
225
226 API NOTES
174 All the "aio_*" calls are more or less thin wrappers around the syscall 227 All the "aio_*" calls are more or less thin wrappers around the syscall
175 with the same name (sans "aio_"). The arguments are similar or 228 with the same name (sans "aio_"). The arguments are similar or
176 identical, and they all accept an additional (and optional) $callback 229 identical, and they all accept an additional (and optional) $callback
177 argument which must be a code reference. This code reference will get 230 argument which must be a code reference. This code reference will be
178 called with the syscall return code (e.g. most syscalls return -1 on
179 error, unlike perl, which usually delivers "false") as its sole argument
180 after the given syscall has been executed asynchronously. 231 called after the syscall has been executed in an asynchronous fashion.
232 The results of the request will be passed as arguments to the callback
233 (and, if an error occured, in $!) - for most requests the syscall return
234 code (e.g. most syscalls return -1 on error, unlike perl, which usually
235 delivers "false").
236
237 Some requests (such as "aio_readdir") pass the actual results and
238 communicate failures by passing "undef".
181 239
182 All functions expecting a filehandle keep a copy of the filehandle 240 All functions expecting a filehandle keep a copy of the filehandle
183 internally until the request has finished. 241 internally until the request has finished.
184 242
185 All functions return request objects of type IO::AIO::REQ that allow 243 All functions return request objects of type IO::AIO::REQ that allow
186 further manipulation of those requests while they are in-flight. 244 further manipulation of those requests while they are in-flight.
187 245
188 The pathnames you pass to these routines *must* be absolute and encoded 246 The pathnames you pass to these routines *should* be absolute. The
189 as octets. The reason for the former is that at the time the request is 247 reason for this is that at the time the request is being executed, the
190 being executed, the current working directory could have changed. 248 current working directory could have changed. Alternatively, you can
191 Alternatively, you can make sure that you never change the current 249 make sure that you never change the current working directory anywhere
192 working directory anywhere in the program and then use relative paths. 250 in the program and then use relative paths. You can also take advantage
251 of IO::AIOs working directory abstraction, that lets you specify paths
252 relative to some previously-opened "working directory object" - see the
253 description of the "IO::AIO::WD" class later in this document.
193 254
194 To encode pathnames as octets, either make sure you either: a) always 255 To encode pathnames as octets, either make sure you either: a) always
195 pass in filenames you got from outside (command line, readdir etc.) 256 pass in filenames you got from outside (command line, readdir etc.)
196 without tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module 257 without tinkering, b) are in your native filesystem encoding, c) use the
197 and encode your pathnames to the locale (or other) encoding in effect in 258 Encode module and encode your pathnames to the locale (or other)
198 the user environment, d) use Glib::filename_from_unicode on unicode 259 encoding in effect in the user environment, d) use
199 filenames or e) use something else to ensure your scalar has the correct 260 Glib::filename_from_unicode on unicode filenames or e) use something
200 contents. 261 else to ensure your scalar has the correct contents.
201 262
202 This works, btw. independent of the internal UTF-8 bit, which IO::AIO 263 This works, btw. independent of the internal UTF-8 bit, which IO::AIO
203 handles correctly whether it is set or not. 264 handles correctly whether it is set or not.
204 265
266 AIO REQUEST FUNCTIONS
205 $prev_pri = aioreq_pri [$pri] 267 $prev_pri = aioreq_pri [$pri]
206 Returns the priority value that would be used for the next request 268 Returns the priority value that would be used for the next request
207 and, if $pri is given, sets the priority for the next aio request. 269 and, if $pri is given, sets the priority for the next aio request.
208 270
209 The default priority is 0, the minimum and maximum priorities are -4 271 The default priority is 0, the minimum and maximum priorities are -4
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248 will be modified by the umask in effect then the request is being 310 will be modified by the umask in effect then the request is being
249 executed, so better never change the umask. 311 executed, so better never change the umask.
250 312
251 Example: 313 Example:
252 314
253 aio_open "/etc/passwd", O_RDONLY, 0, sub { 315 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
254 if ($_[0]) { 316 if ($_[0]) {
255 print "open successful, fh is $_[0]\n"; 317 print "open successful, fh is $_[0]\n";
256 ... 318 ...
257 } else { 319 } else {
258 die "open failed: $!\n"; 320 die "open failed: $!\n";
259 } 321 }
260 }; 322 };
261 323
324 In addition to all the common open modes/flags ("O_RDONLY",
325 "O_WRONLY", "O_RDWR", "O_CREAT", "O_TRUNC", "O_EXCL" and
326 "O_APPEND"), the following POSIX and non-POSIX constants are
327 available (missing ones on your system are, as usual, 0):
328
329 "O_ASYNC", "O_DIRECT", "O_NOATIME", "O_CLOEXEC", "O_NOCTTY",
330 "O_NOFOLLOW", "O_NONBLOCK", "O_EXEC", "O_SEARCH", "O_DIRECTORY",
331 "O_DSYNC", "O_RSYNC", "O_SYNC" and "O_TTY_INIT".
332
262 aio_close $fh, $callback->($status) 333 aio_close $fh, $callback->($status)
263 Asynchronously close a file and call the callback with the result 334 Asynchronously close a file and call the callback with the result
264 code. 335 code.
265 336
266 Unfortunately, you can't do this to perl. Perl *insists* very 337 Unfortunately, you can't do this to perl. Perl *insists* very
… …
271 will use dup2 to overwrite the file descriptor with the write-end of 342 will use dup2 to overwrite the file descriptor with the write-end of
272 a pipe (the pipe fd will be created on demand and will be cached). 343 a pipe (the pipe fd will be created on demand and will be cached).
273 344
274 Or in other words: the file descriptor will be closed, but it will 345 Or in other words: the file descriptor will be closed, but it will
275 not be free for reuse until the perl filehandle is closed. 346 not be free for reuse until the perl filehandle is closed.
347
348 aio_seek $fh, $offset, $whence, $callback->($offs)
349 Seeks the filehandle to the new $offset, similarly to perl's
350 "sysseek". The $whence can use the traditional values (0 for
351 "IO::AIO::SEEK_SET", 1 for "IO::AIO::SEEK_CUR" or 2 for
352 "IO::AIO::SEEK_END").
353
354 The resulting absolute offset will be passed to the callback, or -1
355 in case of an error.
356
357 In theory, the $whence constants could be different than the
358 corresponding values from Fcntl, but perl guarantees they are the
359 same, so don't panic.
276 360
277 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval) 361 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
278 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval) 362 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
279 Reads or writes $length bytes from or to the specified $fh and 363 Reads or writes $length bytes from or to the specified $fh and
280 $offset into the scalar given by $data and offset $dataoffset and 364 $offset into the scalar given by $data and offset $dataoffset and
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309 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval) 393 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
310 Tries to copy $length bytes from $in_fh to $out_fh. It starts 394 Tries to copy $length bytes from $in_fh to $out_fh. It starts
311 reading at byte offset $in_offset, and starts writing at the current 395 reading at byte offset $in_offset, and starts writing at the current
312 file offset of $out_fh. Because of that, it is not safe to issue 396 file offset of $out_fh. Because of that, it is not safe to issue
313 more than one "aio_sendfile" per $out_fh, as they will interfere 397 more than one "aio_sendfile" per $out_fh, as they will interfere
314 with each other. 398 with each other. The same $in_fh works fine though, as this function
399 does not move or use the file offset of $in_fh.
315 400
401 Please note that "aio_sendfile" can read more bytes from $in_fh than
402 are written, and there is no way to find out how many more bytes
403 have been read from "aio_sendfile" alone, as "aio_sendfile" only
404 provides the number of bytes written to $out_fh. Only if the result
405 value equals $length one can assume that $length bytes have been
406 read.
407
408 Unlike with other "aio_" functions, it makes a lot of sense to use
409 "aio_sendfile" on non-blocking sockets, as long as one end
410 (typically the $in_fh) is a file - the file I/O will then be
411 asynchronous, while the socket I/O will be non-blocking. Note,
412 however, that you can run into a trap where "aio_sendfile" reads
413 some data with readahead, then fails to write all data, and when the
414 socket is ready the next time, the data in the cache is already
415 lost, forcing "aio_sendfile" to again hit the disk. Explicit
416 "aio_read" + "aio_write" let's you better control resource usage.
417
316 This call tries to make use of a native "sendfile" syscall to 418 This call tries to make use of a native "sendfile"-like syscall to
317 provide zero-copy operation. For this to work, $out_fh should refer 419 provide zero-copy operation. For this to work, $out_fh should refer
318 to a socket, and $in_fh should refer to mmap'able file. 420 to a socket, and $in_fh should refer to an mmap'able file.
319 421
320 If the native sendfile call fails or is not implemented, it will be 422 If a native sendfile cannot be found or it fails with "ENOSYS",
321 emulated, so you can call "aio_sendfile" on any type of filehandle 423 "EINVAL", "ENOTSUP", "EOPNOTSUPP", "EAFNOSUPPORT", "EPROTOTYPE" or
322 regardless of the limitations of the operating system. 424 "ENOTSOCK", it will be emulated, so you can call "aio_sendfile" on
425 any type of filehandle regardless of the limitations of the
426 operating system.
323 427
324 Please note, however, that "aio_sendfile" can read more bytes from 428 As native sendfile syscalls (as practically any non-POSIX interface
325 $in_fh than are written, and there is no way to find out how many 429 hacked together in a hurry to improve benchmark numbers) tend to be
326 bytes have been read from "aio_sendfile" alone, as "aio_sendfile" 430 rather buggy on many systems, this implementation tries to work
327 only provides the number of bytes written to $out_fh. Only if the 431 around some known bugs in Linux and FreeBSD kernels (probably
328 result value equals $length one can assume that $length bytes have 432 others, too), but that might fail, so you really really should check
329 been read. 433 the return value of "aio_sendfile" - fewre bytes than expected might
434 have been transferred.
330 435
331 aio_readahead $fh,$offset,$length, $callback->($retval) 436 aio_readahead $fh,$offset,$length, $callback->($retval)
332 "aio_readahead" populates the page cache with data from a file so 437 "aio_readahead" populates the page cache with data from a file so
333 that subsequent reads from that file will not block on disk I/O. The 438 that subsequent reads from that file will not block on disk I/O. The
334 $offset argument specifies the starting point from which data is to 439 $offset argument specifies the starting point from which data is to
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355 Currently, the stats are always 64-bit-stats, i.e. instead of 460 Currently, the stats are always 64-bit-stats, i.e. instead of
356 returning an error when stat'ing a large file, the results will be 461 returning an error when stat'ing a large file, the results will be
357 silently truncated unless perl itself is compiled with large file 462 silently truncated unless perl itself is compiled with large file
358 support. 463 support.
359 464
465 To help interpret the mode and dev/rdev stat values, IO::AIO offers
466 the following constants and functions (if not implemented, the
467 constants will be 0 and the functions will either "croak" or fall
468 back on traditional behaviour).
469
470 "S_IFMT", "S_IFIFO", "S_IFCHR", "S_IFBLK", "S_IFLNK", "S_IFREG",
471 "S_IFDIR", "S_IFWHT", "S_IFSOCK", "IO::AIO::major $dev_t",
472 "IO::AIO::minor $dev_t", "IO::AIO::makedev $major, $minor".
473
360 Example: Print the length of /etc/passwd: 474 Example: Print the length of /etc/passwd:
361 475
362 aio_stat "/etc/passwd", sub { 476 aio_stat "/etc/passwd", sub {
363 $_[0] and die "stat failed: $!"; 477 $_[0] and die "stat failed: $!";
364 print "size is ", -s _, "\n"; 478 print "size is ", -s _, "\n";
365 }; 479 };
366 480
481 aio_statvfs $fh_or_path, $callback->($statvfs)
482 Works like the POSIX "statvfs" or "fstatvfs" syscalls, depending on
483 whether a file handle or path was passed.
484
485 On success, the callback is passed a hash reference with the
486 following members: "bsize", "frsize", "blocks", "bfree", "bavail",
487 "files", "ffree", "favail", "fsid", "flag" and "namemax". On
488 failure, "undef" is passed.
489
490 The following POSIX IO::AIO::ST_* constants are defined: "ST_RDONLY"
491 and "ST_NOSUID".
492
493 The following non-POSIX IO::AIO::ST_* flag masks are defined to
494 their correct value when available, or to 0 on systems that do not
495 support them: "ST_NODEV", "ST_NOEXEC", "ST_SYNCHRONOUS",
496 "ST_MANDLOCK", "ST_WRITE", "ST_APPEND", "ST_IMMUTABLE",
497 "ST_NOATIME", "ST_NODIRATIME" and "ST_RELATIME".
498
499 Example: stat "/wd" and dump out the data if successful.
500
501 aio_statvfs "/wd", sub {
502 my $f = $_[0]
503 or die "statvfs: $!";
504
505 use Data::Dumper;
506 say Dumper $f;
507 };
508
509 # result:
510 {
511 bsize => 1024,
512 bfree => 4333064312,
513 blocks => 10253828096,
514 files => 2050765568,
515 flag => 4096,
516 favail => 2042092649,
517 bavail => 4333064312,
518 ffree => 2042092649,
519 namemax => 255,
520 frsize => 1024,
521 fsid => 1810
522 }
523
367 aio_utime $fh_or_path, $atime, $mtime, $callback->($status) 524 aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
368 Works like perl's "utime" function (including the special case of 525 Works like perl's "utime" function (including the special case of
369 $atime and $mtime being undef). Fractional times are supported if 526 $atime and $mtime being undef). Fractional times are supported if
370 the underlying syscalls support them. 527 the underlying syscalls support them.
371 528
… …
400 557
401 aio_unlink $pathname, $callback->($status) 558 aio_unlink $pathname, $callback->($status)
402 Asynchronously unlink (delete) a file and call the callback with the 559 Asynchronously unlink (delete) a file and call the callback with the
403 result code. 560 result code.
404 561
405 aio_mknod $path, $mode, $dev, $callback->($status) 562 aio_mknod $pathname, $mode, $dev, $callback->($status)
406 [EXPERIMENTAL] 563 [EXPERIMENTAL]
407 564
408 Asynchronously create a device node (or fifo). See mknod(2). 565 Asynchronously create a device node (or fifo). See mknod(2).
409 566
410 The only (POSIX-) portable way of calling this function is: 567 The only (POSIX-) portable way of calling this function is:
411 568
412 aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ... 569 aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
570
571 See "aio_stat" for info about some potentially helpful extra
572 constants and functions.
413 573
414 aio_link $srcpath, $dstpath, $callback->($status) 574 aio_link $srcpath, $dstpath, $callback->($status)
415 Asynchronously create a new link to the existing object at $srcpath 575 Asynchronously create a new link to the existing object at $srcpath
416 at the path $dstpath and call the callback with the result code. 576 at the path $dstpath and call the callback with the result code.
417 577
418 aio_symlink $srcpath, $dstpath, $callback->($status) 578 aio_symlink $srcpath, $dstpath, $callback->($status)
419 Asynchronously create a new symbolic link to the existing object at 579 Asynchronously create a new symbolic link to the existing object at
420 $srcpath at the path $dstpath and call the callback with the result 580 $srcpath at the path $dstpath and call the callback with the result
421 code. 581 code.
422 582
423 aio_readlink $path, $callback->($link) 583 aio_readlink $pathname, $callback->($link)
424 Asynchronously read the symlink specified by $path and pass it to 584 Asynchronously read the symlink specified by $path and pass it to
425 the callback. If an error occurs, nothing or undef gets passed to 585 the callback. If an error occurs, nothing or undef gets passed to
426 the callback. 586 the callback.
587
588 aio_realpath $pathname, $callback->($path)
589 Asynchronously make the path absolute and resolve any symlinks in
590 $path. The resulting path only consists of directories (Same as
591 Cwd::realpath).
592
593 This request can be used to get the absolute path of the current
594 working directory by passing it a path of . (a single dot).
427 595
428 aio_rename $srcpath, $dstpath, $callback->($status) 596 aio_rename $srcpath, $dstpath, $callback->($status)
429 Asynchronously rename the object at $srcpath to $dstpath, just as 597 Asynchronously rename the object at $srcpath to $dstpath, just as
430 rename(2) and call the callback with the result code. 598 rename(2) and call the callback with the result code.
431 599
… …
445 613
446 The callback is passed a single argument which is either "undef" or 614 The callback is passed a single argument which is either "undef" or
447 an array-ref with the filenames. 615 an array-ref with the filenames.
448 616
449 aio_readdirx $pathname, $flags, $callback->($entries, $flags) 617 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
450 Quite similar to "aio_readdir", but the $flags argument allows to 618 Quite similar to "aio_readdir", but the $flags argument allows one
451 tune behaviour and output format. In case of an error, $entries will 619 to tune behaviour and output format. In case of an error, $entries
452 be "undef". 620 will be "undef".
453 621
454 The flags are a combination of the following constants, ORed 622 The flags are a combination of the following constants, ORed
455 together (the flags will also be passed to the callback, possibly 623 together (the flags will also be passed to the callback, possibly
456 modified): 624 modified):
457 625
458 IO::AIO::READDIR_DENTS 626 IO::AIO::READDIR_DENTS
459 When this flag is off, then the callback gets an arrayref with 627 When this flag is off, then the callback gets an arrayref
460 of names only (as with "aio_readdir"), otherwise it gets an 628 consisting of names only (as with "aio_readdir"), otherwise it
461 arrayref with "[$name, $type, $inode]" arrayrefs, each 629 gets an arrayref with "[$name, $type, $inode]" arrayrefs, each
462 describing a single directory entry in more detail. 630 describing a single directory entry in more detail.
463 631
464 $name is the name of the entry. 632 $name is the name of the entry.
465 633
466 $type is one of the "IO::AIO::DT_xxx" constants: 634 $type is one of the "IO::AIO::DT_xxx" constants:
… …
479 unspecified content on systems that do not deliver the inode 647 unspecified content on systems that do not deliver the inode
480 information. 648 information.
481 649
482 IO::AIO::READDIR_DIRS_FIRST 650 IO::AIO::READDIR_DIRS_FIRST
483 When this flag is set, then the names will be returned in an 651 When this flag is set, then the names will be returned in an
484 order where likely directories come first. This is useful when 652 order where likely directories come first, in optimal stat
485 you need to quickly find directories, or you want to find all 653 order. This is useful when you need to quickly find directories,
486 directories while avoiding to stat() each entry. 654 or you want to find all directories while avoiding to stat()
655 each entry.
487 656
488 If the system returns type information in readdir, then this is 657 If the system returns type information in readdir, then this is
489 used to find directories directly. Otherwise, likely directories 658 used to find directories directly. Otherwise, likely directories
490 are files beginning with ".", or otherwise files with no dots, 659 are names beginning with ".", or otherwise names with no dots,
491 of which files with short names are tried first. 660 of which names with short names are tried first.
492 661
493 IO::AIO::READDIR_STAT_ORDER 662 IO::AIO::READDIR_STAT_ORDER
494 When this flag is set, then the names will be returned in an 663 When this flag is set, then the names will be returned in an
495 order suitable for stat()'ing each one. That is, when you plan 664 order suitable for stat()'ing each one. That is, when you plan
496 to stat() all files in the given directory, then the returned 665 to stat() all files in the given directory, then the returned
… …
501 optimal stat order. 670 optimal stat order.
502 671
503 IO::AIO::READDIR_FOUND_UNKNOWN 672 IO::AIO::READDIR_FOUND_UNKNOWN
504 This flag should not be set when calling "aio_readdirx". 673 This flag should not be set when calling "aio_readdirx".
505 Instead, it is being set by "aio_readdirx", when any of the 674 Instead, it is being set by "aio_readdirx", when any of the
506 $type's found were "IO::AIO::DT_UNKNOWN". The absense of this 675 $type's found were "IO::AIO::DT_UNKNOWN". The absence of this
507 flag therefore indicates that all $type's are known, which can 676 flag therefore indicates that all $type's are known, which can
508 be used to speed up some algorithms. 677 be used to speed up some algorithms.
509 678
510 aio_load $path, $data, $callback->($status) 679 aio_load $pathname, $data, $callback->($status)
511 This is a composite request that tries to fully load the given file 680 This is a composite request that tries to fully load the given file
512 into memory. Status is the same as with aio_read. 681 into memory. Status is the same as with aio_read.
513 682
514 aio_copy $srcpath, $dstpath, $callback->($status) 683 aio_copy $srcpath, $dstpath, $callback->($status)
515 Try to copy the *file* (directories not supported as either source 684 Try to copy the *file* (directories not supported as either source
516 or destination) from $srcpath to $dstpath and call the callback with 685 or destination) from $srcpath to $dstpath and call the callback with
517 the 0 (error) or -1 ok. 686 a status of 0 (ok) or -1 (error, see $!).
518 687
519 This is a composite request that creates the destination file with 688 This is a composite request that creates the destination file with
520 mode 0200 and copies the contents of the source file into it using 689 mode 0200 and copies the contents of the source file into it using
521 "aio_sendfile", followed by restoring atime, mtime, access mode and 690 "aio_sendfile", followed by restoring atime, mtime, access mode and
522 uid/gid, in that order. 691 uid/gid, in that order.
… …
526 uid/gid, where errors are being ignored. 695 uid/gid, where errors are being ignored.
527 696
528 aio_move $srcpath, $dstpath, $callback->($status) 697 aio_move $srcpath, $dstpath, $callback->($status)
529 Try to move the *file* (directories not supported as either source 698 Try to move the *file* (directories not supported as either source
530 or destination) from $srcpath to $dstpath and call the callback with 699 or destination) from $srcpath to $dstpath and call the callback with
531 the 0 (error) or -1 ok. 700 a status of 0 (ok) or -1 (error, see $!).
532 701
533 This is a composite request that tries to rename(2) the file first; 702 This is a composite request that tries to rename(2) the file first;
534 if rename fails with "EXDEV", it copies the file with "aio_copy" 703 if rename fails with "EXDEV", it copies the file with "aio_copy"
535 and, if that is successful, unlinks the $srcpath. 704 and, if that is successful, unlinks the $srcpath.
536 705
537 aio_scandir $path, $maxreq, $callback->($dirs, $nondirs) 706 aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
538 Scans a directory (similar to "aio_readdir") but additionally tries 707 Scans a directory (similar to "aio_readdir") but additionally tries
539 to efficiently separate the entries of directory $path into two sets 708 to efficiently separate the entries of directory $path into two sets
540 of names, directories you can recurse into (directories), and ones 709 of names, directories you can recurse into (directories), and ones
541 you cannot recurse into (everything else, including symlinks to 710 you cannot recurse into (everything else, including symlinks to
542 directories). 711 directories).
… …
575 Then entries will be sorted into likely directories a non-initial 744 Then entries will be sorted into likely directories a non-initial
576 dot currently) and likely non-directories (see "aio_readdirx"). Then 745 dot currently) and likely non-directories (see "aio_readdirx"). Then
577 every entry plus an appended "/." will be "stat"'ed, likely 746 every entry plus an appended "/." will be "stat"'ed, likely
578 directories first, in order of their inode numbers. If that 747 directories first, in order of their inode numbers. If that
579 succeeds, it assumes that the entry is a directory or a symlink to 748 succeeds, it assumes that the entry is a directory or a symlink to
580 directory (which will be checked seperately). This is often faster 749 directory (which will be checked separately). This is often faster
581 than stat'ing the entry itself because filesystems might detect the 750 than stat'ing the entry itself because filesystems might detect the
582 type of the entry without reading the inode data (e.g. ext2fs 751 type of the entry without reading the inode data (e.g. ext2fs
583 filetype feature), even on systems that cannot return the filetype 752 filetype feature), even on systems that cannot return the filetype
584 information on readdir. 753 information on readdir.
585 754
… …
591 760
592 It will also likely work on non-POSIX filesystems with reduced 761 It will also likely work on non-POSIX filesystems with reduced
593 efficiency as those tend to return 0 or 1 as link counts, which 762 efficiency as those tend to return 0 or 1 as link counts, which
594 disables the directory counting heuristic. 763 disables the directory counting heuristic.
595 764
596 aio_rmtree $path, $callback->($status) 765 aio_rmtree $pathname, $callback->($status)
597 Delete a directory tree starting (and including) $path, return the 766 Delete a directory tree starting (and including) $path, return the
598 status of the final "rmdir" only. This is a composite request that 767 status of the final "rmdir" only. This is a composite request that
599 uses "aio_scandir" to recurse into and rmdir directories, and unlink 768 uses "aio_scandir" to recurse into and rmdir directories, and unlink
600 everything else. 769 everything else.
601 770
… …
610 Asynchronously call fdatasync on the given filehandle and call the 779 Asynchronously call fdatasync on the given filehandle and call the
611 callback with the fdatasync result code. 780 callback with the fdatasync result code.
612 781
613 If this call isn't available because your OS lacks it or it couldn't 782 If this call isn't available because your OS lacks it or it couldn't
614 be detected, it will be emulated by calling "fsync" instead. 783 be detected, it will be emulated by calling "fsync" instead.
784
785 aio_syncfs $fh, $callback->($status)
786 Asynchronously call the syncfs syscall to sync the filesystem
787 associated to the given filehandle and call the callback with the
788 syncfs result code. If syncfs is not available, calls sync(), but
789 returns -1 and sets errno to "ENOSYS" nevertheless.
615 790
616 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status) 791 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
617 Sync the data portion of the file specified by $offset and $length 792 Sync the data portion of the file specified by $offset and $length
618 to disk (but NOT the metadata), by calling the Linux-specific 793 to disk (but NOT the metadata), by calling the Linux-specific
619 sync_file_range call. If sync_file_range is not available or it 794 sync_file_range call. If sync_file_range is not available or it
… …
623 "IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE", 798 "IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE",
624 "IO::AIO::SYNC_FILE_RANGE_WRITE" and 799 "IO::AIO::SYNC_FILE_RANGE_WRITE" and
625 "IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER": refer to the sync_file_range 800 "IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER": refer to the sync_file_range
626 manpage for details. 801 manpage for details.
627 802
628 aio_pathsync $path, $callback->($status) 803 aio_pathsync $pathname, $callback->($status)
629 This request tries to open, fsync and close the given path. This is 804 This request tries to open, fsync and close the given path. This is
630 a composite request intended to sync directories after directory 805 a composite request intended to sync directories after directory
631 operations (E.g. rename). This might not work on all operating 806 operations (E.g. rename). This might not work on all operating
632 systems or have any specific effect, but usually it makes sure that 807 systems or have any specific effect, but usually it makes sure that
633 directory changes get written to disc. It works for anything that 808 directory changes get written to disc. It works for anything that
… …
636 Future versions of this function might fall back to other methods 811 Future versions of this function might fall back to other methods
637 when "fsync" on the directory fails (such as calling "sync"). 812 when "fsync" on the directory fails (such as calling "sync").
638 813
639 Passes 0 when everything went ok, and -1 on error. 814 Passes 0 when everything went ok, and -1 on error.
640 815
816 aio_msync $scalar, $offset = 0, $length = undef, flags = 0,
817 $callback->($status)
818 This is a rather advanced IO::AIO call, which only works on
819 mmap(2)ed scalars (see the "IO::AIO::mmap" function, although it
820 also works on data scalars managed by the Sys::Mmap or Mmap modules,
821 note that the scalar must only be modified in-place while an aio
822 operation is pending on it).
823
824 It calls the "msync" function of your OS, if available, with the
825 memory area starting at $offset in the string and ending $length
826 bytes later. If $length is negative, counts from the end, and if
827 $length is "undef", then it goes till the end of the string. The
828 flags can be a combination of "IO::AIO::MS_ASYNC",
829 "IO::AIO::MS_INVALIDATE" and "IO::AIO::MS_SYNC".
830
831 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0,
832 $callback->($status)
833 This is a rather advanced IO::AIO call, which works best on
834 mmap(2)ed scalars.
835
836 It touches (reads or writes) all memory pages in the specified range
837 inside the scalar. All caveats and parameters are the same as for
838 "aio_msync", above, except for flags, which must be either 0 (which
839 reads all pages and ensures they are instantiated) or
840 "IO::AIO::MT_MODIFY", which modifies the memory page s(by reading
841 and writing an octet from it, which dirties the page).
842
843 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
844 This is a rather advanced IO::AIO call, which works best on
845 mmap(2)ed scalars.
846
847 It reads in all the pages of the underlying storage into memory (if
848 any) and locks them, so they are not getting swapped/paged out or
849 removed.
850
851 If $length is undefined, then the scalar will be locked till the
852 end.
853
854 On systems that do not implement "mlock", this function returns -1
855 and sets errno to "ENOSYS".
856
857 Note that the corresponding "munlock" is synchronous and is
858 documented under "MISCELLANEOUS FUNCTIONS".
859
860 Example: open a file, mmap and mlock it - both will be undone when
861 $data gets destroyed.
862
863 open my $fh, "<", $path or die "$path: $!";
864 my $data;
865 IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
866 aio_mlock $data; # mlock in background
867
868 aio_mlockall $flags, $callback->($status)
869 Calls the "mlockall" function with the given $flags (a combination
870 of "IO::AIO::MCL_CURRENT" and "IO::AIO::MCL_FUTURE").
871
872 On systems that do not implement "mlockall", this function returns
873 -1 and sets errno to "ENOSYS".
874
875 Note that the corresponding "munlockall" is synchronous and is
876 documented under "MISCELLANEOUS FUNCTIONS".
877
878 Example: asynchronously lock all current and future pages into
879 memory.
880
881 aio_mlockall IO::AIO::MCL_FUTURE;
882
883 aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
884 Queries the extents of the given file (by calling the Linux FIEMAP
885 ioctl, see <http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for
886 details). If the "ioctl" is not available on your OS, then this
887 rquiest will fail with "ENOSYS".
888
889 $start is the starting offset to query extents for, $length is the
890 size of the range to query - if it is "undef", then the whole file
891 will be queried.
892
893 $flags is a combination of flags ("IO::AIO::FIEMAP_FLAG_SYNC" or
894 "IO::AIO::FIEMAP_FLAG_XATTR" - "IO::AIO::FIEMAP_FLAGS_COMPAT" is
895 also exported), and is normally 0 or "IO::AIO::FIEMAP_FLAG_SYNC" to
896 query the data portion.
897
898 $count is the maximum number of extent records to return. If it is
899 "undef", then IO::AIO queries all extents of the file. As a very
900 special case, if it is 0, then the callback receives the number of
901 extents instead of the extents themselves.
902
903 If an error occurs, the callback receives no arguments. The special
904 "errno" value "IO::AIO::EBADR" is available to test for flag errors.
905
906 Otherwise, the callback receives an array reference with extent
907 structures. Each extent structure is an array reference itself, with
908 the following members:
909
910 [$logical, $physical, $length, $flags]
911
912 Flags is any combination of the following flag values (typically
913 either 0 or "IO::AIO::FIEMAP_EXTENT_LAST"):
914
915 "IO::AIO::FIEMAP_EXTENT_LAST", "IO::AIO::FIEMAP_EXTENT_UNKNOWN",
916 "IO::AIO::FIEMAP_EXTENT_DELALLOC", "IO::AIO::FIEMAP_EXTENT_ENCODED",
917 "IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED",
918 "IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED",
919 "IO::AIO::FIEMAP_EXTENT_DATA_INLINE",
920 "IO::AIO::FIEMAP_EXTENT_DATA_TAIL",
921 "IO::AIO::FIEMAP_EXTENT_UNWRITTEN", "IO::AIO::FIEMAP_EXTENT_MERGED"
922 or "IO::AIO::FIEMAP_EXTENT_SHARED".
923
641 aio_group $callback->(...) 924 aio_group $callback->(...)
642 This is a very special aio request: Instead of doing something, it 925 This is a very special aio request: Instead of doing something, it
643 is a container for other aio requests, which is useful if you want 926 is a container for other aio requests, which is useful if you want
644 to bundle many requests into a single, composite, request with a 927 to bundle many requests into a single, composite, request with a
645 definite callback and the ability to cancel the whole request with 928 definite callback and the ability to cancel the whole request with
… …
678 While it is theoretically handy to have simple I/O scheduling 961 While it is theoretically handy to have simple I/O scheduling
679 requests like sleep and file handle readable/writable, the overhead 962 requests like sleep and file handle readable/writable, the overhead
680 this creates is immense (it blocks a thread for a long time) so do 963 this creates is immense (it blocks a thread for a long time) so do
681 not use this function except to put your application under 964 not use this function except to put your application under
682 artificial I/O pressure. 965 artificial I/O pressure.
966
967 IO::AIO::WD - multiple working directories
968 Your process only has one current working directory, which is used by
969 all threads. This makes it hard to use relative paths (some other
970 component could call "chdir" at any time, and it is hard to control when
971 the path will be used by IO::AIO).
972
973 One solution for this is to always use absolute paths. This usually
974 works, but can be quite slow (the kernel has to walk the whole path on
975 every access), and can also be a hassle to implement.
976
977 Newer POSIX systems have a number of functions (openat, fdopendir,
978 futimensat and so on) that make it possible to specify working
979 directories per operation.
980
981 For portability, and because the clowns who "designed", or shall I
982 write, perpetrated this new interface were obviously half-drunk, this
983 abstraction cannot be perfect, though.
984
985 IO::AIO allows you to convert directory paths into a so-called
986 IO::AIO::WD object. This object stores the canonicalised, absolute
987 version of the path, and on systems that allow it, also a directory file
988 descriptor.
989
990 Everywhere where a pathname is accepted by IO::AIO (e.g. in "aio_stat"
991 or "aio_unlink"), one can specify an array reference with an IO::AIO::WD
992 object and a pathname instead (or the IO::AIO::WD object alone, which
993 gets interpreted as "[$wd, "."]"). If the pathname is absolute, the
994 IO::AIO::WD object is ignored, otherwise the pathname is resolved
995 relative to that IO::AIO::WD object.
996
997 For example, to get a wd object for /etc and then stat passwd inside,
998 you would write:
999
1000 aio_wd "/etc", sub {
1001 my $etcdir = shift;
1002
1003 # although $etcdir can be undef on error, there is generally no reason
1004 # to check for errors here, as aio_stat will fail with ENOENT
1005 # when $etcdir is undef.
1006
1007 aio_stat [$etcdir, "passwd"], sub {
1008 # yay
1009 };
1010 };
1011
1012 That "aio_wd" is a request and not a normal function shows that creating
1013 an IO::AIO::WD object is itself a potentially blocking operation, which
1014 is why it is done asynchronously.
1015
1016 To stat the directory obtained with "aio_wd" above, one could write
1017 either of the following three request calls:
1018
1019 aio_lstat "/etc" , sub { ... # pathname as normal string
1020 aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
1021 aio_lstat $wd , sub { ... # shorthand for the previous
1022
1023 As with normal pathnames, IO::AIO keeps a copy of the working directory
1024 object and the pathname string, so you could write the following without
1025 causing any issues due to $path getting reused:
1026
1027 my $path = [$wd, undef];
1028
1029 for my $name (qw(abc def ghi)) {
1030 $path->[1] = $name;
1031 aio_stat $path, sub {
1032 # ...
1033 };
1034 }
1035
1036 There are some caveats: when directories get renamed (or deleted), the
1037 pathname string doesn't change, so will point to the new directory (or
1038 nowhere at all), while the directory fd, if available on the system,
1039 will still point to the original directory. Most functions accepting a
1040 pathname will use the directory fd on newer systems, and the string on
1041 older systems. Some functions (such as realpath) will always rely on the
1042 string form of the pathname.
1043
1044 So this fucntionality is mainly useful to get some protection against
1045 "chdir", to easily get an absolute path out of a relative path for
1046 future reference, and to speed up doing many operations in the same
1047 directory (e.g. when stat'ing all files in a directory).
1048
1049 The following functions implement this working directory abstraction:
1050
1051 aio_wd $pathname, $callback->($wd)
1052 Asynchonously canonicalise the given pathname and convert it to an
1053 IO::AIO::WD object representing it. If possible and supported on the
1054 system, also open a directory fd to speed up pathname resolution
1055 relative to this working directory.
1056
1057 If something goes wrong, then "undef" is passwd to the callback
1058 instead of a working directory object and $! is set appropriately.
1059 Since passing "undef" as working directory component of a pathname
1060 fails the request with "ENOENT", there is often no need for error
1061 checking in the "aio_wd" callback, as future requests using the
1062 value will fail in the expected way.
1063
1064 If this call isn't available because your OS lacks it or it couldn't
1065 be detected, it will be emulated by calling "fsync" instead.
1066
1067 IO::AIO::CWD
1068 This is a compiletime constant (object) that represents the process
1069 current working directory.
1070
1071 Specifying this object as working directory object for a pathname is
1072 as if the pathname would be specified directly, without a directory
1073 object, e.g., these calls are functionally identical:
1074
1075 aio_stat "somefile", sub { ... };
1076 aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
683 1077
684 IO::AIO::REQ CLASS 1078 IO::AIO::REQ CLASS
685 All non-aggregate "aio_*" functions return an object of this class when 1079 All non-aggregate "aio_*" functions return an object of this class when
686 called in non-void context. 1080 called in non-void context.
687 1081
… …
761 $grp->cancel_subs 1155 $grp->cancel_subs
762 Cancel all subrequests and clears any feeder, but not the group 1156 Cancel all subrequests and clears any feeder, but not the group
763 request itself. Useful when you queued a lot of events but got a 1157 request itself. Useful when you queued a lot of events but got a
764 result early. 1158 result early.
765 1159
1160 The group request will finish normally (you cannot add requests to
1161 the group).
1162
766 $grp->result (...) 1163 $grp->result (...)
767 Set the result value(s) that will be passed to the group callback 1164 Set the result value(s) that will be passed to the group callback
768 when all subrequests have finished and set the groups errno to the 1165 when all subrequests have finished and set the groups errno to the
769 current value of errno (just like calling "errno" without an error 1166 current value of errno (just like calling "errno" without an error
770 number). By default, no argument will be passed and errno is zero. 1167 number). By default, no argument will be passed and errno is zero.
… …
784 Sets a feeder/generator on this group: every group can have an 1181 Sets a feeder/generator on this group: every group can have an
785 attached generator that generates requests if idle. The idea behind 1182 attached generator that generates requests if idle. The idea behind
786 this is that, although you could just queue as many requests as you 1183 this is that, although you could just queue as many requests as you
787 want in a group, this might starve other requests for a potentially 1184 want in a group, this might starve other requests for a potentially
788 long time. For example, "aio_scandir" might generate hundreds of 1185 long time. For example, "aio_scandir" might generate hundreds of
789 thousands "aio_stat" requests, delaying any later requests for a 1186 thousands of "aio_stat" requests, delaying any later requests for a
790 long time. 1187 long time.
791 1188
792 To avoid this, and allow incremental generation of requests, you can 1189 To avoid this, and allow incremental generation of requests, you can
793 instead a group and set a feeder on it that generates those 1190 instead a group and set a feeder on it that generates those
794 requests. The feed callback will be called whenever there are few 1191 requests. The feed callback will be called whenever there are few
… …
837 1234
838 See "poll_cb" for an example. 1235 See "poll_cb" for an example.
839 1236
840 IO::AIO::poll_cb 1237 IO::AIO::poll_cb
841 Process some outstanding events on the result pipe. You have to call 1238 Process some outstanding events on the result pipe. You have to call
842 this regularly. Returns 0 if all events could be processed, or -1 if 1239 this regularly. Returns 0 if all events could be processed (or there
843 it returned earlier for whatever reason. Returns immediately when no 1240 were no events to process), or -1 if it returned earlier for
844 events are outstanding. The amount of events processed depends on 1241 whatever reason. Returns immediately when no events are outstanding.
845 the settings of "IO::AIO::max_poll_req" and 1242 The amount of events processed depends on the settings of
846 "IO::AIO::max_poll_time". 1243 "IO::AIO::max_poll_req" and "IO::AIO::max_poll_time".
847 1244
848 If not all requests were processed for whatever reason, the 1245 If not all requests were processed for whatever reason, the
849 filehandle will still be ready when "poll_cb" returns, so normally 1246 filehandle will still be ready when "poll_cb" returns, so normally
850 you don't have to do anything special to have it called later. 1247 you don't have to do anything special to have it called later.
851 1248
1249 Apart from calling "IO::AIO::poll_cb" when the event filehandle
1250 becomes ready, it can be beneficial to call this function from loops
1251 which submit a lot of requests, to make sure the results get
1252 processed when they become available and not just when the loop is
1253 finished and the event loop takes over again. This function returns
1254 very fast when there are no outstanding requests.
1255
852 Example: Install an Event watcher that automatically calls 1256 Example: Install an Event watcher that automatically calls
853 IO::AIO::poll_cb with high priority (more examples can be found in 1257 IO::AIO::poll_cb with high priority (more examples can be found in
854 the SYNOPSIS section, at the top of this document): 1258 the SYNOPSIS section, at the top of this document):
855 1259
856 Event->io (fd => IO::AIO::poll_fileno, 1260 Event->io (fd => IO::AIO::poll_fileno,
857 poll => 'r', async => 1, 1261 poll => 'r', async => 1,
858 cb => \&IO::AIO::poll_cb); 1262 cb => \&IO::AIO::poll_cb);
1263
1264 IO::AIO::poll_wait
1265 If there are any outstanding requests and none of them in the result
1266 phase, wait till the result filehandle becomes ready for reading
1267 (simply does a "select" on the filehandle. This is useful if you
1268 want to synchronously wait for some requests to finish).
1269
1270 See "nreqs" for an example.
1271
1272 IO::AIO::poll
1273 Waits until some requests have been handled.
1274
1275 Returns the number of requests processed, but is otherwise strictly
1276 equivalent to:
1277
1278 IO::AIO::poll_wait, IO::AIO::poll_cb
1279
1280 IO::AIO::flush
1281 Wait till all outstanding AIO requests have been handled.
1282
1283 Strictly equivalent to:
1284
1285 IO::AIO::poll_wait, IO::AIO::poll_cb
1286 while IO::AIO::nreqs;
859 1287
860 IO::AIO::max_poll_reqs $nreqs 1288 IO::AIO::max_poll_reqs $nreqs
861 IO::AIO::max_poll_time $seconds 1289 IO::AIO::max_poll_time $seconds
862 These set the maximum number of requests (default 0, meaning 1290 These set the maximum number of requests (default 0, meaning
863 infinity) that are being processed by "IO::AIO::poll_cb" in one 1291 infinity) that are being processed by "IO::AIO::poll_cb" in one
… …
887 # use a low priority so other tasks have priority 1315 # use a low priority so other tasks have priority
888 Event->io (fd => IO::AIO::poll_fileno, 1316 Event->io (fd => IO::AIO::poll_fileno,
889 poll => 'r', nice => 1, 1317 poll => 'r', nice => 1,
890 cb => &IO::AIO::poll_cb); 1318 cb => &IO::AIO::poll_cb);
891 1319
892 IO::AIO::poll_wait
893 If there are any outstanding requests and none of them in the result
894 phase, wait till the result filehandle becomes ready for reading
895 (simply does a "select" on the filehandle. This is useful if you
896 want to synchronously wait for some requests to finish).
897
898 See "nreqs" for an example.
899
900 IO::AIO::poll
901 Waits until some requests have been handled.
902
903 Returns the number of requests processed, but is otherwise strictly
904 equivalent to:
905
906 IO::AIO::poll_wait, IO::AIO::poll_cb
907
908 IO::AIO::flush
909 Wait till all outstanding AIO requests have been handled.
910
911 Strictly equivalent to:
912
913 IO::AIO::poll_wait, IO::AIO::poll_cb
914 while IO::AIO::nreqs;
915
916 CONTROLLING THE NUMBER OF THREADS 1320 CONTROLLING THE NUMBER OF THREADS
917 IO::AIO::min_parallel $nthreads 1321 IO::AIO::min_parallel $nthreads
918 Set the minimum number of AIO threads to $nthreads. The current 1322 Set the minimum number of AIO threads to $nthreads. The current
919 default is 8, which means eight asynchronous operations can execute 1323 default is 8, which means eight asynchronous operations can execute
920 concurrently at any one time (the number of outstanding requests, 1324 concurrently at any one time (the number of outstanding requests,
… …
949 1353
950 Under normal circumstances you don't need to call this function. 1354 Under normal circumstances you don't need to call this function.
951 1355
952 IO::AIO::max_idle $nthreads 1356 IO::AIO::max_idle $nthreads
953 Limit the number of threads (default: 4) that are allowed to idle 1357 Limit the number of threads (default: 4) that are allowed to idle
954 (i.e., threads that did not get a request to process within 10 1358 (i.e., threads that did not get a request to process within the idle
955 seconds). That means if a thread becomes idle while $nthreads other 1359 timeout (default: 10 seconds). That means if a thread becomes idle
956 threads are also idle, it will free its resources and exit. 1360 while $nthreads other threads are also idle, it will free its
1361 resources and exit.
957 1362
958 This is useful when you allow a large number of threads (e.g. 100 or 1363 This is useful when you allow a large number of threads (e.g. 100 or
959 1000) to allow for extremely high load situations, but want to free 1364 1000) to allow for extremely high load situations, but want to free
960 resources under normal circumstances (1000 threads can easily 1365 resources under normal circumstances (1000 threads can easily
961 consume 30MB of RAM). 1366 consume 30MB of RAM).
962 1367
963 The default is probably ok in most situations, especially if thread 1368 The default is probably ok in most situations, especially if thread
964 creation is fast. If thread creation is very slow on your system you 1369 creation is fast. If thread creation is very slow on your system you
965 might want to use larger values. 1370 might want to use larger values.
966 1371
1372 IO::AIO::idle_timeout $seconds
1373 Sets the minimum idle timeout (default 10) after which worker
1374 threads are allowed to exit. SEe "IO::AIO::max_idle".
1375
967 IO::AIO::max_outstanding $maxreqs 1376 IO::AIO::max_outstanding $maxreqs
1377 Sets the maximum number of outstanding requests to $nreqs. If you do
1378 queue up more than this number of requests, the next call to
1379 "IO::AIO::poll_cb" (and other functions calling "poll_cb", such as
1380 "IO::AIO::flush" or "IO::AIO::poll") will block until the limit is
1381 no longer exceeded.
1382
1383 In other words, this setting does not enforce a queue limit, but can
1384 be used to make poll functions block if the limit is exceeded.
1385
968 This is a very bad function to use in interactive programs because 1386 This is a very bad function to use in interactive programs because
969 it blocks, and a bad way to reduce concurrency because it is 1387 it blocks, and a bad way to reduce concurrency because it is
970 inexact: Better use an "aio_group" together with a feed callback. 1388 inexact: Better use an "aio_group" together with a feed callback.
971 1389
972 Sets the maximum number of outstanding requests to $nreqs. If you do 1390 It's main use is in scripts without an event loop - when you want to
973 queue up more than this number of requests, the next call to the 1391 stat a lot of files, you can write somehting like this:
974 "poll_cb" (and "poll_some" and other functions calling "poll_cb")
975 function will block until the limit is no longer exceeded.
976 1392
977 The default value is very large, so there is no practical limit on 1393 IO::AIO::max_outstanding 32;
1394
1395 for my $path (...) {
1396 aio_stat $path , ...;
1397 IO::AIO::poll_cb;
1398 }
1399
1400 IO::AIO::flush;
1401
1402 The call to "poll_cb" inside the loop will normally return
1403 instantly, but as soon as more thna 32 reqeusts are in-flight, it
1404 will block until some requests have been handled. This keeps the
1405 loop from pushing a large number of "aio_stat" requests onto the
1406 queue.
1407
1408 The default value for "max_outstanding" is very large, so there is
978 the number of outstanding requests. 1409 no practical limit on the number of outstanding requests.
979
980 You can still queue as many requests as you want. Therefore,
981 "max_outstanding" is mainly useful in simple scripts (with low
982 values) or as a stop gap to shield against fatal memory overflow
983 (with large values).
984 1410
985 STATISTICAL INFORMATION 1411 STATISTICAL INFORMATION
986 IO::AIO::nreqs 1412 IO::AIO::nreqs
987 Returns the number of requests currently in the ready, execute or 1413 Returns the number of requests currently in the ready, execute or
988 pending states (i.e. for which their callback has not been invoked 1414 pending states (i.e. for which their callback has not been invoked
… …
1012 set to non-blocking operations). 1438 set to non-blocking operations).
1013 1439
1014 Returns the number of bytes copied, or -1 on error. 1440 Returns the number of bytes copied, or -1 on error.
1015 1441
1016 IO::AIO::fadvise $fh, $offset, $len, $advice 1442 IO::AIO::fadvise $fh, $offset, $len, $advice
1017 Simply calls the "posix_fadvise" function (see it's manpage for 1443 Simply calls the "posix_fadvise" function (see its manpage for
1018 details). The following advice constants are avaiable: 1444 details). The following advice constants are available:
1019 "IO::AIO::FADV_NORMAL", "IO::AIO::FADV_SEQUENTIAL", 1445 "IO::AIO::FADV_NORMAL", "IO::AIO::FADV_SEQUENTIAL",
1020 "IO::AIO::FADV_RANDOM", "IO::AIO::FADV_NOREUSE", 1446 "IO::AIO::FADV_RANDOM", "IO::AIO::FADV_NOREUSE",
1021 "IO::AIO::FADV_WILLNEED", "IO::AIO::FADV_DONTNEED". 1447 "IO::AIO::FADV_WILLNEED", "IO::AIO::FADV_DONTNEED".
1022 1448
1023 On systems that do not implement "posix_fadvise", this function 1449 On systems that do not implement "posix_fadvise", this function
1024 returns ENOSYS, otherwise the return value of "posix_fadvise". 1450 returns ENOSYS, otherwise the return value of "posix_fadvise".
1025 1451
1452 IO::AIO::madvise $scalar, $offset, $len, $advice
1453 Simply calls the "posix_madvise" function (see its manpage for
1454 details). The following advice constants are available:
1455 "IO::AIO::MADV_NORMAL", "IO::AIO::MADV_SEQUENTIAL",
1456 "IO::AIO::MADV_RANDOM", "IO::AIO::MADV_WILLNEED",
1457 "IO::AIO::MADV_DONTNEED".
1458
1459 On systems that do not implement "posix_madvise", this function
1460 returns ENOSYS, otherwise the return value of "posix_madvise".
1461
1462 IO::AIO::mprotect $scalar, $offset, $len, $protect
1463 Simply calls the "mprotect" function on the preferably AIO::mmap'ed
1464 $scalar (see its manpage for details). The following protect
1465 constants are available: "IO::AIO::PROT_NONE", "IO::AIO::PROT_READ",
1466 "IO::AIO::PROT_WRITE", "IO::AIO::PROT_EXEC".
1467
1468 On systems that do not implement "mprotect", this function returns
1469 ENOSYS, otherwise the return value of "mprotect".
1470
1471 IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
1472 Memory-maps a file (or anonymous memory range) and attaches it to
1473 the given $scalar, which will act like a string scalar.
1474
1475 The only operations allowed on the scalar are "substr"/"vec" that
1476 don't change the string length, and most read-only operations such
1477 as copying it or searching it with regexes and so on.
1478
1479 Anything else is unsafe and will, at best, result in memory leaks.
1480
1481 The memory map associated with the $scalar is automatically removed
1482 when the $scalar is destroyed, or when the "IO::AIO::mmap" or
1483 "IO::AIO::munmap" functions are called.
1484
1485 This calls the "mmap"(2) function internally. See your system's
1486 manual page for details on the $length, $prot and $flags parameters.
1487
1488 The $length must be larger than zero and smaller than the actual
1489 filesize.
1490
1491 $prot is a combination of "IO::AIO::PROT_NONE",
1492 "IO::AIO::PROT_EXEC", "IO::AIO::PROT_READ" and/or
1493 "IO::AIO::PROT_WRITE",
1494
1495 $flags can be a combination of "IO::AIO::MAP_SHARED" or
1496 "IO::AIO::MAP_PRIVATE", or a number of system-specific flags (when
1497 not available, the are defined as 0): "IO::AIO::MAP_ANONYMOUS"
1498 (which is set to "MAP_ANON" if your system only provides this
1499 constant), "IO::AIO::MAP_HUGETLB", "IO::AIO::MAP_LOCKED",
1500 "IO::AIO::MAP_NORESERVE", "IO::AIO::MAP_POPULATE" or
1501 "IO::AIO::MAP_NONBLOCK"
1502
1503 If $fh is "undef", then a file descriptor of -1 is passed.
1504
1505 $offset is the offset from the start of the file - it generally must
1506 be a multiple of "IO::AIO::PAGESIZE" and defaults to 0.
1507
1508 Example:
1509
1510 use Digest::MD5;
1511 use IO::AIO;
1512
1513 open my $fh, "<verybigfile"
1514 or die "$!";
1515
1516 IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
1517 or die "verybigfile: $!";
1518
1519 my $fast_md5 = md5 $data;
1520
1521 IO::AIO::munmap $scalar
1522 Removes a previous mmap and undefines the $scalar.
1523
1524 IO::AIO::munlock $scalar, $offset = 0, $length = undef
1525 Calls the "munlock" function, undoing the effects of a previous
1526 "aio_mlock" call (see its description for details).
1527
1528 IO::AIO::munlockall
1529 Calls the "munlockall" function.
1530
1531 On systems that do not implement "munlockall", this function returns
1532 ENOSYS, otherwise the return value of "munlockall".
1533
1534EVENT LOOP INTEGRATION
1535 It is recommended to use AnyEvent::AIO to integrate IO::AIO
1536 automatically into many event loops:
1537
1538 # AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
1539 use AnyEvent::AIO;
1540
1541 You can also integrate IO::AIO manually into many event loops, here are
1542 some examples of how to do this:
1543
1544 # EV integration
1545 my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
1546
1547 # Event integration
1548 Event->io (fd => IO::AIO::poll_fileno,
1549 poll => 'r',
1550 cb => \&IO::AIO::poll_cb);
1551
1552 # Glib/Gtk2 integration
1553 add_watch Glib::IO IO::AIO::poll_fileno,
1554 in => sub { IO::AIO::poll_cb; 1 };
1555
1556 # Tk integration
1557 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
1558 readable => \&IO::AIO::poll_cb);
1559
1560 # Danga::Socket integration
1561 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
1562 \&IO::AIO::poll_cb);
1563
1026 FORK BEHAVIOUR 1564 FORK BEHAVIOUR
1027 This module should do "the right thing" when the process using it forks: 1565 Usage of pthreads in a program changes the semantics of fork
1566 considerably. Specifically, only async-safe functions can be called
1567 after fork. Perl doesn't know about this, so in general, you cannot call
1568 fork with defined behaviour in perl if pthreads are involved. IO::AIO
1569 uses pthreads, so this applies, but many other extensions and (for
1570 inexplicable reasons) perl itself often is linked against pthreads, so
1571 this limitation applies to quite a lot of perls.
1028 1572
1029 Before the fork, IO::AIO enters a quiescent state where no requests can 1573 This module no longer tries to fight your OS, or POSIX. That means
1030 be added in other threads and no results will be processed. After the 1574 IO::AIO only works in the process that loaded it. Forking is fully
1031 fork the parent simply leaves the quiescent state and continues 1575 supported, but using IO::AIO in the child is not.
1032 request/result processing, while the child frees the request/result
1033 queue (so that the requests started before the fork will only be handled
1034 in the parent). Threads will be started on demand until the limit set in
1035 the parent process has been reached again.
1036 1576
1037 In short: the parent will, after a short pause, continue as if fork had 1577 You might get around by not *using* IO::AIO before (or after) forking.
1038 not been called, while the child will act as if IO::AIO has not been 1578 You could also try to call the IO::AIO::reinit function in the child:
1039 used yet. 1579
1580 IO::AIO::reinit
1581 Abandons all current requests and I/O threads and simply
1582 reinitialises all data structures. This is not an operation
1583 supported by any standards, but happens to work on GNU/Linux and
1584 some newer BSD systems.
1585
1586 The only reasonable use for this function is to call it after
1587 forking, if "IO::AIO" was used in the parent. Calling it while
1588 IO::AIO is active in the process will result in undefined behaviour.
1589 Calling it at any time will also result in any undefined (by POSIX)
1590 behaviour.
1040 1591
1041 MEMORY USAGE 1592 MEMORY USAGE
1042 Per-request usage: 1593 Per-request usage:
1043 1594
1044 Each aio request uses - depending on your architecture - around 100-200 1595 Each aio request uses - depending on your architecture - around 100-200

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