ViewVC Help
View File | Revision Log | Show Annotations | Download File
/cvs/IO-AIO/README
(Generate patch)

Comparing IO-AIO/README (file contents):
Revision 1.43 by root, Sun Jan 10 23:44:02 2010 UTC vs.
Revision 1.51 by root, Sat Apr 7 00:50:33 2012 UTC

… …
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
… …
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;
… …
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)
158 aio_seek $fh,$offset,$whence, $callback->($offs)
157 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval) 159 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
158 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval) 160 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
159 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval) 161 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
160 aio_readahead $fh,$offset,$length, $callback->($retval) 162 aio_readahead $fh,$offset,$length, $callback->($retval)
161 aio_stat $fh_or_path, $callback->($status) 163 aio_stat $fh_or_path, $callback->($status)
162 aio_lstat $fh, $callback->($status) 164 aio_lstat $fh, $callback->($status)
163 aio_statvfs $fh_or_path, $callback->($statvfs) 165 aio_statvfs $fh_or_path, $callback->($statvfs)
164 aio_utime $fh_or_path, $atime, $mtime, $callback->($status) 166 aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
165 aio_chown $fh_or_path, $uid, $gid, $callback->($status) 167 aio_chown $fh_or_path, $uid, $gid, $callback->($status)
168 aio_chmod $fh_or_path, $mode, $callback->($status)
166 aio_truncate $fh_or_path, $offset, $callback->($status) 169 aio_truncate $fh_or_path, $offset, $callback->($status)
167 aio_chmod $fh_or_path, $mode, $callback->($status)
168 aio_unlink $pathname, $callback->($status) 170 aio_unlink $pathname, $callback->($status)
169 aio_mknod $path, $mode, $dev, $callback->($status) 171 aio_mknod $pathname, $mode, $dev, $callback->($status)
170 aio_link $srcpath, $dstpath, $callback->($status) 172 aio_link $srcpath, $dstpath, $callback->($status)
171 aio_symlink $srcpath, $dstpath, $callback->($status) 173 aio_symlink $srcpath, $dstpath, $callback->($status)
172 aio_readlink $path, $callback->($link) 174 aio_readlink $pathname, $callback->($link)
175 aio_realpath $pathname, $callback->($link)
173 aio_rename $srcpath, $dstpath, $callback->($status) 176 aio_rename $srcpath, $dstpath, $callback->($status)
174 aio_mkdir $pathname, $mode, $callback->($status) 177 aio_mkdir $pathname, $mode, $callback->($status)
175 aio_rmdir $pathname, $callback->($status) 178 aio_rmdir $pathname, $callback->($status)
176 aio_readdir $pathname, $callback->($entries) 179 aio_readdir $pathname, $callback->($entries)
177 aio_readdirx $pathname, $flags, $callback->($entries, $flags) 180 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
178 IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST 181 IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
179 IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN 182 IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
183 aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
180 aio_load $path, $data, $callback->($status) 184 aio_load $pathname, $data, $callback->($status)
181 aio_copy $srcpath, $dstpath, $callback->($status) 185 aio_copy $srcpath, $dstpath, $callback->($status)
182 aio_move $srcpath, $dstpath, $callback->($status) 186 aio_move $srcpath, $dstpath, $callback->($status)
183 aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
184 aio_rmtree $path, $callback->($status) 187 aio_rmtree $pathname, $callback->($status)
185 aio_sync $callback->($status) 188 aio_sync $callback->($status)
189 aio_syncfs $fh, $callback->($status)
186 aio_fsync $fh, $callback->($status) 190 aio_fsync $fh, $callback->($status)
187 aio_fdatasync $fh, $callback->($status) 191 aio_fdatasync $fh, $callback->($status)
188 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status) 192 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
189 aio_pathsync $path, $callback->($status) 193 aio_pathsync $pathname, $callback->($status)
190 aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status) 194 aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
191 aio_mtouch $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)
192 aio_group $callback->(...) 198 aio_group $callback->(...)
193 aio_nop $callback->() 199 aio_nop $callback->()
194 200
195 $prev_pri = aioreq_pri [$pri] 201 $prev_pri = aioreq_pri [$pri]
196 aioreq_nice $pri_adjust 202 aioreq_nice $pri_adjust
… …
202 IO::AIO::max_poll_reqs $nreqs 208 IO::AIO::max_poll_reqs $nreqs
203 IO::AIO::max_poll_time $seconds 209 IO::AIO::max_poll_time $seconds
204 IO::AIO::min_parallel $nthreads 210 IO::AIO::min_parallel $nthreads
205 IO::AIO::max_parallel $nthreads 211 IO::AIO::max_parallel $nthreads
206 IO::AIO::max_idle $nthreads 212 IO::AIO::max_idle $nthreads
213 IO::AIO::idle_timeout $seconds
207 IO::AIO::max_outstanding $maxreqs 214 IO::AIO::max_outstanding $maxreqs
208 IO::AIO::nreqs 215 IO::AIO::nreqs
209 IO::AIO::nready 216 IO::AIO::nready
210 IO::AIO::npending 217 IO::AIO::npending
211 218
212 IO::AIO::sendfile $ofh, $ifh, $offset, $count 219 IO::AIO::sendfile $ofh, $ifh, $offset, $count
213 IO::AIO::fadvise $fh, $offset, $len, $advice 220 IO::AIO::fadvise $fh, $offset, $len, $advice
214 IO::AIO::mlockall $flags 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
215 IO::AIO::munlockall 224 IO::AIO::munlockall
216 225
217 AIO REQUEST FUNCTIONS 226 API NOTES
218 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
219 with the same name (sans "aio_"). The arguments are similar or 228 with the same name (sans "aio_"). The arguments are similar or
220 identical, and they all accept an additional (and optional) $callback 229 identical, and they all accept an additional (and optional) $callback
221 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
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. 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".
225 239
226 All functions expecting a filehandle keep a copy of the filehandle 240 All functions expecting a filehandle keep a copy of the filehandle
227 internally until the request has finished. 241 internally until the request has finished.
228 242
229 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
230 further manipulation of those requests while they are in-flight. 244 further manipulation of those requests while they are in-flight.
231 245
232 The pathnames you pass to these routines *must* be absolute and encoded 246 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 247 reason for this is that at the time the request is being executed, the
234 being executed, the current working directory could have changed. 248 current working directory could have changed. Alternatively, you can
235 Alternatively, you can make sure that you never change the current 249 make sure that you never change the current working directory anywhere
236 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.
237 254
238 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
239 pass in filenames you got from outside (command line, readdir etc.) 256 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 257 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 258 Encode module and encode your pathnames to the locale (or other)
242 the user environment, d) use Glib::filename_from_unicode on unicode 259 encoding in effect in the user environment, d) use
243 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
244 contents. 261 else to ensure your scalar has the correct contents.
245 262
246 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
247 handles correctly whether it is set or not. 264 handles correctly whether it is set or not.
248 265
266 AIO REQUEST FUNCTIONS
249 $prev_pri = aioreq_pri [$pri] 267 $prev_pri = aioreq_pri [$pri]
250 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
251 and, if $pri is given, sets the priority for the next aio request. 269 and, if $pri is given, sets the priority for the next aio request.
252 270
253 The default priority is 0, the minimum and maximum priorities are -4 271 The default priority is 0, the minimum and maximum priorities are -4
… …
292 will be modified by the umask in effect then the request is being 310 will be modified by the umask in effect then the request is being
293 executed, so better never change the umask. 311 executed, so better never change the umask.
294 312
295 Example: 313 Example:
296 314
297 aio_open "/etc/passwd", O_RDONLY, 0, sub { 315 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
298 if ($_[0]) { 316 if ($_[0]) {
299 print "open successful, fh is $_[0]\n"; 317 print "open successful, fh is $_[0]\n";
300 ... 318 ...
301 } else { 319 } else {
302 die "open failed: $!\n"; 320 die "open failed: $!\n";
303 } 321 }
304 }; 322 };
305 323
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
306 aio_close $fh, $callback->($status) 333 aio_close $fh, $callback->($status)
307 Asynchronously close a file and call the callback with the result 334 Asynchronously close a file and call the callback with the result
308 code. 335 code.
309 336
310 Unfortunately, you can't do this to perl. Perl *insists* very 337 Unfortunately, you can't do this to perl. Perl *insists* very
… …
315 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
316 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).
317 344
318 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
319 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.
320 360
321 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval) 361 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
322 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval) 362 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
323 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
324 $offset into the scalar given by $data and offset $dataoffset and 364 $offset into the scalar given by $data and offset $dataoffset and
… …
353 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval) 393 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 394 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 395 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 396 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 397 more than one "aio_sendfile" per $out_fh, as they will interfere
358 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.
359 400
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
360 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
361 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
362 to a socket, and $in_fh should refer to an mmap'able file. 420 to a socket, and $in_fh should refer to an mmap'able file.
363 421
364 If a native sendfile cannot be found or it fails with "ENOSYS", 422 If a native sendfile cannot be found or it fails with "ENOSYS",
365 "ENOTSUP", "EOPNOTSUPP", "EAFNOSUPPORT", "EPROTOTYPE" or "ENOTSOCK", 423 "EINVAL", "ENOTSUP", "EOPNOTSUPP", "EAFNOSUPPORT", "EPROTOTYPE" or
366 it will be emulated, so you can call "aio_sendfile" on any type of 424 "ENOTSOCK", it will be emulated, so you can call "aio_sendfile" on
367 filehandle regardless of the limitations of the operating system. 425 any type of filehandle regardless of the limitations of the
426 operating system.
368 427
369 Please note, however, that "aio_sendfile" can read more bytes from 428 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 429 hacked together in a hurry to improve benchmark numbers) tend to be
371 bytes have been read from "aio_sendfile" alone, as "aio_sendfile" 430 rather buggy on many systems, this implementation tries to work
372 only provides the number of bytes written to $out_fh. Only if the 431 around some known bugs in Linux and FreeBSD kernels (probably
373 result value equals $length one can assume that $length bytes have 432 others, too), but that might fail, so you really really should check
374 been read. 433 the return value of "aio_sendfile" - fewre bytes than expected might
434 have been transferred.
375 435
376 aio_readahead $fh,$offset,$length, $callback->($retval) 436 aio_readahead $fh,$offset,$length, $callback->($retval)
377 "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
378 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
379 $offset argument specifies the starting point from which data is to 439 $offset argument specifies the starting point from which data is to
… …
399 459
400 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
401 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
402 silently truncated unless perl itself is compiled with large file 462 silently truncated unless perl itself is compiled with large file
403 support. 463 support.
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".
404 473
405 Example: Print the length of /etc/passwd: 474 Example: Print the length of /etc/passwd:
406 475
407 aio_stat "/etc/passwd", sub { 476 aio_stat "/etc/passwd", sub {
408 $_[0] and die "stat failed: $!"; 477 $_[0] and die "stat failed: $!";
… …
488 557
489 aio_unlink $pathname, $callback->($status) 558 aio_unlink $pathname, $callback->($status)
490 Asynchronously unlink (delete) a file and call the callback with the 559 Asynchronously unlink (delete) a file and call the callback with the
491 result code. 560 result code.
492 561
493 aio_mknod $path, $mode, $dev, $callback->($status) 562 aio_mknod $pathname, $mode, $dev, $callback->($status)
494 [EXPERIMENTAL] 563 [EXPERIMENTAL]
495 564
496 Asynchronously create a device node (or fifo). See mknod(2). 565 Asynchronously create a device node (or fifo). See mknod(2).
497 566
498 The only (POSIX-) portable way of calling this function is: 567 The only (POSIX-) portable way of calling this function is:
499 568
500 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.
501 573
502 aio_link $srcpath, $dstpath, $callback->($status) 574 aio_link $srcpath, $dstpath, $callback->($status)
503 Asynchronously create a new link to the existing object at $srcpath 575 Asynchronously create a new link to the existing object at $srcpath
504 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.
505 577
506 aio_symlink $srcpath, $dstpath, $callback->($status) 578 aio_symlink $srcpath, $dstpath, $callback->($status)
507 Asynchronously create a new symbolic link to the existing object at 579 Asynchronously create a new symbolic link to the existing object at
508 $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
509 code. 581 code.
510 582
511 aio_readlink $path, $callback->($link) 583 aio_readlink $pathname, $callback->($link)
512 Asynchronously read the symlink specified by $path and pass it to 584 Asynchronously read the symlink specified by $path and pass it to
513 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
514 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).
515 595
516 aio_rename $srcpath, $dstpath, $callback->($status) 596 aio_rename $srcpath, $dstpath, $callback->($status)
517 Asynchronously rename the object at $srcpath to $dstpath, just as 597 Asynchronously rename the object at $srcpath to $dstpath, just as
518 rename(2) and call the callback with the result code. 598 rename(2) and call the callback with the result code.
519 599
… …
533 613
534 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
535 an array-ref with the filenames. 615 an array-ref with the filenames.
536 616
537 aio_readdirx $pathname, $flags, $callback->($entries, $flags) 617 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
538 Quite similar to "aio_readdir", but the $flags argument allows to 618 Quite similar to "aio_readdir", but the $flags argument allows one
539 tune behaviour and output format. In case of an error, $entries will 619 to tune behaviour and output format. In case of an error, $entries
540 be "undef". 620 will be "undef".
541 621
542 The flags are a combination of the following constants, ORed 622 The flags are a combination of the following constants, ORed
543 together (the flags will also be passed to the callback, possibly 623 together (the flags will also be passed to the callback, possibly
544 modified): 624 modified):
545 625
546 IO::AIO::READDIR_DENTS 626 IO::AIO::READDIR_DENTS
547 When this flag is off, then the callback gets an arrayref with 627 When this flag is off, then the callback gets an arrayref
548 of names only (as with "aio_readdir"), otherwise it gets an 628 consisting of names only (as with "aio_readdir"), otherwise it
549 arrayref with "[$name, $type, $inode]" arrayrefs, each 629 gets an arrayref with "[$name, $type, $inode]" arrayrefs, each
550 describing a single directory entry in more detail. 630 describing a single directory entry in more detail.
551 631
552 $name is the name of the entry. 632 $name is the name of the entry.
553 633
554 $type is one of the "IO::AIO::DT_xxx" constants: 634 $type is one of the "IO::AIO::DT_xxx" constants:
… …
567 unspecified content on systems that do not deliver the inode 647 unspecified content on systems that do not deliver the inode
568 information. 648 information.
569 649
570 IO::AIO::READDIR_DIRS_FIRST 650 IO::AIO::READDIR_DIRS_FIRST
571 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
572 order where likely directories come first. This is useful when 652 order where likely directories come first, in optimal stat
573 you need to quickly find directories, or you want to find all 653 order. This is useful when you need to quickly find directories,
574 directories while avoiding to stat() each entry. 654 or you want to find all directories while avoiding to stat()
655 each entry.
575 656
576 If the system returns type information in readdir, then this is 657 If the system returns type information in readdir, then this is
577 used to find directories directly. Otherwise, likely directories 658 used to find directories directly. Otherwise, likely directories
578 are files beginning with ".", or otherwise files with no dots, 659 are names beginning with ".", or otherwise names with no dots,
579 of which files with short names are tried first. 660 of which names with short names are tried first.
580 661
581 IO::AIO::READDIR_STAT_ORDER 662 IO::AIO::READDIR_STAT_ORDER
582 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
583 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
584 to stat() all files in the given directory, then the returned 665 to stat() all files in the given directory, then the returned
… …
589 optimal stat order. 670 optimal stat order.
590 671
591 IO::AIO::READDIR_FOUND_UNKNOWN 672 IO::AIO::READDIR_FOUND_UNKNOWN
592 This flag should not be set when calling "aio_readdirx". 673 This flag should not be set when calling "aio_readdirx".
593 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
594 $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
595 flag therefore indicates that all $type's are known, which can 676 flag therefore indicates that all $type's are known, which can
596 be used to speed up some algorithms. 677 be used to speed up some algorithms.
597 678
598 aio_load $path, $data, $callback->($status) 679 aio_load $pathname, $data, $callback->($status)
599 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
600 into memory. Status is the same as with aio_read. 681 into memory. Status is the same as with aio_read.
601 682
602 aio_copy $srcpath, $dstpath, $callback->($status) 683 aio_copy $srcpath, $dstpath, $callback->($status)
603 Try to copy the *file* (directories not supported as either source 684 Try to copy the *file* (directories not supported as either source
… …
620 701
621 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;
622 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"
623 and, if that is successful, unlinks the $srcpath. 704 and, if that is successful, unlinks the $srcpath.
624 705
625 aio_scandir $path, $maxreq, $callback->($dirs, $nondirs) 706 aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
626 Scans a directory (similar to "aio_readdir") but additionally tries 707 Scans a directory (similar to "aio_readdir") but additionally tries
627 to efficiently separate the entries of directory $path into two sets 708 to efficiently separate the entries of directory $path into two sets
628 of names, directories you can recurse into (directories), and ones 709 of names, directories you can recurse into (directories), and ones
629 you cannot recurse into (everything else, including symlinks to 710 you cannot recurse into (everything else, including symlinks to
630 directories). 711 directories).
… …
663 Then entries will be sorted into likely directories a non-initial 744 Then entries will be sorted into likely directories a non-initial
664 dot currently) and likely non-directories (see "aio_readdirx"). Then 745 dot currently) and likely non-directories (see "aio_readdirx"). Then
665 every entry plus an appended "/." will be "stat"'ed, likely 746 every entry plus an appended "/." will be "stat"'ed, likely
666 directories first, in order of their inode numbers. If that 747 directories first, in order of their inode numbers. If that
667 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
668 directory (which will be checked seperately). This is often faster 749 directory (which will be checked separately). This is often faster
669 than stat'ing the entry itself because filesystems might detect the 750 than stat'ing the entry itself because filesystems might detect the
670 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
671 filetype feature), even on systems that cannot return the filetype 752 filetype feature), even on systems that cannot return the filetype
672 information on readdir. 753 information on readdir.
673 754
… …
679 760
680 It will also likely work on non-POSIX filesystems with reduced 761 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 762 efficiency as those tend to return 0 or 1 as link counts, which
682 disables the directory counting heuristic. 763 disables the directory counting heuristic.
683 764
684 aio_rmtree $path, $callback->($status) 765 aio_rmtree $pathname, $callback->($status)
685 Delete a directory tree starting (and including) $path, return the 766 Delete a directory tree starting (and including) $path, return the
686 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
687 uses "aio_scandir" to recurse into and rmdir directories, and unlink 768 uses "aio_scandir" to recurse into and rmdir directories, and unlink
688 everything else. 769 everything else.
689 770
… …
698 Asynchronously call fdatasync on the given filehandle and call the 779 Asynchronously call fdatasync on the given filehandle and call the
699 callback with the fdatasync result code. 780 callback with the fdatasync result code.
700 781
701 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
702 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.
703 790
704 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status) 791 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
705 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
706 to disk (but NOT the metadata), by calling the Linux-specific 793 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 794 sync_file_range call. If sync_file_range is not available or it
… …
711 "IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE", 798 "IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE",
712 "IO::AIO::SYNC_FILE_RANGE_WRITE" and 799 "IO::AIO::SYNC_FILE_RANGE_WRITE" and
713 "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
714 manpage for details. 801 manpage for details.
715 802
716 aio_pathsync $path, $callback->($status) 803 aio_pathsync $pathname, $callback->($status)
717 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
718 a composite request intended to sync directories after directory 805 a composite request intended to sync directories after directory
719 operations (E.g. rename). This might not work on all operating 806 operations (E.g. rename). This might not work on all operating
720 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
721 directory changes get written to disc. It works for anything that 808 directory changes get written to disc. It works for anything that
… …
751 "aio_msync", above, except for flags, which must be either 0 (which 838 "aio_msync", above, except for flags, which must be either 0 (which
752 reads all pages and ensures they are instantiated) or 839 reads all pages and ensures they are instantiated) or
753 "IO::AIO::MT_MODIFY", which modifies the memory page s(by reading 840 "IO::AIO::MT_MODIFY", which modifies the memory page s(by reading
754 and writing an octet from it, which dirties the page). 841 and writing an octet from it, which dirties the page).
755 842
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
756 aio_group $callback->(...) 924 aio_group $callback->(...)
757 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
758 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
759 to bundle many requests into a single, composite, request with a 927 to bundle many requests into a single, composite, request with a
760 definite callback and the ability to cancel the whole request with 928 definite callback and the ability to cancel the whole request with
… …
793 While it is theoretically handy to have simple I/O scheduling 961 While it is theoretically handy to have simple I/O scheduling
794 requests like sleep and file handle readable/writable, the overhead 962 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 963 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 964 not use this function except to put your application under
797 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 { ... };
798 1077
799 IO::AIO::REQ CLASS 1078 IO::AIO::REQ CLASS
800 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
801 called in non-void context. 1080 called in non-void context.
802 1081
… …
902 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
903 attached generator that generates requests if idle. The idea behind 1182 attached generator that generates requests if idle. The idea behind
904 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
905 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
906 long time. For example, "aio_scandir" might generate hundreds of 1185 long time. For example, "aio_scandir" might generate hundreds of
907 thousands "aio_stat" requests, delaying any later requests for a 1186 thousands of "aio_stat" requests, delaying any later requests for a
908 long time. 1187 long time.
909 1188
910 To avoid this, and allow incremental generation of requests, you can 1189 To avoid this, and allow incremental generation of requests, you can
911 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
912 requests. The feed callback will be called whenever there are few 1191 requests. The feed callback will be called whenever there are few
… …
955 1234
956 See "poll_cb" for an example. 1235 See "poll_cb" for an example.
957 1236
958 IO::AIO::poll_cb 1237 IO::AIO::poll_cb
959 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
960 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
961 it returned earlier for whatever reason. Returns immediately when no 1240 were no events to process), or -1 if it returned earlier for
962 events are outstanding. The amount of events processed depends on 1241 whatever reason. Returns immediately when no events are outstanding.
963 the settings of "IO::AIO::max_poll_req" and 1242 The amount of events processed depends on the settings of
964 "IO::AIO::max_poll_time". 1243 "IO::AIO::max_poll_req" and "IO::AIO::max_poll_time".
965 1244
966 If not all requests were processed for whatever reason, the 1245 If not all requests were processed for whatever reason, the
967 filehandle will still be ready when "poll_cb" returns, so normally 1246 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. 1247 you don't have to do anything special to have it called later.
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.
969 1255
970 Example: Install an Event watcher that automatically calls 1256 Example: Install an Event watcher that automatically calls
971 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
972 the SYNOPSIS section, at the top of this document): 1258 the SYNOPSIS section, at the top of this document):
973 1259
… …
1067 1353
1068 Under normal circumstances you don't need to call this function. 1354 Under normal circumstances you don't need to call this function.
1069 1355
1070 IO::AIO::max_idle $nthreads 1356 IO::AIO::max_idle $nthreads
1071 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
1072 (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
1073 seconds). That means if a thread becomes idle while $nthreads other 1359 timeout (default: 10 seconds). That means if a thread becomes idle
1074 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.
1075 1362
1076 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
1077 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
1078 resources under normal circumstances (1000 threads can easily 1365 resources under normal circumstances (1000 threads can easily
1079 consume 30MB of RAM). 1366 consume 30MB of RAM).
1080 1367
1081 The default is probably ok in most situations, especially if thread 1368 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 1369 creation is fast. If thread creation is very slow on your system you
1083 might want to use larger values. 1370 might want to use larger values.
1084 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
1085 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
1086 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
1087 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
1088 inexact: Better use an "aio_group" together with a feed callback. 1388 inexact: Better use an "aio_group" together with a feed callback.
1089 1389
1090 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
1091 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:
1092 "poll_cb" (and "poll_some" and other functions calling "poll_cb")
1093 function will block until the limit is no longer exceeded.
1094 1392
1095 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
1096 the number of outstanding requests. 1409 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 1410
1103 STATISTICAL INFORMATION 1411 STATISTICAL INFORMATION
1104 IO::AIO::nreqs 1412 IO::AIO::nreqs
1105 Returns the number of requests currently in the ready, execute or 1413 Returns the number of requests currently in the ready, execute or
1106 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
… …
1130 set to non-blocking operations). 1438 set to non-blocking operations).
1131 1439
1132 Returns the number of bytes copied, or -1 on error. 1440 Returns the number of bytes copied, or -1 on error.
1133 1441
1134 IO::AIO::fadvise $fh, $offset, $len, $advice 1442 IO::AIO::fadvise $fh, $offset, $len, $advice
1135 Simply calls the "posix_fadvise" function (see it's manpage for 1443 Simply calls the "posix_fadvise" function (see its manpage for
1136 details). The following advice constants are avaiable: 1444 details). The following advice constants are available:
1137 "IO::AIO::FADV_NORMAL", "IO::AIO::FADV_SEQUENTIAL", 1445 "IO::AIO::FADV_NORMAL", "IO::AIO::FADV_SEQUENTIAL",
1138 "IO::AIO::FADV_RANDOM", "IO::AIO::FADV_NOREUSE", 1446 "IO::AIO::FADV_RANDOM", "IO::AIO::FADV_NOREUSE",
1139 "IO::AIO::FADV_WILLNEED", "IO::AIO::FADV_DONTNEED". 1447 "IO::AIO::FADV_WILLNEED", "IO::AIO::FADV_DONTNEED".
1140 1448
1141 On systems that do not implement "posix_fadvise", this function 1449 On systems that do not implement "posix_fadvise", this function
1142 returns ENOSYS, otherwise the return value of "posix_fadvise". 1450 returns ENOSYS, otherwise the return value of "posix_fadvise".
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".
1143 1470
1144 IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset] 1471 IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
1145 Memory-maps a file (or anonymous memory range) and attaches it to 1472 Memory-maps a file (or anonymous memory range) and attaches it to
1146 the given $scalar, which will act like a string scalar. 1473 the given $scalar, which will act like a string scalar.
1147 1474
… …
1192 my $fast_md5 = md5 $data; 1519 my $fast_md5 = md5 $data;
1193 1520
1194 IO::AIO::munmap $scalar 1521 IO::AIO::munmap $scalar
1195 Removes a previous mmap and undefines the $scalar. 1522 Removes a previous mmap and undefines the $scalar.
1196 1523
1197 IO::AIO::mlockall $flags 1524 IO::AIO::munlock $scalar, $offset = 0, $length = undef
1198 Calls the "mlockall" function with the given $flags (a combination 1525 Calls the "munlock" function, undoing the effects of a previous
1199 of "IO::AIO::MCL_CURRENT" and "IO::AIO::MCL__FUTURE"). 1526 "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 1527
1204 IO::AIO::munlockall 1528 IO::AIO::munlockall
1205 Calls the "munlockall" function. 1529 Calls the "munlockall" function.
1206 1530
1207 On systems that do not implement "munlockall", this function returns 1531 On systems that do not implement "munlockall", this function returns
… …
1236 # Danga::Socket integration 1560 # Danga::Socket integration
1237 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno => 1561 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
1238 \&IO::AIO::poll_cb); 1562 \&IO::AIO::poll_cb);
1239 1563
1240 FORK BEHAVIOUR 1564 FORK BEHAVIOUR
1241 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.
1242 1572
1243 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
1244 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
1245 fork the parent simply leaves the quiescent state and continues 1575 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 1576
1251 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.
1252 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:
1253 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.
1254 1591
1255 MEMORY USAGE 1592 MEMORY USAGE
1256 Per-request usage: 1593 Per-request usage:
1257 1594
1258 Each aio request uses - depending on your architecture - around 100-200 1595 Each aio request uses - depending on your architecture - around 100-200

Diff Legend

– Removed lines
+ Added lines
< Changed lines
> Changed lines