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Revision 1.63 by root, Mon Mar 4 10:28:38 2019 UTC

1NAME 1NAME
2 IO::AIO - Asynchronous Input/Output 2 IO::AIO - Asynchronous/Advanced Input/Output
3 3
4SYNOPSIS 4SYNOPSIS
5 use IO::AIO; 5 use IO::AIO;
6 6
7 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub { 7 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
… …
55 not well-supported or restricted (GNU/Linux doesn't allow them on normal 55 not well-supported or restricted (GNU/Linux doesn't allow them on normal
56 files currently, for example), and they would only support aio_read and 56 files currently, for example), and they would only support aio_read and
57 aio_write, so the remaining functionality would have to be implemented 57 aio_write, so the remaining functionality would have to be implemented
58 using threads anyway. 58 using threads anyway.
59 59
60 In addition to asynchronous I/O, this module also exports some rather
61 arcane interfaces, such as "madvise" or linux's "splice" system call,
62 which is why the "A" in "AIO" can also mean *advanced*.
63
60 Although the module will work in the presence of other (Perl-) threads, 64 Although the module will work in the presence of other (Perl-) threads,
61 it is currently not reentrant in any way, so use appropriate locking 65 it is currently not reentrant in any way, so use appropriate locking
62 yourself, always call "poll_cb" from within the same thread, or never 66 yourself, always call "poll_cb" from within the same thread, or never
63 call "poll_cb" (or other "aio_" functions) recursively. 67 call "poll_cb" (or other "aio_" functions) recursively.
64 68
65 EXAMPLE 69 EXAMPLE
66 This is a simple example that uses the EV module and loads /etc/passwd 70 This is a simple example that uses the EV module and loads /etc/passwd
67 asynchronously: 71 asynchronously:
68 72
69 use Fcntl;
70 use EV; 73 use EV;
71 use IO::AIO; 74 use IO::AIO;
72 75
73 # register the IO::AIO callback with EV 76 # register the IO::AIO callback with EV
74 my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb; 77 my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
… …
91 94
92 # file contents now in $contents 95 # file contents now in $contents
93 print $contents; 96 print $contents;
94 97
95 # exit event loop and program 98 # exit event loop and program
96 EV::unloop; 99 EV::break;
97 }; 100 };
98 }; 101 };
99 102
100 # possibly queue up other requests, or open GUI windows, 103 # possibly queue up other requests, or open GUI windows,
101 # check for sockets etc. etc. 104 # check for sockets etc. etc.
102 105
103 # process events as long as there are some: 106 # process events as long as there are some:
104 EV::loop; 107 EV::run;
105 108
106REQUEST ANATOMY AND LIFETIME 109REQUEST ANATOMY AND LIFETIME
107 Every "aio_*" function creates a request. which is a C data structure 110 Every "aio_*" function creates a request. which is a C data structure
108 not directly visible to Perl. 111 not directly visible to Perl.
109 112
… …
146 the actual aio request is severed and calling its methods will 149 the actual aio request is severed and calling its methods will
147 either do nothing or result in a runtime error). 150 either do nothing or result in a runtime error).
148 151
149FUNCTIONS 152FUNCTIONS
150 QUICK OVERVIEW 153 QUICK OVERVIEW
151 This section simply lists the prototypes of the most important functions 154 This section simply lists the prototypes most of the functions for quick
152 for quick reference. See the following sections for function-by-function 155 reference. See the following sections for function-by-function
153 documentation. 156 documentation.
154 157
158 aio_wd $pathname, $callback->($wd)
155 aio_open $pathname, $flags, $mode, $callback->($fh) 159 aio_open $pathname, $flags, $mode, $callback->($fh)
156 aio_close $fh, $callback->($status) 160 aio_close $fh, $callback->($status)
161 aio_seek $fh,$offset,$whence, $callback->($offs)
157 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval) 162 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
158 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval) 163 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
159 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval) 164 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
160 aio_readahead $fh,$offset,$length, $callback->($retval) 165 aio_readahead $fh,$offset,$length, $callback->($retval)
161 aio_stat $fh_or_path, $callback->($status) 166 aio_stat $fh_or_path, $callback->($status)
162 aio_lstat $fh, $callback->($status) 167 aio_lstat $fh, $callback->($status)
163 aio_statvfs $fh_or_path, $callback->($statvfs) 168 aio_statvfs $fh_or_path, $callback->($statvfs)
164 aio_utime $fh_or_path, $atime, $mtime, $callback->($status) 169 aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
165 aio_chown $fh_or_path, $uid, $gid, $callback->($status) 170 aio_chown $fh_or_path, $uid, $gid, $callback->($status)
171 aio_chmod $fh_or_path, $mode, $callback->($status)
166 aio_truncate $fh_or_path, $offset, $callback->($status) 172 aio_truncate $fh_or_path, $offset, $callback->($status)
167 aio_chmod $fh_or_path, $mode, $callback->($status) 173 aio_allocate $fh, $mode, $offset, $len, $callback->($status)
174 aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
168 aio_unlink $pathname, $callback->($status) 175 aio_unlink $pathname, $callback->($status)
169 aio_mknod $path, $mode, $dev, $callback->($status) 176 aio_mknod $pathname, $mode, $dev, $callback->($status)
170 aio_link $srcpath, $dstpath, $callback->($status) 177 aio_link $srcpath, $dstpath, $callback->($status)
171 aio_symlink $srcpath, $dstpath, $callback->($status) 178 aio_symlink $srcpath, $dstpath, $callback->($status)
172 aio_readlink $path, $callback->($link) 179 aio_readlink $pathname, $callback->($link)
180 aio_realpath $pathname, $callback->($path)
173 aio_rename $srcpath, $dstpath, $callback->($status) 181 aio_rename $srcpath, $dstpath, $callback->($status)
182 aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
174 aio_mkdir $pathname, $mode, $callback->($status) 183 aio_mkdir $pathname, $mode, $callback->($status)
175 aio_rmdir $pathname, $callback->($status) 184 aio_rmdir $pathname, $callback->($status)
176 aio_readdir $pathname, $callback->($entries) 185 aio_readdir $pathname, $callback->($entries)
177 aio_readdirx $pathname, $flags, $callback->($entries, $flags) 186 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
178 IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST 187 IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
179 IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN 188 IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
189 aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
180 aio_load $path, $data, $callback->($status) 190 aio_load $pathname, $data, $callback->($status)
181 aio_copy $srcpath, $dstpath, $callback->($status) 191 aio_copy $srcpath, $dstpath, $callback->($status)
182 aio_move $srcpath, $dstpath, $callback->($status) 192 aio_move $srcpath, $dstpath, $callback->($status)
183 aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
184 aio_rmtree $path, $callback->($status) 193 aio_rmtree $pathname, $callback->($status)
194 aio_fcntl $fh, $cmd, $arg, $callback->($status)
195 aio_ioctl $fh, $request, $buf, $callback->($status)
185 aio_sync $callback->($status) 196 aio_sync $callback->($status)
197 aio_syncfs $fh, $callback->($status)
186 aio_fsync $fh, $callback->($status) 198 aio_fsync $fh, $callback->($status)
187 aio_fdatasync $fh, $callback->($status) 199 aio_fdatasync $fh, $callback->($status)
188 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status) 200 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
189 aio_pathsync $path, $callback->($status) 201 aio_pathsync $pathname, $callback->($status)
190 aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status) 202 aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
191 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status) 203 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
192 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status) 204 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
193 aio_mlockall $flags, $callback->($status) 205 aio_mlockall $flags, $callback->($status)
194 aio_group $callback->(...) 206 aio_group $callback->(...)
195 aio_nop $callback->() 207 aio_nop $callback->()
… …
204 IO::AIO::max_poll_reqs $nreqs 216 IO::AIO::max_poll_reqs $nreqs
205 IO::AIO::max_poll_time $seconds 217 IO::AIO::max_poll_time $seconds
206 IO::AIO::min_parallel $nthreads 218 IO::AIO::min_parallel $nthreads
207 IO::AIO::max_parallel $nthreads 219 IO::AIO::max_parallel $nthreads
208 IO::AIO::max_idle $nthreads 220 IO::AIO::max_idle $nthreads
221 IO::AIO::idle_timeout $seconds
209 IO::AIO::max_outstanding $maxreqs 222 IO::AIO::max_outstanding $maxreqs
210 IO::AIO::nreqs 223 IO::AIO::nreqs
211 IO::AIO::nready 224 IO::AIO::nready
212 IO::AIO::npending 225 IO::AIO::npending
226 $nfd = IO::AIO::get_fdlimit [EXPERIMENTAL]
227 IO::AIO::min_fdlimit $nfd [EXPERIMENTAL]
213 228
214 IO::AIO::sendfile $ofh, $ifh, $offset, $count 229 IO::AIO::sendfile $ofh, $ifh, $offset, $count
215 IO::AIO::fadvise $fh, $offset, $len, $advice 230 IO::AIO::fadvise $fh, $offset, $len, $advice
231 IO::AIO::mmap $scalar, $length, $prot, $flags[, $fh[, $offset]]
232 IO::AIO::munmap $scalar
233 IO::AIO::mremap $scalar, $new_length, $flags[, $new_address]
216 IO::AIO::madvise $scalar, $offset, $length, $advice 234 IO::AIO::madvise $scalar, $offset, $length, $advice
217 IO::AIO::mprotect $scalar, $offset, $length, $protect 235 IO::AIO::mprotect $scalar, $offset, $length, $protect
218 IO::AIO::munlock $scalar, $offset = 0, $length = undef 236 IO::AIO::munlock $scalar, $offset = 0, $length = undef
219 IO::AIO::munlockall 237 IO::AIO::munlockall
220 238
221 AIO REQUEST FUNCTIONS 239 API NOTES
222 All the "aio_*" calls are more or less thin wrappers around the syscall 240 All the "aio_*" calls are more or less thin wrappers around the syscall
223 with the same name (sans "aio_"). The arguments are similar or 241 with the same name (sans "aio_"). The arguments are similar or
224 identical, and they all accept an additional (and optional) $callback 242 identical, and they all accept an additional (and optional) $callback
225 argument which must be a code reference. This code reference will get 243 argument which must be a code reference. This code reference will be
226 called with the syscall return code (e.g. most syscalls return -1 on
227 error, unlike perl, which usually delivers "false") as its sole argument
228 after the given syscall has been executed asynchronously. 244 called after the syscall has been executed in an asynchronous fashion.
245 The results of the request will be passed as arguments to the callback
246 (and, if an error occured, in $!) - for most requests the syscall return
247 code (e.g. most syscalls return -1 on error, unlike perl, which usually
248 delivers "false").
249
250 Some requests (such as "aio_readdir") pass the actual results and
251 communicate failures by passing "undef".
229 252
230 All functions expecting a filehandle keep a copy of the filehandle 253 All functions expecting a filehandle keep a copy of the filehandle
231 internally until the request has finished. 254 internally until the request has finished.
232 255
233 All functions return request objects of type IO::AIO::REQ that allow 256 All functions return request objects of type IO::AIO::REQ that allow
234 further manipulation of those requests while they are in-flight. 257 further manipulation of those requests while they are in-flight.
235 258
236 The pathnames you pass to these routines *must* be absolute and encoded 259 The pathnames you pass to these routines *should* be absolute. The
237 as octets. The reason for the former is that at the time the request is 260 reason for this is that at the time the request is being executed, the
238 being executed, the current working directory could have changed. 261 current working directory could have changed. Alternatively, you can
239 Alternatively, you can make sure that you never change the current 262 make sure that you never change the current working directory anywhere
240 working directory anywhere in the program and then use relative paths. 263 in the program and then use relative paths. You can also take advantage
264 of IO::AIOs working directory abstraction, that lets you specify paths
265 relative to some previously-opened "working directory object" - see the
266 description of the "IO::AIO::WD" class later in this document.
241 267
242 To encode pathnames as octets, either make sure you either: a) always 268 To encode pathnames as octets, either make sure you either: a) always
243 pass in filenames you got from outside (command line, readdir etc.) 269 pass in filenames you got from outside (command line, readdir etc.)
244 without tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module 270 without tinkering, b) are in your native filesystem encoding, c) use the
245 and encode your pathnames to the locale (or other) encoding in effect in 271 Encode module and encode your pathnames to the locale (or other)
246 the user environment, d) use Glib::filename_from_unicode on unicode 272 encoding in effect in the user environment, d) use
247 filenames or e) use something else to ensure your scalar has the correct 273 Glib::filename_from_unicode on unicode filenames or e) use something
248 contents. 274 else to ensure your scalar has the correct contents.
249 275
250 This works, btw. independent of the internal UTF-8 bit, which IO::AIO 276 This works, btw. independent of the internal UTF-8 bit, which IO::AIO
251 handles correctly whether it is set or not. 277 handles correctly whether it is set or not.
252 278
279 AIO REQUEST FUNCTIONS
253 $prev_pri = aioreq_pri [$pri] 280 $prev_pri = aioreq_pri [$pri]
254 Returns the priority value that would be used for the next request 281 Returns the priority value that would be used for the next request
255 and, if $pri is given, sets the priority for the next aio request. 282 and, if $pri is given, sets the priority for the next aio request.
256 283
257 The default priority is 0, the minimum and maximum priorities are -4 284 The default priority is 0, the minimum and maximum priorities are -4
… …
279 Similar to "aioreq_pri", but subtracts the given value from the 306 Similar to "aioreq_pri", but subtracts the given value from the
280 current priority, so the effect is cumulative. 307 current priority, so the effect is cumulative.
281 308
282 aio_open $pathname, $flags, $mode, $callback->($fh) 309 aio_open $pathname, $flags, $mode, $callback->($fh)
283 Asynchronously open or create a file and call the callback with a 310 Asynchronously open or create a file and call the callback with a
284 newly created filehandle for the file. 311 newly created filehandle for the file (or "undef" in case of an
312 error).
285 313
286 The pathname passed to "aio_open" must be absolute. See API NOTES, 314 The pathname passed to "aio_open" must be absolute. See API NOTES,
287 above, for an explanation. 315 above, for an explanation.
288 316
289 The $flags argument is a bitmask. See the "Fcntl" module for a list. 317 The $flags argument is a bitmask. See the "Fcntl" module for a list.
… …
305 } else { 333 } else {
306 die "open failed: $!\n"; 334 die "open failed: $!\n";
307 } 335 }
308 }; 336 };
309 337
338 In addition to all the common open modes/flags ("O_RDONLY",
339 "O_WRONLY", "O_RDWR", "O_CREAT", "O_TRUNC", "O_EXCL" and
340 "O_APPEND"), the following POSIX and non-POSIX constants are
341 available (missing ones on your system are, as usual, 0):
342
343 "O_ASYNC", "O_DIRECT", "O_NOATIME", "O_CLOEXEC", "O_NOCTTY",
344 "O_NOFOLLOW", "O_NONBLOCK", "O_EXEC", "O_SEARCH", "O_DIRECTORY",
345 "O_DSYNC", "O_RSYNC", "O_SYNC", "O_PATH", "O_TMPFILE", "O_TTY_INIT"
346 and "O_ACCMODE".
347
310 aio_close $fh, $callback->($status) 348 aio_close $fh, $callback->($status)
311 Asynchronously close a file and call the callback with the result 349 Asynchronously close a file and call the callback with the result
312 code. 350 code.
313 351
314 Unfortunately, you can't do this to perl. Perl *insists* very 352 Unfortunately, you can't do this to perl. Perl *insists* very
… …
319 will use dup2 to overwrite the file descriptor with the write-end of 357 will use dup2 to overwrite the file descriptor with the write-end of
320 a pipe (the pipe fd will be created on demand and will be cached). 358 a pipe (the pipe fd will be created on demand and will be cached).
321 359
322 Or in other words: the file descriptor will be closed, but it will 360 Or in other words: the file descriptor will be closed, but it will
323 not be free for reuse until the perl filehandle is closed. 361 not be free for reuse until the perl filehandle is closed.
362
363 aio_seek $fh, $offset, $whence, $callback->($offs)
364 Seeks the filehandle to the new $offset, similarly to perl's
365 "sysseek". The $whence can use the traditional values (0 for
366 "IO::AIO::SEEK_SET", 1 for "IO::AIO::SEEK_CUR" or 2 for
367 "IO::AIO::SEEK_END").
368
369 The resulting absolute offset will be passed to the callback, or -1
370 in case of an error.
371
372 In theory, the $whence constants could be different than the
373 corresponding values from Fcntl, but perl guarantees they are the
374 same, so don't panic.
375
376 As a GNU/Linux (and maybe Solaris) extension, also the constants
377 "IO::AIO::SEEK_DATA" and "IO::AIO::SEEK_HOLE" are available, if they
378 could be found. No guarantees about suitability for use in
379 "aio_seek" or Perl's "sysseek" can be made though, although I would
380 naively assume they "just work".
324 381
325 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval) 382 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
326 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval) 383 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
327 Reads or writes $length bytes from or to the specified $fh and 384 Reads or writes $length bytes from or to the specified $fh and
328 $offset into the scalar given by $data and offset $dataoffset and 385 $offset into the scalar given by $data and offset $dataoffset and
329 calls the callback without the actual number of bytes read (or -1 on 386 calls the callback with the actual number of bytes transferred (or
330 error, just like the syscall). 387 -1 on error, just like the syscall).
331 388
332 "aio_read" will, like "sysread", shrink or grow the $data scalar to 389 "aio_read" will, like "sysread", shrink or grow the $data scalar to
333 offset plus the actual number of bytes read. 390 offset plus the actual number of bytes read.
334 391
335 If $offset is undefined, then the current file descriptor offset 392 If $offset is undefined, then the current file descriptor offset
… …
357 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval) 414 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
358 Tries to copy $length bytes from $in_fh to $out_fh. It starts 415 Tries to copy $length bytes from $in_fh to $out_fh. It starts
359 reading at byte offset $in_offset, and starts writing at the current 416 reading at byte offset $in_offset, and starts writing at the current
360 file offset of $out_fh. Because of that, it is not safe to issue 417 file offset of $out_fh. Because of that, it is not safe to issue
361 more than one "aio_sendfile" per $out_fh, as they will interfere 418 more than one "aio_sendfile" per $out_fh, as they will interfere
362 with each other. 419 with each other. The same $in_fh works fine though, as this function
420 does not move or use the file offset of $in_fh.
363 421
364 Please note that "aio_sendfile" can read more bytes from $in_fh than 422 Please note that "aio_sendfile" can read more bytes from $in_fh than
365 are written, and there is no way to find out how many bytes have 423 are written, and there is no way to find out how many more bytes
366 been read from "aio_sendfile" alone, as "aio_sendfile" only provides 424 have been read from "aio_sendfile" alone, as "aio_sendfile" only
367 the number of bytes written to $out_fh. Only if the result value 425 provides the number of bytes written to $out_fh. Only if the result
368 equals $length one can assume that $length bytes have been read. 426 value equals $length one can assume that $length bytes have been
427 read.
369 428
370 Unlike with other "aio_" functions, it makes a lot of sense to use 429 Unlike with other "aio_" functions, it makes a lot of sense to use
371 "aio_sendfile" on non-blocking sockets, as long as one end 430 "aio_sendfile" on non-blocking sockets, as long as one end
372 (typically the $in_fh) is a file - the file I/O will then be 431 (typically the $in_fh) is a file - the file I/O will then be
373 asynchronous, while the socket I/O will be non-blocking. Note, 432 asynchronous, while the socket I/O will be non-blocking. Note,
374 however, that you can run into a trap where "aio_sendfile" reads 433 however, that you can run into a trap where "aio_sendfile" reads
375 some data with readahead, then fails to write all data, and when the 434 some data with readahead, then fails to write all data, and when the
376 socket is ready the next time, the data in the cache is already 435 socket is ready the next time, the data in the cache is already
377 lost, forcing "aio_sendfile" to again hit the disk. Explicit 436 lost, forcing "aio_sendfile" to again hit the disk. Explicit
378 "aio_read" + "aio_write" let's you control resource usage much 437 "aio_read" + "aio_write" let's you better control resource usage.
379 better.
380 438
381 This call tries to make use of a native "sendfile" syscall to 439 This call tries to make use of a native "sendfile"-like syscall to
382 provide zero-copy operation. For this to work, $out_fh should refer 440 provide zero-copy operation. For this to work, $out_fh should refer
383 to a socket, and $in_fh should refer to an mmap'able file. 441 to a socket, and $in_fh should refer to an mmap'able file.
384 442
385 If a native sendfile cannot be found or it fails with "ENOSYS", 443 If a native sendfile cannot be found or it fails with "ENOSYS",
386 "ENOTSUP", "EOPNOTSUPP", "EAFNOSUPPORT", "EPROTOTYPE" or "ENOTSOCK", 444 "EINVAL", "ENOTSUP", "EOPNOTSUPP", "EAFNOSUPPORT", "EPROTOTYPE" or
387 it will be emulated, so you can call "aio_sendfile" on any type of 445 "ENOTSOCK", it will be emulated, so you can call "aio_sendfile" on
388 filehandle regardless of the limitations of the operating system. 446 any type of filehandle regardless of the limitations of the
447 operating system.
448
449 As native sendfile syscalls (as practically any non-POSIX interface
450 hacked together in a hurry to improve benchmark numbers) tend to be
451 rather buggy on many systems, this implementation tries to work
452 around some known bugs in Linux and FreeBSD kernels (probably
453 others, too), but that might fail, so you really really should check
454 the return value of "aio_sendfile" - fewer bytes than expected might
455 have been transferred.
389 456
390 aio_readahead $fh,$offset,$length, $callback->($retval) 457 aio_readahead $fh,$offset,$length, $callback->($retval)
391 "aio_readahead" populates the page cache with data from a file so 458 "aio_readahead" populates the page cache with data from a file so
392 that subsequent reads from that file will not block on disk I/O. The 459 that subsequent reads from that file will not block on disk I/O. The
393 $offset argument specifies the starting point from which data is to 460 $offset argument specifies the starting point from which data is to
… …
396 to a page boundary and bytes are read up to the next page boundary 463 to a page boundary and bytes are read up to the next page boundary
397 greater than or equal to (off-set+length). "aio_readahead" does not 464 greater than or equal to (off-set+length). "aio_readahead" does not
398 read beyond the end of the file. The current file offset of the file 465 read beyond the end of the file. The current file offset of the file
399 is left unchanged. 466 is left unchanged.
400 467
401 If that syscall doesn't exist (likely if your OS isn't Linux) it 468 If that syscall doesn't exist (likely if your kernel isn't Linux) it
402 will be emulated by simply reading the data, which would have a 469 will be emulated by simply reading the data, which would have a
403 similar effect. 470 similar effect.
404 471
405 aio_stat $fh_or_path, $callback->($status) 472 aio_stat $fh_or_path, $callback->($status)
406 aio_lstat $fh, $callback->($status) 473 aio_lstat $fh, $callback->($status)
407 Works like perl's "stat" or "lstat" in void context. The callback 474 Works almost exactly like perl's "stat" or "lstat" in void context.
408 will be called after the stat and the results will be available 475 The callback will be called after the stat and the results will be
409 using "stat _" or "-s _" etc... 476 available using "stat _" or "-s _" and other tests (with the
477 exception of "-B" and "-T").
410 478
411 The pathname passed to "aio_stat" must be absolute. See API NOTES, 479 The pathname passed to "aio_stat" must be absolute. See API NOTES,
412 above, for an explanation. 480 above, for an explanation.
413 481
414 Currently, the stats are always 64-bit-stats, i.e. instead of 482 Currently, the stats are always 64-bit-stats, i.e. instead of
415 returning an error when stat'ing a large file, the results will be 483 returning an error when stat'ing a large file, the results will be
416 silently truncated unless perl itself is compiled with large file 484 silently truncated unless perl itself is compiled with large file
417 support. 485 support.
486
487 To help interpret the mode and dev/rdev stat values, IO::AIO offers
488 the following constants and functions (if not implemented, the
489 constants will be 0 and the functions will either "croak" or fall
490 back on traditional behaviour).
491
492 "S_IFMT", "S_IFIFO", "S_IFCHR", "S_IFBLK", "S_IFLNK", "S_IFREG",
493 "S_IFDIR", "S_IFWHT", "S_IFSOCK", "IO::AIO::major $dev_t",
494 "IO::AIO::minor $dev_t", "IO::AIO::makedev $major, $minor".
495
496 To access higher resolution stat timestamps, see "SUBSECOND STAT
497 TIME ACCESS".
418 498
419 Example: Print the length of /etc/passwd: 499 Example: Print the length of /etc/passwd:
420 500
421 aio_stat "/etc/passwd", sub { 501 aio_stat "/etc/passwd", sub {
422 $_[0] and die "stat failed: $!"; 502 $_[0] and die "stat failed: $!";
… …
469 aio_utime $fh_or_path, $atime, $mtime, $callback->($status) 549 aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
470 Works like perl's "utime" function (including the special case of 550 Works like perl's "utime" function (including the special case of
471 $atime and $mtime being undef). Fractional times are supported if 551 $atime and $mtime being undef). Fractional times are supported if
472 the underlying syscalls support them. 552 the underlying syscalls support them.
473 553
474 When called with a pathname, uses utimes(2) if available, otherwise 554 When called with a pathname, uses utimensat(2) or utimes(2) if
475 utime(2). If called on a file descriptor, uses futimes(2) if 555 available, otherwise utime(2). If called on a file descriptor, uses
476 available, otherwise returns ENOSYS, so this is not portable. 556 futimens(2) or futimes(2) if available, otherwise returns ENOSYS, so
557 this is not portable.
477 558
478 Examples: 559 Examples:
479 560
480 # set atime and mtime to current time (basically touch(1)): 561 # set atime and mtime to current time (basically touch(1)):
481 aio_utime "path", undef, undef; 562 aio_utime "path", undef, undef;
… …
495 aio_chown "path", 0, undef; 576 aio_chown "path", 0, undef;
496 577
497 aio_truncate $fh_or_path, $offset, $callback->($status) 578 aio_truncate $fh_or_path, $offset, $callback->($status)
498 Works like truncate(2) or ftruncate(2). 579 Works like truncate(2) or ftruncate(2).
499 580
581 aio_allocate $fh, $mode, $offset, $len, $callback->($status)
582 Allocates or frees disk space according to the $mode argument. See
583 the linux "fallocate" documentation for details.
584
585 $mode is usually 0 or "IO::AIO::FALLOC_FL_KEEP_SIZE" to allocate
586 space, or "IO::AIO::FALLOC_FL_PUNCH_HOLE |
587 IO::AIO::FALLOC_FL_KEEP_SIZE", to deallocate a file range.
588
589 IO::AIO also supports "FALLOC_FL_COLLAPSE_RANGE", to remove a range
590 (without leaving a hole), "FALLOC_FL_ZERO_RANGE", to zero a range,
591 "FALLOC_FL_INSERT_RANGE" to insert a range and
592 "FALLOC_FL_UNSHARE_RANGE" to unshare shared blocks (see your
593 fallocate(2) manpage).
594
595 The file system block size used by "fallocate" is presumably the
596 "f_bsize" returned by "statvfs", but different filesystems and
597 filetypes can dictate other limitations.
598
599 If "fallocate" isn't available or cannot be emulated (currently no
600 emulation will be attempted), passes -1 and sets $! to "ENOSYS".
601
500 aio_chmod $fh_or_path, $mode, $callback->($status) 602 aio_chmod $fh_or_path, $mode, $callback->($status)
501 Works like perl's "chmod" function. 603 Works like perl's "chmod" function.
502 604
503 aio_unlink $pathname, $callback->($status) 605 aio_unlink $pathname, $callback->($status)
504 Asynchronously unlink (delete) a file and call the callback with the 606 Asynchronously unlink (delete) a file and call the callback with the
505 result code. 607 result code.
506 608
507 aio_mknod $path, $mode, $dev, $callback->($status) 609 aio_mknod $pathname, $mode, $dev, $callback->($status)
508 [EXPERIMENTAL] 610 [EXPERIMENTAL]
509 611
510 Asynchronously create a device node (or fifo). See mknod(2). 612 Asynchronously create a device node (or fifo). See mknod(2).
511 613
512 The only (POSIX-) portable way of calling this function is: 614 The only (POSIX-) portable way of calling this function is:
513 615
514 aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ... 616 aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
617
618 See "aio_stat" for info about some potentially helpful extra
619 constants and functions.
515 620
516 aio_link $srcpath, $dstpath, $callback->($status) 621 aio_link $srcpath, $dstpath, $callback->($status)
517 Asynchronously create a new link to the existing object at $srcpath 622 Asynchronously create a new link to the existing object at $srcpath
518 at the path $dstpath and call the callback with the result code. 623 at the path $dstpath and call the callback with the result code.
519 624
520 aio_symlink $srcpath, $dstpath, $callback->($status) 625 aio_symlink $srcpath, $dstpath, $callback->($status)
521 Asynchronously create a new symbolic link to the existing object at 626 Asynchronously create a new symbolic link to the existing object at
522 $srcpath at the path $dstpath and call the callback with the result 627 $srcpath at the path $dstpath and call the callback with the result
523 code. 628 code.
524 629
525 aio_readlink $path, $callback->($link) 630 aio_readlink $pathname, $callback->($link)
526 Asynchronously read the symlink specified by $path and pass it to 631 Asynchronously read the symlink specified by $path and pass it to
527 the callback. If an error occurs, nothing or undef gets passed to 632 the callback. If an error occurs, nothing or undef gets passed to
528 the callback. 633 the callback.
529 634
635 aio_realpath $pathname, $callback->($path)
636 Asynchronously make the path absolute and resolve any symlinks in
637 $path. The resulting path only consists of directories (same as
638 Cwd::realpath).
639
640 This request can be used to get the absolute path of the current
641 working directory by passing it a path of . (a single dot).
642
530 aio_rename $srcpath, $dstpath, $callback->($status) 643 aio_rename $srcpath, $dstpath, $callback->($status)
531 Asynchronously rename the object at $srcpath to $dstpath, just as 644 Asynchronously rename the object at $srcpath to $dstpath, just as
532 rename(2) and call the callback with the result code. 645 rename(2) and call the callback with the result code.
646
647 On systems that support the AIO::WD working directory abstraction
648 natively, the case "[$wd, "."]" as $srcpath is specialcased -
649 instead of failing, "rename" is called on the absolute path of $wd.
650
651 aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
652 Basically a version of "aio_rename" with an additional $flags
653 argument. Calling this with "$flags=0" is the same as calling
654 "aio_rename".
655
656 Non-zero flags are currently only supported on GNU/Linux systems
657 that support renameat2. Other systems fail with "ENOSYS" in this
658 case.
659
660 The following constants are available (missing ones are, as usual
661 0), see renameat2(2) for details:
662
663 "IO::AIO::RENAME_NOREPLACE", "IO::AIO::RENAME_EXCHANGE" and
664 "IO::AIO::RENAME_WHITEOUT".
533 665
534 aio_mkdir $pathname, $mode, $callback->($status) 666 aio_mkdir $pathname, $mode, $callback->($status)
535 Asynchronously mkdir (create) a directory and call the callback with 667 Asynchronously mkdir (create) a directory and call the callback with
536 the result code. $mode will be modified by the umask at the time the 668 the result code. $mode will be modified by the umask at the time the
537 request is executed, so do not change your umask. 669 request is executed, so do not change your umask.
538 670
539 aio_rmdir $pathname, $callback->($status) 671 aio_rmdir $pathname, $callback->($status)
540 Asynchronously rmdir (delete) a directory and call the callback with 672 Asynchronously rmdir (delete) a directory and call the callback with
541 the result code. 673 the result code.
542 674
675 On systems that support the AIO::WD working directory abstraction
676 natively, the case "[$wd, "."]" is specialcased - instead of
677 failing, "rmdir" is called on the absolute path of $wd.
678
543 aio_readdir $pathname, $callback->($entries) 679 aio_readdir $pathname, $callback->($entries)
544 Unlike the POSIX call of the same name, "aio_readdir" reads an 680 Unlike the POSIX call of the same name, "aio_readdir" reads an
545 entire directory (i.e. opendir + readdir + closedir). The entries 681 entire directory (i.e. opendir + readdir + closedir). The entries
546 will not be sorted, and will NOT include the "." and ".." entries. 682 will not be sorted, and will NOT include the "." and ".." entries.
547 683
548 The callback is passed a single argument which is either "undef" or 684 The callback is passed a single argument which is either "undef" or
549 an array-ref with the filenames. 685 an array-ref with the filenames.
550 686
551 aio_readdirx $pathname, $flags, $callback->($entries, $flags) 687 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
552 Quite similar to "aio_readdir", but the $flags argument allows to 688 Quite similar to "aio_readdir", but the $flags argument allows one
553 tune behaviour and output format. In case of an error, $entries will 689 to tune behaviour and output format. In case of an error, $entries
554 be "undef". 690 will be "undef".
555 691
556 The flags are a combination of the following constants, ORed 692 The flags are a combination of the following constants, ORed
557 together (the flags will also be passed to the callback, possibly 693 together (the flags will also be passed to the callback, possibly
558 modified): 694 modified):
559 695
560 IO::AIO::READDIR_DENTS 696 IO::AIO::READDIR_DENTS
561 When this flag is off, then the callback gets an arrayref with 697 Normally the callback gets an arrayref consisting of names only
562 of names only (as with "aio_readdir"), otherwise it gets an 698 (as with "aio_readdir"). If this flag is set, then the callback
563 arrayref with "[$name, $type, $inode]" arrayrefs, each 699 gets an arrayref with "[$name, $type, $inode]" arrayrefs, each
564 describing a single directory entry in more detail. 700 describing a single directory entry in more detail:
565 701
566 $name is the name of the entry. 702 $name is the name of the entry.
567 703
568 $type is one of the "IO::AIO::DT_xxx" constants: 704 $type is one of the "IO::AIO::DT_xxx" constants:
569 705
570 "IO::AIO::DT_UNKNOWN", "IO::AIO::DT_FIFO", "IO::AIO::DT_CHR", 706 "IO::AIO::DT_UNKNOWN", "IO::AIO::DT_FIFO", "IO::AIO::DT_CHR",
571 "IO::AIO::DT_DIR", "IO::AIO::DT_BLK", "IO::AIO::DT_REG", 707 "IO::AIO::DT_DIR", "IO::AIO::DT_BLK", "IO::AIO::DT_REG",
572 "IO::AIO::DT_LNK", "IO::AIO::DT_SOCK", "IO::AIO::DT_WHT". 708 "IO::AIO::DT_LNK", "IO::AIO::DT_SOCK", "IO::AIO::DT_WHT".
573 709
574 "IO::AIO::DT_UNKNOWN" means just that: readdir does not know. If 710 "IO::AIO::DT_UNKNOWN" means just that: readdir does not know. If
575 you need to know, you have to run stat yourself. Also, for speed 711 you need to know, you have to run stat yourself. Also, for
576 reasons, the $type scalars are read-only: you can not modify 712 speed/memory reasons, the $type scalars are read-only: you must
577 them. 713 not modify them.
578 714
579 $inode is the inode number (which might not be exact on systems 715 $inode is the inode number (which might not be exact on systems
580 with 64 bit inode numbers and 32 bit perls). This field has 716 with 64 bit inode numbers and 32 bit perls). This field has
581 unspecified content on systems that do not deliver the inode 717 unspecified content on systems that do not deliver the inode
582 information. 718 information.
583 719
584 IO::AIO::READDIR_DIRS_FIRST 720 IO::AIO::READDIR_DIRS_FIRST
585 When this flag is set, then the names will be returned in an 721 When this flag is set, then the names will be returned in an
586 order where likely directories come first. This is useful when 722 order where likely directories come first, in optimal stat
587 you need to quickly find directories, or you want to find all 723 order. This is useful when you need to quickly find directories,
588 directories while avoiding to stat() each entry. 724 or you want to find all directories while avoiding to stat()
725 each entry.
589 726
590 If the system returns type information in readdir, then this is 727 If the system returns type information in readdir, then this is
591 used to find directories directly. Otherwise, likely directories 728 used to find directories directly. Otherwise, likely directories
592 are files beginning with ".", or otherwise files with no dots, 729 are names beginning with ".", or otherwise names with no dots,
593 of which files with short names are tried first. 730 of which names with short names are tried first.
594 731
595 IO::AIO::READDIR_STAT_ORDER 732 IO::AIO::READDIR_STAT_ORDER
596 When this flag is set, then the names will be returned in an 733 When this flag is set, then the names will be returned in an
597 order suitable for stat()'ing each one. That is, when you plan 734 order suitable for stat()'ing each one. That is, when you plan
598 to stat() all files in the given directory, then the returned 735 to stat() most or all files in the given directory, then the
599 order will likely be fastest. 736 returned order will likely be faster.
600 737
601 If both this flag and "IO::AIO::READDIR_DIRS_FIRST" are 738 If both this flag and "IO::AIO::READDIR_DIRS_FIRST" are
602 specified, then the likely dirs come first, resulting in a less 739 specified, then the likely dirs come first, resulting in a less
603 optimal stat order. 740 optimal stat order for stat'ing all entries, but likely a more
741 optimal order for finding subdirectories.
604 742
605 IO::AIO::READDIR_FOUND_UNKNOWN 743 IO::AIO::READDIR_FOUND_UNKNOWN
606 This flag should not be set when calling "aio_readdirx". 744 This flag should not be set when calling "aio_readdirx".
607 Instead, it is being set by "aio_readdirx", when any of the 745 Instead, it is being set by "aio_readdirx", when any of the
608 $type's found were "IO::AIO::DT_UNKNOWN". The absense of this 746 $type's found were "IO::AIO::DT_UNKNOWN". The absence of this
609 flag therefore indicates that all $type's are known, which can 747 flag therefore indicates that all $type's are known, which can
610 be used to speed up some algorithms. 748 be used to speed up some algorithms.
611 749
750 aio_slurp $pathname, $offset, $length, $data, $callback->($status)
751 Opens, reads and closes the given file. The data is put into $data,
752 which is resized as required.
753
754 If $offset is negative, then it is counted from the end of the file.
755
756 If $length is zero, then the remaining length of the file is used.
757 Also, in this case, the same limitations to modifying $data apply as
758 when IO::AIO::mmap is used, i.e. it must only be modified in-place
759 with "substr". If the size of the file is known, specifying a
760 non-zero $length results in a performance advantage.
761
762 This request is similar to the older "aio_load" request, but since
763 it is a single request, it might be more efficient to use.
764
765 Example: load /etc/passwd into $passwd.
766
767 my $passwd;
768 aio_slurp "/etc/passwd", 0, 0, $passwd, sub {
769 $_[0] >= 0
770 or die "/etc/passwd: $!\n";
771
772 printf "/etc/passwd is %d bytes long, and contains:\n", length $passwd;
773 print $passwd;
774 };
775 IO::AIO::flush;
776
612 aio_load $path, $data, $callback->($status) 777 aio_load $pathname, $data, $callback->($status)
613 This is a composite request that tries to fully load the given file 778 This is a composite request that tries to fully load the given file
614 into memory. Status is the same as with aio_read. 779 into memory. Status is the same as with aio_read.
780
781 Using "aio_slurp" might be more efficient, as it is a single
782 request.
615 783
616 aio_copy $srcpath, $dstpath, $callback->($status) 784 aio_copy $srcpath, $dstpath, $callback->($status)
617 Try to copy the *file* (directories not supported as either source 785 Try to copy the *file* (directories not supported as either source
618 or destination) from $srcpath to $dstpath and call the callback with 786 or destination) from $srcpath to $dstpath and call the callback with
619 a status of 0 (ok) or -1 (error, see $!). 787 a status of 0 (ok) or -1 (error, see $!).
620 788
789 Existing destination files will be truncated.
790
621 This is a composite request that creates the destination file with 791 This is a composite request that creates the destination file with
622 mode 0200 and copies the contents of the source file into it using 792 mode 0200 and copies the contents of the source file into it using
623 "aio_sendfile", followed by restoring atime, mtime, access mode and 793 "aio_sendfile", followed by restoring atime, mtime, access mode and
624 uid/gid, in that order. 794 uid/gid, in that order.
625 795
… …
634 804
635 This is a composite request that tries to rename(2) the file first; 805 This is a composite request that tries to rename(2) the file first;
636 if rename fails with "EXDEV", it copies the file with "aio_copy" 806 if rename fails with "EXDEV", it copies the file with "aio_copy"
637 and, if that is successful, unlinks the $srcpath. 807 and, if that is successful, unlinks the $srcpath.
638 808
639 aio_scandir $path, $maxreq, $callback->($dirs, $nondirs) 809 aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
640 Scans a directory (similar to "aio_readdir") but additionally tries 810 Scans a directory (similar to "aio_readdir") but additionally tries
641 to efficiently separate the entries of directory $path into two sets 811 to efficiently separate the entries of directory $path into two sets
642 of names, directories you can recurse into (directories), and ones 812 of names, directories you can recurse into (directories), and ones
643 you cannot recurse into (everything else, including symlinks to 813 you cannot recurse into (everything else, including symlinks to
644 directories). 814 directories).
645 815
646 "aio_scandir" is a composite request that creates of many sub 816 "aio_scandir" is a composite request that generates many sub
647 requests_ $maxreq specifies the maximum number of outstanding aio 817 requests. $maxreq specifies the maximum number of outstanding aio
648 requests that this function generates. If it is "<= 0", then a 818 requests that this function generates. If it is "<= 0", then a
649 suitable default will be chosen (currently 4). 819 suitable default will be chosen (currently 4).
650 820
651 On error, the callback is called without arguments, otherwise it 821 On error, the callback is called without arguments, otherwise it
652 receives two array-refs with path-relative entry names. 822 receives two array-refs with path-relative entry names.
… …
677 Then entries will be sorted into likely directories a non-initial 847 Then entries will be sorted into likely directories a non-initial
678 dot currently) and likely non-directories (see "aio_readdirx"). Then 848 dot currently) and likely non-directories (see "aio_readdirx"). Then
679 every entry plus an appended "/." will be "stat"'ed, likely 849 every entry plus an appended "/." will be "stat"'ed, likely
680 directories first, in order of their inode numbers. If that 850 directories first, in order of their inode numbers. If that
681 succeeds, it assumes that the entry is a directory or a symlink to 851 succeeds, it assumes that the entry is a directory or a symlink to
682 directory (which will be checked seperately). This is often faster 852 directory (which will be checked separately). This is often faster
683 than stat'ing the entry itself because filesystems might detect the 853 than stat'ing the entry itself because filesystems might detect the
684 type of the entry without reading the inode data (e.g. ext2fs 854 type of the entry without reading the inode data (e.g. ext2fs
685 filetype feature), even on systems that cannot return the filetype 855 filetype feature), even on systems that cannot return the filetype
686 information on readdir. 856 information on readdir.
687 857
… …
693 863
694 It will also likely work on non-POSIX filesystems with reduced 864 It will also likely work on non-POSIX filesystems with reduced
695 efficiency as those tend to return 0 or 1 as link counts, which 865 efficiency as those tend to return 0 or 1 as link counts, which
696 disables the directory counting heuristic. 866 disables the directory counting heuristic.
697 867
698 aio_rmtree $path, $callback->($status) 868 aio_rmtree $pathname, $callback->($status)
699 Delete a directory tree starting (and including) $path, return the 869 Delete a directory tree starting (and including) $path, return the
700 status of the final "rmdir" only. This is a composite request that 870 status of the final "rmdir" only. This is a composite request that
701 uses "aio_scandir" to recurse into and rmdir directories, and unlink 871 uses "aio_scandir" to recurse into and rmdir directories, and unlink
702 everything else. 872 everything else.
703 873
874 aio_fcntl $fh, $cmd, $arg, $callback->($status)
875 aio_ioctl $fh, $request, $buf, $callback->($status)
876 These work just like the "fcntl" and "ioctl" built-in functions,
877 except they execute asynchronously and pass the return value to the
878 callback.
879
880 Both calls can be used for a lot of things, some of which make more
881 sense to run asynchronously in their own thread, while some others
882 make less sense. For example, calls that block waiting for external
883 events, such as locking, will also lock down an I/O thread while it
884 is waiting, which can deadlock the whole I/O system. At the same
885 time, there might be no alternative to using a thread to wait.
886
887 So in general, you should only use these calls for things that do
888 (filesystem) I/O, not for things that wait for other events
889 (network, other processes), although if you are careful and know
890 what you are doing, you still can.
891
892 The following constants are available (missing ones are, as usual
893 0):
894
895 "F_DUPFD_CLOEXEC",
896
897 "F_OFD_GETLK", "F_OFD_SETLK", "F_OFD_GETLKW",
898
899 "FIFREEZE", "FITHAW", "FITRIM", "FICLONE", "FICLONERANGE",
900 "FIDEDUPERANGE".
901
902 "FS_IOC_GETFLAGS", "FS_IOC_SETFLAGS", "FS_IOC_GETVERSION",
903 "FS_IOC_SETVERSION", "FS_IOC_FIEMAP".
904
905 "FS_IOC_FSGETXATTR", "FS_IOC_FSSETXATTR",
906 "FS_IOC_SET_ENCRYPTION_POLICY", "FS_IOC_GET_ENCRYPTION_PWSALT",
907 "FS_IOC_GET_ENCRYPTION_POLICY", "FS_KEY_DESCRIPTOR_SIZE".
908
909 "FS_SECRM_FL", "FS_UNRM_FL", "FS_COMPR_FL", "FS_SYNC_FL",
910 "FS_IMMUTABLE_FL", "FS_APPEND_FL", "FS_NODUMP_FL", "FS_NOATIME_FL",
911 "FS_DIRTY_FL", "FS_COMPRBLK_FL", "FS_NOCOMP_FL", "FS_ENCRYPT_FL",
912 "FS_BTREE_FL", "FS_INDEX_FL", "FS_JOURNAL_DATA_FL", "FS_NOTAIL_FL",
913 "FS_DIRSYNC_FL", "FS_TOPDIR_FL", "FS_FL_USER_MODIFIABLE".
914
915 "FS_XFLAG_REALTIME", "FS_XFLAG_PREALLOC", "FS_XFLAG_IMMUTABLE",
916 "FS_XFLAG_APPEND", "FS_XFLAG_SYNC", "FS_XFLAG_NOATIME",
917 "FS_XFLAG_NODUMP", "FS_XFLAG_RTINHERIT", "FS_XFLAG_PROJINHERIT",
918 "FS_XFLAG_NOSYMLINKS", "FS_XFLAG_EXTSIZE", "FS_XFLAG_EXTSZINHERIT",
919 "FS_XFLAG_NODEFRAG", "FS_XFLAG_FILESTREAM", "FS_XFLAG_DAX",
920 "FS_XFLAG_HASATTR",
921
704 aio_sync $callback->($status) 922 aio_sync $callback->($status)
705 Asynchronously call sync and call the callback when finished. 923 Asynchronously call sync and call the callback when finished.
706 924
707 aio_fsync $fh, $callback->($status) 925 aio_fsync $fh, $callback->($status)
708 Asynchronously call fsync on the given filehandle and call the 926 Asynchronously call fsync on the given filehandle and call the
… …
712 Asynchronously call fdatasync on the given filehandle and call the 930 Asynchronously call fdatasync on the given filehandle and call the
713 callback with the fdatasync result code. 931 callback with the fdatasync result code.
714 932
715 If this call isn't available because your OS lacks it or it couldn't 933 If this call isn't available because your OS lacks it or it couldn't
716 be detected, it will be emulated by calling "fsync" instead. 934 be detected, it will be emulated by calling "fsync" instead.
935
936 aio_syncfs $fh, $callback->($status)
937 Asynchronously call the syncfs syscall to sync the filesystem
938 associated to the given filehandle and call the callback with the
939 syncfs result code. If syncfs is not available, calls sync(), but
940 returns -1 and sets errno to "ENOSYS" nevertheless.
717 941
718 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status) 942 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
719 Sync the data portion of the file specified by $offset and $length 943 Sync the data portion of the file specified by $offset and $length
720 to disk (but NOT the metadata), by calling the Linux-specific 944 to disk (but NOT the metadata), by calling the Linux-specific
721 sync_file_range call. If sync_file_range is not available or it 945 sync_file_range call. If sync_file_range is not available or it
… …
725 "IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE", 949 "IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE",
726 "IO::AIO::SYNC_FILE_RANGE_WRITE" and 950 "IO::AIO::SYNC_FILE_RANGE_WRITE" and
727 "IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER": refer to the sync_file_range 951 "IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER": refer to the sync_file_range
728 manpage for details. 952 manpage for details.
729 953
730 aio_pathsync $path, $callback->($status) 954 aio_pathsync $pathname, $callback->($status)
731 This request tries to open, fsync and close the given path. This is 955 This request tries to open, fsync and close the given path. This is
732 a composite request intended to sync directories after directory 956 a composite request intended to sync directories after directory
733 operations (E.g. rename). This might not work on all operating 957 operations (E.g. rename). This might not work on all operating
734 systems or have any specific effect, but usually it makes sure that 958 systems or have any specific effect, but usually it makes sure that
735 directory changes get written to disc. It works for anything that 959 directory changes get written to disc. It works for anything that
… …
738 Future versions of this function might fall back to other methods 962 Future versions of this function might fall back to other methods
739 when "fsync" on the directory fails (such as calling "sync"). 963 when "fsync" on the directory fails (such as calling "sync").
740 964
741 Passes 0 when everything went ok, and -1 on error. 965 Passes 0 when everything went ok, and -1 on error.
742 966
743 aio_msync $scalar, $offset = 0, $length = undef, flags = 0, 967 aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC,
744 $callback->($status) 968 $callback->($status)
745 This is a rather advanced IO::AIO call, which only works on 969 This is a rather advanced IO::AIO call, which only works on
746 mmap(2)ed scalars (see the "IO::AIO::mmap" function, although it 970 mmap(2)ed scalars (see the "IO::AIO::mmap" function, although it
747 also works on data scalars managed by the Sys::Mmap or Mmap modules, 971 also works on data scalars managed by the Sys::Mmap or Mmap modules,
748 note that the scalar must only be modified in-place while an aio 972 note that the scalar must only be modified in-place while an aio
… …
750 974
751 It calls the "msync" function of your OS, if available, with the 975 It calls the "msync" function of your OS, if available, with the
752 memory area starting at $offset in the string and ending $length 976 memory area starting at $offset in the string and ending $length
753 bytes later. If $length is negative, counts from the end, and if 977 bytes later. If $length is negative, counts from the end, and if
754 $length is "undef", then it goes till the end of the string. The 978 $length is "undef", then it goes till the end of the string. The
755 flags can be a combination of "IO::AIO::MS_ASYNC", 979 flags can be either "IO::AIO::MS_ASYNC" or "IO::AIO::MS_SYNC", plus
756 "IO::AIO::MS_INVALIDATE" and "IO::AIO::MS_SYNC". 980 an optional "IO::AIO::MS_INVALIDATE".
757 981
758 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, 982 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0,
759 $callback->($status) 983 $callback->($status)
760 This is a rather advanced IO::AIO call, which works best on 984 This is a rather advanced IO::AIO call, which works best on
761 mmap(2)ed scalars. 985 mmap(2)ed scalars.
762 986
763 It touches (reads or writes) all memory pages in the specified range 987 It touches (reads or writes) all memory pages in the specified range
764 inside the scalar. All caveats and parameters are the same as for 988 inside the scalar. All caveats and parameters are the same as for
765 "aio_msync", above, except for flags, which must be either 0 (which 989 "aio_msync", above, except for flags, which must be either 0 (which
766 reads all pages and ensures they are instantiated) or 990 reads all pages and ensures they are instantiated) or
767 "IO::AIO::MT_MODIFY", which modifies the memory page s(by reading 991 "IO::AIO::MT_MODIFY", which modifies the memory pages (by reading
768 and writing an octet from it, which dirties the page). 992 and writing an octet from it, which dirties the page).
769 993
770 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status) 994 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
771 This is a rather advanced IO::AIO call, which works best on 995 This is a rather advanced IO::AIO call, which works best on
772 mmap(2)ed scalars. 996 mmap(2)ed scalars.
… …
792 IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh; 1016 IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
793 aio_mlock $data; # mlock in background 1017 aio_mlock $data; # mlock in background
794 1018
795 aio_mlockall $flags, $callback->($status) 1019 aio_mlockall $flags, $callback->($status)
796 Calls the "mlockall" function with the given $flags (a combination 1020 Calls the "mlockall" function with the given $flags (a combination
797 of "IO::AIO::MCL_CURRENT" and "IO::AIO::MCL_FUTURE"). 1021 of "IO::AIO::MCL_CURRENT", "IO::AIO::MCL_FUTURE" and
1022 "IO::AIO::MCL_ONFAULT").
798 1023
799 On systems that do not implement "mlockall", this function returns 1024 On systems that do not implement "mlockall", this function returns
800 -1 and sets errno to "ENOSYS". 1025 -1 and sets errno to "ENOSYS". Similarly, flag combinations not
1026 supported by the system result in a return value of -1 with errno
1027 being set to "EINVAL".
801 1028
802 Note that the corresponding "munlockall" is synchronous and is 1029 Note that the corresponding "munlockall" is synchronous and is
803 documented under "MISCELLANEOUS FUNCTIONS". 1030 documented under "MISCELLANEOUS FUNCTIONS".
804 1031
805 Example: asynchronously lock all current and future pages into 1032 Example: asynchronously lock all current and future pages into
806 memory. 1033 memory.
807 1034
808 aio_mlockall IO::AIO::MCL_FUTURE; 1035 aio_mlockall IO::AIO::MCL_FUTURE;
1036
1037 aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
1038 Queries the extents of the given file (by calling the Linux "FIEMAP"
1039 ioctl, see <http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for
1040 details). If the ioctl is not available on your OS, then this
1041 request will fail with "ENOSYS".
1042
1043 $start is the starting offset to query extents for, $length is the
1044 size of the range to query - if it is "undef", then the whole file
1045 will be queried.
1046
1047 $flags is a combination of flags ("IO::AIO::FIEMAP_FLAG_SYNC" or
1048 "IO::AIO::FIEMAP_FLAG_XATTR" - "IO::AIO::FIEMAP_FLAGS_COMPAT" is
1049 also exported), and is normally 0 or "IO::AIO::FIEMAP_FLAG_SYNC" to
1050 query the data portion.
1051
1052 $count is the maximum number of extent records to return. If it is
1053 "undef", then IO::AIO queries all extents of the range. As a very
1054 special case, if it is 0, then the callback receives the number of
1055 extents instead of the extents themselves (which is unreliable, see
1056 below).
1057
1058 If an error occurs, the callback receives no arguments. The special
1059 "errno" value "IO::AIO::EBADR" is available to test for flag errors.
1060
1061 Otherwise, the callback receives an array reference with extent
1062 structures. Each extent structure is an array reference itself, with
1063 the following members:
1064
1065 [$logical, $physical, $length, $flags]
1066
1067 Flags is any combination of the following flag values (typically
1068 either 0 or "IO::AIO::FIEMAP_EXTENT_LAST" (1)):
1069
1070 "IO::AIO::FIEMAP_EXTENT_LAST", "IO::AIO::FIEMAP_EXTENT_UNKNOWN",
1071 "IO::AIO::FIEMAP_EXTENT_DELALLOC", "IO::AIO::FIEMAP_EXTENT_ENCODED",
1072 "IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED",
1073 "IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED",
1074 "IO::AIO::FIEMAP_EXTENT_DATA_INLINE",
1075 "IO::AIO::FIEMAP_EXTENT_DATA_TAIL",
1076 "IO::AIO::FIEMAP_EXTENT_UNWRITTEN", "IO::AIO::FIEMAP_EXTENT_MERGED"
1077 or "IO::AIO::FIEMAP_EXTENT_SHARED".
1078
1079 At the time of this writing (Linux 3.2), this request is unreliable
1080 unless $count is "undef", as the kernel has all sorts of bugs
1081 preventing it to return all extents of a range for files with a
1082 large number of extents. The code (only) works around all these
1083 issues if $count is "undef".
809 1084
810 aio_group $callback->(...) 1085 aio_group $callback->(...)
811 This is a very special aio request: Instead of doing something, it 1086 This is a very special aio request: Instead of doing something, it
812 is a container for other aio requests, which is useful if you want 1087 is a container for other aio requests, which is useful if you want
813 to bundle many requests into a single, composite, request with a 1088 to bundle many requests into a single, composite, request with a
… …
847 While it is theoretically handy to have simple I/O scheduling 1122 While it is theoretically handy to have simple I/O scheduling
848 requests like sleep and file handle readable/writable, the overhead 1123 requests like sleep and file handle readable/writable, the overhead
849 this creates is immense (it blocks a thread for a long time) so do 1124 this creates is immense (it blocks a thread for a long time) so do
850 not use this function except to put your application under 1125 not use this function except to put your application under
851 artificial I/O pressure. 1126 artificial I/O pressure.
1127
1128 IO::AIO::WD - multiple working directories
1129 Your process only has one current working directory, which is used by
1130 all threads. This makes it hard to use relative paths (some other
1131 component could call "chdir" at any time, and it is hard to control when
1132 the path will be used by IO::AIO).
1133
1134 One solution for this is to always use absolute paths. This usually
1135 works, but can be quite slow (the kernel has to walk the whole path on
1136 every access), and can also be a hassle to implement.
1137
1138 Newer POSIX systems have a number of functions (openat, fdopendir,
1139 futimensat and so on) that make it possible to specify working
1140 directories per operation.
1141
1142 For portability, and because the clowns who "designed", or shall I
1143 write, perpetrated this new interface were obviously half-drunk, this
1144 abstraction cannot be perfect, though.
1145
1146 IO::AIO allows you to convert directory paths into a so-called
1147 IO::AIO::WD object. This object stores the canonicalised, absolute
1148 version of the path, and on systems that allow it, also a directory file
1149 descriptor.
1150
1151 Everywhere where a pathname is accepted by IO::AIO (e.g. in "aio_stat"
1152 or "aio_unlink"), one can specify an array reference with an IO::AIO::WD
1153 object and a pathname instead (or the IO::AIO::WD object alone, which
1154 gets interpreted as "[$wd, "."]"). If the pathname is absolute, the
1155 IO::AIO::WD object is ignored, otherwise the pathname is resolved
1156 relative to that IO::AIO::WD object.
1157
1158 For example, to get a wd object for /etc and then stat passwd inside,
1159 you would write:
1160
1161 aio_wd "/etc", sub {
1162 my $etcdir = shift;
1163
1164 # although $etcdir can be undef on error, there is generally no reason
1165 # to check for errors here, as aio_stat will fail with ENOENT
1166 # when $etcdir is undef.
1167
1168 aio_stat [$etcdir, "passwd"], sub {
1169 # yay
1170 };
1171 };
1172
1173 The fact that "aio_wd" is a request and not a normal function shows that
1174 creating an IO::AIO::WD object is itself a potentially blocking
1175 operation, which is why it is done asynchronously.
1176
1177 To stat the directory obtained with "aio_wd" above, one could write
1178 either of the following three request calls:
1179
1180 aio_lstat "/etc" , sub { ... # pathname as normal string
1181 aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
1182 aio_lstat $wd , sub { ... # shorthand for the previous
1183
1184 As with normal pathnames, IO::AIO keeps a copy of the working directory
1185 object and the pathname string, so you could write the following without
1186 causing any issues due to $path getting reused:
1187
1188 my $path = [$wd, undef];
1189
1190 for my $name (qw(abc def ghi)) {
1191 $path->[1] = $name;
1192 aio_stat $path, sub {
1193 # ...
1194 };
1195 }
1196
1197 There are some caveats: when directories get renamed (or deleted), the
1198 pathname string doesn't change, so will point to the new directory (or
1199 nowhere at all), while the directory fd, if available on the system,
1200 will still point to the original directory. Most functions accepting a
1201 pathname will use the directory fd on newer systems, and the string on
1202 older systems. Some functions (such as "aio_realpath") will always rely
1203 on the string form of the pathname.
1204
1205 So this functionality is mainly useful to get some protection against
1206 "chdir", to easily get an absolute path out of a relative path for
1207 future reference, and to speed up doing many operations in the same
1208 directory (e.g. when stat'ing all files in a directory).
1209
1210 The following functions implement this working directory abstraction:
1211
1212 aio_wd $pathname, $callback->($wd)
1213 Asynchonously canonicalise the given pathname and convert it to an
1214 IO::AIO::WD object representing it. If possible and supported on the
1215 system, also open a directory fd to speed up pathname resolution
1216 relative to this working directory.
1217
1218 If something goes wrong, then "undef" is passwd to the callback
1219 instead of a working directory object and $! is set appropriately.
1220 Since passing "undef" as working directory component of a pathname
1221 fails the request with "ENOENT", there is often no need for error
1222 checking in the "aio_wd" callback, as future requests using the
1223 value will fail in the expected way.
1224
1225 IO::AIO::CWD
1226 This is a compiletime constant (object) that represents the process
1227 current working directory.
1228
1229 Specifying this object as working directory object for a pathname is
1230 as if the pathname would be specified directly, without a directory
1231 object. For example, these calls are functionally identical:
1232
1233 aio_stat "somefile", sub { ... };
1234 aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
1235
1236 To recover the path associated with an IO::AIO::WD object, you can use
1237 "aio_realpath":
1238
1239 aio_realpath $wd, sub {
1240 warn "path is $_[0]\n";
1241 };
1242
1243 Currently, "aio_statvfs" always, and "aio_rename" and "aio_rmdir"
1244 sometimes, fall back to using an absolue path.
852 1245
853 IO::AIO::REQ CLASS 1246 IO::AIO::REQ CLASS
854 All non-aggregate "aio_*" functions return an object of this class when 1247 All non-aggregate "aio_*" functions return an object of this class when
855 called in non-void context. 1248 called in non-void context.
856 1249
… …
956 Sets a feeder/generator on this group: every group can have an 1349 Sets a feeder/generator on this group: every group can have an
957 attached generator that generates requests if idle. The idea behind 1350 attached generator that generates requests if idle. The idea behind
958 this is that, although you could just queue as many requests as you 1351 this is that, although you could just queue as many requests as you
959 want in a group, this might starve other requests for a potentially 1352 want in a group, this might starve other requests for a potentially
960 long time. For example, "aio_scandir" might generate hundreds of 1353 long time. For example, "aio_scandir" might generate hundreds of
961 thousands "aio_stat" requests, delaying any later requests for a 1354 thousands of "aio_stat" requests, delaying any later requests for a
962 long time. 1355 long time.
963 1356
964 To avoid this, and allow incremental generation of requests, you can 1357 To avoid this, and allow incremental generation of requests, you can
965 instead a group and set a feeder on it that generates those 1358 instead a group and set a feeder on it that generates those
966 requests. The feed callback will be called whenever there are few 1359 requests. The feed callback will be called whenever there are few
… …
1008 results. 1401 results.
1009 1402
1010 See "poll_cb" for an example. 1403 See "poll_cb" for an example.
1011 1404
1012 IO::AIO::poll_cb 1405 IO::AIO::poll_cb
1013 Process some outstanding events on the result pipe. You have to call 1406 Process some requests that have reached the result phase (i.e. they
1014 this regularly. Returns 0 if all events could be processed, or -1 if 1407 have been executed but the results are not yet reported). You have
1015 it returned earlier for whatever reason. Returns immediately when no 1408 to call this "regularly" to finish outstanding requests.
1016 events are outstanding. The amount of events processed depends on
1017 the settings of "IO::AIO::max_poll_req" and
1018 "IO::AIO::max_poll_time".
1019 1409
1410 Returns 0 if all events could be processed (or there were no events
1411 to process), or -1 if it returned earlier for whatever reason.
1412 Returns immediately when no events are outstanding. The amount of
1413 events processed depends on the settings of "IO::AIO::max_poll_req",
1414 "IO::AIO::max_poll_time" and "IO::AIO::max_outstanding".
1415
1020 If not all requests were processed for whatever reason, the 1416 If not all requests were processed for whatever reason, the poll
1021 filehandle will still be ready when "poll_cb" returns, so normally 1417 file descriptor will still be ready when "poll_cb" returns, so
1022 you don't have to do anything special to have it called later. 1418 normally you don't have to do anything special to have it called
1419 later.
1420
1421 Apart from calling "IO::AIO::poll_cb" when the event filehandle
1422 becomes ready, it can be beneficial to call this function from loops
1423 which submit a lot of requests, to make sure the results get
1424 processed when they become available and not just when the loop is
1425 finished and the event loop takes over again. This function returns
1426 very fast when there are no outstanding requests.
1023 1427
1024 Example: Install an Event watcher that automatically calls 1428 Example: Install an Event watcher that automatically calls
1025 IO::AIO::poll_cb with high priority (more examples can be found in 1429 IO::AIO::poll_cb with high priority (more examples can be found in
1026 the SYNOPSIS section, at the top of this document): 1430 the SYNOPSIS section, at the top of this document):
1027 1431
1028 Event->io (fd => IO::AIO::poll_fileno, 1432 Event->io (fd => IO::AIO::poll_fileno,
1029 poll => 'r', async => 1, 1433 poll => 'r', async => 1,
1030 cb => \&IO::AIO::poll_cb); 1434 cb => \&IO::AIO::poll_cb);
1031 1435
1032 IO::AIO::poll_wait 1436 IO::AIO::poll_wait
1033 If there are any outstanding requests and none of them in the result 1437 Wait until either at least one request is in the result phase or no
1034 phase, wait till the result filehandle becomes ready for reading 1438 requests are outstanding anymore.
1035 (simply does a "select" on the filehandle. This is useful if you 1439
1036 want to synchronously wait for some requests to finish). 1440 This is useful if you want to synchronously wait for some requests
1441 to become ready, without actually handling them.
1037 1442
1038 See "nreqs" for an example. 1443 See "nreqs" for an example.
1039 1444
1040 IO::AIO::poll 1445 IO::AIO::poll
1041 Waits until some requests have been handled. 1446 Waits until some requests have been handled.
… …
1050 1455
1051 Strictly equivalent to: 1456 Strictly equivalent to:
1052 1457
1053 IO::AIO::poll_wait, IO::AIO::poll_cb 1458 IO::AIO::poll_wait, IO::AIO::poll_cb
1054 while IO::AIO::nreqs; 1459 while IO::AIO::nreqs;
1460
1461 This function can be useful at program aborts, to make sure
1462 outstanding I/O has been done ("IO::AIO" uses an "END" block which
1463 already calls this function on normal exits), or when you are merely
1464 using "IO::AIO" for its more advanced functions, rather than for
1465 async I/O, e.g.:
1466
1467 my ($dirs, $nondirs);
1468 IO::AIO::aio_scandir "/tmp", 0, sub { ($dirs, $nondirs) = @_ };
1469 IO::AIO::flush;
1470 # $dirs, $nondirs are now set
1055 1471
1056 IO::AIO::max_poll_reqs $nreqs 1472 IO::AIO::max_poll_reqs $nreqs
1057 IO::AIO::max_poll_time $seconds 1473 IO::AIO::max_poll_time $seconds
1058 These set the maximum number of requests (default 0, meaning 1474 These set the maximum number of requests (default 0, meaning
1059 infinity) that are being processed by "IO::AIO::poll_cb" in one 1475 infinity) that are being processed by "IO::AIO::poll_cb" in one
… …
1121 1537
1122 Under normal circumstances you don't need to call this function. 1538 Under normal circumstances you don't need to call this function.
1123 1539
1124 IO::AIO::max_idle $nthreads 1540 IO::AIO::max_idle $nthreads
1125 Limit the number of threads (default: 4) that are allowed to idle 1541 Limit the number of threads (default: 4) that are allowed to idle
1126 (i.e., threads that did not get a request to process within 10 1542 (i.e., threads that did not get a request to process within the idle
1127 seconds). That means if a thread becomes idle while $nthreads other 1543 timeout (default: 10 seconds). That means if a thread becomes idle
1128 threads are also idle, it will free its resources and exit. 1544 while $nthreads other threads are also idle, it will free its
1545 resources and exit.
1129 1546
1130 This is useful when you allow a large number of threads (e.g. 100 or 1547 This is useful when you allow a large number of threads (e.g. 100 or
1131 1000) to allow for extremely high load situations, but want to free 1548 1000) to allow for extremely high load situations, but want to free
1132 resources under normal circumstances (1000 threads can easily 1549 resources under normal circumstances (1000 threads can easily
1133 consume 30MB of RAM). 1550 consume 30MB of RAM).
1134 1551
1135 The default is probably ok in most situations, especially if thread 1552 The default is probably ok in most situations, especially if thread
1136 creation is fast. If thread creation is very slow on your system you 1553 creation is fast. If thread creation is very slow on your system you
1137 might want to use larger values. 1554 might want to use larger values.
1138 1555
1556 IO::AIO::idle_timeout $seconds
1557 Sets the minimum idle timeout (default 10) after which worker
1558 threads are allowed to exit. SEe "IO::AIO::max_idle".
1559
1139 IO::AIO::max_outstanding $maxreqs 1560 IO::AIO::max_outstanding $maxreqs
1561 Sets the maximum number of outstanding requests to $nreqs. If you do
1562 queue up more than this number of requests, the next call to
1563 "IO::AIO::poll_cb" (and other functions calling "poll_cb", such as
1564 "IO::AIO::flush" or "IO::AIO::poll") will block until the limit is
1565 no longer exceeded.
1566
1567 In other words, this setting does not enforce a queue limit, but can
1568 be used to make poll functions block if the limit is exceeded.
1569
1140 This is a very bad function to use in interactive programs because 1570 This is a very bad function to use in interactive programs because
1141 it blocks, and a bad way to reduce concurrency because it is 1571 it blocks, and a bad way to reduce concurrency because it is
1142 inexact: Better use an "aio_group" together with a feed callback. 1572 inexact: Better use an "aio_group" together with a feed callback.
1143 1573
1144 Sets the maximum number of outstanding requests to $nreqs. If you do 1574 Its main use is in scripts without an event loop - when you want to
1145 queue up more than this number of requests, the next call to the 1575 stat a lot of files, you can write something like this:
1146 "poll_cb" (and "poll_some" and other functions calling "poll_cb")
1147 function will block until the limit is no longer exceeded.
1148 1576
1149 The default value is very large, so there is no practical limit on 1577 IO::AIO::max_outstanding 32;
1578
1579 for my $path (...) {
1580 aio_stat $path , ...;
1581 IO::AIO::poll_cb;
1582 }
1583
1584 IO::AIO::flush;
1585
1586 The call to "poll_cb" inside the loop will normally return
1587 instantly, but as soon as more thna 32 reqeusts are in-flight, it
1588 will block until some requests have been handled. This keeps the
1589 loop from pushing a large number of "aio_stat" requests onto the
1590 queue.
1591
1592 The default value for "max_outstanding" is very large, so there is
1150 the number of outstanding requests. 1593 no practical limit on the number of outstanding requests.
1151
1152 You can still queue as many requests as you want. Therefore,
1153 "max_outstanding" is mainly useful in simple scripts (with low
1154 values) or as a stop gap to shield against fatal memory overflow
1155 (with large values).
1156 1594
1157 STATISTICAL INFORMATION 1595 STATISTICAL INFORMATION
1158 IO::AIO::nreqs 1596 IO::AIO::nreqs
1159 Returns the number of requests currently in the ready, execute or 1597 Returns the number of requests currently in the ready, execute or
1160 pending states (i.e. for which their callback has not been invoked 1598 pending states (i.e. for which their callback has not been invoked
… …
1171 1609
1172 IO::AIO::npending 1610 IO::AIO::npending
1173 Returns the number of requests currently in the pending state 1611 Returns the number of requests currently in the pending state
1174 (executed, but not yet processed by poll_cb). 1612 (executed, but not yet processed by poll_cb).
1175 1613
1614 SUBSECOND STAT TIME ACCESS
1615 Both "aio_stat"/"aio_lstat" and perl's "stat"/"lstat" functions can
1616 generally find access/modification and change times with subsecond time
1617 accuracy of the system supports it, but perl's built-in functions only
1618 return the integer part.
1619
1620 The following functions return the timestamps of the most recent stat
1621 with subsecond precision on most systems and work both after
1622 "aio_stat"/"aio_lstat" and perl's "stat"/"lstat" calls. Their return
1623 value is only meaningful after a successful "stat"/"lstat" call, or
1624 during/after a successful "aio_stat"/"aio_lstat" callback.
1625
1626 This is similar to the Time::HiRes "stat" functions, but can return full
1627 resolution without rounding and work with standard perl "stat",
1628 alleviating the need to call the special "Time::HiRes" functions, which
1629 do not act like their perl counterparts.
1630
1631 On operating systems or file systems where subsecond time resolution is
1632 not supported or could not be detected, a fractional part of 0 is
1633 returned, so it is always safe to call these functions.
1634
1635 $seconds = IO::AIO::st_atime, IO::AIO::st_mtime, IO::AIO::st_ctime,
1636 IO::AIO::st_btime
1637 Return the access, modication, change or birth time, respectively,
1638 including fractional part. Due to the limited precision of floating
1639 point, the accuracy on most platforms is only a bit better than
1640 milliseconds for times around now - see the *nsec* function family,
1641 below, for full accuracy.
1642
1643 File birth time is only available when the OS and perl support it
1644 (on FreeBSD and NetBSD at the time of this writing, although support
1645 is adaptive, so if your OS/perl gains support, IO::AIO can take
1646 avdantage of it). On systems where it isn't available, 0 is
1647 currently returned, but this might change to "undef" in a future
1648 version.
1649
1650 ($atime, $mtime, $ctime, $btime, ...) = IO::AIO::st_xtime
1651 Returns access, modification, change and birth time all in one go,
1652 and maybe more times in the future version.
1653
1654 $nanoseconds = IO::AIO::st_atimensec, IO::AIO::st_mtimensec,
1655 IO::AIO::st_ctimensec, IO::AIO::st_btimensec
1656 Return the fractional access, modifcation, change or birth time, in
1657 nanoseconds, as an integer in the range 0 to 999999999.
1658
1659 Note that no accessors are provided for access, modification and
1660 change times - you need to get those from "stat _" if required ("int
1661 IO::AIO::st_atime" and so on will *not* generally give you the
1662 correct value).
1663
1664 $seconds = IO::AIO::st_btimesec
1665 The (integral) seconds part of the file birth time, if available.
1666
1667 ($atime, $mtime, $ctime, $btime, ...) = IO::AIO::st_xtimensec
1668 Like the functions above, but returns all four times in one go (and
1669 maybe more in future versions).
1670
1671 $counter = IO::AIO::st_gen
1672 Returns the generation counter (in practice this is just a random
1673 number) of the file. This is only available on platforms which have
1674 this member in their "struct stat" (most BSDs at the time of this
1675 writing) and generally only to the root usert. If unsupported, 0 is
1676 returned, but this might change to "undef" in a future version.
1677
1678 Example: print the high resolution modification time of /etc, using
1679 "stat", and "IO::AIO::aio_stat".
1680
1681 if (stat "/etc") {
1682 printf "stat(/etc) mtime: %f\n", IO::AIO::st_mtime;
1683 }
1684
1685 IO::AIO::aio_stat "/etc", sub {
1686 $_[0]
1687 and return;
1688
1689 printf "aio_stat(/etc) mtime: %d.%09d\n", (stat _)[9], IO::AIO::st_mtimensec;
1690 };
1691
1692 IO::AIO::flush;
1693
1694 Output of the awbove on my system, showing reduced and full accuracy:
1695
1696 stat(/etc) mtime: 1534043702.020808
1697 aio_stat(/etc) mtime: 1534043702.020807792
1698
1176 MISCELLANEOUS FUNCTIONS 1699 MISCELLANEOUS FUNCTIONS
1177 IO::AIO implements some functions that might be useful, but are not 1700 IO::AIO implements some functions that are useful when you want to use
1178 asynchronous. 1701 some "Advanced I/O" function not available to in Perl, without going the
1702 "Asynchronous I/O" route. Many of these have an asynchronous "aio_*"
1703 counterpart.
1704
1705 $numfd = IO::AIO::get_fdlimit
1706 This function is *EXPERIMENTAL* and subject to change.
1707
1708 Tries to find the current file descriptor limit and returns it, or
1709 "undef" and sets $! in case of an error. The limit is one larger
1710 than the highest valid file descriptor number.
1711
1712 IO::AIO::min_fdlimit [$numfd]
1713 This function is *EXPERIMENTAL* and subject to change.
1714
1715 Try to increase the current file descriptor limit(s) to at least
1716 $numfd by changing the soft or hard file descriptor resource limit.
1717 If $numfd is missing, it will try to set a very high limit, although
1718 this is not recommended when you know the actual minimum that you
1719 require.
1720
1721 If the limit cannot be raised enough, the function makes a
1722 best-effort attempt to increase the limit as much as possible, using
1723 various tricks, while still failing. You can query the resulting
1724 limit using "IO::AIO::get_fdlimit".
1725
1726 If an error occurs, returns "undef" and sets $!, otherwise returns
1727 true.
1179 1728
1180 IO::AIO::sendfile $ofh, $ifh, $offset, $count 1729 IO::AIO::sendfile $ofh, $ifh, $offset, $count
1181 Calls the "eio_sendfile_sync" function, which is like 1730 Calls the "eio_sendfile_sync" function, which is like
1182 "aio_sendfile", but is blocking (this makes most sense if you know 1731 "aio_sendfile", but is blocking (this makes most sense if you know
1183 the input data is likely cached already and the output filehandle is 1732 the input data is likely cached already and the output filehandle is
… …
1185 1734
1186 Returns the number of bytes copied, or -1 on error. 1735 Returns the number of bytes copied, or -1 on error.
1187 1736
1188 IO::AIO::fadvise $fh, $offset, $len, $advice 1737 IO::AIO::fadvise $fh, $offset, $len, $advice
1189 Simply calls the "posix_fadvise" function (see its manpage for 1738 Simply calls the "posix_fadvise" function (see its manpage for
1190 details). The following advice constants are avaiable: 1739 details). The following advice constants are available:
1191 "IO::AIO::FADV_NORMAL", "IO::AIO::FADV_SEQUENTIAL", 1740 "IO::AIO::FADV_NORMAL", "IO::AIO::FADV_SEQUENTIAL",
1192 "IO::AIO::FADV_RANDOM", "IO::AIO::FADV_NOREUSE", 1741 "IO::AIO::FADV_RANDOM", "IO::AIO::FADV_NOREUSE",
1193 "IO::AIO::FADV_WILLNEED", "IO::AIO::FADV_DONTNEED". 1742 "IO::AIO::FADV_WILLNEED", "IO::AIO::FADV_DONTNEED".
1194 1743
1195 On systems that do not implement "posix_fadvise", this function 1744 On systems that do not implement "posix_fadvise", this function
1196 returns ENOSYS, otherwise the return value of "posix_fadvise". 1745 returns ENOSYS, otherwise the return value of "posix_fadvise".
1197 1746
1198 IO::AIO::madvise $scalar, $offset, $len, $advice 1747 IO::AIO::madvise $scalar, $offset, $len, $advice
1199 Simply calls the "posix_madvise" function (see its manpage for 1748 Simply calls the "posix_madvise" function (see its manpage for
1200 details). The following advice constants are avaiable: 1749 details). The following advice constants are available:
1201 "IO::AIO::MADV_NORMAL", "IO::AIO::MADV_SEQUENTIAL", 1750 "IO::AIO::MADV_NORMAL", "IO::AIO::MADV_SEQUENTIAL",
1202 "IO::AIO::MADV_RANDOM", "IO::AIO::MADV_WILLNEED", 1751 "IO::AIO::MADV_RANDOM", "IO::AIO::MADV_WILLNEED",
1203 "IO::AIO::MADV_DONTNEED". 1752 "IO::AIO::MADV_DONTNEED".
1204 1753
1754 If $offset is negative, counts from the end. If $length is negative,
1755 the remaining length of the $scalar is used. If possible, $length
1756 will be reduced to fit into the $scalar.
1757
1205 On systems that do not implement "posix_madvise", this function 1758 On systems that do not implement "posix_madvise", this function
1206 returns ENOSYS, otherwise the return value of "posix_madvise". 1759 returns ENOSYS, otherwise the return value of "posix_madvise".
1207 1760
1208 IO::AIO::mprotect $scalar, $offset, $len, $protect 1761 IO::AIO::mprotect $scalar, $offset, $len, $protect
1209 Simply calls the "mprotect" function on the preferably AIO::mmap'ed 1762 Simply calls the "mprotect" function on the preferably AIO::mmap'ed
1210 $scalar (see its manpage for details). The following protect 1763 $scalar (see its manpage for details). The following protect
1211 constants are avaiable: "IO::AIO::PROT_NONE", "IO::AIO::PROT_READ", 1764 constants are available: "IO::AIO::PROT_NONE", "IO::AIO::PROT_READ",
1212 "IO::AIO::PROT_WRITE", "IO::AIO::PROT_EXEC". 1765 "IO::AIO::PROT_WRITE", "IO::AIO::PROT_EXEC".
1766
1767 If $offset is negative, counts from the end. If $length is negative,
1768 the remaining length of the $scalar is used. If possible, $length
1769 will be reduced to fit into the $scalar.
1213 1770
1214 On systems that do not implement "mprotect", this function returns 1771 On systems that do not implement "mprotect", this function returns
1215 ENOSYS, otherwise the return value of "mprotect". 1772 ENOSYS, otherwise the return value of "mprotect".
1216 1773
1217 IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset] 1774 IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
1218 Memory-maps a file (or anonymous memory range) and attaches it to 1775 Memory-maps a file (or anonymous memory range) and attaches it to
1219 the given $scalar, which will act like a string scalar. 1776 the given $scalar, which will act like a string scalar. Returns true
1777 on success, and false otherwise.
1220 1778
1779 The scalar must exist, but its contents do not matter - this means
1780 you cannot use a nonexistant array or hash element. When in doubt,
1781 "undef" the scalar first.
1782
1221 The only operations allowed on the scalar are "substr"/"vec" that 1783 The only operations allowed on the mmapped scalar are
1222 don't change the string length, and most read-only operations such 1784 "substr"/"vec", which don't change the string length, and most
1223 as copying it or searching it with regexes and so on. 1785 read-only operations such as copying it or searching it with regexes
1786 and so on.
1224 1787
1225 Anything else is unsafe and will, at best, result in memory leaks. 1788 Anything else is unsafe and will, at best, result in memory leaks.
1226 1789
1227 The memory map associated with the $scalar is automatically removed 1790 The memory map associated with the $scalar is automatically removed
1228 when the $scalar is destroyed, or when the "IO::AIO::mmap" or 1791 when the $scalar is undef'd or destroyed, or when the
1229 "IO::AIO::munmap" functions are called. 1792 "IO::AIO::mmap" or "IO::AIO::munmap" functions are called on it.
1230 1793
1231 This calls the "mmap"(2) function internally. See your system's 1794 This calls the "mmap"(2) function internally. See your system's
1232 manual page for details on the $length, $prot and $flags parameters. 1795 manual page for details on the $length, $prot and $flags parameters.
1233 1796
1234 The $length must be larger than zero and smaller than the actual 1797 The $length must be larger than zero and smaller than the actual
… …
1238 "IO::AIO::PROT_EXEC", "IO::AIO::PROT_READ" and/or 1801 "IO::AIO::PROT_EXEC", "IO::AIO::PROT_READ" and/or
1239 "IO::AIO::PROT_WRITE", 1802 "IO::AIO::PROT_WRITE",
1240 1803
1241 $flags can be a combination of "IO::AIO::MAP_SHARED" or 1804 $flags can be a combination of "IO::AIO::MAP_SHARED" or
1242 "IO::AIO::MAP_PRIVATE", or a number of system-specific flags (when 1805 "IO::AIO::MAP_PRIVATE", or a number of system-specific flags (when
1243 not available, the are defined as 0): "IO::AIO::MAP_ANONYMOUS" 1806 not available, the are 0): "IO::AIO::MAP_ANONYMOUS" (which is set to
1244 (which is set to "MAP_ANON" if your system only provides this 1807 "MAP_ANON" if your system only provides this constant),
1808 "IO::AIO::MAP_LOCKED", "IO::AIO::MAP_NORESERVE",
1245 constant), "IO::AIO::MAP_HUGETLB", "IO::AIO::MAP_LOCKED", 1809 "IO::AIO::MAP_POPULATE", "IO::AIO::MAP_NONBLOCK",
1810 "IO::AIO::MAP_FIXED", "IO::AIO::MAP_GROWSDOWN",
1246 "IO::AIO::MAP_NORESERVE", "IO::AIO::MAP_POPULATE" or 1811 "IO::AIO::MAP_32BIT", "IO::AIO::MAP_HUGETLB" or
1247 "IO::AIO::MAP_NONBLOCK" 1812 "IO::AIO::MAP_STACK".
1248 1813
1249 If $fh is "undef", then a file descriptor of -1 is passed. 1814 If $fh is "undef", then a file descriptor of -1 is passed.
1250 1815
1251 $offset is the offset from the start of the file - it generally must 1816 $offset is the offset from the start of the file - it generally must
1252 be a multiple of "IO::AIO::PAGESIZE" and defaults to 0. 1817 be a multiple of "IO::AIO::PAGESIZE" and defaults to 0.
… …
1264 1829
1265 my $fast_md5 = md5 $data; 1830 my $fast_md5 = md5 $data;
1266 1831
1267 IO::AIO::munmap $scalar 1832 IO::AIO::munmap $scalar
1268 Removes a previous mmap and undefines the $scalar. 1833 Removes a previous mmap and undefines the $scalar.
1834
1835 IO::AIO::mremap $scalar, $new_length, $flags = MREMAP_MAYMOVE[,
1836 $new_address = 0]
1837 Calls the Linux-specific mremap(2) system call. The $scalar must
1838 have been mapped by "IO::AIO::mmap", and $flags must currently
1839 either be 0 or "IO::AIO::MREMAP_MAYMOVE".
1840
1841 Returns true if successful, and false otherwise. If the underlying
1842 mmapped region has changed address, then the true value has the
1843 numerical value 1, otherwise it has the numerical value 0:
1844
1845 my $success = IO::AIO::mremap $mmapped, 8192, IO::AIO::MREMAP_MAYMOVE
1846 or die "mremap: $!";
1847
1848 if ($success*1) {
1849 warn "scalar has chanegd address in memory\n";
1850 }
1851
1852 "IO::AIO::MREMAP_FIXED" and the $new_address argument are currently
1853 implemented, but not supported and might go away in a future
1854 version.
1855
1856 On systems where this call is not supported or is not emulated, this
1857 call returns falls and sets $! to "ENOSYS".
1858
1859 IO::AIO::mlockall $flags
1860 Calls the "eio_mlockall_sync" function, which is like
1861 "aio_mlockall", but is blocking.
1269 1862
1270 IO::AIO::munlock $scalar, $offset = 0, $length = undef 1863 IO::AIO::munlock $scalar, $offset = 0, $length = undef
1271 Calls the "munlock" function, undoing the effects of a previous 1864 Calls the "munlock" function, undoing the effects of a previous
1272 "aio_mlock" call (see its description for details). 1865 "aio_mlock" call (see its description for details).
1273 1866
1274 IO::AIO::munlockall 1867 IO::AIO::munlockall
1275 Calls the "munlockall" function. 1868 Calls the "munlockall" function.
1276 1869
1277 On systems that do not implement "munlockall", this function returns 1870 On systems that do not implement "munlockall", this function returns
1278 ENOSYS, otherwise the return value of "munlockall". 1871 ENOSYS, otherwise the return value of "munlockall".
1872
1873 IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
1874 Calls the GNU/Linux splice(2) syscall, if available. If $r_off or
1875 $w_off are "undef", then "NULL" is passed for these, otherwise they
1876 should be the file offset.
1877
1878 $r_fh and $w_fh should not refer to the same file, as splice might
1879 silently corrupt the data in this case.
1880
1881 The following symbol flag values are available:
1882 "IO::AIO::SPLICE_F_MOVE", "IO::AIO::SPLICE_F_NONBLOCK",
1883 "IO::AIO::SPLICE_F_MORE" and "IO::AIO::SPLICE_F_GIFT".
1884
1885 See the splice(2) manpage for details.
1886
1887 IO::AIO::tee $r_fh, $w_fh, $length, $flags
1888 Calls the GNU/Linux tee(2) syscall, see its manpage and the
1889 description for "IO::AIO::splice" above for details.
1890
1891 $actual_size = IO::AIO::pipesize $r_fh[, $new_size]
1892 Attempts to query or change the pipe buffer size. Obviously works
1893 only on pipes, and currently works only on GNU/Linux systems, and
1894 fails with -1/"ENOSYS" everywhere else. If anybody knows how to
1895 influence pipe buffer size on other systems, drop me a note.
1896
1897 ($rfh, $wfh) = IO::AIO::pipe2 [$flags]
1898 This is a direct interface to the Linux pipe2(2) system call. If
1899 $flags is missing or 0, then this should be the same as a call to
1900 perl's built-in "pipe" function and create a new pipe, and works on
1901 systems that lack the pipe2 syscall. On win32, this case invokes
1902 "_pipe (..., 4096, O_BINARY)".
1903
1904 If $flags is non-zero, it tries to invoke the pipe2 system call with
1905 the given flags (Linux 2.6.27, glibc 2.9).
1906
1907 On success, the read and write file handles are returned.
1908
1909 On error, nothing will be returned. If the pipe2 syscall is missing
1910 and $flags is non-zero, fails with "ENOSYS".
1911
1912 Please refer to pipe2(2) for more info on the $flags, but at the
1913 time of this writing, "IO::AIO::O_CLOEXEC", "IO::AIO::O_NONBLOCK"
1914 and "IO::AIO::O_DIRECT" (Linux 3.4, for packet-based pipes) were
1915 supported.
1916
1917 Example: create a pipe race-free w.r.t. threads and fork:
1918
1919 my ($rfh, $wfh) = IO::AIO::pipe2 IO::AIO::O_CLOEXEC
1920 or die "pipe2: $!\n";
1921
1922 $fh = IO::AIO::eventfd [$initval, [$flags]]
1923 This is a direct interface to the Linux eventfd(2) system call. The
1924 (unhelpful) defaults for $initval and $flags are 0 for both.
1925
1926 On success, the new eventfd filehandle is returned, otherwise
1927 returns "undef". If the eventfd syscall is missing, fails with
1928 "ENOSYS".
1929
1930 Please refer to eventfd(2) for more info on this call.
1931
1932 The following symbol flag values are available:
1933 "IO::AIO::EFD_CLOEXEC", "IO::AIO::EFD_NONBLOCK" and
1934 "IO::AIO::EFD_SEMAPHORE" (Linux 2.6.30).
1935
1936 Example: create a new eventfd filehandle:
1937
1938 $fh = IO::AIO::eventfd 0, IO::AIO::O_CLOEXEC
1939 or die "eventfd: $!\n";
1940
1941 $fh = IO::AIO::timerfd_create $clockid[, $flags]
1942 This is a direct interface to the Linux timerfd_create(2) system
1943 call. The (unhelpful) default for $flags is 0.
1944
1945 On success, the new timerfd filehandle is returned, otherwise
1946 returns "undef". If the eventfd syscall is missing, fails with
1947 "ENOSYS".
1948
1949 Please refer to timerfd_create(2) for more info on this call.
1950
1951 The following $clockid values are available:
1952 "IO::AIO::CLOCK_REALTIME", "IO::AIO::CLOCK_MONOTONIC"
1953 "IO::AIO::CLOCK_CLOCK_BOOTTIME" (Linux 3.15)
1954 "IO::AIO::CLOCK_CLOCK_REALTIME_ALARM" (Linux 3.11) and
1955 "IO::AIO::CLOCK_CLOCK_BOOTTIME_ALARM" (Linux 3.11).
1956
1957 The following $flags values are available (Linux 2.6.27):
1958 "IO::AIO::TFD_NONBLOCK" and "IO::AIO::TFD_CLOEXEC".
1959
1960 Example: create a new timerfd and set it to one-second repeated
1961 alarms, then wait for two alarms:
1962
1963 my $fh = IO::AIO::timerfd_create IO::AIO::CLOCK_BOOTTIME, IO::AIO::TFD_CLOEXEC
1964 or die "timerfd_create: $!\n";
1965
1966 defined IO::AIO::timerfd_settime $fh, 0, 1, 1
1967 or die "timerfd_settime: $!\n";
1968
1969 for (1..2) {
1970 8 == sysread $fh, my $buf, 8
1971 or die "timerfd read failure\n";
1972
1973 printf "number of expirations (likely 1): %d\n",
1974 unpack "Q", $buf;
1975 }
1976
1977 ($cur_interval, $cur_value) = IO::AIO::timerfd_settime $fh, $flags,
1978 $new_interval, $nbw_value
1979 This is a direct interface to the Linux timerfd_settime(2) system
1980 call. Please refer to its manpage for more info on this call.
1981
1982 The new itimerspec is specified using two (possibly fractional)
1983 second values, $new_interval and $new_value).
1984
1985 On success, the current interval and value are returned (as per
1986 "timerfd_gettime"). On failure, the empty list is returned.
1987
1988 The following $flags values are available:
1989 "IO::AIO::TFD_TIMER_ABSTIME" and "IO::AIO::TFD_TIMER_CANCEL_ON_SET".
1990
1991 See "IO::AIO::timerfd_create" for a full example.
1992
1993 ($cur_interval, $cur_value) = IO::AIO::timerfd_gettime $fh
1994 This is a direct interface to the Linux timerfd_gettime(2) system
1995 call. Please refer to its manpage for more info on this call.
1996
1997 On success, returns the current values of interval and value for the
1998 given timerfd (as potentially fractional second values). On failure,
1999 the empty list is returned.
1279 2000
1280EVENT LOOP INTEGRATION 2001EVENT LOOP INTEGRATION
1281 It is recommended to use AnyEvent::AIO to integrate IO::AIO 2002 It is recommended to use AnyEvent::AIO to integrate IO::AIO
1282 automatically into many event loops: 2003 automatically into many event loops:
1283 2004
… …
1306 # Danga::Socket integration 2027 # Danga::Socket integration
1307 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno => 2028 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
1308 \&IO::AIO::poll_cb); 2029 \&IO::AIO::poll_cb);
1309 2030
1310 FORK BEHAVIOUR 2031 FORK BEHAVIOUR
1311 This module should do "the right thing" when the process using it forks: 2032 Usage of pthreads in a program changes the semantics of fork
2033 considerably. Specifically, only async-safe functions can be called
2034 after fork. Perl doesn't know about this, so in general, you cannot call
2035 fork with defined behaviour in perl if pthreads are involved. IO::AIO
2036 uses pthreads, so this applies, but many other extensions and (for
2037 inexplicable reasons) perl itself often is linked against pthreads, so
2038 this limitation applies to quite a lot of perls.
1312 2039
1313 Before the fork, IO::AIO enters a quiescent state where no requests can 2040 This module no longer tries to fight your OS, or POSIX. That means
1314 be added in other threads and no results will be processed. After the 2041 IO::AIO only works in the process that loaded it. Forking is fully
1315 fork the parent simply leaves the quiescent state and continues 2042 supported, but using IO::AIO in the child is not.
1316 request/result processing, while the child frees the request/result
1317 queue (so that the requests started before the fork will only be handled
1318 in the parent). Threads will be started on demand until the limit set in
1319 the parent process has been reached again.
1320 2043
1321 In short: the parent will, after a short pause, continue as if fork had 2044 You might get around by not *using* IO::AIO before (or after) forking.
1322 not been called, while the child will act as if IO::AIO has not been 2045 You could also try to call the IO::AIO::reinit function in the child:
1323 used yet. 2046
2047 IO::AIO::reinit
2048 Abandons all current requests and I/O threads and simply
2049 reinitialises all data structures. This is not an operation
2050 supported by any standards, but happens to work on GNU/Linux and
2051 some newer BSD systems.
2052
2053 The only reasonable use for this function is to call it after
2054 forking, if "IO::AIO" was used in the parent. Calling it while
2055 IO::AIO is active in the process will result in undefined behaviour.
2056 Calling it at any time will also result in any undefined (by POSIX)
2057 behaviour.
2058
2059 LINUX-SPECIFIC CALLS
2060 When a call is documented as "linux-specific" then this means it
2061 originated on GNU/Linux. "IO::AIO" will usually try to autodetect the
2062 availability and compatibility of such calls regardless of the platform
2063 it is compiled on, so platforms such as FreeBSD which often implement
2064 these calls will work. When in doubt, call them and see if they fail wth
2065 "ENOSYS".
1324 2066
1325 MEMORY USAGE 2067 MEMORY USAGE
1326 Per-request usage: 2068 Per-request usage:
1327 2069
1328 Each aio request uses - depending on your architecture - around 100-200 2070 Each aio request uses - depending on your architecture - around 100-200
… …
1339 In the execution phase, some aio requests require more memory for 2081 In the execution phase, some aio requests require more memory for
1340 temporary buffers, and each thread requires a stack and other data 2082 temporary buffers, and each thread requires a stack and other data
1341 structures (usually around 16k-128k, depending on the OS). 2083 structures (usually around 16k-128k, depending on the OS).
1342 2084
1343KNOWN BUGS 2085KNOWN BUGS
1344 Known bugs will be fixed in the next release. 2086 Known bugs will be fixed in the next release :)
2087
2088KNOWN ISSUES
2089 Calls that try to "import" foreign memory areas (such as "IO::AIO::mmap"
2090 or "IO::AIO::aio_slurp") do not work with generic lvalues, such as
2091 non-created hash slots or other scalars I didn't think of. It's best to
2092 avoid such and either use scalar variables or making sure that the
2093 scalar exists (e.g. by storing "undef") and isn't "funny" (e.g. tied).
2094
2095 I am not sure anything can be done about this, so this is considered a
2096 known issue, rather than a bug.
1345 2097
1346SEE ALSO 2098SEE ALSO
1347 AnyEvent::AIO for easy integration into event loops, Coro::AIO for a 2099 AnyEvent::AIO for easy integration into event loops, Coro::AIO for a
1348 more natural syntax. 2100 more natural syntax.
1349 2101

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