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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", O_RDONLY, 0, sub { 7 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
8 my $fh = shift 8 my $fh = shift
9 or die "/etc/passwd: $!"; 9 or die "/etc/passwd: $!";
10 ... 10 ...
11 }; 11 };
12 12
… …
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;
75 78
76 # queue the request to open /etc/passwd 79 # queue the request to open /etc/passwd
77 aio_open "/etc/passwd", O_RDONLY, 0, sub { 80 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
78 my $fh = shift 81 my $fh = shift
79 or die "error while opening: $!"; 82 or die "error while opening: $!";
80 83
81 # stat'ing filehandles is generally non-blocking 84 # stat'ing filehandles is generally non-blocking
82 my $size = -s $fh; 85 my $size = -s $fh;
… …
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)
204 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
205 aio_mlockall $flags, $callback->($status)
192 aio_group $callback->(...) 206 aio_group $callback->(...)
193 aio_nop $callback->() 207 aio_nop $callback->()
194 208
195 $prev_pri = aioreq_pri [$pri] 209 $prev_pri = aioreq_pri [$pri]
196 aioreq_nice $pri_adjust 210 aioreq_nice $pri_adjust
… …
202 IO::AIO::max_poll_reqs $nreqs 216 IO::AIO::max_poll_reqs $nreqs
203 IO::AIO::max_poll_time $seconds 217 IO::AIO::max_poll_time $seconds
204 IO::AIO::min_parallel $nthreads 218 IO::AIO::min_parallel $nthreads
205 IO::AIO::max_parallel $nthreads 219 IO::AIO::max_parallel $nthreads
206 IO::AIO::max_idle $nthreads 220 IO::AIO::max_idle $nthreads
221 IO::AIO::idle_timeout $seconds
207 IO::AIO::max_outstanding $maxreqs 222 IO::AIO::max_outstanding $maxreqs
208 IO::AIO::nreqs 223 IO::AIO::nreqs
209 IO::AIO::nready 224 IO::AIO::nready
210 IO::AIO::npending 225 IO::AIO::npending
226 $nfd = IO::AIO::get_fdlimit [EXPERIMENTAL]
227 IO::AIO::min_fdlimit $nfd [EXPERIMENTAL]
211 228
212 IO::AIO::sendfile $ofh, $ifh, $offset, $count 229 IO::AIO::sendfile $ofh, $ifh, $offset, $count
213 IO::AIO::fadvise $fh, $offset, $len, $advice 230 IO::AIO::fadvise $fh, $offset, $len, $advice
214 IO::AIO::mlockall $flags 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]
234 IO::AIO::madvise $scalar, $offset, $length, $advice
235 IO::AIO::mprotect $scalar, $offset, $length, $protect
236 IO::AIO::munlock $scalar, $offset = 0, $length = undef
215 IO::AIO::munlockall 237 IO::AIO::munlockall
216 238
217 AIO REQUEST FUNCTIONS 239 API NOTES
218 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
219 with the same name (sans "aio_"). The arguments are similar or 241 with the same name (sans "aio_"). The arguments are similar or
220 identical, and they all accept an additional (and optional) $callback 242 identical, and they all accept an additional (and optional) $callback
221 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
222 called with the syscall return code (e.g. most syscalls return -1 on
223 error, unlike perl, which usually delivers "false") as its sole argument
224 after the given syscall has been executed asynchronously. 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".
225 252
226 All functions expecting a filehandle keep a copy of the filehandle 253 All functions expecting a filehandle keep a copy of the filehandle
227 internally until the request has finished. 254 internally until the request has finished.
228 255
229 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
230 further manipulation of those requests while they are in-flight. 257 further manipulation of those requests while they are in-flight.
231 258
232 The pathnames you pass to these routines *must* be absolute and encoded 259 The pathnames you pass to these routines *should* be absolute. The
233 as octets. The reason for the former is that at the time the request is 260 reason for this is that at the time the request is being executed, the
234 being executed, the current working directory could have changed. 261 current working directory could have changed. Alternatively, you can
235 Alternatively, you can make sure that you never change the current 262 make sure that you never change the current working directory anywhere
236 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.
237 267
238 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
239 pass in filenames you got from outside (command line, readdir etc.) 269 pass in filenames you got from outside (command line, readdir etc.)
240 without tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module 270 without tinkering, b) are in your native filesystem encoding, c) use the
241 and encode your pathnames to the locale (or other) encoding in effect in 271 Encode module and encode your pathnames to the locale (or other)
242 the user environment, d) use Glib::filename_from_unicode on unicode 272 encoding in effect in the user environment, d) use
243 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
244 contents. 274 else to ensure your scalar has the correct contents.
245 275
246 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
247 handles correctly whether it is set or not. 277 handles correctly whether it is set or not.
248 278
279 AIO REQUEST FUNCTIONS
249 $prev_pri = aioreq_pri [$pri] 280 $prev_pri = aioreq_pri [$pri]
250 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
251 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.
252 283
253 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
… …
275 Similar to "aioreq_pri", but subtracts the given value from the 306 Similar to "aioreq_pri", but subtracts the given value from the
276 current priority, so the effect is cumulative. 307 current priority, so the effect is cumulative.
277 308
278 aio_open $pathname, $flags, $mode, $callback->($fh) 309 aio_open $pathname, $flags, $mode, $callback->($fh)
279 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
280 newly created filehandle for the file. 311 newly created filehandle for the file (or "undef" in case of an
312 error).
281 313
282 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,
283 above, for an explanation. 315 above, for an explanation.
284 316
285 The $flags argument is a bitmask. See the "Fcntl" module for a list. 317 The $flags argument is a bitmask. See the "Fcntl" module for a list.
… …
292 will be modified by the umask in effect then the request is being 324 will be modified by the umask in effect then the request is being
293 executed, so better never change the umask. 325 executed, so better never change the umask.
294 326
295 Example: 327 Example:
296 328
297 aio_open "/etc/passwd", O_RDONLY, 0, sub { 329 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
298 if ($_[0]) { 330 if ($_[0]) {
299 print "open successful, fh is $_[0]\n"; 331 print "open successful, fh is $_[0]\n";
300 ... 332 ...
301 } else { 333 } else {
302 die "open failed: $!\n"; 334 die "open failed: $!\n";
303 } 335 }
304 }; 336 };
305 337
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
306 aio_close $fh, $callback->($status) 348 aio_close $fh, $callback->($status)
307 Asynchronously close a file and call the callback with the result 349 Asynchronously close a file and call the callback with the result
308 code. 350 code.
309 351
310 Unfortunately, you can't do this to perl. Perl *insists* very 352 Unfortunately, you can't do this to perl. Perl *insists* very
… …
315 will use dup2 to overwrite the file descriptor with the write-end of 357 will use dup2 to overwrite the file descriptor with the write-end of
316 a pipe (the pipe fd will be created on demand and will be cached). 358 a pipe (the pipe fd will be created on demand and will be cached).
317 359
318 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
319 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".
320 381
321 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval) 382 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
322 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval) 383 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
323 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
324 $offset into the scalar given by $data and offset $dataoffset and 385 $offset into the scalar given by $data and offset $dataoffset and
325 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
326 error, just like the syscall). 387 -1 on error, just like the syscall).
327 388
328 "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
329 offset plus the actual number of bytes read. 390 offset plus the actual number of bytes read.
330 391
331 If $offset is undefined, then the current file descriptor offset 392 If $offset is undefined, then the current file descriptor offset
… …
353 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval) 414 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
354 Tries to copy $length bytes from $in_fh to $out_fh. It starts 415 Tries to copy $length bytes from $in_fh to $out_fh. It starts
355 reading at byte offset $in_offset, and starts writing at the current 416 reading at byte offset $in_offset, and starts writing at the current
356 file offset of $out_fh. Because of that, it is not safe to issue 417 file offset of $out_fh. Because of that, it is not safe to issue
357 more than one "aio_sendfile" per $out_fh, as they will interfere 418 more than one "aio_sendfile" per $out_fh, as they will interfere
358 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.
359 421
422 Please note that "aio_sendfile" can read more bytes from $in_fh than
423 are written, and there is no way to find out how many more bytes
424 have been read from "aio_sendfile" alone, as "aio_sendfile" only
425 provides the number of bytes written to $out_fh. Only if the result
426 value equals $length one can assume that $length bytes have been
427 read.
428
429 Unlike with other "aio_" functions, it makes a lot of sense to use
430 "aio_sendfile" on non-blocking sockets, as long as one end
431 (typically the $in_fh) is a file - the file I/O will then be
432 asynchronous, while the socket I/O will be non-blocking. Note,
433 however, that you can run into a trap where "aio_sendfile" reads
434 some data with readahead, then fails to write all data, and when the
435 socket is ready the next time, the data in the cache is already
436 lost, forcing "aio_sendfile" to again hit the disk. Explicit
437 "aio_read" + "aio_write" let's you better control resource usage.
438
360 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
361 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
362 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.
363 442
364 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",
365 "ENOTSUP", "EOPNOTSUPP", "EAFNOSUPPORT", "EPROTOTYPE" or "ENOTSOCK", 444 "EINVAL", "ENOTSUP", "EOPNOTSUPP", "EAFNOSUPPORT", "EPROTOTYPE" or
366 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
367 filehandle regardless of the limitations of the operating system. 446 any type of filehandle regardless of the limitations of the
447 operating system.
368 448
369 Please note, however, that "aio_sendfile" can read more bytes from 449 As native sendfile syscalls (as practically any non-POSIX interface
370 $in_fh than are written, and there is no way to find out how many 450 hacked together in a hurry to improve benchmark numbers) tend to be
371 bytes have been read from "aio_sendfile" alone, as "aio_sendfile" 451 rather buggy on many systems, this implementation tries to work
372 only provides the number of bytes written to $out_fh. Only if the 452 around some known bugs in Linux and FreeBSD kernels (probably
373 result value equals $length one can assume that $length bytes have 453 others, too), but that might fail, so you really really should check
374 been read. 454 the return value of "aio_sendfile" - fewer bytes than expected might
455 have been transferred.
375 456
376 aio_readahead $fh,$offset,$length, $callback->($retval) 457 aio_readahead $fh,$offset,$length, $callback->($retval)
377 "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
378 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
379 $offset argument specifies the starting point from which data is to 460 $offset argument specifies the starting point from which data is to
… …
382 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
383 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
384 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
385 is left unchanged. 466 is left unchanged.
386 467
387 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
388 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
389 similar effect. 470 similar effect.
390 471
391 aio_stat $fh_or_path, $callback->($status) 472 aio_stat $fh_or_path, $callback->($status)
392 aio_lstat $fh, $callback->($status) 473 aio_lstat $fh, $callback->($status)
393 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.
394 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
395 using "stat _" or "-s _" etc... 476 available using "stat _" or "-s _" and other tests (with the
477 exception of "-B" and "-T").
396 478
397 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,
398 above, for an explanation. 480 above, for an explanation.
399 481
400 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
401 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
402 silently truncated unless perl itself is compiled with large file 484 silently truncated unless perl itself is compiled with large file
403 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".
404 498
405 Example: Print the length of /etc/passwd: 499 Example: Print the length of /etc/passwd:
406 500
407 aio_stat "/etc/passwd", sub { 501 aio_stat "/etc/passwd", sub {
408 $_[0] and die "stat failed: $!"; 502 $_[0] and die "stat failed: $!";
… …
455 aio_utime $fh_or_path, $atime, $mtime, $callback->($status) 549 aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
456 Works like perl's "utime" function (including the special case of 550 Works like perl's "utime" function (including the special case of
457 $atime and $mtime being undef). Fractional times are supported if 551 $atime and $mtime being undef). Fractional times are supported if
458 the underlying syscalls support them. 552 the underlying syscalls support them.
459 553
460 When called with a pathname, uses utimes(2) if available, otherwise 554 When called with a pathname, uses utimensat(2) or utimes(2) if
461 utime(2). If called on a file descriptor, uses futimes(2) if 555 available, otherwise utime(2). If called on a file descriptor, uses
462 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.
463 558
464 Examples: 559 Examples:
465 560
466 # set atime and mtime to current time (basically touch(1)): 561 # set atime and mtime to current time (basically touch(1)):
467 aio_utime "path", undef, undef; 562 aio_utime "path", undef, undef;
… …
481 aio_chown "path", 0, undef; 576 aio_chown "path", 0, undef;
482 577
483 aio_truncate $fh_or_path, $offset, $callback->($status) 578 aio_truncate $fh_or_path, $offset, $callback->($status)
484 Works like truncate(2) or ftruncate(2). 579 Works like truncate(2) or ftruncate(2).
485 580
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
486 aio_chmod $fh_or_path, $mode, $callback->($status) 602 aio_chmod $fh_or_path, $mode, $callback->($status)
487 Works like perl's "chmod" function. 603 Works like perl's "chmod" function.
488 604
489 aio_unlink $pathname, $callback->($status) 605 aio_unlink $pathname, $callback->($status)
490 Asynchronously unlink (delete) a file and call the callback with the 606 Asynchronously unlink (delete) a file and call the callback with the
491 result code. 607 result code.
492 608
493 aio_mknod $path, $mode, $dev, $callback->($status) 609 aio_mknod $pathname, $mode, $dev, $callback->($status)
494 [EXPERIMENTAL] 610 [EXPERIMENTAL]
495 611
496 Asynchronously create a device node (or fifo). See mknod(2). 612 Asynchronously create a device node (or fifo). See mknod(2).
497 613
498 The only (POSIX-) portable way of calling this function is: 614 The only (POSIX-) portable way of calling this function is:
499 615
500 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.
501 620
502 aio_link $srcpath, $dstpath, $callback->($status) 621 aio_link $srcpath, $dstpath, $callback->($status)
503 Asynchronously create a new link to the existing object at $srcpath 622 Asynchronously create a new link to the existing object at $srcpath
504 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.
505 624
506 aio_symlink $srcpath, $dstpath, $callback->($status) 625 aio_symlink $srcpath, $dstpath, $callback->($status)
507 Asynchronously create a new symbolic link to the existing object at 626 Asynchronously create a new symbolic link to the existing object at
508 $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
509 code. 628 code.
510 629
511 aio_readlink $path, $callback->($link) 630 aio_readlink $pathname, $callback->($link)
512 Asynchronously read the symlink specified by $path and pass it to 631 Asynchronously read the symlink specified by $path and pass it to
513 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
514 the callback. 633 the callback.
515 634
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
516 aio_rename $srcpath, $dstpath, $callback->($status) 643 aio_rename $srcpath, $dstpath, $callback->($status)
517 Asynchronously rename the object at $srcpath to $dstpath, just as 644 Asynchronously rename the object at $srcpath to $dstpath, just as
518 rename(2) and call the callback with the result code. 645 rename(2) and call the callback with the result code.
646
647 On systems that support the AIO::WD working directory abstraction
648 natively, the case "[$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".
519 665
520 aio_mkdir $pathname, $mode, $callback->($status) 666 aio_mkdir $pathname, $mode, $callback->($status)
521 Asynchronously mkdir (create) a directory and call the callback with 667 Asynchronously mkdir (create) a directory and call the callback with
522 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
523 request is executed, so do not change your umask. 669 request is executed, so do not change your umask.
524 670
525 aio_rmdir $pathname, $callback->($status) 671 aio_rmdir $pathname, $callback->($status)
526 Asynchronously rmdir (delete) a directory and call the callback with 672 Asynchronously rmdir (delete) a directory and call the callback with
527 the result code. 673 the result code.
528 674
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
529 aio_readdir $pathname, $callback->($entries) 679 aio_readdir $pathname, $callback->($entries)
530 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
531 entire directory (i.e. opendir + readdir + closedir). The entries 681 entire directory (i.e. opendir + readdir + closedir). The entries
532 will not be sorted, and will NOT include the "." and ".." entries. 682 will not be sorted, and will NOT include the "." and ".." entries.
533 683
534 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
535 an array-ref with the filenames. 685 an array-ref with the filenames.
536 686
537 aio_readdirx $pathname, $flags, $callback->($entries, $flags) 687 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
538 Quite similar to "aio_readdir", but the $flags argument allows to 688 Quite similar to "aio_readdir", but the $flags argument allows one
539 tune behaviour and output format. In case of an error, $entries will 689 to tune behaviour and output format. In case of an error, $entries
540 be "undef". 690 will be "undef".
541 691
542 The flags are a combination of the following constants, ORed 692 The flags are a combination of the following constants, ORed
543 together (the flags will also be passed to the callback, possibly 693 together (the flags will also be passed to the callback, possibly
544 modified): 694 modified):
545 695
546 IO::AIO::READDIR_DENTS 696 IO::AIO::READDIR_DENTS
547 When this flag is off, then the callback gets an arrayref with 697 Normally the callback gets an arrayref consisting of names only
548 of names only (as with "aio_readdir"), otherwise it gets an 698 (as with "aio_readdir"). If this flag is set, then the callback
549 arrayref with "[$name, $type, $inode]" arrayrefs, each 699 gets an arrayref with "[$name, $type, $inode]" arrayrefs, each
550 describing a single directory entry in more detail. 700 describing a single directory entry in more detail:
551 701
552 $name is the name of the entry. 702 $name is the name of the entry.
553 703
554 $type is one of the "IO::AIO::DT_xxx" constants: 704 $type is one of the "IO::AIO::DT_xxx" constants:
555 705
556 "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",
557 "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",
558 "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".
559 709
560 "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
561 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
562 reasons, the $type scalars are read-only: you can not modify 712 speed/memory reasons, the $type scalars are read-only: you must
563 them. 713 not modify them.
564 714
565 $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
566 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
567 unspecified content on systems that do not deliver the inode 717 unspecified content on systems that do not deliver the inode
568 information. 718 information.
569 719
570 IO::AIO::READDIR_DIRS_FIRST 720 IO::AIO::READDIR_DIRS_FIRST
571 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
572 order where likely directories come first. This is useful when 722 order where likely directories come first, in optimal stat
573 you need to quickly find directories, or you want to find all 723 order. This is useful when you need to quickly find directories,
574 directories while avoiding to stat() each entry. 724 or you want to find all directories while avoiding to stat()
725 each entry.
575 726
576 If the system returns type information in readdir, then this is 727 If the system returns type information in readdir, then this is
577 used to find directories directly. Otherwise, likely directories 728 used to find directories directly. Otherwise, likely directories
578 are files beginning with ".", or otherwise files with no dots, 729 are names beginning with ".", or otherwise names with no dots,
579 of which files with short names are tried first. 730 of which names with short names are tried first.
580 731
581 IO::AIO::READDIR_STAT_ORDER 732 IO::AIO::READDIR_STAT_ORDER
582 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
583 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
584 to stat() all files in the given directory, then the returned 735 to stat() most or all files in the given directory, then the
585 order will likely be fastest. 736 returned order will likely be faster.
586 737
587 If both this flag and "IO::AIO::READDIR_DIRS_FIRST" are 738 If both this flag and "IO::AIO::READDIR_DIRS_FIRST" are
588 specified, then the likely dirs come first, resulting in a less 739 specified, then the likely dirs come first, resulting in a less
589 optimal stat order. 740 optimal stat order for stat'ing all entries, but likely a more
741 optimal order for finding subdirectories.
590 742
591 IO::AIO::READDIR_FOUND_UNKNOWN 743 IO::AIO::READDIR_FOUND_UNKNOWN
592 This flag should not be set when calling "aio_readdirx". 744 This flag should not be set when calling "aio_readdirx".
593 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
594 $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
595 flag therefore indicates that all $type's are known, which can 747 flag therefore indicates that all $type's are known, which can
596 be used to speed up some algorithms. 748 be used to speed up some algorithms.
597 749
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
598 aio_load $path, $data, $callback->($status) 777 aio_load $pathname, $data, $callback->($status)
599 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
600 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.
601 783
602 aio_copy $srcpath, $dstpath, $callback->($status) 784 aio_copy $srcpath, $dstpath, $callback->($status)
603 Try to copy the *file* (directories not supported as either source 785 Try to copy the *file* (directories not supported as either source
604 or destination) from $srcpath to $dstpath and call the callback with 786 or destination) from $srcpath to $dstpath and call the callback with
605 a status of 0 (ok) or -1 (error, see $!). 787 a status of 0 (ok) or -1 (error, see $!).
606 788
789 Existing destination files will be truncated.
790
607 This is a composite request that creates the destination file with 791 This is a composite request that creates the destination file with
608 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
609 "aio_sendfile", followed by restoring atime, mtime, access mode and 793 "aio_sendfile", followed by restoring atime, mtime, access mode and
610 uid/gid, in that order. 794 uid/gid, in that order.
611 795
… …
620 804
621 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;
622 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"
623 and, if that is successful, unlinks the $srcpath. 807 and, if that is successful, unlinks the $srcpath.
624 808
625 aio_scandir $path, $maxreq, $callback->($dirs, $nondirs) 809 aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
626 Scans a directory (similar to "aio_readdir") but additionally tries 810 Scans a directory (similar to "aio_readdir") but additionally tries
627 to efficiently separate the entries of directory $path into two sets 811 to efficiently separate the entries of directory $path into two sets
628 of names, directories you can recurse into (directories), and ones 812 of names, directories you can recurse into (directories), and ones
629 you cannot recurse into (everything else, including symlinks to 813 you cannot recurse into (everything else, including symlinks to
630 directories). 814 directories).
631 815
632 "aio_scandir" is a composite request that creates of many sub 816 "aio_scandir" is a composite request that generates many sub
633 requests_ $maxreq specifies the maximum number of outstanding aio 817 requests. $maxreq specifies the maximum number of outstanding aio
634 requests that this function generates. If it is "<= 0", then a 818 requests that this function generates. If it is "<= 0", then a
635 suitable default will be chosen (currently 4). 819 suitable default will be chosen (currently 4).
636 820
637 On error, the callback is called without arguments, otherwise it 821 On error, the callback is called without arguments, otherwise it
638 receives two array-refs with path-relative entry names. 822 receives two array-refs with path-relative entry names.
… …
663 Then entries will be sorted into likely directories a non-initial 847 Then entries will be sorted into likely directories a non-initial
664 dot currently) and likely non-directories (see "aio_readdirx"). Then 848 dot currently) and likely non-directories (see "aio_readdirx"). Then
665 every entry plus an appended "/." will be "stat"'ed, likely 849 every entry plus an appended "/." will be "stat"'ed, likely
666 directories first, in order of their inode numbers. If that 850 directories first, in order of their inode numbers. If that
667 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
668 directory (which will be checked seperately). This is often faster 852 directory (which will be checked separately). This is often faster
669 than stat'ing the entry itself because filesystems might detect the 853 than stat'ing the entry itself because filesystems might detect the
670 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
671 filetype feature), even on systems that cannot return the filetype 855 filetype feature), even on systems that cannot return the filetype
672 information on readdir. 856 information on readdir.
673 857
… …
679 863
680 It will also likely work on non-POSIX filesystems with reduced 864 It will also likely work on non-POSIX filesystems with reduced
681 efficiency as those tend to return 0 or 1 as link counts, which 865 efficiency as those tend to return 0 or 1 as link counts, which
682 disables the directory counting heuristic. 866 disables the directory counting heuristic.
683 867
684 aio_rmtree $path, $callback->($status) 868 aio_rmtree $pathname, $callback->($status)
685 Delete a directory tree starting (and including) $path, return the 869 Delete a directory tree starting (and including) $path, return the
686 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
687 uses "aio_scandir" to recurse into and rmdir directories, and unlink 871 uses "aio_scandir" to recurse into and rmdir directories, and unlink
688 everything else. 872 everything else.
689 873
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
690 aio_sync $callback->($status) 922 aio_sync $callback->($status)
691 Asynchronously call sync and call the callback when finished. 923 Asynchronously call sync and call the callback when finished.
692 924
693 aio_fsync $fh, $callback->($status) 925 aio_fsync $fh, $callback->($status)
694 Asynchronously call fsync on the given filehandle and call the 926 Asynchronously call fsync on the given filehandle and call the
… …
698 Asynchronously call fdatasync on the given filehandle and call the 930 Asynchronously call fdatasync on the given filehandle and call the
699 callback with the fdatasync result code. 931 callback with the fdatasync result code.
700 932
701 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
702 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.
703 941
704 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status) 942 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
705 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
706 to disk (but NOT the metadata), by calling the Linux-specific 944 to disk (but NOT the metadata), by calling the Linux-specific
707 sync_file_range call. If sync_file_range is not available or it 945 sync_file_range call. If sync_file_range is not available or it
… …
711 "IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE", 949 "IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE",
712 "IO::AIO::SYNC_FILE_RANGE_WRITE" and 950 "IO::AIO::SYNC_FILE_RANGE_WRITE" and
713 "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
714 manpage for details. 952 manpage for details.
715 953
716 aio_pathsync $path, $callback->($status) 954 aio_pathsync $pathname, $callback->($status)
717 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
718 a composite request intended to sync directories after directory 956 a composite request intended to sync directories after directory
719 operations (E.g. rename). This might not work on all operating 957 operations (E.g. rename). This might not work on all operating
720 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
721 directory changes get written to disc. It works for anything that 959 directory changes get written to disc. It works for anything that
… …
724 Future versions of this function might fall back to other methods 962 Future versions of this function might fall back to other methods
725 when "fsync" on the directory fails (such as calling "sync"). 963 when "fsync" on the directory fails (such as calling "sync").
726 964
727 Passes 0 when everything went ok, and -1 on error. 965 Passes 0 when everything went ok, and -1 on error.
728 966
729 aio_msync $scalar, $offset = 0, $length = undef, flags = 0, 967 aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC,
730 $callback->($status) 968 $callback->($status)
731 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
732 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
733 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,
734 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
… …
736 974
737 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
738 memory area starting at $offset in the string and ending $length 976 memory area starting at $offset in the string and ending $length
739 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
740 $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
741 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
742 "IO::AIO::MS_INVALIDATE" and "IO::AIO::MS_SYNC". 980 an optional "IO::AIO::MS_INVALIDATE".
743 981
744 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, 982 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0,
745 $callback->($status) 983 $callback->($status)
746 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
747 mmap(2)ed scalars. 985 mmap(2)ed scalars.
748 986
749 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
750 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
751 "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
752 reads all pages and ensures they are instantiated) or 990 reads all pages and ensures they are instantiated) or
753 "IO::AIO::MT_MODIFY", which modifies the memory page s(by reading 991 "IO::AIO::MT_MODIFY", which modifies the memory pages (by reading
754 and writing an octet from it, which dirties the page). 992 and writing an octet from it, which dirties the page).
993
994 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
995 This is a rather advanced IO::AIO call, which works best on
996 mmap(2)ed scalars.
997
998 It reads in all the pages of the underlying storage into memory (if
999 any) and locks them, so they are not getting swapped/paged out or
1000 removed.
1001
1002 If $length is undefined, then the scalar will be locked till the
1003 end.
1004
1005 On systems that do not implement "mlock", this function returns -1
1006 and sets errno to "ENOSYS".
1007
1008 Note that the corresponding "munlock" is synchronous and is
1009 documented under "MISCELLANEOUS FUNCTIONS".
1010
1011 Example: open a file, mmap and mlock it - both will be undone when
1012 $data gets destroyed.
1013
1014 open my $fh, "<", $path or die "$path: $!";
1015 my $data;
1016 IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
1017 aio_mlock $data; # mlock in background
1018
1019 aio_mlockall $flags, $callback->($status)
1020 Calls the "mlockall" function with the given $flags (a combination
1021 of "IO::AIO::MCL_CURRENT", "IO::AIO::MCL_FUTURE" and
1022 "IO::AIO::MCL_ONFAULT").
1023
1024 On systems that do not implement "mlockall", this function returns
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".
1028
1029 Note that the corresponding "munlockall" is synchronous and is
1030 documented under "MISCELLANEOUS FUNCTIONS".
1031
1032 Example: asynchronously lock all current and future pages into
1033 memory.
1034
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".
755 1084
756 aio_group $callback->(...) 1085 aio_group $callback->(...)
757 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
758 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
759 to bundle many requests into a single, composite, request with a 1088 to bundle many requests into a single, composite, request with a
… …
793 While it is theoretically handy to have simple I/O scheduling 1122 While it is theoretically handy to have simple I/O scheduling
794 requests like sleep and file handle readable/writable, the overhead 1123 requests like sleep and file handle readable/writable, the overhead
795 this creates is immense (it blocks a thread for a long time) so do 1124 this creates is immense (it blocks a thread for a long time) so do
796 not use this function except to put your application under 1125 not use this function except to put your application under
797 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.
798 1245
799 IO::AIO::REQ CLASS 1246 IO::AIO::REQ CLASS
800 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
801 called in non-void context. 1248 called in non-void context.
802 1249
… …
902 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
903 attached generator that generates requests if idle. The idea behind 1350 attached generator that generates requests if idle. The idea behind
904 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
905 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
906 long time. For example, "aio_scandir" might generate hundreds of 1353 long time. For example, "aio_scandir" might generate hundreds of
907 thousands "aio_stat" requests, delaying any later requests for a 1354 thousands of "aio_stat" requests, delaying any later requests for a
908 long time. 1355 long time.
909 1356
910 To avoid this, and allow incremental generation of requests, you can 1357 To avoid this, and allow incremental generation of requests, you can
911 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
912 requests. The feed callback will be called whenever there are few 1359 requests. The feed callback will be called whenever there are few
… …
954 results. 1401 results.
955 1402
956 See "poll_cb" for an example. 1403 See "poll_cb" for an example.
957 1404
958 IO::AIO::poll_cb 1405 IO::AIO::poll_cb
959 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
960 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
961 it returned earlier for whatever reason. Returns immediately when no 1408 to call this "regularly" to finish outstanding requests.
962 events are outstanding. The amount of events processed depends on
963 the settings of "IO::AIO::max_poll_req" and
964 "IO::AIO::max_poll_time".
965 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
966 If not all requests were processed for whatever reason, the 1416 If not all requests were processed for whatever reason, the poll
967 filehandle will still be ready when "poll_cb" returns, so normally 1417 file descriptor will still be ready when "poll_cb" returns, so
968 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.
969 1427
970 Example: Install an Event watcher that automatically calls 1428 Example: Install an Event watcher that automatically calls
971 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
972 the SYNOPSIS section, at the top of this document): 1430 the SYNOPSIS section, at the top of this document):
973 1431
974 Event->io (fd => IO::AIO::poll_fileno, 1432 Event->io (fd => IO::AIO::poll_fileno,
975 poll => 'r', async => 1, 1433 poll => 'r', async => 1,
976 cb => \&IO::AIO::poll_cb); 1434 cb => \&IO::AIO::poll_cb);
977 1435
978 IO::AIO::poll_wait 1436 IO::AIO::poll_wait
979 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
980 phase, wait till the result filehandle becomes ready for reading 1438 requests are outstanding anymore.
981 (simply does a "select" on the filehandle. This is useful if you 1439
982 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.
983 1442
984 See "nreqs" for an example. 1443 See "nreqs" for an example.
985 1444
986 IO::AIO::poll 1445 IO::AIO::poll
987 Waits until some requests have been handled. 1446 Waits until some requests have been handled.
… …
996 1455
997 Strictly equivalent to: 1456 Strictly equivalent to:
998 1457
999 IO::AIO::poll_wait, IO::AIO::poll_cb 1458 IO::AIO::poll_wait, IO::AIO::poll_cb
1000 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
1001 1471
1002 IO::AIO::max_poll_reqs $nreqs 1472 IO::AIO::max_poll_reqs $nreqs
1003 IO::AIO::max_poll_time $seconds 1473 IO::AIO::max_poll_time $seconds
1004 These set the maximum number of requests (default 0, meaning 1474 These set the maximum number of requests (default 0, meaning
1005 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
… …
1067 1537
1068 Under normal circumstances you don't need to call this function. 1538 Under normal circumstances you don't need to call this function.
1069 1539
1070 IO::AIO::max_idle $nthreads 1540 IO::AIO::max_idle $nthreads
1071 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
1072 (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
1073 seconds). That means if a thread becomes idle while $nthreads other 1543 timeout (default: 10 seconds). That means if a thread becomes idle
1074 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.
1075 1546
1076 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
1077 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
1078 resources under normal circumstances (1000 threads can easily 1549 resources under normal circumstances (1000 threads can easily
1079 consume 30MB of RAM). 1550 consume 30MB of RAM).
1080 1551
1081 The default is probably ok in most situations, especially if thread 1552 The default is probably ok in most situations, especially if thread
1082 creation is fast. If thread creation is very slow on your system you 1553 creation is fast. If thread creation is very slow on your system you
1083 might want to use larger values. 1554 might want to use larger values.
1084 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
1085 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
1086 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
1087 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
1088 inexact: Better use an "aio_group" together with a feed callback. 1572 inexact: Better use an "aio_group" together with a feed callback.
1089 1573
1090 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
1091 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:
1092 "poll_cb" (and "poll_some" and other functions calling "poll_cb")
1093 function will block until the limit is no longer exceeded.
1094 1576
1095 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
1096 the number of outstanding requests. 1593 no practical limit on the number of outstanding requests.
1097
1098 You can still queue as many requests as you want. Therefore,
1099 "max_outstanding" is mainly useful in simple scripts (with low
1100 values) or as a stop gap to shield against fatal memory overflow
1101 (with large values).
1102 1594
1103 STATISTICAL INFORMATION 1595 STATISTICAL INFORMATION
1104 IO::AIO::nreqs 1596 IO::AIO::nreqs
1105 Returns the number of requests currently in the ready, execute or 1597 Returns the number of requests currently in the ready, execute or
1106 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
… …
1117 1609
1118 IO::AIO::npending 1610 IO::AIO::npending
1119 Returns the number of requests currently in the pending state 1611 Returns the number of requests currently in the pending state
1120 (executed, but not yet processed by poll_cb). 1612 (executed, but not yet processed by poll_cb).
1121 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
1122 MISCELLANEOUS FUNCTIONS 1699 MISCELLANEOUS FUNCTIONS
1123 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
1124 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.
1125 1728
1126 IO::AIO::sendfile $ofh, $ifh, $offset, $count 1729 IO::AIO::sendfile $ofh, $ifh, $offset, $count
1127 Calls the "eio_sendfile_sync" function, which is like 1730 Calls the "eio_sendfile_sync" function, which is like
1128 "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
1129 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
1130 set to non-blocking operations). 1733 set to non-blocking operations).
1131 1734
1132 Returns the number of bytes copied, or -1 on error. 1735 Returns the number of bytes copied, or -1 on error.
1133 1736
1134 IO::AIO::fadvise $fh, $offset, $len, $advice 1737 IO::AIO::fadvise $fh, $offset, $len, $advice
1135 Simply calls the "posix_fadvise" function (see it's manpage for 1738 Simply calls the "posix_fadvise" function (see its manpage for
1136 details). The following advice constants are avaiable: 1739 details). The following advice constants are available:
1137 "IO::AIO::FADV_NORMAL", "IO::AIO::FADV_SEQUENTIAL", 1740 "IO::AIO::FADV_NORMAL", "IO::AIO::FADV_SEQUENTIAL",
1138 "IO::AIO::FADV_RANDOM", "IO::AIO::FADV_NOREUSE", 1741 "IO::AIO::FADV_RANDOM", "IO::AIO::FADV_NOREUSE",
1139 "IO::AIO::FADV_WILLNEED", "IO::AIO::FADV_DONTNEED". 1742 "IO::AIO::FADV_WILLNEED", "IO::AIO::FADV_DONTNEED".
1140 1743
1141 On systems that do not implement "posix_fadvise", this function 1744 On systems that do not implement "posix_fadvise", this function
1142 returns ENOSYS, otherwise the return value of "posix_fadvise". 1745 returns ENOSYS, otherwise the return value of "posix_fadvise".
1143 1746
1747 IO::AIO::madvise $scalar, $offset, $len, $advice
1748 Simply calls the "posix_madvise" function (see its manpage for
1749 details). The following advice constants are available:
1750 "IO::AIO::MADV_NORMAL", "IO::AIO::MADV_SEQUENTIAL",
1751 "IO::AIO::MADV_RANDOM", "IO::AIO::MADV_WILLNEED",
1752 "IO::AIO::MADV_DONTNEED".
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
1758 On systems that do not implement "posix_madvise", this function
1759 returns ENOSYS, otherwise the return value of "posix_madvise".
1760
1761 IO::AIO::mprotect $scalar, $offset, $len, $protect
1762 Simply calls the "mprotect" function on the preferably AIO::mmap'ed
1763 $scalar (see its manpage for details). The following protect
1764 constants are available: "IO::AIO::PROT_NONE", "IO::AIO::PROT_READ",
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.
1770
1771 On systems that do not implement "mprotect", this function returns
1772 ENOSYS, otherwise the return value of "mprotect".
1773
1144 IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset] 1774 IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
1145 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
1146 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.
1147 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
1148 The only operations allowed on the scalar are "substr"/"vec" that 1783 The only operations allowed on the mmapped scalar are
1149 don't change the string length, and most read-only operations such 1784 "substr"/"vec", which don't change the string length, and most
1150 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.
1151 1787
1152 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.
1153 1789
1154 The memory map associated with the $scalar is automatically removed 1790 The memory map associated with the $scalar is automatically removed
1155 when the $scalar is destroyed, or when the "IO::AIO::mmap" or 1791 when the $scalar is undef'd or destroyed, or when the
1156 "IO::AIO::munmap" functions are called. 1792 "IO::AIO::mmap" or "IO::AIO::munmap" functions are called on it.
1157 1793
1158 This calls the "mmap"(2) function internally. See your system's 1794 This calls the "mmap"(2) function internally. See your system's
1159 manual page for details on the $length, $prot and $flags parameters. 1795 manual page for details on the $length, $prot and $flags parameters.
1160 1796
1161 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
… …
1165 "IO::AIO::PROT_EXEC", "IO::AIO::PROT_READ" and/or 1801 "IO::AIO::PROT_EXEC", "IO::AIO::PROT_READ" and/or
1166 "IO::AIO::PROT_WRITE", 1802 "IO::AIO::PROT_WRITE",
1167 1803
1168 $flags can be a combination of "IO::AIO::MAP_SHARED" or 1804 $flags can be a combination of "IO::AIO::MAP_SHARED" or
1169 "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
1170 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
1171 (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",
1172 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",
1173 "IO::AIO::MAP_NORESERVE", "IO::AIO::MAP_POPULATE" or 1811 "IO::AIO::MAP_32BIT", "IO::AIO::MAP_HUGETLB" or
1174 "IO::AIO::MAP_NONBLOCK" 1812 "IO::AIO::MAP_STACK".
1175 1813
1176 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.
1177 1815
1178 $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
1179 be a multiple of "IO::AIO::PAGESIZE" and defaults to 0. 1817 be a multiple of "IO::AIO::PAGESIZE" and defaults to 0.
… …
1192 my $fast_md5 = md5 $data; 1830 my $fast_md5 = md5 $data;
1193 1831
1194 IO::AIO::munmap $scalar 1832 IO::AIO::munmap $scalar
1195 Removes a previous mmap and undefines the $scalar. 1833 Removes a previous mmap and undefines the $scalar.
1196 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
1197 IO::AIO::mlockall $flags 1859 IO::AIO::mlockall $flags
1198 Calls the "mlockall" function with the given $flags (a combination 1860 Calls the "eio_mlockall_sync" function, which is like
1199 of "IO::AIO::MCL_CURRENT" and "IO::AIO::MCL__FUTURE"). 1861 "aio_mlockall", but is blocking.
1200 1862
1201 On systems that do not implement "mlockall", this function returns 1863 IO::AIO::munlock $scalar, $offset = 0, $length = undef
1202 ENOSYS, otherwise the return value of "mlockall". 1864 Calls the "munlock" function, undoing the effects of a previous
1865 "aio_mlock" call (see its description for details).
1203 1866
1204 IO::AIO::munlockall 1867 IO::AIO::munlockall
1205 Calls the "munlockall" function. 1868 Calls the "munlockall" function.
1206 1869
1207 On systems that do not implement "munlockall", this function returns 1870 On systems that do not implement "munlockall", this function returns
1208 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.
1209 2000
1210EVENT LOOP INTEGRATION 2001EVENT LOOP INTEGRATION
1211 It is recommended to use AnyEvent::AIO to integrate IO::AIO 2002 It is recommended to use AnyEvent::AIO to integrate IO::AIO
1212 automatically into many event loops: 2003 automatically into many event loops:
1213 2004
… …
1236 # Danga::Socket integration 2027 # Danga::Socket integration
1237 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno => 2028 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
1238 \&IO::AIO::poll_cb); 2029 \&IO::AIO::poll_cb);
1239 2030
1240 FORK BEHAVIOUR 2031 FORK BEHAVIOUR
1241 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.
1242 2039
1243 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
1244 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
1245 fork the parent simply leaves the quiescent state and continues 2042 supported, but using IO::AIO in the child is not.
1246 request/result processing, while the child frees the request/result
1247 queue (so that the requests started before the fork will only be handled
1248 in the parent). Threads will be started on demand until the limit set in
1249 the parent process has been reached again.
1250 2043
1251 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.
1252 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:
1253 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".
1254 2066
1255 MEMORY USAGE 2067 MEMORY USAGE
1256 Per-request usage: 2068 Per-request usage:
1257 2069
1258 Each aio request uses - depending on your architecture - around 100-200 2070 Each aio request uses - depending on your architecture - around 100-200
… …
1269 In the execution phase, some aio requests require more memory for 2081 In the execution phase, some aio requests require more memory for
1270 temporary buffers, and each thread requires a stack and other data 2082 temporary buffers, and each thread requires a stack and other data
1271 structures (usually around 16k-128k, depending on the OS). 2083 structures (usually around 16k-128k, depending on the OS).
1272 2084
1273KNOWN BUGS 2085KNOWN BUGS
1274 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.
1275 2097
1276SEE ALSO 2098SEE ALSO
1277 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
1278 more natural syntax. 2100 more natural syntax.
1279 2101

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