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Revision 1.61 by root, Sun Aug 12 06:07:06 2018 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
… …
24 $req->cancel; # cancel request if still in queue 24 $req->cancel; # cancel request if still in queue
25 25
26 my $grp = aio_group sub { print "all stats done\n" }; 26 my $grp = aio_group sub { print "all stats done\n" };
27 add $grp aio_stat "..." for ...; 27 add $grp aio_stat "..." for ...;
28 28
29 # AnyEvent integration
30 open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
31 my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
32
33 # Event integration
34 Event->io (fd => IO::AIO::poll_fileno,
35 poll => 'r',
36 cb => \&IO::AIO::poll_cb);
37
38 # Glib/Gtk2 integration
39 add_watch Glib::IO IO::AIO::poll_fileno,
40 in => sub { IO::AIO::poll_cb; 1 };
41
42 # Tk integration
43 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
44 readable => \&IO::AIO::poll_cb);
45
46 # Danga::Socket integration
47 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
48 \&IO::AIO::poll_cb);
49
50DESCRIPTION 29DESCRIPTION
51 This module implements asynchronous I/O using whatever means your 30 This module implements asynchronous I/O using whatever means your
52 operating system supports. 31 operating system supports. It is implemented as an interface to "libeio"
32 (<http://software.schmorp.de/pkg/libeio.html>).
53 33
54 Asynchronous means that operations that can normally block your program 34 Asynchronous means that operations that can normally block your program
55 (e.g. reading from disk) will be done asynchronously: the operation will 35 (e.g. reading from disk) will be done asynchronously: the operation will
56 still block, but you can do something else in the meantime. This is 36 still block, but you can do something else in the meantime. This is
57 extremely useful for programs that need to stay interactive even when 37 extremely useful for programs that need to stay interactive even when
… …
62 operations concurrently. 42 operations concurrently.
63 43
64 While most of this works on all types of file descriptors (for example 44 While most of this works on all types of file descriptors (for example
65 sockets), using these functions on file descriptors that support 45 sockets), using these functions on file descriptors that support
66 nonblocking operation (again, sockets, pipes etc.) is very inefficient. 46 nonblocking operation (again, sockets, pipes etc.) is very inefficient.
67 Use an event loop for that (such as the Event module): IO::AIO will 47 Use an event loop for that (such as the EV module): IO::AIO will
68 naturally fit into such an event loop itself. 48 naturally fit into such an event loop itself.
69 49
70 In this version, a number of threads are started that execute your 50 In this version, a number of threads are started that execute your
71 requests and signal their completion. You don't need thread support in 51 requests and signal their completion. You don't need thread support in
72 perl, and the threads created by this module will not be visible to 52 perl, and the threads created by this module will not be visible to
… …
75 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
76 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
77 aio_write, so the remaining functionality would have to be implemented 57 aio_write, so the remaining functionality would have to be implemented
78 using threads anyway. 58 using threads anyway.
79 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
80 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,
81 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
82 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
83 call "poll_cb" (or other "aio_" functions) recursively. 67 call "poll_cb" (or other "aio_" functions) recursively.
84 68
85 EXAMPLE 69 EXAMPLE
86 This is a simple example that uses the Event module and loads 70 This is a simple example that uses the EV module and loads /etc/passwd
87 /etc/passwd asynchronously: 71 asynchronously:
88 72
89 use Fcntl;
90 use Event; 73 use EV;
91 use IO::AIO; 74 use IO::AIO;
92 75
93 # register the IO::AIO callback with Event 76 # register the IO::AIO callback with EV
94 Event->io (fd => IO::AIO::poll_fileno, 77 my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
95 poll => 'r',
96 cb => \&IO::AIO::poll_cb);
97 78
98 # queue the request to open /etc/passwd 79 # queue the request to open /etc/passwd
99 aio_open "/etc/passwd", O_RDONLY, 0, sub { 80 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
100 my $fh = shift 81 my $fh = shift
101 or die "error while opening: $!"; 82 or die "error while opening: $!";
102 83
103 # stat'ing filehandles is generally non-blocking 84 # stat'ing filehandles is generally non-blocking
104 my $size = -s $fh; 85 my $size = -s $fh;
… …
113 94
114 # file contents now in $contents 95 # file contents now in $contents
115 print $contents; 96 print $contents;
116 97
117 # exit event loop and program 98 # exit event loop and program
118 Event::unloop; 99 EV::break;
119 }; 100 };
120 }; 101 };
121 102
122 # possibly queue up other requests, or open GUI windows, 103 # possibly queue up other requests, or open GUI windows,
123 # check for sockets etc. etc. 104 # check for sockets etc. etc.
124 105
125 # process events as long as there are some: 106 # process events as long as there are some:
126 Event::loop; 107 EV::run;
127 108
128REQUEST ANATOMY AND LIFETIME 109REQUEST ANATOMY AND LIFETIME
129 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
130 not directly visible to Perl. 111 not directly visible to Perl.
131 112
… …
167 anymore (except possibly for the Perl object, but its connection to 148 anymore (except possibly for the Perl object, but its connection to
168 the actual aio request is severed and calling its methods will 149 the actual aio request is severed and calling its methods will
169 either do nothing or result in a runtime error). 150 either do nothing or result in a runtime error).
170 151
171FUNCTIONS 152FUNCTIONS
172 AIO REQUEST FUNCTIONS 153 QUICK OVERVIEW
154 This section simply lists the prototypes most of the functions for quick
155 reference. See the following sections for function-by-function
156 documentation.
157
158 aio_wd $pathname, $callback->($wd)
159 aio_open $pathname, $flags, $mode, $callback->($fh)
160 aio_close $fh, $callback->($status)
161 aio_seek $fh,$offset,$whence, $callback->($offs)
162 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
163 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
164 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
165 aio_readahead $fh,$offset,$length, $callback->($retval)
166 aio_stat $fh_or_path, $callback->($status)
167 aio_lstat $fh, $callback->($status)
168 aio_statvfs $fh_or_path, $callback->($statvfs)
169 aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
170 aio_chown $fh_or_path, $uid, $gid, $callback->($status)
171 aio_chmod $fh_or_path, $mode, $callback->($status)
172 aio_truncate $fh_or_path, $offset, $callback->($status)
173 aio_allocate $fh, $mode, $offset, $len, $callback->($status)
174 aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
175 aio_unlink $pathname, $callback->($status)
176 aio_mknod $pathname, $mode, $dev, $callback->($status)
177 aio_link $srcpath, $dstpath, $callback->($status)
178 aio_symlink $srcpath, $dstpath, $callback->($status)
179 aio_readlink $pathname, $callback->($link)
180 aio_realpath $pathname, $callback->($path)
181 aio_rename $srcpath, $dstpath, $callback->($status)
182 aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
183 aio_mkdir $pathname, $mode, $callback->($status)
184 aio_rmdir $pathname, $callback->($status)
185 aio_readdir $pathname, $callback->($entries)
186 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
187 IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
188 IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
189 aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
190 aio_load $pathname, $data, $callback->($status)
191 aio_copy $srcpath, $dstpath, $callback->($status)
192 aio_move $srcpath, $dstpath, $callback->($status)
193 aio_rmtree $pathname, $callback->($status)
194 aio_fcntl $fh, $cmd, $arg, $callback->($status)
195 aio_ioctl $fh, $request, $buf, $callback->($status)
196 aio_sync $callback->($status)
197 aio_syncfs $fh, $callback->($status)
198 aio_fsync $fh, $callback->($status)
199 aio_fdatasync $fh, $callback->($status)
200 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
201 aio_pathsync $pathname, $callback->($status)
202 aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($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)
206 aio_group $callback->(...)
207 aio_nop $callback->()
208
209 $prev_pri = aioreq_pri [$pri]
210 aioreq_nice $pri_adjust
211
212 IO::AIO::poll_wait
213 IO::AIO::poll_cb
214 IO::AIO::poll
215 IO::AIO::flush
216 IO::AIO::max_poll_reqs $nreqs
217 IO::AIO::max_poll_time $seconds
218 IO::AIO::min_parallel $nthreads
219 IO::AIO::max_parallel $nthreads
220 IO::AIO::max_idle $nthreads
221 IO::AIO::idle_timeout $seconds
222 IO::AIO::max_outstanding $maxreqs
223 IO::AIO::nreqs
224 IO::AIO::nready
225 IO::AIO::npending
226 $nfd = IO::AIO::get_fdlimit [EXPERIMENTAL]
227 IO::AIO::min_fdlimit $nfd [EXPERIMENTAL]
228
229 IO::AIO::sendfile $ofh, $ifh, $offset, $count
230 IO::AIO::fadvise $fh, $offset, $len, $advice
231 IO::AIO::mmap $scalar, $length, $prot, $flags[, $fh[, $offset]]
232 IO::AIO::munmap $scalar
233 IO::AIO::mremap $scalar, $new_length, $flags[, $new_address]
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
237 IO::AIO::munlockall
238
239 API NOTES
173 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
174 with the same name (sans "aio_"). The arguments are similar or 241 with the same name (sans "aio_"). The arguments are similar or
175 identical, and they all accept an additional (and optional) $callback 242 identical, and they all accept an additional (and optional) $callback
176 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
177 called with the syscall return code (e.g. most syscalls return -1 on 244 called after the syscall has been executed in an asynchronous fashion.
178 error, unlike perl, which usually delivers "false") as it's sole 245 The results of the request will be passed as arguments to the callback
179 argument when the given syscall has been executed asynchronously. 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".
180 252
181 All functions expecting a filehandle keep a copy of the filehandle 253 All functions expecting a filehandle keep a copy of the filehandle
182 internally until the request has finished. 254 internally until the request has finished.
183 255
184 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
185 further manipulation of those requests while they are in-flight. 257 further manipulation of those requests while they are in-flight.
186 258
187 The pathnames you pass to these routines *must* be absolute and encoded 259 The pathnames you pass to these routines *should* be absolute. The
188 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
189 being executed, the current working directory could have changed. 261 current working directory could have changed. Alternatively, you can
190 Alternatively, you can make sure that you never change the current 262 make sure that you never change the current working directory anywhere
191 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.
192 267
193 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
194 pass in filenames you got from outside (command line, readdir etc.) 269 pass in filenames you got from outside (command line, readdir etc.)
195 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
196 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)
197 the user environment, d) use Glib::filename_from_unicode on unicode 272 encoding in effect in the user environment, d) use
198 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
199 contents. 274 else to ensure your scalar has the correct contents.
200 275
201 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
202 handles correctly wether it is set or not. 277 handles correctly whether it is set or not.
203 278
279 AIO REQUEST FUNCTIONS
204 $prev_pri = aioreq_pri [$pri] 280 $prev_pri = aioreq_pri [$pri]
205 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
206 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.
207 283
208 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
… …
230 Similar to "aioreq_pri", but subtracts the given value from the 306 Similar to "aioreq_pri", but subtracts the given value from the
231 current priority, so the effect is cumulative. 307 current priority, so the effect is cumulative.
232 308
233 aio_open $pathname, $flags, $mode, $callback->($fh) 309 aio_open $pathname, $flags, $mode, $callback->($fh)
234 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
235 newly created filehandle for the file. 311 newly created filehandle for the file (or "undef" in case of an
312 error).
236 313
237 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,
238 above, for an explanation. 315 above, for an explanation.
239 316
240 The $flags argument is a bitmask. See the "Fcntl" module for a list. 317 The $flags argument is a bitmask. See the "Fcntl" module for a list.
… …
247 will be modified by the umask in effect then the request is being 324 will be modified by the umask in effect then the request is being
248 executed, so better never change the umask. 325 executed, so better never change the umask.
249 326
250 Example: 327 Example:
251 328
252 aio_open "/etc/passwd", O_RDONLY, 0, sub { 329 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
253 if ($_[0]) { 330 if ($_[0]) {
254 print "open successful, fh is $_[0]\n"; 331 print "open successful, fh is $_[0]\n";
255 ... 332 ...
256 } else { 333 } else {
257 die "open failed: $!\n"; 334 die "open failed: $!\n";
258 } 335 }
259 }; 336 };
260 337
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
261 aio_close $fh, $callback->($status) 348 aio_close $fh, $callback->($status)
262 Asynchronously close a file and call the callback with the result 349 Asynchronously close a file and call the callback with the result
263 code. 350 code.
264 351
265 Unlike the other functions operating on files, this function uses 352 Unfortunately, you can't do this to perl. Perl *insists* very
266 the PerlIO layer to close the filehandle. The reason is that the 353 strongly on closing the file descriptor associated with the
267 PerlIO API insists on closing the underlying fd itself, no matter 354 filehandle itself.
268 what, and doesn't allow modifications to the fd. Unfortunately, it
269 is not clear that you can call PerlIO from different threads
270 (actually, its quite clear that this won't work in some cases), so
271 while it likely works perfectly with simple file handles (such as
272 the ones created by "aio_open") it might fail in interesting ways
273 for others.
274 355
275 Having said that, aio_close tries to clean up the filehandle as much 356 Therefore, "aio_close" will not close the filehandle - instead it
276 as possible before handing it to an io thread, and generally does 357 will use dup2 to overwrite the file descriptor with the write-end of
277 work. 358 a pipe (the pipe fd will be created on demand and will be cached).
359
360 Or in other words: the file descriptor will be closed, but it will
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".
278 381
279 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval) 382 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
280 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval) 383 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
281 Reads or writes $length bytes from the specified $fh and $offset 384 Reads or writes $length bytes from or to the specified $fh and
282 into the scalar given by $data and offset $dataoffset and calls the 385 $offset into the scalar given by $data and offset $dataoffset and
283 callback without the actual number of bytes read (or -1 on error, 386 calls the callback with the actual number of bytes transferred (or
284 just like the syscall). 387 -1 on error, just like the syscall).
388
389 "aio_read" will, like "sysread", shrink or grow the $data scalar to
390 offset plus the actual number of bytes read.
285 391
286 If $offset is undefined, then the current file descriptor offset 392 If $offset is undefined, then the current file descriptor offset
287 will be used (and updated), otherwise the file descriptor offset 393 will be used (and updated), otherwise the file descriptor offset
288 will not be changed by these calls. 394 will not be changed by these calls.
289 395
… …
308 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval) 414 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
309 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
310 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
311 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
312 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
313 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.
314 421
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
315 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
316 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
317 to a socket, and $in_fh should refer to mmap'able file. 441 to a socket, and $in_fh should refer to an mmap'able file.
318 442
319 If the native sendfile call fails or is not implemented, it will be 443 If a native sendfile cannot be found or it fails with "ENOSYS",
320 emulated, so you can call "aio_sendfile" on any type of filehandle 444 "EINVAL", "ENOTSUP", "EOPNOTSUPP", "EAFNOSUPPORT", "EPROTOTYPE" or
321 regardless of the limitations of the operating system. 445 "ENOTSOCK", it will be emulated, so you can call "aio_sendfile" on
446 any type of filehandle regardless of the limitations of the
447 operating system.
322 448
323 Please note, however, that "aio_sendfile" can read more bytes from 449 As native sendfile syscalls (as practically any non-POSIX interface
324 $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
325 bytes have been read from "aio_sendfile" alone, as "aio_sendfile" 451 rather buggy on many systems, this implementation tries to work
326 only provides the number of bytes written to $out_fh. Only if the 452 around some known bugs in Linux and FreeBSD kernels (probably
327 result value equals $length one can assume that $length bytes have 453 others, too), but that might fail, so you really really should check
328 been read. 454 the return value of "aio_sendfile" - fewer bytes than expected might
455 have been transferred.
329 456
330 aio_readahead $fh,$offset,$length, $callback->($retval) 457 aio_readahead $fh,$offset,$length, $callback->($retval)
331 "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
332 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
333 $offset argument specifies the starting point from which data is to 460 $offset argument specifies the starting point from which data is to
… …
336 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
337 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
338 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
339 is left unchanged. 466 is left unchanged.
340 467
341 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
342 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
343 similar effect. 470 similar effect.
344 471
345 aio_stat $fh_or_path, $callback->($status) 472 aio_stat $fh_or_path, $callback->($status)
346 aio_lstat $fh, $callback->($status) 473 aio_lstat $fh, $callback->($status)
… …
354 Currently, the stats are always 64-bit-stats, i.e. instead of 481 Currently, the stats are always 64-bit-stats, i.e. instead of
355 returning an error when stat'ing a large file, the results will be 482 returning an error when stat'ing a large file, the results will be
356 silently truncated unless perl itself is compiled with large file 483 silently truncated unless perl itself is compiled with large file
357 support. 484 support.
358 485
486 To help interpret the mode and dev/rdev stat values, IO::AIO offers
487 the following constants and functions (if not implemented, the
488 constants will be 0 and the functions will either "croak" or fall
489 back on traditional behaviour).
490
491 "S_IFMT", "S_IFIFO", "S_IFCHR", "S_IFBLK", "S_IFLNK", "S_IFREG",
492 "S_IFDIR", "S_IFWHT", "S_IFSOCK", "IO::AIO::major $dev_t",
493 "IO::AIO::minor $dev_t", "IO::AIO::makedev $major, $minor".
494
495 To access higher resolution stat timestamps, see "SUBSECOND STAT
496 TIME ACCESS".
497
359 Example: Print the length of /etc/passwd: 498 Example: Print the length of /etc/passwd:
360 499
361 aio_stat "/etc/passwd", sub { 500 aio_stat "/etc/passwd", sub {
362 $_[0] and die "stat failed: $!"; 501 $_[0] and die "stat failed: $!";
363 print "size is ", -s _, "\n"; 502 print "size is ", -s _, "\n";
364 }; 503 };
365 504
505 aio_statvfs $fh_or_path, $callback->($statvfs)
506 Works like the POSIX "statvfs" or "fstatvfs" syscalls, depending on
507 whether a file handle or path was passed.
508
509 On success, the callback is passed a hash reference with the
510 following members: "bsize", "frsize", "blocks", "bfree", "bavail",
511 "files", "ffree", "favail", "fsid", "flag" and "namemax". On
512 failure, "undef" is passed.
513
514 The following POSIX IO::AIO::ST_* constants are defined: "ST_RDONLY"
515 and "ST_NOSUID".
516
517 The following non-POSIX IO::AIO::ST_* flag masks are defined to
518 their correct value when available, or to 0 on systems that do not
519 support them: "ST_NODEV", "ST_NOEXEC", "ST_SYNCHRONOUS",
520 "ST_MANDLOCK", "ST_WRITE", "ST_APPEND", "ST_IMMUTABLE",
521 "ST_NOATIME", "ST_NODIRATIME" and "ST_RELATIME".
522
523 Example: stat "/wd" and dump out the data if successful.
524
525 aio_statvfs "/wd", sub {
526 my $f = $_[0]
527 or die "statvfs: $!";
528
529 use Data::Dumper;
530 say Dumper $f;
531 };
532
533 # result:
534 {
535 bsize => 1024,
536 bfree => 4333064312,
537 blocks => 10253828096,
538 files => 2050765568,
539 flag => 4096,
540 favail => 2042092649,
541 bavail => 4333064312,
542 ffree => 2042092649,
543 namemax => 255,
544 frsize => 1024,
545 fsid => 1810
546 }
547
366 aio_utime $fh_or_path, $atime, $mtime, $callback->($status) 548 aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
367 Works like perl's "utime" function (including the special case of 549 Works like perl's "utime" function (including the special case of
368 $atime and $mtime being undef). Fractional times are supported if 550 $atime and $mtime being undef). Fractional times are supported if
369 the underlying syscalls support them. 551 the underlying syscalls support them.
370 552
… …
392 aio_chown "path", 0, undef; 574 aio_chown "path", 0, undef;
393 575
394 aio_truncate $fh_or_path, $offset, $callback->($status) 576 aio_truncate $fh_or_path, $offset, $callback->($status)
395 Works like truncate(2) or ftruncate(2). 577 Works like truncate(2) or ftruncate(2).
396 578
579 aio_allocate $fh, $mode, $offset, $len, $callback->($status)
580 Allocates or frees disk space according to the $mode argument. See
581 the linux "fallocate" documentation for details.
582
583 $mode is usually 0 or "IO::AIO::FALLOC_FL_KEEP_SIZE" to allocate
584 space, or "IO::AIO::FALLOC_FL_PUNCH_HOLE |
585 IO::AIO::FALLOC_FL_KEEP_SIZE", to deallocate a file range.
586
587 IO::AIO also supports "FALLOC_FL_COLLAPSE_RANGE", to remove a range
588 (without leaving a hole), "FALLOC_FL_ZERO_RANGE", to zero a range,
589 "FALLOC_FL_INSERT_RANGE" to insert a range and
590 "FALLOC_FL_UNSHARE_RANGE" to unshare shared blocks (see your
591 fallocate(2) manpage).
592
593 The file system block size used by "fallocate" is presumably the
594 "f_bsize" returned by "statvfs", but different filesystems and
595 filetypes can dictate other limitations.
596
597 If "fallocate" isn't available or cannot be emulated (currently no
598 emulation will be attempted), passes -1 and sets $! to "ENOSYS".
599
397 aio_chmod $fh_or_path, $mode, $callback->($status) 600 aio_chmod $fh_or_path, $mode, $callback->($status)
398 Works like perl's "chmod" function. 601 Works like perl's "chmod" function.
399 602
400 aio_unlink $pathname, $callback->($status) 603 aio_unlink $pathname, $callback->($status)
401 Asynchronously unlink (delete) a file and call the callback with the 604 Asynchronously unlink (delete) a file and call the callback with the
402 result code. 605 result code.
403 606
404 aio_mknod $path, $mode, $dev, $callback->($status) 607 aio_mknod $pathname, $mode, $dev, $callback->($status)
405 [EXPERIMENTAL] 608 [EXPERIMENTAL]
406 609
407 Asynchronously create a device node (or fifo). See mknod(2). 610 Asynchronously create a device node (or fifo). See mknod(2).
408 611
409 The only (POSIX-) portable way of calling this function is: 612 The only (POSIX-) portable way of calling this function is:
410 613
411 aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ... 614 aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
615
616 See "aio_stat" for info about some potentially helpful extra
617 constants and functions.
412 618
413 aio_link $srcpath, $dstpath, $callback->($status) 619 aio_link $srcpath, $dstpath, $callback->($status)
414 Asynchronously create a new link to the existing object at $srcpath 620 Asynchronously create a new link to the existing object at $srcpath
415 at the path $dstpath and call the callback with the result code. 621 at the path $dstpath and call the callback with the result code.
416 622
417 aio_symlink $srcpath, $dstpath, $callback->($status) 623 aio_symlink $srcpath, $dstpath, $callback->($status)
418 Asynchronously create a new symbolic link to the existing object at 624 Asynchronously create a new symbolic link to the existing object at
419 $srcpath at the path $dstpath and call the callback with the result 625 $srcpath at the path $dstpath and call the callback with the result
420 code. 626 code.
421 627
422 aio_readlink $path, $callback->($link) 628 aio_readlink $pathname, $callback->($link)
423 Asynchronously read the symlink specified by $path and pass it to 629 Asynchronously read the symlink specified by $path and pass it to
424 the callback. If an error occurs, nothing or undef gets passed to 630 the callback. If an error occurs, nothing or undef gets passed to
425 the callback. 631 the callback.
426 632
633 aio_realpath $pathname, $callback->($path)
634 Asynchronously make the path absolute and resolve any symlinks in
635 $path. The resulting path only consists of directories (same as
636 Cwd::realpath).
637
638 This request can be used to get the absolute path of the current
639 working directory by passing it a path of . (a single dot).
640
427 aio_rename $srcpath, $dstpath, $callback->($status) 641 aio_rename $srcpath, $dstpath, $callback->($status)
428 Asynchronously rename the object at $srcpath to $dstpath, just as 642 Asynchronously rename the object at $srcpath to $dstpath, just as
429 rename(2) and call the callback with the result code. 643 rename(2) and call the callback with the result code.
644
645 On systems that support the AIO::WD working directory abstraction
646 natively, the case "[$wd, "."]" as $srcpath is specialcased -
647 instead of failing, "rename" is called on the absolute path of $wd.
648
649 aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
650 Basically a version of "aio_rename" with an additional $flags
651 argument. Calling this with "$flags=0" is the same as calling
652 "aio_rename".
653
654 Non-zero flags are currently only supported on GNU/Linux systems
655 that support renameat2. Other systems fail with "ENOSYS" in this
656 case.
657
658 The following constants are available (missing ones are, as usual
659 0), see renameat2(2) for details:
660
661 "IO::AIO::RENAME_NOREPLACE", "IO::AIO::RENAME_EXCHANGE" and
662 "IO::AIO::RENAME_WHITEOUT".
430 663
431 aio_mkdir $pathname, $mode, $callback->($status) 664 aio_mkdir $pathname, $mode, $callback->($status)
432 Asynchronously mkdir (create) a directory and call the callback with 665 Asynchronously mkdir (create) a directory and call the callback with
433 the result code. $mode will be modified by the umask at the time the 666 the result code. $mode will be modified by the umask at the time the
434 request is executed, so do not change your umask. 667 request is executed, so do not change your umask.
435 668
436 aio_rmdir $pathname, $callback->($status) 669 aio_rmdir $pathname, $callback->($status)
437 Asynchronously rmdir (delete) a directory and call the callback with 670 Asynchronously rmdir (delete) a directory and call the callback with
438 the result code. 671 the result code.
439 672
673 On systems that support the AIO::WD working directory abstraction
674 natively, the case "[$wd, "."]" is specialcased - instead of
675 failing, "rmdir" is called on the absolute path of $wd.
676
440 aio_readdir $pathname, $callback->($entries) 677 aio_readdir $pathname, $callback->($entries)
441 Unlike the POSIX call of the same name, "aio_readdir" reads an 678 Unlike the POSIX call of the same name, "aio_readdir" reads an
442 entire directory (i.e. opendir + readdir + closedir). The entries 679 entire directory (i.e. opendir + readdir + closedir). The entries
443 will not be sorted, and will NOT include the "." and ".." entries. 680 will not be sorted, and will NOT include the "." and ".." entries.
444 681
445 The callback a single argument which is either "undef" or an 682 The callback is passed a single argument which is either "undef" or
446 array-ref with the filenames. 683 an array-ref with the filenames.
447 684
685 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
686 Quite similar to "aio_readdir", but the $flags argument allows one
687 to tune behaviour and output format. In case of an error, $entries
688 will be "undef".
689
690 The flags are a combination of the following constants, ORed
691 together (the flags will also be passed to the callback, possibly
692 modified):
693
694 IO::AIO::READDIR_DENTS
695 Normally the callback gets an arrayref consisting of names only
696 (as with "aio_readdir"). If this flag is set, then the callback
697 gets an arrayref with "[$name, $type, $inode]" arrayrefs, each
698 describing a single directory entry in more detail:
699
700 $name is the name of the entry.
701
702 $type is one of the "IO::AIO::DT_xxx" constants:
703
704 "IO::AIO::DT_UNKNOWN", "IO::AIO::DT_FIFO", "IO::AIO::DT_CHR",
705 "IO::AIO::DT_DIR", "IO::AIO::DT_BLK", "IO::AIO::DT_REG",
706 "IO::AIO::DT_LNK", "IO::AIO::DT_SOCK", "IO::AIO::DT_WHT".
707
708 "IO::AIO::DT_UNKNOWN" means just that: readdir does not know. If
709 you need to know, you have to run stat yourself. Also, for
710 speed/memory reasons, the $type scalars are read-only: you must
711 not modify them.
712
713 $inode is the inode number (which might not be exact on systems
714 with 64 bit inode numbers and 32 bit perls). This field has
715 unspecified content on systems that do not deliver the inode
716 information.
717
718 IO::AIO::READDIR_DIRS_FIRST
719 When this flag is set, then the names will be returned in an
720 order where likely directories come first, in optimal stat
721 order. This is useful when you need to quickly find directories,
722 or you want to find all directories while avoiding to stat()
723 each entry.
724
725 If the system returns type information in readdir, then this is
726 used to find directories directly. Otherwise, likely directories
727 are names beginning with ".", or otherwise names with no dots,
728 of which names with short names are tried first.
729
730 IO::AIO::READDIR_STAT_ORDER
731 When this flag is set, then the names will be returned in an
732 order suitable for stat()'ing each one. That is, when you plan
733 to stat() most or all files in the given directory, then the
734 returned order will likely be faster.
735
736 If both this flag and "IO::AIO::READDIR_DIRS_FIRST" are
737 specified, then the likely dirs come first, resulting in a less
738 optimal stat order for stat'ing all entries, but likely a more
739 optimal order for finding subdirectories.
740
741 IO::AIO::READDIR_FOUND_UNKNOWN
742 This flag should not be set when calling "aio_readdirx".
743 Instead, it is being set by "aio_readdirx", when any of the
744 $type's found were "IO::AIO::DT_UNKNOWN". The absence of this
745 flag therefore indicates that all $type's are known, which can
746 be used to speed up some algorithms.
747
748 aio_slurp $pathname, $offset, $length, $data, $callback->($status)
749 Opens, reads and closes the given file. The data is put into $data,
750 which is resized as required.
751
752 If $offset is negative, then it is counted from the end of the file.
753
754 If $length is zero, then the remaining length of the file is used.
755 Also, in this case, the same limitations to modifying $data apply as
756 when IO::AIO::mmap is used, i.e. it must only be modified in-place
757 with "substr". If the size of the file is known, specifying a
758 non-zero $length results in a performance advantage.
759
760 This request is similar to the older "aio_load" request, but since
761 it is a single request, it might be more efficient to use.
762
763 Example: load /etc/passwd into $passwd.
764
765 my $passwd;
766 aio_slurp "/etc/passwd", 0, 0, $passwd, sub {
767 $_[0] >= 0
768 or die "/etc/passwd: $!\n";
769
770 printf "/etc/passwd is %d bytes long, and contains:\n", length $passwd;
771 print $passwd;
772 };
773 IO::AIO::flush;
774
448 aio_load $path, $data, $callback->($status) 775 aio_load $pathname, $data, $callback->($status)
449 This is a composite request that tries to fully load the given file 776 This is a composite request that tries to fully load the given file
450 into memory. Status is the same as with aio_read. 777 into memory. Status is the same as with aio_read.
778
779 Using "aio_slurp" might be more efficient, as it is a single
780 request.
451 781
452 aio_copy $srcpath, $dstpath, $callback->($status) 782 aio_copy $srcpath, $dstpath, $callback->($status)
453 Try to copy the *file* (directories not supported as either source 783 Try to copy the *file* (directories not supported as either source
454 or destination) from $srcpath to $dstpath and call the callback with 784 or destination) from $srcpath to $dstpath and call the callback with
455 the 0 (error) or -1 ok. 785 a status of 0 (ok) or -1 (error, see $!).
456 786
787 Existing destination files will be truncated.
788
457 This is a composite request that it creates the destination file 789 This is a composite request that creates the destination file with
458 with mode 0200 and copies the contents of the source file into it 790 mode 0200 and copies the contents of the source file into it using
459 using "aio_sendfile", followed by restoring atime, mtime, access 791 "aio_sendfile", followed by restoring atime, mtime, access mode and
460 mode and uid/gid, in that order. 792 uid/gid, in that order.
461 793
462 If an error occurs, the partial destination file will be unlinked, 794 If an error occurs, the partial destination file will be unlinked,
463 if possible, except when setting atime, mtime, access mode and 795 if possible, except when setting atime, mtime, access mode and
464 uid/gid, where errors are being ignored. 796 uid/gid, where errors are being ignored.
465 797
466 aio_move $srcpath, $dstpath, $callback->($status) 798 aio_move $srcpath, $dstpath, $callback->($status)
467 Try to move the *file* (directories not supported as either source 799 Try to move the *file* (directories not supported as either source
468 or destination) from $srcpath to $dstpath and call the callback with 800 or destination) from $srcpath to $dstpath and call the callback with
469 the 0 (error) or -1 ok. 801 a status of 0 (ok) or -1 (error, see $!).
470 802
471 This is a composite request that tries to rename(2) the file first. 803 This is a composite request that tries to rename(2) the file first;
472 If rename files with "EXDEV", it copies the file with "aio_copy" 804 if rename fails with "EXDEV", it copies the file with "aio_copy"
473 and, if that is successful, unlinking the $srcpath. 805 and, if that is successful, unlinks the $srcpath.
474 806
475 aio_scandir $path, $maxreq, $callback->($dirs, $nondirs) 807 aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
476 Scans a directory (similar to "aio_readdir") but additionally tries 808 Scans a directory (similar to "aio_readdir") but additionally tries
477 to efficiently separate the entries of directory $path into two sets 809 to efficiently separate the entries of directory $path into two sets
478 of names, directories you can recurse into (directories), and ones 810 of names, directories you can recurse into (directories), and ones
479 you cannot recurse into (everything else, including symlinks to 811 you cannot recurse into (everything else, including symlinks to
480 directories). 812 directories).
481 813
482 "aio_scandir" is a composite request that creates of many sub 814 "aio_scandir" is a composite request that generates many sub
483 requests_ $maxreq specifies the maximum number of outstanding aio 815 requests. $maxreq specifies the maximum number of outstanding aio
484 requests that this function generates. If it is "<= 0", then a 816 requests that this function generates. If it is "<= 0", then a
485 suitable default will be chosen (currently 4). 817 suitable default will be chosen (currently 4).
486 818
487 On error, the callback is called without arguments, otherwise it 819 On error, the callback is called without arguments, otherwise it
488 receives two array-refs with path-relative entry names. 820 receives two array-refs with path-relative entry names.
… …
498 Implementation notes. 830 Implementation notes.
499 831
500 The "aio_readdir" cannot be avoided, but "stat()"'ing every entry 832 The "aio_readdir" cannot be avoided, but "stat()"'ing every entry
501 can. 833 can.
502 834
835 If readdir returns file type information, then this is used directly
836 to find directories.
837
503 After reading the directory, the modification time, size etc. of the 838 Otherwise, after reading the directory, the modification time, size
504 directory before and after the readdir is checked, and if they match 839 etc. of the directory before and after the readdir is checked, and
505 (and isn't the current time), the link count will be used to decide 840 if they match (and isn't the current time), the link count will be
506 how many entries are directories (if >= 2). Otherwise, no knowledge 841 used to decide how many entries are directories (if >= 2).
507 of the number of subdirectories will be assumed. 842 Otherwise, no knowledge of the number of subdirectories will be
843 assumed.
508 844
509 Then entries will be sorted into likely directories (everything 845 Then entries will be sorted into likely directories a non-initial
510 without a non-initial dot currently) and likely non-directories 846 dot currently) and likely non-directories (see "aio_readdirx"). Then
511 (everything else). Then every entry plus an appended "/." will be 847 every entry plus an appended "/." will be "stat"'ed, likely
512 "stat"'ed, likely directories first. If that succeeds, it assumes 848 directories first, in order of their inode numbers. If that
513 that the entry is a directory or a symlink to directory (which will 849 succeeds, it assumes that the entry is a directory or a symlink to
514 be checked seperately). This is often faster than stat'ing the entry 850 directory (which will be checked separately). This is often faster
515 itself because filesystems might detect the type of the entry 851 than stat'ing the entry itself because filesystems might detect the
516 without reading the inode data (e.g. ext2fs filetype feature). 852 type of the entry without reading the inode data (e.g. ext2fs
853 filetype feature), even on systems that cannot return the filetype
854 information on readdir.
517 855
518 If the known number of directories (link count - 2) has been 856 If the known number of directories (link count - 2) has been
519 reached, the rest of the entries is assumed to be non-directories. 857 reached, the rest of the entries is assumed to be non-directories.
520 858
521 This only works with certainty on POSIX (= UNIX) filesystems, which 859 This only works with certainty on POSIX (= UNIX) filesystems, which
… …
523 861
524 It will also likely work on non-POSIX filesystems with reduced 862 It will also likely work on non-POSIX filesystems with reduced
525 efficiency as those tend to return 0 or 1 as link counts, which 863 efficiency as those tend to return 0 or 1 as link counts, which
526 disables the directory counting heuristic. 864 disables the directory counting heuristic.
527 865
528 aio_rmtree $path, $callback->($status) 866 aio_rmtree $pathname, $callback->($status)
529 Delete a directory tree starting (and including) $path, return the 867 Delete a directory tree starting (and including) $path, return the
530 status of the final "rmdir" only. This is a composite request that 868 status of the final "rmdir" only. This is a composite request that
531 uses "aio_scandir" to recurse into and rmdir directories, and unlink 869 uses "aio_scandir" to recurse into and rmdir directories, and unlink
532 everything else. 870 everything else.
533 871
872 aio_fcntl $fh, $cmd, $arg, $callback->($status)
873 aio_ioctl $fh, $request, $buf, $callback->($status)
874 These work just like the "fcntl" and "ioctl" built-in functions,
875 except they execute asynchronously and pass the return value to the
876 callback.
877
878 Both calls can be used for a lot of things, some of which make more
879 sense to run asynchronously in their own thread, while some others
880 make less sense. For example, calls that block waiting for external
881 events, such as locking, will also lock down an I/O thread while it
882 is waiting, which can deadlock the whole I/O system. At the same
883 time, there might be no alternative to using a thread to wait.
884
885 So in general, you should only use these calls for things that do
886 (filesystem) I/O, not for things that wait for other events
887 (network, other processes), although if you are careful and know
888 what you are doing, you still can.
889
890 The following constants are available (missing ones are, as usual
891 0):
892
893 "F_DUPFD_CLOEXEC",
894
895 "F_OFD_GETLK", "F_OFD_SETLK", "F_OFD_GETLKW",
896
897 "FIFREEZE", "FITHAW", "FITRIM", "FICLONE", "FICLONERANGE",
898 "FIDEDUPERANGE".
899
900 "FS_IOC_GETFLAGS", "FS_IOC_SETFLAGS", "FS_IOC_GETVERSION",
901 "FS_IOC_SETVERSION", "FS_IOC_FIEMAP".
902
903 "FS_IOC_FSGETXATTR", "FS_IOC_FSSETXATTR",
904 "FS_IOC_SET_ENCRYPTION_POLICY", "FS_IOC_GET_ENCRYPTION_PWSALT",
905 "FS_IOC_GET_ENCRYPTION_POLICY", "FS_KEY_DESCRIPTOR_SIZE".
906
907 "FS_SECRM_FL", "FS_UNRM_FL", "FS_COMPR_FL", "FS_SYNC_FL",
908 "FS_IMMUTABLE_FL", "FS_APPEND_FL", "FS_NODUMP_FL", "FS_NOATIME_FL",
909 "FS_DIRTY_FL", "FS_COMPRBLK_FL", "FS_NOCOMP_FL", "FS_ENCRYPT_FL",
910 "FS_BTREE_FL", "FS_INDEX_FL", "FS_JOURNAL_DATA_FL", "FS_NOTAIL_FL",
911 "FS_DIRSYNC_FL", "FS_TOPDIR_FL", "FS_FL_USER_MODIFIABLE".
912
913 "FS_XFLAG_REALTIME", "FS_XFLAG_PREALLOC", "FS_XFLAG_IMMUTABLE",
914 "FS_XFLAG_APPEND", "FS_XFLAG_SYNC", "FS_XFLAG_NOATIME",
915 "FS_XFLAG_NODUMP", "FS_XFLAG_RTINHERIT", "FS_XFLAG_PROJINHERIT",
916 "FS_XFLAG_NOSYMLINKS", "FS_XFLAG_EXTSIZE", "FS_XFLAG_EXTSZINHERIT",
917 "FS_XFLAG_NODEFRAG", "FS_XFLAG_FILESTREAM", "FS_XFLAG_DAX",
918 "FS_XFLAG_HASATTR",
919
920 aio_sync $callback->($status)
921 Asynchronously call sync and call the callback when finished.
922
534 aio_fsync $fh, $callback->($status) 923 aio_fsync $fh, $callback->($status)
535 Asynchronously call fsync on the given filehandle and call the 924 Asynchronously call fsync on the given filehandle and call the
536 callback with the fsync result code. 925 callback with the fsync result code.
537 926
538 aio_fdatasync $fh, $callback->($status) 927 aio_fdatasync $fh, $callback->($status)
539 Asynchronously call fdatasync on the given filehandle and call the 928 Asynchronously call fdatasync on the given filehandle and call the
540 callback with the fdatasync result code. 929 callback with the fdatasync result code.
541 930
542 If this call isn't available because your OS lacks it or it couldn't 931 If this call isn't available because your OS lacks it or it couldn't
543 be detected, it will be emulated by calling "fsync" instead. 932 be detected, it will be emulated by calling "fsync" instead.
933
934 aio_syncfs $fh, $callback->($status)
935 Asynchronously call the syncfs syscall to sync the filesystem
936 associated to the given filehandle and call the callback with the
937 syncfs result code. If syncfs is not available, calls sync(), but
938 returns -1 and sets errno to "ENOSYS" nevertheless.
939
940 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
941 Sync the data portion of the file specified by $offset and $length
942 to disk (but NOT the metadata), by calling the Linux-specific
943 sync_file_range call. If sync_file_range is not available or it
944 returns ENOSYS, then fdatasync or fsync is being substituted.
945
946 $flags can be a combination of
947 "IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE",
948 "IO::AIO::SYNC_FILE_RANGE_WRITE" and
949 "IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER": refer to the sync_file_range
950 manpage for details.
951
952 aio_pathsync $pathname, $callback->($status)
953 This request tries to open, fsync and close the given path. This is
954 a composite request intended to sync directories after directory
955 operations (E.g. rename). This might not work on all operating
956 systems or have any specific effect, but usually it makes sure that
957 directory changes get written to disc. It works for anything that
958 can be opened for read-only, not just directories.
959
960 Future versions of this function might fall back to other methods
961 when "fsync" on the directory fails (such as calling "sync").
962
963 Passes 0 when everything went ok, and -1 on error.
964
965 aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC,
966 $callback->($status)
967 This is a rather advanced IO::AIO call, which only works on
968 mmap(2)ed scalars (see the "IO::AIO::mmap" function, although it
969 also works on data scalars managed by the Sys::Mmap or Mmap modules,
970 note that the scalar must only be modified in-place while an aio
971 operation is pending on it).
972
973 It calls the "msync" function of your OS, if available, with the
974 memory area starting at $offset in the string and ending $length
975 bytes later. If $length is negative, counts from the end, and if
976 $length is "undef", then it goes till the end of the string. The
977 flags can be either "IO::AIO::MS_ASYNC" or "IO::AIO::MS_SYNC", plus
978 an optional "IO::AIO::MS_INVALIDATE".
979
980 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0,
981 $callback->($status)
982 This is a rather advanced IO::AIO call, which works best on
983 mmap(2)ed scalars.
984
985 It touches (reads or writes) all memory pages in the specified range
986 inside the scalar. All caveats and parameters are the same as for
987 "aio_msync", above, except for flags, which must be either 0 (which
988 reads all pages and ensures they are instantiated) or
989 "IO::AIO::MT_MODIFY", which modifies the memory pages (by reading
990 and writing an octet from it, which dirties the page).
991
992 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
993 This is a rather advanced IO::AIO call, which works best on
994 mmap(2)ed scalars.
995
996 It reads in all the pages of the underlying storage into memory (if
997 any) and locks them, so they are not getting swapped/paged out or
998 removed.
999
1000 If $length is undefined, then the scalar will be locked till the
1001 end.
1002
1003 On systems that do not implement "mlock", this function returns -1
1004 and sets errno to "ENOSYS".
1005
1006 Note that the corresponding "munlock" is synchronous and is
1007 documented under "MISCELLANEOUS FUNCTIONS".
1008
1009 Example: open a file, mmap and mlock it - both will be undone when
1010 $data gets destroyed.
1011
1012 open my $fh, "<", $path or die "$path: $!";
1013 my $data;
1014 IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
1015 aio_mlock $data; # mlock in background
1016
1017 aio_mlockall $flags, $callback->($status)
1018 Calls the "mlockall" function with the given $flags (a combination
1019 of "IO::AIO::MCL_CURRENT" and "IO::AIO::MCL_FUTURE").
1020
1021 On systems that do not implement "mlockall", this function returns
1022 -1 and sets errno to "ENOSYS".
1023
1024 Note that the corresponding "munlockall" is synchronous and is
1025 documented under "MISCELLANEOUS FUNCTIONS".
1026
1027 Example: asynchronously lock all current and future pages into
1028 memory.
1029
1030 aio_mlockall IO::AIO::MCL_FUTURE;
1031
1032 aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
1033 Queries the extents of the given file (by calling the Linux "FIEMAP"
1034 ioctl, see <http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for
1035 details). If the ioctl is not available on your OS, then this
1036 request will fail with "ENOSYS".
1037
1038 $start is the starting offset to query extents for, $length is the
1039 size of the range to query - if it is "undef", then the whole file
1040 will be queried.
1041
1042 $flags is a combination of flags ("IO::AIO::FIEMAP_FLAG_SYNC" or
1043 "IO::AIO::FIEMAP_FLAG_XATTR" - "IO::AIO::FIEMAP_FLAGS_COMPAT" is
1044 also exported), and is normally 0 or "IO::AIO::FIEMAP_FLAG_SYNC" to
1045 query the data portion.
1046
1047 $count is the maximum number of extent records to return. If it is
1048 "undef", then IO::AIO queries all extents of the range. As a very
1049 special case, if it is 0, then the callback receives the number of
1050 extents instead of the extents themselves (which is unreliable, see
1051 below).
1052
1053 If an error occurs, the callback receives no arguments. The special
1054 "errno" value "IO::AIO::EBADR" is available to test for flag errors.
1055
1056 Otherwise, the callback receives an array reference with extent
1057 structures. Each extent structure is an array reference itself, with
1058 the following members:
1059
1060 [$logical, $physical, $length, $flags]
1061
1062 Flags is any combination of the following flag values (typically
1063 either 0 or "IO::AIO::FIEMAP_EXTENT_LAST" (1)):
1064
1065 "IO::AIO::FIEMAP_EXTENT_LAST", "IO::AIO::FIEMAP_EXTENT_UNKNOWN",
1066 "IO::AIO::FIEMAP_EXTENT_DELALLOC", "IO::AIO::FIEMAP_EXTENT_ENCODED",
1067 "IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED",
1068 "IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED",
1069 "IO::AIO::FIEMAP_EXTENT_DATA_INLINE",
1070 "IO::AIO::FIEMAP_EXTENT_DATA_TAIL",
1071 "IO::AIO::FIEMAP_EXTENT_UNWRITTEN", "IO::AIO::FIEMAP_EXTENT_MERGED"
1072 or "IO::AIO::FIEMAP_EXTENT_SHARED".
1073
1074 At the time of this writing (Linux 3.2), this request is unreliable
1075 unless $count is "undef", as the kernel has all sorts of bugs
1076 preventing it to return all extents of a range for files with a
1077 large number of extents. The code (only) works around all these
1078 issues if $count is "undef".
544 1079
545 aio_group $callback->(...) 1080 aio_group $callback->(...)
546 This is a very special aio request: Instead of doing something, it 1081 This is a very special aio request: Instead of doing something, it
547 is a container for other aio requests, which is useful if you want 1082 is a container for other aio requests, which is useful if you want
548 to bundle many requests into a single, composite, request with a 1083 to bundle many requests into a single, composite, request with a
… …
583 requests like sleep and file handle readable/writable, the overhead 1118 requests like sleep and file handle readable/writable, the overhead
584 this creates is immense (it blocks a thread for a long time) so do 1119 this creates is immense (it blocks a thread for a long time) so do
585 not use this function except to put your application under 1120 not use this function except to put your application under
586 artificial I/O pressure. 1121 artificial I/O pressure.
587 1122
1123 IO::AIO::WD - multiple working directories
1124 Your process only has one current working directory, which is used by
1125 all threads. This makes it hard to use relative paths (some other
1126 component could call "chdir" at any time, and it is hard to control when
1127 the path will be used by IO::AIO).
1128
1129 One solution for this is to always use absolute paths. This usually
1130 works, but can be quite slow (the kernel has to walk the whole path on
1131 every access), and can also be a hassle to implement.
1132
1133 Newer POSIX systems have a number of functions (openat, fdopendir,
1134 futimensat and so on) that make it possible to specify working
1135 directories per operation.
1136
1137 For portability, and because the clowns who "designed", or shall I
1138 write, perpetrated this new interface were obviously half-drunk, this
1139 abstraction cannot be perfect, though.
1140
1141 IO::AIO allows you to convert directory paths into a so-called
1142 IO::AIO::WD object. This object stores the canonicalised, absolute
1143 version of the path, and on systems that allow it, also a directory file
1144 descriptor.
1145
1146 Everywhere where a pathname is accepted by IO::AIO (e.g. in "aio_stat"
1147 or "aio_unlink"), one can specify an array reference with an IO::AIO::WD
1148 object and a pathname instead (or the IO::AIO::WD object alone, which
1149 gets interpreted as "[$wd, "."]"). If the pathname is absolute, the
1150 IO::AIO::WD object is ignored, otherwise the pathname is resolved
1151 relative to that IO::AIO::WD object.
1152
1153 For example, to get a wd object for /etc and then stat passwd inside,
1154 you would write:
1155
1156 aio_wd "/etc", sub {
1157 my $etcdir = shift;
1158
1159 # although $etcdir can be undef on error, there is generally no reason
1160 # to check for errors here, as aio_stat will fail with ENOENT
1161 # when $etcdir is undef.
1162
1163 aio_stat [$etcdir, "passwd"], sub {
1164 # yay
1165 };
1166 };
1167
1168 The fact that "aio_wd" is a request and not a normal function shows that
1169 creating an IO::AIO::WD object is itself a potentially blocking
1170 operation, which is why it is done asynchronously.
1171
1172 To stat the directory obtained with "aio_wd" above, one could write
1173 either of the following three request calls:
1174
1175 aio_lstat "/etc" , sub { ... # pathname as normal string
1176 aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
1177 aio_lstat $wd , sub { ... # shorthand for the previous
1178
1179 As with normal pathnames, IO::AIO keeps a copy of the working directory
1180 object and the pathname string, so you could write the following without
1181 causing any issues due to $path getting reused:
1182
1183 my $path = [$wd, undef];
1184
1185 for my $name (qw(abc def ghi)) {
1186 $path->[1] = $name;
1187 aio_stat $path, sub {
1188 # ...
1189 };
1190 }
1191
1192 There are some caveats: when directories get renamed (or deleted), the
1193 pathname string doesn't change, so will point to the new directory (or
1194 nowhere at all), while the directory fd, if available on the system,
1195 will still point to the original directory. Most functions accepting a
1196 pathname will use the directory fd on newer systems, and the string on
1197 older systems. Some functions (such as "aio_realpath") will always rely
1198 on the string form of the pathname.
1199
1200 So this functionality is mainly useful to get some protection against
1201 "chdir", to easily get an absolute path out of a relative path for
1202 future reference, and to speed up doing many operations in the same
1203 directory (e.g. when stat'ing all files in a directory).
1204
1205 The following functions implement this working directory abstraction:
1206
1207 aio_wd $pathname, $callback->($wd)
1208 Asynchonously canonicalise the given pathname and convert it to an
1209 IO::AIO::WD object representing it. If possible and supported on the
1210 system, also open a directory fd to speed up pathname resolution
1211 relative to this working directory.
1212
1213 If something goes wrong, then "undef" is passwd to the callback
1214 instead of a working directory object and $! is set appropriately.
1215 Since passing "undef" as working directory component of a pathname
1216 fails the request with "ENOENT", there is often no need for error
1217 checking in the "aio_wd" callback, as future requests using the
1218 value will fail in the expected way.
1219
1220 IO::AIO::CWD
1221 This is a compiletime constant (object) that represents the process
1222 current working directory.
1223
1224 Specifying this object as working directory object for a pathname is
1225 as if the pathname would be specified directly, without a directory
1226 object. For example, these calls are functionally identical:
1227
1228 aio_stat "somefile", sub { ... };
1229 aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
1230
1231 To recover the path associated with an IO::AIO::WD object, you can use
1232 "aio_realpath":
1233
1234 aio_realpath $wd, sub {
1235 warn "path is $_[0]\n";
1236 };
1237
1238 Currently, "aio_statvfs" always, and "aio_rename" and "aio_rmdir"
1239 sometimes, fall back to using an absolue path.
1240
588 IO::AIO::REQ CLASS 1241 IO::AIO::REQ CLASS
589 All non-aggregate "aio_*" functions return an object of this class when 1242 All non-aggregate "aio_*" functions return an object of this class when
590 called in non-void context. 1243 called in non-void context.
591 1244
592 cancel $req 1245 cancel $req
593 Cancels the request, if possible. Has the effect of skipping 1246 Cancels the request, if possible. Has the effect of skipping
594 execution when entering the execute state and skipping calling the 1247 execution when entering the execute state and skipping calling the
595 callback when entering the the result state, but will leave the 1248 callback when entering the the result state, but will leave the
596 request otherwise untouched. That means that requests that currently 1249 request otherwise untouched (with the exception of readdir). That
597 execute will not be stopped and resources held by the request will 1250 means that requests that currently execute will not be stopped and
598 not be freed prematurely. 1251 resources held by the request will not be freed prematurely.
599 1252
600 cb $req $callback->(...) 1253 cb $req $callback->(...)
601 Replace (or simply set) the callback registered to the request. 1254 Replace (or simply set) the callback registered to the request.
602 1255
603 IO::AIO::GRP CLASS 1256 IO::AIO::GRP CLASS
… …
630 }; 1283 };
631 1284
632 This makes it very easy to create composite requests (see the source of 1285 This makes it very easy to create composite requests (see the source of
633 "aio_move" for an application) that work and feel like simple requests. 1286 "aio_move" for an application) that work and feel like simple requests.
634 1287
635 * The IO::AIO::GRP objects will be cleaned up during calls to 1288 * The IO::AIO::GRP objects will be cleaned up during calls to
636 "IO::AIO::poll_cb", just like any other request. 1289 "IO::AIO::poll_cb", just like any other request.
1290
637 * They can be canceled like any other request. Canceling will cancel not 1291 * They can be canceled like any other request. Canceling will cancel
638 only the request itself, but also all requests it contains. 1292 not only the request itself, but also all requests it contains.
1293
639 * They can also can also be added to other IO::AIO::GRP objects. 1294 * They can also can also be added to other IO::AIO::GRP objects.
1295
640 * You must not add requests to a group from within the group callback 1296 * You must not add requests to a group from within the group callback
641 (or any later time). 1297 (or any later time).
642 1298
643 Their lifetime, simplified, looks like this: when they are empty, they 1299 Their lifetime, simplified, looks like this: when they are empty, they
644 will finish very quickly. If they contain only requests that are in the 1300 will finish very quickly. If they contain only requests that are in the
645 "done" state, they will also finish. Otherwise they will continue to 1301 "done" state, they will also finish. Otherwise they will continue to
646 exist. 1302 exist.
647 1303
648 That means after creating a group you have some time to add requests. 1304 That means after creating a group you have some time to add requests
649 And in the callbacks of those requests, you can add further requests to 1305 (precisely before the callback has been invoked, which is only done
650 the group. And only when all those requests have finished will the the 1306 within the "poll_cb"). And in the callbacks of those requests, you can
651 group itself finish. 1307 add further requests to the group. And only when all those requests have
1308 finished will the the group itself finish.
652 1309
653 add $grp ... 1310 add $grp ...
654 $grp->add (...) 1311 $grp->add (...)
655 Add one or more requests to the group. Any type of IO::AIO::REQ can 1312 Add one or more requests to the group. Any type of IO::AIO::REQ can
656 be added, including other groups, as long as you do not create 1313 be added, including other groups, as long as you do not create
… …
661 $grp->cancel_subs 1318 $grp->cancel_subs
662 Cancel all subrequests and clears any feeder, but not the group 1319 Cancel all subrequests and clears any feeder, but not the group
663 request itself. Useful when you queued a lot of events but got a 1320 request itself. Useful when you queued a lot of events but got a
664 result early. 1321 result early.
665 1322
1323 The group request will finish normally (you cannot add requests to
1324 the group).
1325
666 $grp->result (...) 1326 $grp->result (...)
667 Set the result value(s) that will be passed to the group callback 1327 Set the result value(s) that will be passed to the group callback
668 when all subrequests have finished and set thre groups errno to the 1328 when all subrequests have finished and set the groups errno to the
669 current value of errno (just like calling "errno" without an error 1329 current value of errno (just like calling "errno" without an error
670 number). By default, no argument will be passed and errno is zero. 1330 number). By default, no argument will be passed and errno is zero.
671 1331
672 $grp->errno ([$errno]) 1332 $grp->errno ([$errno])
673 Sets the group errno value to $errno, or the current value of errno 1333 Sets the group errno value to $errno, or the current value of errno
… …
684 Sets a feeder/generator on this group: every group can have an 1344 Sets a feeder/generator on this group: every group can have an
685 attached generator that generates requests if idle. The idea behind 1345 attached generator that generates requests if idle. The idea behind
686 this is that, although you could just queue as many requests as you 1346 this is that, although you could just queue as many requests as you
687 want in a group, this might starve other requests for a potentially 1347 want in a group, this might starve other requests for a potentially
688 long time. For example, "aio_scandir" might generate hundreds of 1348 long time. For example, "aio_scandir" might generate hundreds of
689 thousands "aio_stat" requests, delaying any later requests for a 1349 thousands of "aio_stat" requests, delaying any later requests for a
690 long time. 1350 long time.
691 1351
692 To avoid this, and allow incremental generation of requests, you can 1352 To avoid this, and allow incremental generation of requests, you can
693 instead a group and set a feeder on it that generates those 1353 instead a group and set a feeder on it that generates those
694 requests. The feed callback will be called whenever there are few 1354 requests. The feed callback will be called whenever there are few
… …
699 does not impose any limits). 1359 does not impose any limits).
700 1360
701 If the feed does not queue more requests when called, it will be 1361 If the feed does not queue more requests when called, it will be
702 automatically removed from the group. 1362 automatically removed from the group.
703 1363
704 If the feed limit is 0, it will be set to 2 automatically. 1364 If the feed limit is 0 when this method is called, it will be set to
1365 2 automatically.
705 1366
706 Example: 1367 Example:
707 1368
708 # stat all files in @files, but only ever use four aio requests concurrently: 1369 # stat all files in @files, but only ever use four aio requests concurrently:
709 1370
… …
720 Sets the feeder limit for the group: The feeder will be called 1381 Sets the feeder limit for the group: The feeder will be called
721 whenever the group contains less than this many requests. 1382 whenever the group contains less than this many requests.
722 1383
723 Setting the limit to 0 will pause the feeding process. 1384 Setting the limit to 0 will pause the feeding process.
724 1385
1386 The default value for the limit is 0, but note that setting a feeder
1387 automatically bumps it up to 2.
1388
725 SUPPORT FUNCTIONS 1389 SUPPORT FUNCTIONS
726 EVENT PROCESSING AND EVENT LOOP INTEGRATION 1390 EVENT PROCESSING AND EVENT LOOP INTEGRATION
727 $fileno = IO::AIO::poll_fileno 1391 $fileno = IO::AIO::poll_fileno
728 Return the *request result pipe file descriptor*. This filehandle 1392 Return the *request result pipe file descriptor*. This filehandle
729 must be polled for reading by some mechanism outside this module 1393 must be polled for reading by some mechanism outside this module
730 (e.g. Event or select, see below or the SYNOPSIS). If the pipe 1394 (e.g. EV, Glib, select and so on, see below or the SYNOPSIS). If the
731 becomes readable you have to call "poll_cb" to check the results. 1395 pipe becomes readable you have to call "poll_cb" to check the
1396 results.
732 1397
733 See "poll_cb" for an example. 1398 See "poll_cb" for an example.
734 1399
735 IO::AIO::poll_cb 1400 IO::AIO::poll_cb
736 Process some outstanding events on the result pipe. You have to call 1401 Process some requests that have reached the result phase (i.e. they
737 this regularly. Returns the number of events processed. Returns 1402 have been executed but the results are not yet reported). You have
1403 to call this "regularly" to finish outstanding requests.
1404
1405 Returns 0 if all events could be processed (or there were no events
1406 to process), or -1 if it returned earlier for whatever reason.
738 immediately when no events are outstanding. The amount of events 1407 Returns immediately when no events are outstanding. The amount of
739 processed depends on the settings of "IO::AIO::max_poll_req" and 1408 events processed depends on the settings of "IO::AIO::max_poll_req",
740 "IO::AIO::max_poll_time". 1409 "IO::AIO::max_poll_time" and "IO::AIO::max_outstanding".
741 1410
742 If not all requests were processed for whatever reason, the 1411 If not all requests were processed for whatever reason, the poll
743 filehandle will still be ready when "poll_cb" returns. 1412 file descriptor will still be ready when "poll_cb" returns, so
1413 normally you don't have to do anything special to have it called
1414 later.
1415
1416 Apart from calling "IO::AIO::poll_cb" when the event filehandle
1417 becomes ready, it can be beneficial to call this function from loops
1418 which submit a lot of requests, to make sure the results get
1419 processed when they become available and not just when the loop is
1420 finished and the event loop takes over again. This function returns
1421 very fast when there are no outstanding requests.
744 1422
745 Example: Install an Event watcher that automatically calls 1423 Example: Install an Event watcher that automatically calls
746 IO::AIO::poll_cb with high priority: 1424 IO::AIO::poll_cb with high priority (more examples can be found in
1425 the SYNOPSIS section, at the top of this document):
747 1426
748 Event->io (fd => IO::AIO::poll_fileno, 1427 Event->io (fd => IO::AIO::poll_fileno,
749 poll => 'r', async => 1, 1428 poll => 'r', async => 1,
750 cb => \&IO::AIO::poll_cb); 1429 cb => \&IO::AIO::poll_cb);
1430
1431 IO::AIO::poll_wait
1432 Wait until either at least one request is in the result phase or no
1433 requests are outstanding anymore.
1434
1435 This is useful if you want to synchronously wait for some requests
1436 to become ready, without actually handling them.
1437
1438 See "nreqs" for an example.
1439
1440 IO::AIO::poll
1441 Waits until some requests have been handled.
1442
1443 Returns the number of requests processed, but is otherwise strictly
1444 equivalent to:
1445
1446 IO::AIO::poll_wait, IO::AIO::poll_cb
1447
1448 IO::AIO::flush
1449 Wait till all outstanding AIO requests have been handled.
1450
1451 Strictly equivalent to:
1452
1453 IO::AIO::poll_wait, IO::AIO::poll_cb
1454 while IO::AIO::nreqs;
751 1455
752 IO::AIO::max_poll_reqs $nreqs 1456 IO::AIO::max_poll_reqs $nreqs
753 IO::AIO::max_poll_time $seconds 1457 IO::AIO::max_poll_time $seconds
754 These set the maximum number of requests (default 0, meaning 1458 These set the maximum number of requests (default 0, meaning
755 infinity) that are being processed by "IO::AIO::poll_cb" in one 1459 infinity) that are being processed by "IO::AIO::poll_cb" in one
… …
779 # use a low priority so other tasks have priority 1483 # use a low priority so other tasks have priority
780 Event->io (fd => IO::AIO::poll_fileno, 1484 Event->io (fd => IO::AIO::poll_fileno,
781 poll => 'r', nice => 1, 1485 poll => 'r', nice => 1,
782 cb => &IO::AIO::poll_cb); 1486 cb => &IO::AIO::poll_cb);
783 1487
784 IO::AIO::poll_wait
785 If there are any outstanding requests and none of them in the result
786 phase, wait till the result filehandle becomes ready for reading
787 (simply does a "select" on the filehandle. This is useful if you
788 want to synchronously wait for some requests to finish).
789
790 See "nreqs" for an example.
791
792 IO::AIO::poll
793 Waits until some requests have been handled.
794
795 Returns the number of requests processed, but is otherwise strictly
796 equivalent to:
797
798 IO::AIO::poll_wait, IO::AIO::poll_cb
799
800 IO::AIO::flush
801 Wait till all outstanding AIO requests have been handled.
802
803 Strictly equivalent to:
804
805 IO::AIO::poll_wait, IO::AIO::poll_cb
806 while IO::AIO::nreqs;
807
808 CONTROLLING THE NUMBER OF THREADS 1488 CONTROLLING THE NUMBER OF THREADS
809 IO::AIO::min_parallel $nthreads 1489 IO::AIO::min_parallel $nthreads
810 Set the minimum number of AIO threads to $nthreads. The current 1490 Set the minimum number of AIO threads to $nthreads. The current
811 default is 8, which means eight asynchronous operations can execute 1491 default is 8, which means eight asynchronous operations can execute
812 concurrently at any one time (the number of outstanding requests, 1492 concurrently at any one time (the number of outstanding requests,
… …
841 1521
842 Under normal circumstances you don't need to call this function. 1522 Under normal circumstances you don't need to call this function.
843 1523
844 IO::AIO::max_idle $nthreads 1524 IO::AIO::max_idle $nthreads
845 Limit the number of threads (default: 4) that are allowed to idle 1525 Limit the number of threads (default: 4) that are allowed to idle
846 (i.e., threads that did not get a request to process within 10 1526 (i.e., threads that did not get a request to process within the idle
847 seconds). That means if a thread becomes idle while $nthreads other 1527 timeout (default: 10 seconds). That means if a thread becomes idle
848 threads are also idle, it will free its resources and exit. 1528 while $nthreads other threads are also idle, it will free its
1529 resources and exit.
849 1530
850 This is useful when you allow a large number of threads (e.g. 100 or 1531 This is useful when you allow a large number of threads (e.g. 100 or
851 1000) to allow for extremely high load situations, but want to free 1532 1000) to allow for extremely high load situations, but want to free
852 resources under normal circumstances (1000 threads can easily 1533 resources under normal circumstances (1000 threads can easily
853 consume 30MB of RAM). 1534 consume 30MB of RAM).
854 1535
855 The default is probably ok in most situations, especially if thread 1536 The default is probably ok in most situations, especially if thread
856 creation is fast. If thread creation is very slow on your system you 1537 creation is fast. If thread creation is very slow on your system you
857 might want to use larger values. 1538 might want to use larger values.
858 1539
1540 IO::AIO::idle_timeout $seconds
1541 Sets the minimum idle timeout (default 10) after which worker
1542 threads are allowed to exit. SEe "IO::AIO::max_idle".
1543
859 $oldmaxreqs = IO::AIO::max_outstanding $maxreqs 1544 IO::AIO::max_outstanding $maxreqs
1545 Sets the maximum number of outstanding requests to $nreqs. If you do
1546 queue up more than this number of requests, the next call to
1547 "IO::AIO::poll_cb" (and other functions calling "poll_cb", such as
1548 "IO::AIO::flush" or "IO::AIO::poll") will block until the limit is
1549 no longer exceeded.
1550
1551 In other words, this setting does not enforce a queue limit, but can
1552 be used to make poll functions block if the limit is exceeded.
1553
860 This is a very bad function to use in interactive programs because 1554 This is a very bad function to use in interactive programs because
861 it blocks, and a bad way to reduce concurrency because it is 1555 it blocks, and a bad way to reduce concurrency because it is
862 inexact: Better use an "aio_group" together with a feed callback. 1556 inexact: Better use an "aio_group" together with a feed callback.
863 1557
864 Sets the maximum number of outstanding requests to $nreqs. If you do 1558 Its main use is in scripts without an event loop - when you want to
865 queue up more than this number of requests, the next call to the 1559 stat a lot of files, you can write something like this:
866 "poll_cb" (and "poll_some" and other functions calling "poll_cb")
867 function will block until the limit is no longer exceeded.
868 1560
869 The default value is very large, so there is no practical limit on 1561 IO::AIO::max_outstanding 32;
1562
1563 for my $path (...) {
1564 aio_stat $path , ...;
1565 IO::AIO::poll_cb;
1566 }
1567
1568 IO::AIO::flush;
1569
1570 The call to "poll_cb" inside the loop will normally return
1571 instantly, but as soon as more thna 32 reqeusts are in-flight, it
1572 will block until some requests have been handled. This keeps the
1573 loop from pushing a large number of "aio_stat" requests onto the
1574 queue.
1575
1576 The default value for "max_outstanding" is very large, so there is
870 the number of outstanding requests. 1577 no practical limit on the number of outstanding requests.
871
872 You can still queue as many requests as you want. Therefore,
873 "max_oustsanding" is mainly useful in simple scripts (with low
874 values) or as a stop gap to shield against fatal memory overflow
875 (with large values).
876 1578
877 STATISTICAL INFORMATION 1579 STATISTICAL INFORMATION
878 IO::AIO::nreqs 1580 IO::AIO::nreqs
879 Returns the number of requests currently in the ready, execute or 1581 Returns the number of requests currently in the ready, execute or
880 pending states (i.e. for which their callback has not been invoked 1582 pending states (i.e. for which their callback has not been invoked
… …
891 1593
892 IO::AIO::npending 1594 IO::AIO::npending
893 Returns the number of requests currently in the pending state 1595 Returns the number of requests currently in the pending state
894 (executed, but not yet processed by poll_cb). 1596 (executed, but not yet processed by poll_cb).
895 1597
1598 SUBSECOND STAT TIME ACCESS
1599 Both "aio_stat"/"aio_lstat" and perl's "stat"/"lstat" functions can
1600 generally find access/modification and change times with subsecond time
1601 accuracy of the system supports it, but perl's built-in functions only
1602 return the integer part.
1603
1604 The following functions return the timestamps of the most recent stat
1605 with subsecond precision on most systems and work both after
1606 "aio_stat"/"aio_lstat" and perl's "stat"/"lstat" calls. Their return
1607 value is only meaningful after a successful "stat"/"lstat" call, or
1608 during/after a successful "aio_stat"/"aio_lstat" callback.
1609
1610 This is similar to the Time::HiRes "stat" functions, but can return full
1611 resolution without rounding and work with standard perl "stat",
1612 alleviating the need to call the special "Time::HiRes" functions, which
1613 do not act like their perl counterparts.
1614
1615 On operating systems or file systems where subsecond time resolution is
1616 not supported or could not be detected, a fractional part of 0 is
1617 returned, so it is always safe to call these functions.
1618
1619 $seconds = IO::AIO::st_atime, IO::AIO::st_mtime, IO::AIO::st_ctime
1620 Return the access, modication or change time, respectively,
1621 including fractional part. Due to the limited precision of floating
1622 point, the accuracy on most platforms is only a bit better than
1623 milliseconds for times around now - see the *nsec* function family,
1624 below, for full accuracy.
1625
1626 ($atime, $mtime, $ctime, ...) = IO::AIO::st_xtime
1627 Returns access, modification and change time all in one go, and
1628 maybe more times in the future version.
1629
1630 $nanoseconds = IO::AIO::st_atimensec, IO::AIO::st_mtimensec,
1631 IO::AIO::st_ctimensec
1632 Return the fractional access, modifcation or change time, in
1633 nanoseconds, as an integer in the range 0 to 999999999.
1634
1635 ($atime, $mtime, $ctime, ...) = IO::AIO::st_xtimensec
1636 Like the functions above, but returns all three times in one go (and
1637 maybe more in future versions).
1638
1639 Example: print the high resolution modification time of /etc, using
1640 "stat", and "IO::AIO::aio_stat".
1641
1642 if (stat "/etc") {
1643 printf "stat(/etc) mtime: %f\n", IO::AIO::st_mtime;
1644 }
1645
1646 IO::AIO::aio_stat "/etc", sub {
1647 $_[0]
1648 and return;
1649
1650 printf "aio_stat(/etc) mtime: %d.%09d\n", (stat _)[9], IO::AIO::st_mtimensec;
1651 };
1652
1653 IO::AIO::flush;
1654
1655 Output of the awbove on my system, showing reduced and full accuracy:
1656
1657 stat(/etc) mtime: 1534043702.020808
1658 aio_stat(/etc) mtime: 1534043702.020807792
1659
1660 MISCELLANEOUS FUNCTIONS
1661 IO::AIO implements some functions that are useful when you want to use
1662 some "Advanced I/O" function not available to in Perl, without going the
1663 "Asynchronous I/O" route. Many of these have an asynchronous "aio_*"
1664 counterpart.
1665
1666 $numfd = IO::AIO::get_fdlimit
1667 This function is *EXPERIMENTAL* and subject to change.
1668
1669 Tries to find the current file descriptor limit and returns it, or
1670 "undef" and sets $! in case of an error. The limit is one larger
1671 than the highest valid file descriptor number.
1672
1673 IO::AIO::min_fdlimit [$numfd]
1674 This function is *EXPERIMENTAL* and subject to change.
1675
1676 Try to increase the current file descriptor limit(s) to at least
1677 $numfd by changing the soft or hard file descriptor resource limit.
1678 If $numfd is missing, it will try to set a very high limit, although
1679 this is not recommended when you know the actual minimum that you
1680 require.
1681
1682 If the limit cannot be raised enough, the function makes a
1683 best-effort attempt to increase the limit as much as possible, using
1684 various tricks, while still failing. You can query the resulting
1685 limit using "IO::AIO::get_fdlimit".
1686
1687 If an error occurs, returns "undef" and sets $!, otherwise returns
1688 true.
1689
1690 IO::AIO::sendfile $ofh, $ifh, $offset, $count
1691 Calls the "eio_sendfile_sync" function, which is like
1692 "aio_sendfile", but is blocking (this makes most sense if you know
1693 the input data is likely cached already and the output filehandle is
1694 set to non-blocking operations).
1695
1696 Returns the number of bytes copied, or -1 on error.
1697
1698 IO::AIO::fadvise $fh, $offset, $len, $advice
1699 Simply calls the "posix_fadvise" function (see its manpage for
1700 details). The following advice constants are available:
1701 "IO::AIO::FADV_NORMAL", "IO::AIO::FADV_SEQUENTIAL",
1702 "IO::AIO::FADV_RANDOM", "IO::AIO::FADV_NOREUSE",
1703 "IO::AIO::FADV_WILLNEED", "IO::AIO::FADV_DONTNEED".
1704
1705 On systems that do not implement "posix_fadvise", this function
1706 returns ENOSYS, otherwise the return value of "posix_fadvise".
1707
1708 IO::AIO::madvise $scalar, $offset, $len, $advice
1709 Simply calls the "posix_madvise" function (see its manpage for
1710 details). The following advice constants are available:
1711 "IO::AIO::MADV_NORMAL", "IO::AIO::MADV_SEQUENTIAL",
1712 "IO::AIO::MADV_RANDOM", "IO::AIO::MADV_WILLNEED",
1713 "IO::AIO::MADV_DONTNEED".
1714
1715 If $offset is negative, counts from the end. If $length is negative,
1716 the remaining length of the $scalar is used. If possible, $length
1717 will be reduced to fit into the $scalar.
1718
1719 On systems that do not implement "posix_madvise", this function
1720 returns ENOSYS, otherwise the return value of "posix_madvise".
1721
1722 IO::AIO::mprotect $scalar, $offset, $len, $protect
1723 Simply calls the "mprotect" function on the preferably AIO::mmap'ed
1724 $scalar (see its manpage for details). The following protect
1725 constants are available: "IO::AIO::PROT_NONE", "IO::AIO::PROT_READ",
1726 "IO::AIO::PROT_WRITE", "IO::AIO::PROT_EXEC".
1727
1728 If $offset is negative, counts from the end. If $length is negative,
1729 the remaining length of the $scalar is used. If possible, $length
1730 will be reduced to fit into the $scalar.
1731
1732 On systems that do not implement "mprotect", this function returns
1733 ENOSYS, otherwise the return value of "mprotect".
1734
1735 IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
1736 Memory-maps a file (or anonymous memory range) and attaches it to
1737 the given $scalar, which will act like a string scalar. Returns true
1738 on success, and false otherwise.
1739
1740 The scalar must exist, but its contents do not matter - this means
1741 you cannot use a nonexistant array or hash element. When in doubt,
1742 "undef" the scalar first.
1743
1744 The only operations allowed on the mmapped scalar are
1745 "substr"/"vec", which don't change the string length, and most
1746 read-only operations such as copying it or searching it with regexes
1747 and so on.
1748
1749 Anything else is unsafe and will, at best, result in memory leaks.
1750
1751 The memory map associated with the $scalar is automatically removed
1752 when the $scalar is undef'd or destroyed, or when the
1753 "IO::AIO::mmap" or "IO::AIO::munmap" functions are called on it.
1754
1755 This calls the "mmap"(2) function internally. See your system's
1756 manual page for details on the $length, $prot and $flags parameters.
1757
1758 The $length must be larger than zero and smaller than the actual
1759 filesize.
1760
1761 $prot is a combination of "IO::AIO::PROT_NONE",
1762 "IO::AIO::PROT_EXEC", "IO::AIO::PROT_READ" and/or
1763 "IO::AIO::PROT_WRITE",
1764
1765 $flags can be a combination of "IO::AIO::MAP_SHARED" or
1766 "IO::AIO::MAP_PRIVATE", or a number of system-specific flags (when
1767 not available, the are 0): "IO::AIO::MAP_ANONYMOUS" (which is set to
1768 "MAP_ANON" if your system only provides this constant),
1769 "IO::AIO::MAP_LOCKED", "IO::AIO::MAP_NORESERVE",
1770 "IO::AIO::MAP_POPULATE", "IO::AIO::MAP_NONBLOCK",
1771 "IO::AIO::MAP_FIXED", "IO::AIO::MAP_GROWSDOWN",
1772 "IO::AIO::MAP_32BIT", "IO::AIO::MAP_HUGETLB" or
1773 "IO::AIO::MAP_STACK".
1774
1775 If $fh is "undef", then a file descriptor of -1 is passed.
1776
1777 $offset is the offset from the start of the file - it generally must
1778 be a multiple of "IO::AIO::PAGESIZE" and defaults to 0.
1779
1780 Example:
1781
1782 use Digest::MD5;
1783 use IO::AIO;
1784
1785 open my $fh, "<verybigfile"
1786 or die "$!";
1787
1788 IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
1789 or die "verybigfile: $!";
1790
1791 my $fast_md5 = md5 $data;
1792
1793 IO::AIO::munmap $scalar
1794 Removes a previous mmap and undefines the $scalar.
1795
1796 IO::AIO::mremap $scalar, $new_length, $flags = MREMAP_MAYMOVE[,
1797 $new_address = 0]
1798 Calls the Linux-specific mremap(2) system call. The $scalar must
1799 have been mapped by "IO::AIO::mmap", and $flags must currently
1800 either be 0 or "IO::AIO::MREMAP_MAYMOVE".
1801
1802 Returns true if successful, and false otherwise. If the underlying
1803 mmapped region has changed address, then the true value has the
1804 numerical value 1, otherwise it has the numerical value 0:
1805
1806 my $success = IO::AIO::mremap $mmapped, 8192, IO::AIO::MREMAP_MAYMOVE
1807 or die "mremap: $!";
1808
1809 if ($success*1) {
1810 warn "scalar has chanegd address in memory\n";
1811 }
1812
1813 "IO::AIO::MREMAP_FIXED" and the $new_address argument are currently
1814 implemented, but not supported and might go away in a future
1815 version.
1816
1817 On systems where this call is not supported or is not emulated, this
1818 call returns falls and sets $! to "ENOSYS".
1819
1820 IO::AIO::munlock $scalar, $offset = 0, $length = undef
1821 Calls the "munlock" function, undoing the effects of a previous
1822 "aio_mlock" call (see its description for details).
1823
1824 IO::AIO::munlockall
1825 Calls the "munlockall" function.
1826
1827 On systems that do not implement "munlockall", this function returns
1828 ENOSYS, otherwise the return value of "munlockall".
1829
1830 IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
1831 Calls the GNU/Linux splice(2) syscall, if available. If $r_off or
1832 $w_off are "undef", then "NULL" is passed for these, otherwise they
1833 should be the file offset.
1834
1835 $r_fh and $w_fh should not refer to the same file, as splice might
1836 silently corrupt the data in this case.
1837
1838 The following symbol flag values are available:
1839 "IO::AIO::SPLICE_F_MOVE", "IO::AIO::SPLICE_F_NONBLOCK",
1840 "IO::AIO::SPLICE_F_MORE" and "IO::AIO::SPLICE_F_GIFT".
1841
1842 See the splice(2) manpage for details.
1843
1844 IO::AIO::tee $r_fh, $w_fh, $length, $flags
1845 Calls the GNU/Linux tee(2) syscall, see its manpage and the
1846 description for "IO::AIO::splice" above for details.
1847
1848 $actual_size = IO::AIO::pipesize $r_fh[, $new_size]
1849 Attempts to query or change the pipe buffer size. Obviously works
1850 only on pipes, and currently works only on GNU/Linux systems, and
1851 fails with -1/"ENOSYS" everywhere else. If anybody knows how to
1852 influence pipe buffer size on other systems, drop me a note.
1853
1854 ($rfh, $wfh) = IO::AIO::pipe2 [$flags]
1855 This is a direct interface to the Linux pipe2(2) system call. If
1856 $flags is missing or 0, then this should be the same as a call to
1857 perl's built-in "pipe" function and create a new pipe, and works on
1858 systems that lack the pipe2 syscall. On win32, this case invokes
1859 "_pipe (..., 4096, O_BINARY)".
1860
1861 If $flags is non-zero, it tries to invoke the pipe2 system call with
1862 the given flags (Linux 2.6.27, glibc 2.9).
1863
1864 On success, the read and write file handles are returned.
1865
1866 On error, nothing will be returned. If the pipe2 syscall is missing
1867 and $flags is non-zero, fails with "ENOSYS".
1868
1869 Please refer to pipe2(2) for more info on the $flags, but at the
1870 time of this writing, "IO::AIO::O_CLOEXEC", "IO::AIO::O_NONBLOCK"
1871 and "IO::AIO::O_DIRECT" (Linux 3.4, for packet-based pipes) were
1872 supported.
1873
1874 Example: create a pipe race-free w.r.t. threads and fork:
1875
1876 my ($rfh, $wfh) = IO::AIO::pipe2 IO::AIO::O_CLOEXEC
1877 or die "pipe2: $!\n";
1878
1879 $fh = IO::AIO::eventfd [$initval, [$flags]]
1880 This is a direct interface to the Linux eventfd(2) system call. The
1881 (unhelpful) defaults for $initval and $flags are 0 for both.
1882
1883 On success, the new eventfd filehandle is returned, otherwise
1884 returns "undef". If the eventfd syscall is missing, fails with
1885 "ENOSYS".
1886
1887 Please refer to eventfd(2) for more info on this call.
1888
1889 The following symbol flag values are available:
1890 "IO::AIO::EFD_CLOEXEC", "IO::AIO::EFD_NONBLOCK" and
1891 "IO::AIO::EFD_SEMAPHORE" (Linux 2.6.30).
1892
1893 Example: create a new eventfd filehandle:
1894
1895 $fh = IO::AIO::eventfd 0, IO::AIO::O_CLOEXEC
1896 or die "eventfd: $!\n";
1897
1898 $fh = IO::AIO::timerfd_create $clockid[, $flags]
1899 This is a direct interface to the Linux timerfd_create(2) system
1900 call. The (unhelpful) default for $flags is 0.
1901
1902 On success, the new timerfd filehandle is returned, otherwise
1903 returns "undef". If the eventfd syscall is missing, fails with
1904 "ENOSYS".
1905
1906 Please refer to timerfd_create(2) for more info on this call.
1907
1908 The following $clockid values are available:
1909 "IO::AIO::CLOCK_REALTIME", "IO::AIO::CLOCK_MONOTONIC"
1910 "IO::AIO::CLOCK_CLOCK_BOOTTIME" (Linux 3.15)
1911 "IO::AIO::CLOCK_CLOCK_REALTIME_ALARM" (Linux 3.11) and
1912 "IO::AIO::CLOCK_CLOCK_BOOTTIME_ALARM" (Linux 3.11).
1913
1914 The following $flags values are available (Linux 2.6.27):
1915 "IO::AIO::TFD_NONBLOCK" and "IO::AIO::TFD_CLOEXEC".
1916
1917 Example: create a new timerfd and set it to one-second repeated
1918 alarms, then wait for two alarms:
1919
1920 my $fh = IO::AIO::timerfd_create IO::AIO::CLOCK_BOOTTIME, IO::AIO::TFD_CLOEXEC
1921 or die "timerfd_create: $!\n";
1922
1923 defined IO::AIO::timerfd_settime $fh, 0, 1, 1
1924 or die "timerfd_settime: $!\n";
1925
1926 for (1..2) {
1927 8 == sysread $fh, my $buf, 8
1928 or die "timerfd read failure\n";
1929
1930 printf "number of expirations (likely 1): %d\n",
1931 unpack "Q", $buf;
1932 }
1933
1934 ($cur_interval, $cur_value) = IO::AIO::timerfd_settime $fh, $flags,
1935 $new_interval, $nbw_value
1936 This is a direct interface to the Linux timerfd_settime(2) system
1937 call. Please refer to its manpage for more info on this call.
1938
1939 The new itimerspec is specified using two (possibly fractional)
1940 second values, $new_interval and $new_value).
1941
1942 On success, the current interval and value are returned (as per
1943 "timerfd_gettime"). On failure, the empty list is returned.
1944
1945 The following $flags values are available:
1946 "IO::AIO::TFD_TIMER_ABSTIME" and "IO::AIO::TFD_TIMER_CANCEL_ON_SET".
1947
1948 See "IO::AIO::timerfd_create" for a full example.
1949
1950 ($cur_interval, $cur_value) = IO::AIO::timerfd_gettime $fh
1951 This is a direct interface to the Linux timerfd_gettime(2) system
1952 call. Please refer to its manpage for more info on this call.
1953
1954 On success, returns the current values of interval and value for the
1955 given timerfd (as potentially fractional second values). On failure,
1956 the empty list is returned.
1957
1958EVENT LOOP INTEGRATION
1959 It is recommended to use AnyEvent::AIO to integrate IO::AIO
1960 automatically into many event loops:
1961
1962 # AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
1963 use AnyEvent::AIO;
1964
1965 You can also integrate IO::AIO manually into many event loops, here are
1966 some examples of how to do this:
1967
1968 # EV integration
1969 my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
1970
1971 # Event integration
1972 Event->io (fd => IO::AIO::poll_fileno,
1973 poll => 'r',
1974 cb => \&IO::AIO::poll_cb);
1975
1976 # Glib/Gtk2 integration
1977 add_watch Glib::IO IO::AIO::poll_fileno,
1978 in => sub { IO::AIO::poll_cb; 1 };
1979
1980 # Tk integration
1981 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
1982 readable => \&IO::AIO::poll_cb);
1983
1984 # Danga::Socket integration
1985 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
1986 \&IO::AIO::poll_cb);
1987
896 FORK BEHAVIOUR 1988 FORK BEHAVIOUR
897 This module should do "the right thing" when the process using it forks: 1989 Usage of pthreads in a program changes the semantics of fork
1990 considerably. Specifically, only async-safe functions can be called
1991 after fork. Perl doesn't know about this, so in general, you cannot call
1992 fork with defined behaviour in perl if pthreads are involved. IO::AIO
1993 uses pthreads, so this applies, but many other extensions and (for
1994 inexplicable reasons) perl itself often is linked against pthreads, so
1995 this limitation applies to quite a lot of perls.
898 1996
899 Before the fork, IO::AIO enters a quiescent state where no requests can 1997 This module no longer tries to fight your OS, or POSIX. That means
900 be added in other threads and no results will be processed. After the 1998 IO::AIO only works in the process that loaded it. Forking is fully
901 fork the parent simply leaves the quiescent state and continues 1999 supported, but using IO::AIO in the child is not.
902 request/result processing, while the child frees the request/result
903 queue (so that the requests started before the fork will only be handled
904 in the parent). Threads will be started on demand until the limit set in
905 the parent process has been reached again.
906 2000
907 In short: the parent will, after a short pause, continue as if fork had 2001 You might get around by not *using* IO::AIO before (or after) forking.
908 not been called, while the child will act as if IO::AIO has not been 2002 You could also try to call the IO::AIO::reinit function in the child:
909 used yet. 2003
2004 IO::AIO::reinit
2005 Abandons all current requests and I/O threads and simply
2006 reinitialises all data structures. This is not an operation
2007 supported by any standards, but happens to work on GNU/Linux and
2008 some newer BSD systems.
2009
2010 The only reasonable use for this function is to call it after
2011 forking, if "IO::AIO" was used in the parent. Calling it while
2012 IO::AIO is active in the process will result in undefined behaviour.
2013 Calling it at any time will also result in any undefined (by POSIX)
2014 behaviour.
2015
2016 LINUX-SPECIFIC CALLS
2017 When a call is documented as "linux-specific" then this means it
2018 originated on GNU/Linux. "IO::AIO" will usually try to autodetect the
2019 availability and compatibility of such calls regardless of the platform
2020 it is compiled on, so platforms such as FreeBSD which often implement
2021 these calls will work. When in doubt, call them and see if they fail wth
2022 "ENOSYS".
910 2023
911 MEMORY USAGE 2024 MEMORY USAGE
912 Per-request usage: 2025 Per-request usage:
913 2026
914 Each aio request uses - depending on your architecture - around 100-200 2027 Each aio request uses - depending on your architecture - around 100-200
… …
925 In the execution phase, some aio requests require more memory for 2038 In the execution phase, some aio requests require more memory for
926 temporary buffers, and each thread requires a stack and other data 2039 temporary buffers, and each thread requires a stack and other data
927 structures (usually around 16k-128k, depending on the OS). 2040 structures (usually around 16k-128k, depending on the OS).
928 2041
929KNOWN BUGS 2042KNOWN BUGS
930 Known bugs will be fixed in the next release. 2043 Known bugs will be fixed in the next release :)
2044
2045KNOWN ISSUES
2046 Calls that try to "import" foreign memory areas (such as "IO::AIO::mmap"
2047 or "IO::AIO::aio_slurp") do not work with generic lvalues, such as
2048 non-created hash slots or other scalars I didn't think of. It's best to
2049 avoid such and either use scalar variables or making sure that the
2050 scalar exists (e.g. by storing "undef") and isn't "funny" (e.g. tied).
2051
2052 I am not sure anything can be done about this, so this is considered a
2053 known issue, rather than a bug.
931 2054
932SEE ALSO 2055SEE ALSO
933 Coro::AIO. 2056 AnyEvent::AIO for easy integration into event loops, Coro::AIO for a
2057 more natural syntax.
934 2058
935AUTHOR 2059AUTHOR
936 Marc Lehmann <schmorp@schmorp.de> 2060 Marc Lehmann <schmorp@schmorp.de>
937 http://home.schmorp.de/ 2061 http://home.schmorp.de/
938 2062

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