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2 IO::AIO - Asynchronous Input/Output 2 IO::AIO - Asynchronous Input/Output
3 3
4SYNOPSIS 4SYNOPSIS
5 use IO::AIO; 5 use IO::AIO;
6 6
7 aio_open "/etc/passwd", O_RDONLY, 0, sub { 7 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
8 my ($fh) = @_; 8 my $fh = shift
9 or die "/etc/passwd: $!";
9 ... 10 ...
10 }; 11 };
11 12
12 aio_unlink "/tmp/file", sub { }; 13 aio_unlink "/tmp/file", sub { };
13 14
14 aio_read $fh, 30000, 1024, $buffer, 0, sub { 15 aio_read $fh, 30000, 1024, $buffer, 0, sub {
15 $_[0] > 0 or die "read error: $!"; 16 $_[0] > 0 or die "read error: $!";
16 }; 17 };
17 18
18 # AnyEvent 19 # version 2+ has request and group objects
19 open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!"; 20 use IO::AIO 2;
20 my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
21 21
22 # Event 22 aioreq_pri 4; # give next request a very high priority
23 Event->io (fd => IO::AIO::poll_fileno, 23 my $req = aio_unlink "/tmp/file", sub { };
24 poll => 'r', 24 $req->cancel; # cancel request if still in queue
25 cb => \&IO::AIO::poll_cb);
26 25
27 # Glib/Gtk2 26 my $grp = aio_group sub { print "all stats done\n" };
28 add_watch Glib::IO IO::AIO::poll_fileno, 27 add $grp aio_stat "..." for ...;
29 in => sub { IO::AIO::poll_cb; 1 };
30
31 # Tk
32 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
33 readable => \&IO::AIO::poll_cb);
34
35 # Danga::Socket
36 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
37 \&IO::AIO::poll_cb);
38 28
39DESCRIPTION 29DESCRIPTION
40 This module implements asynchronous I/O using whatever means your 30 This module implements asynchronous I/O using whatever means your
41 operating system supports. 31 operating system supports. It is implemented as an interface to "libeio"
32 (<http://software.schmorp.de/pkg/libeio.html>).
42 33
34 Asynchronous means that operations that can normally block your program
35 (e.g. reading from disk) will be done asynchronously: the operation will
36 still block, but you can do something else in the meantime. This is
37 extremely useful for programs that need to stay interactive even when
38 doing heavy I/O (GUI programs, high performance network servers etc.),
39 but can also be used to easily do operations in parallel that are
40 normally done sequentially, e.g. stat'ing many files, which is much
41 faster on a RAID volume or over NFS when you do a number of stat
42 operations concurrently.
43
44 While most of this works on all types of file descriptors (for example
45 sockets), using these functions on file descriptors that support
46 nonblocking operation (again, sockets, pipes etc.) is very inefficient.
47 Use an event loop for that (such as the EV module): IO::AIO will
48 naturally fit into such an event loop itself.
49
43 Currently, a number of threads are started that execute your read/writes 50 In this version, a number of threads are started that execute your
44 and signal their completion. You don't need thread support in your libc 51 requests and signal their completion. You don't need thread support in
45 or 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
46 the pthreads library. In the future, this module might make use of the 53 perl. In the future, this module might make use of the native aio
47 native aio functions available on many operating systems. However, they 54 functions available on many operating systems. However, they are often
48 are often not well-supported (Linux doesn't allow them on normal files 55 not well-supported or restricted (GNU/Linux doesn't allow them on normal
49 currently, for example), and they would only support aio_read and 56 files currently, for example), and they would only support aio_read and
50 aio_write, so the remaining functionality would have to be implemented 57 aio_write, so the remaining functionality would have to be implemented
51 using threads anyway. 58 using threads anyway.
52 59
53 Although the module will work with in the presence of other threads, it 60 Although the module will work in the presence of other (Perl-) threads,
54 is currently not reentrant, so use appropriate locking yourself, always 61 it is currently not reentrant in any way, so use appropriate locking
55 call "poll_cb" from within the same thread, or never call "poll_cb" (or 62 yourself, always call "poll_cb" from within the same thread, or never
56 other "aio_" functions) recursively. 63 call "poll_cb" (or other "aio_" functions) recursively.
64
65 EXAMPLE
66 This is a simple example that uses the EV module and loads /etc/passwd
67 asynchronously:
68
69 use Fcntl;
70 use EV;
71 use IO::AIO;
72
73 # register the IO::AIO callback with EV
74 my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
75
76 # queue the request to open /etc/passwd
77 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
78 my $fh = shift
79 or die "error while opening: $!";
80
81 # stat'ing filehandles is generally non-blocking
82 my $size = -s $fh;
83
84 # queue a request to read the file
85 my $contents;
86 aio_read $fh, 0, $size, $contents, 0, sub {
87 $_[0] == $size
88 or die "short read: $!";
89
90 close $fh;
91
92 # file contents now in $contents
93 print $contents;
94
95 # exit event loop and program
96 EV::unloop;
97 };
98 };
99
100 # possibly queue up other requests, or open GUI windows,
101 # check for sockets etc. etc.
102
103 # process events as long as there are some:
104 EV::loop;
105
106REQUEST ANATOMY AND LIFETIME
107 Every "aio_*" function creates a request. which is a C data structure
108 not directly visible to Perl.
109
110 If called in non-void context, every request function returns a Perl
111 object representing the request. In void context, nothing is returned,
112 which saves a bit of memory.
113
114 The perl object is a fairly standard ref-to-hash object. The hash
115 contents are not used by IO::AIO so you are free to store anything you
116 like in it.
117
118 During their existance, aio requests travel through the following
119 states, in order:
120
121 ready
122 Immediately after a request is created it is put into the ready
123 state, waiting for a thread to execute it.
124
125 execute
126 A thread has accepted the request for processing and is currently
127 executing it (e.g. blocking in read).
128
129 pending
130 The request has been executed and is waiting for result processing.
131
132 While request submission and execution is fully asynchronous, result
133 processing is not and relies on the perl interpreter calling
134 "poll_cb" (or another function with the same effect).
135
136 result
137 The request results are processed synchronously by "poll_cb".
138
139 The "poll_cb" function will process all outstanding aio requests by
140 calling their callbacks, freeing memory associated with them and
141 managing any groups they are contained in.
142
143 done
144 Request has reached the end of its lifetime and holds no resources
145 anymore (except possibly for the Perl object, but its connection to
146 the actual aio request is severed and calling its methods will
147 either do nothing or result in a runtime error).
57 148
58FUNCTIONS 149FUNCTIONS
150 QUICK OVERVIEW
151 This section simply lists the prototypes of the most important functions
152 for quick reference. See the following sections for function-by-function
153 documentation.
154
155 aio_wd $pathname, $callback->($wd)
156 aio_open $pathname, $flags, $mode, $callback->($fh)
157 aio_close $fh, $callback->($status)
158 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
159 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
160 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
161 aio_readahead $fh,$offset,$length, $callback->($retval)
162 aio_stat $fh_or_path, $callback->($status)
163 aio_lstat $fh, $callback->($status)
164 aio_statvfs $fh_or_path, $callback->($statvfs)
165 aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
166 aio_chown $fh_or_path, $uid, $gid, $callback->($status)
167 aio_truncate $fh_or_path, $offset, $callback->($status)
168 aio_chmod $fh_or_path, $mode, $callback->($status)
169 aio_unlink $pathname, $callback->($status)
170 aio_mknod $pathname, $mode, $dev, $callback->($status)
171 aio_link $srcpath, $dstpath, $callback->($status)
172 aio_symlink $srcpath, $dstpath, $callback->($status)
173 aio_readlink $pathname, $callback->($link)
174 aio_realpath $pathname, $callback->($link)
175 aio_rename $srcpath, $dstpath, $callback->($status)
176 aio_mkdir $pathname, $mode, $callback->($status)
177 aio_rmdir $pathname, $callback->($status)
178 aio_readdir $pathname, $callback->($entries)
179 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
180 IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
181 IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
182 aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
183 aio_load $pathname, $data, $callback->($status)
184 aio_copy $srcpath, $dstpath, $callback->($status)
185 aio_move $srcpath, $dstpath, $callback->($status)
186 aio_rmtree $pathname, $callback->($status)
187 aio_sync $callback->($status)
188 aio_syncfs $fh, $callback->($status)
189 aio_fsync $fh, $callback->($status)
190 aio_fdatasync $fh, $callback->($status)
191 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
192 aio_pathsync $pathname, $callback->($status)
193 aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
194 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
195 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
196 aio_mlockall $flags, $callback->($status)
197 aio_group $callback->(...)
198 aio_nop $callback->()
199
200 $prev_pri = aioreq_pri [$pri]
201 aioreq_nice $pri_adjust
202
203 IO::AIO::poll_wait
204 IO::AIO::poll_cb
205 IO::AIO::poll
206 IO::AIO::flush
207 IO::AIO::max_poll_reqs $nreqs
208 IO::AIO::max_poll_time $seconds
209 IO::AIO::min_parallel $nthreads
210 IO::AIO::max_parallel $nthreads
211 IO::AIO::max_idle $nthreads
212 IO::AIO::idle_timeout $seconds
213 IO::AIO::max_outstanding $maxreqs
214 IO::AIO::nreqs
215 IO::AIO::nready
216 IO::AIO::npending
217
218 IO::AIO::sendfile $ofh, $ifh, $offset, $count
219 IO::AIO::fadvise $fh, $offset, $len, $advice
220 IO::AIO::madvise $scalar, $offset, $length, $advice
221 IO::AIO::mprotect $scalar, $offset, $length, $protect
222 IO::AIO::munlock $scalar, $offset = 0, $length = undef
223 IO::AIO::munlockall
224
59 AIO FUNCTIONS 225 AIO REQUEST FUNCTIONS
60 All the "aio_*" calls are more or less thin wrappers around the syscall 226 All the "aio_*" calls are more or less thin wrappers around the syscall
61 with the same name (sans "aio_"). The arguments are similar or 227 with the same name (sans "aio_"). The arguments are similar or
62 identical, and they all accept an additional (and optional) $callback 228 identical, and they all accept an additional (and optional) $callback
63 argument which must be a code reference. This code reference will get 229 argument which must be a code reference. This code reference will be
64 called with the syscall return code (e.g. most syscalls return -1 on 230 called after the syscall has been executed in an asynchronous fashion.
65 error, unlike perl, which usually delivers "false") as it's sole 231 The results of the request will be passed as arguments to the callback
66 argument when the given syscall has been executed asynchronously. 232 (and, if an error occured, in $!) - for most requests the syscall return
233 code (e.g. most syscalls return -1 on error, unlike perl, which usually
234 delivers "false").
235
236 Some requests (such as "aio_readdir") pass the actual results and
237 communicate failures by passing "undef".
67 238
68 All functions expecting a filehandle keep a copy of the filehandle 239 All functions expecting a filehandle keep a copy of the filehandle
69 internally until the request has finished. 240 internally until the request has finished.
70 241
242 All functions return request objects of type IO::AIO::REQ that allow
243 further manipulation of those requests while they are in-flight.
244
71 The pathnames you pass to these routines *must* be absolute and encoded 245 The pathnames you pass to these routines *should* be absolute. The
72 in byte form. The reason for the former is that at the time the request 246 reason for this is that at the time the request is being executed, the
73 is being executed, the current working directory could have changed. 247 current working directory could have changed. Alternatively, you can
74 Alternatively, you can make sure that you never change the current 248 make sure that you never change the current working directory anywhere
75 working directory. 249 in the program and then use relative paths. You can also take advantage
250 of IO::AIOs working directory abstraction, that lets you specify paths
251 relative to some previously-opened "working directory object" - see the
252 description of the "IO::AIO::WD" class later in this document.
76 253
77 To encode pathnames to byte form, either make sure you either: a) always 254 To encode pathnames as octets, either make sure you either: a) always
78 pass in filenames you got from outside (command line, readdir etc.), b) 255 pass in filenames you got from outside (command line, readdir etc.)
79 are ASCII or ISO 8859-1, c) use the Encode module and encode your 256 without tinkering, b) are in your native filesystem encoding, c) use the
80 pathnames to the locale (or other) encoding in effect in the user 257 Encode module and encode your pathnames to the locale (or other)
81 environment, d) use Glib::filename_from_unicode on unicode filenames or 258 encoding in effect in the user environment, d) use
82 e) use something else. 259 Glib::filename_from_unicode on unicode filenames or e) use something
260 else to ensure your scalar has the correct contents.
261
262 This works, btw. independent of the internal UTF-8 bit, which IO::AIO
263 handles correctly whether it is set or not.
264
265 $prev_pri = aioreq_pri [$pri]
266 Returns the priority value that would be used for the next request
267 and, if $pri is given, sets the priority for the next aio request.
268
269 The default priority is 0, the minimum and maximum priorities are -4
270 and 4, respectively. Requests with higher priority will be serviced
271 first.
272
273 The priority will be reset to 0 after each call to one of the
274 "aio_*" functions.
275
276 Example: open a file with low priority, then read something from it
277 with higher priority so the read request is serviced before other
278 low priority open requests (potentially spamming the cache):
279
280 aioreq_pri -3;
281 aio_open ..., sub {
282 return unless $_[0];
283
284 aioreq_pri -2;
285 aio_read $_[0], ..., sub {
286 ...
287 };
288 };
289
290 aioreq_nice $pri_adjust
291 Similar to "aioreq_pri", but subtracts the given value from the
292 current priority, so the effect is cumulative.
83 293
84 aio_open $pathname, $flags, $mode, $callback->($fh) 294 aio_open $pathname, $flags, $mode, $callback->($fh)
85 Asynchronously open or create a file and call the callback with a 295 Asynchronously open or create a file and call the callback with a
86 newly created filehandle for the file. 296 newly created filehandle for the file.
87 297
… …
92 They are the same as used by "sysopen". 302 They are the same as used by "sysopen".
93 303
94 Likewise, $mode specifies the mode of the newly created file, if it 304 Likewise, $mode specifies the mode of the newly created file, if it
95 didn't exist and "O_CREAT" has been given, just like perl's 305 didn't exist and "O_CREAT" has been given, just like perl's
96 "sysopen", except that it is mandatory (i.e. use 0 if you don't 306 "sysopen", except that it is mandatory (i.e. use 0 if you don't
97 create new files, and 0666 or 0777 if you do). 307 create new files, and 0666 or 0777 if you do). Note that the $mode
308 will be modified by the umask in effect then the request is being
309 executed, so better never change the umask.
98 310
99 Example: 311 Example:
100 312
101 aio_open "/etc/passwd", O_RDONLY, 0, sub { 313 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
102 if ($_[0]) { 314 if ($_[0]) {
103 print "open successful, fh is $_[0]\n"; 315 print "open successful, fh is $_[0]\n";
104 ... 316 ...
105 } else { 317 } else {
106 die "open failed: $!\n"; 318 die "open failed: $!\n";
107 } 319 }
108 }; 320 };
109 321
322 In addition to all the common open modes/flags ("O_RDONLY",
323 "O_WRONLY", "O_RDWR", "O_CREAT", "O_TRUNC", "O_EXCL" and
324 "O_APPEND"), the following POSIX and non-POSIX constants are
325 available (missing ones on your system are, as usual, 0):
326
327 "O_ASYNC", "O_DIRECT", "O_NOATIME", "O_CLOEXEC", "O_NOCTTY",
328 "O_NOFOLLOW", "O_NONBLOCK", "O_EXEC", "O_SEARCH", "O_DIRECTORY",
329 "O_DSYNC", "O_RSYNC", "O_SYNC" and "O_TTY_INIT".
330
110 aio_close $fh, $callback->($status) 331 aio_close $fh, $callback->($status)
111 Asynchronously close a file and call the callback with the result 332 Asynchronously close a file and call the callback with the result
112 code. *WARNING:* although accepted, you should not pass in a perl 333 code.
113 filehandle here, as perl will likely close the file descriptor
114 another time when the filehandle is destroyed. Normally, you can
115 safely call perls "close" or just let filehandles go out of scope.
116 334
117 This is supposed to be a bug in the API, so that might change. It's 335 Unfortunately, you can't do this to perl. Perl *insists* very
118 therefore best to avoid this function. 336 strongly on closing the file descriptor associated with the
337 filehandle itself.
338
339 Therefore, "aio_close" will not close the filehandle - instead it
340 will use dup2 to overwrite the file descriptor with the write-end of
341 a pipe (the pipe fd will be created on demand and will be cached).
342
343 Or in other words: the file descriptor will be closed, but it will
344 not be free for reuse until the perl filehandle is closed.
119 345
120 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval) 346 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
121 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval) 347 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
122 Reads or writes "length" bytes from the specified "fh" and "offset" 348 Reads or writes $length bytes from or to the specified $fh and
123 into the scalar given by "data" and offset "dataoffset" and calls 349 $offset into the scalar given by $data and offset $dataoffset and
124 the callback without the actual number of bytes read (or -1 on 350 calls the callback without the actual number of bytes read (or -1 on
125 error, just like the syscall). 351 error, just like the syscall).
126 352
353 "aio_read" will, like "sysread", shrink or grow the $data scalar to
354 offset plus the actual number of bytes read.
355
356 If $offset is undefined, then the current file descriptor offset
357 will be used (and updated), otherwise the file descriptor offset
358 will not be changed by these calls.
359
360 If $length is undefined in "aio_write", use the remaining length of
361 $data.
362
363 If $dataoffset is less than zero, it will be counted from the end of
364 $data.
365
127 The $data scalar *MUST NOT* be modified in any way while the request 366 The $data scalar *MUST NOT* be modified in any way while the request
128 is outstanding. Modifying it can result in segfaults or WW3 (if the 367 is outstanding. Modifying it can result in segfaults or World War
129 necessary/optional hardware is installed). 368 III (if the necessary/optional hardware is installed).
130 369
131 Example: Read 15 bytes at offset 7 into scalar $buffer, starting at 370 Example: Read 15 bytes at offset 7 into scalar $buffer, starting at
132 offset 0 within the scalar: 371 offset 0 within the scalar:
133 372
134 aio_read $fh, 7, 15, $buffer, 0, sub { 373 aio_read $fh, 7, 15, $buffer, 0, sub {
135 $_[0] > 0 or die "read error: $!"; 374 $_[0] > 0 or die "read error: $!";
136 print "read $_[0] bytes: <$buffer>\n"; 375 print "read $_[0] bytes: <$buffer>\n";
137 }; 376 };
138
139 aio_move $srcpath, $dstpath, $callback->($status)
140 [EXPERIMENTAL]
141
142 Try to move the *file* (directories not supported as either source
143 or destination) from $srcpath to $dstpath and call the callback with
144 the 0 (error) or -1 ok.
145
146 This is a composite request that tries to rename(2) the file first.
147 If rename files with "EXDEV", it creates the destination file with
148 mode 0200 and copies the contents of the source file into it using
149 "aio_sendfile", followed by restoring atime, mtime, access mode and
150 uid/gid, in that order, and unlinking the $srcpath.
151
152 If an error occurs, the partial destination file will be unlinked,
153 if possible, except when setting atime, mtime, access mode and
154 uid/gid, where errors are being ignored.
155 377
156 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval) 378 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
157 Tries to copy $length bytes from $in_fh to $out_fh. It starts 379 Tries to copy $length bytes from $in_fh to $out_fh. It starts
158 reading at byte offset $in_offset, and starts writing at the current 380 reading at byte offset $in_offset, and starts writing at the current
159 file offset of $out_fh. Because of that, it is not safe to issue 381 file offset of $out_fh. Because of that, it is not safe to issue
160 more than one "aio_sendfile" per $out_fh, as they will interfere 382 more than one "aio_sendfile" per $out_fh, as they will interfere
161 with each other. 383 with each other. The same $in_fh works fine though, as this function
384 does not move or use the file offset of $in_fh.
162 385
386 Please note that "aio_sendfile" can read more bytes from $in_fh than
387 are written, and there is no way to find out how many more bytes
388 have been read from "aio_sendfile" alone, as "aio_sendfile" only
389 provides the number of bytes written to $out_fh. Only if the result
390 value equals $length one can assume that $length bytes have been
391 read.
392
393 Unlike with other "aio_" functions, it makes a lot of sense to use
394 "aio_sendfile" on non-blocking sockets, as long as one end
395 (typically the $in_fh) is a file - the file I/O will then be
396 asynchronous, while the socket I/O will be non-blocking. Note,
397 however, that you can run into a trap where "aio_sendfile" reads
398 some data with readahead, then fails to write all data, and when the
399 socket is ready the next time, the data in the cache is already
400 lost, forcing "aio_sendfile" to again hit the disk. Explicit
401 "aio_read" + "aio_write" let's you better control resource usage.
402
163 This call tries to make use of a native "sendfile" syscall to 403 This call tries to make use of a native "sendfile"-like syscall to
164 provide zero-copy operation. For this to work, $out_fh should refer 404 provide zero-copy operation. For this to work, $out_fh should refer
165 to a socket, and $in_fh should refer to mmap'able file. 405 to a socket, and $in_fh should refer to an mmap'able file.
166 406
167 If the native sendfile call fails or is not implemented, it will be 407 If a native sendfile cannot be found or it fails with "ENOSYS",
168 emulated, so you can call "aio_sendfile" on any type of filehandle 408 "EINVAL", "ENOTSUP", "EOPNOTSUPP", "EAFNOSUPPORT", "EPROTOTYPE" or
169 regardless of the limitations of the operating system. 409 "ENOTSOCK", it will be emulated, so you can call "aio_sendfile" on
410 any type of filehandle regardless of the limitations of the
411 operating system.
170 412
171 Please note, however, that "aio_sendfile" can read more bytes from 413 As native sendfile syscalls (as practically any non-POSIX interface
172 $in_fh than are written, and there is no way to find out how many 414 hacked together in a hurry to improve benchmark numbers) tend to be
173 bytes have been read from "aio_sendfile" alone, as "aio_sendfile" 415 rather buggy on many systems, this implementation tries to work
174 only provides the number of bytes written to $out_fh. Only if the 416 around some known bugs in Linux and FreeBSD kernels (probably
175 result value equals $length one can assume that $length bytes have 417 others, too), but that might fail, so you really really should check
176 been read. 418 the return value of "aio_sendfile" - fewre bytes than expected might
419 have been transferred.
177 420
178 aio_readahead $fh,$offset,$length, $callback->($retval) 421 aio_readahead $fh,$offset,$length, $callback->($retval)
179 "aio_readahead" populates the page cache with data from a file so 422 "aio_readahead" populates the page cache with data from a file so
180 that subsequent reads from that file will not block on disk I/O. The 423 that subsequent reads from that file will not block on disk I/O. The
181 $offset argument specifies the starting point from which data is to 424 $offset argument specifies the starting point from which data is to
… …
202 Currently, the stats are always 64-bit-stats, i.e. instead of 445 Currently, the stats are always 64-bit-stats, i.e. instead of
203 returning an error when stat'ing a large file, the results will be 446 returning an error when stat'ing a large file, the results will be
204 silently truncated unless perl itself is compiled with large file 447 silently truncated unless perl itself is compiled with large file
205 support. 448 support.
206 449
450 To help interpret the mode and dev/rdev stat values, IO::AIO offers
451 the following constants and functions (if not implemented, the
452 constants will be 0 and the functions will either "croak" or fall
453 back on traditional behaviour).
454
455 "S_IFMT", "S_IFIFO", "S_IFCHR", "S_IFBLK", "S_IFLNK", "S_IFREG",
456 "S_IFDIR", "S_IFWHT", "S_IFSOCK", "IO::AIO::major $dev_t",
457 "IO::AIO::minor $dev_t", "IO::AIO::makedev $major, $minor".
458
207 Example: Print the length of /etc/passwd: 459 Example: Print the length of /etc/passwd:
208 460
209 aio_stat "/etc/passwd", sub { 461 aio_stat "/etc/passwd", sub {
210 $_[0] and die "stat failed: $!"; 462 $_[0] and die "stat failed: $!";
211 print "size is ", -s _, "\n"; 463 print "size is ", -s _, "\n";
212 }; 464 };
213 465
466 aio_statvfs $fh_or_path, $callback->($statvfs)
467 Works like the POSIX "statvfs" or "fstatvfs" syscalls, depending on
468 whether a file handle or path was passed.
469
470 On success, the callback is passed a hash reference with the
471 following members: "bsize", "frsize", "blocks", "bfree", "bavail",
472 "files", "ffree", "favail", "fsid", "flag" and "namemax". On
473 failure, "undef" is passed.
474
475 The following POSIX IO::AIO::ST_* constants are defined: "ST_RDONLY"
476 and "ST_NOSUID".
477
478 The following non-POSIX IO::AIO::ST_* flag masks are defined to
479 their correct value when available, or to 0 on systems that do not
480 support them: "ST_NODEV", "ST_NOEXEC", "ST_SYNCHRONOUS",
481 "ST_MANDLOCK", "ST_WRITE", "ST_APPEND", "ST_IMMUTABLE",
482 "ST_NOATIME", "ST_NODIRATIME" and "ST_RELATIME".
483
484 Example: stat "/wd" and dump out the data if successful.
485
486 aio_statvfs "/wd", sub {
487 my $f = $_[0]
488 or die "statvfs: $!";
489
490 use Data::Dumper;
491 say Dumper $f;
492 };
493
494 # result:
495 {
496 bsize => 1024,
497 bfree => 4333064312,
498 blocks => 10253828096,
499 files => 2050765568,
500 flag => 4096,
501 favail => 2042092649,
502 bavail => 4333064312,
503 ffree => 2042092649,
504 namemax => 255,
505 frsize => 1024,
506 fsid => 1810
507 }
508
509 aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
510 Works like perl's "utime" function (including the special case of
511 $atime and $mtime being undef). Fractional times are supported if
512 the underlying syscalls support them.
513
514 When called with a pathname, uses utimes(2) if available, otherwise
515 utime(2). If called on a file descriptor, uses futimes(2) if
516 available, otherwise returns ENOSYS, so this is not portable.
517
518 Examples:
519
520 # set atime and mtime to current time (basically touch(1)):
521 aio_utime "path", undef, undef;
522 # set atime to current time and mtime to beginning of the epoch:
523 aio_utime "path", time, undef; # undef==0
524
525 aio_chown $fh_or_path, $uid, $gid, $callback->($status)
526 Works like perl's "chown" function, except that "undef" for either
527 $uid or $gid is being interpreted as "do not change" (but -1 can
528 also be used).
529
530 Examples:
531
532 # same as "chown root path" in the shell:
533 aio_chown "path", 0, -1;
534 # same as above:
535 aio_chown "path", 0, undef;
536
537 aio_truncate $fh_or_path, $offset, $callback->($status)
538 Works like truncate(2) or ftruncate(2).
539
540 aio_chmod $fh_or_path, $mode, $callback->($status)
541 Works like perl's "chmod" function.
542
214 aio_unlink $pathname, $callback->($status) 543 aio_unlink $pathname, $callback->($status)
215 Asynchronously unlink (delete) a file and call the callback with the 544 Asynchronously unlink (delete) a file and call the callback with the
216 result code. 545 result code.
546
547 aio_mknod $pathname, $mode, $dev, $callback->($status)
548 [EXPERIMENTAL]
549
550 Asynchronously create a device node (or fifo). See mknod(2).
551
552 The only (POSIX-) portable way of calling this function is:
553
554 aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
555
556 See "aio_stat" for info about some potentially helpful extra
557 constants and functions.
217 558
218 aio_link $srcpath, $dstpath, $callback->($status) 559 aio_link $srcpath, $dstpath, $callback->($status)
219 Asynchronously create a new link to the existing object at $srcpath 560 Asynchronously create a new link to the existing object at $srcpath
220 at the path $dstpath and call the callback with the result code. 561 at the path $dstpath and call the callback with the result code.
221 562
222 aio_symlink $srcpath, $dstpath, $callback->($status) 563 aio_symlink $srcpath, $dstpath, $callback->($status)
223 Asynchronously create a new symbolic link to the existing object at 564 Asynchronously create a new symbolic link to the existing object at
224 $srcpath at the path $dstpath and call the callback with the result 565 $srcpath at the path $dstpath and call the callback with the result
225 code. 566 code.
226 567
568 aio_readlink $pathname, $callback->($link)
569 Asynchronously read the symlink specified by $path and pass it to
570 the callback. If an error occurs, nothing or undef gets passed to
571 the callback.
572
573 aio_realpath $pathname, $callback->($path)
574 Asynchronously make the path absolute and resolve any symlinks in
575 $path. The resulting path only consists of directories (Same as
576 Cwd::realpath).
577
578 This request can be used to get the absolute path of the current
579 working directory by passing it a path of . (a single dot).
580
227 aio_rename $srcpath, $dstpath, $callback->($status) 581 aio_rename $srcpath, $dstpath, $callback->($status)
228 Asynchronously rename the object at $srcpath to $dstpath, just as 582 Asynchronously rename the object at $srcpath to $dstpath, just as
229 rename(2) and call the callback with the result code. 583 rename(2) and call the callback with the result code.
584
585 aio_mkdir $pathname, $mode, $callback->($status)
586 Asynchronously mkdir (create) a directory and call the callback with
587 the result code. $mode will be modified by the umask at the time the
588 request is executed, so do not change your umask.
230 589
231 aio_rmdir $pathname, $callback->($status) 590 aio_rmdir $pathname, $callback->($status)
232 Asynchronously rmdir (delete) a directory and call the callback with 591 Asynchronously rmdir (delete) a directory and call the callback with
233 the result code. 592 the result code.
234 593
235 aio_readdir $pathname, $callback->($entries) 594 aio_readdir $pathname, $callback->($entries)
236 Unlike the POSIX call of the same name, "aio_readdir" reads an 595 Unlike the POSIX call of the same name, "aio_readdir" reads an
237 entire directory (i.e. opendir + readdir + closedir). The entries 596 entire directory (i.e. opendir + readdir + closedir). The entries
238 will not be sorted, and will NOT include the "." and ".." entries. 597 will not be sorted, and will NOT include the "." and ".." entries.
239 598
240 The callback a single argument which is either "undef" or an 599 The callback is passed a single argument which is either "undef" or
241 array-ref with the filenames. 600 an array-ref with the filenames.
242 601
602 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
603 Quite similar to "aio_readdir", but the $flags argument allows one
604 to tune behaviour and output format. In case of an error, $entries
605 will be "undef".
606
607 The flags are a combination of the following constants, ORed
608 together (the flags will also be passed to the callback, possibly
609 modified):
610
611 IO::AIO::READDIR_DENTS
612 When this flag is off, then the callback gets an arrayref
613 consisting of names only (as with "aio_readdir"), otherwise it
614 gets an arrayref with "[$name, $type, $inode]" arrayrefs, each
615 describing a single directory entry in more detail.
616
617 $name is the name of the entry.
618
619 $type is one of the "IO::AIO::DT_xxx" constants:
620
621 "IO::AIO::DT_UNKNOWN", "IO::AIO::DT_FIFO", "IO::AIO::DT_CHR",
622 "IO::AIO::DT_DIR", "IO::AIO::DT_BLK", "IO::AIO::DT_REG",
623 "IO::AIO::DT_LNK", "IO::AIO::DT_SOCK", "IO::AIO::DT_WHT".
624
625 "IO::AIO::DT_UNKNOWN" means just that: readdir does not know. If
626 you need to know, you have to run stat yourself. Also, for speed
627 reasons, the $type scalars are read-only: you can not modify
628 them.
629
630 $inode is the inode number (which might not be exact on systems
631 with 64 bit inode numbers and 32 bit perls). This field has
632 unspecified content on systems that do not deliver the inode
633 information.
634
635 IO::AIO::READDIR_DIRS_FIRST
636 When this flag is set, then the names will be returned in an
637 order where likely directories come first, in optimal stat
638 order. This is useful when you need to quickly find directories,
639 or you want to find all directories while avoiding to stat()
640 each entry.
641
642 If the system returns type information in readdir, then this is
643 used to find directories directly. Otherwise, likely directories
644 are names beginning with ".", or otherwise names with no dots,
645 of which names with short names are tried first.
646
647 IO::AIO::READDIR_STAT_ORDER
648 When this flag is set, then the names will be returned in an
649 order suitable for stat()'ing each one. That is, when you plan
650 to stat() all files in the given directory, then the returned
651 order will likely be fastest.
652
653 If both this flag and "IO::AIO::READDIR_DIRS_FIRST" are
654 specified, then the likely dirs come first, resulting in a less
655 optimal stat order.
656
657 IO::AIO::READDIR_FOUND_UNKNOWN
658 This flag should not be set when calling "aio_readdirx".
659 Instead, it is being set by "aio_readdirx", when any of the
660 $type's found were "IO::AIO::DT_UNKNOWN". The absence of this
661 flag therefore indicates that all $type's are known, which can
662 be used to speed up some algorithms.
663
664 aio_load $pathname, $data, $callback->($status)
665 This is a composite request that tries to fully load the given file
666 into memory. Status is the same as with aio_read.
667
668 aio_copy $srcpath, $dstpath, $callback->($status)
669 Try to copy the *file* (directories not supported as either source
670 or destination) from $srcpath to $dstpath and call the callback with
671 a status of 0 (ok) or -1 (error, see $!).
672
673 This is a composite request that creates the destination file with
674 mode 0200 and copies the contents of the source file into it using
675 "aio_sendfile", followed by restoring atime, mtime, access mode and
676 uid/gid, in that order.
677
678 If an error occurs, the partial destination file will be unlinked,
679 if possible, except when setting atime, mtime, access mode and
680 uid/gid, where errors are being ignored.
681
682 aio_move $srcpath, $dstpath, $callback->($status)
683 Try to move the *file* (directories not supported as either source
684 or destination) from $srcpath to $dstpath and call the callback with
685 a status of 0 (ok) or -1 (error, see $!).
686
687 This is a composite request that tries to rename(2) the file first;
688 if rename fails with "EXDEV", it copies the file with "aio_copy"
689 and, if that is successful, unlinks the $srcpath.
690
243 aio_scandir $path, $maxreq, $callback->($dirs, $nondirs) 691 aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
244 Scans a directory (similar to "aio_readdir") and tries to separate 692 Scans a directory (similar to "aio_readdir") but additionally tries
245 the entries of directory $path into two sets of names, ones you can 693 to efficiently separate the entries of directory $path into two sets
246 recurse into (directories), and ones you cannot recurse into 694 of names, directories you can recurse into (directories), and ones
247 (everything else). 695 you cannot recurse into (everything else, including symlinks to
696 directories).
248 697
249 "aio_scandir" is a composite request that consists of many 698 "aio_scandir" is a composite request that creates of many sub
250 aio-primitives. $maxreq specifies the maximum number of outstanding 699 requests_ $maxreq specifies the maximum number of outstanding aio
251 aio requests that this function generates. If it is "<= 0", then a 700 requests that this function generates. If it is "<= 0", then a
252 suitable default will be chosen (currently 8). 701 suitable default will be chosen (currently 4).
253 702
254 On error, the callback is called without arguments, otherwise it 703 On error, the callback is called without arguments, otherwise it
255 receives two array-refs with path-relative entry names. 704 receives two array-refs with path-relative entry names.
256 705
257 Example: 706 Example:
… …
265 Implementation notes. 714 Implementation notes.
266 715
267 The "aio_readdir" cannot be avoided, but "stat()"'ing every entry 716 The "aio_readdir" cannot be avoided, but "stat()"'ing every entry
268 can. 717 can.
269 718
719 If readdir returns file type information, then this is used directly
720 to find directories.
721
270 After reading the directory, the modification time, size etc. of the 722 Otherwise, after reading the directory, the modification time, size
271 directory before and after the readdir is checked, and if they 723 etc. of the directory before and after the readdir is checked, and
272 match, the link count will be used to decide how many entries are 724 if they match (and isn't the current time), the link count will be
273 directories (if >= 2). Otherwise, no knowledge of the number of 725 used to decide how many entries are directories (if >= 2).
274 subdirectories will be assumed. 726 Otherwise, no knowledge of the number of subdirectories will be
727 assumed.
275 728
276 Then entires will be sorted into likely directories (everything 729 Then entries will be sorted into likely directories a non-initial
277 without a non-initial dot) and likely non-directories (everything 730 dot currently) and likely non-directories (see "aio_readdirx"). Then
278 else). Then every entry + "/." will be "stat"'ed, likely directories 731 every entry plus an appended "/." will be "stat"'ed, likely
279 first. This is often faster because filesystems might detect the 732 directories first, in order of their inode numbers. If that
733 succeeds, it assumes that the entry is a directory or a symlink to
734 directory (which will be checked separately). This is often faster
735 than stat'ing the entry itself because filesystems might detect the
280 type of the entry without reading the inode data (e.g. ext2fs 736 type of the entry without reading the inode data (e.g. ext2fs
281 filetype feature). If that succeeds, it assumes that the entry is a 737 filetype feature), even on systems that cannot return the filetype
282 directory or a symlink to directory (which will be checked 738 information on readdir.
283 seperately).
284 739
285 If the known number of directories has been reached, the rest of the 740 If the known number of directories (link count - 2) has been
286 entries is assumed to be non-directories. 741 reached, the rest of the entries is assumed to be non-directories.
742
743 This only works with certainty on POSIX (= UNIX) filesystems, which
744 fortunately are the vast majority of filesystems around.
745
746 It will also likely work on non-POSIX filesystems with reduced
747 efficiency as those tend to return 0 or 1 as link counts, which
748 disables the directory counting heuristic.
749
750 aio_rmtree $pathname, $callback->($status)
751 Delete a directory tree starting (and including) $path, return the
752 status of the final "rmdir" only. This is a composite request that
753 uses "aio_scandir" to recurse into and rmdir directories, and unlink
754 everything else.
755
756 aio_sync $callback->($status)
757 Asynchronously call sync and call the callback when finished.
287 758
288 aio_fsync $fh, $callback->($status) 759 aio_fsync $fh, $callback->($status)
289 Asynchronously call fsync on the given filehandle and call the 760 Asynchronously call fsync on the given filehandle and call the
290 callback with the fsync result code. 761 callback with the fsync result code.
291 762
… …
294 callback with the fdatasync result code. 765 callback with the fdatasync result code.
295 766
296 If this call isn't available because your OS lacks it or it couldn't 767 If this call isn't available because your OS lacks it or it couldn't
297 be detected, it will be emulated by calling "fsync" instead. 768 be detected, it will be emulated by calling "fsync" instead.
298 769
770 aio_syncfs $fh, $callback->($status)
771 Asynchronously call the syncfs syscall to sync the filesystem
772 associated to the given filehandle and call the callback with the
773 syncfs result code. If syncfs is not available, calls sync(), but
774 returns -1 and sets errno to "ENOSYS" nevertheless.
775
776 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
777 Sync the data portion of the file specified by $offset and $length
778 to disk (but NOT the metadata), by calling the Linux-specific
779 sync_file_range call. If sync_file_range is not available or it
780 returns ENOSYS, then fdatasync or fsync is being substituted.
781
782 $flags can be a combination of
783 "IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE",
784 "IO::AIO::SYNC_FILE_RANGE_WRITE" and
785 "IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER": refer to the sync_file_range
786 manpage for details.
787
788 aio_pathsync $pathname, $callback->($status)
789 This request tries to open, fsync and close the given path. This is
790 a composite request intended to sync directories after directory
791 operations (E.g. rename). This might not work on all operating
792 systems or have any specific effect, but usually it makes sure that
793 directory changes get written to disc. It works for anything that
794 can be opened for read-only, not just directories.
795
796 Future versions of this function might fall back to other methods
797 when "fsync" on the directory fails (such as calling "sync").
798
799 Passes 0 when everything went ok, and -1 on error.
800
801 aio_msync $scalar, $offset = 0, $length = undef, flags = 0,
802 $callback->($status)
803 This is a rather advanced IO::AIO call, which only works on
804 mmap(2)ed scalars (see the "IO::AIO::mmap" function, although it
805 also works on data scalars managed by the Sys::Mmap or Mmap modules,
806 note that the scalar must only be modified in-place while an aio
807 operation is pending on it).
808
809 It calls the "msync" function of your OS, if available, with the
810 memory area starting at $offset in the string and ending $length
811 bytes later. If $length is negative, counts from the end, and if
812 $length is "undef", then it goes till the end of the string. The
813 flags can be a combination of "IO::AIO::MS_ASYNC",
814 "IO::AIO::MS_INVALIDATE" and "IO::AIO::MS_SYNC".
815
816 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0,
817 $callback->($status)
818 This is a rather advanced IO::AIO call, which works best on
819 mmap(2)ed scalars.
820
821 It touches (reads or writes) all memory pages in the specified range
822 inside the scalar. All caveats and parameters are the same as for
823 "aio_msync", above, except for flags, which must be either 0 (which
824 reads all pages and ensures they are instantiated) or
825 "IO::AIO::MT_MODIFY", which modifies the memory page s(by reading
826 and writing an octet from it, which dirties the page).
827
828 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
829 This is a rather advanced IO::AIO call, which works best on
830 mmap(2)ed scalars.
831
832 It reads in all the pages of the underlying storage into memory (if
833 any) and locks them, so they are not getting swapped/paged out or
834 removed.
835
836 If $length is undefined, then the scalar will be locked till the
837 end.
838
839 On systems that do not implement "mlock", this function returns -1
840 and sets errno to "ENOSYS".
841
842 Note that the corresponding "munlock" is synchronous and is
843 documented under "MISCELLANEOUS FUNCTIONS".
844
845 Example: open a file, mmap and mlock it - both will be undone when
846 $data gets destroyed.
847
848 open my $fh, "<", $path or die "$path: $!";
849 my $data;
850 IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
851 aio_mlock $data; # mlock in background
852
853 aio_mlockall $flags, $callback->($status)
854 Calls the "mlockall" function with the given $flags (a combination
855 of "IO::AIO::MCL_CURRENT" and "IO::AIO::MCL_FUTURE").
856
857 On systems that do not implement "mlockall", this function returns
858 -1 and sets errno to "ENOSYS".
859
860 Note that the corresponding "munlockall" is synchronous and is
861 documented under "MISCELLANEOUS FUNCTIONS".
862
863 Example: asynchronously lock all current and future pages into
864 memory.
865
866 aio_mlockall IO::AIO::MCL_FUTURE;
867
868 aio_group $callback->(...)
869 This is a very special aio request: Instead of doing something, it
870 is a container for other aio requests, which is useful if you want
871 to bundle many requests into a single, composite, request with a
872 definite callback and the ability to cancel the whole request with
873 its subrequests.
874
875 Returns an object of class IO::AIO::GRP. See its documentation below
876 for more info.
877
878 Example:
879
880 my $grp = aio_group sub {
881 print "all stats done\n";
882 };
883
884 add $grp
885 (aio_stat ...),
886 (aio_stat ...),
887 ...;
888
889 aio_nop $callback->()
890 This is a special request - it does nothing in itself and is only
891 used for side effects, such as when you want to add a dummy request
892 to a group so that finishing the requests in the group depends on
893 executing the given code.
894
895 While this request does nothing, it still goes through the execution
896 phase and still requires a worker thread. Thus, the callback will
897 not be executed immediately but only after other requests in the
898 queue have entered their execution phase. This can be used to
899 measure request latency.
900
901 IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
902 Mainly used for debugging and benchmarking, this aio request puts
903 one of the request workers to sleep for the given time.
904
905 While it is theoretically handy to have simple I/O scheduling
906 requests like sleep and file handle readable/writable, the overhead
907 this creates is immense (it blocks a thread for a long time) so do
908 not use this function except to put your application under
909 artificial I/O pressure.
910
911 IO::AIO::WD - multiple working directories
912 Your process only has one current working directory, which is used by
913 all threads. This makes it hard to use relative paths (some other
914 component could call "chdir" at any time, and it is hard to control when
915 the path will be used by IO::AIO).
916
917 One solution for this is to always use absolute paths. This usually
918 works, but can be quite slow (the kernel has to walk the whole path on
919 every access), and can also be a hassle to implement.
920
921 Newer POSIX systems have a number of functions (openat, fdopendir,
922 futimensat and so on) that make it possible to specify working
923 directories per operation.
924
925 For portability, and because the clowns who "designed", or shall I
926 write, perpetrated this new interface were obviously half-drunk, this
927 abstraction cannot be perfect, though.
928
929 IO::AIO allows you to convert directory paths into a so-called
930 IO::AIO::WD object. This object stores the canonicalised, absolute
931 version of the path, and on systems that allow it, also a directory file
932 descriptor.
933
934 Everywhere where a pathname is accepted by IO::AIO (e.g. in "aio_stat"
935 or "aio_unlink"), one can specify an array reference with an IO::AIO::WD
936 object and a pathname instead (or the IO::AIO::WD object alone, which
937 gets interpreted as "[$wd, "."]"). If the pathname is absolute, the
938 IO::AIO::WD object is ignored, otherwise the pathname is resolved
939 relative to that IO::AIO::WD object.
940
941 For example, to get a wd object for /etc and then stat passwd inside,
942 you would write:
943
944 aio_wd "/etc", sub {
945 my $etcdir = shift;
946
947 # although $etcdir can be undef on error, there is generally no reason
948 # to check for errors here, as aio_stat will fail with ENOENT
949 # when $etcdir is undef.
950
951 aio_stat [$etcdir, "passwd"], sub {
952 # yay
953 };
954 };
955
956 That "aio_wd" is a request and not a normal function shows that creating
957 an IO::AIO::WD object is itself a potentially blocking operation, which
958 is why it is done asynchronously.
959
960 To stat the directory obtained with "aio_wd" above, one could write
961 either of the following three request calls:
962
963 aio_lstat "/etc" , sub { ... # pathname as normal string
964 aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
965 aio_lstat $wd , sub { ... # shorthand for the previous
966
967 As with normal pathnames, IO::AIO keeps a copy of the working directory
968 object and the pathname string, so you could write the following without
969 causing any issues due to $path getting reused:
970
971 my $path = [$wd, undef];
972
973 for my $name (qw(abc def ghi)) {
974 $path->[1] = $name;
975 aio_stat $path, sub {
976 # ...
977 };
978 }
979
980 There are some caveats: when directories get renamed (or deleted), the
981 pathname string doesn't change, so will point to the new directory (or
982 nowhere at all), while the directory fd, if available on the system,
983 will still point to the original directory. Most functions accepting a
984 pathname will use the directory fd on newer systems, and the string on
985 older systems. Some functions (such as realpath) will always rely on the
986 string form of the pathname.
987
988 So this fucntionality is mainly useful to get some protection against
989 "chdir", to easily get an absolute path out of a relative path for
990 future reference, and to speed up doing many operations in the same
991 directory (e.g. when stat'ing all files in a directory).
992
993 The following functions implement this working directory abstraction:
994
995 aio_wd $pathname, $callback->($wd)
996 Asynchonously canonicalise the given pathname and convert it to an
997 IO::AIO::WD object representing it. If possible and supported on the
998 system, also open a directory fd to speed up pathname resolution
999 relative to this working directory.
1000
1001 If something goes wrong, then "undef" is passwd to the callback
1002 instead of a working directory object and $! is set appropriately.
1003 Since passing "undef" as working directory component of a pathname
1004 fails the request with "ENOENT", there is often no need for error
1005 checking in the "aio_wd" callback, as future requests using the
1006 value will fail in the expected way.
1007
1008 If this call isn't available because your OS lacks it or it couldn't
1009 be detected, it will be emulated by calling "fsync" instead.
1010
1011 IO::AIO::CWD
1012 This is a compiletime constant (object) that represents the process
1013 current working directory.
1014
1015 Specifying this object as working directory object for a pathname is
1016 as if the pathname would be specified directly, without a directory
1017 object, e.g., these calls are functionally identical:
1018
1019 aio_stat "somefile", sub { ... };
1020 aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
1021
1022 IO::AIO::REQ CLASS
1023 All non-aggregate "aio_*" functions return an object of this class when
1024 called in non-void context.
1025
1026 cancel $req
1027 Cancels the request, if possible. Has the effect of skipping
1028 execution when entering the execute state and skipping calling the
1029 callback when entering the the result state, but will leave the
1030 request otherwise untouched (with the exception of readdir). That
1031 means that requests that currently execute will not be stopped and
1032 resources held by the request will not be freed prematurely.
1033
1034 cb $req $callback->(...)
1035 Replace (or simply set) the callback registered to the request.
1036
1037 IO::AIO::GRP CLASS
1038 This class is a subclass of IO::AIO::REQ, so all its methods apply to
1039 objects of this class, too.
1040
1041 A IO::AIO::GRP object is a special request that can contain multiple
1042 other aio requests.
1043
1044 You create one by calling the "aio_group" constructing function with a
1045 callback that will be called when all contained requests have entered
1046 the "done" state:
1047
1048 my $grp = aio_group sub {
1049 print "all requests are done\n";
1050 };
1051
1052 You add requests by calling the "add" method with one or more
1053 "IO::AIO::REQ" objects:
1054
1055 $grp->add (aio_unlink "...");
1056
1057 add $grp aio_stat "...", sub {
1058 $_[0] or return $grp->result ("error");
1059
1060 # add another request dynamically, if first succeeded
1061 add $grp aio_open "...", sub {
1062 $grp->result ("ok");
1063 };
1064 };
1065
1066 This makes it very easy to create composite requests (see the source of
1067 "aio_move" for an application) that work and feel like simple requests.
1068
1069 * The IO::AIO::GRP objects will be cleaned up during calls to
1070 "IO::AIO::poll_cb", just like any other request.
1071
1072 * They can be canceled like any other request. Canceling will cancel
1073 not only the request itself, but also all requests it contains.
1074
1075 * They can also can also be added to other IO::AIO::GRP objects.
1076
1077 * You must not add requests to a group from within the group callback
1078 (or any later time).
1079
1080 Their lifetime, simplified, looks like this: when they are empty, they
1081 will finish very quickly. If they contain only requests that are in the
1082 "done" state, they will also finish. Otherwise they will continue to
1083 exist.
1084
1085 That means after creating a group you have some time to add requests
1086 (precisely before the callback has been invoked, which is only done
1087 within the "poll_cb"). And in the callbacks of those requests, you can
1088 add further requests to the group. And only when all those requests have
1089 finished will the the group itself finish.
1090
1091 add $grp ...
1092 $grp->add (...)
1093 Add one or more requests to the group. Any type of IO::AIO::REQ can
1094 be added, including other groups, as long as you do not create
1095 circular dependencies.
1096
1097 Returns all its arguments.
1098
1099 $grp->cancel_subs
1100 Cancel all subrequests and clears any feeder, but not the group
1101 request itself. Useful when you queued a lot of events but got a
1102 result early.
1103
1104 The group request will finish normally (you cannot add requests to
1105 the group).
1106
1107 $grp->result (...)
1108 Set the result value(s) that will be passed to the group callback
1109 when all subrequests have finished and set the groups errno to the
1110 current value of errno (just like calling "errno" without an error
1111 number). By default, no argument will be passed and errno is zero.
1112
1113 $grp->errno ([$errno])
1114 Sets the group errno value to $errno, or the current value of errno
1115 when the argument is missing.
1116
1117 Every aio request has an associated errno value that is restored
1118 when the callback is invoked. This method lets you change this value
1119 from its default (0).
1120
1121 Calling "result" will also set errno, so make sure you either set $!
1122 before the call to "result", or call c<errno> after it.
1123
1124 feed $grp $callback->($grp)
1125 Sets a feeder/generator on this group: every group can have an
1126 attached generator that generates requests if idle. The idea behind
1127 this is that, although you could just queue as many requests as you
1128 want in a group, this might starve other requests for a potentially
1129 long time. For example, "aio_scandir" might generate hundreds of
1130 thousands of "aio_stat" requests, delaying any later requests for a
1131 long time.
1132
1133 To avoid this, and allow incremental generation of requests, you can
1134 instead a group and set a feeder on it that generates those
1135 requests. The feed callback will be called whenever there are few
1136 enough (see "limit", below) requests active in the group itself and
1137 is expected to queue more requests.
1138
1139 The feed callback can queue as many requests as it likes (i.e. "add"
1140 does not impose any limits).
1141
1142 If the feed does not queue more requests when called, it will be
1143 automatically removed from the group.
1144
1145 If the feed limit is 0 when this method is called, it will be set to
1146 2 automatically.
1147
1148 Example:
1149
1150 # stat all files in @files, but only ever use four aio requests concurrently:
1151
1152 my $grp = aio_group sub { print "finished\n" };
1153 limit $grp 4;
1154 feed $grp sub {
1155 my $file = pop @files
1156 or return;
1157
1158 add $grp aio_stat $file, sub { ... };
1159 };
1160
1161 limit $grp $num
1162 Sets the feeder limit for the group: The feeder will be called
1163 whenever the group contains less than this many requests.
1164
1165 Setting the limit to 0 will pause the feeding process.
1166
1167 The default value for the limit is 0, but note that setting a feeder
1168 automatically bumps it up to 2.
1169
299 SUPPORT FUNCTIONS 1170 SUPPORT FUNCTIONS
1171 EVENT PROCESSING AND EVENT LOOP INTEGRATION
300 $fileno = IO::AIO::poll_fileno 1172 $fileno = IO::AIO::poll_fileno
301 Return the *request result pipe file descriptor*. This filehandle 1173 Return the *request result pipe file descriptor*. This filehandle
302 must be polled for reading by some mechanism outside this module 1174 must be polled for reading by some mechanism outside this module
303 (e.g. Event or select, see below or the SYNOPSIS). If the pipe 1175 (e.g. EV, Glib, select and so on, see below or the SYNOPSIS). If the
304 becomes readable you have to call "poll_cb" to check the results. 1176 pipe becomes readable you have to call "poll_cb" to check the
1177 results.
305 1178
306 See "poll_cb" for an example. 1179 See "poll_cb" for an example.
307 1180
308 IO::AIO::poll_cb 1181 IO::AIO::poll_cb
309 Process all outstanding events on the result pipe. You have to call 1182 Process some outstanding events on the result pipe. You have to call
310 this regularly. Returns the number of events processed. Returns 1183 this regularly. Returns 0 if all events could be processed (or there
1184 were no events to process), or -1 if it returned earlier for
311 immediately when no events are outstanding. 1185 whatever reason. Returns immediately when no events are outstanding.
1186 The amount of events processed depends on the settings of
1187 "IO::AIO::max_poll_req" and "IO::AIO::max_poll_time".
1188
1189 If not all requests were processed for whatever reason, the
1190 filehandle will still be ready when "poll_cb" returns, so normally
1191 you don't have to do anything special to have it called later.
1192
1193 Apart from calling "IO::AIO::poll_cb" when the event filehandle
1194 becomes ready, it can be beneficial to call this function from loops
1195 which submit a lot of requests, to make sure the results get
1196 processed when they become available and not just when the loop is
1197 finished and the event loop takes over again. This function returns
1198 very fast when there are no outstanding requests.
312 1199
313 Example: Install an Event watcher that automatically calls 1200 Example: Install an Event watcher that automatically calls
314 IO::AIO::poll_cb with high priority: 1201 IO::AIO::poll_cb with high priority (more examples can be found in
1202 the SYNOPSIS section, at the top of this document):
315 1203
316 Event->io (fd => IO::AIO::poll_fileno, 1204 Event->io (fd => IO::AIO::poll_fileno,
317 poll => 'r', async => 1, 1205 poll => 'r', async => 1,
318 cb => \&IO::AIO::poll_cb); 1206 cb => \&IO::AIO::poll_cb);
319 1207
320 IO::AIO::poll_wait 1208 IO::AIO::poll_wait
1209 If there are any outstanding requests and none of them in the result
321 Wait till the result filehandle becomes ready for reading (simply 1210 phase, wait till the result filehandle becomes ready for reading
322 does a "select" on the filehandle. This is useful if you want to 1211 (simply does a "select" on the filehandle. This is useful if you
323 synchronously wait for some requests to finish). 1212 want to synchronously wait for some requests to finish).
324 1213
325 See "nreqs" for an example. 1214 See "nreqs" for an example.
326 1215
1216 IO::AIO::poll
1217 Waits until some requests have been handled.
1218
1219 Returns the number of requests processed, but is otherwise strictly
1220 equivalent to:
1221
1222 IO::AIO::poll_wait, IO::AIO::poll_cb
1223
327 IO::AIO::nreqs 1224 IO::AIO::flush
328 Returns the number of requests currently outstanding (i.e. for which 1225 Wait till all outstanding AIO requests have been handled.
329 their callback has not been invoked yet).
330 1226
331 Example: wait till there are no outstanding requests anymore: 1227 Strictly equivalent to:
332 1228
333 IO::AIO::poll_wait, IO::AIO::poll_cb 1229 IO::AIO::poll_wait, IO::AIO::poll_cb
334 while IO::AIO::nreqs; 1230 while IO::AIO::nreqs;
335 1231
336 IO::AIO::flush 1232 IO::AIO::max_poll_reqs $nreqs
337 Wait till all outstanding AIO requests have been handled. 1233 IO::AIO::max_poll_time $seconds
1234 These set the maximum number of requests (default 0, meaning
1235 infinity) that are being processed by "IO::AIO::poll_cb" in one
1236 call, respectively the maximum amount of time (default 0, meaning
1237 infinity) spent in "IO::AIO::poll_cb" to process requests (more
1238 correctly the mininum amount of time "poll_cb" is allowed to use).
338 1239
339 Strictly equivalent to: 1240 Setting "max_poll_time" to a non-zero value creates an overhead of
1241 one syscall per request processed, which is not normally a problem
1242 unless your callbacks are really really fast or your OS is really
1243 really slow (I am not mentioning Solaris here). Using
1244 "max_poll_reqs" incurs no overhead.
340 1245
341 IO::AIO::poll_wait, IO::AIO::poll_cb 1246 Setting these is useful if you want to ensure some level of
342 while IO::AIO::nreqs; 1247 interactiveness when perl is not fast enough to process all requests
1248 in time.
343 1249
344 IO::AIO::poll 1250 For interactive programs, values such as 0.01 to 0.1 should be fine.
345 Waits until some requests have been handled.
346 1251
347 Strictly equivalent to: 1252 Example: Install an Event watcher that automatically calls
1253 IO::AIO::poll_cb with low priority, to ensure that other parts of
1254 the program get the CPU sometimes even under high AIO load.
348 1255
349 IO::AIO::poll_wait, IO::AIO::poll_cb 1256 # try not to spend much more than 0.1s in poll_cb
350 if IO::AIO::nreqs; 1257 IO::AIO::max_poll_time 0.1;
351 1258
1259 # use a low priority so other tasks have priority
1260 Event->io (fd => IO::AIO::poll_fileno,
1261 poll => 'r', nice => 1,
1262 cb => &IO::AIO::poll_cb);
1263
1264 CONTROLLING THE NUMBER OF THREADS
352 IO::AIO::min_parallel $nthreads 1265 IO::AIO::min_parallel $nthreads
353 Set the minimum number of AIO threads to $nthreads. The current 1266 Set the minimum number of AIO threads to $nthreads. The current
354 default is 4, which means four asynchronous operations can be done 1267 default is 8, which means eight asynchronous operations can execute
355 at one time (the number of outstanding operations, however, is 1268 concurrently at any one time (the number of outstanding requests,
356 unlimited). 1269 however, is unlimited).
357 1270
358 IO::AIO starts threads only on demand, when an AIO request is queued 1271 IO::AIO starts threads only on demand, when an AIO request is queued
359 and no free thread exists. 1272 and no free thread exists. Please note that queueing up a hundred
1273 requests can create demand for a hundred threads, even if it turns
1274 out that everything is in the cache and could have been processed
1275 faster by a single thread.
360 1276
361 It is recommended to keep the number of threads low, as some Linux 1277 It is recommended to keep the number of threads relatively low, as
362 kernel versions will scale negatively with the number of threads 1278 some Linux kernel versions will scale negatively with the number of
363 (higher parallelity => MUCH higher latency). With current Linux 2.6 1279 threads (higher parallelity => MUCH higher latency). With current
364 versions, 4-32 threads should be fine. 1280 Linux 2.6 versions, 4-32 threads should be fine.
365 1281
366 Under most circumstances you don't need to call this function, as 1282 Under most circumstances you don't need to call this function, as
367 the module selects a default that is suitable for low to moderate 1283 the module selects a default that is suitable for low to moderate
368 load. 1284 load.
369 1285
… …
379 ensure that all threads are killed and that there are no outstanding 1295 ensure that all threads are killed and that there are no outstanding
380 requests. 1296 requests.
381 1297
382 Under normal circumstances you don't need to call this function. 1298 Under normal circumstances you don't need to call this function.
383 1299
1300 IO::AIO::max_idle $nthreads
1301 Limit the number of threads (default: 4) that are allowed to idle
1302 (i.e., threads that did not get a request to process within the idle
1303 timeout (default: 10 seconds). That means if a thread becomes idle
1304 while $nthreads other threads are also idle, it will free its
1305 resources and exit.
1306
1307 This is useful when you allow a large number of threads (e.g. 100 or
1308 1000) to allow for extremely high load situations, but want to free
1309 resources under normal circumstances (1000 threads can easily
1310 consume 30MB of RAM).
1311
1312 The default is probably ok in most situations, especially if thread
1313 creation is fast. If thread creation is very slow on your system you
1314 might want to use larger values.
1315
1316 IO::AIO::idle_timeout $seconds
1317 Sets the minimum idle timeout (default 10) after which worker
1318 threads are allowed to exit. SEe "IO::AIO::max_idle".
1319
384 $oldnreqs = IO::AIO::max_outstanding $nreqs 1320 IO::AIO::max_outstanding $maxreqs
385 Sets the maximum number of outstanding requests to $nreqs. If you 1321 Sets the maximum number of outstanding requests to $nreqs. If you do
386 try to queue up more than this number of requests, the caller will 1322 queue up more than this number of requests, the next call to
1323 "IO::AIO::poll_cb" (and other functions calling "poll_cb", such as
1324 "IO::AIO::flush" or "IO::AIO::poll") will block until the limit is
1325 no longer exceeded.
1326
1327 In other words, this setting does not enforce a queue limit, but can
1328 be used to make poll functions block if the limit is exceeded.
1329
1330 This is a very bad function to use in interactive programs because
1331 it blocks, and a bad way to reduce concurrency because it is
1332 inexact: Better use an "aio_group" together with a feed callback.
1333
1334 It's main use is in scripts without an event loop - when you want to
1335 stat a lot of files, you can write somehting like this:
1336
1337 IO::AIO::max_outstanding 32;
1338
1339 for my $path (...) {
1340 aio_stat $path , ...;
1341 IO::AIO::poll_cb;
1342 }
1343
1344 IO::AIO::flush;
1345
1346 The call to "poll_cb" inside the loop will normally return
1347 instantly, but as soon as more thna 32 reqeusts are in-flight, it
387 block until some requests have been handled. 1348 will block until some requests have been handled. This keeps the
1349 loop from pushing a large number of "aio_stat" requests onto the
1350 queue.
388 1351
389 The default is very large, so normally there is no practical limit. 1352 The default value for "max_outstanding" is very large, so there is
390 If you queue up many requests in a loop it often improves speed if 1353 no practical limit on the number of outstanding requests.
391 you set this to a relatively low number, such as 100.
392 1354
393 Under normal circumstances you don't need to call this function. 1355 STATISTICAL INFORMATION
1356 IO::AIO::nreqs
1357 Returns the number of requests currently in the ready, execute or
1358 pending states (i.e. for which their callback has not been invoked
1359 yet).
1360
1361 Example: wait till there are no outstanding requests anymore:
1362
1363 IO::AIO::poll_wait, IO::AIO::poll_cb
1364 while IO::AIO::nreqs;
1365
1366 IO::AIO::nready
1367 Returns the number of requests currently in the ready state (not yet
1368 executed).
1369
1370 IO::AIO::npending
1371 Returns the number of requests currently in the pending state
1372 (executed, but not yet processed by poll_cb).
1373
1374 MISCELLANEOUS FUNCTIONS
1375 IO::AIO implements some functions that might be useful, but are not
1376 asynchronous.
1377
1378 IO::AIO::sendfile $ofh, $ifh, $offset, $count
1379 Calls the "eio_sendfile_sync" function, which is like
1380 "aio_sendfile", but is blocking (this makes most sense if you know
1381 the input data is likely cached already and the output filehandle is
1382 set to non-blocking operations).
1383
1384 Returns the number of bytes copied, or -1 on error.
1385
1386 IO::AIO::fadvise $fh, $offset, $len, $advice
1387 Simply calls the "posix_fadvise" function (see its manpage for
1388 details). The following advice constants are available:
1389 "IO::AIO::FADV_NORMAL", "IO::AIO::FADV_SEQUENTIAL",
1390 "IO::AIO::FADV_RANDOM", "IO::AIO::FADV_NOREUSE",
1391 "IO::AIO::FADV_WILLNEED", "IO::AIO::FADV_DONTNEED".
1392
1393 On systems that do not implement "posix_fadvise", this function
1394 returns ENOSYS, otherwise the return value of "posix_fadvise".
1395
1396 IO::AIO::madvise $scalar, $offset, $len, $advice
1397 Simply calls the "posix_madvise" function (see its manpage for
1398 details). The following advice constants are available:
1399 "IO::AIO::MADV_NORMAL", "IO::AIO::MADV_SEQUENTIAL",
1400 "IO::AIO::MADV_RANDOM", "IO::AIO::MADV_WILLNEED",
1401 "IO::AIO::MADV_DONTNEED".
1402
1403 On systems that do not implement "posix_madvise", this function
1404 returns ENOSYS, otherwise the return value of "posix_madvise".
1405
1406 IO::AIO::mprotect $scalar, $offset, $len, $protect
1407 Simply calls the "mprotect" function on the preferably AIO::mmap'ed
1408 $scalar (see its manpage for details). The following protect
1409 constants are available: "IO::AIO::PROT_NONE", "IO::AIO::PROT_READ",
1410 "IO::AIO::PROT_WRITE", "IO::AIO::PROT_EXEC".
1411
1412 On systems that do not implement "mprotect", this function returns
1413 ENOSYS, otherwise the return value of "mprotect".
1414
1415 IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
1416 Memory-maps a file (or anonymous memory range) and attaches it to
1417 the given $scalar, which will act like a string scalar.
1418
1419 The only operations allowed on the scalar are "substr"/"vec" that
1420 don't change the string length, and most read-only operations such
1421 as copying it or searching it with regexes and so on.
1422
1423 Anything else is unsafe and will, at best, result in memory leaks.
1424
1425 The memory map associated with the $scalar is automatically removed
1426 when the $scalar is destroyed, or when the "IO::AIO::mmap" or
1427 "IO::AIO::munmap" functions are called.
1428
1429 This calls the "mmap"(2) function internally. See your system's
1430 manual page for details on the $length, $prot and $flags parameters.
1431
1432 The $length must be larger than zero and smaller than the actual
1433 filesize.
1434
1435 $prot is a combination of "IO::AIO::PROT_NONE",
1436 "IO::AIO::PROT_EXEC", "IO::AIO::PROT_READ" and/or
1437 "IO::AIO::PROT_WRITE",
1438
1439 $flags can be a combination of "IO::AIO::MAP_SHARED" or
1440 "IO::AIO::MAP_PRIVATE", or a number of system-specific flags (when
1441 not available, the are defined as 0): "IO::AIO::MAP_ANONYMOUS"
1442 (which is set to "MAP_ANON" if your system only provides this
1443 constant), "IO::AIO::MAP_HUGETLB", "IO::AIO::MAP_LOCKED",
1444 "IO::AIO::MAP_NORESERVE", "IO::AIO::MAP_POPULATE" or
1445 "IO::AIO::MAP_NONBLOCK"
1446
1447 If $fh is "undef", then a file descriptor of -1 is passed.
1448
1449 $offset is the offset from the start of the file - it generally must
1450 be a multiple of "IO::AIO::PAGESIZE" and defaults to 0.
1451
1452 Example:
1453
1454 use Digest::MD5;
1455 use IO::AIO;
1456
1457 open my $fh, "<verybigfile"
1458 or die "$!";
1459
1460 IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
1461 or die "verybigfile: $!";
1462
1463 my $fast_md5 = md5 $data;
1464
1465 IO::AIO::munmap $scalar
1466 Removes a previous mmap and undefines the $scalar.
1467
1468 IO::AIO::munlock $scalar, $offset = 0, $length = undef
1469 Calls the "munlock" function, undoing the effects of a previous
1470 "aio_mlock" call (see its description for details).
1471
1472 IO::AIO::munlockall
1473 Calls the "munlockall" function.
1474
1475 On systems that do not implement "munlockall", this function returns
1476 ENOSYS, otherwise the return value of "munlockall".
1477
1478EVENT LOOP INTEGRATION
1479 It is recommended to use AnyEvent::AIO to integrate IO::AIO
1480 automatically into many event loops:
1481
1482 # AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
1483 use AnyEvent::AIO;
1484
1485 You can also integrate IO::AIO manually into many event loops, here are
1486 some examples of how to do this:
1487
1488 # EV integration
1489 my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
1490
1491 # Event integration
1492 Event->io (fd => IO::AIO::poll_fileno,
1493 poll => 'r',
1494 cb => \&IO::AIO::poll_cb);
1495
1496 # Glib/Gtk2 integration
1497 add_watch Glib::IO IO::AIO::poll_fileno,
1498 in => sub { IO::AIO::poll_cb; 1 };
1499
1500 # Tk integration
1501 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
1502 readable => \&IO::AIO::poll_cb);
1503
1504 # Danga::Socket integration
1505 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
1506 \&IO::AIO::poll_cb);
394 1507
395 FORK BEHAVIOUR 1508 FORK BEHAVIOUR
396 Before the fork, IO::AIO enters a quiescent state where no requests can 1509 Usage of pthreads in a program changes the semantics of fork
397 be added in other threads and no results will be processed. After the 1510 considerably. Specifically, only async-safe functions can be called
398 fork the parent simply leaves the quiescent state and continues 1511 after fork. Perl doesn't know about this, so in general, you cannot call
399 request/result processing, while the child clears the request/result 1512 fork with defined behaviour in perl if pthreads are involved. IO::AIO
400 queue (so the requests started before the fork will only be handled in 1513 uses pthreads, so this applies, but many other extensions and (for
401 the parent). Threats will be started on demand until the limit ste in 1514 inexplicable reasons) perl itself often is linked against pthreads, so
402 the parent process has been reached again. 1515 this limitation applies to quite a lot of perls.
1516
1517 This module no longer tries to fight your OS, or POSIX. That means
1518 IO::AIO only works in the process that loaded it. Forking is fully
1519 supported, but using IO::AIO in the child is not.
1520
1521 You might get around by not *using* IO::AIO before (or after) forking.
1522 You could also try to call the IO::AIO::reinit function in the child:
1523
1524 IO::AIO::reinit
1525 Abandons all current requests and I/O threads and simply
1526 reinitialises all data structures. This is not an operation
1527 supported by any standards, but happens to work on GNU/Linux and
1528 some newer BSD systems.
1529
1530 The only reasonable use for this function is to call it after
1531 forking, if "IO::AIO" was used in the parent. Calling it while
1532 IO::AIO is active in the process will result in undefined behaviour.
1533 Calling it at any time will also result in any undefined (by POSIX)
1534 behaviour.
1535
1536 MEMORY USAGE
1537 Per-request usage:
1538
1539 Each aio request uses - depending on your architecture - around 100-200
1540 bytes of memory. In addition, stat requests need a stat buffer (possibly
1541 a few hundred bytes), readdir requires a result buffer and so on. Perl
1542 scalars and other data passed into aio requests will also be locked and
1543 will consume memory till the request has entered the done state.
1544
1545 This is not awfully much, so queuing lots of requests is not usually a
1546 problem.
1547
1548 Per-thread usage:
1549
1550 In the execution phase, some aio requests require more memory for
1551 temporary buffers, and each thread requires a stack and other data
1552 structures (usually around 16k-128k, depending on the OS).
1553
1554KNOWN BUGS
1555 Known bugs will be fixed in the next release.
403 1556
404SEE ALSO 1557SEE ALSO
405 Coro, Linux::AIO. 1558 AnyEvent::AIO for easy integration into event loops, Coro::AIO for a
1559 more natural syntax.
406 1560
407AUTHOR 1561AUTHOR
408 Marc Lehmann <schmorp@schmorp.de> 1562 Marc Lehmann <schmorp@schmorp.de>
409 http://home.schmorp.de/ 1563 http://home.schmorp.de/
410 1564

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