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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", IO::AIO::O_RDONLY, 0, sub {
8 my $fh = shift
9 or die "/etc/passwd: $!";
10 ...
11 };
12
13 aio_unlink "/tmp/file", sub { };
14
15 aio_read $fh, 30000, 1024, $buffer, 0, sub {
16 $_[0] > 0 or die "read error: $!";
17 };
18
19 # version 2+ has request and group objects
20 use IO::AIO 2;
21
22 aioreq_pri 4; # give next request a very high priority
23 my $req = aio_unlink "/tmp/file", sub { };
24 $req->cancel; # cancel request if still in queue
25
26 my $grp = aio_group sub { print "all stats done\n" };
27 add $grp aio_stat "..." for ...;
28
7DESCRIPTION 29DESCRIPTION
8 This module implements asynchronous I/O using whatever means your 30 This module implements asynchronous I/O using whatever means your
9 operating system supports. 31 operating system supports. It is implemented as an interface to "libeio"
32 (<http://software.schmorp.de/pkg/libeio.html>).
10 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
11 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
12 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
13 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
14 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
15 native aio functions available on many operating systems. However, they 54 functions available on many operating systems. However, they are often
16 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
17 currently, for example), and they would only support aio_read and 56 files currently, for example), and they would only support aio_read and
18 aio_write, so the remaining functionality would have to be implemented 57 aio_write, so the remaining functionality would have to be implemented
19 using threads anyway. 58 using threads anyway.
20 59
21 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,
22 is currently not reentrant, so use appropriate locking yourself. 61 it is currently not reentrant in any way, so use appropriate locking
62 yourself, always call "poll_cb" from within the same thread, or never
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 EV;
70 use IO::AIO;
71
72 # register the IO::AIO callback with EV
73 my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
74
75 # queue the request to open /etc/passwd
76 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
77 my $fh = shift
78 or die "error while opening: $!";
79
80 # stat'ing filehandles is generally non-blocking
81 my $size = -s $fh;
82
83 # queue a request to read the file
84 my $contents;
85 aio_read $fh, 0, $size, $contents, 0, sub {
86 $_[0] == $size
87 or die "short read: $!";
88
89 close $fh;
90
91 # file contents now in $contents
92 print $contents;
93
94 # exit event loop and program
95 EV::break;
96 };
97 };
98
99 # possibly queue up other requests, or open GUI windows,
100 # check for sockets etc. etc.
101
102 # process events as long as there are some:
103 EV::run;
104
105REQUEST ANATOMY AND LIFETIME
106 Every "aio_*" function creates a request. which is a C data structure
107 not directly visible to Perl.
108
109 If called in non-void context, every request function returns a Perl
110 object representing the request. In void context, nothing is returned,
111 which saves a bit of memory.
112
113 The perl object is a fairly standard ref-to-hash object. The hash
114 contents are not used by IO::AIO so you are free to store anything you
115 like in it.
116
117 During their existance, aio requests travel through the following
118 states, in order:
119
120 ready
121 Immediately after a request is created it is put into the ready
122 state, waiting for a thread to execute it.
123
124 execute
125 A thread has accepted the request for processing and is currently
126 executing it (e.g. blocking in read).
127
128 pending
129 The request has been executed and is waiting for result processing.
130
131 While request submission and execution is fully asynchronous, result
132 processing is not and relies on the perl interpreter calling
133 "poll_cb" (or another function with the same effect).
134
135 result
136 The request results are processed synchronously by "poll_cb".
137
138 The "poll_cb" function will process all outstanding aio requests by
139 calling their callbacks, freeing memory associated with them and
140 managing any groups they are contained in.
141
142 done
143 Request has reached the end of its lifetime and holds no resources
144 anymore (except possibly for the Perl object, but its connection to
145 the actual aio request is severed and calling its methods will
146 either do nothing or result in a runtime error).
147
148FUNCTIONS
149 QUICK OVERVIEW
150 This section simply lists the prototypes most of the functions for quick
151 reference. See the following sections for function-by-function
152 documentation.
153
154 aio_wd $pathname, $callback->($wd)
155 aio_open $pathname, $flags, $mode, $callback->($fh)
156 aio_close $fh, $callback->($status)
157 aio_seek $fh,$offset,$whence, $callback->($offs)
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_chmod $fh_or_path, $mode, $callback->($status)
168 aio_truncate $fh_or_path, $offset, $callback->($status)
169 aio_allocate $fh, $mode, $offset, $len, $callback->($status)
170 aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
171 aio_unlink $pathname, $callback->($status)
172 aio_mknod $pathname, $mode, $dev, $callback->($status)
173 aio_link $srcpath, $dstpath, $callback->($status)
174 aio_symlink $srcpath, $dstpath, $callback->($status)
175 aio_readlink $pathname, $callback->($link)
176 aio_realpath $pathname, $callback->($path)
177 aio_rename $srcpath, $dstpath, $callback->($status)
178 aio_mkdir $pathname, $mode, $callback->($status)
179 aio_rmdir $pathname, $callback->($status)
180 aio_readdir $pathname, $callback->($entries)
181 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
182 IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
183 IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
184 aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
185 aio_load $pathname, $data, $callback->($status)
186 aio_copy $srcpath, $dstpath, $callback->($status)
187 aio_move $srcpath, $dstpath, $callback->($status)
188 aio_rmtree $pathname, $callback->($status)
189 aio_fcntl $fh, $cmd, $arg, $callback->($status)
190 aio_ioctl $fh, $request, $buf, $callback->($status)
191 aio_sync $callback->($status)
192 aio_syncfs $fh, $callback->($status)
193 aio_fsync $fh, $callback->($status)
194 aio_fdatasync $fh, $callback->($status)
195 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
196 aio_pathsync $pathname, $callback->($status)
197 aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
198 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
199 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
200 aio_mlockall $flags, $callback->($status)
201 aio_group $callback->(...)
202 aio_nop $callback->()
203
204 $prev_pri = aioreq_pri [$pri]
205 aioreq_nice $pri_adjust
206
207 IO::AIO::poll_wait
208 IO::AIO::poll_cb
209 IO::AIO::poll
210 IO::AIO::flush
211 IO::AIO::max_poll_reqs $nreqs
212 IO::AIO::max_poll_time $seconds
213 IO::AIO::min_parallel $nthreads
214 IO::AIO::max_parallel $nthreads
215 IO::AIO::max_idle $nthreads
216 IO::AIO::idle_timeout $seconds
217 IO::AIO::max_outstanding $maxreqs
218 IO::AIO::nreqs
219 IO::AIO::nready
220 IO::AIO::npending
221
222 IO::AIO::sendfile $ofh, $ifh, $offset, $count
223 IO::AIO::fadvise $fh, $offset, $len, $advice
224 IO::AIO::mmap $scalar, $length, $prot, $flags[, $fh[, $offset]]
225 IO::AIO::munmap $scalar
226 IO::AIO::madvise $scalar, $offset, $length, $advice
227 IO::AIO::mprotect $scalar, $offset, $length, $protect
228 IO::AIO::munlock $scalar, $offset = 0, $length = undef
229 IO::AIO::munlockall
23 230
24 API NOTES 231 API NOTES
25 All the "aio_*" calls are more or less thin wrappers around the syscall 232 All the "aio_*" calls are more or less thin wrappers around the syscall
26 with the same name (sans "aio_"). The arguments are similar or 233 with the same name (sans "aio_"). The arguments are similar or
27 identical, and they all accept an additional $callback argument which 234 identical, and they all accept an additional (and optional) $callback
28 must be a code reference. This code reference will get called with the 235 argument which must be a code reference. This code reference will be
236 called after the syscall has been executed in an asynchronous fashion.
237 The results of the request will be passed as arguments to the callback
238 (and, if an error occured, in $!) - for most requests the syscall return
29 syscall return code (e.g. most syscalls return -1 on error, unlike perl, 239 code (e.g. most syscalls return -1 on error, unlike perl, which usually
30 which usually delivers "false") as it's sole argument when the given 240 delivers "false").
31 syscall has been executed asynchronously.
32 241
33 All functions that expect a filehandle will also accept a file 242 Some requests (such as "aio_readdir") pass the actual results and
34 descriptor. 243 communicate failures by passing "undef".
35 244
245 All functions expecting a filehandle keep a copy of the filehandle
246 internally until the request has finished.
247
248 All functions return request objects of type IO::AIO::REQ that allow
249 further manipulation of those requests while they are in-flight.
250
36 The filenames you pass to these routines *must* be absolute. The reason 251 The pathnames you pass to these routines *should* be absolute. The
37 is that at the time the request is being executed, the current working 252 reason for this is that at the time the request is being executed, the
38 directory could have changed. Alternatively, you can make sure that you 253 current working directory could have changed. Alternatively, you can
39 never change the current working directory. 254 make sure that you never change the current working directory anywhere
255 in the program and then use relative paths. You can also take advantage
256 of IO::AIOs working directory abstraction, that lets you specify paths
257 relative to some previously-opened "working directory object" - see the
258 description of the "IO::AIO::WD" class later in this document.
40 259
41 IO::AIO::min_parallel $nthreads 260 To encode pathnames as octets, either make sure you either: a) always
42 Set the minimum number of AIO threads to $nthreads. The default is 261 pass in filenames you got from outside (command line, readdir etc.)
43 1, which means a single asynchronous operation can be done at one 262 without tinkering, b) are in your native filesystem encoding, c) use the
44 time (the number of outstanding operations, however, is unlimited). 263 Encode module and encode your pathnames to the locale (or other)
264 encoding in effect in the user environment, d) use
265 Glib::filename_from_unicode on unicode filenames or e) use something
266 else to ensure your scalar has the correct contents.
45 267
46 It is recommended to keep the number of threads low, as some linux 268 This works, btw. independent of the internal UTF-8 bit, which IO::AIO
47 kernel versions will scale negatively with the number of threads 269 handles correctly whether it is set or not.
48 (higher parallelity => MUCH higher latency).
49 270
50 Under normal circumstances you don't need to call this function, as 271 AIO REQUEST FUNCTIONS
51 this module automatically starts a single async thread. 272 $prev_pri = aioreq_pri [$pri]
273 Returns the priority value that would be used for the next request
274 and, if $pri is given, sets the priority for the next aio request.
52 275
53 IO::AIO::max_parallel $nthreads 276 The default priority is 0, the minimum and maximum priorities are -4
54 Sets the maximum number of AIO threads to $nthreads. If more than 277 and 4, respectively. Requests with higher priority will be serviced
55 the specified number of threads are currently running, kill them.
56 This function blocks until the limit is reached.
57
58 This module automatically runs "max_parallel 0" at program end, to
59 ensure that all threads are killed and that there are no outstanding
60 requests. 278 first.
61 279
62 Under normal circumstances you don't need to call this function. 280 The priority will be reset to 0 after each call to one of the
281 "aio_*" functions.
63 282
64 $fileno = IO::AIO::poll_fileno 283 Example: open a file with low priority, then read something from it
65 Return the *request result pipe filehandle*. This filehandle must be 284 with higher priority so the read request is serviced before other
66 polled for reading by some mechanism outside this module (e.g. Event 285 low priority open requests (potentially spamming the cache):
67 or select, see below). If the pipe becomes readable you have to call
68 "poll_cb" to check the results.
69 286
70 See "poll_cb" for an example. 287 aioreq_pri -3;
288 aio_open ..., sub {
289 return unless $_[0];
71 290
72 IO::AIO::poll_cb 291 aioreq_pri -2;
73 Process all outstanding events on the result pipe. You have to call 292 aio_read $_[0], ..., sub {
74 this regularly. Returns the number of events processed. Returns 293 ...
75 immediately when no events are outstanding. 294 };
295 };
76 296
77 You can use Event to multiplex, e.g.: 297 aioreq_nice $pri_adjust
298 Similar to "aioreq_pri", but subtracts the given value from the
299 current priority, so the effect is cumulative.
78 300
79 Event->io (fd => IO::AIO::poll_fileno,
80 poll => 'r', async => 1,
81 cb => \&IO::AIO::poll_cb);
82
83 IO::AIO::poll_wait
84 Wait till the result filehandle becomes ready for reading (simply
85 does a select on the filehandle. This is useful if you want to
86 synchronously wait for some requests to finish).
87
88 See "nreqs" for an example.
89
90 IO::AIO::nreqs
91 Returns the number of requests currently outstanding.
92
93 Example: wait till there are no outstanding requests anymore:
94
95 IO::AIO::poll_wait, IO::AIO::poll_cb
96 while IO::AIO::nreqs;
97
98 aio_open $pathname, $flags, $mode, $callback 301 aio_open $pathname, $flags, $mode, $callback->($fh)
99 Asynchronously open or create a file and call the callback with a 302 Asynchronously open or create a file and call the callback with a
100 newly created filehandle for the file. 303 newly created filehandle for the file (or "undef" in case of an
304 error).
101 305
102 The pathname passed to "aio_open" must be absolute. See API NOTES, 306 The pathname passed to "aio_open" must be absolute. See API NOTES,
103 above, for an explanation. 307 above, for an explanation.
104 308
105 The $mode argument is a bitmask. See the "Fcntl" module for a list. 309 The $flags argument is a bitmask. See the "Fcntl" module for a list.
106 They are the same as used in "sysopen". 310 They are the same as used by "sysopen".
311
312 Likewise, $mode specifies the mode of the newly created file, if it
313 didn't exist and "O_CREAT" has been given, just like perl's
314 "sysopen", except that it is mandatory (i.e. use 0 if you don't
315 create new files, and 0666 or 0777 if you do). Note that the $mode
316 will be modified by the umask in effect then the request is being
317 executed, so better never change the umask.
107 318
108 Example: 319 Example:
109 320
110 aio_open "/etc/passwd", O_RDONLY, 0, sub { 321 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
111 if ($_[0]) { 322 if ($_[0]) {
112 print "open successful, fh is $_[0]\n"; 323 print "open successful, fh is $_[0]\n";
113 ... 324 ...
114 } else { 325 } else {
115 die "open failed: $!\n"; 326 die "open failed: $!\n";
116 } 327 }
117 }; 328 };
118 329
330 In addition to all the common open modes/flags ("O_RDONLY",
331 "O_WRONLY", "O_RDWR", "O_CREAT", "O_TRUNC", "O_EXCL" and
332 "O_APPEND"), the following POSIX and non-POSIX constants are
333 available (missing ones on your system are, as usual, 0):
334
335 "O_ASYNC", "O_DIRECT", "O_NOATIME", "O_CLOEXEC", "O_NOCTTY",
336 "O_NOFOLLOW", "O_NONBLOCK", "O_EXEC", "O_SEARCH", "O_DIRECTORY",
337 "O_DSYNC", "O_RSYNC", "O_SYNC", "O_PATH", "O_TMPFILE", and
338 "O_TTY_INIT".
339
119 aio_close $fh, $callback 340 aio_close $fh, $callback->($status)
120 Asynchronously close a file and call the callback with the result 341 Asynchronously close a file and call the callback with the result
121 code. *WARNING:* although accepted, you should not pass in a perl 342 code.
122 filehandle here, as perl will likely close the file descriptor
123 itself when the filehandle is destroyed. Normally, you can safely
124 call perls "close" or just let filehandles go out of scope.
125 343
344 Unfortunately, you can't do this to perl. Perl *insists* very
345 strongly on closing the file descriptor associated with the
346 filehandle itself.
347
348 Therefore, "aio_close" will not close the filehandle - instead it
349 will use dup2 to overwrite the file descriptor with the write-end of
350 a pipe (the pipe fd will be created on demand and will be cached).
351
352 Or in other words: the file descriptor will be closed, but it will
353 not be free for reuse until the perl filehandle is closed.
354
355 aio_seek $fh, $offset, $whence, $callback->($offs)
356 Seeks the filehandle to the new $offset, similarly to perl's
357 "sysseek". The $whence can use the traditional values (0 for
358 "IO::AIO::SEEK_SET", 1 for "IO::AIO::SEEK_CUR" or 2 for
359 "IO::AIO::SEEK_END").
360
361 The resulting absolute offset will be passed to the callback, or -1
362 in case of an error.
363
364 In theory, the $whence constants could be different than the
365 corresponding values from Fcntl, but perl guarantees they are the
366 same, so don't panic.
367
368 As a GNU/Linux (and maybe Solaris) extension, also the constants
369 "IO::AIO::SEEK_DATA" and "IO::AIO::SEEK_HOLE" are available, if they
370 could be found. No guarantees about suitability for use in
371 "aio_seek" or Perl's "sysseek" can be made though, although I would
372 naively assume they "just work".
373
126 aio_read $fh,$offset,$length, $data,$dataoffset,$callback 374 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
127 aio_write $fh,$offset,$length, $data,$dataoffset,$callback 375 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
128 Reads or writes "length" bytes from the specified "fh" and "offset" 376 Reads or writes $length bytes from or to the specified $fh and
129 into the scalar given by "data" and offset "dataoffset" and calls 377 $offset into the scalar given by $data and offset $dataoffset and
130 the callback without the actual number of bytes read (or -1 on 378 calls the callback without the actual number of bytes read (or -1 on
131 error, just like the syscall). 379 error, just like the syscall).
132 380
381 "aio_read" will, like "sysread", shrink or grow the $data scalar to
382 offset plus the actual number of bytes read.
383
384 If $offset is undefined, then the current file descriptor offset
385 will be used (and updated), otherwise the file descriptor offset
386 will not be changed by these calls.
387
388 If $length is undefined in "aio_write", use the remaining length of
389 $data.
390
391 If $dataoffset is less than zero, it will be counted from the end of
392 $data.
393
394 The $data scalar *MUST NOT* be modified in any way while the request
395 is outstanding. Modifying it can result in segfaults or World War
396 III (if the necessary/optional hardware is installed).
397
133 Example: Read 15 bytes at offset 7 into scalar $buffer, strating at 398 Example: Read 15 bytes at offset 7 into scalar $buffer, starting at
134 offset 0 within the scalar: 399 offset 0 within the scalar:
135 400
136 aio_read $fh, 7, 15, $buffer, 0, sub { 401 aio_read $fh, 7, 15, $buffer, 0, sub {
137 $_[0] >= 0 or die "read error: $!"; 402 $_[0] > 0 or die "read error: $!";
138 print "read <$buffer>\n"; 403 print "read $_[0] bytes: <$buffer>\n";
139 }; 404 };
140 405
406 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
407 Tries to copy $length bytes from $in_fh to $out_fh. It starts
408 reading at byte offset $in_offset, and starts writing at the current
409 file offset of $out_fh. Because of that, it is not safe to issue
410 more than one "aio_sendfile" per $out_fh, as they will interfere
411 with each other. The same $in_fh works fine though, as this function
412 does not move or use the file offset of $in_fh.
413
414 Please note that "aio_sendfile" can read more bytes from $in_fh than
415 are written, and there is no way to find out how many more bytes
416 have been read from "aio_sendfile" alone, as "aio_sendfile" only
417 provides the number of bytes written to $out_fh. Only if the result
418 value equals $length one can assume that $length bytes have been
419 read.
420
421 Unlike with other "aio_" functions, it makes a lot of sense to use
422 "aio_sendfile" on non-blocking sockets, as long as one end
423 (typically the $in_fh) is a file - the file I/O will then be
424 asynchronous, while the socket I/O will be non-blocking. Note,
425 however, that you can run into a trap where "aio_sendfile" reads
426 some data with readahead, then fails to write all data, and when the
427 socket is ready the next time, the data in the cache is already
428 lost, forcing "aio_sendfile" to again hit the disk. Explicit
429 "aio_read" + "aio_write" let's you better control resource usage.
430
431 This call tries to make use of a native "sendfile"-like syscall to
432 provide zero-copy operation. For this to work, $out_fh should refer
433 to a socket, and $in_fh should refer to an mmap'able file.
434
435 If a native sendfile cannot be found or it fails with "ENOSYS",
436 "EINVAL", "ENOTSUP", "EOPNOTSUPP", "EAFNOSUPPORT", "EPROTOTYPE" or
437 "ENOTSOCK", it will be emulated, so you can call "aio_sendfile" on
438 any type of filehandle regardless of the limitations of the
439 operating system.
440
441 As native sendfile syscalls (as practically any non-POSIX interface
442 hacked together in a hurry to improve benchmark numbers) tend to be
443 rather buggy on many systems, this implementation tries to work
444 around some known bugs in Linux and FreeBSD kernels (probably
445 others, too), but that might fail, so you really really should check
446 the return value of "aio_sendfile" - fewre bytes than expected might
447 have been transferred.
448
141 aio_readahead $fh,$offset,$length, $callback 449 aio_readahead $fh,$offset,$length, $callback->($retval)
142 Asynchronously reads the specified byte range into the page cache,
143 using the "readahead" syscall. If that syscall doesn't exist the
144 status will be -1 and $! is set to ENOSYS.
145
146 readahead() populates the page cache with data from a file so that 450 "aio_readahead" populates the page cache with data from a file so
147 subsequent reads from that file will not block on disk I/O. The 451 that subsequent reads from that file will not block on disk I/O. The
148 $offset argument specifies the starting point from which data is to 452 $offset argument specifies the starting point from which data is to
149 be read and $length specifies the number of bytes to be read. I/O is 453 be read and $length specifies the number of bytes to be read. I/O is
150 performed in whole pages, so that offset is effectively rounded down 454 performed in whole pages, so that offset is effectively rounded down
151 to a page boundary and bytes are read up to the next page boundary 455 to a page boundary and bytes are read up to the next page boundary
152 greater than or equal to (off-set+length). aio_readahead() does not 456 greater than or equal to (off-set+length). "aio_readahead" does not
153 read beyond the end of the file. The current file offset of the file 457 read beyond the end of the file. The current file offset of the file
154 is left unchanged. 458 is left unchanged.
155 459
460 If that syscall doesn't exist (likely if your OS isn't Linux) it
461 will be emulated by simply reading the data, which would have a
462 similar effect.
463
156 aio_stat $fh_or_path, $callback 464 aio_stat $fh_or_path, $callback->($status)
157 aio_lstat $fh, $callback 465 aio_lstat $fh, $callback->($status)
158 Works like perl's "stat" or "lstat" in void context. The callback 466 Works like perl's "stat" or "lstat" in void context. The callback
159 will be called after the stat and the results will be available 467 will be called after the stat and the results will be available
160 using "stat _" or "-s _" etc... 468 using "stat _" or "-s _" etc...
161 469
162 The pathname passed to "aio_stat" must be absolute. See API NOTES, 470 The pathname passed to "aio_stat" must be absolute. See API NOTES,
… …
165 Currently, the stats are always 64-bit-stats, i.e. instead of 473 Currently, the stats are always 64-bit-stats, i.e. instead of
166 returning an error when stat'ing a large file, the results will be 474 returning an error when stat'ing a large file, the results will be
167 silently truncated unless perl itself is compiled with large file 475 silently truncated unless perl itself is compiled with large file
168 support. 476 support.
169 477
478 To help interpret the mode and dev/rdev stat values, IO::AIO offers
479 the following constants and functions (if not implemented, the
480 constants will be 0 and the functions will either "croak" or fall
481 back on traditional behaviour).
482
483 "S_IFMT", "S_IFIFO", "S_IFCHR", "S_IFBLK", "S_IFLNK", "S_IFREG",
484 "S_IFDIR", "S_IFWHT", "S_IFSOCK", "IO::AIO::major $dev_t",
485 "IO::AIO::minor $dev_t", "IO::AIO::makedev $major, $minor".
486
170 Example: Print the length of /etc/passwd: 487 Example: Print the length of /etc/passwd:
171 488
172 aio_stat "/etc/passwd", sub { 489 aio_stat "/etc/passwd", sub {
173 $_[0] and die "stat failed: $!"; 490 $_[0] and die "stat failed: $!";
174 print "size is ", -s _, "\n"; 491 print "size is ", -s _, "\n";
175 }; 492 };
176 493
494 aio_statvfs $fh_or_path, $callback->($statvfs)
495 Works like the POSIX "statvfs" or "fstatvfs" syscalls, depending on
496 whether a file handle or path was passed.
497
498 On success, the callback is passed a hash reference with the
499 following members: "bsize", "frsize", "blocks", "bfree", "bavail",
500 "files", "ffree", "favail", "fsid", "flag" and "namemax". On
501 failure, "undef" is passed.
502
503 The following POSIX IO::AIO::ST_* constants are defined: "ST_RDONLY"
504 and "ST_NOSUID".
505
506 The following non-POSIX IO::AIO::ST_* flag masks are defined to
507 their correct value when available, or to 0 on systems that do not
508 support them: "ST_NODEV", "ST_NOEXEC", "ST_SYNCHRONOUS",
509 "ST_MANDLOCK", "ST_WRITE", "ST_APPEND", "ST_IMMUTABLE",
510 "ST_NOATIME", "ST_NODIRATIME" and "ST_RELATIME".
511
512 Example: stat "/wd" and dump out the data if successful.
513
514 aio_statvfs "/wd", sub {
515 my $f = $_[0]
516 or die "statvfs: $!";
517
518 use Data::Dumper;
519 say Dumper $f;
520 };
521
522 # result:
523 {
524 bsize => 1024,
525 bfree => 4333064312,
526 blocks => 10253828096,
527 files => 2050765568,
528 flag => 4096,
529 favail => 2042092649,
530 bavail => 4333064312,
531 ffree => 2042092649,
532 namemax => 255,
533 frsize => 1024,
534 fsid => 1810
535 }
536
537 Here is a (likely partial - send me updates!) list of fsid values
538 used by Linux - it is safe to hardcode these when $^O is "linux":
539
540 0x0000adf5 adfs
541 0x0000adff affs
542 0x5346414f afs
543 0x09041934 anon-inode filesystem
544 0x00000187 autofs
545 0x42465331 befs
546 0x1badface bfs
547 0x42494e4d binfmt_misc
548 0x9123683e btrfs
549 0x0027e0eb cgroupfs
550 0xff534d42 cifs
551 0x73757245 coda
552 0x012ff7b7 coh
553 0x28cd3d45 cramfs
554 0x453dcd28 cramfs-wend (wrong endianness)
555 0x64626720 debugfs
556 0x00001373 devfs
557 0x00001cd1 devpts
558 0x0000f15f ecryptfs
559 0x00414a53 efs
560 0x0000137d ext
561 0x0000ef53 ext2/ext3/ext4
562 0x0000ef51 ext2
563 0xf2f52010 f2fs
564 0x00004006 fat
565 0x65735546 fuseblk
566 0x65735543 fusectl
567 0x0bad1dea futexfs
568 0x01161970 gfs2
569 0x47504653 gpfs
570 0x00004244 hfs
571 0xf995e849 hpfs
572 0x00c0ffee hostfs
573 0x958458f6 hugetlbfs
574 0x2bad1dea inotifyfs
575 0x00009660 isofs
576 0x000072b6 jffs2
577 0x3153464a jfs
578 0x6b414653 k-afs
579 0x0bd00bd0 lustre
580 0x0000137f minix
581 0x0000138f minix 30 char names
582 0x00002468 minix v2
583 0x00002478 minix v2 30 char names
584 0x00004d5a minix v3
585 0x19800202 mqueue
586 0x00004d44 msdos
587 0x0000564c novell
588 0x00006969 nfs
589 0x6e667364 nfsd
590 0x00003434 nilfs
591 0x5346544e ntfs
592 0x00009fa1 openprom
593 0x7461636F ocfs2
594 0x00009fa0 proc
595 0x6165676c pstorefs
596 0x0000002f qnx4
597 0x68191122 qnx6
598 0x858458f6 ramfs
599 0x52654973 reiserfs
600 0x00007275 romfs
601 0x67596969 rpc_pipefs
602 0x73636673 securityfs
603 0xf97cff8c selinux
604 0x0000517b smb
605 0x534f434b sockfs
606 0x73717368 squashfs
607 0x62656572 sysfs
608 0x012ff7b6 sysv2
609 0x012ff7b5 sysv4
610 0x01021994 tmpfs
611 0x15013346 udf
612 0x00011954 ufs
613 0x54190100 ufs byteswapped
614 0x00009fa2 usbdevfs
615 0x01021997 v9fs
616 0xa501fcf5 vxfs
617 0xabba1974 xenfs
618 0x012ff7b4 xenix
619 0x58465342 xfs
620 0x012fd16d xia
621
622 aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
623 Works like perl's "utime" function (including the special case of
624 $atime and $mtime being undef). Fractional times are supported if
625 the underlying syscalls support them.
626
627 When called with a pathname, uses utimes(2) if available, otherwise
628 utime(2). If called on a file descriptor, uses futimes(2) if
629 available, otherwise returns ENOSYS, so this is not portable.
630
631 Examples:
632
633 # set atime and mtime to current time (basically touch(1)):
634 aio_utime "path", undef, undef;
635 # set atime to current time and mtime to beginning of the epoch:
636 aio_utime "path", time, undef; # undef==0
637
638 aio_chown $fh_or_path, $uid, $gid, $callback->($status)
639 Works like perl's "chown" function, except that "undef" for either
640 $uid or $gid is being interpreted as "do not change" (but -1 can
641 also be used).
642
643 Examples:
644
645 # same as "chown root path" in the shell:
646 aio_chown "path", 0, -1;
647 # same as above:
648 aio_chown "path", 0, undef;
649
650 aio_truncate $fh_or_path, $offset, $callback->($status)
651 Works like truncate(2) or ftruncate(2).
652
653 aio_allocate $fh, $mode, $offset, $len, $callback->($status)
654 Allocates or frees disk space according to the $mode argument. See
655 the linux "fallocate" documentation for details.
656
657 $mode is usually 0 or "IO::AIO::FALLOC_FL_KEEP_SIZE" to allocate
658 space, or "IO::AIO::FALLOC_FL_PUNCH_HOLE |
659 IO::AIO::FALLOC_FL_KEEP_SIZE", to deallocate a file range.
660
661 IO::AIO also supports "FALLOC_FL_COLLAPSE_RANGE", to remove a range
662 (without leaving a hole) and "FALLOC_FL_ZERO_RANGE", to zero a range
663 (see your fallocate(2) manpage).
664
665 The file system block size used by "fallocate" is presumably the
666 "f_bsize" returned by "statvfs".
667
668 If "fallocate" isn't available or cannot be emulated (currently no
669 emulation will be attempted), passes -1 and sets $! to "ENOSYS".
670
671 aio_chmod $fh_or_path, $mode, $callback->($status)
672 Works like perl's "chmod" function.
673
177 aio_unlink $pathname, $callback 674 aio_unlink $pathname, $callback->($status)
178 Asynchronously unlink (delete) a file and call the callback with the 675 Asynchronously unlink (delete) a file and call the callback with the
179 result code. 676 result code.
180 677
678 aio_mknod $pathname, $mode, $dev, $callback->($status)
679 [EXPERIMENTAL]
680
681 Asynchronously create a device node (or fifo). See mknod(2).
682
683 The only (POSIX-) portable way of calling this function is:
684
685 aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
686
687 See "aio_stat" for info about some potentially helpful extra
688 constants and functions.
689
690 aio_link $srcpath, $dstpath, $callback->($status)
691 Asynchronously create a new link to the existing object at $srcpath
692 at the path $dstpath and call the callback with the result code.
693
694 aio_symlink $srcpath, $dstpath, $callback->($status)
695 Asynchronously create a new symbolic link to the existing object at
696 $srcpath at the path $dstpath and call the callback with the result
697 code.
698
699 aio_readlink $pathname, $callback->($link)
700 Asynchronously read the symlink specified by $path and pass it to
701 the callback. If an error occurs, nothing or undef gets passed to
702 the callback.
703
704 aio_realpath $pathname, $callback->($path)
705 Asynchronously make the path absolute and resolve any symlinks in
706 $path. The resulting path only consists of directories (same as
707 Cwd::realpath).
708
709 This request can be used to get the absolute path of the current
710 working directory by passing it a path of . (a single dot).
711
712 aio_rename $srcpath, $dstpath, $callback->($status)
713 Asynchronously rename the object at $srcpath to $dstpath, just as
714 rename(2) and call the callback with the result code.
715
716 On systems that support the AIO::WD working directory abstraction
717 natively, the case "[$wd, "."]" as $srcpath is specialcased -
718 instead of failing, "rename" is called on the absolute path of $wd.
719
720 aio_mkdir $pathname, $mode, $callback->($status)
721 Asynchronously mkdir (create) a directory and call the callback with
722 the result code. $mode will be modified by the umask at the time the
723 request is executed, so do not change your umask.
724
725 aio_rmdir $pathname, $callback->($status)
726 Asynchronously rmdir (delete) a directory and call the callback with
727 the result code.
728
729 On systems that support the AIO::WD working directory abstraction
730 natively, the case "[$wd, "."]" is specialcased - instead of
731 failing, "rmdir" is called on the absolute path of $wd.
732
733 aio_readdir $pathname, $callback->($entries)
734 Unlike the POSIX call of the same name, "aio_readdir" reads an
735 entire directory (i.e. opendir + readdir + closedir). The entries
736 will not be sorted, and will NOT include the "." and ".." entries.
737
738 The callback is passed a single argument which is either "undef" or
739 an array-ref with the filenames.
740
741 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
742 Quite similar to "aio_readdir", but the $flags argument allows one
743 to tune behaviour and output format. In case of an error, $entries
744 will be "undef".
745
746 The flags are a combination of the following constants, ORed
747 together (the flags will also be passed to the callback, possibly
748 modified):
749
750 IO::AIO::READDIR_DENTS
751 When this flag is off, then the callback gets an arrayref
752 consisting of names only (as with "aio_readdir"), otherwise it
753 gets an arrayref with "[$name, $type, $inode]" arrayrefs, each
754 describing a single directory entry in more detail.
755
756 $name is the name of the entry.
757
758 $type is one of the "IO::AIO::DT_xxx" constants:
759
760 "IO::AIO::DT_UNKNOWN", "IO::AIO::DT_FIFO", "IO::AIO::DT_CHR",
761 "IO::AIO::DT_DIR", "IO::AIO::DT_BLK", "IO::AIO::DT_REG",
762 "IO::AIO::DT_LNK", "IO::AIO::DT_SOCK", "IO::AIO::DT_WHT".
763
764 "IO::AIO::DT_UNKNOWN" means just that: readdir does not know. If
765 you need to know, you have to run stat yourself. Also, for speed
766 reasons, the $type scalars are read-only: you can not modify
767 them.
768
769 $inode is the inode number (which might not be exact on systems
770 with 64 bit inode numbers and 32 bit perls). This field has
771 unspecified content on systems that do not deliver the inode
772 information.
773
774 IO::AIO::READDIR_DIRS_FIRST
775 When this flag is set, then the names will be returned in an
776 order where likely directories come first, in optimal stat
777 order. This is useful when you need to quickly find directories,
778 or you want to find all directories while avoiding to stat()
779 each entry.
780
781 If the system returns type information in readdir, then this is
782 used to find directories directly. Otherwise, likely directories
783 are names beginning with ".", or otherwise names with no dots,
784 of which names with short names are tried first.
785
786 IO::AIO::READDIR_STAT_ORDER
787 When this flag is set, then the names will be returned in an
788 order suitable for stat()'ing each one. That is, when you plan
789 to stat() all files in the given directory, then the returned
790 order will likely be fastest.
791
792 If both this flag and "IO::AIO::READDIR_DIRS_FIRST" are
793 specified, then the likely dirs come first, resulting in a less
794 optimal stat order.
795
796 IO::AIO::READDIR_FOUND_UNKNOWN
797 This flag should not be set when calling "aio_readdirx".
798 Instead, it is being set by "aio_readdirx", when any of the
799 $type's found were "IO::AIO::DT_UNKNOWN". The absence of this
800 flag therefore indicates that all $type's are known, which can
801 be used to speed up some algorithms.
802
803 aio_load $pathname, $data, $callback->($status)
804 This is a composite request that tries to fully load the given file
805 into memory. Status is the same as with aio_read.
806
807 aio_copy $srcpath, $dstpath, $callback->($status)
808 Try to copy the *file* (directories not supported as either source
809 or destination) from $srcpath to $dstpath and call the callback with
810 a status of 0 (ok) or -1 (error, see $!).
811
812 This is a composite request that creates the destination file with
813 mode 0200 and copies the contents of the source file into it using
814 "aio_sendfile", followed by restoring atime, mtime, access mode and
815 uid/gid, in that order.
816
817 If an error occurs, the partial destination file will be unlinked,
818 if possible, except when setting atime, mtime, access mode and
819 uid/gid, where errors are being ignored.
820
821 aio_move $srcpath, $dstpath, $callback->($status)
822 Try to move the *file* (directories not supported as either source
823 or destination) from $srcpath to $dstpath and call the callback with
824 a status of 0 (ok) or -1 (error, see $!).
825
826 This is a composite request that tries to rename(2) the file first;
827 if rename fails with "EXDEV", it copies the file with "aio_copy"
828 and, if that is successful, unlinks the $srcpath.
829
830 aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
831 Scans a directory (similar to "aio_readdir") but additionally tries
832 to efficiently separate the entries of directory $path into two sets
833 of names, directories you can recurse into (directories), and ones
834 you cannot recurse into (everything else, including symlinks to
835 directories).
836
837 "aio_scandir" is a composite request that creates of many sub
838 requests_ $maxreq specifies the maximum number of outstanding aio
839 requests that this function generates. If it is "<= 0", then a
840 suitable default will be chosen (currently 4).
841
842 On error, the callback is called without arguments, otherwise it
843 receives two array-refs with path-relative entry names.
844
845 Example:
846
847 aio_scandir $dir, 0, sub {
848 my ($dirs, $nondirs) = @_;
849 print "real directories: @$dirs\n";
850 print "everything else: @$nondirs\n";
851 };
852
853 Implementation notes.
854
855 The "aio_readdir" cannot be avoided, but "stat()"'ing every entry
856 can.
857
858 If readdir returns file type information, then this is used directly
859 to find directories.
860
861 Otherwise, after reading the directory, the modification time, size
862 etc. of the directory before and after the readdir is checked, and
863 if they match (and isn't the current time), the link count will be
864 used to decide how many entries are directories (if >= 2).
865 Otherwise, no knowledge of the number of subdirectories will be
866 assumed.
867
868 Then entries will be sorted into likely directories a non-initial
869 dot currently) and likely non-directories (see "aio_readdirx"). Then
870 every entry plus an appended "/." will be "stat"'ed, likely
871 directories first, in order of their inode numbers. If that
872 succeeds, it assumes that the entry is a directory or a symlink to
873 directory (which will be checked separately). This is often faster
874 than stat'ing the entry itself because filesystems might detect the
875 type of the entry without reading the inode data (e.g. ext2fs
876 filetype feature), even on systems that cannot return the filetype
877 information on readdir.
878
879 If the known number of directories (link count - 2) has been
880 reached, the rest of the entries is assumed to be non-directories.
881
882 This only works with certainty on POSIX (= UNIX) filesystems, which
883 fortunately are the vast majority of filesystems around.
884
885 It will also likely work on non-POSIX filesystems with reduced
886 efficiency as those tend to return 0 or 1 as link counts, which
887 disables the directory counting heuristic.
888
889 aio_rmtree $pathname, $callback->($status)
890 Delete a directory tree starting (and including) $path, return the
891 status of the final "rmdir" only. This is a composite request that
892 uses "aio_scandir" to recurse into and rmdir directories, and unlink
893 everything else.
894
895 aio_fcntl $fh, $cmd, $arg, $callback->($status)
896 aio_ioctl $fh, $request, $buf, $callback->($status)
897 These work just like the "fcntl" and "ioctl" built-in functions,
898 except they execute asynchronously and pass the return value to the
899 callback.
900
901 Both calls can be used for a lot of things, some of which make more
902 sense to run asynchronously in their own thread, while some others
903 make less sense. For example, calls that block waiting for external
904 events, such as locking, will also lock down an I/O thread while it
905 is waiting, which can deadlock the whole I/O system. At the same
906 time, there might be no alternative to using a thread to wait.
907
908 So in general, you should only use these calls for things that do
909 (filesystem) I/O, not for things that wait for other events
910 (network, other processes), although if you are careful and know
911 what you are doing, you still can.
912
913 aio_sync $callback->($status)
914 Asynchronously call sync and call the callback when finished.
915
181 aio_fsync $fh, $callback 916 aio_fsync $fh, $callback->($status)
182 Asynchronously call fsync on the given filehandle and call the 917 Asynchronously call fsync on the given filehandle and call the
183 callback with the fsync result code. 918 callback with the fsync result code.
184 919
185 aio_fdatasync $fh, $callback 920 aio_fdatasync $fh, $callback->($status)
186 Asynchronously call fdatasync on the given filehandle and call the 921 Asynchronously call fdatasync on the given filehandle and call the
187 callback with the fdatasync result code. 922 callback with the fdatasync result code.
188 923
189BUGS 924 If this call isn't available because your OS lacks it or it couldn't
190 - could be optimized to use more semaphores instead of filehandles. 925 be detected, it will be emulated by calling "fsync" instead.
926
927 aio_syncfs $fh, $callback->($status)
928 Asynchronously call the syncfs syscall to sync the filesystem
929 associated to the given filehandle and call the callback with the
930 syncfs result code. If syncfs is not available, calls sync(), but
931 returns -1 and sets errno to "ENOSYS" nevertheless.
932
933 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
934 Sync the data portion of the file specified by $offset and $length
935 to disk (but NOT the metadata), by calling the Linux-specific
936 sync_file_range call. If sync_file_range is not available or it
937 returns ENOSYS, then fdatasync or fsync is being substituted.
938
939 $flags can be a combination of
940 "IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE",
941 "IO::AIO::SYNC_FILE_RANGE_WRITE" and
942 "IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER": refer to the sync_file_range
943 manpage for details.
944
945 aio_pathsync $pathname, $callback->($status)
946 This request tries to open, fsync and close the given path. This is
947 a composite request intended to sync directories after directory
948 operations (E.g. rename). This might not work on all operating
949 systems or have any specific effect, but usually it makes sure that
950 directory changes get written to disc. It works for anything that
951 can be opened for read-only, not just directories.
952
953 Future versions of this function might fall back to other methods
954 when "fsync" on the directory fails (such as calling "sync").
955
956 Passes 0 when everything went ok, and -1 on error.
957
958 aio_msync $scalar, $offset = 0, $length = undef, flags = 0,
959 $callback->($status)
960 This is a rather advanced IO::AIO call, which only works on
961 mmap(2)ed scalars (see the "IO::AIO::mmap" function, although it
962 also works on data scalars managed by the Sys::Mmap or Mmap modules,
963 note that the scalar must only be modified in-place while an aio
964 operation is pending on it).
965
966 It calls the "msync" function of your OS, if available, with the
967 memory area starting at $offset in the string and ending $length
968 bytes later. If $length is negative, counts from the end, and if
969 $length is "undef", then it goes till the end of the string. The
970 flags can be a combination of "IO::AIO::MS_ASYNC",
971 "IO::AIO::MS_INVALIDATE" and "IO::AIO::MS_SYNC".
972
973 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0,
974 $callback->($status)
975 This is a rather advanced IO::AIO call, which works best on
976 mmap(2)ed scalars.
977
978 It touches (reads or writes) all memory pages in the specified range
979 inside the scalar. All caveats and parameters are the same as for
980 "aio_msync", above, except for flags, which must be either 0 (which
981 reads all pages and ensures they are instantiated) or
982 "IO::AIO::MT_MODIFY", which modifies the memory pages (by reading
983 and writing an octet from it, which dirties the page).
984
985 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
986 This is a rather advanced IO::AIO call, which works best on
987 mmap(2)ed scalars.
988
989 It reads in all the pages of the underlying storage into memory (if
990 any) and locks them, so they are not getting swapped/paged out or
991 removed.
992
993 If $length is undefined, then the scalar will be locked till the
994 end.
995
996 On systems that do not implement "mlock", this function returns -1
997 and sets errno to "ENOSYS".
998
999 Note that the corresponding "munlock" is synchronous and is
1000 documented under "MISCELLANEOUS FUNCTIONS".
1001
1002 Example: open a file, mmap and mlock it - both will be undone when
1003 $data gets destroyed.
1004
1005 open my $fh, "<", $path or die "$path: $!";
1006 my $data;
1007 IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
1008 aio_mlock $data; # mlock in background
1009
1010 aio_mlockall $flags, $callback->($status)
1011 Calls the "mlockall" function with the given $flags (a combination
1012 of "IO::AIO::MCL_CURRENT" and "IO::AIO::MCL_FUTURE").
1013
1014 On systems that do not implement "mlockall", this function returns
1015 -1 and sets errno to "ENOSYS".
1016
1017 Note that the corresponding "munlockall" is synchronous and is
1018 documented under "MISCELLANEOUS FUNCTIONS".
1019
1020 Example: asynchronously lock all current and future pages into
1021 memory.
1022
1023 aio_mlockall IO::AIO::MCL_FUTURE;
1024
1025 aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
1026 Queries the extents of the given file (by calling the Linux "FIEMAP"
1027 ioctl, see <http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for
1028 details). If the ioctl is not available on your OS, then this
1029 request will fail with "ENOSYS".
1030
1031 $start is the starting offset to query extents for, $length is the
1032 size of the range to query - if it is "undef", then the whole file
1033 will be queried.
1034
1035 $flags is a combination of flags ("IO::AIO::FIEMAP_FLAG_SYNC" or
1036 "IO::AIO::FIEMAP_FLAG_XATTR" - "IO::AIO::FIEMAP_FLAGS_COMPAT" is
1037 also exported), and is normally 0 or "IO::AIO::FIEMAP_FLAG_SYNC" to
1038 query the data portion.
1039
1040 $count is the maximum number of extent records to return. If it is
1041 "undef", then IO::AIO queries all extents of the range. As a very
1042 special case, if it is 0, then the callback receives the number of
1043 extents instead of the extents themselves (which is unreliable, see
1044 below).
1045
1046 If an error occurs, the callback receives no arguments. The special
1047 "errno" value "IO::AIO::EBADR" is available to test for flag errors.
1048
1049 Otherwise, the callback receives an array reference with extent
1050 structures. Each extent structure is an array reference itself, with
1051 the following members:
1052
1053 [$logical, $physical, $length, $flags]
1054
1055 Flags is any combination of the following flag values (typically
1056 either 0 or "IO::AIO::FIEMAP_EXTENT_LAST" (1)):
1057
1058 "IO::AIO::FIEMAP_EXTENT_LAST", "IO::AIO::FIEMAP_EXTENT_UNKNOWN",
1059 "IO::AIO::FIEMAP_EXTENT_DELALLOC", "IO::AIO::FIEMAP_EXTENT_ENCODED",
1060 "IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED",
1061 "IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED",
1062 "IO::AIO::FIEMAP_EXTENT_DATA_INLINE",
1063 "IO::AIO::FIEMAP_EXTENT_DATA_TAIL",
1064 "IO::AIO::FIEMAP_EXTENT_UNWRITTEN", "IO::AIO::FIEMAP_EXTENT_MERGED"
1065 or "IO::AIO::FIEMAP_EXTENT_SHARED".
1066
1067 At the time of this writing (Linux 3.2), this requets is unreliable
1068 unless $count is "undef", as the kernel has all sorts of bugs
1069 preventing it to return all extents of a range for files with large
1070 number of extents. The code works around all these issues if $count
1071 is undef.
1072
1073 aio_group $callback->(...)
1074 This is a very special aio request: Instead of doing something, it
1075 is a container for other aio requests, which is useful if you want
1076 to bundle many requests into a single, composite, request with a
1077 definite callback and the ability to cancel the whole request with
1078 its subrequests.
1079
1080 Returns an object of class IO::AIO::GRP. See its documentation below
1081 for more info.
1082
1083 Example:
1084
1085 my $grp = aio_group sub {
1086 print "all stats done\n";
1087 };
1088
1089 add $grp
1090 (aio_stat ...),
1091 (aio_stat ...),
1092 ...;
1093
1094 aio_nop $callback->()
1095 This is a special request - it does nothing in itself and is only
1096 used for side effects, such as when you want to add a dummy request
1097 to a group so that finishing the requests in the group depends on
1098 executing the given code.
1099
1100 While this request does nothing, it still goes through the execution
1101 phase and still requires a worker thread. Thus, the callback will
1102 not be executed immediately but only after other requests in the
1103 queue have entered their execution phase. This can be used to
1104 measure request latency.
1105
1106 IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
1107 Mainly used for debugging and benchmarking, this aio request puts
1108 one of the request workers to sleep for the given time.
1109
1110 While it is theoretically handy to have simple I/O scheduling
1111 requests like sleep and file handle readable/writable, the overhead
1112 this creates is immense (it blocks a thread for a long time) so do
1113 not use this function except to put your application under
1114 artificial I/O pressure.
1115
1116 IO::AIO::WD - multiple working directories
1117 Your process only has one current working directory, which is used by
1118 all threads. This makes it hard to use relative paths (some other
1119 component could call "chdir" at any time, and it is hard to control when
1120 the path will be used by IO::AIO).
1121
1122 One solution for this is to always use absolute paths. This usually
1123 works, but can be quite slow (the kernel has to walk the whole path on
1124 every access), and can also be a hassle to implement.
1125
1126 Newer POSIX systems have a number of functions (openat, fdopendir,
1127 futimensat and so on) that make it possible to specify working
1128 directories per operation.
1129
1130 For portability, and because the clowns who "designed", or shall I
1131 write, perpetrated this new interface were obviously half-drunk, this
1132 abstraction cannot be perfect, though.
1133
1134 IO::AIO allows you to convert directory paths into a so-called
1135 IO::AIO::WD object. This object stores the canonicalised, absolute
1136 version of the path, and on systems that allow it, also a directory file
1137 descriptor.
1138
1139 Everywhere where a pathname is accepted by IO::AIO (e.g. in "aio_stat"
1140 or "aio_unlink"), one can specify an array reference with an IO::AIO::WD
1141 object and a pathname instead (or the IO::AIO::WD object alone, which
1142 gets interpreted as "[$wd, "."]"). If the pathname is absolute, the
1143 IO::AIO::WD object is ignored, otherwise the pathname is resolved
1144 relative to that IO::AIO::WD object.
1145
1146 For example, to get a wd object for /etc and then stat passwd inside,
1147 you would write:
1148
1149 aio_wd "/etc", sub {
1150 my $etcdir = shift;
1151
1152 # although $etcdir can be undef on error, there is generally no reason
1153 # to check for errors here, as aio_stat will fail with ENOENT
1154 # when $etcdir is undef.
1155
1156 aio_stat [$etcdir, "passwd"], sub {
1157 # yay
1158 };
1159 };
1160
1161 The fact that "aio_wd" is a request and not a normal function shows that
1162 creating an IO::AIO::WD object is itself a potentially blocking
1163 operation, which is why it is done asynchronously.
1164
1165 To stat the directory obtained with "aio_wd" above, one could write
1166 either of the following three request calls:
1167
1168 aio_lstat "/etc" , sub { ... # pathname as normal string
1169 aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
1170 aio_lstat $wd , sub { ... # shorthand for the previous
1171
1172 As with normal pathnames, IO::AIO keeps a copy of the working directory
1173 object and the pathname string, so you could write the following without
1174 causing any issues due to $path getting reused:
1175
1176 my $path = [$wd, undef];
1177
1178 for my $name (qw(abc def ghi)) {
1179 $path->[1] = $name;
1180 aio_stat $path, sub {
1181 # ...
1182 };
1183 }
1184
1185 There are some caveats: when directories get renamed (or deleted), the
1186 pathname string doesn't change, so will point to the new directory (or
1187 nowhere at all), while the directory fd, if available on the system,
1188 will still point to the original directory. Most functions accepting a
1189 pathname will use the directory fd on newer systems, and the string on
1190 older systems. Some functions (such as realpath) will always rely on the
1191 string form of the pathname.
1192
1193 So this functionality is mainly useful to get some protection against
1194 "chdir", to easily get an absolute path out of a relative path for
1195 future reference, and to speed up doing many operations in the same
1196 directory (e.g. when stat'ing all files in a directory).
1197
1198 The following functions implement this working directory abstraction:
1199
1200 aio_wd $pathname, $callback->($wd)
1201 Asynchonously canonicalise the given pathname and convert it to an
1202 IO::AIO::WD object representing it. If possible and supported on the
1203 system, also open a directory fd to speed up pathname resolution
1204 relative to this working directory.
1205
1206 If something goes wrong, then "undef" is passwd to the callback
1207 instead of a working directory object and $! is set appropriately.
1208 Since passing "undef" as working directory component of a pathname
1209 fails the request with "ENOENT", there is often no need for error
1210 checking in the "aio_wd" callback, as future requests using the
1211 value will fail in the expected way.
1212
1213 IO::AIO::CWD
1214 This is a compiletime constant (object) that represents the process
1215 current working directory.
1216
1217 Specifying this object as working directory object for a pathname is
1218 as if the pathname would be specified directly, without a directory
1219 object. For example, these calls are functionally identical:
1220
1221 aio_stat "somefile", sub { ... };
1222 aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
1223
1224 To recover the path associated with an IO::AIO::WD object, you can use
1225 "aio_realpath":
1226
1227 aio_realpath $wd, sub {
1228 warn "path is $_[0]\n";
1229 };
1230
1231 Currently, "aio_statvfs" always, and "aio_rename" and "aio_rmdir"
1232 sometimes, fall back to using an absolue path.
1233
1234 IO::AIO::REQ CLASS
1235 All non-aggregate "aio_*" functions return an object of this class when
1236 called in non-void context.
1237
1238 cancel $req
1239 Cancels the request, if possible. Has the effect of skipping
1240 execution when entering the execute state and skipping calling the
1241 callback when entering the the result state, but will leave the
1242 request otherwise untouched (with the exception of readdir). That
1243 means that requests that currently execute will not be stopped and
1244 resources held by the request will not be freed prematurely.
1245
1246 cb $req $callback->(...)
1247 Replace (or simply set) the callback registered to the request.
1248
1249 IO::AIO::GRP CLASS
1250 This class is a subclass of IO::AIO::REQ, so all its methods apply to
1251 objects of this class, too.
1252
1253 A IO::AIO::GRP object is a special request that can contain multiple
1254 other aio requests.
1255
1256 You create one by calling the "aio_group" constructing function with a
1257 callback that will be called when all contained requests have entered
1258 the "done" state:
1259
1260 my $grp = aio_group sub {
1261 print "all requests are done\n";
1262 };
1263
1264 You add requests by calling the "add" method with one or more
1265 "IO::AIO::REQ" objects:
1266
1267 $grp->add (aio_unlink "...");
1268
1269 add $grp aio_stat "...", sub {
1270 $_[0] or return $grp->result ("error");
1271
1272 # add another request dynamically, if first succeeded
1273 add $grp aio_open "...", sub {
1274 $grp->result ("ok");
1275 };
1276 };
1277
1278 This makes it very easy to create composite requests (see the source of
1279 "aio_move" for an application) that work and feel like simple requests.
1280
1281 * The IO::AIO::GRP objects will be cleaned up during calls to
1282 "IO::AIO::poll_cb", just like any other request.
1283
1284 * They can be canceled like any other request. Canceling will cancel
1285 not only the request itself, but also all requests it contains.
1286
1287 * They can also can also be added to other IO::AIO::GRP objects.
1288
1289 * You must not add requests to a group from within the group callback
1290 (or any later time).
1291
1292 Their lifetime, simplified, looks like this: when they are empty, they
1293 will finish very quickly. If they contain only requests that are in the
1294 "done" state, they will also finish. Otherwise they will continue to
1295 exist.
1296
1297 That means after creating a group you have some time to add requests
1298 (precisely before the callback has been invoked, which is only done
1299 within the "poll_cb"). And in the callbacks of those requests, you can
1300 add further requests to the group. And only when all those requests have
1301 finished will the the group itself finish.
1302
1303 add $grp ...
1304 $grp->add (...)
1305 Add one or more requests to the group. Any type of IO::AIO::REQ can
1306 be added, including other groups, as long as you do not create
1307 circular dependencies.
1308
1309 Returns all its arguments.
1310
1311 $grp->cancel_subs
1312 Cancel all subrequests and clears any feeder, but not the group
1313 request itself. Useful when you queued a lot of events but got a
1314 result early.
1315
1316 The group request will finish normally (you cannot add requests to
1317 the group).
1318
1319 $grp->result (...)
1320 Set the result value(s) that will be passed to the group callback
1321 when all subrequests have finished and set the groups errno to the
1322 current value of errno (just like calling "errno" without an error
1323 number). By default, no argument will be passed and errno is zero.
1324
1325 $grp->errno ([$errno])
1326 Sets the group errno value to $errno, or the current value of errno
1327 when the argument is missing.
1328
1329 Every aio request has an associated errno value that is restored
1330 when the callback is invoked. This method lets you change this value
1331 from its default (0).
1332
1333 Calling "result" will also set errno, so make sure you either set $!
1334 before the call to "result", or call c<errno> after it.
1335
1336 feed $grp $callback->($grp)
1337 Sets a feeder/generator on this group: every group can have an
1338 attached generator that generates requests if idle. The idea behind
1339 this is that, although you could just queue as many requests as you
1340 want in a group, this might starve other requests for a potentially
1341 long time. For example, "aio_scandir" might generate hundreds of
1342 thousands of "aio_stat" requests, delaying any later requests for a
1343 long time.
1344
1345 To avoid this, and allow incremental generation of requests, you can
1346 instead a group and set a feeder on it that generates those
1347 requests. The feed callback will be called whenever there are few
1348 enough (see "limit", below) requests active in the group itself and
1349 is expected to queue more requests.
1350
1351 The feed callback can queue as many requests as it likes (i.e. "add"
1352 does not impose any limits).
1353
1354 If the feed does not queue more requests when called, it will be
1355 automatically removed from the group.
1356
1357 If the feed limit is 0 when this method is called, it will be set to
1358 2 automatically.
1359
1360 Example:
1361
1362 # stat all files in @files, but only ever use four aio requests concurrently:
1363
1364 my $grp = aio_group sub { print "finished\n" };
1365 limit $grp 4;
1366 feed $grp sub {
1367 my $file = pop @files
1368 or return;
1369
1370 add $grp aio_stat $file, sub { ... };
1371 };
1372
1373 limit $grp $num
1374 Sets the feeder limit for the group: The feeder will be called
1375 whenever the group contains less than this many requests.
1376
1377 Setting the limit to 0 will pause the feeding process.
1378
1379 The default value for the limit is 0, but note that setting a feeder
1380 automatically bumps it up to 2.
1381
1382 SUPPORT FUNCTIONS
1383 EVENT PROCESSING AND EVENT LOOP INTEGRATION
1384 $fileno = IO::AIO::poll_fileno
1385 Return the *request result pipe file descriptor*. This filehandle
1386 must be polled for reading by some mechanism outside this module
1387 (e.g. EV, Glib, select and so on, see below or the SYNOPSIS). If the
1388 pipe becomes readable you have to call "poll_cb" to check the
1389 results.
1390
1391 See "poll_cb" for an example.
1392
1393 IO::AIO::poll_cb
1394 Process some requests that have reached the result phase (i.e. they
1395 have been executed but the results are not yet reported). You have
1396 to call this "regularly" to finish outstanding requests.
1397
1398 Returns 0 if all events could be processed (or there were no events
1399 to process), or -1 if it returned earlier for whatever reason.
1400 Returns immediately when no events are outstanding. The amount of
1401 events processed depends on the settings of "IO::AIO::max_poll_req",
1402 "IO::AIO::max_poll_time" and "IO::AIO::max_outstanding".
1403
1404 If not all requests were processed for whatever reason, the poll
1405 file descriptor will still be ready when "poll_cb" returns, so
1406 normally you don't have to do anything special to have it called
1407 later.
1408
1409 Apart from calling "IO::AIO::poll_cb" when the event filehandle
1410 becomes ready, it can be beneficial to call this function from loops
1411 which submit a lot of requests, to make sure the results get
1412 processed when they become available and not just when the loop is
1413 finished and the event loop takes over again. This function returns
1414 very fast when there are no outstanding requests.
1415
1416 Example: Install an Event watcher that automatically calls
1417 IO::AIO::poll_cb with high priority (more examples can be found in
1418 the SYNOPSIS section, at the top of this document):
1419
1420 Event->io (fd => IO::AIO::poll_fileno,
1421 poll => 'r', async => 1,
1422 cb => \&IO::AIO::poll_cb);
1423
1424 IO::AIO::poll_wait
1425 Wait until either at least one request is in the result phase or no
1426 requests are outstanding anymore.
1427
1428 This is useful if you want to synchronously wait for some requests
1429 to become ready, without actually handling them.
1430
1431 See "nreqs" for an example.
1432
1433 IO::AIO::poll
1434 Waits until some requests have been handled.
1435
1436 Returns the number of requests processed, but is otherwise strictly
1437 equivalent to:
1438
1439 IO::AIO::poll_wait, IO::AIO::poll_cb
1440
1441 IO::AIO::flush
1442 Wait till all outstanding AIO requests have been handled.
1443
1444 Strictly equivalent to:
1445
1446 IO::AIO::poll_wait, IO::AIO::poll_cb
1447 while IO::AIO::nreqs;
1448
1449 IO::AIO::max_poll_reqs $nreqs
1450 IO::AIO::max_poll_time $seconds
1451 These set the maximum number of requests (default 0, meaning
1452 infinity) that are being processed by "IO::AIO::poll_cb" in one
1453 call, respectively the maximum amount of time (default 0, meaning
1454 infinity) spent in "IO::AIO::poll_cb" to process requests (more
1455 correctly the mininum amount of time "poll_cb" is allowed to use).
1456
1457 Setting "max_poll_time" to a non-zero value creates an overhead of
1458 one syscall per request processed, which is not normally a problem
1459 unless your callbacks are really really fast or your OS is really
1460 really slow (I am not mentioning Solaris here). Using
1461 "max_poll_reqs" incurs no overhead.
1462
1463 Setting these is useful if you want to ensure some level of
1464 interactiveness when perl is not fast enough to process all requests
1465 in time.
1466
1467 For interactive programs, values such as 0.01 to 0.1 should be fine.
1468
1469 Example: Install an Event watcher that automatically calls
1470 IO::AIO::poll_cb with low priority, to ensure that other parts of
1471 the program get the CPU sometimes even under high AIO load.
1472
1473 # try not to spend much more than 0.1s in poll_cb
1474 IO::AIO::max_poll_time 0.1;
1475
1476 # use a low priority so other tasks have priority
1477 Event->io (fd => IO::AIO::poll_fileno,
1478 poll => 'r', nice => 1,
1479 cb => &IO::AIO::poll_cb);
1480
1481 CONTROLLING THE NUMBER OF THREADS
1482 IO::AIO::min_parallel $nthreads
1483 Set the minimum number of AIO threads to $nthreads. The current
1484 default is 8, which means eight asynchronous operations can execute
1485 concurrently at any one time (the number of outstanding requests,
1486 however, is unlimited).
1487
1488 IO::AIO starts threads only on demand, when an AIO request is queued
1489 and no free thread exists. Please note that queueing up a hundred
1490 requests can create demand for a hundred threads, even if it turns
1491 out that everything is in the cache and could have been processed
1492 faster by a single thread.
1493
1494 It is recommended to keep the number of threads relatively low, as
1495 some Linux kernel versions will scale negatively with the number of
1496 threads (higher parallelity => MUCH higher latency). With current
1497 Linux 2.6 versions, 4-32 threads should be fine.
1498
1499 Under most circumstances you don't need to call this function, as
1500 the module selects a default that is suitable for low to moderate
1501 load.
1502
1503 IO::AIO::max_parallel $nthreads
1504 Sets the maximum number of AIO threads to $nthreads. If more than
1505 the specified number of threads are currently running, this function
1506 kills them. This function blocks until the limit is reached.
1507
1508 While $nthreads are zero, aio requests get queued but not executed
1509 until the number of threads has been increased again.
1510
1511 This module automatically runs "max_parallel 0" at program end, to
1512 ensure that all threads are killed and that there are no outstanding
1513 requests.
1514
1515 Under normal circumstances you don't need to call this function.
1516
1517 IO::AIO::max_idle $nthreads
1518 Limit the number of threads (default: 4) that are allowed to idle
1519 (i.e., threads that did not get a request to process within the idle
1520 timeout (default: 10 seconds). That means if a thread becomes idle
1521 while $nthreads other threads are also idle, it will free its
1522 resources and exit.
1523
1524 This is useful when you allow a large number of threads (e.g. 100 or
1525 1000) to allow for extremely high load situations, but want to free
1526 resources under normal circumstances (1000 threads can easily
1527 consume 30MB of RAM).
1528
1529 The default is probably ok in most situations, especially if thread
1530 creation is fast. If thread creation is very slow on your system you
1531 might want to use larger values.
1532
1533 IO::AIO::idle_timeout $seconds
1534 Sets the minimum idle timeout (default 10) after which worker
1535 threads are allowed to exit. SEe "IO::AIO::max_idle".
1536
1537 IO::AIO::max_outstanding $maxreqs
1538 Sets the maximum number of outstanding requests to $nreqs. If you do
1539 queue up more than this number of requests, the next call to
1540 "IO::AIO::poll_cb" (and other functions calling "poll_cb", such as
1541 "IO::AIO::flush" or "IO::AIO::poll") will block until the limit is
1542 no longer exceeded.
1543
1544 In other words, this setting does not enforce a queue limit, but can
1545 be used to make poll functions block if the limit is exceeded.
1546
1547 This is a very bad function to use in interactive programs because
1548 it blocks, and a bad way to reduce concurrency because it is
1549 inexact: Better use an "aio_group" together with a feed callback.
1550
1551 Its main use is in scripts without an event loop - when you want to
1552 stat a lot of files, you can write somehting like this:
1553
1554 IO::AIO::max_outstanding 32;
1555
1556 for my $path (...) {
1557 aio_stat $path , ...;
1558 IO::AIO::poll_cb;
1559 }
1560
1561 IO::AIO::flush;
1562
1563 The call to "poll_cb" inside the loop will normally return
1564 instantly, but as soon as more thna 32 reqeusts are in-flight, it
1565 will block until some requests have been handled. This keeps the
1566 loop from pushing a large number of "aio_stat" requests onto the
1567 queue.
1568
1569 The default value for "max_outstanding" is very large, so there is
1570 no practical limit on the number of outstanding requests.
1571
1572 STATISTICAL INFORMATION
1573 IO::AIO::nreqs
1574 Returns the number of requests currently in the ready, execute or
1575 pending states (i.e. for which their callback has not been invoked
1576 yet).
1577
1578 Example: wait till there are no outstanding requests anymore:
1579
1580 IO::AIO::poll_wait, IO::AIO::poll_cb
1581 while IO::AIO::nreqs;
1582
1583 IO::AIO::nready
1584 Returns the number of requests currently in the ready state (not yet
1585 executed).
1586
1587 IO::AIO::npending
1588 Returns the number of requests currently in the pending state
1589 (executed, but not yet processed by poll_cb).
1590
1591 MISCELLANEOUS FUNCTIONS
1592 IO::AIO implements some functions that are useful when you want to use
1593 some "Advanced I/O" function not available to in Perl, without going the
1594 "Asynchronous I/O" route. Many of these have an asynchronous "aio_*"
1595 counterpart.
1596
1597 IO::AIO::sendfile $ofh, $ifh, $offset, $count
1598 Calls the "eio_sendfile_sync" function, which is like
1599 "aio_sendfile", but is blocking (this makes most sense if you know
1600 the input data is likely cached already and the output filehandle is
1601 set to non-blocking operations).
1602
1603 Returns the number of bytes copied, or -1 on error.
1604
1605 IO::AIO::fadvise $fh, $offset, $len, $advice
1606 Simply calls the "posix_fadvise" function (see its manpage for
1607 details). The following advice constants are available:
1608 "IO::AIO::FADV_NORMAL", "IO::AIO::FADV_SEQUENTIAL",
1609 "IO::AIO::FADV_RANDOM", "IO::AIO::FADV_NOREUSE",
1610 "IO::AIO::FADV_WILLNEED", "IO::AIO::FADV_DONTNEED".
1611
1612 On systems that do not implement "posix_fadvise", this function
1613 returns ENOSYS, otherwise the return value of "posix_fadvise".
1614
1615 IO::AIO::madvise $scalar, $offset, $len, $advice
1616 Simply calls the "posix_madvise" function (see its manpage for
1617 details). The following advice constants are available:
1618 "IO::AIO::MADV_NORMAL", "IO::AIO::MADV_SEQUENTIAL",
1619 "IO::AIO::MADV_RANDOM", "IO::AIO::MADV_WILLNEED",
1620 "IO::AIO::MADV_DONTNEED".
1621
1622 On systems that do not implement "posix_madvise", this function
1623 returns ENOSYS, otherwise the return value of "posix_madvise".
1624
1625 IO::AIO::mprotect $scalar, $offset, $len, $protect
1626 Simply calls the "mprotect" function on the preferably AIO::mmap'ed
1627 $scalar (see its manpage for details). The following protect
1628 constants are available: "IO::AIO::PROT_NONE", "IO::AIO::PROT_READ",
1629 "IO::AIO::PROT_WRITE", "IO::AIO::PROT_EXEC".
1630
1631 On systems that do not implement "mprotect", this function returns
1632 ENOSYS, otherwise the return value of "mprotect".
1633
1634 IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
1635 Memory-maps a file (or anonymous memory range) and attaches it to
1636 the given $scalar, which will act like a string scalar. Returns true
1637 on success, and false otherwise.
1638
1639 The only operations allowed on the scalar are "substr"/"vec" that
1640 don't change the string length, and most read-only operations such
1641 as copying it or searching it with regexes and so on.
1642
1643 Anything else is unsafe and will, at best, result in memory leaks.
1644
1645 The memory map associated with the $scalar is automatically removed
1646 when the $scalar is destroyed, or when the "IO::AIO::mmap" or
1647 "IO::AIO::munmap" functions are called.
1648
1649 This calls the "mmap"(2) function internally. See your system's
1650 manual page for details on the $length, $prot and $flags parameters.
1651
1652 The $length must be larger than zero and smaller than the actual
1653 filesize.
1654
1655 $prot is a combination of "IO::AIO::PROT_NONE",
1656 "IO::AIO::PROT_EXEC", "IO::AIO::PROT_READ" and/or
1657 "IO::AIO::PROT_WRITE",
1658
1659 $flags can be a combination of "IO::AIO::MAP_SHARED" or
1660 "IO::AIO::MAP_PRIVATE", or a number of system-specific flags (when
1661 not available, the are 0): "IO::AIO::MAP_ANONYMOUS" (which is set to
1662 "MAP_ANON" if your system only provides this constant),
1663 "IO::AIO::MAP_LOCKED", "IO::AIO::MAP_NORESERVE",
1664 "IO::AIO::MAP_POPULATE", "IO::AIO::MAP_NONBLOCK",
1665 "IO::AIO::MAP_FIXED", "IO::AIO::MAP_GROWSDOWN",
1666 "IO::AIO::MAP_32BIT", "IO::AIO::MAP_HUGETLB" or
1667 "IO::AIO::MAP_STACK".
1668
1669 If $fh is "undef", then a file descriptor of -1 is passed.
1670
1671 $offset is the offset from the start of the file - it generally must
1672 be a multiple of "IO::AIO::PAGESIZE" and defaults to 0.
1673
1674 Example:
1675
1676 use Digest::MD5;
1677 use IO::AIO;
1678
1679 open my $fh, "<verybigfile"
1680 or die "$!";
1681
1682 IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
1683 or die "verybigfile: $!";
1684
1685 my $fast_md5 = md5 $data;
1686
1687 IO::AIO::munmap $scalar
1688 Removes a previous mmap and undefines the $scalar.
1689
1690 IO::AIO::munlock $scalar, $offset = 0, $length = undef
1691 Calls the "munlock" function, undoing the effects of a previous
1692 "aio_mlock" call (see its description for details).
1693
1694 IO::AIO::munlockall
1695 Calls the "munlockall" function.
1696
1697 On systems that do not implement "munlockall", this function returns
1698 ENOSYS, otherwise the return value of "munlockall".
1699
1700 IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
1701 Calls the GNU/Linux splice(2) syscall, if available. If $r_off or
1702 $w_off are "undef", then "NULL" is passed for these, otherwise they
1703 should be the file offset.
1704
1705 $r_fh and $w_fh should not refer to the same file, as splice might
1706 silently corrupt the data in this case.
1707
1708 The following symbol flag values are available:
1709 "IO::AIO::SPLICE_F_MOVE", "IO::AIO::SPLICE_F_NONBLOCK",
1710 "IO::AIO::SPLICE_F_MORE" and "IO::AIO::SPLICE_F_GIFT".
1711
1712 See the splice(2) manpage for details.
1713
1714 IO::AIO::tee $r_fh, $w_fh, $length, $flags
1715 Calls the GNU/Linux tee(2) syscall, see its manpage and the
1716 description for "IO::AIO::splice" above for details.
1717
1718 $actual_size = IO::AIO::pipesize $r_fh[, $new_size]
1719 Attempts to query or change the pipe buffer size. Obviously works
1720 only on pipes, and currently works only on GNU/Linux systems, and
1721 fails with -1/"ENOSYS" everywhere else. If anybody knows how to
1722 influence pipe buffer size on other systems, drop me a note.
1723
1724 ($rfh, $wfh) = IO::AIO::pipe2 [$flags]
1725 This is a direct interface to the Linux pipe2(2) system call. If
1726 $flags is missing or 0, then this should be the same as a call to
1727 perl's built-in "pipe" function and create a new pipe, and works on
1728 systems that lack the pipe2 syscall. On win32, this case invokes
1729 "_pipe (..., 4096, O_BINARY)".
1730
1731 If $flags is non-zero, it tries to invoke the pipe2 system call with
1732 the given flags (Linux 2.6.27, glibc 2.9).
1733
1734 On success, the read and write file handles are returned.
1735
1736 On error, nothing will be returned. If the pipe2 syscall is missing
1737 and $flags is non-zero, fails with "ENOSYS".
1738
1739 Please refer to pipe2(2) for more info on the $flags, but at the
1740 time of this writing, "IO::AIO::O_CLOEXEC", "IO::AIO::O_NONBLOCK"
1741 and "IO::AIO::O_DIRECT" (Linux 3.4, for packet-based pipes) were
1742 supported.
1743
1744EVENT LOOP INTEGRATION
1745 It is recommended to use AnyEvent::AIO to integrate IO::AIO
1746 automatically into many event loops:
1747
1748 # AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
1749 use AnyEvent::AIO;
1750
1751 You can also integrate IO::AIO manually into many event loops, here are
1752 some examples of how to do this:
1753
1754 # EV integration
1755 my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
1756
1757 # Event integration
1758 Event->io (fd => IO::AIO::poll_fileno,
1759 poll => 'r',
1760 cb => \&IO::AIO::poll_cb);
1761
1762 # Glib/Gtk2 integration
1763 add_watch Glib::IO IO::AIO::poll_fileno,
1764 in => sub { IO::AIO::poll_cb; 1 };
1765
1766 # Tk integration
1767 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
1768 readable => \&IO::AIO::poll_cb);
1769
1770 # Danga::Socket integration
1771 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
1772 \&IO::AIO::poll_cb);
1773
1774 FORK BEHAVIOUR
1775 Usage of pthreads in a program changes the semantics of fork
1776 considerably. Specifically, only async-safe functions can be called
1777 after fork. Perl doesn't know about this, so in general, you cannot call
1778 fork with defined behaviour in perl if pthreads are involved. IO::AIO
1779 uses pthreads, so this applies, but many other extensions and (for
1780 inexplicable reasons) perl itself often is linked against pthreads, so
1781 this limitation applies to quite a lot of perls.
1782
1783 This module no longer tries to fight your OS, or POSIX. That means
1784 IO::AIO only works in the process that loaded it. Forking is fully
1785 supported, but using IO::AIO in the child is not.
1786
1787 You might get around by not *using* IO::AIO before (or after) forking.
1788 You could also try to call the IO::AIO::reinit function in the child:
1789
1790 IO::AIO::reinit
1791 Abandons all current requests and I/O threads and simply
1792 reinitialises all data structures. This is not an operation
1793 supported by any standards, but happens to work on GNU/Linux and
1794 some newer BSD systems.
1795
1796 The only reasonable use for this function is to call it after
1797 forking, if "IO::AIO" was used in the parent. Calling it while
1798 IO::AIO is active in the process will result in undefined behaviour.
1799 Calling it at any time will also result in any undefined (by POSIX)
1800 behaviour.
1801
1802 MEMORY USAGE
1803 Per-request usage:
1804
1805 Each aio request uses - depending on your architecture - around 100-200
1806 bytes of memory. In addition, stat requests need a stat buffer (possibly
1807 a few hundred bytes), readdir requires a result buffer and so on. Perl
1808 scalars and other data passed into aio requests will also be locked and
1809 will consume memory till the request has entered the done state.
1810
1811 This is not awfully much, so queuing lots of requests is not usually a
1812 problem.
1813
1814 Per-thread usage:
1815
1816 In the execution phase, some aio requests require more memory for
1817 temporary buffers, and each thread requires a stack and other data
1818 structures (usually around 16k-128k, depending on the OS).
1819
1820KNOWN BUGS
1821 Known bugs will be fixed in the next release.
191 1822
192SEE ALSO 1823SEE ALSO
193 Coro, Linux::AIO. 1824 AnyEvent::AIO for easy integration into event loops, Coro::AIO for a
1825 more natural syntax.
194 1826
195AUTHOR 1827AUTHOR
196 Marc Lehmann <schmorp@schmorp.de> 1828 Marc Lehmann <schmorp@schmorp.de>
197 http://home.schmorp.de/ 1829 http://home.schmorp.de/
198 1830

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