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Revision 1.51 by root, Sat Apr 7 00:50:33 2012 UTC

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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 = shift 8 my $fh = shift
9 or die "/etc/passwd: $!"; 9 or die "/etc/passwd: $!";
10 ... 10 ...
11 }; 11 };
12 12
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24 $req->cancel; # cancel request if still in queue 24 $req->cancel; # cancel request if still in queue
25 25
26 my $grp = aio_group sub { print "all stats done\n" }; 26 my $grp = aio_group sub { print "all stats done\n" };
27 add $grp aio_stat "..." for ...; 27 add $grp aio_stat "..." for ...;
28 28
29 # AnyEvent integration
30 open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
31 my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
32
33 # Event integration
34 Event->io (fd => IO::AIO::poll_fileno,
35 poll => 'r',
36 cb => \&IO::AIO::poll_cb);
37
38 # Glib/Gtk2 integration
39 add_watch Glib::IO IO::AIO::poll_fileno,
40 in => sub { IO::AIO::poll_cb; 1 };
41
42 # Tk integration
43 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
44 readable => \&IO::AIO::poll_cb);
45
46 # Danga::Socket integration
47 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
48 \&IO::AIO::poll_cb);
49
50DESCRIPTION 29DESCRIPTION
51 This module implements asynchronous I/O using whatever means your 30 This module implements asynchronous I/O using whatever means your
52 operating system supports. 31 operating system supports. It is implemented as an interface to "libeio"
32 (<http://software.schmorp.de/pkg/libeio.html>).
53 33
54 Asynchronous means that operations that can normally block your program 34 Asynchronous means that operations that can normally block your program
55 (e.g. reading from disk) will be done asynchronously: the operation will 35 (e.g. reading from disk) will be done asynchronously: the operation will
56 still block, but you can do something else in the meantime. This is 36 still block, but you can do something else in the meantime. This is
57 extremely useful for programs that need to stay interactive even when 37 extremely useful for programs that need to stay interactive even when
… …
61 faster on a RAID volume or over NFS when you do a number of stat 41 faster on a RAID volume or over NFS when you do a number of stat
62 operations concurrently. 42 operations concurrently.
63 43
64 While most of this works on all types of file descriptors (for example 44 While most of this works on all types of file descriptors (for example
65 sockets), using these functions on file descriptors that support 45 sockets), using these functions on file descriptors that support
66 nonblocking operation (again, sockets, pipes etc.) is very inefficient 46 nonblocking operation (again, sockets, pipes etc.) is very inefficient.
67 or might not work (aio_read fails on sockets/pipes/fifos). Use an event
68 loop for that (such as the Event module): IO::AIO will naturally fit 47 Use an event loop for that (such as the EV module): IO::AIO will
69 into such an event loop itself. 48 naturally fit into such an event loop itself.
70 49
71 In this version, a number of threads are started that execute your 50 In this version, a number of threads are started that execute your
72 requests and signal their completion. You don't need thread support in 51 requests and signal their completion. You don't need thread support in
73 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
74 perl. In the future, this module might make use of the native aio 53 perl. In the future, this module might make use of the native aio
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76 not well-supported or restricted (GNU/Linux doesn't allow them on normal 55 not well-supported or restricted (GNU/Linux doesn't allow them on normal
77 files currently, for example), and they would only support aio_read and 56 files currently, for example), and they would only support aio_read and
78 aio_write, so the remaining functionality would have to be implemented 57 aio_write, so the remaining functionality would have to be implemented
79 using threads anyway. 58 using threads anyway.
80 59
81 Although the module will work with in the presence of other (Perl-) 60 Although the module will work in the presence of other (Perl-) threads,
82 threads, it is currently not reentrant in any way, so use appropriate 61 it is currently not reentrant in any way, so use appropriate locking
83 locking yourself, always call "poll_cb" from within the same thread, or 62 yourself, always call "poll_cb" from within the same thread, or never
84 never call "poll_cb" (or other "aio_" functions) recursively. 63 call "poll_cb" (or other "aio_" functions) recursively.
85 64
86 EXAMPLE 65 EXAMPLE
87 This is a simple example that uses the Event module and loads 66 This is a simple example that uses the EV module and loads /etc/passwd
88 /etc/passwd asynchronously: 67 asynchronously:
89 68
90 use Fcntl; 69 use Fcntl;
91 use Event; 70 use EV;
92 use IO::AIO; 71 use IO::AIO;
93 72
94 # register the IO::AIO callback with Event 73 # register the IO::AIO callback with EV
95 Event->io (fd => IO::AIO::poll_fileno, 74 my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
96 poll => 'r',
97 cb => \&IO::AIO::poll_cb);
98 75
99 # queue the request to open /etc/passwd 76 # queue the request to open /etc/passwd
100 aio_open "/etc/passwd", O_RDONLY, 0, sub { 77 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
101 my $fh = shift 78 my $fh = shift
102 or die "error while opening: $!"; 79 or die "error while opening: $!";
103 80
104 # stat'ing filehandles is generally non-blocking 81 # stat'ing filehandles is generally non-blocking
105 my $size = -s $fh; 82 my $size = -s $fh;
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114 91
115 # file contents now in $contents 92 # file contents now in $contents
116 print $contents; 93 print $contents;
117 94
118 # exit event loop and program 95 # exit event loop and program
119 Event::unloop; 96 EV::unloop;
120 }; 97 };
121 }; 98 };
122 99
123 # possibly queue up other requests, or open GUI windows, 100 # possibly queue up other requests, or open GUI windows,
124 # check for sockets etc. etc. 101 # check for sockets etc. etc.
125 102
126 # process events as long as there are some: 103 # process events as long as there are some:
127 Event::loop; 104 EV::loop;
128 105
129REQUEST ANATOMY AND LIFETIME 106REQUEST ANATOMY AND LIFETIME
130 Every "aio_*" function creates a request. which is a C data structure 107 Every "aio_*" function creates a request. which is a C data structure
131 not directly visible to Perl. 108 not directly visible to Perl.
132 109
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168 anymore (except possibly for the Perl object, but its connection to 145 anymore (except possibly for the Perl object, but its connection to
169 the actual aio request is severed and calling its methods will 146 the actual aio request is severed and calling its methods will
170 either do nothing or result in a runtime error). 147 either do nothing or result in a runtime error).
171 148
172FUNCTIONS 149FUNCTIONS
173 AIO REQUEST FUNCTIONS 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_seek $fh,$offset,$whence, $callback->($offs)
159 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
160 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
161 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
162 aio_readahead $fh,$offset,$length, $callback->($retval)
163 aio_stat $fh_or_path, $callback->($status)
164 aio_lstat $fh, $callback->($status)
165 aio_statvfs $fh_or_path, $callback->($statvfs)
166 aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
167 aio_chown $fh_or_path, $uid, $gid, $callback->($status)
168 aio_chmod $fh_or_path, $mode, $callback->($status)
169 aio_truncate $fh_or_path, $offset, $callback->($status)
170 aio_unlink $pathname, $callback->($status)
171 aio_mknod $pathname, $mode, $dev, $callback->($status)
172 aio_link $srcpath, $dstpath, $callback->($status)
173 aio_symlink $srcpath, $dstpath, $callback->($status)
174 aio_readlink $pathname, $callback->($link)
175 aio_realpath $pathname, $callback->($link)
176 aio_rename $srcpath, $dstpath, $callback->($status)
177 aio_mkdir $pathname, $mode, $callback->($status)
178 aio_rmdir $pathname, $callback->($status)
179 aio_readdir $pathname, $callback->($entries)
180 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
181 IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
182 IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
183 aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
184 aio_load $pathname, $data, $callback->($status)
185 aio_copy $srcpath, $dstpath, $callback->($status)
186 aio_move $srcpath, $dstpath, $callback->($status)
187 aio_rmtree $pathname, $callback->($status)
188 aio_sync $callback->($status)
189 aio_syncfs $fh, $callback->($status)
190 aio_fsync $fh, $callback->($status)
191 aio_fdatasync $fh, $callback->($status)
192 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
193 aio_pathsync $pathname, $callback->($status)
194 aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
195 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
196 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
197 aio_mlockall $flags, $callback->($status)
198 aio_group $callback->(...)
199 aio_nop $callback->()
200
201 $prev_pri = aioreq_pri [$pri]
202 aioreq_nice $pri_adjust
203
204 IO::AIO::poll_wait
205 IO::AIO::poll_cb
206 IO::AIO::poll
207 IO::AIO::flush
208 IO::AIO::max_poll_reqs $nreqs
209 IO::AIO::max_poll_time $seconds
210 IO::AIO::min_parallel $nthreads
211 IO::AIO::max_parallel $nthreads
212 IO::AIO::max_idle $nthreads
213 IO::AIO::idle_timeout $seconds
214 IO::AIO::max_outstanding $maxreqs
215 IO::AIO::nreqs
216 IO::AIO::nready
217 IO::AIO::npending
218
219 IO::AIO::sendfile $ofh, $ifh, $offset, $count
220 IO::AIO::fadvise $fh, $offset, $len, $advice
221 IO::AIO::madvise $scalar, $offset, $length, $advice
222 IO::AIO::mprotect $scalar, $offset, $length, $protect
223 IO::AIO::munlock $scalar, $offset = 0, $length = undef
224 IO::AIO::munlockall
225
226 API NOTES
174 All the "aio_*" calls are more or less thin wrappers around the syscall 227 All the "aio_*" calls are more or less thin wrappers around the syscall
175 with the same name (sans "aio_"). The arguments are similar or 228 with the same name (sans "aio_"). The arguments are similar or
176 identical, and they all accept an additional (and optional) $callback 229 identical, and they all accept an additional (and optional) $callback
177 argument which must be a code reference. This code reference will get 230 argument which must be a code reference. This code reference will be
178 called with the syscall return code (e.g. most syscalls return -1 on 231 called after the syscall has been executed in an asynchronous fashion.
179 error, unlike perl, which usually delivers "false") as it's sole 232 The results of the request will be passed as arguments to the callback
180 argument when the given syscall has been executed asynchronously. 233 (and, if an error occured, in $!) - for most requests the syscall return
234 code (e.g. most syscalls return -1 on error, unlike perl, which usually
235 delivers "false").
236
237 Some requests (such as "aio_readdir") pass the actual results and
238 communicate failures by passing "undef".
181 239
182 All functions expecting a filehandle keep a copy of the filehandle 240 All functions expecting a filehandle keep a copy of the filehandle
183 internally until the request has finished. 241 internally until the request has finished.
184 242
185 All functions return request objects of type IO::AIO::REQ that allow 243 All functions return request objects of type IO::AIO::REQ that allow
186 further manipulation of those requests while they are in-flight. 244 further manipulation of those requests while they are in-flight.
187 245
188 The pathnames you pass to these routines *must* be absolute and encoded 246 The pathnames you pass to these routines *should* be absolute. The
189 as octets. The reason for the former is that at the time the request is 247 reason for this is that at the time the request is being executed, the
190 being executed, the current working directory could have changed. 248 current working directory could have changed. Alternatively, you can
191 Alternatively, you can make sure that you never change the current 249 make sure that you never change the current working directory anywhere
192 working directory anywhere in the program and then use relative paths. 250 in the program and then use relative paths. You can also take advantage
251 of IO::AIOs working directory abstraction, that lets you specify paths
252 relative to some previously-opened "working directory object" - see the
253 description of the "IO::AIO::WD" class later in this document.
193 254
194 To encode pathnames as octets, either make sure you either: a) always 255 To encode pathnames as octets, either make sure you either: a) always
195 pass in filenames you got from outside (command line, readdir etc.) 256 pass in filenames you got from outside (command line, readdir etc.)
196 without tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module 257 without tinkering, b) are in your native filesystem encoding, c) use the
197 and encode your pathnames to the locale (or other) encoding in effect in 258 Encode module and encode your pathnames to the locale (or other)
198 the user environment, d) use Glib::filename_from_unicode on unicode 259 encoding in effect in the user environment, d) use
199 filenames or e) use something else to ensure your scalar has the correct 260 Glib::filename_from_unicode on unicode filenames or e) use something
200 contents. 261 else to ensure your scalar has the correct contents.
201 262
202 This works, btw. independent of the internal UTF-8 bit, which IO::AIO 263 This works, btw. independent of the internal UTF-8 bit, which IO::AIO
203 handles correctly wether it is set or not. 264 handles correctly whether it is set or not.
204 265
266 AIO REQUEST FUNCTIONS
205 $prev_pri = aioreq_pri [$pri] 267 $prev_pri = aioreq_pri [$pri]
206 Returns the priority value that would be used for the next request 268 Returns the priority value that would be used for the next request
207 and, if $pri is given, sets the priority for the next aio request. 269 and, if $pri is given, sets the priority for the next aio request.
208 270
209 The default priority is 0, the minimum and maximum priorities are -4 271 The default priority is 0, the minimum and maximum priorities are -4
… …
242 They are the same as used by "sysopen". 304 They are the same as used by "sysopen".
243 305
244 Likewise, $mode specifies the mode of the newly created file, if it 306 Likewise, $mode specifies the mode of the newly created file, if it
245 didn't exist and "O_CREAT" has been given, just like perl's 307 didn't exist and "O_CREAT" has been given, just like perl's
246 "sysopen", except that it is mandatory (i.e. use 0 if you don't 308 "sysopen", except that it is mandatory (i.e. use 0 if you don't
247 create new files, and 0666 or 0777 if you do). 309 create new files, and 0666 or 0777 if you do). Note that the $mode
310 will be modified by the umask in effect then the request is being
311 executed, so better never change the umask.
248 312
249 Example: 313 Example:
250 314
251 aio_open "/etc/passwd", O_RDONLY, 0, sub { 315 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
252 if ($_[0]) { 316 if ($_[0]) {
253 print "open successful, fh is $_[0]\n"; 317 print "open successful, fh is $_[0]\n";
254 ... 318 ...
255 } else { 319 } else {
256 die "open failed: $!\n"; 320 die "open failed: $!\n";
257 } 321 }
258 }; 322 };
259 323
324 In addition to all the common open modes/flags ("O_RDONLY",
325 "O_WRONLY", "O_RDWR", "O_CREAT", "O_TRUNC", "O_EXCL" and
326 "O_APPEND"), the following POSIX and non-POSIX constants are
327 available (missing ones on your system are, as usual, 0):
328
329 "O_ASYNC", "O_DIRECT", "O_NOATIME", "O_CLOEXEC", "O_NOCTTY",
330 "O_NOFOLLOW", "O_NONBLOCK", "O_EXEC", "O_SEARCH", "O_DIRECTORY",
331 "O_DSYNC", "O_RSYNC", "O_SYNC" and "O_TTY_INIT".
332
260 aio_close $fh, $callback->($status) 333 aio_close $fh, $callback->($status)
261 Asynchronously close a file and call the callback with the result 334 Asynchronously close a file and call the callback with the result
262 code. *WARNING:* although accepted, you should not pass in a perl 335 code.
263 filehandle here, as perl will likely close the file descriptor
264 another time when the filehandle is destroyed. Normally, you can
265 safely call perls "close" or just let filehandles go out of scope.
266 336
267 This is supposed to be a bug in the API, so that might change. It's 337 Unfortunately, you can't do this to perl. Perl *insists* very
268 therefore best to avoid this function. 338 strongly on closing the file descriptor associated with the
339 filehandle itself.
340
341 Therefore, "aio_close" will not close the filehandle - instead it
342 will use dup2 to overwrite the file descriptor with the write-end of
343 a pipe (the pipe fd will be created on demand and will be cached).
344
345 Or in other words: the file descriptor will be closed, but it will
346 not be free for reuse until the perl filehandle is closed.
347
348 aio_seek $fh, $offset, $whence, $callback->($offs)
349 Seeks the filehandle to the new $offset, similarly to perl's
350 "sysseek". The $whence can use the traditional values (0 for
351 "IO::AIO::SEEK_SET", 1 for "IO::AIO::SEEK_CUR" or 2 for
352 "IO::AIO::SEEK_END").
353
354 The resulting absolute offset will be passed to the callback, or -1
355 in case of an error.
356
357 In theory, the $whence constants could be different than the
358 corresponding values from Fcntl, but perl guarantees they are the
359 same, so don't panic.
269 360
270 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval) 361 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
271 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval) 362 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
272 Reads or writes "length" bytes from the specified "fh" and "offset" 363 Reads or writes $length bytes from or to the specified $fh and
273 into the scalar given by "data" and offset "dataoffset" and calls 364 $offset into the scalar given by $data and offset $dataoffset and
274 the callback without the actual number of bytes read (or -1 on 365 calls the callback without the actual number of bytes read (or -1 on
275 error, just like the syscall). 366 error, just like the syscall).
276 367
368 "aio_read" will, like "sysread", shrink or grow the $data scalar to
369 offset plus the actual number of bytes read.
370
371 If $offset is undefined, then the current file descriptor offset
372 will be used (and updated), otherwise the file descriptor offset
373 will not be changed by these calls.
374
375 If $length is undefined in "aio_write", use the remaining length of
376 $data.
377
378 If $dataoffset is less than zero, it will be counted from the end of
379 $data.
380
277 The $data scalar *MUST NOT* be modified in any way while the request 381 The $data scalar *MUST NOT* be modified in any way while the request
278 is outstanding. Modifying it can result in segfaults or WW3 (if the 382 is outstanding. Modifying it can result in segfaults or World War
279 necessary/optional hardware is installed). 383 III (if the necessary/optional hardware is installed).
280 384
281 Example: Read 15 bytes at offset 7 into scalar $buffer, starting at 385 Example: Read 15 bytes at offset 7 into scalar $buffer, starting at
282 offset 0 within the scalar: 386 offset 0 within the scalar:
283 387
284 aio_read $fh, 7, 15, $buffer, 0, sub { 388 aio_read $fh, 7, 15, $buffer, 0, sub {
… …
289 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval) 393 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
290 Tries to copy $length bytes from $in_fh to $out_fh. It starts 394 Tries to copy $length bytes from $in_fh to $out_fh. It starts
291 reading at byte offset $in_offset, and starts writing at the current 395 reading at byte offset $in_offset, and starts writing at the current
292 file offset of $out_fh. Because of that, it is not safe to issue 396 file offset of $out_fh. Because of that, it is not safe to issue
293 more than one "aio_sendfile" per $out_fh, as they will interfere 397 more than one "aio_sendfile" per $out_fh, as they will interfere
294 with each other. 398 with each other. The same $in_fh works fine though, as this function
399 does not move or use the file offset of $in_fh.
295 400
401 Please note that "aio_sendfile" can read more bytes from $in_fh than
402 are written, and there is no way to find out how many more bytes
403 have been read from "aio_sendfile" alone, as "aio_sendfile" only
404 provides the number of bytes written to $out_fh. Only if the result
405 value equals $length one can assume that $length bytes have been
406 read.
407
408 Unlike with other "aio_" functions, it makes a lot of sense to use
409 "aio_sendfile" on non-blocking sockets, as long as one end
410 (typically the $in_fh) is a file - the file I/O will then be
411 asynchronous, while the socket I/O will be non-blocking. Note,
412 however, that you can run into a trap where "aio_sendfile" reads
413 some data with readahead, then fails to write all data, and when the
414 socket is ready the next time, the data in the cache is already
415 lost, forcing "aio_sendfile" to again hit the disk. Explicit
416 "aio_read" + "aio_write" let's you better control resource usage.
417
296 This call tries to make use of a native "sendfile" syscall to 418 This call tries to make use of a native "sendfile"-like syscall to
297 provide zero-copy operation. For this to work, $out_fh should refer 419 provide zero-copy operation. For this to work, $out_fh should refer
298 to a socket, and $in_fh should refer to mmap'able file. 420 to a socket, and $in_fh should refer to an mmap'able file.
299 421
300 If the native sendfile call fails or is not implemented, it will be 422 If a native sendfile cannot be found or it fails with "ENOSYS",
301 emulated, so you can call "aio_sendfile" on any type of filehandle 423 "EINVAL", "ENOTSUP", "EOPNOTSUPP", "EAFNOSUPPORT", "EPROTOTYPE" or
302 regardless of the limitations of the operating system. 424 "ENOTSOCK", it will be emulated, so you can call "aio_sendfile" on
425 any type of filehandle regardless of the limitations of the
426 operating system.
303 427
304 Please note, however, that "aio_sendfile" can read more bytes from 428 As native sendfile syscalls (as practically any non-POSIX interface
305 $in_fh than are written, and there is no way to find out how many 429 hacked together in a hurry to improve benchmark numbers) tend to be
306 bytes have been read from "aio_sendfile" alone, as "aio_sendfile" 430 rather buggy on many systems, this implementation tries to work
307 only provides the number of bytes written to $out_fh. Only if the 431 around some known bugs in Linux and FreeBSD kernels (probably
308 result value equals $length one can assume that $length bytes have 432 others, too), but that might fail, so you really really should check
309 been read. 433 the return value of "aio_sendfile" - fewre bytes than expected might
434 have been transferred.
310 435
311 aio_readahead $fh,$offset,$length, $callback->($retval) 436 aio_readahead $fh,$offset,$length, $callback->($retval)
312 "aio_readahead" populates the page cache with data from a file so 437 "aio_readahead" populates the page cache with data from a file so
313 that subsequent reads from that file will not block on disk I/O. The 438 that subsequent reads from that file will not block on disk I/O. The
314 $offset argument specifies the starting point from which data is to 439 $offset argument specifies the starting point from which data is to
… …
335 Currently, the stats are always 64-bit-stats, i.e. instead of 460 Currently, the stats are always 64-bit-stats, i.e. instead of
336 returning an error when stat'ing a large file, the results will be 461 returning an error when stat'ing a large file, the results will be
337 silently truncated unless perl itself is compiled with large file 462 silently truncated unless perl itself is compiled with large file
338 support. 463 support.
339 464
465 To help interpret the mode and dev/rdev stat values, IO::AIO offers
466 the following constants and functions (if not implemented, the
467 constants will be 0 and the functions will either "croak" or fall
468 back on traditional behaviour).
469
470 "S_IFMT", "S_IFIFO", "S_IFCHR", "S_IFBLK", "S_IFLNK", "S_IFREG",
471 "S_IFDIR", "S_IFWHT", "S_IFSOCK", "IO::AIO::major $dev_t",
472 "IO::AIO::minor $dev_t", "IO::AIO::makedev $major, $minor".
473
340 Example: Print the length of /etc/passwd: 474 Example: Print the length of /etc/passwd:
341 475
342 aio_stat "/etc/passwd", sub { 476 aio_stat "/etc/passwd", sub {
343 $_[0] and die "stat failed: $!"; 477 $_[0] and die "stat failed: $!";
344 print "size is ", -s _, "\n"; 478 print "size is ", -s _, "\n";
345 }; 479 };
346 480
481 aio_statvfs $fh_or_path, $callback->($statvfs)
482 Works like the POSIX "statvfs" or "fstatvfs" syscalls, depending on
483 whether a file handle or path was passed.
484
485 On success, the callback is passed a hash reference with the
486 following members: "bsize", "frsize", "blocks", "bfree", "bavail",
487 "files", "ffree", "favail", "fsid", "flag" and "namemax". On
488 failure, "undef" is passed.
489
490 The following POSIX IO::AIO::ST_* constants are defined: "ST_RDONLY"
491 and "ST_NOSUID".
492
493 The following non-POSIX IO::AIO::ST_* flag masks are defined to
494 their correct value when available, or to 0 on systems that do not
495 support them: "ST_NODEV", "ST_NOEXEC", "ST_SYNCHRONOUS",
496 "ST_MANDLOCK", "ST_WRITE", "ST_APPEND", "ST_IMMUTABLE",
497 "ST_NOATIME", "ST_NODIRATIME" and "ST_RELATIME".
498
499 Example: stat "/wd" and dump out the data if successful.
500
501 aio_statvfs "/wd", sub {
502 my $f = $_[0]
503 or die "statvfs: $!";
504
505 use Data::Dumper;
506 say Dumper $f;
507 };
508
509 # result:
510 {
511 bsize => 1024,
512 bfree => 4333064312,
513 blocks => 10253828096,
514 files => 2050765568,
515 flag => 4096,
516 favail => 2042092649,
517 bavail => 4333064312,
518 ffree => 2042092649,
519 namemax => 255,
520 frsize => 1024,
521 fsid => 1810
522 }
523
524 aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
525 Works like perl's "utime" function (including the special case of
526 $atime and $mtime being undef). Fractional times are supported if
527 the underlying syscalls support them.
528
529 When called with a pathname, uses utimes(2) if available, otherwise
530 utime(2). If called on a file descriptor, uses futimes(2) if
531 available, otherwise returns ENOSYS, so this is not portable.
532
533 Examples:
534
535 # set atime and mtime to current time (basically touch(1)):
536 aio_utime "path", undef, undef;
537 # set atime to current time and mtime to beginning of the epoch:
538 aio_utime "path", time, undef; # undef==0
539
540 aio_chown $fh_or_path, $uid, $gid, $callback->($status)
541 Works like perl's "chown" function, except that "undef" for either
542 $uid or $gid is being interpreted as "do not change" (but -1 can
543 also be used).
544
545 Examples:
546
547 # same as "chown root path" in the shell:
548 aio_chown "path", 0, -1;
549 # same as above:
550 aio_chown "path", 0, undef;
551
552 aio_truncate $fh_or_path, $offset, $callback->($status)
553 Works like truncate(2) or ftruncate(2).
554
555 aio_chmod $fh_or_path, $mode, $callback->($status)
556 Works like perl's "chmod" function.
557
347 aio_unlink $pathname, $callback->($status) 558 aio_unlink $pathname, $callback->($status)
348 Asynchronously unlink (delete) a file and call the callback with the 559 Asynchronously unlink (delete) a file and call the callback with the
349 result code. 560 result code.
350 561
351 aio_mknod $path, $mode, $dev, $callback->($status) 562 aio_mknod $pathname, $mode, $dev, $callback->($status)
352 [EXPERIMENTAL] 563 [EXPERIMENTAL]
353 564
354 Asynchronously create a device node (or fifo). See mknod(2). 565 Asynchronously create a device node (or fifo). See mknod(2).
355 566
356 The only (POSIX-) portable way of calling this function is: 567 The only (POSIX-) portable way of calling this function is:
357 568
358 aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ... 569 aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
570
571 See "aio_stat" for info about some potentially helpful extra
572 constants and functions.
359 573
360 aio_link $srcpath, $dstpath, $callback->($status) 574 aio_link $srcpath, $dstpath, $callback->($status)
361 Asynchronously create a new link to the existing object at $srcpath 575 Asynchronously create a new link to the existing object at $srcpath
362 at the path $dstpath and call the callback with the result code. 576 at the path $dstpath and call the callback with the result code.
363 577
364 aio_symlink $srcpath, $dstpath, $callback->($status) 578 aio_symlink $srcpath, $dstpath, $callback->($status)
365 Asynchronously create a new symbolic link to the existing object at 579 Asynchronously create a new symbolic link to the existing object at
366 $srcpath at the path $dstpath and call the callback with the result 580 $srcpath at the path $dstpath and call the callback with the result
367 code. 581 code.
368 582
369 aio_readlink $path, $callback->($link) 583 aio_readlink $pathname, $callback->($link)
370 Asynchronously read the symlink specified by $path and pass it to 584 Asynchronously read the symlink specified by $path and pass it to
371 the callback. If an error occurs, nothing or undef gets passed to 585 the callback. If an error occurs, nothing or undef gets passed to
372 the callback. 586 the callback.
373 587
588 aio_realpath $pathname, $callback->($path)
589 Asynchronously make the path absolute and resolve any symlinks in
590 $path. The resulting path only consists of directories (Same as
591 Cwd::realpath).
592
593 This request can be used to get the absolute path of the current
594 working directory by passing it a path of . (a single dot).
595
374 aio_rename $srcpath, $dstpath, $callback->($status) 596 aio_rename $srcpath, $dstpath, $callback->($status)
375 Asynchronously rename the object at $srcpath to $dstpath, just as 597 Asynchronously rename the object at $srcpath to $dstpath, just as
376 rename(2) and call the callback with the result code. 598 rename(2) and call the callback with the result code.
599
600 aio_mkdir $pathname, $mode, $callback->($status)
601 Asynchronously mkdir (create) a directory and call the callback with
602 the result code. $mode will be modified by the umask at the time the
603 request is executed, so do not change your umask.
377 604
378 aio_rmdir $pathname, $callback->($status) 605 aio_rmdir $pathname, $callback->($status)
379 Asynchronously rmdir (delete) a directory and call the callback with 606 Asynchronously rmdir (delete) a directory and call the callback with
380 the result code. 607 the result code.
381 608
382 aio_readdir $pathname, $callback->($entries) 609 aio_readdir $pathname, $callback->($entries)
383 Unlike the POSIX call of the same name, "aio_readdir" reads an 610 Unlike the POSIX call of the same name, "aio_readdir" reads an
384 entire directory (i.e. opendir + readdir + closedir). The entries 611 entire directory (i.e. opendir + readdir + closedir). The entries
385 will not be sorted, and will NOT include the "." and ".." entries. 612 will not be sorted, and will NOT include the "." and ".." entries.
386 613
387 The callback a single argument which is either "undef" or an 614 The callback is passed a single argument which is either "undef" or
388 array-ref with the filenames. 615 an array-ref with the filenames.
616
617 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
618 Quite similar to "aio_readdir", but the $flags argument allows one
619 to tune behaviour and output format. In case of an error, $entries
620 will be "undef".
621
622 The flags are a combination of the following constants, ORed
623 together (the flags will also be passed to the callback, possibly
624 modified):
625
626 IO::AIO::READDIR_DENTS
627 When this flag is off, then the callback gets an arrayref
628 consisting of names only (as with "aio_readdir"), otherwise it
629 gets an arrayref with "[$name, $type, $inode]" arrayrefs, each
630 describing a single directory entry in more detail.
631
632 $name is the name of the entry.
633
634 $type is one of the "IO::AIO::DT_xxx" constants:
635
636 "IO::AIO::DT_UNKNOWN", "IO::AIO::DT_FIFO", "IO::AIO::DT_CHR",
637 "IO::AIO::DT_DIR", "IO::AIO::DT_BLK", "IO::AIO::DT_REG",
638 "IO::AIO::DT_LNK", "IO::AIO::DT_SOCK", "IO::AIO::DT_WHT".
639
640 "IO::AIO::DT_UNKNOWN" means just that: readdir does not know. If
641 you need to know, you have to run stat yourself. Also, for speed
642 reasons, the $type scalars are read-only: you can not modify
643 them.
644
645 $inode is the inode number (which might not be exact on systems
646 with 64 bit inode numbers and 32 bit perls). This field has
647 unspecified content on systems that do not deliver the inode
648 information.
649
650 IO::AIO::READDIR_DIRS_FIRST
651 When this flag is set, then the names will be returned in an
652 order where likely directories come first, in optimal stat
653 order. This is useful when you need to quickly find directories,
654 or you want to find all directories while avoiding to stat()
655 each entry.
656
657 If the system returns type information in readdir, then this is
658 used to find directories directly. Otherwise, likely directories
659 are names beginning with ".", or otherwise names with no dots,
660 of which names with short names are tried first.
661
662 IO::AIO::READDIR_STAT_ORDER
663 When this flag is set, then the names will be returned in an
664 order suitable for stat()'ing each one. That is, when you plan
665 to stat() all files in the given directory, then the returned
666 order will likely be fastest.
667
668 If both this flag and "IO::AIO::READDIR_DIRS_FIRST" are
669 specified, then the likely dirs come first, resulting in a less
670 optimal stat order.
671
672 IO::AIO::READDIR_FOUND_UNKNOWN
673 This flag should not be set when calling "aio_readdirx".
674 Instead, it is being set by "aio_readdirx", when any of the
675 $type's found were "IO::AIO::DT_UNKNOWN". The absence of this
676 flag therefore indicates that all $type's are known, which can
677 be used to speed up some algorithms.
678
679 aio_load $pathname, $data, $callback->($status)
680 This is a composite request that tries to fully load the given file
681 into memory. Status is the same as with aio_read.
389 682
390 aio_copy $srcpath, $dstpath, $callback->($status) 683 aio_copy $srcpath, $dstpath, $callback->($status)
391 Try to copy the *file* (directories not supported as either source 684 Try to copy the *file* (directories not supported as either source
392 or destination) from $srcpath to $dstpath and call the callback with 685 or destination) from $srcpath to $dstpath and call the callback with
393 the 0 (error) or -1 ok. 686 a status of 0 (ok) or -1 (error, see $!).
394 687
395 This is a composite request that it creates the destination file 688 This is a composite request that creates the destination file with
396 with mode 0200 and copies the contents of the source file into it 689 mode 0200 and copies the contents of the source file into it using
397 using "aio_sendfile", followed by restoring atime, mtime, access 690 "aio_sendfile", followed by restoring atime, mtime, access mode and
398 mode and uid/gid, in that order. 691 uid/gid, in that order.
399 692
400 If an error occurs, the partial destination file will be unlinked, 693 If an error occurs, the partial destination file will be unlinked,
401 if possible, except when setting atime, mtime, access mode and 694 if possible, except when setting atime, mtime, access mode and
402 uid/gid, where errors are being ignored. 695 uid/gid, where errors are being ignored.
403 696
404 aio_move $srcpath, $dstpath, $callback->($status) 697 aio_move $srcpath, $dstpath, $callback->($status)
405 Try to move the *file* (directories not supported as either source 698 Try to move the *file* (directories not supported as either source
406 or destination) from $srcpath to $dstpath and call the callback with 699 or destination) from $srcpath to $dstpath and call the callback with
407 the 0 (error) or -1 ok. 700 a status of 0 (ok) or -1 (error, see $!).
408 701
409 This is a composite request that tries to rename(2) the file first. 702 This is a composite request that tries to rename(2) the file first;
410 If rename files with "EXDEV", it copies the file with "aio_copy" 703 if rename fails with "EXDEV", it copies the file with "aio_copy"
411 and, if that is successful, unlinking the $srcpath. 704 and, if that is successful, unlinks the $srcpath.
412 705
413 aio_scandir $path, $maxreq, $callback->($dirs, $nondirs) 706 aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
414 Scans a directory (similar to "aio_readdir") but additionally tries 707 Scans a directory (similar to "aio_readdir") but additionally tries
415 to efficiently separate the entries of directory $path into two sets 708 to efficiently separate the entries of directory $path into two sets
416 of names, directories you can recurse into (directories), and ones 709 of names, directories you can recurse into (directories), and ones
417 you cannot recurse into (everything else, including symlinks to 710 you cannot recurse into (everything else, including symlinks to
418 directories). 711 directories).
… …
436 Implementation notes. 729 Implementation notes.
437 730
438 The "aio_readdir" cannot be avoided, but "stat()"'ing every entry 731 The "aio_readdir" cannot be avoided, but "stat()"'ing every entry
439 can. 732 can.
440 733
734 If readdir returns file type information, then this is used directly
735 to find directories.
736
441 After reading the directory, the modification time, size etc. of the 737 Otherwise, after reading the directory, the modification time, size
442 directory before and after the readdir is checked, and if they match 738 etc. of the directory before and after the readdir is checked, and
443 (and isn't the current time), the link count will be used to decide 739 if they match (and isn't the current time), the link count will be
444 how many entries are directories (if >= 2). Otherwise, no knowledge 740 used to decide how many entries are directories (if >= 2).
445 of the number of subdirectories will be assumed. 741 Otherwise, no knowledge of the number of subdirectories will be
742 assumed.
446 743
447 Then entries will be sorted into likely directories (everything 744 Then entries will be sorted into likely directories a non-initial
448 without a non-initial dot currently) and likely non-directories 745 dot currently) and likely non-directories (see "aio_readdirx"). Then
449 (everything else). Then every entry plus an appended "/." will be 746 every entry plus an appended "/." will be "stat"'ed, likely
450 "stat"'ed, likely directories first. If that succeeds, it assumes 747 directories first, in order of their inode numbers. If that
451 that the entry is a directory or a symlink to directory (which will 748 succeeds, it assumes that the entry is a directory or a symlink to
452 be checked seperately). This is often faster than stat'ing the entry 749 directory (which will be checked separately). This is often faster
453 itself because filesystems might detect the type of the entry 750 than stat'ing the entry itself because filesystems might detect the
454 without reading the inode data (e.g. ext2fs filetype feature). 751 type of the entry without reading the inode data (e.g. ext2fs
752 filetype feature), even on systems that cannot return the filetype
753 information on readdir.
455 754
456 If the known number of directories (link count - 2) has been 755 If the known number of directories (link count - 2) has been
457 reached, the rest of the entries is assumed to be non-directories. 756 reached, the rest of the entries is assumed to be non-directories.
458 757
459 This only works with certainty on POSIX (= UNIX) filesystems, which 758 This only works with certainty on POSIX (= UNIX) filesystems, which
… …
461 760
462 It will also likely work on non-POSIX filesystems with reduced 761 It will also likely work on non-POSIX filesystems with reduced
463 efficiency as those tend to return 0 or 1 as link counts, which 762 efficiency as those tend to return 0 or 1 as link counts, which
464 disables the directory counting heuristic. 763 disables the directory counting heuristic.
465 764
765 aio_rmtree $pathname, $callback->($status)
766 Delete a directory tree starting (and including) $path, return the
767 status of the final "rmdir" only. This is a composite request that
768 uses "aio_scandir" to recurse into and rmdir directories, and unlink
769 everything else.
770
771 aio_sync $callback->($status)
772 Asynchronously call sync and call the callback when finished.
773
466 aio_fsync $fh, $callback->($status) 774 aio_fsync $fh, $callback->($status)
467 Asynchronously call fsync on the given filehandle and call the 775 Asynchronously call fsync on the given filehandle and call the
468 callback with the fsync result code. 776 callback with the fsync result code.
469 777
470 aio_fdatasync $fh, $callback->($status) 778 aio_fdatasync $fh, $callback->($status)
471 Asynchronously call fdatasync on the given filehandle and call the 779 Asynchronously call fdatasync on the given filehandle and call the
472 callback with the fdatasync result code. 780 callback with the fdatasync result code.
473 781
474 If this call isn't available because your OS lacks it or it couldn't 782 If this call isn't available because your OS lacks it or it couldn't
475 be detected, it will be emulated by calling "fsync" instead. 783 be detected, it will be emulated by calling "fsync" instead.
784
785 aio_syncfs $fh, $callback->($status)
786 Asynchronously call the syncfs syscall to sync the filesystem
787 associated to the given filehandle and call the callback with the
788 syncfs result code. If syncfs is not available, calls sync(), but
789 returns -1 and sets errno to "ENOSYS" nevertheless.
790
791 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
792 Sync the data portion of the file specified by $offset and $length
793 to disk (but NOT the metadata), by calling the Linux-specific
794 sync_file_range call. If sync_file_range is not available or it
795 returns ENOSYS, then fdatasync or fsync is being substituted.
796
797 $flags can be a combination of
798 "IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE",
799 "IO::AIO::SYNC_FILE_RANGE_WRITE" and
800 "IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER": refer to the sync_file_range
801 manpage for details.
802
803 aio_pathsync $pathname, $callback->($status)
804 This request tries to open, fsync and close the given path. This is
805 a composite request intended to sync directories after directory
806 operations (E.g. rename). This might not work on all operating
807 systems or have any specific effect, but usually it makes sure that
808 directory changes get written to disc. It works for anything that
809 can be opened for read-only, not just directories.
810
811 Future versions of this function might fall back to other methods
812 when "fsync" on the directory fails (such as calling "sync").
813
814 Passes 0 when everything went ok, and -1 on error.
815
816 aio_msync $scalar, $offset = 0, $length = undef, flags = 0,
817 $callback->($status)
818 This is a rather advanced IO::AIO call, which only works on
819 mmap(2)ed scalars (see the "IO::AIO::mmap" function, although it
820 also works on data scalars managed by the Sys::Mmap or Mmap modules,
821 note that the scalar must only be modified in-place while an aio
822 operation is pending on it).
823
824 It calls the "msync" function of your OS, if available, with the
825 memory area starting at $offset in the string and ending $length
826 bytes later. If $length is negative, counts from the end, and if
827 $length is "undef", then it goes till the end of the string. The
828 flags can be a combination of "IO::AIO::MS_ASYNC",
829 "IO::AIO::MS_INVALIDATE" and "IO::AIO::MS_SYNC".
830
831 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0,
832 $callback->($status)
833 This is a rather advanced IO::AIO call, which works best on
834 mmap(2)ed scalars.
835
836 It touches (reads or writes) all memory pages in the specified range
837 inside the scalar. All caveats and parameters are the same as for
838 "aio_msync", above, except for flags, which must be either 0 (which
839 reads all pages and ensures they are instantiated) or
840 "IO::AIO::MT_MODIFY", which modifies the memory page s(by reading
841 and writing an octet from it, which dirties the page).
842
843 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
844 This is a rather advanced IO::AIO call, which works best on
845 mmap(2)ed scalars.
846
847 It reads in all the pages of the underlying storage into memory (if
848 any) and locks them, so they are not getting swapped/paged out or
849 removed.
850
851 If $length is undefined, then the scalar will be locked till the
852 end.
853
854 On systems that do not implement "mlock", this function returns -1
855 and sets errno to "ENOSYS".
856
857 Note that the corresponding "munlock" is synchronous and is
858 documented under "MISCELLANEOUS FUNCTIONS".
859
860 Example: open a file, mmap and mlock it - both will be undone when
861 $data gets destroyed.
862
863 open my $fh, "<", $path or die "$path: $!";
864 my $data;
865 IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
866 aio_mlock $data; # mlock in background
867
868 aio_mlockall $flags, $callback->($status)
869 Calls the "mlockall" function with the given $flags (a combination
870 of "IO::AIO::MCL_CURRENT" and "IO::AIO::MCL_FUTURE").
871
872 On systems that do not implement "mlockall", this function returns
873 -1 and sets errno to "ENOSYS".
874
875 Note that the corresponding "munlockall" is synchronous and is
876 documented under "MISCELLANEOUS FUNCTIONS".
877
878 Example: asynchronously lock all current and future pages into
879 memory.
880
881 aio_mlockall IO::AIO::MCL_FUTURE;
882
883 aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
884 Queries the extents of the given file (by calling the Linux FIEMAP
885 ioctl, see <http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for
886 details). If the "ioctl" is not available on your OS, then this
887 rquiest will fail with "ENOSYS".
888
889 $start is the starting offset to query extents for, $length is the
890 size of the range to query - if it is "undef", then the whole file
891 will be queried.
892
893 $flags is a combination of flags ("IO::AIO::FIEMAP_FLAG_SYNC" or
894 "IO::AIO::FIEMAP_FLAG_XATTR" - "IO::AIO::FIEMAP_FLAGS_COMPAT" is
895 also exported), and is normally 0 or "IO::AIO::FIEMAP_FLAG_SYNC" to
896 query the data portion.
897
898 $count is the maximum number of extent records to return. If it is
899 "undef", then IO::AIO queries all extents of the file. As a very
900 special case, if it is 0, then the callback receives the number of
901 extents instead of the extents themselves.
902
903 If an error occurs, the callback receives no arguments. The special
904 "errno" value "IO::AIO::EBADR" is available to test for flag errors.
905
906 Otherwise, the callback receives an array reference with extent
907 structures. Each extent structure is an array reference itself, with
908 the following members:
909
910 [$logical, $physical, $length, $flags]
911
912 Flags is any combination of the following flag values (typically
913 either 0 or "IO::AIO::FIEMAP_EXTENT_LAST"):
914
915 "IO::AIO::FIEMAP_EXTENT_LAST", "IO::AIO::FIEMAP_EXTENT_UNKNOWN",
916 "IO::AIO::FIEMAP_EXTENT_DELALLOC", "IO::AIO::FIEMAP_EXTENT_ENCODED",
917 "IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED",
918 "IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED",
919 "IO::AIO::FIEMAP_EXTENT_DATA_INLINE",
920 "IO::AIO::FIEMAP_EXTENT_DATA_TAIL",
921 "IO::AIO::FIEMAP_EXTENT_UNWRITTEN", "IO::AIO::FIEMAP_EXTENT_MERGED"
922 or "IO::AIO::FIEMAP_EXTENT_SHARED".
476 923
477 aio_group $callback->(...) 924 aio_group $callback->(...)
478 This is a very special aio request: Instead of doing something, it 925 This is a very special aio request: Instead of doing something, it
479 is a container for other aio requests, which is useful if you want 926 is a container for other aio requests, which is useful if you want
480 to bundle many requests into a single, composite, request with a 927 to bundle many requests into a single, composite, request with a
… …
515 requests like sleep and file handle readable/writable, the overhead 962 requests like sleep and file handle readable/writable, the overhead
516 this creates is immense (it blocks a thread for a long time) so do 963 this creates is immense (it blocks a thread for a long time) so do
517 not use this function except to put your application under 964 not use this function except to put your application under
518 artificial I/O pressure. 965 artificial I/O pressure.
519 966
967 IO::AIO::WD - multiple working directories
968 Your process only has one current working directory, which is used by
969 all threads. This makes it hard to use relative paths (some other
970 component could call "chdir" at any time, and it is hard to control when
971 the path will be used by IO::AIO).
972
973 One solution for this is to always use absolute paths. This usually
974 works, but can be quite slow (the kernel has to walk the whole path on
975 every access), and can also be a hassle to implement.
976
977 Newer POSIX systems have a number of functions (openat, fdopendir,
978 futimensat and so on) that make it possible to specify working
979 directories per operation.
980
981 For portability, and because the clowns who "designed", or shall I
982 write, perpetrated this new interface were obviously half-drunk, this
983 abstraction cannot be perfect, though.
984
985 IO::AIO allows you to convert directory paths into a so-called
986 IO::AIO::WD object. This object stores the canonicalised, absolute
987 version of the path, and on systems that allow it, also a directory file
988 descriptor.
989
990 Everywhere where a pathname is accepted by IO::AIO (e.g. in "aio_stat"
991 or "aio_unlink"), one can specify an array reference with an IO::AIO::WD
992 object and a pathname instead (or the IO::AIO::WD object alone, which
993 gets interpreted as "[$wd, "."]"). If the pathname is absolute, the
994 IO::AIO::WD object is ignored, otherwise the pathname is resolved
995 relative to that IO::AIO::WD object.
996
997 For example, to get a wd object for /etc and then stat passwd inside,
998 you would write:
999
1000 aio_wd "/etc", sub {
1001 my $etcdir = shift;
1002
1003 # although $etcdir can be undef on error, there is generally no reason
1004 # to check for errors here, as aio_stat will fail with ENOENT
1005 # when $etcdir is undef.
1006
1007 aio_stat [$etcdir, "passwd"], sub {
1008 # yay
1009 };
1010 };
1011
1012 That "aio_wd" is a request and not a normal function shows that creating
1013 an IO::AIO::WD object is itself a potentially blocking operation, which
1014 is why it is done asynchronously.
1015
1016 To stat the directory obtained with "aio_wd" above, one could write
1017 either of the following three request calls:
1018
1019 aio_lstat "/etc" , sub { ... # pathname as normal string
1020 aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
1021 aio_lstat $wd , sub { ... # shorthand for the previous
1022
1023 As with normal pathnames, IO::AIO keeps a copy of the working directory
1024 object and the pathname string, so you could write the following without
1025 causing any issues due to $path getting reused:
1026
1027 my $path = [$wd, undef];
1028
1029 for my $name (qw(abc def ghi)) {
1030 $path->[1] = $name;
1031 aio_stat $path, sub {
1032 # ...
1033 };
1034 }
1035
1036 There are some caveats: when directories get renamed (or deleted), the
1037 pathname string doesn't change, so will point to the new directory (or
1038 nowhere at all), while the directory fd, if available on the system,
1039 will still point to the original directory. Most functions accepting a
1040 pathname will use the directory fd on newer systems, and the string on
1041 older systems. Some functions (such as realpath) will always rely on the
1042 string form of the pathname.
1043
1044 So this fucntionality is mainly useful to get some protection against
1045 "chdir", to easily get an absolute path out of a relative path for
1046 future reference, and to speed up doing many operations in the same
1047 directory (e.g. when stat'ing all files in a directory).
1048
1049 The following functions implement this working directory abstraction:
1050
1051 aio_wd $pathname, $callback->($wd)
1052 Asynchonously canonicalise the given pathname and convert it to an
1053 IO::AIO::WD object representing it. If possible and supported on the
1054 system, also open a directory fd to speed up pathname resolution
1055 relative to this working directory.
1056
1057 If something goes wrong, then "undef" is passwd to the callback
1058 instead of a working directory object and $! is set appropriately.
1059 Since passing "undef" as working directory component of a pathname
1060 fails the request with "ENOENT", there is often no need for error
1061 checking in the "aio_wd" callback, as future requests using the
1062 value will fail in the expected way.
1063
1064 If this call isn't available because your OS lacks it or it couldn't
1065 be detected, it will be emulated by calling "fsync" instead.
1066
1067 IO::AIO::CWD
1068 This is a compiletime constant (object) that represents the process
1069 current working directory.
1070
1071 Specifying this object as working directory object for a pathname is
1072 as if the pathname would be specified directly, without a directory
1073 object, e.g., these calls are functionally identical:
1074
1075 aio_stat "somefile", sub { ... };
1076 aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
1077
520 IO::AIO::REQ CLASS 1078 IO::AIO::REQ CLASS
521 All non-aggregate "aio_*" functions return an object of this class when 1079 All non-aggregate "aio_*" functions return an object of this class when
522 called in non-void context. 1080 called in non-void context.
523 1081
524 cancel $req 1082 cancel $req
525 Cancels the request, if possible. Has the effect of skipping 1083 Cancels the request, if possible. Has the effect of skipping
526 execution when entering the execute state and skipping calling the 1084 execution when entering the execute state and skipping calling the
527 callback when entering the the result state, but will leave the 1085 callback when entering the the result state, but will leave the
528 request otherwise untouched. That means that requests that currently 1086 request otherwise untouched (with the exception of readdir). That
529 execute will not be stopped and resources held by the request will 1087 means that requests that currently execute will not be stopped and
530 not be freed prematurely. 1088 resources held by the request will not be freed prematurely.
531 1089
532 cb $req $callback->(...) 1090 cb $req $callback->(...)
533 Replace (or simply set) the callback registered to the request. 1091 Replace (or simply set) the callback registered to the request.
534 1092
535 IO::AIO::GRP CLASS 1093 IO::AIO::GRP CLASS
… …
562 }; 1120 };
563 1121
564 This makes it very easy to create composite requests (see the source of 1122 This makes it very easy to create composite requests (see the source of
565 "aio_move" for an application) that work and feel like simple requests. 1123 "aio_move" for an application) that work and feel like simple requests.
566 1124
567 * The IO::AIO::GRP objects will be cleaned up during calls to 1125 * The IO::AIO::GRP objects will be cleaned up during calls to
568 "IO::AIO::poll_cb", just like any other request. 1126 "IO::AIO::poll_cb", just like any other request.
1127
569 * They can be canceled like any other request. Canceling will cancel not 1128 * They can be canceled like any other request. Canceling will cancel
570 only the request itself, but also all requests it contains. 1129 not only the request itself, but also all requests it contains.
1130
571 * They can also can also be added to other IO::AIO::GRP objects. 1131 * They can also can also be added to other IO::AIO::GRP objects.
1132
572 * You must not add requests to a group from within the group callback 1133 * You must not add requests to a group from within the group callback
573 (or any later time). 1134 (or any later time).
574 1135
575 Their lifetime, simplified, looks like this: when they are empty, they 1136 Their lifetime, simplified, looks like this: when they are empty, they
576 will finish very quickly. If they contain only requests that are in the 1137 will finish very quickly. If they contain only requests that are in the
577 "done" state, they will also finish. Otherwise they will continue to 1138 "done" state, they will also finish. Otherwise they will continue to
578 exist. 1139 exist.
579 1140
580 That means after creating a group you have some time to add requests. 1141 That means after creating a group you have some time to add requests
581 And in the callbacks of those requests, you can add further requests to 1142 (precisely before the callback has been invoked, which is only done
582 the group. And only when all those requests have finished will the the 1143 within the "poll_cb"). And in the callbacks of those requests, you can
583 group itself finish. 1144 add further requests to the group. And only when all those requests have
1145 finished will the the group itself finish.
584 1146
585 add $grp ... 1147 add $grp ...
586 $grp->add (...) 1148 $grp->add (...)
587 Add one or more requests to the group. Any type of IO::AIO::REQ can 1149 Add one or more requests to the group. Any type of IO::AIO::REQ can
588 be added, including other groups, as long as you do not create 1150 be added, including other groups, as long as you do not create
… …
593 $grp->cancel_subs 1155 $grp->cancel_subs
594 Cancel all subrequests and clears any feeder, but not the group 1156 Cancel all subrequests and clears any feeder, but not the group
595 request itself. Useful when you queued a lot of events but got a 1157 request itself. Useful when you queued a lot of events but got a
596 result early. 1158 result early.
597 1159
1160 The group request will finish normally (you cannot add requests to
1161 the group).
1162
598 $grp->result (...) 1163 $grp->result (...)
599 Set the result value(s) that will be passed to the group callback 1164 Set the result value(s) that will be passed to the group callback
600 when all subrequests have finished and set thre groups errno to the 1165 when all subrequests have finished and set the groups errno to the
601 current value of errno (just like calling "errno" without an error 1166 current value of errno (just like calling "errno" without an error
602 number). By default, no argument will be passed and errno is zero. 1167 number). By default, no argument will be passed and errno is zero.
603 1168
604 $grp->errno ([$errno]) 1169 $grp->errno ([$errno])
605 Sets the group errno value to $errno, or the current value of errno 1170 Sets the group errno value to $errno, or the current value of errno
… …
616 Sets a feeder/generator on this group: every group can have an 1181 Sets a feeder/generator on this group: every group can have an
617 attached generator that generates requests if idle. The idea behind 1182 attached generator that generates requests if idle. The idea behind
618 this is that, although you could just queue as many requests as you 1183 this is that, although you could just queue as many requests as you
619 want in a group, this might starve other requests for a potentially 1184 want in a group, this might starve other requests for a potentially
620 long time. For example, "aio_scandir" might generate hundreds of 1185 long time. For example, "aio_scandir" might generate hundreds of
621 thousands "aio_stat" requests, delaying any later requests for a 1186 thousands of "aio_stat" requests, delaying any later requests for a
622 long time. 1187 long time.
623 1188
624 To avoid this, and allow incremental generation of requests, you can 1189 To avoid this, and allow incremental generation of requests, you can
625 instead a group and set a feeder on it that generates those 1190 instead a group and set a feeder on it that generates those
626 requests. The feed callback will be called whenever there are few 1191 requests. The feed callback will be called whenever there are few
… …
631 does not impose any limits). 1196 does not impose any limits).
632 1197
633 If the feed does not queue more requests when called, it will be 1198 If the feed does not queue more requests when called, it will be
634 automatically removed from the group. 1199 automatically removed from the group.
635 1200
636 If the feed limit is 0, it will be set to 2 automatically. 1201 If the feed limit is 0 when this method is called, it will be set to
1202 2 automatically.
637 1203
638 Example: 1204 Example:
639 1205
640 # stat all files in @files, but only ever use four aio requests concurrently: 1206 # stat all files in @files, but only ever use four aio requests concurrently:
641 1207
… …
652 Sets the feeder limit for the group: The feeder will be called 1218 Sets the feeder limit for the group: The feeder will be called
653 whenever the group contains less than this many requests. 1219 whenever the group contains less than this many requests.
654 1220
655 Setting the limit to 0 will pause the feeding process. 1221 Setting the limit to 0 will pause the feeding process.
656 1222
1223 The default value for the limit is 0, but note that setting a feeder
1224 automatically bumps it up to 2.
1225
657 SUPPORT FUNCTIONS 1226 SUPPORT FUNCTIONS
658 EVENT PROCESSING AND EVENT LOOP INTEGRATION 1227 EVENT PROCESSING AND EVENT LOOP INTEGRATION
659 $fileno = IO::AIO::poll_fileno 1228 $fileno = IO::AIO::poll_fileno
660 Return the *request result pipe file descriptor*. This filehandle 1229 Return the *request result pipe file descriptor*. This filehandle
661 must be polled for reading by some mechanism outside this module 1230 must be polled for reading by some mechanism outside this module
662 (e.g. Event or select, see below or the SYNOPSIS). If the pipe 1231 (e.g. EV, Glib, select and so on, see below or the SYNOPSIS). If the
663 becomes readable you have to call "poll_cb" to check the results. 1232 pipe becomes readable you have to call "poll_cb" to check the
1233 results.
664 1234
665 See "poll_cb" for an example. 1235 See "poll_cb" for an example.
666 1236
667 IO::AIO::poll_cb 1237 IO::AIO::poll_cb
668 Process some outstanding events on the result pipe. You have to call 1238 Process some outstanding events on the result pipe. You have to call
669 this regularly. Returns the number of events processed. Returns 1239 this regularly. Returns 0 if all events could be processed (or there
670 immediately when no events are outstanding. The amount of events 1240 were no events to process), or -1 if it returned earlier for
671 processed depends on the settings of "IO::AIO::max_poll_req" and 1241 whatever reason. Returns immediately when no events are outstanding.
672 "IO::AIO::max_poll_time". 1242 The amount of events processed depends on the settings of
1243 "IO::AIO::max_poll_req" and "IO::AIO::max_poll_time".
673 1244
674 If not all requests were processed for whatever reason, the 1245 If not all requests were processed for whatever reason, the
675 filehandle will still be ready when "poll_cb" returns. 1246 filehandle will still be ready when "poll_cb" returns, so normally
1247 you don't have to do anything special to have it called later.
1248
1249 Apart from calling "IO::AIO::poll_cb" when the event filehandle
1250 becomes ready, it can be beneficial to call this function from loops
1251 which submit a lot of requests, to make sure the results get
1252 processed when they become available and not just when the loop is
1253 finished and the event loop takes over again. This function returns
1254 very fast when there are no outstanding requests.
676 1255
677 Example: Install an Event watcher that automatically calls 1256 Example: Install an Event watcher that automatically calls
678 IO::AIO::poll_cb with high priority: 1257 IO::AIO::poll_cb with high priority (more examples can be found in
1258 the SYNOPSIS section, at the top of this document):
679 1259
680 Event->io (fd => IO::AIO::poll_fileno, 1260 Event->io (fd => IO::AIO::poll_fileno,
681 poll => 'r', async => 1, 1261 poll => 'r', async => 1,
682 cb => \&IO::AIO::poll_cb); 1262 cb => \&IO::AIO::poll_cb);
1263
1264 IO::AIO::poll_wait
1265 If there are any outstanding requests and none of them in the result
1266 phase, wait till the result filehandle becomes ready for reading
1267 (simply does a "select" on the filehandle. This is useful if you
1268 want to synchronously wait for some requests to finish).
1269
1270 See "nreqs" for an example.
1271
1272 IO::AIO::poll
1273 Waits until some requests have been handled.
1274
1275 Returns the number of requests processed, but is otherwise strictly
1276 equivalent to:
1277
1278 IO::AIO::poll_wait, IO::AIO::poll_cb
1279
1280 IO::AIO::flush
1281 Wait till all outstanding AIO requests have been handled.
1282
1283 Strictly equivalent to:
1284
1285 IO::AIO::poll_wait, IO::AIO::poll_cb
1286 while IO::AIO::nreqs;
683 1287
684 IO::AIO::max_poll_reqs $nreqs 1288 IO::AIO::max_poll_reqs $nreqs
685 IO::AIO::max_poll_time $seconds 1289 IO::AIO::max_poll_time $seconds
686 These set the maximum number of requests (default 0, meaning 1290 These set the maximum number of requests (default 0, meaning
687 infinity) that are being processed by "IO::AIO::poll_cb" in one 1291 infinity) that are being processed by "IO::AIO::poll_cb" in one
… …
711 # use a low priority so other tasks have priority 1315 # use a low priority so other tasks have priority
712 Event->io (fd => IO::AIO::poll_fileno, 1316 Event->io (fd => IO::AIO::poll_fileno,
713 poll => 'r', nice => 1, 1317 poll => 'r', nice => 1,
714 cb => &IO::AIO::poll_cb); 1318 cb => &IO::AIO::poll_cb);
715 1319
716 IO::AIO::poll_wait
717 If there are any outstanding requests and none of them in the result
718 phase, wait till the result filehandle becomes ready for reading
719 (simply does a "select" on the filehandle. This is useful if you
720 want to synchronously wait for some requests to finish).
721
722 See "nreqs" for an example.
723
724 IO::AIO::poll
725 Waits until some requests have been handled.
726
727 Returns the number of requests processed, but is otherwise strictly
728 equivalent to:
729
730 IO::AIO::poll_wait, IO::AIO::poll_cb
731
732 IO::AIO::flush
733 Wait till all outstanding AIO requests have been handled.
734
735 Strictly equivalent to:
736
737 IO::AIO::poll_wait, IO::AIO::poll_cb
738 while IO::AIO::nreqs;
739
740 CONTROLLING THE NUMBER OF THREADS 1320 CONTROLLING THE NUMBER OF THREADS
741 IO::AIO::min_parallel $nthreads 1321 IO::AIO::min_parallel $nthreads
742 Set the minimum number of AIO threads to $nthreads. The current 1322 Set the minimum number of AIO threads to $nthreads. The current
743 default is 8, which means eight asynchronous operations can execute 1323 default is 8, which means eight asynchronous operations can execute
744 concurrently at any one time (the number of outstanding requests, 1324 concurrently at any one time (the number of outstanding requests,
… …
773 1353
774 Under normal circumstances you don't need to call this function. 1354 Under normal circumstances you don't need to call this function.
775 1355
776 IO::AIO::max_idle $nthreads 1356 IO::AIO::max_idle $nthreads
777 Limit the number of threads (default: 4) that are allowed to idle 1357 Limit the number of threads (default: 4) that are allowed to idle
778 (i.e., threads that did not get a request to process within 10 1358 (i.e., threads that did not get a request to process within the idle
779 seconds). That means if a thread becomes idle while $nthreads other 1359 timeout (default: 10 seconds). That means if a thread becomes idle
780 threads are also idle, it will free its resources and exit. 1360 while $nthreads other threads are also idle, it will free its
1361 resources and exit.
781 1362
782 This is useful when you allow a large number of threads (e.g. 100 or 1363 This is useful when you allow a large number of threads (e.g. 100 or
783 1000) to allow for extremely high load situations, but want to free 1364 1000) to allow for extremely high load situations, but want to free
784 resources under normal circumstances (1000 threads can easily 1365 resources under normal circumstances (1000 threads can easily
785 consume 30MB of RAM). 1366 consume 30MB of RAM).
786 1367
787 The default is probably ok in most situations, especially if thread 1368 The default is probably ok in most situations, especially if thread
788 creation is fast. If thread creation is very slow on your system you 1369 creation is fast. If thread creation is very slow on your system you
789 might want to use larger values. 1370 might want to use larger values.
790 1371
1372 IO::AIO::idle_timeout $seconds
1373 Sets the minimum idle timeout (default 10) after which worker
1374 threads are allowed to exit. SEe "IO::AIO::max_idle".
1375
791 $oldmaxreqs = IO::AIO::max_outstanding $maxreqs 1376 IO::AIO::max_outstanding $maxreqs
1377 Sets the maximum number of outstanding requests to $nreqs. If you do
1378 queue up more than this number of requests, the next call to
1379 "IO::AIO::poll_cb" (and other functions calling "poll_cb", such as
1380 "IO::AIO::flush" or "IO::AIO::poll") will block until the limit is
1381 no longer exceeded.
1382
1383 In other words, this setting does not enforce a queue limit, but can
1384 be used to make poll functions block if the limit is exceeded.
1385
792 This is a very bad function to use in interactive programs because 1386 This is a very bad function to use in interactive programs because
793 it blocks, and a bad way to reduce concurrency because it is 1387 it blocks, and a bad way to reduce concurrency because it is
794 inexact: Better use an "aio_group" together with a feed callback. 1388 inexact: Better use an "aio_group" together with a feed callback.
795 1389
796 Sets the maximum number of outstanding requests to $nreqs. If you to 1390 It's main use is in scripts without an event loop - when you want to
797 queue up more than this number of requests, the next call to the 1391 stat a lot of files, you can write somehting like this:
798 "poll_cb" (and "poll_some" and other functions calling "poll_cb")
799 function will block until the limit is no longer exceeded.
800 1392
801 The default value is very large, so there is no practical limit on 1393 IO::AIO::max_outstanding 32;
1394
1395 for my $path (...) {
1396 aio_stat $path , ...;
1397 IO::AIO::poll_cb;
1398 }
1399
1400 IO::AIO::flush;
1401
1402 The call to "poll_cb" inside the loop will normally return
1403 instantly, but as soon as more thna 32 reqeusts are in-flight, it
1404 will block until some requests have been handled. This keeps the
1405 loop from pushing a large number of "aio_stat" requests onto the
1406 queue.
1407
1408 The default value for "max_outstanding" is very large, so there is
802 the number of outstanding requests. 1409 no practical limit on the number of outstanding requests.
803
804 You can still queue as many requests as you want. Therefore,
805 "max_oustsanding" is mainly useful in simple scripts (with low
806 values) or as a stop gap to shield against fatal memory overflow
807 (with large values).
808 1410
809 STATISTICAL INFORMATION 1411 STATISTICAL INFORMATION
810 IO::AIO::nreqs 1412 IO::AIO::nreqs
811 Returns the number of requests currently in the ready, execute or 1413 Returns the number of requests currently in the ready, execute or
812 pending states (i.e. for which their callback has not been invoked 1414 pending states (i.e. for which their callback has not been invoked
… …
823 1425
824 IO::AIO::npending 1426 IO::AIO::npending
825 Returns the number of requests currently in the pending state 1427 Returns the number of requests currently in the pending state
826 (executed, but not yet processed by poll_cb). 1428 (executed, but not yet processed by poll_cb).
827 1429
1430 MISCELLANEOUS FUNCTIONS
1431 IO::AIO implements some functions that might be useful, but are not
1432 asynchronous.
1433
1434 IO::AIO::sendfile $ofh, $ifh, $offset, $count
1435 Calls the "eio_sendfile_sync" function, which is like
1436 "aio_sendfile", but is blocking (this makes most sense if you know
1437 the input data is likely cached already and the output filehandle is
1438 set to non-blocking operations).
1439
1440 Returns the number of bytes copied, or -1 on error.
1441
1442 IO::AIO::fadvise $fh, $offset, $len, $advice
1443 Simply calls the "posix_fadvise" function (see its manpage for
1444 details). The following advice constants are available:
1445 "IO::AIO::FADV_NORMAL", "IO::AIO::FADV_SEQUENTIAL",
1446 "IO::AIO::FADV_RANDOM", "IO::AIO::FADV_NOREUSE",
1447 "IO::AIO::FADV_WILLNEED", "IO::AIO::FADV_DONTNEED".
1448
1449 On systems that do not implement "posix_fadvise", this function
1450 returns ENOSYS, otherwise the return value of "posix_fadvise".
1451
1452 IO::AIO::madvise $scalar, $offset, $len, $advice
1453 Simply calls the "posix_madvise" function (see its manpage for
1454 details). The following advice constants are available:
1455 "IO::AIO::MADV_NORMAL", "IO::AIO::MADV_SEQUENTIAL",
1456 "IO::AIO::MADV_RANDOM", "IO::AIO::MADV_WILLNEED",
1457 "IO::AIO::MADV_DONTNEED".
1458
1459 On systems that do not implement "posix_madvise", this function
1460 returns ENOSYS, otherwise the return value of "posix_madvise".
1461
1462 IO::AIO::mprotect $scalar, $offset, $len, $protect
1463 Simply calls the "mprotect" function on the preferably AIO::mmap'ed
1464 $scalar (see its manpage for details). The following protect
1465 constants are available: "IO::AIO::PROT_NONE", "IO::AIO::PROT_READ",
1466 "IO::AIO::PROT_WRITE", "IO::AIO::PROT_EXEC".
1467
1468 On systems that do not implement "mprotect", this function returns
1469 ENOSYS, otherwise the return value of "mprotect".
1470
1471 IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
1472 Memory-maps a file (or anonymous memory range) and attaches it to
1473 the given $scalar, which will act like a string scalar.
1474
1475 The only operations allowed on the scalar are "substr"/"vec" that
1476 don't change the string length, and most read-only operations such
1477 as copying it or searching it with regexes and so on.
1478
1479 Anything else is unsafe and will, at best, result in memory leaks.
1480
1481 The memory map associated with the $scalar is automatically removed
1482 when the $scalar is destroyed, or when the "IO::AIO::mmap" or
1483 "IO::AIO::munmap" functions are called.
1484
1485 This calls the "mmap"(2) function internally. See your system's
1486 manual page for details on the $length, $prot and $flags parameters.
1487
1488 The $length must be larger than zero and smaller than the actual
1489 filesize.
1490
1491 $prot is a combination of "IO::AIO::PROT_NONE",
1492 "IO::AIO::PROT_EXEC", "IO::AIO::PROT_READ" and/or
1493 "IO::AIO::PROT_WRITE",
1494
1495 $flags can be a combination of "IO::AIO::MAP_SHARED" or
1496 "IO::AIO::MAP_PRIVATE", or a number of system-specific flags (when
1497 not available, the are defined as 0): "IO::AIO::MAP_ANONYMOUS"
1498 (which is set to "MAP_ANON" if your system only provides this
1499 constant), "IO::AIO::MAP_HUGETLB", "IO::AIO::MAP_LOCKED",
1500 "IO::AIO::MAP_NORESERVE", "IO::AIO::MAP_POPULATE" or
1501 "IO::AIO::MAP_NONBLOCK"
1502
1503 If $fh is "undef", then a file descriptor of -1 is passed.
1504
1505 $offset is the offset from the start of the file - it generally must
1506 be a multiple of "IO::AIO::PAGESIZE" and defaults to 0.
1507
1508 Example:
1509
1510 use Digest::MD5;
1511 use IO::AIO;
1512
1513 open my $fh, "<verybigfile"
1514 or die "$!";
1515
1516 IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
1517 or die "verybigfile: $!";
1518
1519 my $fast_md5 = md5 $data;
1520
1521 IO::AIO::munmap $scalar
1522 Removes a previous mmap and undefines the $scalar.
1523
1524 IO::AIO::munlock $scalar, $offset = 0, $length = undef
1525 Calls the "munlock" function, undoing the effects of a previous
1526 "aio_mlock" call (see its description for details).
1527
1528 IO::AIO::munlockall
1529 Calls the "munlockall" function.
1530
1531 On systems that do not implement "munlockall", this function returns
1532 ENOSYS, otherwise the return value of "munlockall".
1533
1534EVENT LOOP INTEGRATION
1535 It is recommended to use AnyEvent::AIO to integrate IO::AIO
1536 automatically into many event loops:
1537
1538 # AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
1539 use AnyEvent::AIO;
1540
1541 You can also integrate IO::AIO manually into many event loops, here are
1542 some examples of how to do this:
1543
1544 # EV integration
1545 my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
1546
1547 # Event integration
1548 Event->io (fd => IO::AIO::poll_fileno,
1549 poll => 'r',
1550 cb => \&IO::AIO::poll_cb);
1551
1552 # Glib/Gtk2 integration
1553 add_watch Glib::IO IO::AIO::poll_fileno,
1554 in => sub { IO::AIO::poll_cb; 1 };
1555
1556 # Tk integration
1557 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
1558 readable => \&IO::AIO::poll_cb);
1559
1560 # Danga::Socket integration
1561 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
1562 \&IO::AIO::poll_cb);
1563
828 FORK BEHAVIOUR 1564 FORK BEHAVIOUR
829 This module should do "the right thing" when the process using it forks: 1565 Usage of pthreads in a program changes the semantics of fork
1566 considerably. Specifically, only async-safe functions can be called
1567 after fork. Perl doesn't know about this, so in general, you cannot call
1568 fork with defined behaviour in perl if pthreads are involved. IO::AIO
1569 uses pthreads, so this applies, but many other extensions and (for
1570 inexplicable reasons) perl itself often is linked against pthreads, so
1571 this limitation applies to quite a lot of perls.
830 1572
831 Before the fork, IO::AIO enters a quiescent state where no requests can 1573 This module no longer tries to fight your OS, or POSIX. That means
832 be added in other threads and no results will be processed. After the 1574 IO::AIO only works in the process that loaded it. Forking is fully
833 fork the parent simply leaves the quiescent state and continues 1575 supported, but using IO::AIO in the child is not.
834 request/result processing, while the child frees the request/result
835 queue (so that the requests started before the fork will only be handled
836 in the parent). Threads will be started on demand until the limit set in
837 the parent process has been reached again.
838 1576
839 In short: the parent will, after a short pause, continue as if fork had 1577 You might get around by not *using* IO::AIO before (or after) forking.
840 not been called, while the child will act as if IO::AIO has not been 1578 You could also try to call the IO::AIO::reinit function in the child:
841 used yet. 1579
1580 IO::AIO::reinit
1581 Abandons all current requests and I/O threads and simply
1582 reinitialises all data structures. This is not an operation
1583 supported by any standards, but happens to work on GNU/Linux and
1584 some newer BSD systems.
1585
1586 The only reasonable use for this function is to call it after
1587 forking, if "IO::AIO" was used in the parent. Calling it while
1588 IO::AIO is active in the process will result in undefined behaviour.
1589 Calling it at any time will also result in any undefined (by POSIX)
1590 behaviour.
842 1591
843 MEMORY USAGE 1592 MEMORY USAGE
844 Per-request usage: 1593 Per-request usage:
845 1594
846 Each aio request uses - depending on your architecture - around 100-200 1595 Each aio request uses - depending on your architecture - around 100-200
847 bytes of memory. In addition, stat requests need a stat buffer (possibly 1596 bytes of memory. In addition, stat requests need a stat buffer (possibly
848 a few hundred bytes), readdir requires a result buffer and so on. Perl 1597 a few hundred bytes), readdir requires a result buffer and so on. Perl
849 scalars and other data passed into aio requests will also be locked and 1598 scalars and other data passed into aio requests will also be locked and
850 will consume memory till the request has entered the done state. 1599 will consume memory till the request has entered the done state.
851 1600
852 This is now awfully much, so queuing lots of requests is not usually a 1601 This is not awfully much, so queuing lots of requests is not usually a
853 problem. 1602 problem.
854 1603
855 Per-thread usage: 1604 Per-thread usage:
856 1605
857 In the execution phase, some aio requests require more memory for 1606 In the execution phase, some aio requests require more memory for
… …
860 1609
861KNOWN BUGS 1610KNOWN BUGS
862 Known bugs will be fixed in the next release. 1611 Known bugs will be fixed in the next release.
863 1612
864SEE ALSO 1613SEE ALSO
865 Coro::AIO. 1614 AnyEvent::AIO for easy integration into event loops, Coro::AIO for a
1615 more natural syntax.
866 1616
867AUTHOR 1617AUTHOR
868 Marc Lehmann <schmorp@schmorp.de> 1618 Marc Lehmann <schmorp@schmorp.de>
869 http://home.schmorp.de/ 1619 http://home.schmorp.de/
870 1620

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