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Revision 1.52 by root, Tue Apr 10 05:01:33 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
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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.
360
361 As a GNU/Linux (and maybe Solaris) extension, also the constants
362 "IO::AIO::SEEK_DATA" and "IO::AIO::SEEK_HOLE" are available, if they
363 could be found. No guarantees about suitability for use in
364 "aio_seek" or Perl's "sysseek" can be made though, although I would
365 naively assume they "just work".
269 366
270 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval) 367 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
271 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval) 368 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
272 Reads or writes "length" bytes from the specified "fh" and "offset" 369 Reads or writes $length bytes from or to the specified $fh and
273 into the scalar given by "data" and offset "dataoffset" and calls 370 $offset into the scalar given by $data and offset $dataoffset and
274 the callback without the actual number of bytes read (or -1 on 371 calls the callback without the actual number of bytes read (or -1 on
275 error, just like the syscall). 372 error, just like the syscall).
276 373
374 "aio_read" will, like "sysread", shrink or grow the $data scalar to
375 offset plus the actual number of bytes read.
376
377 If $offset is undefined, then the current file descriptor offset
378 will be used (and updated), otherwise the file descriptor offset
379 will not be changed by these calls.
380
381 If $length is undefined in "aio_write", use the remaining length of
382 $data.
383
384 If $dataoffset is less than zero, it will be counted from the end of
385 $data.
386
277 The $data scalar *MUST NOT* be modified in any way while the request 387 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 388 is outstanding. Modifying it can result in segfaults or World War
279 necessary/optional hardware is installed). 389 III (if the necessary/optional hardware is installed).
280 390
281 Example: Read 15 bytes at offset 7 into scalar $buffer, starting at 391 Example: Read 15 bytes at offset 7 into scalar $buffer, starting at
282 offset 0 within the scalar: 392 offset 0 within the scalar:
283 393
284 aio_read $fh, 7, 15, $buffer, 0, sub { 394 aio_read $fh, 7, 15, $buffer, 0, sub {
… …
289 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval) 399 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 400 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 401 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 402 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 403 more than one "aio_sendfile" per $out_fh, as they will interfere
294 with each other. 404 with each other. The same $in_fh works fine though, as this function
405 does not move or use the file offset of $in_fh.
295 406
407 Please note that "aio_sendfile" can read more bytes from $in_fh than
408 are written, and there is no way to find out how many more bytes
409 have been read from "aio_sendfile" alone, as "aio_sendfile" only
410 provides the number of bytes written to $out_fh. Only if the result
411 value equals $length one can assume that $length bytes have been
412 read.
413
414 Unlike with other "aio_" functions, it makes a lot of sense to use
415 "aio_sendfile" on non-blocking sockets, as long as one end
416 (typically the $in_fh) is a file - the file I/O will then be
417 asynchronous, while the socket I/O will be non-blocking. Note,
418 however, that you can run into a trap where "aio_sendfile" reads
419 some data with readahead, then fails to write all data, and when the
420 socket is ready the next time, the data in the cache is already
421 lost, forcing "aio_sendfile" to again hit the disk. Explicit
422 "aio_read" + "aio_write" let's you better control resource usage.
423
296 This call tries to make use of a native "sendfile" syscall to 424 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 425 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. 426 to a socket, and $in_fh should refer to an mmap'able file.
299 427
300 If the native sendfile call fails or is not implemented, it will be 428 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 429 "EINVAL", "ENOTSUP", "EOPNOTSUPP", "EAFNOSUPPORT", "EPROTOTYPE" or
302 regardless of the limitations of the operating system. 430 "ENOTSOCK", it will be emulated, so you can call "aio_sendfile" on
431 any type of filehandle regardless of the limitations of the
432 operating system.
303 433
304 Please note, however, that "aio_sendfile" can read more bytes from 434 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 435 hacked together in a hurry to improve benchmark numbers) tend to be
306 bytes have been read from "aio_sendfile" alone, as "aio_sendfile" 436 rather buggy on many systems, this implementation tries to work
307 only provides the number of bytes written to $out_fh. Only if the 437 around some known bugs in Linux and FreeBSD kernels (probably
308 result value equals $length one can assume that $length bytes have 438 others, too), but that might fail, so you really really should check
309 been read. 439 the return value of "aio_sendfile" - fewre bytes than expected might
440 have been transferred.
310 441
311 aio_readahead $fh,$offset,$length, $callback->($retval) 442 aio_readahead $fh,$offset,$length, $callback->($retval)
312 "aio_readahead" populates the page cache with data from a file so 443 "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 444 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 445 $offset argument specifies the starting point from which data is to
… …
335 Currently, the stats are always 64-bit-stats, i.e. instead of 466 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 467 returning an error when stat'ing a large file, the results will be
337 silently truncated unless perl itself is compiled with large file 468 silently truncated unless perl itself is compiled with large file
338 support. 469 support.
339 470
471 To help interpret the mode and dev/rdev stat values, IO::AIO offers
472 the following constants and functions (if not implemented, the
473 constants will be 0 and the functions will either "croak" or fall
474 back on traditional behaviour).
475
476 "S_IFMT", "S_IFIFO", "S_IFCHR", "S_IFBLK", "S_IFLNK", "S_IFREG",
477 "S_IFDIR", "S_IFWHT", "S_IFSOCK", "IO::AIO::major $dev_t",
478 "IO::AIO::minor $dev_t", "IO::AIO::makedev $major, $minor".
479
340 Example: Print the length of /etc/passwd: 480 Example: Print the length of /etc/passwd:
341 481
342 aio_stat "/etc/passwd", sub { 482 aio_stat "/etc/passwd", sub {
343 $_[0] and die "stat failed: $!"; 483 $_[0] and die "stat failed: $!";
344 print "size is ", -s _, "\n"; 484 print "size is ", -s _, "\n";
345 }; 485 };
346 486
487 aio_statvfs $fh_or_path, $callback->($statvfs)
488 Works like the POSIX "statvfs" or "fstatvfs" syscalls, depending on
489 whether a file handle or path was passed.
490
491 On success, the callback is passed a hash reference with the
492 following members: "bsize", "frsize", "blocks", "bfree", "bavail",
493 "files", "ffree", "favail", "fsid", "flag" and "namemax". On
494 failure, "undef" is passed.
495
496 The following POSIX IO::AIO::ST_* constants are defined: "ST_RDONLY"
497 and "ST_NOSUID".
498
499 The following non-POSIX IO::AIO::ST_* flag masks are defined to
500 their correct value when available, or to 0 on systems that do not
501 support them: "ST_NODEV", "ST_NOEXEC", "ST_SYNCHRONOUS",
502 "ST_MANDLOCK", "ST_WRITE", "ST_APPEND", "ST_IMMUTABLE",
503 "ST_NOATIME", "ST_NODIRATIME" and "ST_RELATIME".
504
505 Example: stat "/wd" and dump out the data if successful.
506
507 aio_statvfs "/wd", sub {
508 my $f = $_[0]
509 or die "statvfs: $!";
510
511 use Data::Dumper;
512 say Dumper $f;
513 };
514
515 # result:
516 {
517 bsize => 1024,
518 bfree => 4333064312,
519 blocks => 10253828096,
520 files => 2050765568,
521 flag => 4096,
522 favail => 2042092649,
523 bavail => 4333064312,
524 ffree => 2042092649,
525 namemax => 255,
526 frsize => 1024,
527 fsid => 1810
528 }
529
530 aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
531 Works like perl's "utime" function (including the special case of
532 $atime and $mtime being undef). Fractional times are supported if
533 the underlying syscalls support them.
534
535 When called with a pathname, uses utimes(2) if available, otherwise
536 utime(2). If called on a file descriptor, uses futimes(2) if
537 available, otherwise returns ENOSYS, so this is not portable.
538
539 Examples:
540
541 # set atime and mtime to current time (basically touch(1)):
542 aio_utime "path", undef, undef;
543 # set atime to current time and mtime to beginning of the epoch:
544 aio_utime "path", time, undef; # undef==0
545
546 aio_chown $fh_or_path, $uid, $gid, $callback->($status)
547 Works like perl's "chown" function, except that "undef" for either
548 $uid or $gid is being interpreted as "do not change" (but -1 can
549 also be used).
550
551 Examples:
552
553 # same as "chown root path" in the shell:
554 aio_chown "path", 0, -1;
555 # same as above:
556 aio_chown "path", 0, undef;
557
558 aio_truncate $fh_or_path, $offset, $callback->($status)
559 Works like truncate(2) or ftruncate(2).
560
561 aio_chmod $fh_or_path, $mode, $callback->($status)
562 Works like perl's "chmod" function.
563
347 aio_unlink $pathname, $callback->($status) 564 aio_unlink $pathname, $callback->($status)
348 Asynchronously unlink (delete) a file and call the callback with the 565 Asynchronously unlink (delete) a file and call the callback with the
349 result code. 566 result code.
350 567
351 aio_mknod $path, $mode, $dev, $callback->($status) 568 aio_mknod $pathname, $mode, $dev, $callback->($status)
352 [EXPERIMENTAL] 569 [EXPERIMENTAL]
353 570
354 Asynchronously create a device node (or fifo). See mknod(2). 571 Asynchronously create a device node (or fifo). See mknod(2).
355 572
356 The only (POSIX-) portable way of calling this function is: 573 The only (POSIX-) portable way of calling this function is:
357 574
358 aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ... 575 aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
576
577 See "aio_stat" for info about some potentially helpful extra
578 constants and functions.
359 579
360 aio_link $srcpath, $dstpath, $callback->($status) 580 aio_link $srcpath, $dstpath, $callback->($status)
361 Asynchronously create a new link to the existing object at $srcpath 581 Asynchronously create a new link to the existing object at $srcpath
362 at the path $dstpath and call the callback with the result code. 582 at the path $dstpath and call the callback with the result code.
363 583
364 aio_symlink $srcpath, $dstpath, $callback->($status) 584 aio_symlink $srcpath, $dstpath, $callback->($status)
365 Asynchronously create a new symbolic link to the existing object at 585 Asynchronously create a new symbolic link to the existing object at
366 $srcpath at the path $dstpath and call the callback with the result 586 $srcpath at the path $dstpath and call the callback with the result
367 code. 587 code.
368 588
369 aio_readlink $path, $callback->($link) 589 aio_readlink $pathname, $callback->($link)
370 Asynchronously read the symlink specified by $path and pass it to 590 Asynchronously read the symlink specified by $path and pass it to
371 the callback. If an error occurs, nothing or undef gets passed to 591 the callback. If an error occurs, nothing or undef gets passed to
372 the callback. 592 the callback.
373 593
594 aio_realpath $pathname, $callback->($path)
595 Asynchronously make the path absolute and resolve any symlinks in
596 $path. The resulting path only consists of directories (Same as
597 Cwd::realpath).
598
599 This request can be used to get the absolute path of the current
600 working directory by passing it a path of . (a single dot).
601
374 aio_rename $srcpath, $dstpath, $callback->($status) 602 aio_rename $srcpath, $dstpath, $callback->($status)
375 Asynchronously rename the object at $srcpath to $dstpath, just as 603 Asynchronously rename the object at $srcpath to $dstpath, just as
376 rename(2) and call the callback with the result code. 604 rename(2) and call the callback with the result code.
605
606 aio_mkdir $pathname, $mode, $callback->($status)
607 Asynchronously mkdir (create) a directory and call the callback with
608 the result code. $mode will be modified by the umask at the time the
609 request is executed, so do not change your umask.
377 610
378 aio_rmdir $pathname, $callback->($status) 611 aio_rmdir $pathname, $callback->($status)
379 Asynchronously rmdir (delete) a directory and call the callback with 612 Asynchronously rmdir (delete) a directory and call the callback with
380 the result code. 613 the result code.
381 614
382 aio_readdir $pathname, $callback->($entries) 615 aio_readdir $pathname, $callback->($entries)
383 Unlike the POSIX call of the same name, "aio_readdir" reads an 616 Unlike the POSIX call of the same name, "aio_readdir" reads an
384 entire directory (i.e. opendir + readdir + closedir). The entries 617 entire directory (i.e. opendir + readdir + closedir). The entries
385 will not be sorted, and will NOT include the "." and ".." entries. 618 will not be sorted, and will NOT include the "." and ".." entries.
386 619
387 The callback a single argument which is either "undef" or an 620 The callback is passed a single argument which is either "undef" or
388 array-ref with the filenames. 621 an array-ref with the filenames.
622
623 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
624 Quite similar to "aio_readdir", but the $flags argument allows one
625 to tune behaviour and output format. In case of an error, $entries
626 will be "undef".
627
628 The flags are a combination of the following constants, ORed
629 together (the flags will also be passed to the callback, possibly
630 modified):
631
632 IO::AIO::READDIR_DENTS
633 When this flag is off, then the callback gets an arrayref
634 consisting of names only (as with "aio_readdir"), otherwise it
635 gets an arrayref with "[$name, $type, $inode]" arrayrefs, each
636 describing a single directory entry in more detail.
637
638 $name is the name of the entry.
639
640 $type is one of the "IO::AIO::DT_xxx" constants:
641
642 "IO::AIO::DT_UNKNOWN", "IO::AIO::DT_FIFO", "IO::AIO::DT_CHR",
643 "IO::AIO::DT_DIR", "IO::AIO::DT_BLK", "IO::AIO::DT_REG",
644 "IO::AIO::DT_LNK", "IO::AIO::DT_SOCK", "IO::AIO::DT_WHT".
645
646 "IO::AIO::DT_UNKNOWN" means just that: readdir does not know. If
647 you need to know, you have to run stat yourself. Also, for speed
648 reasons, the $type scalars are read-only: you can not modify
649 them.
650
651 $inode is the inode number (which might not be exact on systems
652 with 64 bit inode numbers and 32 bit perls). This field has
653 unspecified content on systems that do not deliver the inode
654 information.
655
656 IO::AIO::READDIR_DIRS_FIRST
657 When this flag is set, then the names will be returned in an
658 order where likely directories come first, in optimal stat
659 order. This is useful when you need to quickly find directories,
660 or you want to find all directories while avoiding to stat()
661 each entry.
662
663 If the system returns type information in readdir, then this is
664 used to find directories directly. Otherwise, likely directories
665 are names beginning with ".", or otherwise names with no dots,
666 of which names with short names are tried first.
667
668 IO::AIO::READDIR_STAT_ORDER
669 When this flag is set, then the names will be returned in an
670 order suitable for stat()'ing each one. That is, when you plan
671 to stat() all files in the given directory, then the returned
672 order will likely be fastest.
673
674 If both this flag and "IO::AIO::READDIR_DIRS_FIRST" are
675 specified, then the likely dirs come first, resulting in a less
676 optimal stat order.
677
678 IO::AIO::READDIR_FOUND_UNKNOWN
679 This flag should not be set when calling "aio_readdirx".
680 Instead, it is being set by "aio_readdirx", when any of the
681 $type's found were "IO::AIO::DT_UNKNOWN". The absence of this
682 flag therefore indicates that all $type's are known, which can
683 be used to speed up some algorithms.
684
685 aio_load $pathname, $data, $callback->($status)
686 This is a composite request that tries to fully load the given file
687 into memory. Status is the same as with aio_read.
389 688
390 aio_copy $srcpath, $dstpath, $callback->($status) 689 aio_copy $srcpath, $dstpath, $callback->($status)
391 Try to copy the *file* (directories not supported as either source 690 Try to copy the *file* (directories not supported as either source
392 or destination) from $srcpath to $dstpath and call the callback with 691 or destination) from $srcpath to $dstpath and call the callback with
393 the 0 (error) or -1 ok. 692 a status of 0 (ok) or -1 (error, see $!).
394 693
395 This is a composite request that it creates the destination file 694 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 695 mode 0200 and copies the contents of the source file into it using
397 using "aio_sendfile", followed by restoring atime, mtime, access 696 "aio_sendfile", followed by restoring atime, mtime, access mode and
398 mode and uid/gid, in that order. 697 uid/gid, in that order.
399 698
400 If an error occurs, the partial destination file will be unlinked, 699 If an error occurs, the partial destination file will be unlinked,
401 if possible, except when setting atime, mtime, access mode and 700 if possible, except when setting atime, mtime, access mode and
402 uid/gid, where errors are being ignored. 701 uid/gid, where errors are being ignored.
403 702
404 aio_move $srcpath, $dstpath, $callback->($status) 703 aio_move $srcpath, $dstpath, $callback->($status)
405 Try to move the *file* (directories not supported as either source 704 Try to move the *file* (directories not supported as either source
406 or destination) from $srcpath to $dstpath and call the callback with 705 or destination) from $srcpath to $dstpath and call the callback with
407 the 0 (error) or -1 ok. 706 a status of 0 (ok) or -1 (error, see $!).
408 707
409 This is a composite request that tries to rename(2) the file first. 708 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" 709 if rename fails with "EXDEV", it copies the file with "aio_copy"
411 and, if that is successful, unlinking the $srcpath. 710 and, if that is successful, unlinks the $srcpath.
412 711
413 aio_scandir $path, $maxreq, $callback->($dirs, $nondirs) 712 aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
414 Scans a directory (similar to "aio_readdir") but additionally tries 713 Scans a directory (similar to "aio_readdir") but additionally tries
415 to efficiently separate the entries of directory $path into two sets 714 to efficiently separate the entries of directory $path into two sets
416 of names, directories you can recurse into (directories), and ones 715 of names, directories you can recurse into (directories), and ones
417 you cannot recurse into (everything else, including symlinks to 716 you cannot recurse into (everything else, including symlinks to
418 directories). 717 directories).
… …
436 Implementation notes. 735 Implementation notes.
437 736
438 The "aio_readdir" cannot be avoided, but "stat()"'ing every entry 737 The "aio_readdir" cannot be avoided, but "stat()"'ing every entry
439 can. 738 can.
440 739
740 If readdir returns file type information, then this is used directly
741 to find directories.
742
441 After reading the directory, the modification time, size etc. of the 743 Otherwise, after reading the directory, the modification time, size
442 directory before and after the readdir is checked, and if they match 744 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 745 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 746 used to decide how many entries are directories (if >= 2).
445 of the number of subdirectories will be assumed. 747 Otherwise, no knowledge of the number of subdirectories will be
748 assumed.
446 749
447 Then entries will be sorted into likely directories (everything 750 Then entries will be sorted into likely directories a non-initial
448 without a non-initial dot currently) and likely non-directories 751 dot currently) and likely non-directories (see "aio_readdirx"). Then
449 (everything else). Then every entry plus an appended "/." will be 752 every entry plus an appended "/." will be "stat"'ed, likely
450 "stat"'ed, likely directories first. If that succeeds, it assumes 753 directories first, in order of their inode numbers. If that
451 that the entry is a directory or a symlink to directory (which will 754 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 755 directory (which will be checked separately). This is often faster
453 itself because filesystems might detect the type of the entry 756 than stat'ing the entry itself because filesystems might detect the
454 without reading the inode data (e.g. ext2fs filetype feature). 757 type of the entry without reading the inode data (e.g. ext2fs
758 filetype feature), even on systems that cannot return the filetype
759 information on readdir.
455 760
456 If the known number of directories (link count - 2) has been 761 If the known number of directories (link count - 2) has been
457 reached, the rest of the entries is assumed to be non-directories. 762 reached, the rest of the entries is assumed to be non-directories.
458 763
459 This only works with certainty on POSIX (= UNIX) filesystems, which 764 This only works with certainty on POSIX (= UNIX) filesystems, which
… …
461 766
462 It will also likely work on non-POSIX filesystems with reduced 767 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 768 efficiency as those tend to return 0 or 1 as link counts, which
464 disables the directory counting heuristic. 769 disables the directory counting heuristic.
465 770
771 aio_rmtree $pathname, $callback->($status)
772 Delete a directory tree starting (and including) $path, return the
773 status of the final "rmdir" only. This is a composite request that
774 uses "aio_scandir" to recurse into and rmdir directories, and unlink
775 everything else.
776
777 aio_sync $callback->($status)
778 Asynchronously call sync and call the callback when finished.
779
466 aio_fsync $fh, $callback->($status) 780 aio_fsync $fh, $callback->($status)
467 Asynchronously call fsync on the given filehandle and call the 781 Asynchronously call fsync on the given filehandle and call the
468 callback with the fsync result code. 782 callback with the fsync result code.
469 783
470 aio_fdatasync $fh, $callback->($status) 784 aio_fdatasync $fh, $callback->($status)
471 Asynchronously call fdatasync on the given filehandle and call the 785 Asynchronously call fdatasync on the given filehandle and call the
472 callback with the fdatasync result code. 786 callback with the fdatasync result code.
473 787
474 If this call isn't available because your OS lacks it or it couldn't 788 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. 789 be detected, it will be emulated by calling "fsync" instead.
790
791 aio_syncfs $fh, $callback->($status)
792 Asynchronously call the syncfs syscall to sync the filesystem
793 associated to the given filehandle and call the callback with the
794 syncfs result code. If syncfs is not available, calls sync(), but
795 returns -1 and sets errno to "ENOSYS" nevertheless.
796
797 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
798 Sync the data portion of the file specified by $offset and $length
799 to disk (but NOT the metadata), by calling the Linux-specific
800 sync_file_range call. If sync_file_range is not available or it
801 returns ENOSYS, then fdatasync or fsync is being substituted.
802
803 $flags can be a combination of
804 "IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE",
805 "IO::AIO::SYNC_FILE_RANGE_WRITE" and
806 "IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER": refer to the sync_file_range
807 manpage for details.
808
809 aio_pathsync $pathname, $callback->($status)
810 This request tries to open, fsync and close the given path. This is
811 a composite request intended to sync directories after directory
812 operations (E.g. rename). This might not work on all operating
813 systems or have any specific effect, but usually it makes sure that
814 directory changes get written to disc. It works for anything that
815 can be opened for read-only, not just directories.
816
817 Future versions of this function might fall back to other methods
818 when "fsync" on the directory fails (such as calling "sync").
819
820 Passes 0 when everything went ok, and -1 on error.
821
822 aio_msync $scalar, $offset = 0, $length = undef, flags = 0,
823 $callback->($status)
824 This is a rather advanced IO::AIO call, which only works on
825 mmap(2)ed scalars (see the "IO::AIO::mmap" function, although it
826 also works on data scalars managed by the Sys::Mmap or Mmap modules,
827 note that the scalar must only be modified in-place while an aio
828 operation is pending on it).
829
830 It calls the "msync" function of your OS, if available, with the
831 memory area starting at $offset in the string and ending $length
832 bytes later. If $length is negative, counts from the end, and if
833 $length is "undef", then it goes till the end of the string. The
834 flags can be a combination of "IO::AIO::MS_ASYNC",
835 "IO::AIO::MS_INVALIDATE" and "IO::AIO::MS_SYNC".
836
837 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0,
838 $callback->($status)
839 This is a rather advanced IO::AIO call, which works best on
840 mmap(2)ed scalars.
841
842 It touches (reads or writes) all memory pages in the specified range
843 inside the scalar. All caveats and parameters are the same as for
844 "aio_msync", above, except for flags, which must be either 0 (which
845 reads all pages and ensures they are instantiated) or
846 "IO::AIO::MT_MODIFY", which modifies the memory page s(by reading
847 and writing an octet from it, which dirties the page).
848
849 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
850 This is a rather advanced IO::AIO call, which works best on
851 mmap(2)ed scalars.
852
853 It reads in all the pages of the underlying storage into memory (if
854 any) and locks them, so they are not getting swapped/paged out or
855 removed.
856
857 If $length is undefined, then the scalar will be locked till the
858 end.
859
860 On systems that do not implement "mlock", this function returns -1
861 and sets errno to "ENOSYS".
862
863 Note that the corresponding "munlock" is synchronous and is
864 documented under "MISCELLANEOUS FUNCTIONS".
865
866 Example: open a file, mmap and mlock it - both will be undone when
867 $data gets destroyed.
868
869 open my $fh, "<", $path or die "$path: $!";
870 my $data;
871 IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
872 aio_mlock $data; # mlock in background
873
874 aio_mlockall $flags, $callback->($status)
875 Calls the "mlockall" function with the given $flags (a combination
876 of "IO::AIO::MCL_CURRENT" and "IO::AIO::MCL_FUTURE").
877
878 On systems that do not implement "mlockall", this function returns
879 -1 and sets errno to "ENOSYS".
880
881 Note that the corresponding "munlockall" is synchronous and is
882 documented under "MISCELLANEOUS FUNCTIONS".
883
884 Example: asynchronously lock all current and future pages into
885 memory.
886
887 aio_mlockall IO::AIO::MCL_FUTURE;
888
889 aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
890 Queries the extents of the given file (by calling the Linux FIEMAP
891 ioctl, see <http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for
892 details). If the "ioctl" is not available on your OS, then this
893 rquiest will fail with "ENOSYS".
894
895 $start is the starting offset to query extents for, $length is the
896 size of the range to query - if it is "undef", then the whole file
897 will be queried.
898
899 $flags is a combination of flags ("IO::AIO::FIEMAP_FLAG_SYNC" or
900 "IO::AIO::FIEMAP_FLAG_XATTR" - "IO::AIO::FIEMAP_FLAGS_COMPAT" is
901 also exported), and is normally 0 or "IO::AIO::FIEMAP_FLAG_SYNC" to
902 query the data portion.
903
904 $count is the maximum number of extent records to return. If it is
905 "undef", then IO::AIO queries all extents of the file. As a very
906 special case, if it is 0, then the callback receives the number of
907 extents instead of the extents themselves.
908
909 If an error occurs, the callback receives no arguments. The special
910 "errno" value "IO::AIO::EBADR" is available to test for flag errors.
911
912 Otherwise, the callback receives an array reference with extent
913 structures. Each extent structure is an array reference itself, with
914 the following members:
915
916 [$logical, $physical, $length, $flags]
917
918 Flags is any combination of the following flag values (typically
919 either 0 or "IO::AIO::FIEMAP_EXTENT_LAST"):
920
921 "IO::AIO::FIEMAP_EXTENT_LAST", "IO::AIO::FIEMAP_EXTENT_UNKNOWN",
922 "IO::AIO::FIEMAP_EXTENT_DELALLOC", "IO::AIO::FIEMAP_EXTENT_ENCODED",
923 "IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED",
924 "IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED",
925 "IO::AIO::FIEMAP_EXTENT_DATA_INLINE",
926 "IO::AIO::FIEMAP_EXTENT_DATA_TAIL",
927 "IO::AIO::FIEMAP_EXTENT_UNWRITTEN", "IO::AIO::FIEMAP_EXTENT_MERGED"
928 or "IO::AIO::FIEMAP_EXTENT_SHARED".
476 929
477 aio_group $callback->(...) 930 aio_group $callback->(...)
478 This is a very special aio request: Instead of doing something, it 931 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 932 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 933 to bundle many requests into a single, composite, request with a
… …
515 requests like sleep and file handle readable/writable, the overhead 968 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 969 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 970 not use this function except to put your application under
518 artificial I/O pressure. 971 artificial I/O pressure.
519 972
973 IO::AIO::WD - multiple working directories
974 Your process only has one current working directory, which is used by
975 all threads. This makes it hard to use relative paths (some other
976 component could call "chdir" at any time, and it is hard to control when
977 the path will be used by IO::AIO).
978
979 One solution for this is to always use absolute paths. This usually
980 works, but can be quite slow (the kernel has to walk the whole path on
981 every access), and can also be a hassle to implement.
982
983 Newer POSIX systems have a number of functions (openat, fdopendir,
984 futimensat and so on) that make it possible to specify working
985 directories per operation.
986
987 For portability, and because the clowns who "designed", or shall I
988 write, perpetrated this new interface were obviously half-drunk, this
989 abstraction cannot be perfect, though.
990
991 IO::AIO allows you to convert directory paths into a so-called
992 IO::AIO::WD object. This object stores the canonicalised, absolute
993 version of the path, and on systems that allow it, also a directory file
994 descriptor.
995
996 Everywhere where a pathname is accepted by IO::AIO (e.g. in "aio_stat"
997 or "aio_unlink"), one can specify an array reference with an IO::AIO::WD
998 object and a pathname instead (or the IO::AIO::WD object alone, which
999 gets interpreted as "[$wd, "."]"). If the pathname is absolute, the
1000 IO::AIO::WD object is ignored, otherwise the pathname is resolved
1001 relative to that IO::AIO::WD object.
1002
1003 For example, to get a wd object for /etc and then stat passwd inside,
1004 you would write:
1005
1006 aio_wd "/etc", sub {
1007 my $etcdir = shift;
1008
1009 # although $etcdir can be undef on error, there is generally no reason
1010 # to check for errors here, as aio_stat will fail with ENOENT
1011 # when $etcdir is undef.
1012
1013 aio_stat [$etcdir, "passwd"], sub {
1014 # yay
1015 };
1016 };
1017
1018 That "aio_wd" is a request and not a normal function shows that creating
1019 an IO::AIO::WD object is itself a potentially blocking operation, which
1020 is why it is done asynchronously.
1021
1022 To stat the directory obtained with "aio_wd" above, one could write
1023 either of the following three request calls:
1024
1025 aio_lstat "/etc" , sub { ... # pathname as normal string
1026 aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
1027 aio_lstat $wd , sub { ... # shorthand for the previous
1028
1029 As with normal pathnames, IO::AIO keeps a copy of the working directory
1030 object and the pathname string, so you could write the following without
1031 causing any issues due to $path getting reused:
1032
1033 my $path = [$wd, undef];
1034
1035 for my $name (qw(abc def ghi)) {
1036 $path->[1] = $name;
1037 aio_stat $path, sub {
1038 # ...
1039 };
1040 }
1041
1042 There are some caveats: when directories get renamed (or deleted), the
1043 pathname string doesn't change, so will point to the new directory (or
1044 nowhere at all), while the directory fd, if available on the system,
1045 will still point to the original directory. Most functions accepting a
1046 pathname will use the directory fd on newer systems, and the string on
1047 older systems. Some functions (such as realpath) will always rely on the
1048 string form of the pathname.
1049
1050 So this fucntionality is mainly useful to get some protection against
1051 "chdir", to easily get an absolute path out of a relative path for
1052 future reference, and to speed up doing many operations in the same
1053 directory (e.g. when stat'ing all files in a directory).
1054
1055 The following functions implement this working directory abstraction:
1056
1057 aio_wd $pathname, $callback->($wd)
1058 Asynchonously canonicalise the given pathname and convert it to an
1059 IO::AIO::WD object representing it. If possible and supported on the
1060 system, also open a directory fd to speed up pathname resolution
1061 relative to this working directory.
1062
1063 If something goes wrong, then "undef" is passwd to the callback
1064 instead of a working directory object and $! is set appropriately.
1065 Since passing "undef" as working directory component of a pathname
1066 fails the request with "ENOENT", there is often no need for error
1067 checking in the "aio_wd" callback, as future requests using the
1068 value will fail in the expected way.
1069
1070 If this call isn't available because your OS lacks it or it couldn't
1071 be detected, it will be emulated by calling "fsync" instead.
1072
1073 IO::AIO::CWD
1074 This is a compiletime constant (object) that represents the process
1075 current working directory.
1076
1077 Specifying this object as working directory object for a pathname is
1078 as if the pathname would be specified directly, without a directory
1079 object, e.g., these calls are functionally identical:
1080
1081 aio_stat "somefile", sub { ... };
1082 aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
1083
520 IO::AIO::REQ CLASS 1084 IO::AIO::REQ CLASS
521 All non-aggregate "aio_*" functions return an object of this class when 1085 All non-aggregate "aio_*" functions return an object of this class when
522 called in non-void context. 1086 called in non-void context.
523 1087
524 cancel $req 1088 cancel $req
525 Cancels the request, if possible. Has the effect of skipping 1089 Cancels the request, if possible. Has the effect of skipping
526 execution when entering the execute state and skipping calling the 1090 execution when entering the execute state and skipping calling the
527 callback when entering the the result state, but will leave the 1091 callback when entering the the result state, but will leave the
528 request otherwise untouched. That means that requests that currently 1092 request otherwise untouched (with the exception of readdir). That
529 execute will not be stopped and resources held by the request will 1093 means that requests that currently execute will not be stopped and
530 not be freed prematurely. 1094 resources held by the request will not be freed prematurely.
531 1095
532 cb $req $callback->(...) 1096 cb $req $callback->(...)
533 Replace (or simply set) the callback registered to the request. 1097 Replace (or simply set) the callback registered to the request.
534 1098
535 IO::AIO::GRP CLASS 1099 IO::AIO::GRP CLASS
… …
562 }; 1126 };
563 1127
564 This makes it very easy to create composite requests (see the source of 1128 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. 1129 "aio_move" for an application) that work and feel like simple requests.
566 1130
567 * The IO::AIO::GRP objects will be cleaned up during calls to 1131 * The IO::AIO::GRP objects will be cleaned up during calls to
568 "IO::AIO::poll_cb", just like any other request. 1132 "IO::AIO::poll_cb", just like any other request.
1133
569 * They can be canceled like any other request. Canceling will cancel not 1134 * They can be canceled like any other request. Canceling will cancel
570 only the request itself, but also all requests it contains. 1135 not only the request itself, but also all requests it contains.
1136
571 * They can also can also be added to other IO::AIO::GRP objects. 1137 * They can also can also be added to other IO::AIO::GRP objects.
1138
572 * You must not add requests to a group from within the group callback 1139 * You must not add requests to a group from within the group callback
573 (or any later time). 1140 (or any later time).
574 1141
575 Their lifetime, simplified, looks like this: when they are empty, they 1142 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 1143 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 1144 "done" state, they will also finish. Otherwise they will continue to
578 exist. 1145 exist.
579 1146
580 That means after creating a group you have some time to add requests. 1147 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 1148 (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 1149 within the "poll_cb"). And in the callbacks of those requests, you can
583 group itself finish. 1150 add further requests to the group. And only when all those requests have
1151 finished will the the group itself finish.
584 1152
585 add $grp ... 1153 add $grp ...
586 $grp->add (...) 1154 $grp->add (...)
587 Add one or more requests to the group. Any type of IO::AIO::REQ can 1155 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 1156 be added, including other groups, as long as you do not create
… …
593 $grp->cancel_subs 1161 $grp->cancel_subs
594 Cancel all subrequests and clears any feeder, but not the group 1162 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 1163 request itself. Useful when you queued a lot of events but got a
596 result early. 1164 result early.
597 1165
1166 The group request will finish normally (you cannot add requests to
1167 the group).
1168
598 $grp->result (...) 1169 $grp->result (...)
599 Set the result value(s) that will be passed to the group callback 1170 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 1171 when all subrequests have finished and set the groups errno to the
601 current value of errno (just like calling "errno" without an error 1172 current value of errno (just like calling "errno" without an error
602 number). By default, no argument will be passed and errno is zero. 1173 number). By default, no argument will be passed and errno is zero.
603 1174
604 $grp->errno ([$errno]) 1175 $grp->errno ([$errno])
605 Sets the group errno value to $errno, or the current value of errno 1176 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 1187 Sets a feeder/generator on this group: every group can have an
617 attached generator that generates requests if idle. The idea behind 1188 attached generator that generates requests if idle. The idea behind
618 this is that, although you could just queue as many requests as you 1189 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 1190 want in a group, this might starve other requests for a potentially
620 long time. For example, "aio_scandir" might generate hundreds of 1191 long time. For example, "aio_scandir" might generate hundreds of
621 thousands "aio_stat" requests, delaying any later requests for a 1192 thousands of "aio_stat" requests, delaying any later requests for a
622 long time. 1193 long time.
623 1194
624 To avoid this, and allow incremental generation of requests, you can 1195 To avoid this, and allow incremental generation of requests, you can
625 instead a group and set a feeder on it that generates those 1196 instead a group and set a feeder on it that generates those
626 requests. The feed callback will be called whenever there are few 1197 requests. The feed callback will be called whenever there are few
… …
631 does not impose any limits). 1202 does not impose any limits).
632 1203
633 If the feed does not queue more requests when called, it will be 1204 If the feed does not queue more requests when called, it will be
634 automatically removed from the group. 1205 automatically removed from the group.
635 1206
636 If the feed limit is 0, it will be set to 2 automatically. 1207 If the feed limit is 0 when this method is called, it will be set to
1208 2 automatically.
637 1209
638 Example: 1210 Example:
639 1211
640 # stat all files in @files, but only ever use four aio requests concurrently: 1212 # stat all files in @files, but only ever use four aio requests concurrently:
641 1213
… …
652 Sets the feeder limit for the group: The feeder will be called 1224 Sets the feeder limit for the group: The feeder will be called
653 whenever the group contains less than this many requests. 1225 whenever the group contains less than this many requests.
654 1226
655 Setting the limit to 0 will pause the feeding process. 1227 Setting the limit to 0 will pause the feeding process.
656 1228
1229 The default value for the limit is 0, but note that setting a feeder
1230 automatically bumps it up to 2.
1231
657 SUPPORT FUNCTIONS 1232 SUPPORT FUNCTIONS
658 EVENT PROCESSING AND EVENT LOOP INTEGRATION 1233 EVENT PROCESSING AND EVENT LOOP INTEGRATION
659 $fileno = IO::AIO::poll_fileno 1234 $fileno = IO::AIO::poll_fileno
660 Return the *request result pipe file descriptor*. This filehandle 1235 Return the *request result pipe file descriptor*. This filehandle
661 must be polled for reading by some mechanism outside this module 1236 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 1237 (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. 1238 pipe becomes readable you have to call "poll_cb" to check the
1239 results.
664 1240
665 See "poll_cb" for an example. 1241 See "poll_cb" for an example.
666 1242
667 IO::AIO::poll_cb 1243 IO::AIO::poll_cb
668 Process some outstanding events on the result pipe. You have to call 1244 Process some outstanding events on the result pipe. You have to call
669 this regularly. Returns the number of events processed. Returns 1245 this regularly. Returns 0 if all events could be processed (or there
670 immediately when no events are outstanding. The amount of events 1246 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 1247 whatever reason. Returns immediately when no events are outstanding.
672 "IO::AIO::max_poll_time". 1248 The amount of events processed depends on the settings of
1249 "IO::AIO::max_poll_req" and "IO::AIO::max_poll_time".
673 1250
674 If not all requests were processed for whatever reason, the 1251 If not all requests were processed for whatever reason, the
675 filehandle will still be ready when "poll_cb" returns. 1252 filehandle will still be ready when "poll_cb" returns, so normally
1253 you don't have to do anything special to have it called later.
1254
1255 Apart from calling "IO::AIO::poll_cb" when the event filehandle
1256 becomes ready, it can be beneficial to call this function from loops
1257 which submit a lot of requests, to make sure the results get
1258 processed when they become available and not just when the loop is
1259 finished and the event loop takes over again. This function returns
1260 very fast when there are no outstanding requests.
676 1261
677 Example: Install an Event watcher that automatically calls 1262 Example: Install an Event watcher that automatically calls
678 IO::AIO::poll_cb with high priority: 1263 IO::AIO::poll_cb with high priority (more examples can be found in
1264 the SYNOPSIS section, at the top of this document):
679 1265
680 Event->io (fd => IO::AIO::poll_fileno, 1266 Event->io (fd => IO::AIO::poll_fileno,
681 poll => 'r', async => 1, 1267 poll => 'r', async => 1,
682 cb => \&IO::AIO::poll_cb); 1268 cb => \&IO::AIO::poll_cb);
1269
1270 IO::AIO::poll_wait
1271 If there are any outstanding requests and none of them in the result
1272 phase, wait till the result filehandle becomes ready for reading
1273 (simply does a "select" on the filehandle. This is useful if you
1274 want to synchronously wait for some requests to finish).
1275
1276 See "nreqs" for an example.
1277
1278 IO::AIO::poll
1279 Waits until some requests have been handled.
1280
1281 Returns the number of requests processed, but is otherwise strictly
1282 equivalent to:
1283
1284 IO::AIO::poll_wait, IO::AIO::poll_cb
1285
1286 IO::AIO::flush
1287 Wait till all outstanding AIO requests have been handled.
1288
1289 Strictly equivalent to:
1290
1291 IO::AIO::poll_wait, IO::AIO::poll_cb
1292 while IO::AIO::nreqs;
683 1293
684 IO::AIO::max_poll_reqs $nreqs 1294 IO::AIO::max_poll_reqs $nreqs
685 IO::AIO::max_poll_time $seconds 1295 IO::AIO::max_poll_time $seconds
686 These set the maximum number of requests (default 0, meaning 1296 These set the maximum number of requests (default 0, meaning
687 infinity) that are being processed by "IO::AIO::poll_cb" in one 1297 infinity) that are being processed by "IO::AIO::poll_cb" in one
… …
711 # use a low priority so other tasks have priority 1321 # use a low priority so other tasks have priority
712 Event->io (fd => IO::AIO::poll_fileno, 1322 Event->io (fd => IO::AIO::poll_fileno,
713 poll => 'r', nice => 1, 1323 poll => 'r', nice => 1,
714 cb => &IO::AIO::poll_cb); 1324 cb => &IO::AIO::poll_cb);
715 1325
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 1326 CONTROLLING THE NUMBER OF THREADS
741 IO::AIO::min_parallel $nthreads 1327 IO::AIO::min_parallel $nthreads
742 Set the minimum number of AIO threads to $nthreads. The current 1328 Set the minimum number of AIO threads to $nthreads. The current
743 default is 8, which means eight asynchronous operations can execute 1329 default is 8, which means eight asynchronous operations can execute
744 concurrently at any one time (the number of outstanding requests, 1330 concurrently at any one time (the number of outstanding requests,
… …
773 1359
774 Under normal circumstances you don't need to call this function. 1360 Under normal circumstances you don't need to call this function.
775 1361
776 IO::AIO::max_idle $nthreads 1362 IO::AIO::max_idle $nthreads
777 Limit the number of threads (default: 4) that are allowed to idle 1363 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 1364 (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 1365 timeout (default: 10 seconds). That means if a thread becomes idle
780 threads are also idle, it will free its resources and exit. 1366 while $nthreads other threads are also idle, it will free its
1367 resources and exit.
781 1368
782 This is useful when you allow a large number of threads (e.g. 100 or 1369 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 1370 1000) to allow for extremely high load situations, but want to free
784 resources under normal circumstances (1000 threads can easily 1371 resources under normal circumstances (1000 threads can easily
785 consume 30MB of RAM). 1372 consume 30MB of RAM).
786 1373
787 The default is probably ok in most situations, especially if thread 1374 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 1375 creation is fast. If thread creation is very slow on your system you
789 might want to use larger values. 1376 might want to use larger values.
790 1377
1378 IO::AIO::idle_timeout $seconds
1379 Sets the minimum idle timeout (default 10) after which worker
1380 threads are allowed to exit. SEe "IO::AIO::max_idle".
1381
791 $oldmaxreqs = IO::AIO::max_outstanding $maxreqs 1382 IO::AIO::max_outstanding $maxreqs
1383 Sets the maximum number of outstanding requests to $nreqs. If you do
1384 queue up more than this number of requests, the next call to
1385 "IO::AIO::poll_cb" (and other functions calling "poll_cb", such as
1386 "IO::AIO::flush" or "IO::AIO::poll") will block until the limit is
1387 no longer exceeded.
1388
1389 In other words, this setting does not enforce a queue limit, but can
1390 be used to make poll functions block if the limit is exceeded.
1391
792 This is a very bad function to use in interactive programs because 1392 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 1393 it blocks, and a bad way to reduce concurrency because it is
794 inexact: Better use an "aio_group" together with a feed callback. 1394 inexact: Better use an "aio_group" together with a feed callback.
795 1395
796 Sets the maximum number of outstanding requests to $nreqs. If you to 1396 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 1397 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 1398
801 The default value is very large, so there is no practical limit on 1399 IO::AIO::max_outstanding 32;
1400
1401 for my $path (...) {
1402 aio_stat $path , ...;
1403 IO::AIO::poll_cb;
1404 }
1405
1406 IO::AIO::flush;
1407
1408 The call to "poll_cb" inside the loop will normally return
1409 instantly, but as soon as more thna 32 reqeusts are in-flight, it
1410 will block until some requests have been handled. This keeps the
1411 loop from pushing a large number of "aio_stat" requests onto the
1412 queue.
1413
1414 The default value for "max_outstanding" is very large, so there is
802 the number of outstanding requests. 1415 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 1416
809 STATISTICAL INFORMATION 1417 STATISTICAL INFORMATION
810 IO::AIO::nreqs 1418 IO::AIO::nreqs
811 Returns the number of requests currently in the ready, execute or 1419 Returns the number of requests currently in the ready, execute or
812 pending states (i.e. for which their callback has not been invoked 1420 pending states (i.e. for which their callback has not been invoked
… …
823 1431
824 IO::AIO::npending 1432 IO::AIO::npending
825 Returns the number of requests currently in the pending state 1433 Returns the number of requests currently in the pending state
826 (executed, but not yet processed by poll_cb). 1434 (executed, but not yet processed by poll_cb).
827 1435
1436 MISCELLANEOUS FUNCTIONS
1437 IO::AIO implements some functions that might be useful, but are not
1438 asynchronous.
1439
1440 IO::AIO::sendfile $ofh, $ifh, $offset, $count
1441 Calls the "eio_sendfile_sync" function, which is like
1442 "aio_sendfile", but is blocking (this makes most sense if you know
1443 the input data is likely cached already and the output filehandle is
1444 set to non-blocking operations).
1445
1446 Returns the number of bytes copied, or -1 on error.
1447
1448 IO::AIO::fadvise $fh, $offset, $len, $advice
1449 Simply calls the "posix_fadvise" function (see its manpage for
1450 details). The following advice constants are available:
1451 "IO::AIO::FADV_NORMAL", "IO::AIO::FADV_SEQUENTIAL",
1452 "IO::AIO::FADV_RANDOM", "IO::AIO::FADV_NOREUSE",
1453 "IO::AIO::FADV_WILLNEED", "IO::AIO::FADV_DONTNEED".
1454
1455 On systems that do not implement "posix_fadvise", this function
1456 returns ENOSYS, otherwise the return value of "posix_fadvise".
1457
1458 IO::AIO::madvise $scalar, $offset, $len, $advice
1459 Simply calls the "posix_madvise" function (see its manpage for
1460 details). The following advice constants are available:
1461 "IO::AIO::MADV_NORMAL", "IO::AIO::MADV_SEQUENTIAL",
1462 "IO::AIO::MADV_RANDOM", "IO::AIO::MADV_WILLNEED",
1463 "IO::AIO::MADV_DONTNEED".
1464
1465 On systems that do not implement "posix_madvise", this function
1466 returns ENOSYS, otherwise the return value of "posix_madvise".
1467
1468 IO::AIO::mprotect $scalar, $offset, $len, $protect
1469 Simply calls the "mprotect" function on the preferably AIO::mmap'ed
1470 $scalar (see its manpage for details). The following protect
1471 constants are available: "IO::AIO::PROT_NONE", "IO::AIO::PROT_READ",
1472 "IO::AIO::PROT_WRITE", "IO::AIO::PROT_EXEC".
1473
1474 On systems that do not implement "mprotect", this function returns
1475 ENOSYS, otherwise the return value of "mprotect".
1476
1477 IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
1478 Memory-maps a file (or anonymous memory range) and attaches it to
1479 the given $scalar, which will act like a string scalar.
1480
1481 The only operations allowed on the scalar are "substr"/"vec" that
1482 don't change the string length, and most read-only operations such
1483 as copying it or searching it with regexes and so on.
1484
1485 Anything else is unsafe and will, at best, result in memory leaks.
1486
1487 The memory map associated with the $scalar is automatically removed
1488 when the $scalar is destroyed, or when the "IO::AIO::mmap" or
1489 "IO::AIO::munmap" functions are called.
1490
1491 This calls the "mmap"(2) function internally. See your system's
1492 manual page for details on the $length, $prot and $flags parameters.
1493
1494 The $length must be larger than zero and smaller than the actual
1495 filesize.
1496
1497 $prot is a combination of "IO::AIO::PROT_NONE",
1498 "IO::AIO::PROT_EXEC", "IO::AIO::PROT_READ" and/or
1499 "IO::AIO::PROT_WRITE",
1500
1501 $flags can be a combination of "IO::AIO::MAP_SHARED" or
1502 "IO::AIO::MAP_PRIVATE", or a number of system-specific flags (when
1503 not available, the are defined as 0): "IO::AIO::MAP_ANONYMOUS"
1504 (which is set to "MAP_ANON" if your system only provides this
1505 constant), "IO::AIO::MAP_HUGETLB", "IO::AIO::MAP_LOCKED",
1506 "IO::AIO::MAP_NORESERVE", "IO::AIO::MAP_POPULATE" or
1507 "IO::AIO::MAP_NONBLOCK"
1508
1509 If $fh is "undef", then a file descriptor of -1 is passed.
1510
1511 $offset is the offset from the start of the file - it generally must
1512 be a multiple of "IO::AIO::PAGESIZE" and defaults to 0.
1513
1514 Example:
1515
1516 use Digest::MD5;
1517 use IO::AIO;
1518
1519 open my $fh, "<verybigfile"
1520 or die "$!";
1521
1522 IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
1523 or die "verybigfile: $!";
1524
1525 my $fast_md5 = md5 $data;
1526
1527 IO::AIO::munmap $scalar
1528 Removes a previous mmap and undefines the $scalar.
1529
1530 IO::AIO::munlock $scalar, $offset = 0, $length = undef
1531 Calls the "munlock" function, undoing the effects of a previous
1532 "aio_mlock" call (see its description for details).
1533
1534 IO::AIO::munlockall
1535 Calls the "munlockall" function.
1536
1537 On systems that do not implement "munlockall", this function returns
1538 ENOSYS, otherwise the return value of "munlockall".
1539
1540 IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
1541 Calls the GNU/Linux splice(2) syscall, if available. If $r_off or
1542 $w_off are "undef", then "NULL" is passed for these, otherwise they
1543 should be the file offset.
1544
1545 The following symbol flag values are available:
1546 "IO::AIO::SPLICE_F_MOVE", "IO::AIO::SPLICE_F_NONBLOCK",
1547 "IO::AIO::SPLICE_F_MORE" and "IO::AIO::SPLICE_F_GIFT".
1548
1549 See the splice(2) manpage for details.
1550
1551 IO::AIO::tee $r_fh, $w_fh, $length, $flags
1552 Calls the GNU/Linux tee(2) syscall, see it's manpage and the
1553 description for "IO::AIO::splice" above for details.
1554
1555EVENT LOOP INTEGRATION
1556 It is recommended to use AnyEvent::AIO to integrate IO::AIO
1557 automatically into many event loops:
1558
1559 # AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
1560 use AnyEvent::AIO;
1561
1562 You can also integrate IO::AIO manually into many event loops, here are
1563 some examples of how to do this:
1564
1565 # EV integration
1566 my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
1567
1568 # Event integration
1569 Event->io (fd => IO::AIO::poll_fileno,
1570 poll => 'r',
1571 cb => \&IO::AIO::poll_cb);
1572
1573 # Glib/Gtk2 integration
1574 add_watch Glib::IO IO::AIO::poll_fileno,
1575 in => sub { IO::AIO::poll_cb; 1 };
1576
1577 # Tk integration
1578 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
1579 readable => \&IO::AIO::poll_cb);
1580
1581 # Danga::Socket integration
1582 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
1583 \&IO::AIO::poll_cb);
1584
828 FORK BEHAVIOUR 1585 FORK BEHAVIOUR
829 This module should do "the right thing" when the process using it forks: 1586 Usage of pthreads in a program changes the semantics of fork
1587 considerably. Specifically, only async-safe functions can be called
1588 after fork. Perl doesn't know about this, so in general, you cannot call
1589 fork with defined behaviour in perl if pthreads are involved. IO::AIO
1590 uses pthreads, so this applies, but many other extensions and (for
1591 inexplicable reasons) perl itself often is linked against pthreads, so
1592 this limitation applies to quite a lot of perls.
830 1593
831 Before the fork, IO::AIO enters a quiescent state where no requests can 1594 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 1595 IO::AIO only works in the process that loaded it. Forking is fully
833 fork the parent simply leaves the quiescent state and continues 1596 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 1597
839 In short: the parent will, after a short pause, continue as if fork had 1598 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 1599 You could also try to call the IO::AIO::reinit function in the child:
841 used yet. 1600
1601 IO::AIO::reinit
1602 Abandons all current requests and I/O threads and simply
1603 reinitialises all data structures. This is not an operation
1604 supported by any standards, but happens to work on GNU/Linux and
1605 some newer BSD systems.
1606
1607 The only reasonable use for this function is to call it after
1608 forking, if "IO::AIO" was used in the parent. Calling it while
1609 IO::AIO is active in the process will result in undefined behaviour.
1610 Calling it at any time will also result in any undefined (by POSIX)
1611 behaviour.
842 1612
843 MEMORY USAGE 1613 MEMORY USAGE
844 Per-request usage: 1614 Per-request usage:
845 1615
846 Each aio request uses - depending on your architecture - around 100-200 1616 Each aio request uses - depending on your architecture - around 100-200
847 bytes of memory. In addition, stat requests need a stat buffer (possibly 1617 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 1618 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 1619 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. 1620 will consume memory till the request has entered the done state.
851 1621
852 This is now awfully much, so queuing lots of requests is not usually a 1622 This is not awfully much, so queuing lots of requests is not usually a
853 problem. 1623 problem.
854 1624
855 Per-thread usage: 1625 Per-thread usage:
856 1626
857 In the execution phase, some aio requests require more memory for 1627 In the execution phase, some aio requests require more memory for
… …
860 1630
861KNOWN BUGS 1631KNOWN BUGS
862 Known bugs will be fixed in the next release. 1632 Known bugs will be fixed in the next release.
863 1633
864SEE ALSO 1634SEE ALSO
865 Coro::AIO. 1635 AnyEvent::AIO for easy integration into event loops, Coro::AIO for a
1636 more natural syntax.
866 1637
867AUTHOR 1638AUTHOR
868 Marc Lehmann <schmorp@schmorp.de> 1639 Marc Lehmann <schmorp@schmorp.de>
869 http://home.schmorp.de/ 1640 http://home.schmorp.de/
870 1641

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