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1NAME 1NAME
2 IO::AIO - Asynchronous Input/Output 2 IO::AIO - Asynchronous/Advanced Input/Output
3 3
4SYNOPSIS 4SYNOPSIS
5 use IO::AIO; 5 use IO::AIO;
6 6
7 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
8 my $fh = shift
9 or die "/etc/passwd: $!";
10 ...
11 };
12
13 aio_unlink "/tmp/file", sub { };
14
15 aio_read $fh, 30000, 1024, $buffer, 0, sub {
16 $_[0] > 0 or die "read error: $!";
17 };
18
19 # version 2+ has request and group objects
20 use IO::AIO 2;
21
22 aioreq_pri 4; # give next request a very high priority
23 my $req = aio_unlink "/tmp/file", sub { };
24 $req->cancel; # cancel request if still in queue
25
26 my $grp = aio_group sub { print "all stats done\n" };
27 add $grp aio_stat "..." for ...;
28
7DESCRIPTION 29DESCRIPTION
8 This module implements asynchronous I/O using whatever means your 30 This module implements asynchronous I/O using whatever means your
9 operating system supports. 31 operating system supports. It is implemented as an interface to "libeio"
32 (<http://software.schmorp.de/pkg/libeio.html>).
10 33
34 Asynchronous means that operations that can normally block your program
35 (e.g. reading from disk) will be done asynchronously: the operation will
36 still block, but you can do something else in the meantime. This is
37 extremely useful for programs that need to stay interactive even when
38 doing heavy I/O (GUI programs, high performance network servers etc.),
39 but can also be used to easily do operations in parallel that are
40 normally done sequentially, e.g. stat'ing many files, which is much
41 faster on a RAID volume or over NFS when you do a number of stat
42 operations concurrently.
43
44 While most of this works on all types of file descriptors (for example
45 sockets), using these functions on file descriptors that support
46 nonblocking operation (again, sockets, pipes etc.) is very inefficient.
47 Use an event loop for that (such as the EV module): IO::AIO will
48 naturally fit into such an event loop itself.
49
11 Currently, a number of threads are started that execute your read/writes 50 In this version, a number of threads are started that execute your
12 and signal their completion. You don't need thread support in your libc 51 requests and signal their completion. You don't need thread support in
13 or perl, and the threads created by this module will not be visible to 52 perl, and the threads created by this module will not be visible to
14 the pthreads library. In the future, this module might make use of the 53 perl. In the future, this module might make use of the native aio
15 native aio functions available on many operating systems. However, they 54 functions available on many operating systems. However, they are often
16 are often not well-supported (Linux doesn't allow them on normal files 55 not well-supported or restricted (GNU/Linux doesn't allow them on normal
17 currently, for example), and they would only support aio_read and 56 files currently, for example), and they would only support aio_read and
18 aio_write, so the remaining functionality would have to be implemented 57 aio_write, so the remaining functionality would have to be implemented
19 using threads anyway. 58 using threads anyway.
20 59
60 In addition to asynchronous I/O, this module also exports some rather
61 arcane interfaces, such as "madvise" or linux's "splice" system call,
62 which is why the "A" in "AIO" can also mean *advanced*.
63
21 Although the module will work with in the presence of other threads, it 64 Although the module will work in the presence of other (Perl-) threads,
22 is currently not reentrant, so use appropriate locking yourself. 65 it is currently not reentrant in any way, so use appropriate locking
66 yourself, always call "poll_cb" from within the same thread, or never
67 call "poll_cb" (or other "aio_" functions) recursively.
68
69 EXAMPLE
70 This is a simple example that uses the EV module and loads /etc/passwd
71 asynchronously:
72
73 use EV;
74 use IO::AIO;
75
76 # register the IO::AIO callback with EV
77 my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
78
79 # queue the request to open /etc/passwd
80 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
81 my $fh = shift
82 or die "error while opening: $!";
83
84 # stat'ing filehandles is generally non-blocking
85 my $size = -s $fh;
86
87 # queue a request to read the file
88 my $contents;
89 aio_read $fh, 0, $size, $contents, 0, sub {
90 $_[0] == $size
91 or die "short read: $!";
92
93 close $fh;
94
95 # file contents now in $contents
96 print $contents;
97
98 # exit event loop and program
99 EV::break;
100 };
101 };
102
103 # possibly queue up other requests, or open GUI windows,
104 # check for sockets etc. etc.
105
106 # process events as long as there are some:
107 EV::run;
108
109REQUEST ANATOMY AND LIFETIME
110 Every "aio_*" function creates a request. which is a C data structure
111 not directly visible to Perl.
112
113 If called in non-void context, every request function returns a Perl
114 object representing the request. In void context, nothing is returned,
115 which saves a bit of memory.
116
117 The perl object is a fairly standard ref-to-hash object. The hash
118 contents are not used by IO::AIO so you are free to store anything you
119 like in it.
120
121 During their existance, aio requests travel through the following
122 states, in order:
123
124 ready
125 Immediately after a request is created it is put into the ready
126 state, waiting for a thread to execute it.
127
128 execute
129 A thread has accepted the request for processing and is currently
130 executing it (e.g. blocking in read).
131
132 pending
133 The request has been executed and is waiting for result processing.
134
135 While request submission and execution is fully asynchronous, result
136 processing is not and relies on the perl interpreter calling
137 "poll_cb" (or another function with the same effect).
138
139 result
140 The request results are processed synchronously by "poll_cb".
141
142 The "poll_cb" function will process all outstanding aio requests by
143 calling their callbacks, freeing memory associated with them and
144 managing any groups they are contained in.
145
146 done
147 Request has reached the end of its lifetime and holds no resources
148 anymore (except possibly for the Perl object, but its connection to
149 the actual aio request is severed and calling its methods will
150 either do nothing or result in a runtime error).
151
152FUNCTIONS
153 QUICK OVERVIEW
154 This section simply lists the prototypes most of the functions for quick
155 reference. See the following sections for function-by-function
156 documentation.
157
158 aio_wd $pathname, $callback->($wd)
159 aio_open $pathname, $flags, $mode, $callback->($fh)
160 aio_close $fh, $callback->($status)
161 aio_seek $fh,$offset,$whence, $callback->($offs)
162 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
163 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
164 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
165 aio_readahead $fh,$offset,$length, $callback->($retval)
166 aio_stat $fh_or_path, $callback->($status)
167 aio_lstat $fh, $callback->($status)
168 aio_statvfs $fh_or_path, $callback->($statvfs)
169 aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
170 aio_chown $fh_or_path, $uid, $gid, $callback->($status)
171 aio_chmod $fh_or_path, $mode, $callback->($status)
172 aio_truncate $fh_or_path, $offset, $callback->($status)
173 aio_allocate $fh, $mode, $offset, $len, $callback->($status)
174 aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
175 aio_unlink $pathname, $callback->($status)
176 aio_mknod $pathname, $mode, $dev, $callback->($status)
177 aio_link $srcpath, $dstpath, $callback->($status)
178 aio_symlink $srcpath, $dstpath, $callback->($status)
179 aio_readlink $pathname, $callback->($link)
180 aio_realpath $pathname, $callback->($path)
181 aio_rename $srcpath, $dstpath, $callback->($status)
182 aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
183 aio_mkdir $pathname, $mode, $callback->($status)
184 aio_rmdir $pathname, $callback->($status)
185 aio_readdir $pathname, $callback->($entries)
186 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
187 IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
188 IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
189 aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
190 aio_load $pathname, $data, $callback->($status)
191 aio_copy $srcpath, $dstpath, $callback->($status)
192 aio_move $srcpath, $dstpath, $callback->($status)
193 aio_rmtree $pathname, $callback->($status)
194 aio_fcntl $fh, $cmd, $arg, $callback->($status)
195 aio_ioctl $fh, $request, $buf, $callback->($status)
196 aio_sync $callback->($status)
197 aio_syncfs $fh, $callback->($status)
198 aio_fsync $fh, $callback->($status)
199 aio_fdatasync $fh, $callback->($status)
200 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
201 aio_pathsync $pathname, $callback->($status)
202 aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
203 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
204 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
205 aio_mlockall $flags, $callback->($status)
206 aio_group $callback->(...)
207 aio_nop $callback->()
208
209 $prev_pri = aioreq_pri [$pri]
210 aioreq_nice $pri_adjust
211
212 IO::AIO::poll_wait
213 IO::AIO::poll_cb
214 IO::AIO::poll
215 IO::AIO::flush
216 IO::AIO::max_poll_reqs $nreqs
217 IO::AIO::max_poll_time $seconds
218 IO::AIO::min_parallel $nthreads
219 IO::AIO::max_parallel $nthreads
220 IO::AIO::max_idle $nthreads
221 IO::AIO::idle_timeout $seconds
222 IO::AIO::max_outstanding $maxreqs
223 IO::AIO::nreqs
224 IO::AIO::nready
225 IO::AIO::npending
226 IO::AIO::reinit
227
228 $nfd = IO::AIO::get_fdlimit
229 IO::AIO::min_fdlimit $nfd
230
231 IO::AIO::sendfile $ofh, $ifh, $offset, $count
232 IO::AIO::fadvise $fh, $offset, $len, $advice
233 IO::AIO::fexecve $fh, $argv, $envp
234
235 IO::AIO::mmap $scalar, $length, $prot, $flags[, $fh[, $offset]]
236 IO::AIO::munmap $scalar
237 IO::AIO::mremap $scalar, $new_length, $flags[, $new_address]
238 IO::AIO::madvise $scalar, $offset, $length, $advice
239 IO::AIO::mprotect $scalar, $offset, $length, $protect
240 IO::AIO::munlock $scalar, $offset = 0, $length = undef
241 IO::AIO::munlockall
242
243 # stat extensions
244 $counter = IO::AIO::st_gen
245 $seconds = IO::AIO::st_atime, IO::AIO::st_mtime, IO::AIO::st_ctime, IO::AIO::st_btime
246 ($atime, $mtime, $ctime, $btime, ...) = IO::AIO::st_xtime
247 $nanoseconds = IO::AIO::st_atimensec, IO::AIO::st_mtimensec, IO::AIO::st_ctimensec, IO::AIO::st_btimensec
248 $seconds = IO::AIO::st_btimesec
249 ($atime, $mtime, $ctime, $btime, ...) = IO::AIO::st_xtimensec
250
251 # very much unportable syscalls
252 IO::AIO::accept4 $r_fh, $sockaddr, $sockaddr_len, $flags
253 IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
254 IO::AIO::tee $r_fh, $w_fh, $length, $flags
255
256 $actual_size = IO::AIO::pipesize $r_fh[, $new_size]
257 ($rfh, $wfh) = IO::AIO::pipe2 [$flags]
258
259 $fh = IO::AIO::eventfd [$initval, [$flags]]
260 $fh = IO::AIO::memfd_create $pathname[, $flags]
261
262 $fh = IO::AIO::timerfd_create $clockid[, $flags]
263 ($cur_interval, $cur_value) = IO::AIO::timerfd_settime $fh, $flags, $new_interval, $nbw_value
264 ($cur_interval, $cur_value) = IO::AIO::timerfd_gettime $fh
265
266 $fh = IO::AIO::pidfd_open $pid[, $flags]
267 $status = IO::AIO::pidfd_send_signal $pidfh, $signal[, $siginfo[, $flags]]
268 $fh = IO::AIO::pidfd_getfd $pidfh, $targetfd[, $flags]
23 269
24 API NOTES 270 API NOTES
25 All the "aio_*" calls are more or less thin wrappers around the syscall 271 All the "aio_*" calls are more or less thin wrappers around the syscall
26 with the same name (sans "aio_"). The arguments are similar or 272 with the same name (sans "aio_"). The arguments are similar or
27 identical, and they all accept an additional $callback argument which 273 identical, and they all accept an additional (and optional) $callback
28 must be a code reference. This code reference will get called with the 274 argument which must be a code reference. This code reference will be
275 called after the syscall has been executed in an asynchronous fashion.
276 The results of the request will be passed as arguments to the callback
277 (and, if an error occured, in $!) - for most requests the syscall return
29 syscall return code (e.g. most syscalls return -1 on error, unlike perl, 278 code (e.g. most syscalls return -1 on error, unlike perl, which usually
30 which usually delivers "false") as it's sole argument when the given 279 delivers "false").
31 syscall has been executed asynchronously.
32 280
33 All functions that expect a filehandle will also accept a file 281 Some requests (such as "aio_readdir") pass the actual results and
34 descriptor. 282 communicate failures by passing "undef".
35 283
284 All functions expecting a filehandle keep a copy of the filehandle
285 internally until the request has finished.
286
287 All functions return request objects of type IO::AIO::REQ that allow
288 further manipulation of those requests while they are in-flight.
289
36 The filenames you pass to these routines *must* be absolute. The reason 290 The pathnames you pass to these routines *should* be absolute. The
37 is that at the time the request is being executed, the current working 291 reason for this is that at the time the request is being executed, the
38 directory could have changed. Alternatively, you can make sure that you 292 current working directory could have changed. Alternatively, you can
39 never change the current working directory. 293 make sure that you never change the current working directory anywhere
294 in the program and then use relative paths. You can also take advantage
295 of IO::AIOs working directory abstraction, that lets you specify paths
296 relative to some previously-opened "working directory object" - see the
297 description of the "IO::AIO::WD" class later in this document.
40 298
41 IO::AIO::min_parallel $nthreads 299 To encode pathnames as octets, either make sure you either: a) always
42 Set the minimum number of AIO threads to $nthreads. The default is 300 pass in filenames you got from outside (command line, readdir etc.)
43 1, which means a single asynchronous operation can be done at one 301 without tinkering, b) are in your native filesystem encoding, c) use the
44 time (the number of outstanding operations, however, is unlimited). 302 Encode module and encode your pathnames to the locale (or other)
303 encoding in effect in the user environment, d) use
304 Glib::filename_from_unicode on unicode filenames or e) use something
305 else to ensure your scalar has the correct contents.
45 306
46 It is recommended to keep the number of threads low, as some linux 307 This works, btw. independent of the internal UTF-8 bit, which IO::AIO
47 kernel versions will scale negatively with the number of threads 308 handles correctly whether it is set or not.
48 (higher parallelity => MUCH higher latency).
49 309
50 Under normal circumstances you don't need to call this function, as 310 AIO REQUEST FUNCTIONS
51 this module automatically starts a single async thread. 311 $prev_pri = aioreq_pri [$pri]
312 Returns the priority value that would be used for the next request
313 and, if $pri is given, sets the priority for the next aio request.
52 314
53 IO::AIO::max_parallel $nthreads 315 The default priority is 0, the minimum and maximum priorities are -4
54 Sets the maximum number of AIO threads to $nthreads. If more than 316 and 4, respectively. Requests with higher priority will be serviced
55 the specified number of threads are currently running, kill them.
56 This function blocks until the limit is reached.
57
58 This module automatically runs "max_parallel 0" at program end, to
59 ensure that all threads are killed and that there are no outstanding
60 requests. 317 first.
61 318
62 Under normal circumstances you don't need to call this function. 319 The priority will be reset to 0 after each call to one of the
320 "aio_*" functions.
63 321
64 $fileno = IO::AIO::poll_fileno 322 Example: open a file with low priority, then read something from it
65 Return the *request result pipe filehandle*. This filehandle must be 323 with higher priority so the read request is serviced before other
66 polled for reading by some mechanism outside this module (e.g. Event 324 low priority open requests (potentially spamming the cache):
67 or select, see below). If the pipe becomes readable you have to call
68 "poll_cb" to check the results.
69 325
70 See "poll_cb" for an example. 326 aioreq_pri -3;
327 aio_open ..., sub {
328 return unless $_[0];
71 329
72 IO::AIO::poll_cb 330 aioreq_pri -2;
73 Process all outstanding events on the result pipe. You have to call 331 aio_read $_[0], ..., sub {
74 this regularly. Returns the number of events processed. Returns 332 ...
75 immediately when no events are outstanding. 333 };
334 };
76 335
77 You can use Event to multiplex, e.g.: 336 aioreq_nice $pri_adjust
337 Similar to "aioreq_pri", but subtracts the given value from the
338 current priority, so the effect is cumulative.
78 339
79 Event->io (fd => IO::AIO::poll_fileno,
80 poll => 'r', async => 1,
81 cb => \&IO::AIO::poll_cb);
82
83 IO::AIO::poll_wait
84 Wait till the result filehandle becomes ready for reading (simply
85 does a select on the filehandle. This is useful if you want to
86 synchronously wait for some requests to finish).
87
88 See "nreqs" for an example.
89
90 IO::AIO::nreqs
91 Returns the number of requests currently outstanding.
92
93 Example: wait till there are no outstanding requests anymore:
94
95 IO::AIO::poll_wait, IO::AIO::poll_cb
96 while IO::AIO::nreqs;
97
98 aio_open $pathname, $flags, $mode, $callback 340 aio_open $pathname, $flags, $mode, $callback->($fh)
99 Asynchronously open or create a file and call the callback with a 341 Asynchronously open or create a file and call the callback with a
100 newly created filehandle for the file. 342 newly created filehandle for the file (or "undef" in case of an
343 error).
101 344
102 The pathname passed to "aio_open" must be absolute. See API NOTES, 345 The pathname passed to "aio_open" must be absolute. See API NOTES,
103 above, for an explanation. 346 above, for an explanation.
104 347
105 The $mode argument is a bitmask. See the "Fcntl" module for a list. 348 The $flags argument is a bitmask. See the "Fcntl" module for a list.
106 They are the same as used in "sysopen". 349 They are the same as used by "sysopen".
350
351 Likewise, $mode specifies the mode of the newly created file, if it
352 didn't exist and "O_CREAT" has been given, just like perl's
353 "sysopen", except that it is mandatory (i.e. use 0 if you don't
354 create new files, and 0666 or 0777 if you do). Note that the $mode
355 will be modified by the umask in effect then the request is being
356 executed, so better never change the umask.
107 357
108 Example: 358 Example:
109 359
110 aio_open "/etc/passwd", O_RDONLY, 0, sub { 360 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
111 if ($_[0]) { 361 if ($_[0]) {
112 print "open successful, fh is $_[0]\n"; 362 print "open successful, fh is $_[0]\n";
113 ... 363 ...
114 } else { 364 } else {
115 die "open failed: $!\n"; 365 die "open failed: $!\n";
116 } 366 }
117 }; 367 };
118 368
369 In addition to all the common open modes/flags ("O_RDONLY",
370 "O_WRONLY", "O_RDWR", "O_CREAT", "O_TRUNC", "O_EXCL" and
371 "O_APPEND"), the following POSIX and non-POSIX constants are
372 available (missing ones on your system are, as usual, 0):
373
374 "O_ASYNC", "O_DIRECT", "O_NOATIME", "O_CLOEXEC", "O_NOCTTY",
375 "O_NOFOLLOW", "O_NONBLOCK", "O_EXEC", "O_SEARCH", "O_DIRECTORY",
376 "O_DSYNC", "O_RSYNC", "O_SYNC", "O_PATH", "O_TMPFILE", "O_TTY_INIT"
377 and "O_ACCMODE".
378
119 aio_close $fh, $callback 379 aio_close $fh, $callback->($status)
120 Asynchronously close a file and call the callback with the result 380 Asynchronously close a file and call the callback with the result
121 code. *WARNING:* although accepted, you should not pass in a perl 381 code.
122 filehandle here, as perl will likely close the file descriptor
123 itself when the filehandle is destroyed. Normally, you can safely
124 call perls "close" or just let filehandles go out of scope.
125 382
383 Unfortunately, you can't do this to perl. Perl *insists* very
384 strongly on closing the file descriptor associated with the
385 filehandle itself.
386
387 Therefore, "aio_close" will not close the filehandle - instead it
388 will use dup2 to overwrite the file descriptor with the write-end of
389 a pipe (the pipe fd will be created on demand and will be cached).
390
391 Or in other words: the file descriptor will be closed, but it will
392 not be free for reuse until the perl filehandle is closed.
393
394 aio_seek $fh, $offset, $whence, $callback->($offs)
395 Seeks the filehandle to the new $offset, similarly to perl's
396 "sysseek". The $whence can use the traditional values (0 for
397 "IO::AIO::SEEK_SET", 1 for "IO::AIO::SEEK_CUR" or 2 for
398 "IO::AIO::SEEK_END").
399
400 The resulting absolute offset will be passed to the callback, or -1
401 in case of an error.
402
403 In theory, the $whence constants could be different than the
404 corresponding values from Fcntl, but perl guarantees they are the
405 same, so don't panic.
406
407 As a GNU/Linux (and maybe Solaris) extension, also the constants
408 "IO::AIO::SEEK_DATA" and "IO::AIO::SEEK_HOLE" are available, if they
409 could be found. No guarantees about suitability for use in
410 "aio_seek" or Perl's "sysseek" can be made though, although I would
411 naively assume they "just work".
412
126 aio_read $fh,$offset,$length, $data,$dataoffset,$callback 413 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
127 aio_write $fh,$offset,$length, $data,$dataoffset,$callback 414 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
128 Reads or writes "length" bytes from the specified "fh" and "offset" 415 Reads or writes $length bytes from or to the specified $fh and
129 into the scalar given by "data" and offset "dataoffset" and calls 416 $offset into the scalar given by $data and offset $dataoffset and
130 the callback without the actual number of bytes read (or -1 on 417 calls the callback with the actual number of bytes transferred (or
131 error, just like the syscall). 418 -1 on error, just like the syscall).
132 419
420 "aio_read" will, like "sysread", shrink or grow the $data scalar to
421 offset plus the actual number of bytes read.
422
423 If $offset is undefined, then the current file descriptor offset
424 will be used (and updated), otherwise the file descriptor offset
425 will not be changed by these calls.
426
427 If $length is undefined in "aio_write", use the remaining length of
428 $data.
429
430 If $dataoffset is less than zero, it will be counted from the end of
431 $data.
432
433 The $data scalar *MUST NOT* be modified in any way while the request
434 is outstanding. Modifying it can result in segfaults or World War
435 III (if the necessary/optional hardware is installed).
436
133 Example: Read 15 bytes at offset 7 into scalar $buffer, strating at 437 Example: Read 15 bytes at offset 7 into scalar $buffer, starting at
134 offset 0 within the scalar: 438 offset 0 within the scalar:
135 439
136 aio_read $fh, 7, 15, $buffer, 0, sub { 440 aio_read $fh, 7, 15, $buffer, 0, sub {
137 $_[0] >= 0 or die "read error: $!"; 441 $_[0] > 0 or die "read error: $!";
138 print "read <$buffer>\n"; 442 print "read $_[0] bytes: <$buffer>\n";
139 }; 443 };
140 444
445 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
446 Tries to copy $length bytes from $in_fh to $out_fh. It starts
447 reading at byte offset $in_offset, and starts writing at the current
448 file offset of $out_fh. Because of that, it is not safe to issue
449 more than one "aio_sendfile" per $out_fh, as they will interfere
450 with each other. The same $in_fh works fine though, as this function
451 does not move or use the file offset of $in_fh.
452
453 Please note that "aio_sendfile" can read more bytes from $in_fh than
454 are written, and there is no way to find out how many more bytes
455 have been read from "aio_sendfile" alone, as "aio_sendfile" only
456 provides the number of bytes written to $out_fh. Only if the result
457 value equals $length one can assume that $length bytes have been
458 read.
459
460 Unlike with other "aio_" functions, it makes a lot of sense to use
461 "aio_sendfile" on non-blocking sockets, as long as one end
462 (typically the $in_fh) is a file - the file I/O will then be
463 asynchronous, while the socket I/O will be non-blocking. Note,
464 however, that you can run into a trap where "aio_sendfile" reads
465 some data with readahead, then fails to write all data, and when the
466 socket is ready the next time, the data in the cache is already
467 lost, forcing "aio_sendfile" to again hit the disk. Explicit
468 "aio_read" + "aio_write" let's you better control resource usage.
469
470 This call tries to make use of a native "sendfile"-like syscall to
471 provide zero-copy operation. For this to work, $out_fh should refer
472 to a socket, and $in_fh should refer to an mmap'able file.
473
474 If a native sendfile cannot be found or it fails with "ENOSYS",
475 "EINVAL", "ENOTSUP", "EOPNOTSUPP", "EAFNOSUPPORT", "EPROTOTYPE" or
476 "ENOTSOCK", it will be emulated, so you can call "aio_sendfile" on
477 any type of filehandle regardless of the limitations of the
478 operating system.
479
480 As native sendfile syscalls (as practically any non-POSIX interface
481 hacked together in a hurry to improve benchmark numbers) tend to be
482 rather buggy on many systems, this implementation tries to work
483 around some known bugs in Linux and FreeBSD kernels (probably
484 others, too), but that might fail, so you really really should check
485 the return value of "aio_sendfile" - fewer bytes than expected might
486 have been transferred.
487
141 aio_readahead $fh,$offset,$length, $callback 488 aio_readahead $fh,$offset,$length, $callback->($retval)
142 Asynchronously reads the specified byte range into the page cache,
143 using the "readahead" syscall. If that syscall doesn't exist the
144 status will be -1 and $! is set to ENOSYS.
145
146 readahead() populates the page cache with data from a file so that 489 "aio_readahead" populates the page cache with data from a file so
147 subsequent reads from that file will not block on disk I/O. The 490 that subsequent reads from that file will not block on disk I/O. The
148 $offset argument specifies the starting point from which data is to 491 $offset argument specifies the starting point from which data is to
149 be read and $length specifies the number of bytes to be read. I/O is 492 be read and $length specifies the number of bytes to be read. I/O is
150 performed in whole pages, so that offset is effectively rounded down 493 performed in whole pages, so that offset is effectively rounded down
151 to a page boundary and bytes are read up to the next page boundary 494 to a page boundary and bytes are read up to the next page boundary
152 greater than or equal to (off-set+length). aio_readahead() does not 495 greater than or equal to (off-set+length). "aio_readahead" does not
153 read beyond the end of the file. The current file offset of the file 496 read beyond the end of the file. The current file offset of the file
154 is left unchanged. 497 is left unchanged.
155 498
499 If that syscall doesn't exist (likely if your kernel isn't Linux) it
500 will be emulated by simply reading the data, which would have a
501 similar effect.
502
156 aio_stat $fh_or_path, $callback 503 aio_stat $fh_or_path, $callback->($status)
157 aio_lstat $fh, $callback 504 aio_lstat $fh, $callback->($status)
158 Works like perl's "stat" or "lstat" in void context. The callback 505 Works almost exactly like perl's "stat" or "lstat" in void context.
159 will be called after the stat and the results will be available 506 The callback will be called after the stat and the results will be
160 using "stat _" or "-s _" etc... 507 available using "stat _" or "-s _" and other tests (with the
508 exception of "-B" and "-T").
161 509
162 The pathname passed to "aio_stat" must be absolute. See API NOTES, 510 The pathname passed to "aio_stat" must be absolute. See API NOTES,
163 above, for an explanation. 511 above, for an explanation.
164 512
165 Currently, the stats are always 64-bit-stats, i.e. instead of 513 Currently, the stats are always 64-bit-stats, i.e. instead of
166 returning an error when stat'ing a large file, the results will be 514 returning an error when stat'ing a large file, the results will be
167 silently truncated unless perl itself is compiled with large file 515 silently truncated unless perl itself is compiled with large file
168 support. 516 support.
169 517
518 To help interpret the mode and dev/rdev stat values, IO::AIO offers
519 the following constants and functions (if not implemented, the
520 constants will be 0 and the functions will either "croak" or fall
521 back on traditional behaviour).
522
523 "S_IFMT", "S_IFIFO", "S_IFCHR", "S_IFBLK", "S_IFLNK", "S_IFREG",
524 "S_IFDIR", "S_IFWHT", "S_IFSOCK", "IO::AIO::major $dev_t",
525 "IO::AIO::minor $dev_t", "IO::AIO::makedev $major, $minor".
526
527 To access higher resolution stat timestamps, see "SUBSECOND STAT
528 TIME ACCESS".
529
170 Example: Print the length of /etc/passwd: 530 Example: Print the length of /etc/passwd:
171 531
172 aio_stat "/etc/passwd", sub { 532 aio_stat "/etc/passwd", sub {
173 $_[0] and die "stat failed: $!"; 533 $_[0] and die "stat failed: $!";
174 print "size is ", -s _, "\n"; 534 print "size is ", -s _, "\n";
175 }; 535 };
176 536
537 aio_statvfs $fh_or_path, $callback->($statvfs)
538 Works like the POSIX "statvfs" or "fstatvfs" syscalls, depending on
539 whether a file handle or path was passed.
540
541 On success, the callback is passed a hash reference with the
542 following members: "bsize", "frsize", "blocks", "bfree", "bavail",
543 "files", "ffree", "favail", "fsid", "flag" and "namemax". On
544 failure, "undef" is passed.
545
546 The following POSIX IO::AIO::ST_* constants are defined: "ST_RDONLY"
547 and "ST_NOSUID".
548
549 The following non-POSIX IO::AIO::ST_* flag masks are defined to
550 their correct value when available, or to 0 on systems that do not
551 support them: "ST_NODEV", "ST_NOEXEC", "ST_SYNCHRONOUS",
552 "ST_MANDLOCK", "ST_WRITE", "ST_APPEND", "ST_IMMUTABLE",
553 "ST_NOATIME", "ST_NODIRATIME" and "ST_RELATIME".
554
555 Example: stat "/wd" and dump out the data if successful.
556
557 aio_statvfs "/wd", sub {
558 my $f = $_[0]
559 or die "statvfs: $!";
560
561 use Data::Dumper;
562 say Dumper $f;
563 };
564
565 # result:
566 {
567 bsize => 1024,
568 bfree => 4333064312,
569 blocks => 10253828096,
570 files => 2050765568,
571 flag => 4096,
572 favail => 2042092649,
573 bavail => 4333064312,
574 ffree => 2042092649,
575 namemax => 255,
576 frsize => 1024,
577 fsid => 1810
578 }
579
580 aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
581 Works like perl's "utime" function (including the special case of
582 $atime and $mtime being undef). Fractional times are supported if
583 the underlying syscalls support them.
584
585 When called with a pathname, uses utimensat(2) or utimes(2) if
586 available, otherwise utime(2). If called on a file descriptor, uses
587 futimens(2) or futimes(2) if available, otherwise returns ENOSYS, so
588 this is not portable.
589
590 Examples:
591
592 # set atime and mtime to current time (basically touch(1)):
593 aio_utime "path", undef, undef;
594 # set atime to current time and mtime to beginning of the epoch:
595 aio_utime "path", time, undef; # undef==0
596
597 aio_chown $fh_or_path, $uid, $gid, $callback->($status)
598 Works like perl's "chown" function, except that "undef" for either
599 $uid or $gid is being interpreted as "do not change" (but -1 can
600 also be used).
601
602 Examples:
603
604 # same as "chown root path" in the shell:
605 aio_chown "path", 0, -1;
606 # same as above:
607 aio_chown "path", 0, undef;
608
609 aio_truncate $fh_or_path, $offset, $callback->($status)
610 Works like truncate(2) or ftruncate(2).
611
612 aio_allocate $fh, $mode, $offset, $len, $callback->($status)
613 Allocates or frees disk space according to the $mode argument. See
614 the linux "fallocate" documentation for details.
615
616 $mode is usually 0 or "IO::AIO::FALLOC_FL_KEEP_SIZE" to allocate
617 space, or "IO::AIO::FALLOC_FL_PUNCH_HOLE |
618 IO::AIO::FALLOC_FL_KEEP_SIZE", to deallocate a file range.
619
620 IO::AIO also supports "FALLOC_FL_COLLAPSE_RANGE", to remove a range
621 (without leaving a hole), "FALLOC_FL_ZERO_RANGE", to zero a range,
622 "FALLOC_FL_INSERT_RANGE" to insert a range and
623 "FALLOC_FL_UNSHARE_RANGE" to unshare shared blocks (see your
624 fallocate(2) manpage).
625
626 The file system block size used by "fallocate" is presumably the
627 "f_bsize" returned by "statvfs", but different filesystems and
628 filetypes can dictate other limitations.
629
630 If "fallocate" isn't available or cannot be emulated (currently no
631 emulation will be attempted), passes -1 and sets $! to "ENOSYS".
632
633 aio_chmod $fh_or_path, $mode, $callback->($status)
634 Works like perl's "chmod" function.
635
177 aio_unlink $pathname, $callback 636 aio_unlink $pathname, $callback->($status)
178 Asynchronously unlink (delete) a file and call the callback with the 637 Asynchronously unlink (delete) a file and call the callback with the
179 result code. 638 result code.
180 639
640 aio_mknod $pathname, $mode, $dev, $callback->($status)
641 [EXPERIMENTAL]
642
643 Asynchronously create a device node (or fifo). See mknod(2).
644
645 The only (POSIX-) portable way of calling this function is:
646
647 aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
648
649 See "aio_stat" for info about some potentially helpful extra
650 constants and functions.
651
652 aio_link $srcpath, $dstpath, $callback->($status)
653 Asynchronously create a new link to the existing object at $srcpath
654 at the path $dstpath and call the callback with the result code.
655
656 aio_symlink $srcpath, $dstpath, $callback->($status)
657 Asynchronously create a new symbolic link to the existing object at
658 $srcpath at the path $dstpath and call the callback with the result
659 code.
660
661 aio_readlink $pathname, $callback->($link)
662 Asynchronously read the symlink specified by $path and pass it to
663 the callback. If an error occurs, nothing or undef gets passed to
664 the callback.
665
666 aio_realpath $pathname, $callback->($path)
667 Asynchronously make the path absolute and resolve any symlinks in
668 $path. The resulting path only consists of directories (same as
669 Cwd::realpath).
670
671 This request can be used to get the absolute path of the current
672 working directory by passing it a path of . (a single dot).
673
674 aio_rename $srcpath, $dstpath, $callback->($status)
675 Asynchronously rename the object at $srcpath to $dstpath, just as
676 rename(2) and call the callback with the result code.
677
678 On systems that support the AIO::WD working directory abstraction
679 natively, the case "[$wd, "."]" as $srcpath is specialcased -
680 instead of failing, "rename" is called on the absolute path of $wd.
681
682 aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
683 Basically a version of "aio_rename" with an additional $flags
684 argument. Calling this with "$flags=0" is the same as calling
685 "aio_rename".
686
687 Non-zero flags are currently only supported on GNU/Linux systems
688 that support renameat2. Other systems fail with "ENOSYS" in this
689 case.
690
691 The following constants are available (missing ones are, as usual
692 0), see renameat2(2) for details:
693
694 "IO::AIO::RENAME_NOREPLACE", "IO::AIO::RENAME_EXCHANGE" and
695 "IO::AIO::RENAME_WHITEOUT".
696
697 aio_mkdir $pathname, $mode, $callback->($status)
698 Asynchronously mkdir (create) a directory and call the callback with
699 the result code. $mode will be modified by the umask at the time the
700 request is executed, so do not change your umask.
701
702 aio_rmdir $pathname, $callback->($status)
703 Asynchronously rmdir (delete) a directory and call the callback with
704 the result code.
705
706 On systems that support the AIO::WD working directory abstraction
707 natively, the case "[$wd, "."]" is specialcased - instead of
708 failing, "rmdir" is called on the absolute path of $wd.
709
710 aio_readdir $pathname, $callback->($entries)
711 Unlike the POSIX call of the same name, "aio_readdir" reads an
712 entire directory (i.e. opendir + readdir + closedir). The entries
713 will not be sorted, and will NOT include the "." and ".." entries.
714
715 The callback is passed a single argument which is either "undef" or
716 an array-ref with the filenames.
717
718 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
719 Quite similar to "aio_readdir", but the $flags argument allows one
720 to tune behaviour and output format. In case of an error, $entries
721 will be "undef".
722
723 The flags are a combination of the following constants, ORed
724 together (the flags will also be passed to the callback, possibly
725 modified):
726
727 IO::AIO::READDIR_DENTS
728 Normally the callback gets an arrayref consisting of names only
729 (as with "aio_readdir"). If this flag is set, then the callback
730 gets an arrayref with "[$name, $type, $inode]" arrayrefs, each
731 describing a single directory entry in more detail:
732
733 $name is the name of the entry.
734
735 $type is one of the "IO::AIO::DT_xxx" constants:
736
737 "IO::AIO::DT_UNKNOWN", "IO::AIO::DT_FIFO", "IO::AIO::DT_CHR",
738 "IO::AIO::DT_DIR", "IO::AIO::DT_BLK", "IO::AIO::DT_REG",
739 "IO::AIO::DT_LNK", "IO::AIO::DT_SOCK", "IO::AIO::DT_WHT".
740
741 "IO::AIO::DT_UNKNOWN" means just that: readdir does not know. If
742 you need to know, you have to run stat yourself. Also, for
743 speed/memory reasons, the $type scalars are read-only: you must
744 not modify them.
745
746 $inode is the inode number (which might not be exact on systems
747 with 64 bit inode numbers and 32 bit perls). This field has
748 unspecified content on systems that do not deliver the inode
749 information.
750
751 IO::AIO::READDIR_DIRS_FIRST
752 When this flag is set, then the names will be returned in an
753 order where likely directories come first, in optimal stat
754 order. This is useful when you need to quickly find directories,
755 or you want to find all directories while avoiding to stat()
756 each entry.
757
758 If the system returns type information in readdir, then this is
759 used to find directories directly. Otherwise, likely directories
760 are names beginning with ".", or otherwise names with no dots,
761 of which names with short names are tried first.
762
763 IO::AIO::READDIR_STAT_ORDER
764 When this flag is set, then the names will be returned in an
765 order suitable for stat()'ing each one. That is, when you plan
766 to stat() most or all files in the given directory, then the
767 returned order will likely be faster.
768
769 If both this flag and "IO::AIO::READDIR_DIRS_FIRST" are
770 specified, then the likely dirs come first, resulting in a less
771 optimal stat order for stat'ing all entries, but likely a more
772 optimal order for finding subdirectories.
773
774 IO::AIO::READDIR_FOUND_UNKNOWN
775 This flag should not be set when calling "aio_readdirx".
776 Instead, it is being set by "aio_readdirx", when any of the
777 $type's found were "IO::AIO::DT_UNKNOWN". The absence of this
778 flag therefore indicates that all $type's are known, which can
779 be used to speed up some algorithms.
780
781 aio_slurp $pathname, $offset, $length, $data, $callback->($status)
782 Opens, reads and closes the given file. The data is put into $data,
783 which is resized as required.
784
785 If $offset is negative, then it is counted from the end of the file.
786
787 If $length is zero, then the remaining length of the file is used.
788 Also, in this case, the same limitations to modifying $data apply as
789 when IO::AIO::mmap is used, i.e. it must only be modified in-place
790 with "substr". If the size of the file is known, specifying a
791 non-zero $length results in a performance advantage.
792
793 This request is similar to the older "aio_load" request, but since
794 it is a single request, it might be more efficient to use.
795
796 Example: load /etc/passwd into $passwd.
797
798 my $passwd;
799 aio_slurp "/etc/passwd", 0, 0, $passwd, sub {
800 $_[0] >= 0
801 or die "/etc/passwd: $!\n";
802
803 printf "/etc/passwd is %d bytes long, and contains:\n", length $passwd;
804 print $passwd;
805 };
806 IO::AIO::flush;
807
808 aio_load $pathname, $data, $callback->($status)
809 This is a composite request that tries to fully load the given file
810 into memory. Status is the same as with aio_read.
811
812 Using "aio_slurp" might be more efficient, as it is a single
813 request.
814
815 aio_copy $srcpath, $dstpath, $callback->($status)
816 Try to copy the *file* (directories not supported as either source
817 or destination) from $srcpath to $dstpath and call the callback with
818 a status of 0 (ok) or -1 (error, see $!).
819
820 Existing destination files will be truncated.
821
822 This is a composite request that creates the destination file with
823 mode 0200 and copies the contents of the source file into it using
824 "aio_sendfile", followed by restoring atime, mtime, access mode and
825 uid/gid, in that order.
826
827 If an error occurs, the partial destination file will be unlinked,
828 if possible, except when setting atime, mtime, access mode and
829 uid/gid, where errors are being ignored.
830
831 aio_move $srcpath, $dstpath, $callback->($status)
832 Try to move the *file* (directories not supported as either source
833 or destination) from $srcpath to $dstpath and call the callback with
834 a status of 0 (ok) or -1 (error, see $!).
835
836 This is a composite request that tries to rename(2) the file first;
837 if rename fails with "EXDEV", it copies the file with "aio_copy"
838 and, if that is successful, unlinks the $srcpath.
839
840 aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
841 Scans a directory (similar to "aio_readdir") but additionally tries
842 to efficiently separate the entries of directory $path into two sets
843 of names, directories you can recurse into (directories), and ones
844 you cannot recurse into (everything else, including symlinks to
845 directories).
846
847 "aio_scandir" is a composite request that generates many sub
848 requests. $maxreq specifies the maximum number of outstanding aio
849 requests that this function generates. If it is "<= 0", then a
850 suitable default will be chosen (currently 4).
851
852 On error, the callback is called without arguments, otherwise it
853 receives two array-refs with path-relative entry names.
854
855 Example:
856
857 aio_scandir $dir, 0, sub {
858 my ($dirs, $nondirs) = @_;
859 print "real directories: @$dirs\n";
860 print "everything else: @$nondirs\n";
861 };
862
863 Implementation notes.
864
865 The "aio_readdir" cannot be avoided, but "stat()"'ing every entry
866 can.
867
868 If readdir returns file type information, then this is used directly
869 to find directories.
870
871 Otherwise, after reading the directory, the modification time, size
872 etc. of the directory before and after the readdir is checked, and
873 if they match (and isn't the current time), the link count will be
874 used to decide how many entries are directories (if >= 2).
875 Otherwise, no knowledge of the number of subdirectories will be
876 assumed.
877
878 Then entries will be sorted into likely directories a non-initial
879 dot currently) and likely non-directories (see "aio_readdirx"). Then
880 every entry plus an appended "/." will be "stat"'ed, likely
881 directories first, in order of their inode numbers. If that
882 succeeds, it assumes that the entry is a directory or a symlink to
883 directory (which will be checked separately). This is often faster
884 than stat'ing the entry itself because filesystems might detect the
885 type of the entry without reading the inode data (e.g. ext2fs
886 filetype feature), even on systems that cannot return the filetype
887 information on readdir.
888
889 If the known number of directories (link count - 2) has been
890 reached, the rest of the entries is assumed to be non-directories.
891
892 This only works with certainty on POSIX (= UNIX) filesystems, which
893 fortunately are the vast majority of filesystems around.
894
895 It will also likely work on non-POSIX filesystems with reduced
896 efficiency as those tend to return 0 or 1 as link counts, which
897 disables the directory counting heuristic.
898
899 aio_rmtree $pathname, $callback->($status)
900 Delete a directory tree starting (and including) $path, return the
901 status of the final "rmdir" only. This is a composite request that
902 uses "aio_scandir" to recurse into and rmdir directories, and unlink
903 everything else.
904
905 aio_fcntl $fh, $cmd, $arg, $callback->($status)
906 aio_ioctl $fh, $request, $buf, $callback->($status)
907 These work just like the "fcntl" and "ioctl" built-in functions,
908 except they execute asynchronously and pass the return value to the
909 callback.
910
911 Both calls can be used for a lot of things, some of which make more
912 sense to run asynchronously in their own thread, while some others
913 make less sense. For example, calls that block waiting for external
914 events, such as locking, will also lock down an I/O thread while it
915 is waiting, which can deadlock the whole I/O system. At the same
916 time, there might be no alternative to using a thread to wait.
917
918 So in general, you should only use these calls for things that do
919 (filesystem) I/O, not for things that wait for other events
920 (network, other processes), although if you are careful and know
921 what you are doing, you still can.
922
923 The following constants are available and can be used for normal
924 "ioctl" and "fcntl" as well (missing ones are, as usual 0):
925
926 "F_DUPFD_CLOEXEC",
927
928 "F_OFD_GETLK", "F_OFD_SETLK", "F_OFD_GETLKW",
929
930 "FIFREEZE", "FITHAW", "FITRIM", "FICLONE", "FICLONERANGE",
931 "FIDEDUPERANGE".
932
933 "F_ADD_SEALS", "F_GET_SEALS", "F_SEAL_SEAL", "F_SEAL_SHRINK",
934 "F_SEAL_GROW" and "F_SEAL_WRITE".
935
936 "FS_IOC_GETFLAGS", "FS_IOC_SETFLAGS", "FS_IOC_GETVERSION",
937 "FS_IOC_SETVERSION", "FS_IOC_FIEMAP".
938
939 "FS_IOC_FSGETXATTR", "FS_IOC_FSSETXATTR",
940 "FS_IOC_SET_ENCRYPTION_POLICY", "FS_IOC_GET_ENCRYPTION_PWSALT",
941 "FS_IOC_GET_ENCRYPTION_POLICY", "FS_KEY_DESCRIPTOR_SIZE".
942
943 "FS_SECRM_FL", "FS_UNRM_FL", "FS_COMPR_FL", "FS_SYNC_FL",
944 "FS_IMMUTABLE_FL", "FS_APPEND_FL", "FS_NODUMP_FL", "FS_NOATIME_FL",
945 "FS_DIRTY_FL", "FS_COMPRBLK_FL", "FS_NOCOMP_FL", "FS_ENCRYPT_FL",
946 "FS_BTREE_FL", "FS_INDEX_FL", "FS_JOURNAL_DATA_FL", "FS_NOTAIL_FL",
947 "FS_DIRSYNC_FL", "FS_TOPDIR_FL", "FS_FL_USER_MODIFIABLE".
948
949 "FS_XFLAG_REALTIME", "FS_XFLAG_PREALLOC", "FS_XFLAG_IMMUTABLE",
950 "FS_XFLAG_APPEND", "FS_XFLAG_SYNC", "FS_XFLAG_NOATIME",
951 "FS_XFLAG_NODUMP", "FS_XFLAG_RTINHERIT", "FS_XFLAG_PROJINHERIT",
952 "FS_XFLAG_NOSYMLINKS", "FS_XFLAG_EXTSIZE", "FS_XFLAG_EXTSZINHERIT",
953 "FS_XFLAG_NODEFRAG", "FS_XFLAG_FILESTREAM", "FS_XFLAG_DAX",
954 "FS_XFLAG_HASATTR",
955
956 aio_sync $callback->($status)
957 Asynchronously call sync and call the callback when finished.
958
181 aio_fsync $fh, $callback 959 aio_fsync $fh, $callback->($status)
182 Asynchronously call fsync on the given filehandle and call the 960 Asynchronously call fsync on the given filehandle and call the
183 callback with the fsync result code. 961 callback with the fsync result code.
184 962
185 aio_fdatasync $fh, $callback 963 aio_fdatasync $fh, $callback->($status)
186 Asynchronously call fdatasync on the given filehandle and call the 964 Asynchronously call fdatasync on the given filehandle and call the
187 callback with the fdatasync result code. 965 callback with the fdatasync result code.
188 966
189BUGS 967 If this call isn't available because your OS lacks it or it couldn't
190 - could be optimized to use more semaphores instead of filehandles. 968 be detected, it will be emulated by calling "fsync" instead.
969
970 aio_syncfs $fh, $callback->($status)
971 Asynchronously call the syncfs syscall to sync the filesystem
972 associated to the given filehandle and call the callback with the
973 syncfs result code. If syncfs is not available, calls sync(), but
974 returns -1 and sets errno to "ENOSYS" nevertheless.
975
976 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
977 Sync the data portion of the file specified by $offset and $length
978 to disk (but NOT the metadata), by calling the Linux-specific
979 sync_file_range call. If sync_file_range is not available or it
980 returns ENOSYS, then fdatasync or fsync is being substituted.
981
982 $flags can be a combination of
983 "IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE",
984 "IO::AIO::SYNC_FILE_RANGE_WRITE" and
985 "IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER": refer to the sync_file_range
986 manpage for details.
987
988 aio_pathsync $pathname, $callback->($status)
989 This request tries to open, fsync and close the given path. This is
990 a composite request intended to sync directories after directory
991 operations (E.g. rename). This might not work on all operating
992 systems or have any specific effect, but usually it makes sure that
993 directory changes get written to disc. It works for anything that
994 can be opened for read-only, not just directories.
995
996 Future versions of this function might fall back to other methods
997 when "fsync" on the directory fails (such as calling "sync").
998
999 Passes 0 when everything went ok, and -1 on error.
1000
1001 aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC,
1002 $callback->($status)
1003 This is a rather advanced IO::AIO call, which only works on
1004 mmap(2)ed scalars (see the "IO::AIO::mmap" function, although it
1005 also works on data scalars managed by the Sys::Mmap or Mmap modules,
1006 note that the scalar must only be modified in-place while an aio
1007 operation is pending on it).
1008
1009 It calls the "msync" function of your OS, if available, with the
1010 memory area starting at $offset in the string and ending $length
1011 bytes later. If $length is negative, counts from the end, and if
1012 $length is "undef", then it goes till the end of the string. The
1013 flags can be either "IO::AIO::MS_ASYNC" or "IO::AIO::MS_SYNC", plus
1014 an optional "IO::AIO::MS_INVALIDATE".
1015
1016 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0,
1017 $callback->($status)
1018 This is a rather advanced IO::AIO call, which works best on
1019 mmap(2)ed scalars.
1020
1021 It touches (reads or writes) all memory pages in the specified range
1022 inside the scalar. All caveats and parameters are the same as for
1023 "aio_msync", above, except for flags, which must be either 0 (which
1024 reads all pages and ensures they are instantiated) or
1025 "IO::AIO::MT_MODIFY", which modifies the memory pages (by reading
1026 and writing an octet from it, which dirties the page).
1027
1028 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
1029 This is a rather advanced IO::AIO call, which works best on
1030 mmap(2)ed scalars.
1031
1032 It reads in all the pages of the underlying storage into memory (if
1033 any) and locks them, so they are not getting swapped/paged out or
1034 removed.
1035
1036 If $length is undefined, then the scalar will be locked till the
1037 end.
1038
1039 On systems that do not implement "mlock", this function returns -1
1040 and sets errno to "ENOSYS".
1041
1042 Note that the corresponding "munlock" is synchronous and is
1043 documented under "MISCELLANEOUS FUNCTIONS".
1044
1045 Example: open a file, mmap and mlock it - both will be undone when
1046 $data gets destroyed.
1047
1048 open my $fh, "<", $path or die "$path: $!";
1049 my $data;
1050 IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
1051 aio_mlock $data; # mlock in background
1052
1053 aio_mlockall $flags, $callback->($status)
1054 Calls the "mlockall" function with the given $flags (a combination
1055 of "IO::AIO::MCL_CURRENT", "IO::AIO::MCL_FUTURE" and
1056 "IO::AIO::MCL_ONFAULT").
1057
1058 On systems that do not implement "mlockall", this function returns
1059 -1 and sets errno to "ENOSYS". Similarly, flag combinations not
1060 supported by the system result in a return value of -1 with errno
1061 being set to "EINVAL".
1062
1063 Note that the corresponding "munlockall" is synchronous and is
1064 documented under "MISCELLANEOUS FUNCTIONS".
1065
1066 Example: asynchronously lock all current and future pages into
1067 memory.
1068
1069 aio_mlockall IO::AIO::MCL_FUTURE;
1070
1071 aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
1072 Queries the extents of the given file (by calling the Linux "FIEMAP"
1073 ioctl, see <http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for
1074 details). If the ioctl is not available on your OS, then this
1075 request will fail with "ENOSYS".
1076
1077 $start is the starting offset to query extents for, $length is the
1078 size of the range to query - if it is "undef", then the whole file
1079 will be queried.
1080
1081 $flags is a combination of flags ("IO::AIO::FIEMAP_FLAG_SYNC" or
1082 "IO::AIO::FIEMAP_FLAG_XATTR" - "IO::AIO::FIEMAP_FLAGS_COMPAT" is
1083 also exported), and is normally 0 or "IO::AIO::FIEMAP_FLAG_SYNC" to
1084 query the data portion.
1085
1086 $count is the maximum number of extent records to return. If it is
1087 "undef", then IO::AIO queries all extents of the range. As a very
1088 special case, if it is 0, then the callback receives the number of
1089 extents instead of the extents themselves (which is unreliable, see
1090 below).
1091
1092 If an error occurs, the callback receives no arguments. The special
1093 "errno" value "IO::AIO::EBADR" is available to test for flag errors.
1094
1095 Otherwise, the callback receives an array reference with extent
1096 structures. Each extent structure is an array reference itself, with
1097 the following members:
1098
1099 [$logical, $physical, $length, $flags]
1100
1101 Flags is any combination of the following flag values (typically
1102 either 0 or "IO::AIO::FIEMAP_EXTENT_LAST" (1)):
1103
1104 "IO::AIO::FIEMAP_EXTENT_LAST", "IO::AIO::FIEMAP_EXTENT_UNKNOWN",
1105 "IO::AIO::FIEMAP_EXTENT_DELALLOC", "IO::AIO::FIEMAP_EXTENT_ENCODED",
1106 "IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED",
1107 "IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED",
1108 "IO::AIO::FIEMAP_EXTENT_DATA_INLINE",
1109 "IO::AIO::FIEMAP_EXTENT_DATA_TAIL",
1110 "IO::AIO::FIEMAP_EXTENT_UNWRITTEN", "IO::AIO::FIEMAP_EXTENT_MERGED"
1111 or "IO::AIO::FIEMAP_EXTENT_SHARED".
1112
1113 At the time of this writing (Linux 3.2), this request is unreliable
1114 unless $count is "undef", as the kernel has all sorts of bugs
1115 preventing it to return all extents of a range for files with a
1116 large number of extents. The code (only) works around all these
1117 issues if $count is "undef".
1118
1119 aio_group $callback->(...)
1120 This is a very special aio request: Instead of doing something, it
1121 is a container for other aio requests, which is useful if you want
1122 to bundle many requests into a single, composite, request with a
1123 definite callback and the ability to cancel the whole request with
1124 its subrequests.
1125
1126 Returns an object of class IO::AIO::GRP. See its documentation below
1127 for more info.
1128
1129 Example:
1130
1131 my $grp = aio_group sub {
1132 print "all stats done\n";
1133 };
1134
1135 add $grp
1136 (aio_stat ...),
1137 (aio_stat ...),
1138 ...;
1139
1140 aio_nop $callback->()
1141 This is a special request - it does nothing in itself and is only
1142 used for side effects, such as when you want to add a dummy request
1143 to a group so that finishing the requests in the group depends on
1144 executing the given code.
1145
1146 While this request does nothing, it still goes through the execution
1147 phase and still requires a worker thread. Thus, the callback will
1148 not be executed immediately but only after other requests in the
1149 queue have entered their execution phase. This can be used to
1150 measure request latency.
1151
1152 IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
1153 Mainly used for debugging and benchmarking, this aio request puts
1154 one of the request workers to sleep for the given time.
1155
1156 While it is theoretically handy to have simple I/O scheduling
1157 requests like sleep and file handle readable/writable, the overhead
1158 this creates is immense (it blocks a thread for a long time) so do
1159 not use this function except to put your application under
1160 artificial I/O pressure.
1161
1162 IO::AIO::WD - multiple working directories
1163 Your process only has one current working directory, which is used by
1164 all threads. This makes it hard to use relative paths (some other
1165 component could call "chdir" at any time, and it is hard to control when
1166 the path will be used by IO::AIO).
1167
1168 One solution for this is to always use absolute paths. This usually
1169 works, but can be quite slow (the kernel has to walk the whole path on
1170 every access), and can also be a hassle to implement.
1171
1172 Newer POSIX systems have a number of functions (openat, fdopendir,
1173 futimensat and so on) that make it possible to specify working
1174 directories per operation.
1175
1176 For portability, and because the clowns who "designed", or shall I
1177 write, perpetrated this new interface were obviously half-drunk, this
1178 abstraction cannot be perfect, though.
1179
1180 IO::AIO allows you to convert directory paths into a so-called
1181 IO::AIO::WD object. This object stores the canonicalised, absolute
1182 version of the path, and on systems that allow it, also a directory file
1183 descriptor.
1184
1185 Everywhere where a pathname is accepted by IO::AIO (e.g. in "aio_stat"
1186 or "aio_unlink"), one can specify an array reference with an IO::AIO::WD
1187 object and a pathname instead (or the IO::AIO::WD object alone, which
1188 gets interpreted as "[$wd, "."]"). If the pathname is absolute, the
1189 IO::AIO::WD object is ignored, otherwise the pathname is resolved
1190 relative to that IO::AIO::WD object.
1191
1192 For example, to get a wd object for /etc and then stat passwd inside,
1193 you would write:
1194
1195 aio_wd "/etc", sub {
1196 my $etcdir = shift;
1197
1198 # although $etcdir can be undef on error, there is generally no reason
1199 # to check for errors here, as aio_stat will fail with ENOENT
1200 # when $etcdir is undef.
1201
1202 aio_stat [$etcdir, "passwd"], sub {
1203 # yay
1204 };
1205 };
1206
1207 The fact that "aio_wd" is a request and not a normal function shows that
1208 creating an IO::AIO::WD object is itself a potentially blocking
1209 operation, which is why it is done asynchronously.
1210
1211 To stat the directory obtained with "aio_wd" above, one could write
1212 either of the following three request calls:
1213
1214 aio_lstat "/etc" , sub { ... # pathname as normal string
1215 aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
1216 aio_lstat $wd , sub { ... # shorthand for the previous
1217
1218 As with normal pathnames, IO::AIO keeps a copy of the working directory
1219 object and the pathname string, so you could write the following without
1220 causing any issues due to $path getting reused:
1221
1222 my $path = [$wd, undef];
1223
1224 for my $name (qw(abc def ghi)) {
1225 $path->[1] = $name;
1226 aio_stat $path, sub {
1227 # ...
1228 };
1229 }
1230
1231 There are some caveats: when directories get renamed (or deleted), the
1232 pathname string doesn't change, so will point to the new directory (or
1233 nowhere at all), while the directory fd, if available on the system,
1234 will still point to the original directory. Most functions accepting a
1235 pathname will use the directory fd on newer systems, and the string on
1236 older systems. Some functions (such as "aio_realpath") will always rely
1237 on the string form of the pathname.
1238
1239 So this functionality is mainly useful to get some protection against
1240 "chdir", to easily get an absolute path out of a relative path for
1241 future reference, and to speed up doing many operations in the same
1242 directory (e.g. when stat'ing all files in a directory).
1243
1244 The following functions implement this working directory abstraction:
1245
1246 aio_wd $pathname, $callback->($wd)
1247 Asynchonously canonicalise the given pathname and convert it to an
1248 IO::AIO::WD object representing it. If possible and supported on the
1249 system, also open a directory fd to speed up pathname resolution
1250 relative to this working directory.
1251
1252 If something goes wrong, then "undef" is passwd to the callback
1253 instead of a working directory object and $! is set appropriately.
1254 Since passing "undef" as working directory component of a pathname
1255 fails the request with "ENOENT", there is often no need for error
1256 checking in the "aio_wd" callback, as future requests using the
1257 value will fail in the expected way.
1258
1259 IO::AIO::CWD
1260 This is a compile time constant (object) that represents the process
1261 current working directory.
1262
1263 Specifying this object as working directory object for a pathname is
1264 as if the pathname would be specified directly, without a directory
1265 object. For example, these calls are functionally identical:
1266
1267 aio_stat "somefile", sub { ... };
1268 aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
1269
1270 To recover the path associated with an IO::AIO::WD object, you can use
1271 "aio_realpath":
1272
1273 aio_realpath $wd, sub {
1274 warn "path is $_[0]\n";
1275 };
1276
1277 Currently, "aio_statvfs" always, and "aio_rename" and "aio_rmdir"
1278 sometimes, fall back to using an absolue path.
1279
1280 IO::AIO::REQ CLASS
1281 All non-aggregate "aio_*" functions return an object of this class when
1282 called in non-void context.
1283
1284 cancel $req
1285 Cancels the request, if possible. Has the effect of skipping
1286 execution when entering the execute state and skipping calling the
1287 callback when entering the the result state, but will leave the
1288 request otherwise untouched (with the exception of readdir). That
1289 means that requests that currently execute will not be stopped and
1290 resources held by the request will not be freed prematurely.
1291
1292 cb $req $callback->(...)
1293 Replace (or simply set) the callback registered to the request.
1294
1295 IO::AIO::GRP CLASS
1296 This class is a subclass of IO::AIO::REQ, so all its methods apply to
1297 objects of this class, too.
1298
1299 A IO::AIO::GRP object is a special request that can contain multiple
1300 other aio requests.
1301
1302 You create one by calling the "aio_group" constructing function with a
1303 callback that will be called when all contained requests have entered
1304 the "done" state:
1305
1306 my $grp = aio_group sub {
1307 print "all requests are done\n";
1308 };
1309
1310 You add requests by calling the "add" method with one or more
1311 "IO::AIO::REQ" objects:
1312
1313 $grp->add (aio_unlink "...");
1314
1315 add $grp aio_stat "...", sub {
1316 $_[0] or return $grp->result ("error");
1317
1318 # add another request dynamically, if first succeeded
1319 add $grp aio_open "...", sub {
1320 $grp->result ("ok");
1321 };
1322 };
1323
1324 This makes it very easy to create composite requests (see the source of
1325 "aio_move" for an application) that work and feel like simple requests.
1326
1327 * The IO::AIO::GRP objects will be cleaned up during calls to
1328 "IO::AIO::poll_cb", just like any other request.
1329
1330 * They can be canceled like any other request. Canceling will cancel
1331 not only the request itself, but also all requests it contains.
1332
1333 * They can also can also be added to other IO::AIO::GRP objects.
1334
1335 * You must not add requests to a group from within the group callback
1336 (or any later time).
1337
1338 Their lifetime, simplified, looks like this: when they are empty, they
1339 will finish very quickly. If they contain only requests that are in the
1340 "done" state, they will also finish. Otherwise they will continue to
1341 exist.
1342
1343 That means after creating a group you have some time to add requests
1344 (precisely before the callback has been invoked, which is only done
1345 within the "poll_cb"). And in the callbacks of those requests, you can
1346 add further requests to the group. And only when all those requests have
1347 finished will the the group itself finish.
1348
1349 add $grp ...
1350 $grp->add (...)
1351 Add one or more requests to the group. Any type of IO::AIO::REQ can
1352 be added, including other groups, as long as you do not create
1353 circular dependencies.
1354
1355 Returns all its arguments.
1356
1357 $grp->cancel_subs
1358 Cancel all subrequests and clears any feeder, but not the group
1359 request itself. Useful when you queued a lot of events but got a
1360 result early.
1361
1362 The group request will finish normally (you cannot add requests to
1363 the group).
1364
1365 $grp->result (...)
1366 Set the result value(s) that will be passed to the group callback
1367 when all subrequests have finished and set the groups errno to the
1368 current value of errno (just like calling "errno" without an error
1369 number). By default, no argument will be passed and errno is zero.
1370
1371 $grp->errno ([$errno])
1372 Sets the group errno value to $errno, or the current value of errno
1373 when the argument is missing.
1374
1375 Every aio request has an associated errno value that is restored
1376 when the callback is invoked. This method lets you change this value
1377 from its default (0).
1378
1379 Calling "result" will also set errno, so make sure you either set $!
1380 before the call to "result", or call c<errno> after it.
1381
1382 feed $grp $callback->($grp)
1383 Sets a feeder/generator on this group: every group can have an
1384 attached generator that generates requests if idle. The idea behind
1385 this is that, although you could just queue as many requests as you
1386 want in a group, this might starve other requests for a potentially
1387 long time. For example, "aio_scandir" might generate hundreds of
1388 thousands of "aio_stat" requests, delaying any later requests for a
1389 long time.
1390
1391 To avoid this, and allow incremental generation of requests, you can
1392 instead a group and set a feeder on it that generates those
1393 requests. The feed callback will be called whenever there are few
1394 enough (see "limit", below) requests active in the group itself and
1395 is expected to queue more requests.
1396
1397 The feed callback can queue as many requests as it likes (i.e. "add"
1398 does not impose any limits).
1399
1400 If the feed does not queue more requests when called, it will be
1401 automatically removed from the group.
1402
1403 If the feed limit is 0 when this method is called, it will be set to
1404 2 automatically.
1405
1406 Example:
1407
1408 # stat all files in @files, but only ever use four aio requests concurrently:
1409
1410 my $grp = aio_group sub { print "finished\n" };
1411 limit $grp 4;
1412 feed $grp sub {
1413 my $file = pop @files
1414 or return;
1415
1416 add $grp aio_stat $file, sub { ... };
1417 };
1418
1419 limit $grp $num
1420 Sets the feeder limit for the group: The feeder will be called
1421 whenever the group contains less than this many requests.
1422
1423 Setting the limit to 0 will pause the feeding process.
1424
1425 The default value for the limit is 0, but note that setting a feeder
1426 automatically bumps it up to 2.
1427
1428 SUPPORT FUNCTIONS
1429 EVENT PROCESSING AND EVENT LOOP INTEGRATION
1430 $fileno = IO::AIO::poll_fileno
1431 Return the *request result pipe file descriptor*. This filehandle
1432 must be polled for reading by some mechanism outside this module
1433 (e.g. EV, Glib, select and so on, see below or the SYNOPSIS). If the
1434 pipe becomes readable you have to call "poll_cb" to check the
1435 results.
1436
1437 See "poll_cb" for an example.
1438
1439 IO::AIO::poll_cb
1440 Process some requests that have reached the result phase (i.e. they
1441 have been executed but the results are not yet reported). You have
1442 to call this "regularly" to finish outstanding requests.
1443
1444 Returns 0 if all events could be processed (or there were no events
1445 to process), or -1 if it returned earlier for whatever reason.
1446 Returns immediately when no events are outstanding. The amount of
1447 events processed depends on the settings of "IO::AIO::max_poll_req",
1448 "IO::AIO::max_poll_time" and "IO::AIO::max_outstanding".
1449
1450 If not all requests were processed for whatever reason, the poll
1451 file descriptor will still be ready when "poll_cb" returns, so
1452 normally you don't have to do anything special to have it called
1453 later.
1454
1455 Apart from calling "IO::AIO::poll_cb" when the event filehandle
1456 becomes ready, it can be beneficial to call this function from loops
1457 which submit a lot of requests, to make sure the results get
1458 processed when they become available and not just when the loop is
1459 finished and the event loop takes over again. This function returns
1460 very fast when there are no outstanding requests.
1461
1462 Example: Install an Event watcher that automatically calls
1463 IO::AIO::poll_cb with high priority (more examples can be found in
1464 the SYNOPSIS section, at the top of this document):
1465
1466 Event->io (fd => IO::AIO::poll_fileno,
1467 poll => 'r', async => 1,
1468 cb => \&IO::AIO::poll_cb);
1469
1470 IO::AIO::poll_wait
1471 Wait until either at least one request is in the result phase or no
1472 requests are outstanding anymore.
1473
1474 This is useful if you want to synchronously wait for some requests
1475 to become ready, without actually handling them.
1476
1477 See "nreqs" for an example.
1478
1479 IO::AIO::poll
1480 Waits until some requests have been handled.
1481
1482 Returns the number of requests processed, but is otherwise strictly
1483 equivalent to:
1484
1485 IO::AIO::poll_wait, IO::AIO::poll_cb
1486
1487 IO::AIO::flush
1488 Wait till all outstanding AIO requests have been handled.
1489
1490 Strictly equivalent to:
1491
1492 IO::AIO::poll_wait, IO::AIO::poll_cb
1493 while IO::AIO::nreqs;
1494
1495 This function can be useful at program aborts, to make sure
1496 outstanding I/O has been done ("IO::AIO" uses an "END" block which
1497 already calls this function on normal exits), or when you are merely
1498 using "IO::AIO" for its more advanced functions, rather than for
1499 async I/O, e.g.:
1500
1501 my ($dirs, $nondirs);
1502 IO::AIO::aio_scandir "/tmp", 0, sub { ($dirs, $nondirs) = @_ };
1503 IO::AIO::flush;
1504 # $dirs, $nondirs are now set
1505
1506 IO::AIO::max_poll_reqs $nreqs
1507 IO::AIO::max_poll_time $seconds
1508 These set the maximum number of requests (default 0, meaning
1509 infinity) that are being processed by "IO::AIO::poll_cb" in one
1510 call, respectively the maximum amount of time (default 0, meaning
1511 infinity) spent in "IO::AIO::poll_cb" to process requests (more
1512 correctly the mininum amount of time "poll_cb" is allowed to use).
1513
1514 Setting "max_poll_time" to a non-zero value creates an overhead of
1515 one syscall per request processed, which is not normally a problem
1516 unless your callbacks are really really fast or your OS is really
1517 really slow (I am not mentioning Solaris here). Using
1518 "max_poll_reqs" incurs no overhead.
1519
1520 Setting these is useful if you want to ensure some level of
1521 interactiveness when perl is not fast enough to process all requests
1522 in time.
1523
1524 For interactive programs, values such as 0.01 to 0.1 should be fine.
1525
1526 Example: Install an Event watcher that automatically calls
1527 IO::AIO::poll_cb with low priority, to ensure that other parts of
1528 the program get the CPU sometimes even under high AIO load.
1529
1530 # try not to spend much more than 0.1s in poll_cb
1531 IO::AIO::max_poll_time 0.1;
1532
1533 # use a low priority so other tasks have priority
1534 Event->io (fd => IO::AIO::poll_fileno,
1535 poll => 'r', nice => 1,
1536 cb => &IO::AIO::poll_cb);
1537
1538 CONTROLLING THE NUMBER OF THREADS
1539 IO::AIO::min_parallel $nthreads
1540 Set the minimum number of AIO threads to $nthreads. The current
1541 default is 8, which means eight asynchronous operations can execute
1542 concurrently at any one time (the number of outstanding requests,
1543 however, is unlimited).
1544
1545 IO::AIO starts threads only on demand, when an AIO request is queued
1546 and no free thread exists. Please note that queueing up a hundred
1547 requests can create demand for a hundred threads, even if it turns
1548 out that everything is in the cache and could have been processed
1549 faster by a single thread.
1550
1551 It is recommended to keep the number of threads relatively low, as
1552 some Linux kernel versions will scale negatively with the number of
1553 threads (higher parallelity => MUCH higher latency). With current
1554 Linux 2.6 versions, 4-32 threads should be fine.
1555
1556 Under most circumstances you don't need to call this function, as
1557 the module selects a default that is suitable for low to moderate
1558 load.
1559
1560 IO::AIO::max_parallel $nthreads
1561 Sets the maximum number of AIO threads to $nthreads. If more than
1562 the specified number of threads are currently running, this function
1563 kills them. This function blocks until the limit is reached.
1564
1565 While $nthreads are zero, aio requests get queued but not executed
1566 until the number of threads has been increased again.
1567
1568 This module automatically runs "max_parallel 0" at program end, to
1569 ensure that all threads are killed and that there are no outstanding
1570 requests.
1571
1572 Under normal circumstances you don't need to call this function.
1573
1574 IO::AIO::max_idle $nthreads
1575 Limit the number of threads (default: 4) that are allowed to idle
1576 (i.e., threads that did not get a request to process within the idle
1577 timeout (default: 10 seconds). That means if a thread becomes idle
1578 while $nthreads other threads are also idle, it will free its
1579 resources and exit.
1580
1581 This is useful when you allow a large number of threads (e.g. 100 or
1582 1000) to allow for extremely high load situations, but want to free
1583 resources under normal circumstances (1000 threads can easily
1584 consume 30MB of RAM).
1585
1586 The default is probably ok in most situations, especially if thread
1587 creation is fast. If thread creation is very slow on your system you
1588 might want to use larger values.
1589
1590 IO::AIO::idle_timeout $seconds
1591 Sets the minimum idle timeout (default 10) after which worker
1592 threads are allowed to exit. SEe "IO::AIO::max_idle".
1593
1594 IO::AIO::max_outstanding $maxreqs
1595 Sets the maximum number of outstanding requests to $nreqs. If you do
1596 queue up more than this number of requests, the next call to
1597 "IO::AIO::poll_cb" (and other functions calling "poll_cb", such as
1598 "IO::AIO::flush" or "IO::AIO::poll") will block until the limit is
1599 no longer exceeded.
1600
1601 In other words, this setting does not enforce a queue limit, but can
1602 be used to make poll functions block if the limit is exceeded.
1603
1604 This is a bad function to use in interactive programs because it
1605 blocks, and a bad way to reduce concurrency because it is inexact.
1606 If you need to issue many requests without being able to call a poll
1607 function on demand, it is better to use an "aio_group" together with
1608 a feed callback.
1609
1610 Its main use is in scripts without an event loop - when you want to
1611 stat a lot of files, you can write something like this:
1612
1613 IO::AIO::max_outstanding 32;
1614
1615 for my $path (...) {
1616 aio_stat $path , ...;
1617 IO::AIO::poll_cb;
1618 }
1619
1620 IO::AIO::flush;
1621
1622 The call to "poll_cb" inside the loop will normally return
1623 instantly, allowing the loop to progress, but as soon as more than
1624 32 requests are in-flight, it will block until some requests have
1625 been handled. This keeps the loop from pushing a large number of
1626 "aio_stat" requests onto the queue (which, with many paths to stat,
1627 can use up a lot of memory).
1628
1629 The default value for "max_outstanding" is very large, so there is
1630 no practical limit on the number of outstanding requests.
1631
1632 STATISTICAL INFORMATION
1633 IO::AIO::nreqs
1634 Returns the number of requests currently in the ready, execute or
1635 pending states (i.e. for which their callback has not been invoked
1636 yet).
1637
1638 Example: wait till there are no outstanding requests anymore:
1639
1640 IO::AIO::poll_wait, IO::AIO::poll_cb
1641 while IO::AIO::nreqs;
1642
1643 IO::AIO::nready
1644 Returns the number of requests currently in the ready state (not yet
1645 executed).
1646
1647 IO::AIO::npending
1648 Returns the number of requests currently in the pending state
1649 (executed, but not yet processed by poll_cb).
1650
1651 SUBSECOND STAT TIME ACCESS
1652 Both "aio_stat"/"aio_lstat" and perl's "stat"/"lstat" functions can
1653 generally find access/modification and change times with subsecond time
1654 accuracy of the system supports it, but perl's built-in functions only
1655 return the integer part.
1656
1657 The following functions return the timestamps of the most recent stat
1658 with subsecond precision on most systems and work both after
1659 "aio_stat"/"aio_lstat" and perl's "stat"/"lstat" calls. Their return
1660 value is only meaningful after a successful "stat"/"lstat" call, or
1661 during/after a successful "aio_stat"/"aio_lstat" callback.
1662
1663 This is similar to the Time::HiRes "stat" functions, but can return full
1664 resolution without rounding and work with standard perl "stat",
1665 alleviating the need to call the special "Time::HiRes" functions, which
1666 do not act like their perl counterparts.
1667
1668 On operating systems or file systems where subsecond time resolution is
1669 not supported or could not be detected, a fractional part of 0 is
1670 returned, so it is always safe to call these functions.
1671
1672 $seconds = IO::AIO::st_atime, IO::AIO::st_mtime, IO::AIO::st_ctime,
1673 IO::AIO::st_btime
1674 Return the access, modication, change or birth time, respectively,
1675 including fractional part. Due to the limited precision of floating
1676 point, the accuracy on most platforms is only a bit better than
1677 milliseconds for times around now - see the *nsec* function family,
1678 below, for full accuracy.
1679
1680 File birth time is only available when the OS and perl support it
1681 (on FreeBSD and NetBSD at the time of this writing, although support
1682 is adaptive, so if your OS/perl gains support, IO::AIO can take
1683 advantage of it). On systems where it isn't available, 0 is
1684 currently returned, but this might change to "undef" in a future
1685 version.
1686
1687 ($atime, $mtime, $ctime, $btime, ...) = IO::AIO::st_xtime
1688 Returns access, modification, change and birth time all in one go,
1689 and maybe more times in the future version.
1690
1691 $nanoseconds = IO::AIO::st_atimensec, IO::AIO::st_mtimensec,
1692 IO::AIO::st_ctimensec, IO::AIO::st_btimensec
1693 Return the fractional access, modifcation, change or birth time, in
1694 nanoseconds, as an integer in the range 0 to 999999999.
1695
1696 Note that no accessors are provided for access, modification and
1697 change times - you need to get those from "stat _" if required ("int
1698 IO::AIO::st_atime" and so on will *not* generally give you the
1699 correct value).
1700
1701 $seconds = IO::AIO::st_btimesec
1702 The (integral) seconds part of the file birth time, if available.
1703
1704 ($atime, $mtime, $ctime, $btime, ...) = IO::AIO::st_xtimensec
1705 Like the functions above, but returns all four times in one go (and
1706 maybe more in future versions).
1707
1708 $counter = IO::AIO::st_gen
1709 Returns the generation counter (in practice this is just a random
1710 number) of the file. This is only available on platforms which have
1711 this member in their "struct stat" (most BSDs at the time of this
1712 writing) and generally only to the root usert. If unsupported, 0 is
1713 returned, but this might change to "undef" in a future version.
1714
1715 Example: print the high resolution modification time of /etc, using
1716 "stat", and "IO::AIO::aio_stat".
1717
1718 if (stat "/etc") {
1719 printf "stat(/etc) mtime: %f\n", IO::AIO::st_mtime;
1720 }
1721
1722 IO::AIO::aio_stat "/etc", sub {
1723 $_[0]
1724 and return;
1725
1726 printf "aio_stat(/etc) mtime: %d.%09d\n", (stat _)[9], IO::AIO::st_mtimensec;
1727 };
1728
1729 IO::AIO::flush;
1730
1731 Output of the awbove on my system, showing reduced and full accuracy:
1732
1733 stat(/etc) mtime: 1534043702.020808
1734 aio_stat(/etc) mtime: 1534043702.020807792
1735
1736 MISCELLANEOUS FUNCTIONS
1737 IO::AIO implements some functions that are useful when you want to use
1738 some "Advanced I/O" function not available to in Perl, without going the
1739 "Asynchronous I/O" route. Many of these have an asynchronous "aio_*"
1740 counterpart.
1741
1742 $retval = IO::AIO::fexecve $fh, $argv, $envp
1743 A more-or-less direct equivalent to the POSIX "fexecve" functions,
1744 which allows you to specify the program to be executed via a file
1745 descriptor (or handle). Returns -1 and sets errno to "ENOSYS" if not
1746 available.
1747
1748 $numfd = IO::AIO::get_fdlimit
1749 Tries to find the current file descriptor limit and returns it, or
1750 "undef" and sets $! in case of an error. The limit is one larger
1751 than the highest valid file descriptor number.
1752
1753 IO::AIO::min_fdlimit [$numfd]
1754 Try to increase the current file descriptor limit(s) to at least
1755 $numfd by changing the soft or hard file descriptor resource limit.
1756 If $numfd is missing, it will try to set a very high limit, although
1757 this is not recommended when you know the actual minimum that you
1758 require.
1759
1760 If the limit cannot be raised enough, the function makes a
1761 best-effort attempt to increase the limit as much as possible, using
1762 various tricks, while still failing. You can query the resulting
1763 limit using "IO::AIO::get_fdlimit".
1764
1765 If an error occurs, returns "undef" and sets $!, otherwise returns
1766 true.
1767
1768 IO::AIO::sendfile $ofh, $ifh, $offset, $count
1769 Calls the "eio_sendfile_sync" function, which is like
1770 "aio_sendfile", but is blocking (this makes most sense if you know
1771 the input data is likely cached already and the output filehandle is
1772 set to non-blocking operations).
1773
1774 Returns the number of bytes copied, or -1 on error.
1775
1776 IO::AIO::fadvise $fh, $offset, $len, $advice
1777 Simply calls the "posix_fadvise" function (see its manpage for
1778 details). The following advice constants are available:
1779 "IO::AIO::FADV_NORMAL", "IO::AIO::FADV_SEQUENTIAL",
1780 "IO::AIO::FADV_RANDOM", "IO::AIO::FADV_NOREUSE",
1781 "IO::AIO::FADV_WILLNEED", "IO::AIO::FADV_DONTNEED".
1782
1783 On systems that do not implement "posix_fadvise", this function
1784 returns ENOSYS, otherwise the return value of "posix_fadvise".
1785
1786 IO::AIO::madvise $scalar, $offset, $len, $advice
1787 Simply calls the "posix_madvise" function (see its manpage for
1788 details). The following advice constants are available:
1789 "IO::AIO::MADV_NORMAL", "IO::AIO::MADV_SEQUENTIAL",
1790 "IO::AIO::MADV_RANDOM", "IO::AIO::MADV_WILLNEED",
1791 "IO::AIO::MADV_DONTNEED".
1792
1793 If $offset is negative, counts from the end. If $length is negative,
1794 the remaining length of the $scalar is used. If possible, $length
1795 will be reduced to fit into the $scalar.
1796
1797 On systems that do not implement "posix_madvise", this function
1798 returns ENOSYS, otherwise the return value of "posix_madvise".
1799
1800 IO::AIO::mprotect $scalar, $offset, $len, $protect
1801 Simply calls the "mprotect" function on the preferably AIO::mmap'ed
1802 $scalar (see its manpage for details). The following protect
1803 constants are available: "IO::AIO::PROT_NONE", "IO::AIO::PROT_READ",
1804 "IO::AIO::PROT_WRITE", "IO::AIO::PROT_EXEC".
1805
1806 If $offset is negative, counts from the end. If $length is negative,
1807 the remaining length of the $scalar is used. If possible, $length
1808 will be reduced to fit into the $scalar.
1809
1810 On systems that do not implement "mprotect", this function returns
1811 ENOSYS, otherwise the return value of "mprotect".
1812
1813 IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
1814 Memory-maps a file (or anonymous memory range) and attaches it to
1815 the given $scalar, which will act like a string scalar. Returns true
1816 on success, and false otherwise.
1817
1818 The scalar must exist, but its contents do not matter - this means
1819 you cannot use a nonexistant array or hash element. When in doubt,
1820 "undef" the scalar first.
1821
1822 The only operations allowed on the mmapped scalar are
1823 "substr"/"vec", which don't change the string length, and most
1824 read-only operations such as copying it or searching it with regexes
1825 and so on.
1826
1827 Anything else is unsafe and will, at best, result in memory leaks.
1828
1829 The memory map associated with the $scalar is automatically removed
1830 when the $scalar is undef'd or destroyed, or when the
1831 "IO::AIO::mmap" or "IO::AIO::munmap" functions are called on it.
1832
1833 This calls the "mmap"(2) function internally. See your system's
1834 manual page for details on the $length, $prot and $flags parameters.
1835
1836 The $length must be larger than zero and smaller than the actual
1837 filesize.
1838
1839 $prot is a combination of "IO::AIO::PROT_NONE",
1840 "IO::AIO::PROT_EXEC", "IO::AIO::PROT_READ" and/or
1841 "IO::AIO::PROT_WRITE",
1842
1843 $flags can be a combination of "IO::AIO::MAP_SHARED" or
1844 "IO::AIO::MAP_PRIVATE", or a number of system-specific flags (when
1845 not available, the are 0): "IO::AIO::MAP_ANONYMOUS" (which is set to
1846 "MAP_ANON" if your system only provides this constant),
1847 "IO::AIO::MAP_LOCKED", "IO::AIO::MAP_NORESERVE",
1848 "IO::AIO::MAP_POPULATE", "IO::AIO::MAP_NONBLOCK",
1849 "IO::AIO::MAP_FIXED", "IO::AIO::MAP_GROWSDOWN",
1850 "IO::AIO::MAP_32BIT", "IO::AIO::MAP_HUGETLB", "IO::AIO::MAP_STACK",
1851 "IO::AIO::MAP_FIXED_NOREPLACE", "IO::AIO::MAP_SHARED_VALIDATE",
1852 "IO::AIO::MAP_SYNC" or "IO::AIO::MAP_UNINITIALIZED".
1853
1854 If $fh is "undef", then a file descriptor of -1 is passed.
1855
1856 $offset is the offset from the start of the file - it generally must
1857 be a multiple of "IO::AIO::PAGESIZE" and defaults to 0.
1858
1859 Example:
1860
1861 use Digest::MD5;
1862 use IO::AIO;
1863
1864 open my $fh, "<verybigfile"
1865 or die "$!";
1866
1867 IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
1868 or die "verybigfile: $!";
1869
1870 my $fast_md5 = md5 $data;
1871
1872 IO::AIO::munmap $scalar
1873 Removes a previous mmap and undefines the $scalar.
1874
1875 IO::AIO::mremap $scalar, $new_length, $flags = MREMAP_MAYMOVE[,
1876 $new_address = 0]
1877 Calls the Linux-specific mremap(2) system call. The $scalar must
1878 have been mapped by "IO::AIO::mmap", and $flags must currently
1879 either be 0 or "IO::AIO::MREMAP_MAYMOVE".
1880
1881 Returns true if successful, and false otherwise. If the underlying
1882 mmapped region has changed address, then the true value has the
1883 numerical value 1, otherwise it has the numerical value 0:
1884
1885 my $success = IO::AIO::mremap $mmapped, 8192, IO::AIO::MREMAP_MAYMOVE
1886 or die "mremap: $!";
1887
1888 if ($success*1) {
1889 warn "scalar has chanegd address in memory\n";
1890 }
1891
1892 "IO::AIO::MREMAP_FIXED" and the $new_address argument are currently
1893 implemented, but not supported and might go away in a future
1894 version.
1895
1896 On systems where this call is not supported or is not emulated, this
1897 call returns falls and sets $! to "ENOSYS".
1898
1899 IO::AIO::mlockall $flags
1900 Calls the "eio_mlockall_sync" function, which is like
1901 "aio_mlockall", but is blocking.
1902
1903 IO::AIO::munlock $scalar, $offset = 0, $length = undef
1904 Calls the "munlock" function, undoing the effects of a previous
1905 "aio_mlock" call (see its description for details).
1906
1907 IO::AIO::munlockall
1908 Calls the "munlockall" function.
1909
1910 On systems that do not implement "munlockall", this function returns
1911 ENOSYS, otherwise the return value of "munlockall".
1912
1913 $fh = IO::AIO::accept4 $r_fh, $sockaddr, $sockaddr_maxlen, $flags
1914 Uses the GNU/Linux accept4(2) syscall, if available, to accept a
1915 socket and return the new file handle on success, or sets $! and
1916 returns "undef" on error.
1917
1918 The remote name of the new socket will be stored in $sockaddr, which
1919 will be extended to allow for at least $sockaddr_maxlen octets. If
1920 the socket name does not fit into $sockaddr_maxlen octets, this is
1921 signaled by returning a longer string in $sockaddr, which might or
1922 might not be truncated.
1923
1924 To accept name-less sockets, use "undef" for $sockaddr and 0 for
1925 $sockaddr_maxlen.
1926
1927 The main reasons to use this syscall rather than portable accept(2)
1928 are that you can specify "SOCK_NONBLOCK" and/or "SOCK_CLOEXEC" flags
1929 and you can accept name-less sockets by specifying 0 for
1930 $sockaddr_maxlen, which is sadly not possible with perl's interface
1931 to "accept".
1932
1933 IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
1934 Calls the GNU/Linux splice(2) syscall, if available. If $r_off or
1935 $w_off are "undef", then "NULL" is passed for these, otherwise they
1936 should be the file offset.
1937
1938 $r_fh and $w_fh should not refer to the same file, as splice might
1939 silently corrupt the data in this case.
1940
1941 The following symbol flag values are available:
1942 "IO::AIO::SPLICE_F_MOVE", "IO::AIO::SPLICE_F_NONBLOCK",
1943 "IO::AIO::SPLICE_F_MORE" and "IO::AIO::SPLICE_F_GIFT".
1944
1945 See the splice(2) manpage for details.
1946
1947 IO::AIO::tee $r_fh, $w_fh, $length, $flags
1948 Calls the GNU/Linux tee(2) syscall, see its manpage and the
1949 description for "IO::AIO::splice" above for details.
1950
1951 $actual_size = IO::AIO::pipesize $r_fh[, $new_size]
1952 Attempts to query or change the pipe buffer size. Obviously works
1953 only on pipes, and currently works only on GNU/Linux systems, and
1954 fails with -1/"ENOSYS" everywhere else. If anybody knows how to
1955 influence pipe buffer size on other systems, drop me a note.
1956
1957 ($rfh, $wfh) = IO::AIO::pipe2 [$flags]
1958 This is a direct interface to the Linux pipe2(2) system call. If
1959 $flags is missing or 0, then this should be the same as a call to
1960 perl's built-in "pipe" function and create a new pipe, and works on
1961 systems that lack the pipe2 syscall. On win32, this case invokes
1962 "_pipe (..., 4096, O_BINARY)".
1963
1964 If $flags is non-zero, it tries to invoke the pipe2 system call with
1965 the given flags (Linux 2.6.27, glibc 2.9).
1966
1967 On success, the read and write file handles are returned.
1968
1969 On error, nothing will be returned. If the pipe2 syscall is missing
1970 and $flags is non-zero, fails with "ENOSYS".
1971
1972 Please refer to pipe2(2) for more info on the $flags, but at the
1973 time of this writing, "IO::AIO::O_CLOEXEC", "IO::AIO::O_NONBLOCK"
1974 and "IO::AIO::O_DIRECT" (Linux 3.4, for packet-based pipes) were
1975 supported.
1976
1977 Example: create a pipe race-free w.r.t. threads and fork:
1978
1979 my ($rfh, $wfh) = IO::AIO::pipe2 IO::AIO::O_CLOEXEC
1980 or die "pipe2: $!\n";
1981
1982 $fh = IO::AIO::memfd_create $pathname[, $flags]
1983 This is a direct interface to the Linux memfd_create(2) system call.
1984 The (unhelpful) default for $flags is 0, but your default should be
1985 "IO::AIO::MFD_CLOEXEC".
1986
1987 On success, the new memfd filehandle is returned, otherwise returns
1988 "undef". If the memfd_create syscall is missing, fails with
1989 "ENOSYS".
1990
1991 Please refer to memfd_create(2) for more info on this call.
1992
1993 The following $flags values are available: "IO::AIO::MFD_CLOEXEC",
1994 "IO::AIO::MFD_ALLOW_SEALING", "IO::AIO::MFD_HUGETLB",
1995 "IO::AIO::MFD_HUGETLB_2MB" and "IO::AIO::MFD_HUGETLB_1GB".
1996
1997 Example: create a new memfd.
1998
1999 my $fh = IO::AIO::memfd_create "somenameforprocfd", IO::AIO::MFD_CLOEXEC
2000 or die "memfd_create: $!\n";
2001
2002 $fh = IO::AIO::pidfd_open $pid[, $flags]
2003 This is an interface to the Linux pidfd_open(2) system call. The
2004 default for $flags is 0.
2005
2006 On success, a new pidfd filehandle is returned (that is already set
2007 to close-on-exec), otherwise returns "undef". If the syscall is
2008 missing, fails with "ENOSYS".
2009
2010 Example: open pid 6341 as pidfd.
2011
2012 my $fh = IO::AIO::pidfd_open 6341
2013 or die "pidfd_open: $!\n";
2014
2015 $status = IO::AIO::pidfd_send_signal $pidfh, $signal[, $siginfo[,
2016 $flags]]
2017 This is an interface to the Linux pidfd_send_signal system call. The
2018 default for $siginfo is "undef" and the default for $flags is 0.
2019
2020 Returns the system call status. If the syscall is missing, fails
2021 with "ENOSYS".
2022
2023 When specified, $siginfo must be a reference to a hash with one or
2024 more of the following members:
2025
2026 code - the "si_code" member
2027 pid - the "si_pid" member
2028 uid - the "si_uid" member
2029 value_int - the "si_value.sival_int" member
2030 value_ptr - the "si_value.sival_ptr" member, specified as an integer
2031
2032 Example: send a SIGKILL to the specified process.
2033
2034 my $status = IO::AIO::pidfd_send_signal $pidfh, 9, undef
2035 and die "pidfd_send_signal: $!\n";
2036
2037 Example: send a SIGKILL to the specified process with extra data.
2038
2039 my $status = IO::AIO::pidfd_send_signal $pidfh, 9, { code => -1, value_int => 7 }
2040 and die "pidfd_send_signal: $!\n";
2041
2042 $fh = IO::AIO::pidfd_getfd $pidfh, $targetfd[, $flags]
2043 This is an interface to the Linux pidfd_getfd system call. The
2044 default for $flags is 0.
2045
2046 On success, returns a dup'ed copy of the target file descriptor
2047 (specified as an integer) returned (that is already set to
2048 close-on-exec), otherwise returns "undef". If the syscall is
2049 missing, fails with "ENOSYS".
2050
2051 Example: get a copy of standard error of another process and print
2052 soemthing to it.
2053
2054 my $errfh = IO::AIO::pidfd_getfd $pidfh, 2
2055 or die "pidfd_getfd: $!\n";
2056 print $errfh "stderr\n";
2057
2058 $fh = IO::AIO::eventfd [$initval, [$flags]]
2059 This is a direct interface to the Linux eventfd(2) system call. The
2060 (unhelpful) defaults for $initval and $flags are 0 for both.
2061
2062 On success, the new eventfd filehandle is returned, otherwise
2063 returns "undef". If the eventfd syscall is missing, fails with
2064 "ENOSYS".
2065
2066 Please refer to eventfd(2) for more info on this call.
2067
2068 The following symbol flag values are available:
2069 "IO::AIO::EFD_CLOEXEC", "IO::AIO::EFD_NONBLOCK" and
2070 "IO::AIO::EFD_SEMAPHORE" (Linux 2.6.30).
2071
2072 Example: create a new eventfd filehandle:
2073
2074 $fh = IO::AIO::eventfd 0, IO::AIO::EFD_CLOEXEC
2075 or die "eventfd: $!\n";
2076
2077 $fh = IO::AIO::timerfd_create $clockid[, $flags]
2078 This is a direct interface to the Linux timerfd_create(2) system
2079 call. The (unhelpful) default for $flags is 0, but your default
2080 should be "IO::AIO::TFD_CLOEXEC".
2081
2082 On success, the new timerfd filehandle is returned, otherwise
2083 returns "undef". If the timerfd_create syscall is missing, fails
2084 with "ENOSYS".
2085
2086 Please refer to timerfd_create(2) for more info on this call.
2087
2088 The following $clockid values are available:
2089 "IO::AIO::CLOCK_REALTIME", "IO::AIO::CLOCK_MONOTONIC"
2090 "IO::AIO::CLOCK_CLOCK_BOOTTIME" (Linux 3.15)
2091 "IO::AIO::CLOCK_CLOCK_REALTIME_ALARM" (Linux 3.11) and
2092 "IO::AIO::CLOCK_CLOCK_BOOTTIME_ALARM" (Linux 3.11).
2093
2094 The following $flags values are available (Linux 2.6.27):
2095 "IO::AIO::TFD_NONBLOCK" and "IO::AIO::TFD_CLOEXEC".
2096
2097 Example: create a new timerfd and set it to one-second repeated
2098 alarms, then wait for two alarms:
2099
2100 my $fh = IO::AIO::timerfd_create IO::AIO::CLOCK_BOOTTIME, IO::AIO::TFD_CLOEXEC
2101 or die "timerfd_create: $!\n";
2102
2103 defined IO::AIO::timerfd_settime $fh, 0, 1, 1
2104 or die "timerfd_settime: $!\n";
2105
2106 for (1..2) {
2107 8 == sysread $fh, my $buf, 8
2108 or die "timerfd read failure\n";
2109
2110 printf "number of expirations (likely 1): %d\n",
2111 unpack "Q", $buf;
2112 }
2113
2114 ($cur_interval, $cur_value) = IO::AIO::timerfd_settime $fh, $flags,
2115 $new_interval, $nbw_value
2116 This is a direct interface to the Linux timerfd_settime(2) system
2117 call. Please refer to its manpage for more info on this call.
2118
2119 The new itimerspec is specified using two (possibly fractional)
2120 second values, $new_interval and $new_value).
2121
2122 On success, the current interval and value are returned (as per
2123 "timerfd_gettime"). On failure, the empty list is returned.
2124
2125 The following $flags values are available:
2126 "IO::AIO::TFD_TIMER_ABSTIME" and "IO::AIO::TFD_TIMER_CANCEL_ON_SET".
2127
2128 See "IO::AIO::timerfd_create" for a full example.
2129
2130 ($cur_interval, $cur_value) = IO::AIO::timerfd_gettime $fh
2131 This is a direct interface to the Linux timerfd_gettime(2) system
2132 call. Please refer to its manpage for more info on this call.
2133
2134 On success, returns the current values of interval and value for the
2135 given timerfd (as potentially fractional second values). On failure,
2136 the empty list is returned.
2137
2138EVENT LOOP INTEGRATION
2139 It is recommended to use AnyEvent::AIO to integrate IO::AIO
2140 automatically into many event loops:
2141
2142 # AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
2143 use AnyEvent::AIO;
2144
2145 You can also integrate IO::AIO manually into many event loops, here are
2146 some examples of how to do this:
2147
2148 # EV integration
2149 my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
2150
2151 # Event integration
2152 Event->io (fd => IO::AIO::poll_fileno,
2153 poll => 'r',
2154 cb => \&IO::AIO::poll_cb);
2155
2156 # Glib/Gtk2 integration
2157 add_watch Glib::IO IO::AIO::poll_fileno,
2158 in => sub { IO::AIO::poll_cb; 1 };
2159
2160 # Tk integration
2161 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
2162 readable => \&IO::AIO::poll_cb);
2163
2164 # Danga::Socket integration
2165 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
2166 \&IO::AIO::poll_cb);
2167
2168 FORK BEHAVIOUR
2169 Usage of pthreads in a program changes the semantics of fork
2170 considerably. Specifically, only async-safe functions can be called
2171 after fork. Perl doesn't know about this, so in general, you cannot call
2172 fork with defined behaviour in perl if pthreads are involved. IO::AIO
2173 uses pthreads, so this applies, but many other extensions and (for
2174 inexplicable reasons) perl itself often is linked against pthreads, so
2175 this limitation applies to quite a lot of perls.
2176
2177 This module no longer tries to fight your OS, or POSIX. That means
2178 IO::AIO only works in the process that loaded it. Forking is fully
2179 supported, but using IO::AIO in the child is not.
2180
2181 You might get around by not *using* IO::AIO before (or after) forking.
2182 You could also try to call the IO::AIO::reinit function in the child:
2183
2184 IO::AIO::reinit
2185 Abandons all current requests and I/O threads and simply
2186 reinitialises all data structures. This is not an operation
2187 supported by any standards, but happens to work on GNU/Linux and
2188 some newer BSD systems.
2189
2190 The only reasonable use for this function is to call it after
2191 forking, if "IO::AIO" was used in the parent. Calling it while
2192 IO::AIO is active in the process will result in undefined behaviour.
2193 Calling it at any time will also result in any undefined (by POSIX)
2194 behaviour.
2195
2196 LINUX-SPECIFIC CALLS
2197 When a call is documented as "linux-specific" then this means it
2198 originated on GNU/Linux. "IO::AIO" will usually try to autodetect the
2199 availability and compatibility of such calls regardless of the platform
2200 it is compiled on, so platforms such as FreeBSD which often implement
2201 these calls will work. When in doubt, call them and see if they fail wth
2202 "ENOSYS".
2203
2204 MEMORY USAGE
2205 Per-request usage:
2206
2207 Each aio request uses - depending on your architecture - around 100-200
2208 bytes of memory. In addition, stat requests need a stat buffer (possibly
2209 a few hundred bytes), readdir requires a result buffer and so on. Perl
2210 scalars and other data passed into aio requests will also be locked and
2211 will consume memory till the request has entered the done state.
2212
2213 This is not awfully much, so queuing lots of requests is not usually a
2214 problem.
2215
2216 Per-thread usage:
2217
2218 In the execution phase, some aio requests require more memory for
2219 temporary buffers, and each thread requires a stack and other data
2220 structures (usually around 16k-128k, depending on the OS).
2221
2222KNOWN BUGS
2223 Known bugs will be fixed in the next release :)
2224
2225KNOWN ISSUES
2226 Calls that try to "import" foreign memory areas (such as "IO::AIO::mmap"
2227 or "IO::AIO::aio_slurp") do not work with generic lvalues, such as
2228 non-created hash slots or other scalars I didn't think of. It's best to
2229 avoid such and either use scalar variables or making sure that the
2230 scalar exists (e.g. by storing "undef") and isn't "funny" (e.g. tied).
2231
2232 I am not sure anything can be done about this, so this is considered a
2233 known issue, rather than a bug.
191 2234
192SEE ALSO 2235SEE ALSO
193 Coro, Linux::AIO. 2236 AnyEvent::AIO for easy integration into event loops, Coro::AIO for a
2237 more natural syntax and IO::FDPass for file descriptor passing.
194 2238
195AUTHOR 2239AUTHOR
196 Marc Lehmann <schmorp@schmorp.de> 2240 Marc Lehmann <schmorp@schmorp.de>
197 http://home.schmorp.de/ 2241 http://home.schmorp.de/
198 2242

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