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Revision 1.70 by root, Sat Apr 1 02:14:05 2023 UTC

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", O_RDONLY, 0, sub { 7 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
8 my ($fh) = @_; 8 my $fh = shift
9 or die "/etc/passwd: $!";
9 ... 10 ...
10 }; 11 };
11 12
12 aio_unlink "/tmp/file", sub { }; 13 aio_unlink "/tmp/file", sub { };
13 14
14 aio_read $fh, 30000, 1024, $buffer, 0, sub { 15 aio_read $fh, 30000, 1024, $buffer, 0, sub {
15 $_[0] > 0 or die "read error: $!"; 16 $_[0] > 0 or die "read error: $!";
16 }; 17 };
17 18
18 # Event 19 # version 2+ has request and group objects
19 Event->io (fd => IO::AIO::poll_fileno, 20 use IO::AIO 2;
20 poll => 'r',
21 cb => \&IO::AIO::poll_cb);
22 21
23 # Glib/Gtk2 22 aioreq_pri 4; # give next request a very high priority
24 add_watch Glib::IO IO::AIO::poll_fileno, 23 my $req = aio_unlink "/tmp/file", sub { };
25 in => sub { IO::AIO::poll_cb; 1 }; 24 $req->cancel; # cancel request if still in queue
26 25
27 # Tk 26 my $grp = aio_group sub { print "all stats done\n" };
28 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "", 27 add $grp aio_stat "..." for ...;
29 readable => \&IO::AIO::poll_cb);
30
31 # Danga::Socket
32 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
33 \&IO::AIO::poll_cb);
34 28
35DESCRIPTION 29DESCRIPTION
36 This module implements asynchronous I/O using whatever means your 30 This module implements asynchronous I/O using whatever means your
37 operating system supports. 31 operating system supports. It is implemented as an interface to "libeio"
32 (<http://software.schmorp.de/pkg/libeio.html>).
38 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
39 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
40 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
41 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
42 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
43 native aio functions available on many operating systems. However, they 54 functions available on many operating systems. However, they are often
44 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
45 currently, for example), and they would only support aio_read and 56 files currently, for example), and they would only support aio_read and
46 aio_write, so the remaining functionality would have to be implemented 57 aio_write, so the remaining functionality would have to be implemented
47 using threads anyway. 58 using threads anyway.
48 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
49 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,
50 is currently not reentrant, so use appropriate locking yourself, always 65 it is currently not reentrant in any way, so use appropriate locking
51 call "poll_cb" from within the same thread, or never call "poll_cb" (or 66 yourself, always call "poll_cb" from within the same thread, or never
52 other "aio_" functions) recursively. 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).
53 151
54FUNCTIONS 152FUNCTIONS
55 AIO FUNCTIONS 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]
269
270 $retval = IO::AIO::mount $special, $path, $fstype, $flags = 0, $data = undef
271 $retval = IO::AIO::umount $path, $flags = 0
272
273 API NOTES
56 All the "aio_*" calls are more or less thin wrappers around the syscall 274 All the "aio_*" calls are more or less thin wrappers around the syscall
57 with the same name (sans "aio_"). The arguments are similar or 275 with the same name (sans "aio_"). The arguments are similar or
58 identical, and they all accept an additional (and optional) $callback 276 identical, and they all accept an additional (and optional) $callback
59 argument which must be a code reference. This code reference will get 277 argument which must be a code reference. This code reference will be
60 called with the syscall return code (e.g. most syscalls return -1 on 278 called after the syscall has been executed in an asynchronous fashion.
61 error, unlike perl, which usually delivers "false") as it's sole 279 The results of the request will be passed as arguments to the callback
62 argument when the given syscall has been executed asynchronously. 280 (and, if an error occured, in $!) - for most requests the syscall return
281 code (e.g. most syscalls return -1 on error, unlike perl, which usually
282 delivers "false").
283
284 Some requests (such as "aio_readdir") pass the actual results and
285 communicate failures by passing "undef".
63 286
64 All functions expecting a filehandle keep a copy of the filehandle 287 All functions expecting a filehandle keep a copy of the filehandle
65 internally until the request has finished. 288 internally until the request has finished.
66 289
290 All functions return request objects of type IO::AIO::REQ that allow
291 further manipulation of those requests while they are in-flight.
292
67 The pathnames you pass to these routines *must* be absolute and encoded 293 The pathnames you pass to these routines *should* be absolute. The
68 in byte form. The reason for the former is that at the time the request 294 reason for this is that at the time the request is being executed, the
69 is being executed, the current working directory could have changed. 295 current working directory could have changed. Alternatively, you can
70 Alternatively, you can make sure that you never change the current 296 make sure that you never change the current working directory anywhere
71 working directory. 297 in the program and then use relative paths. You can also take advantage
298 of IO::AIOs working directory abstraction, that lets you specify paths
299 relative to some previously-opened "working directory object" - see the
300 description of the "IO::AIO::WD" class later in this document.
72 301
73 To encode pathnames to byte form, either make sure you either: a) always 302 To encode pathnames as octets, either make sure you either: a) always
74 pass in filenames you got from outside (command line, readdir etc.), b) 303 pass in filenames you got from outside (command line, readdir etc.)
75 are ASCII or ISO 8859-1, c) use the Encode module and encode your 304 without tinkering, b) are in your native filesystem encoding, c) use the
76 pathnames to the locale (or other) encoding in effect in the user 305 Encode module and encode your pathnames to the locale (or other)
77 environment, d) use Glib::filename_from_unicode on unicode filenames or 306 encoding in effect in the user environment, d) use
78 e) use something else. 307 Glib::filename_from_unicode on unicode filenames or e) use something
308 else to ensure your scalar has the correct contents.
79 309
310 This works, btw. independent of the internal UTF-8 bit, which IO::AIO
311 handles correctly whether it is set or not.
312
313 AIO REQUEST FUNCTIONS
314 $prev_pri = aioreq_pri [$pri]
315 Returns the priority value that would be used for the next request
316 and, if $pri is given, sets the priority for the next aio request.
317
318 The default priority is 0, the minimum and maximum priorities are -4
319 and 4, respectively. Requests with higher priority will be serviced
320 first.
321
322 The priority will be reset to 0 after each call to one of the
323 "aio_*" functions.
324
325 Example: open a file with low priority, then read something from it
326 with higher priority so the read request is serviced before other
327 low priority open requests (potentially spamming the cache):
328
329 aioreq_pri -3;
330 aio_open ..., sub {
331 return unless $_[0];
332
333 aioreq_pri -2;
334 aio_read $_[0], ..., sub {
335 ...
336 };
337 };
338
339 aioreq_nice $pri_adjust
340 Similar to "aioreq_pri", but subtracts the given value from the
341 current priority, so the effect is cumulative.
342
80 aio_open $pathname, $flags, $mode, $callback 343 aio_open $pathname, $flags, $mode, $callback->($fh)
81 Asynchronously open or create a file and call the callback with a 344 Asynchronously open or create a file and call the callback with a
82 newly created filehandle for the file. 345 newly created filehandle for the file (or "undef" in case of an
83 346 error).
84 The pathname passed to "aio_open" must be absolute. See API NOTES,
85 above, for an explanation.
86 347
87 The $flags 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.
88 They are the same as used by "sysopen". 349 They are the same as used by "sysopen".
89 350
90 Likewise, $mode specifies the mode of the newly created file, if it 351 Likewise, $mode specifies the mode of the newly created file, if it
91 didn't exist and "O_CREAT" has been given, just like perl's 352 didn't exist and "O_CREAT" has been given, just like perl's
92 "sysopen", except that it is mandatory (i.e. use 0 if you don't 353 "sysopen", except that it is mandatory (i.e. use 0 if you don't
93 create new files, and 0666 or 0777 if you do). 354 create new files, and 0666 or 0777 if you do). Note that the $mode
355 will be modified by the umask in effect then the request is being
356 executed, so better never change the umask.
94 357
95 Example: 358 Example:
96 359
97 aio_open "/etc/passwd", O_RDONLY, 0, sub { 360 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
98 if ($_[0]) { 361 if ($_[0]) {
99 print "open successful, fh is $_[0]\n"; 362 print "open successful, fh is $_[0]\n";
100 ... 363 ...
101 } else { 364 } else {
102 die "open failed: $!\n"; 365 die "open failed: $!\n";
103 } 366 }
104 }; 367 };
105 368
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
106 aio_close $fh, $callback 379 aio_close $fh, $callback->($status)
107 Asynchronously close a file and call the callback with the result 380 Asynchronously close a file and call the callback with the result
108 code. *WARNING:* although accepted, you should not pass in a perl 381 code.
109 filehandle here, as perl will likely close the file descriptor
110 another time when the filehandle is destroyed. Normally, you can
111 safely call perls "close" or just let filehandles go out of scope.
112 382
113 This is supposed to be a bug in the API, so that might change. It's 383 Unfortunately, you can't do this to perl. Perl *insists* very
114 therefore best to avoid this function. 384 strongly on closing the file descriptor associated with the
385 filehandle itself.
115 386
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
116 aio_read $fh,$offset,$length, $data,$dataoffset,$callback 413 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
117 aio_write $fh,$offset,$length, $data,$dataoffset,$callback 414 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
118 Reads or writes "length" bytes from the specified "fh" and "offset" 415 Reads or writes $length bytes from or to the specified $fh and
119 into the scalar given by "data" and offset "dataoffset" and calls 416 $offset into the scalar given by $data and offset $dataoffset and
120 the callback without the actual number of bytes read (or -1 on 417 calls the callback with the actual number of bytes transferred (or
121 error, just like the syscall). 418 -1 on error, just like the syscall).
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.
122 432
123 The $data scalar *MUST NOT* be modified in any way while the request 433 The $data scalar *MUST NOT* be modified in any way while the request
124 is outstanding. Modifying it can result in segfaults or WW3 (if the 434 is outstanding. Modifying it can result in segfaults or World War
125 necessary/optional hardware is installed). 435 III (if the necessary/optional hardware is installed).
126 436
127 Example: Read 15 bytes at offset 7 into scalar $buffer, starting at 437 Example: Read 15 bytes at offset 7 into scalar $buffer, starting at
128 offset 0 within the scalar: 438 offset 0 within the scalar:
129 439
130 aio_read $fh, 7, 15, $buffer, 0, sub { 440 aio_read $fh, 7, 15, $buffer, 0, sub {
131 $_[0] > 0 or die "read error: $!"; 441 $_[0] > 0 or die "read error: $!";
132 print "read $_[0] bytes: <$buffer>\n"; 442 print "read $_[0] bytes: <$buffer>\n";
133 }; 443 };
134 444
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
135 aio_readahead $fh,$offset,$length, $callback 488 aio_readahead $fh,$offset,$length, $callback->($retval)
136 "aio_readahead" populates the page cache with data from a file so 489 "aio_readahead" populates the page cache with data from a file so
137 that 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
138 $offset argument specifies the starting point from which data is to 491 $offset argument specifies the starting point from which data is to
139 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
140 performed in whole pages, so that offset is effectively rounded down 493 performed in whole pages, so that offset is effectively rounded down
141 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
142 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
143 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
144 is left unchanged. 497 is left unchanged.
145 498
146 If that syscall doesn't exist (likely if your OS isn't Linux) it 499 If that syscall doesn't exist (likely if your kernel isn't Linux) it
147 will be emulated by simply reading the data, which would have a 500 will be emulated by simply reading the data, which would have a
148 similar effect. 501 similar effect.
149 502
150 aio_stat $fh_or_path, $callback 503 aio_stat $fh_or_path, $callback->($status)
151 aio_lstat $fh, $callback 504 aio_lstat $fh, $callback->($status)
152 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.
153 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
154 using "stat _" or "-s _" etc... 507 available using "stat _" or "-s _" and other tests (with the
155 508 exception of "-B" and "-T").
156 The pathname passed to "aio_stat" must be absolute. See API NOTES,
157 above, for an explanation.
158 509
159 Currently, the stats are always 64-bit-stats, i.e. instead of 510 Currently, the stats are always 64-bit-stats, i.e. instead of
160 returning an error when stat'ing a large file, the results will be 511 returning an error when stat'ing a large file, the results will be
161 silently truncated unless perl itself is compiled with large file 512 silently truncated unless perl itself is compiled with large file
162 support. 513 support.
163 514
515 To help interpret the mode and dev/rdev stat values, IO::AIO offers
516 the following constants and functions (if not implemented, the
517 constants will be 0 and the functions will either "croak" or fall
518 back on traditional behaviour).
519
520 "S_IFMT", "S_IFIFO", "S_IFCHR", "S_IFBLK", "S_IFLNK", "S_IFREG",
521 "S_IFDIR", "S_IFWHT", "S_IFSOCK", "IO::AIO::major $dev_t",
522 "IO::AIO::minor $dev_t", "IO::AIO::makedev $major, $minor".
523
524 To access higher resolution stat timestamps, see "SUBSECOND STAT
525 TIME ACCESS".
526
164 Example: Print the length of /etc/passwd: 527 Example: Print the length of /etc/passwd:
165 528
166 aio_stat "/etc/passwd", sub { 529 aio_stat "/etc/passwd", sub {
167 $_[0] and die "stat failed: $!"; 530 $_[0] and die "stat failed: $!";
168 print "size is ", -s _, "\n"; 531 print "size is ", -s _, "\n";
169 }; 532 };
170 533
534 aio_statvfs $fh_or_path, $callback->($statvfs)
535 Works like the POSIX "statvfs" or "fstatvfs" syscalls, depending on
536 whether a file handle or path was passed.
537
538 On success, the callback is passed a hash reference with the
539 following members: "bsize", "frsize", "blocks", "bfree", "bavail",
540 "files", "ffree", "favail", "fsid", "flag" and "namemax". On
541 failure, "undef" is passed.
542
543 The following POSIX IO::AIO::ST_* constants are defined: "ST_RDONLY"
544 and "ST_NOSUID".
545
546 The following non-POSIX IO::AIO::ST_* flag masks are defined to
547 their correct value when available, or to 0 on systems that do not
548 support them: "ST_NODEV", "ST_NOEXEC", "ST_SYNCHRONOUS",
549 "ST_MANDLOCK", "ST_WRITE", "ST_APPEND", "ST_IMMUTABLE",
550 "ST_NOATIME", "ST_NODIRATIME" and "ST_RELATIME".
551
552 Example: stat "/wd" and dump out the data if successful.
553
554 aio_statvfs "/wd", sub {
555 my $f = $_[0]
556 or die "statvfs: $!";
557
558 use Data::Dumper;
559 say Dumper $f;
560 };
561
562 # result:
563 {
564 bsize => 1024,
565 bfree => 4333064312,
566 blocks => 10253828096,
567 files => 2050765568,
568 flag => 4096,
569 favail => 2042092649,
570 bavail => 4333064312,
571 ffree => 2042092649,
572 namemax => 255,
573 frsize => 1024,
574 fsid => 1810
575 }
576
577 aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
578 Works like perl's "utime" function (including the special case of
579 $atime and $mtime being undef). Fractional times are supported if
580 the underlying syscalls support them.
581
582 When called with a pathname, uses utimensat(2) or utimes(2) if
583 available, otherwise utime(2). If called on a file descriptor, uses
584 futimens(2) or futimes(2) if available, otherwise returns ENOSYS, so
585 this is not portable.
586
587 Examples:
588
589 # set atime and mtime to current time (basically touch(1)):
590 aio_utime "path", undef, undef;
591 # set atime to current time and mtime to beginning of the epoch:
592 aio_utime "path", time, undef; # undef==0
593
594 aio_chown $fh_or_path, $uid, $gid, $callback->($status)
595 Works like perl's "chown" function, except that "undef" for either
596 $uid or $gid is being interpreted as "do not change" (but -1 can
597 also be used).
598
599 Examples:
600
601 # same as "chown root path" in the shell:
602 aio_chown "path", 0, -1;
603 # same as above:
604 aio_chown "path", 0, undef;
605
606 aio_truncate $fh_or_path, $offset, $callback->($status)
607 Works like truncate(2) or ftruncate(2).
608
609 aio_allocate $fh, $mode, $offset, $len, $callback->($status)
610 Allocates or frees disk space according to the $mode argument. See
611 the linux "fallocate" documentation for details.
612
613 $mode is usually 0 or "IO::AIO::FALLOC_FL_KEEP_SIZE" to allocate
614 space, or "IO::AIO::FALLOC_FL_PUNCH_HOLE |
615 IO::AIO::FALLOC_FL_KEEP_SIZE", to deallocate a file range.
616
617 IO::AIO also supports "FALLOC_FL_COLLAPSE_RANGE", to remove a range
618 (without leaving a hole), "FALLOC_FL_ZERO_RANGE", to zero a range,
619 "FALLOC_FL_INSERT_RANGE" to insert a range and
620 "FALLOC_FL_UNSHARE_RANGE" to unshare shared blocks (see your
621 fallocate(2) manpage).
622
623 The file system block size used by "fallocate" is presumably the
624 "f_bsize" returned by "statvfs", but different filesystems and
625 filetypes can dictate other limitations.
626
627 If "fallocate" isn't available or cannot be emulated (currently no
628 emulation will be attempted), passes -1 and sets $! to "ENOSYS".
629
630 aio_chmod $fh_or_path, $mode, $callback->($status)
631 Works like perl's "chmod" function.
632
171 aio_unlink $pathname, $callback 633 aio_unlink $pathname, $callback->($status)
172 Asynchronously unlink (delete) a file and call the callback with the 634 Asynchronously unlink (delete) a file and call the callback with the
173 result code. 635 result code.
174 636
637 aio_mknod $pathname, $mode, $dev, $callback->($status)
638 [EXPERIMENTAL]
639
640 Asynchronously create a device node (or fifo). See mknod(2).
641
642 The only (POSIX-) portable way of calling this function is:
643
644 aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
645
646 See "aio_stat" for info about some potentially helpful extra
647 constants and functions.
648
649 aio_link $srcpath, $dstpath, $callback->($status)
650 Asynchronously create a new link to the existing object at $srcpath
651 at the path $dstpath and call the callback with the result code.
652
653 aio_symlink $srcpath, $dstpath, $callback->($status)
654 Asynchronously create a new symbolic link to the existing object at
655 $srcpath at the path $dstpath and call the callback with the result
656 code.
657
658 aio_readlink $pathname, $callback->($link)
659 Asynchronously read the symlink specified by $path and pass it to
660 the callback. If an error occurs, nothing or undef gets passed to
661 the callback.
662
663 aio_realpath $pathname, $callback->($path)
664 Asynchronously make the path absolute and resolve any symlinks in
665 $path. The resulting path only consists of directories (same as
666 Cwd::realpath).
667
668 This request can be used to get the absolute path of the current
669 working directory by passing it a path of . (a single dot).
670
671 aio_rename $srcpath, $dstpath, $callback->($status)
672 Asynchronously rename the object at $srcpath to $dstpath, just as
673 rename(2) and call the callback with the result code.
674
675 On systems that support the AIO::WD working directory abstraction
676 natively, the case "[$wd, "."]" as $srcpath is specialcased -
677 instead of failing, "rename" is called on the absolute path of $wd.
678
679 aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
680 Basically a version of "aio_rename" with an additional $flags
681 argument. Calling this with "$flags=0" is the same as calling
682 "aio_rename".
683
684 Non-zero flags are currently only supported on GNU/Linux systems
685 that support renameat2. Other systems fail with "ENOSYS" in this
686 case.
687
688 The following constants are available (missing ones are, as usual
689 0), see renameat2(2) for details:
690
691 "IO::AIO::RENAME_NOREPLACE", "IO::AIO::RENAME_EXCHANGE" and
692 "IO::AIO::RENAME_WHITEOUT".
693
694 aio_mkdir $pathname, $mode, $callback->($status)
695 Asynchronously mkdir (create) a directory and call the callback with
696 the result code. $mode will be modified by the umask at the time the
697 request is executed, so do not change your umask.
698
175 aio_rmdir $pathname, $callback 699 aio_rmdir $pathname, $callback->($status)
176 Asynchronously rmdir (delete) a directory and call the callback with 700 Asynchronously rmdir (delete) a directory and call the callback with
177 the result code. 701 the result code.
178 702
703 On systems that support the AIO::WD working directory abstraction
704 natively, the case "[$wd, "."]" is specialcased - instead of
705 failing, "rmdir" is called on the absolute path of $wd.
706
707 aio_readdir $pathname, $callback->($entries)
708 Unlike the POSIX call of the same name, "aio_readdir" reads an
709 entire directory (i.e. opendir + readdir + closedir). The entries
710 will not be sorted, and will NOT include the "." and ".." entries.
711
712 The callback is passed a single argument which is either "undef" or
713 an array-ref with the filenames.
714
715 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
716 Quite similar to "aio_readdir", but the $flags argument allows one
717 to tune behaviour and output format. In case of an error, $entries
718 will be "undef".
719
720 The flags are a combination of the following constants, ORed
721 together (the flags will also be passed to the callback, possibly
722 modified):
723
724 IO::AIO::READDIR_DENTS
725 Normally the callback gets an arrayref consisting of names only
726 (as with "aio_readdir"). If this flag is set, then the callback
727 gets an arrayref with "[$name, $type, $inode]" arrayrefs, each
728 describing a single directory entry in more detail:
729
730 $name is the name of the entry.
731
732 $type is one of the "IO::AIO::DT_xxx" constants:
733
734 "IO::AIO::DT_UNKNOWN", "IO::AIO::DT_FIFO", "IO::AIO::DT_CHR",
735 "IO::AIO::DT_DIR", "IO::AIO::DT_BLK", "IO::AIO::DT_REG",
736 "IO::AIO::DT_LNK", "IO::AIO::DT_SOCK", "IO::AIO::DT_WHT".
737
738 "IO::AIO::DT_UNKNOWN" means just that: readdir does not know. If
739 you need to know, you have to run stat yourself. Also, for
740 speed/memory reasons, the $type scalars are read-only: you must
741 not modify them.
742
743 $inode is the inode number (which might not be exact on systems
744 with 64 bit inode numbers and 32 bit perls). This field has
745 unspecified content on systems that do not deliver the inode
746 information.
747
748 IO::AIO::READDIR_DIRS_FIRST
749 When this flag is set, then the names will be returned in an
750 order where likely directories come first, in optimal stat
751 order. This is useful when you need to quickly find directories,
752 or you want to find all directories while avoiding to stat()
753 each entry.
754
755 If the system returns type information in readdir, then this is
756 used to find directories directly. Otherwise, likely directories
757 are names beginning with ".", or otherwise names with no dots,
758 of which names with short names are tried first.
759
760 IO::AIO::READDIR_STAT_ORDER
761 When this flag is set, then the names will be returned in an
762 order suitable for stat()'ing each one. That is, when you plan
763 to stat() most or all files in the given directory, then the
764 returned order will likely be faster.
765
766 If both this flag and "IO::AIO::READDIR_DIRS_FIRST" are
767 specified, then the likely dirs come first, resulting in a less
768 optimal stat order for stat'ing all entries, but likely a more
769 optimal order for finding subdirectories.
770
771 IO::AIO::READDIR_FOUND_UNKNOWN
772 This flag should not be set when calling "aio_readdirx".
773 Instead, it is being set by "aio_readdirx", when any of the
774 $type's found were "IO::AIO::DT_UNKNOWN". The absence of this
775 flag therefore indicates that all $type's are known, which can
776 be used to speed up some algorithms.
777
778 aio_slurp $pathname, $offset, $length, $data, $callback->($status)
779 Opens, reads and closes the given file. The data is put into $data,
780 which is resized as required.
781
782 If $offset is negative, then it is counted from the end of the file.
783
784 If $length is zero, then the remaining length of the file is used.
785 Also, in this case, the same limitations to modifying $data apply as
786 when IO::AIO::mmap is used, i.e. it must only be modified in-place
787 with "substr". If the size of the file is known, specifying a
788 non-zero $length results in a performance advantage.
789
790 This request is similar to the older "aio_load" request, but since
791 it is a single request, it might be more efficient to use.
792
793 Example: load /etc/passwd into $passwd.
794
795 my $passwd;
796 aio_slurp "/etc/passwd", 0, 0, $passwd, sub {
797 $_[0] >= 0
798 or die "/etc/passwd: $!\n";
799
800 printf "/etc/passwd is %d bytes long, and contains:\n", length $passwd;
801 print $passwd;
802 };
803 IO::AIO::flush;
804
805 aio_load $pathname, $data, $callback->($status)
806 This is a composite request that tries to fully load the given file
807 into memory. Status is the same as with aio_read.
808
809 Using "aio_slurp" might be more efficient, as it is a single
810 request.
811
812 aio_copy $srcpath, $dstpath, $callback->($status)
813 Try to copy the *file* (directories not supported as either source
814 or destination) from $srcpath to $dstpath and call the callback with
815 a status of 0 (ok) or -1 (error, see $!).
816
817 Existing destination files will be truncated.
818
819 This is a composite request that creates the destination file with
820 mode 0200 and copies the contents of the source file into it using
821 "aio_sendfile", followed by restoring atime, mtime, access mode and
822 uid/gid, in that order.
823
824 If an error occurs, the partial destination file will be unlinked,
825 if possible, except when setting atime, mtime, access mode and
826 uid/gid, where errors are being ignored.
827
828 aio_move $srcpath, $dstpath, $callback->($status)
829 Try to move the *file* (directories not supported as either source
830 or destination) from $srcpath to $dstpath and call the callback with
831 a status of 0 (ok) or -1 (error, see $!).
832
833 This is a composite request that tries to rename(2) the file first;
834 if rename fails with "EXDEV", it copies the file with "aio_copy"
835 and, if that is successful, unlinks the $srcpath.
836
837 aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
838 Scans a directory (similar to "aio_readdir") but additionally tries
839 to efficiently separate the entries of directory $path into two sets
840 of names, directories you can recurse into (directories), and ones
841 you cannot recurse into (everything else, including symlinks to
842 directories).
843
844 "aio_scandir" is a composite request that generates many sub
845 requests. $maxreq specifies the maximum number of outstanding aio
846 requests that this function generates. If it is "<= 0", then a
847 suitable default will be chosen (currently 4).
848
849 On error, the callback is called without arguments, otherwise it
850 receives two array-refs with path-relative entry names.
851
852 Example:
853
854 aio_scandir $dir, 0, sub {
855 my ($dirs, $nondirs) = @_;
856 print "real directories: @$dirs\n";
857 print "everything else: @$nondirs\n";
858 };
859
860 Implementation notes.
861
862 The "aio_readdir" cannot be avoided, but "stat()"'ing every entry
863 can.
864
865 If readdir returns file type information, then this is used directly
866 to find directories.
867
868 Otherwise, after reading the directory, the modification time, size
869 etc. of the directory before and after the readdir is checked, and
870 if they match (and isn't the current time), the link count will be
871 used to decide how many entries are directories (if >= 2).
872 Otherwise, no knowledge of the number of subdirectories will be
873 assumed.
874
875 Then entries will be sorted into likely directories a non-initial
876 dot currently) and likely non-directories (see "aio_readdirx"). Then
877 every entry plus an appended "/." will be "stat"'ed, likely
878 directories first, in order of their inode numbers. If that
879 succeeds, it assumes that the entry is a directory or a symlink to
880 directory (which will be checked separately). This is often faster
881 than stat'ing the entry itself because filesystems might detect the
882 type of the entry without reading the inode data (e.g. ext2fs
883 filetype feature), even on systems that cannot return the filetype
884 information on readdir.
885
886 If the known number of directories (link count - 2) has been
887 reached, the rest of the entries is assumed to be non-directories.
888
889 This only works with certainty on POSIX (= UNIX) filesystems, which
890 fortunately are the vast majority of filesystems around.
891
892 It will also likely work on non-POSIX filesystems with reduced
893 efficiency as those tend to return 0 or 1 as link counts, which
894 disables the directory counting heuristic.
895
896 aio_rmtree $pathname, $callback->($status)
897 Delete a directory tree starting (and including) $path, return the
898 status of the final "rmdir" only. This is a composite request that
899 uses "aio_scandir" to recurse into and rmdir directories, and unlink
900 everything else.
901
902 aio_fcntl $fh, $cmd, $arg, $callback->($status)
903 aio_ioctl $fh, $request, $buf, $callback->($status)
904 These work just like the "fcntl" and "ioctl" built-in functions,
905 except they execute asynchronously and pass the return value to the
906 callback.
907
908 Both calls can be used for a lot of things, some of which make more
909 sense to run asynchronously in their own thread, while some others
910 make less sense. For example, calls that block waiting for external
911 events, such as locking, will also lock down an I/O thread while it
912 is waiting, which can deadlock the whole I/O system. At the same
913 time, there might be no alternative to using a thread to wait.
914
915 So in general, you should only use these calls for things that do
916 (filesystem) I/O, not for things that wait for other events
917 (network, other processes), although if you are careful and know
918 what you are doing, you still can.
919
920 The following constants are available and can be used for normal
921 "ioctl" and "fcntl" as well (missing ones are, as usual 0):
922
923 "F_DUPFD_CLOEXEC",
924
925 "F_OFD_GETLK", "F_OFD_SETLK", "F_OFD_GETLKW",
926
927 "FIFREEZE", "FITHAW", "FITRIM", "FICLONE", "FICLONERANGE",
928 "FIDEDUPERANGE".
929
930 "F_ADD_SEALS", "F_GET_SEALS", "F_SEAL_SEAL", "F_SEAL_SHRINK",
931 "F_SEAL_GROW" and "F_SEAL_WRITE".
932
933 "FS_IOC_GETFLAGS", "FS_IOC_SETFLAGS", "FS_IOC_GETVERSION",
934 "FS_IOC_SETVERSION", "FS_IOC_FIEMAP".
935
936 "FS_IOC_FSGETXATTR", "FS_IOC_FSSETXATTR",
937 "FS_IOC_SET_ENCRYPTION_POLICY", "FS_IOC_GET_ENCRYPTION_PWSALT",
938 "FS_IOC_GET_ENCRYPTION_POLICY", "FS_KEY_DESCRIPTOR_SIZE".
939
940 "FS_SECRM_FL", "FS_UNRM_FL", "FS_COMPR_FL", "FS_SYNC_FL",
941 "FS_IMMUTABLE_FL", "FS_APPEND_FL", "FS_NODUMP_FL", "FS_NOATIME_FL",
942 "FS_DIRTY_FL", "FS_COMPRBLK_FL", "FS_NOCOMP_FL", "FS_ENCRYPT_FL",
943 "FS_BTREE_FL", "FS_INDEX_FL", "FS_JOURNAL_DATA_FL", "FS_NOTAIL_FL",
944 "FS_DIRSYNC_FL", "FS_TOPDIR_FL", "FS_FL_USER_MODIFIABLE".
945
946 "FS_XFLAG_REALTIME", "FS_XFLAG_PREALLOC", "FS_XFLAG_IMMUTABLE",
947 "FS_XFLAG_APPEND", "FS_XFLAG_SYNC", "FS_XFLAG_NOATIME",
948 "FS_XFLAG_NODUMP", "FS_XFLAG_RTINHERIT", "FS_XFLAG_PROJINHERIT",
949 "FS_XFLAG_NOSYMLINKS", "FS_XFLAG_EXTSIZE", "FS_XFLAG_EXTSZINHERIT",
950 "FS_XFLAG_NODEFRAG", "FS_XFLAG_FILESTREAM", "FS_XFLAG_DAX",
951 "FS_XFLAG_HASATTR",
952
953 "BLKROSET", "BLKROGET", "BLKRRPART", "BLKGETSIZE", "BLKFLSBUF",
954 "BLKRASET", "BLKRAGET", "BLKFRASET", "BLKFRAGET", "BLKSECTSET",
955 "BLKSECTGET", "BLKSSZGET", "BLKBSZGET", "BLKBSZSET", "BLKGETSIZE64",
956
957 aio_sync $callback->($status)
958 Asynchronously call sync and call the callback when finished.
959
179 aio_fsync $fh, $callback 960 aio_fsync $fh, $callback->($status)
180 Asynchronously call fsync on the given filehandle and call the 961 Asynchronously call fsync on the given filehandle and call the
181 callback with the fsync result code. 962 callback with the fsync result code.
182 963
183 aio_fdatasync $fh, $callback 964 aio_fdatasync $fh, $callback->($status)
184 Asynchronously call fdatasync on the given filehandle and call the 965 Asynchronously call fdatasync on the given filehandle and call the
185 callback with the fdatasync result code. 966 callback with the fdatasync result code.
186 967
187 If this call isn't available because your OS lacks it or it couldn't 968 If this call isn't available because your OS lacks it or it couldn't
188 be detected, it will be emulated by calling "fsync" instead. 969 be detected, it will be emulated by calling "fsync" instead.
189 970
971 aio_syncfs $fh, $callback->($status)
972 Asynchronously call the syncfs syscall to sync the filesystem
973 associated to the given filehandle and call the callback with the
974 syncfs result code. If syncfs is not available, calls sync(), but
975 returns -1 and sets errno to "ENOSYS" nevertheless.
976
977 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
978 Sync the data portion of the file specified by $offset and $length
979 to disk (but NOT the metadata), by calling the Linux-specific
980 sync_file_range call. If sync_file_range is not available or it
981 returns ENOSYS, then fdatasync or fsync is being substituted.
982
983 $flags can be a combination of
984 "IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE",
985 "IO::AIO::SYNC_FILE_RANGE_WRITE" and
986 "IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER": refer to the sync_file_range
987 manpage for details.
988
989 aio_pathsync $pathname, $callback->($status)
990 This request tries to open, fsync and close the given path. This is
991 a composite request intended to sync directories after directory
992 operations (E.g. rename). This might not work on all operating
993 systems or have any specific effect, but usually it makes sure that
994 directory changes get written to disc. It works for anything that
995 can be opened for read-only, not just directories.
996
997 Future versions of this function might fall back to other methods
998 when "fsync" on the directory fails (such as calling "sync").
999
1000 Passes 0 when everything went ok, and -1 on error.
1001
1002 aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC,
1003 $callback->($status)
1004 This is a rather advanced IO::AIO call, which only works on
1005 mmap(2)ed scalars (see the "IO::AIO::mmap" function, although it
1006 also works on data scalars managed by the Sys::Mmap or Mmap modules,
1007 note that the scalar must only be modified in-place while an aio
1008 operation is pending on it).
1009
1010 It calls the "msync" function of your OS, if available, with the
1011 memory area starting at $offset in the string and ending $length
1012 bytes later. If $length is negative, counts from the end, and if
1013 $length is "undef", then it goes till the end of the string. The
1014 flags can be either "IO::AIO::MS_ASYNC" or "IO::AIO::MS_SYNC", plus
1015 an optional "IO::AIO::MS_INVALIDATE".
1016
1017 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0,
1018 $callback->($status)
1019 This is a rather advanced IO::AIO call, which works best on
1020 mmap(2)ed scalars.
1021
1022 It touches (reads or writes) all memory pages in the specified range
1023 inside the scalar. All caveats and parameters are the same as for
1024 "aio_msync", above, except for flags, which must be either 0 (which
1025 reads all pages and ensures they are instantiated) or
1026 "IO::AIO::MT_MODIFY", which modifies the memory pages (by reading
1027 and writing an octet from it, which dirties the page).
1028
1029 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
1030 This is a rather advanced IO::AIO call, which works best on
1031 mmap(2)ed scalars.
1032
1033 It reads in all the pages of the underlying storage into memory (if
1034 any) and locks them, so they are not getting swapped/paged out or
1035 removed.
1036
1037 If $length is undefined, then the scalar will be locked till the
1038 end.
1039
1040 On systems that do not implement "mlock", this function returns -1
1041 and sets errno to "ENOSYS".
1042
1043 Note that the corresponding "munlock" is synchronous and is
1044 documented under "MISCELLANEOUS FUNCTIONS".
1045
1046 Example: open a file, mmap and mlock it - both will be undone when
1047 $data gets destroyed.
1048
1049 open my $fh, "<", $path or die "$path: $!";
1050 my $data;
1051 IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
1052 aio_mlock $data; # mlock in background
1053
1054 aio_mlockall $flags, $callback->($status)
1055 Calls the "mlockall" function with the given $flags (a combination
1056 of "IO::AIO::MCL_CURRENT", "IO::AIO::MCL_FUTURE" and
1057 "IO::AIO::MCL_ONFAULT").
1058
1059 On systems that do not implement "mlockall", this function returns
1060 -1 and sets errno to "ENOSYS". Similarly, flag combinations not
1061 supported by the system result in a return value of -1 with errno
1062 being set to "EINVAL".
1063
1064 Note that the corresponding "munlockall" is synchronous and is
1065 documented under "MISCELLANEOUS FUNCTIONS".
1066
1067 Example: asynchronously lock all current and future pages into
1068 memory.
1069
1070 aio_mlockall IO::AIO::MCL_FUTURE;
1071
1072 aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
1073 Queries the extents of the given file (by calling the Linux "FIEMAP"
1074 ioctl, see <http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for
1075 details). If the ioctl is not available on your OS, then this
1076 request will fail with "ENOSYS".
1077
1078 $start is the starting offset to query extents for, $length is the
1079 size of the range to query - if it is "undef", then the whole file
1080 will be queried.
1081
1082 $flags is a combination of flags ("IO::AIO::FIEMAP_FLAG_SYNC" or
1083 "IO::AIO::FIEMAP_FLAG_XATTR" - "IO::AIO::FIEMAP_FLAGS_COMPAT" is
1084 also exported), and is normally 0 or "IO::AIO::FIEMAP_FLAG_SYNC" to
1085 query the data portion.
1086
1087 $count is the maximum number of extent records to return. If it is
1088 "undef", then IO::AIO queries all extents of the range. As a very
1089 special case, if it is 0, then the callback receives the number of
1090 extents instead of the extents themselves (which is unreliable, see
1091 below).
1092
1093 If an error occurs, the callback receives no arguments. The special
1094 "errno" value "IO::AIO::EBADR" is available to test for flag errors.
1095
1096 Otherwise, the callback receives an array reference with extent
1097 structures. Each extent structure is an array reference itself, with
1098 the following members:
1099
1100 [$logical, $physical, $length, $flags]
1101
1102 Flags is any combination of the following flag values (typically
1103 either 0 or "IO::AIO::FIEMAP_EXTENT_LAST" (1)):
1104
1105 "IO::AIO::FIEMAP_EXTENT_LAST", "IO::AIO::FIEMAP_EXTENT_UNKNOWN",
1106 "IO::AIO::FIEMAP_EXTENT_DELALLOC", "IO::AIO::FIEMAP_EXTENT_ENCODED",
1107 "IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED",
1108 "IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED",
1109 "IO::AIO::FIEMAP_EXTENT_DATA_INLINE",
1110 "IO::AIO::FIEMAP_EXTENT_DATA_TAIL",
1111 "IO::AIO::FIEMAP_EXTENT_UNWRITTEN", "IO::AIO::FIEMAP_EXTENT_MERGED"
1112 or "IO::AIO::FIEMAP_EXTENT_SHARED".
1113
1114 At the time of this writing (Linux 3.2), this request is unreliable
1115 unless $count is "undef", as the kernel has all sorts of bugs
1116 preventing it to return all extents of a range for files with a
1117 large number of extents. The code (only) works around all these
1118 issues if $count is "undef".
1119
1120 aio_group $callback->(...)
1121 This is a very special aio request: Instead of doing something, it
1122 is a container for other aio requests, which is useful if you want
1123 to bundle many requests into a single, composite, request with a
1124 definite callback and the ability to cancel the whole request with
1125 its subrequests.
1126
1127 Returns an object of class IO::AIO::GRP. See its documentation below
1128 for more info.
1129
1130 Example:
1131
1132 my $grp = aio_group sub {
1133 print "all stats done\n";
1134 };
1135
1136 add $grp
1137 (aio_stat ...),
1138 (aio_stat ...),
1139 ...;
1140
1141 aio_nop $callback->()
1142 This is a special request - it does nothing in itself and is only
1143 used for side effects, such as when you want to add a dummy request
1144 to a group so that finishing the requests in the group depends on
1145 executing the given code.
1146
1147 While this request does nothing, it still goes through the execution
1148 phase and still requires a worker thread. Thus, the callback will
1149 not be executed immediately but only after other requests in the
1150 queue have entered their execution phase. This can be used to
1151 measure request latency.
1152
1153 IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
1154 Mainly used for debugging and benchmarking, this aio request puts
1155 one of the request workers to sleep for the given time.
1156
1157 While it is theoretically handy to have simple I/O scheduling
1158 requests like sleep and file handle readable/writable, the overhead
1159 this creates is immense (it blocks a thread for a long time) so do
1160 not use this function except to put your application under
1161 artificial I/O pressure.
1162
1163 IO::AIO::WD - multiple working directories
1164 Your process only has one current working directory, which is used by
1165 all threads. This makes it hard to use relative paths (some other
1166 component could call "chdir" at any time, and it is hard to control when
1167 the path will be used by IO::AIO).
1168
1169 One solution for this is to always use absolute paths. This usually
1170 works, but can be quite slow (the kernel has to walk the whole path on
1171 every access), and can also be a hassle to implement.
1172
1173 Newer POSIX systems have a number of functions (openat, fdopendir,
1174 futimensat and so on) that make it possible to specify working
1175 directories per operation.
1176
1177 For portability, and because the clowns who "designed", or shall I
1178 write, perpetrated this new interface were obviously half-drunk, this
1179 abstraction cannot be perfect, though.
1180
1181 IO::AIO allows you to convert directory paths into a so-called
1182 IO::AIO::WD object. This object stores the canonicalised, absolute
1183 version of the path, and on systems that allow it, also a directory file
1184 descriptor.
1185
1186 Everywhere where a pathname is accepted by IO::AIO (e.g. in "aio_stat"
1187 or "aio_unlink"), one can specify an array reference with an IO::AIO::WD
1188 object and a pathname instead (or the IO::AIO::WD object alone, which
1189 gets interpreted as "[$wd, "."]"). If the pathname is absolute, the
1190 IO::AIO::WD object is ignored, otherwise the pathname is resolved
1191 relative to that IO::AIO::WD object.
1192
1193 For example, to get a wd object for /etc and then stat passwd inside,
1194 you would write:
1195
1196 aio_wd "/etc", sub {
1197 my $etcdir = shift;
1198
1199 # although $etcdir can be undef on error, there is generally no reason
1200 # to check for errors here, as aio_stat will fail with ENOENT
1201 # when $etcdir is undef.
1202
1203 aio_stat [$etcdir, "passwd"], sub {
1204 # yay
1205 };
1206 };
1207
1208 The fact that "aio_wd" is a request and not a normal function shows that
1209 creating an IO::AIO::WD object is itself a potentially blocking
1210 operation, which is why it is done asynchronously.
1211
1212 To stat the directory obtained with "aio_wd" above, one could write
1213 either of the following three request calls:
1214
1215 aio_lstat "/etc" , sub { ... # pathname as normal string
1216 aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
1217 aio_lstat $wd , sub { ... # shorthand for the previous
1218
1219 As with normal pathnames, IO::AIO keeps a copy of the working directory
1220 object and the pathname string, so you could write the following without
1221 causing any issues due to $path getting reused:
1222
1223 my $path = [$wd, undef];
1224
1225 for my $name (qw(abc def ghi)) {
1226 $path->[1] = $name;
1227 aio_stat $path, sub {
1228 # ...
1229 };
1230 }
1231
1232 There are some caveats: when directories get renamed (or deleted), the
1233 pathname string doesn't change, so will point to the new directory (or
1234 nowhere at all), while the directory fd, if available on the system,
1235 will still point to the original directory. Most functions accepting a
1236 pathname will use the directory fd on newer systems, and the string on
1237 older systems. Some functions (such as "aio_realpath") will always rely
1238 on the string form of the pathname.
1239
1240 So this functionality is mainly useful to get some protection against
1241 "chdir", to easily get an absolute path out of a relative path for
1242 future reference, and to speed up doing many operations in the same
1243 directory (e.g. when stat'ing all files in a directory).
1244
1245 The following functions implement this working directory abstraction:
1246
1247 aio_wd $pathname, $callback->($wd)
1248 Asynchonously canonicalise the given pathname and convert it to an
1249 IO::AIO::WD object representing it. If possible and supported on the
1250 system, also open a directory fd to speed up pathname resolution
1251 relative to this working directory.
1252
1253 If something goes wrong, then "undef" is passwd to the callback
1254 instead of a working directory object and $! is set appropriately.
1255 Since passing "undef" as working directory component of a pathname
1256 fails the request with "ENOENT", there is often no need for error
1257 checking in the "aio_wd" callback, as future requests using the
1258 value will fail in the expected way.
1259
1260 IO::AIO::CWD
1261 This is a compile time constant (object) that represents the process
1262 current working directory.
1263
1264 Specifying this object as working directory object for a pathname is
1265 as if the pathname would be specified directly, without a directory
1266 object. For example, these calls are functionally identical:
1267
1268 aio_stat "somefile", sub { ... };
1269 aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
1270
1271 To recover the path associated with an IO::AIO::WD object, you can use
1272 "aio_realpath":
1273
1274 aio_realpath $wd, sub {
1275 warn "path is $_[0]\n";
1276 };
1277
1278 Currently, "aio_statvfs" always, and "aio_rename" and "aio_rmdir"
1279 sometimes, fall back to using an absolue path.
1280
1281 IO::AIO::REQ CLASS
1282 All non-aggregate "aio_*" functions return an object of this class when
1283 called in non-void context.
1284
1285 cancel $req
1286 Cancels the request, if possible. Has the effect of skipping
1287 execution when entering the execute state and skipping calling the
1288 callback when entering the the result state, but will leave the
1289 request otherwise untouched (with the exception of readdir). That
1290 means that requests that currently execute will not be stopped and
1291 resources held by the request will not be freed prematurely.
1292
1293 cb $req $callback->(...)
1294 Replace (or simply set) the callback registered to the request.
1295
1296 IO::AIO::GRP CLASS
1297 This class is a subclass of IO::AIO::REQ, so all its methods apply to
1298 objects of this class, too.
1299
1300 A IO::AIO::GRP object is a special request that can contain multiple
1301 other aio requests.
1302
1303 You create one by calling the "aio_group" constructing function with a
1304 callback that will be called when all contained requests have entered
1305 the "done" state:
1306
1307 my $grp = aio_group sub {
1308 print "all requests are done\n";
1309 };
1310
1311 You add requests by calling the "add" method with one or more
1312 "IO::AIO::REQ" objects:
1313
1314 $grp->add (aio_unlink "...");
1315
1316 add $grp aio_stat "...", sub {
1317 $_[0] or return $grp->result ("error");
1318
1319 # add another request dynamically, if first succeeded
1320 add $grp aio_open "...", sub {
1321 $grp->result ("ok");
1322 };
1323 };
1324
1325 This makes it very easy to create composite requests (see the source of
1326 "aio_move" for an application) that work and feel like simple requests.
1327
1328 * The IO::AIO::GRP objects will be cleaned up during calls to
1329 "IO::AIO::poll_cb", just like any other request.
1330
1331 * They can be canceled like any other request. Canceling will cancel
1332 not only the request itself, but also all requests it contains.
1333
1334 * They can also can also be added to other IO::AIO::GRP objects.
1335
1336 * You must not add requests to a group from within the group callback
1337 (or any later time).
1338
1339 Their lifetime, simplified, looks like this: when they are empty, they
1340 will finish very quickly. If they contain only requests that are in the
1341 "done" state, they will also finish. Otherwise they will continue to
1342 exist.
1343
1344 That means after creating a group you have some time to add requests
1345 (precisely before the callback has been invoked, which is only done
1346 within the "poll_cb"). And in the callbacks of those requests, you can
1347 add further requests to the group. And only when all those requests have
1348 finished will the the group itself finish.
1349
1350 add $grp ...
1351 $grp->add (...)
1352 Add one or more requests to the group. Any type of IO::AIO::REQ can
1353 be added, including other groups, as long as you do not create
1354 circular dependencies.
1355
1356 Returns all its arguments.
1357
1358 $grp->cancel_subs
1359 Cancel all subrequests and clears any feeder, but not the group
1360 request itself. Useful when you queued a lot of events but got a
1361 result early.
1362
1363 The group request will finish normally (you cannot add requests to
1364 the group).
1365
1366 $grp->result (...)
1367 Set the result value(s) that will be passed to the group callback
1368 when all subrequests have finished and set the groups errno to the
1369 current value of errno (just like calling "errno" without an error
1370 number). By default, no argument will be passed and errno is zero.
1371
1372 $grp->errno ([$errno])
1373 Sets the group errno value to $errno, or the current value of errno
1374 when the argument is missing.
1375
1376 Every aio request has an associated errno value that is restored
1377 when the callback is invoked. This method lets you change this value
1378 from its default (0).
1379
1380 Calling "result" will also set errno, so make sure you either set $!
1381 before the call to "result", or call c<errno> after it.
1382
1383 feed $grp $callback->($grp)
1384 Sets a feeder/generator on this group: every group can have an
1385 attached generator that generates requests if idle. The idea behind
1386 this is that, although you could just queue as many requests as you
1387 want in a group, this might starve other requests for a potentially
1388 long time. For example, "aio_scandir" might generate hundreds of
1389 thousands of "aio_stat" requests, delaying any later requests for a
1390 long time.
1391
1392 To avoid this, and allow incremental generation of requests, you can
1393 instead a group and set a feeder on it that generates those
1394 requests. The feed callback will be called whenever there are few
1395 enough (see "limit", below) requests active in the group itself and
1396 is expected to queue more requests.
1397
1398 The feed callback can queue as many requests as it likes (i.e. "add"
1399 does not impose any limits).
1400
1401 If the feed does not queue more requests when called, it will be
1402 automatically removed from the group.
1403
1404 If the feed limit is 0 when this method is called, it will be set to
1405 2 automatically.
1406
1407 Example:
1408
1409 # stat all files in @files, but only ever use four aio requests concurrently:
1410
1411 my $grp = aio_group sub { print "finished\n" };
1412 limit $grp 4;
1413 feed $grp sub {
1414 my $file = pop @files
1415 or return;
1416
1417 add $grp aio_stat $file, sub { ... };
1418 };
1419
1420 limit $grp $num
1421 Sets the feeder limit for the group: The feeder will be called
1422 whenever the group contains less than this many requests.
1423
1424 Setting the limit to 0 will pause the feeding process.
1425
1426 The default value for the limit is 0, but note that setting a feeder
1427 automatically bumps it up to 2.
1428
190 SUPPORT FUNCTIONS 1429 SUPPORT FUNCTIONS
1430 EVENT PROCESSING AND EVENT LOOP INTEGRATION
191 $fileno = IO::AIO::poll_fileno 1431 $fileno = IO::AIO::poll_fileno
192 Return the *request result pipe file descriptor*. This filehandle 1432 Return the *request result pipe file descriptor*. This filehandle
193 must be polled for reading by some mechanism outside this module 1433 must be polled for reading by some mechanism outside this module
194 (e.g. Event or select, see below or the SYNOPSIS). If the pipe 1434 (e.g. EV, Glib, select and so on, see below or the SYNOPSIS). If the
195 becomes readable you have to call "poll_cb" to check the results. 1435 pipe becomes readable you have to call "poll_cb" to check the
1436 results.
196 1437
197 See "poll_cb" for an example. 1438 See "poll_cb" for an example.
198 1439
199 IO::AIO::poll_cb 1440 IO::AIO::poll_cb
200 Process all outstanding events on the result pipe. You have to call 1441 Process some requests that have reached the result phase (i.e. they
201 this regularly. Returns the number of events processed. Returns 1442 have been executed but the results are not yet reported). You have
1443 to call this "regularly" to finish outstanding requests.
1444
1445 Returns 0 if all events could be processed (or there were no events
1446 to process), or -1 if it returned earlier for whatever reason.
202 immediately when no events are outstanding. 1447 Returns immediately when no events are outstanding. The amount of
1448 events processed depends on the settings of "IO::AIO::max_poll_req",
1449 "IO::AIO::max_poll_time" and "IO::AIO::max_outstanding".
1450
1451 If not all requests were processed for whatever reason, the poll
1452 file descriptor will still be ready when "poll_cb" returns, so
1453 normally you don't have to do anything special to have it called
1454 later.
1455
1456 Apart from calling "IO::AIO::poll_cb" when the event filehandle
1457 becomes ready, it can be beneficial to call this function from loops
1458 which submit a lot of requests, to make sure the results get
1459 processed when they become available and not just when the loop is
1460 finished and the event loop takes over again. This function returns
1461 very fast when there are no outstanding requests.
203 1462
204 Example: Install an Event watcher that automatically calls 1463 Example: Install an Event watcher that automatically calls
205 IO::AIO::poll_cb with high priority: 1464 IO::AIO::poll_cb with high priority (more examples can be found in
1465 the SYNOPSIS section, at the top of this document):
206 1466
207 Event->io (fd => IO::AIO::poll_fileno, 1467 Event->io (fd => IO::AIO::poll_fileno,
208 poll => 'r', async => 1, 1468 poll => 'r', async => 1,
209 cb => \&IO::AIO::poll_cb); 1469 cb => \&IO::AIO::poll_cb);
210 1470
211 IO::AIO::poll_wait 1471 IO::AIO::poll_wait
212 Wait till the result filehandle becomes ready for reading (simply 1472 Wait until either at least one request is in the result phase or no
213 does a "select" on the filehandle. This is useful if you want to 1473 requests are outstanding anymore.
214 synchronously wait for some requests to finish). 1474
1475 This is useful if you want to synchronously wait for some requests
1476 to become ready, without actually handling them.
215 1477
216 See "nreqs" for an example. 1478 See "nreqs" for an example.
217 1479
1480 IO::AIO::poll
1481 Waits until some requests have been handled.
1482
1483 Returns the number of requests processed, but is otherwise strictly
1484 equivalent to:
1485
1486 IO::AIO::poll_wait, IO::AIO::poll_cb
1487
218 IO::AIO::nreqs 1488 IO::AIO::flush
219 Returns the number of requests currently outstanding (i.e. for which 1489 Wait till all outstanding AIO requests have been handled.
220 their callback has not been invoked yet).
221 1490
222 Example: wait till there are no outstanding requests anymore: 1491 Strictly equivalent to:
223 1492
224 IO::AIO::poll_wait, IO::AIO::poll_cb 1493 IO::AIO::poll_wait, IO::AIO::poll_cb
225 while IO::AIO::nreqs; 1494 while IO::AIO::nreqs;
226 1495
1496 This function can be useful at program aborts, to make sure
1497 outstanding I/O has been done ("IO::AIO" uses an "END" block which
1498 already calls this function on normal exits), or when you are merely
1499 using "IO::AIO" for its more advanced functions, rather than for
1500 async I/O, e.g.:
1501
1502 my ($dirs, $nondirs);
1503 IO::AIO::aio_scandir "/tmp", 0, sub { ($dirs, $nondirs) = @_ };
227 IO::AIO::flush 1504 IO::AIO::flush;
228 Wait till all outstanding AIO requests have been handled. 1505 # $dirs, $nondirs are now set
229 1506
230 Strictly equivalent to: 1507 IO::AIO::max_poll_reqs $nreqs
1508 IO::AIO::max_poll_time $seconds
1509 These set the maximum number of requests (default 0, meaning
1510 infinity) that are being processed by "IO::AIO::poll_cb" in one
1511 call, respectively the maximum amount of time (default 0, meaning
1512 infinity) spent in "IO::AIO::poll_cb" to process requests (more
1513 correctly the mininum amount of time "poll_cb" is allowed to use).
231 1514
232 IO::AIO::poll_wait, IO::AIO::poll_cb 1515 Setting "max_poll_time" to a non-zero value creates an overhead of
233 while IO::AIO::nreqs; 1516 one syscall per request processed, which is not normally a problem
1517 unless your callbacks are really really fast or your OS is really
1518 really slow (I am not mentioning Solaris here). Using
1519 "max_poll_reqs" incurs no overhead.
234 1520
235 IO::AIO::poll 1521 Setting these is useful if you want to ensure some level of
236 Waits until some requests have been handled. 1522 interactiveness when perl is not fast enough to process all requests
1523 in time.
237 1524
238 Strictly equivalent to: 1525 For interactive programs, values such as 0.01 to 0.1 should be fine.
239 1526
240 IO::AIO::poll_wait, IO::AIO::poll_cb 1527 Example: Install an Event watcher that automatically calls
241 if IO::AIO::nreqs; 1528 IO::AIO::poll_cb with low priority, to ensure that other parts of
1529 the program get the CPU sometimes even under high AIO load.
242 1530
1531 # try not to spend much more than 0.1s in poll_cb
1532 IO::AIO::max_poll_time 0.1;
1533
1534 # use a low priority so other tasks have priority
1535 Event->io (fd => IO::AIO::poll_fileno,
1536 poll => 'r', nice => 1,
1537 cb => &IO::AIO::poll_cb);
1538
1539 CONTROLLING THE NUMBER OF THREADS
243 IO::AIO::min_parallel $nthreads 1540 IO::AIO::min_parallel $nthreads
244 Set the minimum number of AIO threads to $nthreads. The default is 1541 Set the minimum number of AIO threads to $nthreads. The current
245 1, which means a single asynchronous operation can be done at one 1542 default is 8, which means eight asynchronous operations can execute
246 time (the number of outstanding operations, however, is unlimited). 1543 concurrently at any one time (the number of outstanding requests,
1544 however, is unlimited).
247 1545
1546 IO::AIO starts threads only on demand, when an AIO request is queued
1547 and no free thread exists. Please note that queueing up a hundred
1548 requests can create demand for a hundred threads, even if it turns
1549 out that everything is in the cache and could have been processed
1550 faster by a single thread.
1551
248 It is recommended to keep the number of threads low, as some Linux 1552 It is recommended to keep the number of threads relatively low, as
249 kernel versions will scale negatively with the number of threads 1553 some Linux kernel versions will scale negatively with the number of
250 (higher parallelity => MUCH higher latency). With current Linux 2.6 1554 threads (higher parallelity => MUCH higher latency). With current
251 versions, 4-32 threads should be fine. 1555 Linux 2.6 versions, 4-32 threads should be fine.
252 1556
253 Under normal circumstances you don't need to call this function, as 1557 Under most circumstances you don't need to call this function, as
254 this module automatically starts some threads (the exact number 1558 the module selects a default that is suitable for low to moderate
255 might change, and is currently 4). 1559 load.
256 1560
257 IO::AIO::max_parallel $nthreads 1561 IO::AIO::max_parallel $nthreads
258 Sets the maximum number of AIO threads to $nthreads. If more than 1562 Sets the maximum number of AIO threads to $nthreads. If more than
259 the specified number of threads are currently running, kill them. 1563 the specified number of threads are currently running, this function
260 This function blocks until the limit is reached. 1564 kills them. This function blocks until the limit is reached.
1565
1566 While $nthreads are zero, aio requests get queued but not executed
1567 until the number of threads has been increased again.
261 1568
262 This module automatically runs "max_parallel 0" at program end, to 1569 This module automatically runs "max_parallel 0" at program end, to
263 ensure that all threads are killed and that there are no outstanding 1570 ensure that all threads are killed and that there are no outstanding
264 requests. 1571 requests.
265 1572
266 Under normal circumstances you don't need to call this function. 1573 Under normal circumstances you don't need to call this function.
267 1574
1575 IO::AIO::max_idle $nthreads
1576 Limit the number of threads (default: 4) that are allowed to idle
1577 (i.e., threads that did not get a request to process within the idle
1578 timeout (default: 10 seconds). That means if a thread becomes idle
1579 while $nthreads other threads are also idle, it will free its
1580 resources and exit.
1581
1582 This is useful when you allow a large number of threads (e.g. 100 or
1583 1000) to allow for extremely high load situations, but want to free
1584 resources under normal circumstances (1000 threads can easily
1585 consume 30MB of RAM).
1586
1587 The default is probably ok in most situations, especially if thread
1588 creation is fast. If thread creation is very slow on your system you
1589 might want to use larger values.
1590
1591 IO::AIO::idle_timeout $seconds
1592 Sets the minimum idle timeout (default 10) after which worker
1593 threads are allowed to exit. SEe "IO::AIO::max_idle".
1594
268 $oldnreqs = IO::AIO::max_outstanding $nreqs 1595 IO::AIO::max_outstanding $maxreqs
269 Sets the maximum number of outstanding requests to $nreqs. If you 1596 Sets the maximum number of outstanding requests to $nreqs. If you do
270 try to queue up more than this number of requests, the caller will 1597 queue up more than this number of requests, the next call to
271 block until some requests have been handled. 1598 "IO::AIO::poll_cb" (and other functions calling "poll_cb", such as
1599 "IO::AIO::flush" or "IO::AIO::poll") will block until the limit is
1600 no longer exceeded.
272 1601
273 The default is very large, so normally there is no practical limit. 1602 In other words, this setting does not enforce a queue limit, but can
274 If you queue up many requests in a loop it it often improves speed 1603 be used to make poll functions block if the limit is exceeded.
275 if you set this to a relatively low number, such as 100.
276 1604
277 Under normal circumstances you don't need to call this function. 1605 This is a bad function to use in interactive programs because it
1606 blocks, and a bad way to reduce concurrency because it is inexact.
1607 If you need to issue many requests without being able to call a poll
1608 function on demand, it is better to use an "aio_group" together with
1609 a feed callback.
1610
1611 Its main use is in scripts without an event loop - when you want to
1612 stat a lot of files, you can write something like this:
1613
1614 IO::AIO::max_outstanding 32;
1615
1616 for my $path (...) {
1617 aio_stat $path , ...;
1618 IO::AIO::poll_cb;
1619 }
1620
1621 IO::AIO::flush;
1622
1623 The call to "poll_cb" inside the loop will normally return
1624 instantly, allowing the loop to progress, but as soon as more than
1625 32 requests are in-flight, it will block until some requests have
1626 been handled. This keeps the loop from pushing a large number of
1627 "aio_stat" requests onto the queue (which, with many paths to stat,
1628 can use up a lot of memory).
1629
1630 The default value for "max_outstanding" is very large, so there is
1631 no practical limit on the number of outstanding requests.
1632
1633 STATISTICAL INFORMATION
1634 IO::AIO::nreqs
1635 Returns the number of requests currently in the ready, execute or
1636 pending states (i.e. for which their callback has not been invoked
1637 yet).
1638
1639 Example: wait till there are no outstanding requests anymore:
1640
1641 IO::AIO::poll_wait, IO::AIO::poll_cb
1642 while IO::AIO::nreqs;
1643
1644 IO::AIO::nready
1645 Returns the number of requests currently in the ready state (not yet
1646 executed).
1647
1648 IO::AIO::npending
1649 Returns the number of requests currently in the pending state
1650 (executed, but not yet processed by poll_cb).
1651
1652 SUBSECOND STAT TIME ACCESS
1653 Both "aio_stat"/"aio_lstat" and perl's "stat"/"lstat" functions can
1654 generally find access/modification and change times with subsecond time
1655 accuracy of the system supports it, but perl's built-in functions only
1656 return the integer part.
1657
1658 The following functions return the timestamps of the most recent stat
1659 with subsecond precision on most systems and work both after
1660 "aio_stat"/"aio_lstat" and perl's "stat"/"lstat" calls. Their return
1661 value is only meaningful after a successful "stat"/"lstat" call, or
1662 during/after a successful "aio_stat"/"aio_lstat" callback.
1663
1664 This is similar to the Time::HiRes "stat" functions, but can return full
1665 resolution without rounding and work with standard perl "stat",
1666 alleviating the need to call the special "Time::HiRes" functions, which
1667 do not act like their perl counterparts.
1668
1669 On operating systems or file systems where subsecond time resolution is
1670 not supported or could not be detected, a fractional part of 0 is
1671 returned, so it is always safe to call these functions.
1672
1673 $seconds = IO::AIO::st_atime, IO::AIO::st_mtime, IO::AIO::st_ctime,
1674 IO::AIO::st_btime
1675 Return the access, modication, change or birth time, respectively,
1676 including fractional part. Due to the limited precision of floating
1677 point, the accuracy on most platforms is only a bit better than
1678 milliseconds for times around now - see the *nsec* function family,
1679 below, for full accuracy.
1680
1681 File birth time is only available when the OS and perl support it
1682 (on FreeBSD and NetBSD at the time of this writing, although support
1683 is adaptive, so if your OS/perl gains support, IO::AIO can take
1684 advantage of it). On systems where it isn't available, 0 is
1685 currently returned, but this might change to "undef" in a future
1686 version.
1687
1688 ($atime, $mtime, $ctime, $btime, ...) = IO::AIO::st_xtime
1689 Returns access, modification, change and birth time all in one go,
1690 and maybe more times in the future version.
1691
1692 $nanoseconds = IO::AIO::st_atimensec, IO::AIO::st_mtimensec,
1693 IO::AIO::st_ctimensec, IO::AIO::st_btimensec
1694 Return the fractional access, modifcation, change or birth time, in
1695 nanoseconds, as an integer in the range 0 to 999999999.
1696
1697 Note that no accessors are provided for access, modification and
1698 change times - you need to get those from "stat _" if required ("int
1699 IO::AIO::st_atime" and so on will *not* generally give you the
1700 correct value).
1701
1702 $seconds = IO::AIO::st_btimesec
1703 The (integral) seconds part of the file birth time, if available.
1704
1705 ($atime, $mtime, $ctime, $btime, ...) = IO::AIO::st_xtimensec
1706 Like the functions above, but returns all four times in one go (and
1707 maybe more in future versions).
1708
1709 $counter = IO::AIO::st_gen
1710 Returns the generation counter (in practice this is just a random
1711 number) of the file. This is only available on platforms which have
1712 this member in their "struct stat" (most BSDs at the time of this
1713 writing) and generally only to the root usert. If unsupported, 0 is
1714 returned, but this might change to "undef" in a future version.
1715
1716 Example: print the high resolution modification time of /etc, using
1717 "stat", and "IO::AIO::aio_stat".
1718
1719 if (stat "/etc") {
1720 printf "stat(/etc) mtime: %f\n", IO::AIO::st_mtime;
1721 }
1722
1723 IO::AIO::aio_stat "/etc", sub {
1724 $_[0]
1725 and return;
1726
1727 printf "aio_stat(/etc) mtime: %d.%09d\n", (stat _)[9], IO::AIO::st_mtimensec;
1728 };
1729
1730 IO::AIO::flush;
1731
1732 Output of the awbove on my system, showing reduced and full accuracy:
1733
1734 stat(/etc) mtime: 1534043702.020808
1735 aio_stat(/etc) mtime: 1534043702.020807792
1736
1737 MISCELLANEOUS FUNCTIONS
1738 IO::AIO implements some functions that are useful when you want to use
1739 some "Advanced I/O" function not available to in Perl, without going the
1740 "Asynchronous I/O" route. Many of these have an asynchronous "aio_*"
1741 counterpart.
1742
1743 $retval = IO::AIO::fexecve $fh, $argv, $envp
1744 A more-or-less direct equivalent to the POSIX "fexecve" functions,
1745 which allows you to specify the program to be executed via a file
1746 descriptor (or handle). Returns -1 and sets errno to "ENOSYS" if not
1747 available.
1748
1749 $retval = IO::AIO::mount $special, $path, $fstype, $flags = 0, $data =
1750 undef
1751 Calls the GNU/Linux mount syscall with the given arguments. All
1752 except $flags are strings, and if $data is "undef", a "NULL" will be
1753 passed.
1754
1755 The following values for $flags are available:
1756
1757 "IO::AIO::MS_RDONLY", "IO::AIO::MS_NOSUID", "IO::AIO::MS_NODEV",
1758 "IO::AIO::MS_NOEXEC", "IO::AIO::MS_SYNCHRONOUS",
1759 "IO::AIO::MS_REMOUNT", "IO::AIO::MS_MANDLOCK",
1760 "IO::AIO::MS_DIRSYNC", "IO::AIO::MS_NOATIME",
1761 "IO::AIO::MS_NODIRATIME", "IO::AIO::MS_BIND", "IO::AIO::MS_MOVE",
1762 "IO::AIO::MS_REC", "IO::AIO::MS_SILENT", "IO::AIO::MS_POSIXACL",
1763 "IO::AIO::MS_UNBINDABLE", "IO::AIO::MS_PRIVATE",
1764 "IO::AIO::MS_SLAVE", "IO::AIO::MS_SHARED", "IO::AIO::MS_RELATIME",
1765 "IO::AIO::MS_KERNMOUNT", "IO::AIO::MS_I_VERSION",
1766 "IO::AIO::MS_STRICTATIME", "IO::AIO::MS_LAZYTIME",
1767 "IO::AIO::MS_ACTIVE", "IO::AIO::MS_NOUSER", "IO::AIO::MS_RMT_MASK",
1768 "IO::AIO::MS_MGC_VAL" and "IO::AIO::MS_MGC_MSK".
1769
1770 $retval = IO::AIO::umount $path, $flags = 0
1771 Invokes the GNU/Linux "umount" or "umount2" syscalls. Always calls
1772 "umount" if $flags is 0, otherwqise always tries to call "umount2".
1773
1774 The following $flags are available:
1775
1776 "IO::AIO::MNT_FORCE", "IO::AIO::MNT_DETACH", "IO::AIO::MNT_EXPIRE"
1777 and "IO::AIO::UMOUNT_NOFOLLOW".
1778
1779 $numfd = IO::AIO::get_fdlimit
1780 Tries to find the current file descriptor limit and returns it, or
1781 "undef" and sets $! in case of an error. The limit is one larger
1782 than the highest valid file descriptor number.
1783
1784 IO::AIO::min_fdlimit [$numfd]
1785 Try to increase the current file descriptor limit(s) to at least
1786 $numfd by changing the soft or hard file descriptor resource limit.
1787 If $numfd is missing, it will try to set a very high limit, although
1788 this is not recommended when you know the actual minimum that you
1789 require.
1790
1791 If the limit cannot be raised enough, the function makes a
1792 best-effort attempt to increase the limit as much as possible, using
1793 various tricks, while still failing. You can query the resulting
1794 limit using "IO::AIO::get_fdlimit".
1795
1796 If an error occurs, returns "undef" and sets $!, otherwise returns
1797 true.
1798
1799 IO::AIO::sendfile $ofh, $ifh, $offset, $count
1800 Calls the "eio_sendfile_sync" function, which is like
1801 "aio_sendfile", but is blocking (this makes most sense if you know
1802 the input data is likely cached already and the output filehandle is
1803 set to non-blocking operations).
1804
1805 Returns the number of bytes copied, or -1 on error.
1806
1807 IO::AIO::fadvise $fh, $offset, $len, $advice
1808 Simply calls the "posix_fadvise" function (see its manpage for
1809 details). The following advice constants are available:
1810 "IO::AIO::FADV_NORMAL", "IO::AIO::FADV_SEQUENTIAL",
1811 "IO::AIO::FADV_RANDOM", "IO::AIO::FADV_NOREUSE",
1812 "IO::AIO::FADV_WILLNEED", "IO::AIO::FADV_DONTNEED".
1813
1814 On systems that do not implement "posix_fadvise", this function
1815 returns ENOSYS, otherwise the return value of "posix_fadvise".
1816
1817 IO::AIO::madvise $scalar, $offset, $len, $advice
1818 Simply calls the "posix_madvise" function (see its manpage for
1819 details). The following advice constants are available:
1820 "IO::AIO::MADV_NORMAL", "IO::AIO::MADV_SEQUENTIAL",
1821 "IO::AIO::MADV_RANDOM", "IO::AIO::MADV_WILLNEED",
1822 "IO::AIO::MADV_DONTNEED".
1823
1824 If $offset is negative, counts from the end. If $length is negative,
1825 the remaining length of the $scalar is used. If possible, $length
1826 will be reduced to fit into the $scalar.
1827
1828 On systems that do not implement "posix_madvise", this function
1829 returns ENOSYS, otherwise the return value of "posix_madvise".
1830
1831 IO::AIO::mprotect $scalar, $offset, $len, $protect
1832 Simply calls the "mprotect" function on the preferably AIO::mmap'ed
1833 $scalar (see its manpage for details). The following protect
1834 constants are available: "IO::AIO::PROT_NONE", "IO::AIO::PROT_READ",
1835 "IO::AIO::PROT_WRITE", "IO::AIO::PROT_EXEC".
1836
1837 If $offset is negative, counts from the end. If $length is negative,
1838 the remaining length of the $scalar is used. If possible, $length
1839 will be reduced to fit into the $scalar.
1840
1841 On systems that do not implement "mprotect", this function returns
1842 ENOSYS, otherwise the return value of "mprotect".
1843
1844 IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
1845 Memory-maps a file (or anonymous memory range) and attaches it to
1846 the given $scalar, which will act like a string scalar. Returns true
1847 on success, and false otherwise.
1848
1849 The scalar must exist, but its contents do not matter - this means
1850 you cannot use a nonexistant array or hash element. When in doubt,
1851 "undef" the scalar first.
1852
1853 The only operations allowed on the mmapped scalar are
1854 "substr"/"vec", which don't change the string length, and most
1855 read-only operations such as copying it or searching it with regexes
1856 and so on.
1857
1858 Anything else is unsafe and will, at best, result in memory leaks.
1859
1860 The memory map associated with the $scalar is automatically removed
1861 when the $scalar is undef'd or destroyed, or when the
1862 "IO::AIO::mmap" or "IO::AIO::munmap" functions are called on it.
1863
1864 This calls the "mmap"(2) function internally. See your system's
1865 manual page for details on the $length, $prot and $flags parameters.
1866
1867 The $length must be larger than zero and smaller than the actual
1868 filesize.
1869
1870 $prot is a combination of "IO::AIO::PROT_NONE",
1871 "IO::AIO::PROT_EXEC", "IO::AIO::PROT_READ" and/or
1872 "IO::AIO::PROT_WRITE",
1873
1874 $flags can be a combination of "IO::AIO::MAP_SHARED" or
1875 "IO::AIO::MAP_PRIVATE", or a number of system-specific flags (when
1876 not available, the are 0): "IO::AIO::MAP_ANONYMOUS" (which is set to
1877 "MAP_ANON" if your system only provides this constant),
1878 "IO::AIO::MAP_LOCKED", "IO::AIO::MAP_NORESERVE",
1879 "IO::AIO::MAP_POPULATE", "IO::AIO::MAP_NONBLOCK",
1880 "IO::AIO::MAP_FIXED", "IO::AIO::MAP_GROWSDOWN",
1881 "IO::AIO::MAP_32BIT", "IO::AIO::MAP_HUGETLB", "IO::AIO::MAP_STACK",
1882 "IO::AIO::MAP_FIXED_NOREPLACE", "IO::AIO::MAP_SHARED_VALIDATE",
1883 "IO::AIO::MAP_SYNC" or "IO::AIO::MAP_UNINITIALIZED".
1884
1885 If $fh is "undef", then a file descriptor of -1 is passed.
1886
1887 $offset is the offset from the start of the file - it generally must
1888 be a multiple of "IO::AIO::PAGESIZE" and defaults to 0.
1889
1890 Example:
1891
1892 use Digest::MD5;
1893 use IO::AIO;
1894
1895 open my $fh, "<verybigfile"
1896 or die "$!";
1897
1898 IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
1899 or die "verybigfile: $!";
1900
1901 my $fast_md5 = md5 $data;
1902
1903 IO::AIO::munmap $scalar
1904 Removes a previous mmap and undefines the $scalar.
1905
1906 IO::AIO::mremap $scalar, $new_length, $flags = MREMAP_MAYMOVE[,
1907 $new_address = 0]
1908 Calls the Linux-specific mremap(2) system call. The $scalar must
1909 have been mapped by "IO::AIO::mmap", and $flags must currently
1910 either be 0 or "IO::AIO::MREMAP_MAYMOVE".
1911
1912 Returns true if successful, and false otherwise. If the underlying
1913 mmapped region has changed address, then the true value has the
1914 numerical value 1, otherwise it has the numerical value 0:
1915
1916 my $success = IO::AIO::mremap $mmapped, 8192, IO::AIO::MREMAP_MAYMOVE
1917 or die "mremap: $!";
1918
1919 if ($success*1) {
1920 warn "scalar has chanegd address in memory\n";
1921 }
1922
1923 "IO::AIO::MREMAP_FIXED" and the $new_address argument are currently
1924 implemented, but not supported and might go away in a future
1925 version.
1926
1927 On systems where this call is not supported or is not emulated, this
1928 call returns falls and sets $! to "ENOSYS".
1929
1930 IO::AIO::mlockall $flags
1931 Calls the "eio_mlockall_sync" function, which is like
1932 "aio_mlockall", but is blocking.
1933
1934 IO::AIO::munlock $scalar, $offset = 0, $length = undef
1935 Calls the "munlock" function, undoing the effects of a previous
1936 "aio_mlock" call (see its description for details).
1937
1938 IO::AIO::munlockall
1939 Calls the "munlockall" function.
1940
1941 On systems that do not implement "munlockall", this function returns
1942 ENOSYS, otherwise the return value of "munlockall".
1943
1944 $fh = IO::AIO::accept4 $r_fh, $sockaddr, $sockaddr_maxlen, $flags
1945 Uses the GNU/Linux accept4(2) syscall, if available, to accept a
1946 socket and return the new file handle on success, or sets $! and
1947 returns "undef" on error.
1948
1949 The remote name of the new socket will be stored in $sockaddr, which
1950 will be extended to allow for at least $sockaddr_maxlen octets. If
1951 the socket name does not fit into $sockaddr_maxlen octets, this is
1952 signaled by returning a longer string in $sockaddr, which might or
1953 might not be truncated.
1954
1955 To accept name-less sockets, use "undef" for $sockaddr and 0 for
1956 $sockaddr_maxlen.
1957
1958 The main reasons to use this syscall rather than portable accept(2)
1959 are that you can specify "SOCK_NONBLOCK" and/or "SOCK_CLOEXEC" flags
1960 and you can accept name-less sockets by specifying 0 for
1961 $sockaddr_maxlen, which is sadly not possible with perl's interface
1962 to "accept".
1963
1964 IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
1965 Calls the GNU/Linux splice(2) syscall, if available. If $r_off or
1966 $w_off are "undef", then "NULL" is passed for these, otherwise they
1967 should be the file offset.
1968
1969 $r_fh and $w_fh should not refer to the same file, as splice might
1970 silently corrupt the data in this case.
1971
1972 The following symbol flag values are available:
1973 "IO::AIO::SPLICE_F_MOVE", "IO::AIO::SPLICE_F_NONBLOCK",
1974 "IO::AIO::SPLICE_F_MORE" and "IO::AIO::SPLICE_F_GIFT".
1975
1976 See the splice(2) manpage for details.
1977
1978 IO::AIO::tee $r_fh, $w_fh, $length, $flags
1979 Calls the GNU/Linux tee(2) syscall, see its manpage and the
1980 description for "IO::AIO::splice" above for details.
1981
1982 $actual_size = IO::AIO::pipesize $r_fh[, $new_size]
1983 Attempts to query or change the pipe buffer size. Obviously works
1984 only on pipes, and currently works only on GNU/Linux systems, and
1985 fails with -1/"ENOSYS" everywhere else. If anybody knows how to
1986 influence pipe buffer size on other systems, drop me a note.
1987
1988 ($rfh, $wfh) = IO::AIO::pipe2 [$flags]
1989 This is a direct interface to the Linux pipe2(2) system call. If
1990 $flags is missing or 0, then this should be the same as a call to
1991 perl's built-in "pipe" function and create a new pipe, and works on
1992 systems that lack the pipe2 syscall. On win32, this case invokes
1993 "_pipe (..., 4096, O_BINARY)".
1994
1995 If $flags is non-zero, it tries to invoke the pipe2 system call with
1996 the given flags (Linux 2.6.27, glibc 2.9).
1997
1998 On success, the read and write file handles are returned.
1999
2000 On error, nothing will be returned. If the pipe2 syscall is missing
2001 and $flags is non-zero, fails with "ENOSYS".
2002
2003 Please refer to pipe2(2) for more info on the $flags, but at the
2004 time of this writing, "IO::AIO::O_CLOEXEC", "IO::AIO::O_NONBLOCK"
2005 and "IO::AIO::O_DIRECT" (Linux 3.4, for packet-based pipes) were
2006 supported.
2007
2008 Example: create a pipe race-free w.r.t. threads and fork:
2009
2010 my ($rfh, $wfh) = IO::AIO::pipe2 IO::AIO::O_CLOEXEC
2011 or die "pipe2: $!\n";
2012
2013 $fh = IO::AIO::memfd_create $pathname[, $flags]
2014 This is a direct interface to the Linux memfd_create(2) system call.
2015 The (unhelpful) default for $flags is 0, but your default should be
2016 "IO::AIO::MFD_CLOEXEC".
2017
2018 On success, the new memfd filehandle is returned, otherwise returns
2019 "undef". If the memfd_create syscall is missing, fails with
2020 "ENOSYS".
2021
2022 Please refer to memfd_create(2) for more info on this call.
2023
2024 The following $flags values are available: "IO::AIO::MFD_CLOEXEC",
2025 "IO::AIO::MFD_ALLOW_SEALING", "IO::AIO::MFD_HUGETLB",
2026 "IO::AIO::MFD_HUGETLB_2MB" and "IO::AIO::MFD_HUGETLB_1GB".
2027
2028 Example: create a new memfd.
2029
2030 my $fh = IO::AIO::memfd_create "somenameforprocfd", IO::AIO::MFD_CLOEXEC
2031 or die "memfd_create: $!\n";
2032
2033 $fh = IO::AIO::pidfd_open $pid[, $flags]
2034 This is an interface to the Linux pidfd_open(2) system call. The
2035 default for $flags is 0.
2036
2037 On success, a new pidfd filehandle is returned (that is already set
2038 to close-on-exec), otherwise returns "undef". If the syscall is
2039 missing, fails with "ENOSYS".
2040
2041 Example: open pid 6341 as pidfd.
2042
2043 my $fh = IO::AIO::pidfd_open 6341
2044 or die "pidfd_open: $!\n";
2045
2046 $status = IO::AIO::pidfd_send_signal $pidfh, $signal[, $siginfo[,
2047 $flags]]
2048 This is an interface to the Linux pidfd_send_signal system call. The
2049 default for $siginfo is "undef" and the default for $flags is 0.
2050
2051 Returns the system call status. If the syscall is missing, fails
2052 with "ENOSYS".
2053
2054 When specified, $siginfo must be a reference to a hash with one or
2055 more of the following members:
2056
2057 code - the "si_code" member
2058 pid - the "si_pid" member
2059 uid - the "si_uid" member
2060 value_int - the "si_value.sival_int" member
2061 value_ptr - the "si_value.sival_ptr" member, specified as an integer
2062
2063 Example: send a SIGKILL to the specified process.
2064
2065 my $status = IO::AIO::pidfd_send_signal $pidfh, 9, undef
2066 and die "pidfd_send_signal: $!\n";
2067
2068 Example: send a SIGKILL to the specified process with extra data.
2069
2070 my $status = IO::AIO::pidfd_send_signal $pidfh, 9, { code => -1, value_int => 7 }
2071 and die "pidfd_send_signal: $!\n";
2072
2073 $fh = IO::AIO::pidfd_getfd $pidfh, $targetfd[, $flags]
2074 This is an interface to the Linux pidfd_getfd system call. The
2075 default for $flags is 0.
2076
2077 On success, returns a dup'ed copy of the target file descriptor
2078 (specified as an integer) returned (that is already set to
2079 close-on-exec), otherwise returns "undef". If the syscall is
2080 missing, fails with "ENOSYS".
2081
2082 Example: get a copy of standard error of another process and print
2083 soemthing to it.
2084
2085 my $errfh = IO::AIO::pidfd_getfd $pidfh, 2
2086 or die "pidfd_getfd: $!\n";
2087 print $errfh "stderr\n";
2088
2089 $fh = IO::AIO::eventfd [$initval, [$flags]]
2090 This is a direct interface to the Linux eventfd(2) system call. The
2091 (unhelpful) defaults for $initval and $flags are 0 for both.
2092
2093 On success, the new eventfd filehandle is returned, otherwise
2094 returns "undef". If the eventfd syscall is missing, fails with
2095 "ENOSYS".
2096
2097 Please refer to eventfd(2) for more info on this call.
2098
2099 The following symbol flag values are available:
2100 "IO::AIO::EFD_CLOEXEC", "IO::AIO::EFD_NONBLOCK" and
2101 "IO::AIO::EFD_SEMAPHORE" (Linux 2.6.30).
2102
2103 Example: create a new eventfd filehandle:
2104
2105 $fh = IO::AIO::eventfd 0, IO::AIO::EFD_CLOEXEC
2106 or die "eventfd: $!\n";
2107
2108 $fh = IO::AIO::timerfd_create $clockid[, $flags]
2109 This is a direct interface to the Linux timerfd_create(2) system
2110 call. The (unhelpful) default for $flags is 0, but your default
2111 should be "IO::AIO::TFD_CLOEXEC".
2112
2113 On success, the new timerfd filehandle is returned, otherwise
2114 returns "undef". If the timerfd_create syscall is missing, fails
2115 with "ENOSYS".
2116
2117 Please refer to timerfd_create(2) for more info on this call.
2118
2119 The following $clockid values are available:
2120 "IO::AIO::CLOCK_REALTIME", "IO::AIO::CLOCK_MONOTONIC"
2121 "IO::AIO::CLOCK_CLOCK_BOOTTIME" (Linux 3.15)
2122 "IO::AIO::CLOCK_CLOCK_REALTIME_ALARM" (Linux 3.11) and
2123 "IO::AIO::CLOCK_CLOCK_BOOTTIME_ALARM" (Linux 3.11).
2124
2125 The following $flags values are available (Linux 2.6.27):
2126 "IO::AIO::TFD_NONBLOCK" and "IO::AIO::TFD_CLOEXEC".
2127
2128 Example: create a new timerfd and set it to one-second repeated
2129 alarms, then wait for two alarms:
2130
2131 my $fh = IO::AIO::timerfd_create IO::AIO::CLOCK_BOOTTIME, IO::AIO::TFD_CLOEXEC
2132 or die "timerfd_create: $!\n";
2133
2134 defined IO::AIO::timerfd_settime $fh, 0, 1, 1
2135 or die "timerfd_settime: $!\n";
2136
2137 for (1..2) {
2138 8 == sysread $fh, my $buf, 8
2139 or die "timerfd read failure\n";
2140
2141 printf "number of expirations (likely 1): %d\n",
2142 unpack "Q", $buf;
2143 }
2144
2145 ($cur_interval, $cur_value) = IO::AIO::timerfd_settime $fh, $flags,
2146 $new_interval, $nbw_value
2147 This is a direct interface to the Linux timerfd_settime(2) system
2148 call. Please refer to its manpage for more info on this call.
2149
2150 The new itimerspec is specified using two (possibly fractional)
2151 second values, $new_interval and $new_value).
2152
2153 On success, the current interval and value are returned (as per
2154 "timerfd_gettime"). On failure, the empty list is returned.
2155
2156 The following $flags values are available:
2157 "IO::AIO::TFD_TIMER_ABSTIME" and "IO::AIO::TFD_TIMER_CANCEL_ON_SET".
2158
2159 See "IO::AIO::timerfd_create" for a full example.
2160
2161 ($cur_interval, $cur_value) = IO::AIO::timerfd_gettime $fh
2162 This is a direct interface to the Linux timerfd_gettime(2) system
2163 call. Please refer to its manpage for more info on this call.
2164
2165 On success, returns the current values of interval and value for the
2166 given timerfd (as potentially fractional second values). On failure,
2167 the empty list is returned.
2168
2169EVENT LOOP INTEGRATION
2170 It is recommended to use AnyEvent::AIO to integrate IO::AIO
2171 automatically into many event loops:
2172
2173 # AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
2174 use AnyEvent::AIO;
2175
2176 You can also integrate IO::AIO manually into many event loops, here are
2177 some examples of how to do this:
2178
2179 # EV integration
2180 my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
2181
2182 # Event integration
2183 Event->io (fd => IO::AIO::poll_fileno,
2184 poll => 'r',
2185 cb => \&IO::AIO::poll_cb);
2186
2187 # Glib/Gtk2 integration
2188 add_watch Glib::IO IO::AIO::poll_fileno,
2189 in => sub { IO::AIO::poll_cb; 1 };
2190
2191 # Tk integration
2192 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
2193 readable => \&IO::AIO::poll_cb);
2194
2195 # Danga::Socket integration
2196 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
2197 \&IO::AIO::poll_cb);
278 2198
279 FORK BEHAVIOUR 2199 FORK BEHAVIOUR
280 Before the fork IO::AIO enters a quiescent state where no requests can 2200 Usage of pthreads in a program changes the semantics of fork
281 be added in other threads and no results will be processed. After the 2201 considerably. Specifically, only async-safe functions can be called
282 fork the parent simply leaves the quiescent state and continues 2202 after fork. Perl doesn't know about this, so in general, you cannot call
283 request/result processing, while the child clears the request/result 2203 fork with defined behaviour in perl if pthreads are involved. IO::AIO
284 queue and starts the same number of threads as were in use by the 2204 uses pthreads, so this applies, but many other extensions and (for
285 parent. 2205 inexplicable reasons) perl itself often is linked against pthreads, so
2206 this limitation applies to quite a lot of perls.
2207
2208 This module no longer tries to fight your OS, or POSIX. That means
2209 IO::AIO only works in the process that loaded it. Forking is fully
2210 supported, but using IO::AIO in the child is not.
2211
2212 You might get around by not *using* IO::AIO before (or after) forking.
2213 You could also try to call the IO::AIO::reinit function in the child:
2214
2215 IO::AIO::reinit
2216 Abandons all current requests and I/O threads and simply
2217 reinitialises all data structures. This is not an operation
2218 supported by any standards, but happens to work on GNU/Linux and
2219 some newer BSD systems.
2220
2221 The only reasonable use for this function is to call it after
2222 forking, if "IO::AIO" was used in the parent. Calling it while
2223 IO::AIO is active in the process will result in undefined behaviour.
2224 Calling it at any time will also result in any undefined (by POSIX)
2225 behaviour.
2226
2227 LINUX-SPECIFIC CALLS
2228 When a call is documented as "linux-specific" then this means it
2229 originated on GNU/Linux. "IO::AIO" will usually try to autodetect the
2230 availability and compatibility of such calls regardless of the platform
2231 it is compiled on, so platforms such as FreeBSD which often implement
2232 these calls will work. When in doubt, call them and see if they fail wth
2233 "ENOSYS".
2234
2235 MEMORY USAGE
2236 Per-request usage:
2237
2238 Each aio request uses - depending on your architecture - around 100-200
2239 bytes of memory. In addition, stat requests need a stat buffer (possibly
2240 a few hundred bytes), readdir requires a result buffer and so on. Perl
2241 scalars and other data passed into aio requests will also be locked and
2242 will consume memory till the request has entered the done state.
2243
2244 This is not awfully much, so queuing lots of requests is not usually a
2245 problem.
2246
2247 Per-thread usage:
2248
2249 In the execution phase, some aio requests require more memory for
2250 temporary buffers, and each thread requires a stack and other data
2251 structures (usually around 16k-128k, depending on the OS).
2252
2253KNOWN BUGS
2254 Known bugs will be fixed in the next release :)
2255
2256KNOWN ISSUES
2257 Calls that try to "import" foreign memory areas (such as "IO::AIO::mmap"
2258 or "IO::AIO::aio_slurp") do not work with generic lvalues, such as
2259 non-created hash slots or other scalars I didn't think of. It's best to
2260 avoid such and either use scalar variables or making sure that the
2261 scalar exists (e.g. by storing "undef") and isn't "funny" (e.g. tied).
2262
2263 I am not sure anything can be done about this, so this is considered a
2264 known issue, rather than a bug.
286 2265
287SEE ALSO 2266SEE ALSO
288 Coro, Linux::AIO. 2267 AnyEvent::AIO for easy integration into event loops, Coro::AIO for a
2268 more natural syntax and IO::FDPass for file descriptor passing.
289 2269
290AUTHOR 2270AUTHOR
291 Marc Lehmann <schmorp@schmorp.de> 2271 Marc Lehmann <schmorp@schmorp.de>
292 http://home.schmorp.de/ 2272 http://home.schmorp.de/
293 2273

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