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Revision 1.62 by root, Sat Aug 25 19:59:18 2018 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 = shift 8 my $fh = shift
9 or die "/etc/passwd: $!"; 9 or die "/etc/passwd: $!";
10 ... 10 ...
11 }; 11 };
12 12
… …
24 $req->cancel; # cancel request if still in queue 24 $req->cancel; # cancel request if still in queue
25 25
26 my $grp = aio_group sub { print "all stats done\n" }; 26 my $grp = aio_group sub { print "all stats done\n" };
27 add $grp aio_stat "..." for ...; 27 add $grp aio_stat "..." for ...;
28 28
29 # AnyEvent integration (EV, Event, Glib, Tk, urxvt, pureperl...)
30 open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
31 my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
32
33 # EV integration
34 my $w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
35
36 # Event integration
37 Event->io (fd => IO::AIO::poll_fileno,
38 poll => 'r',
39 cb => \&IO::AIO::poll_cb);
40
41 # Glib/Gtk2 integration
42 add_watch Glib::IO IO::AIO::poll_fileno,
43 in => sub { IO::AIO::poll_cb; 1 };
44
45 # Tk integration
46 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
47 readable => \&IO::AIO::poll_cb);
48
49 # Danga::Socket integration
50 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
51 \&IO::AIO::poll_cb);
52
53DESCRIPTION 29DESCRIPTION
54 This module implements asynchronous I/O using whatever means your 30 This module implements asynchronous I/O using whatever means your
55 operating system supports. 31 operating system supports. It is implemented as an interface to "libeio"
32 (<http://software.schmorp.de/pkg/libeio.html>).
56 33
57 Asynchronous means that operations that can normally block your program 34 Asynchronous means that operations that can normally block your program
58 (e.g. reading from disk) will be done asynchronously: the operation will 35 (e.g. reading from disk) will be done asynchronously: the operation will
59 still block, but you can do something else in the meantime. This is 36 still block, but you can do something else in the meantime. This is
60 extremely useful for programs that need to stay interactive even when 37 extremely useful for programs that need to stay interactive even when
… …
65 operations concurrently. 42 operations concurrently.
66 43
67 While most of this works on all types of file descriptors (for example 44 While most of this works on all types of file descriptors (for example
68 sockets), using these functions on file descriptors that support 45 sockets), using these functions on file descriptors that support
69 nonblocking operation (again, sockets, pipes etc.) is very inefficient. 46 nonblocking operation (again, sockets, pipes etc.) is very inefficient.
70 Use an event loop for that (such as the Event module): IO::AIO will 47 Use an event loop for that (such as the EV module): IO::AIO will
71 naturally fit into such an event loop itself. 48 naturally fit into such an event loop itself.
72 49
73 In this version, a number of threads are started that execute your 50 In this version, a number of threads are started that execute your
74 requests and signal their completion. You don't need thread support in 51 requests and signal their completion. You don't need thread support in
75 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
… …
78 not well-supported or restricted (GNU/Linux doesn't allow them on normal 55 not well-supported or restricted (GNU/Linux doesn't allow them on normal
79 files currently, for example), and they would only support aio_read and 56 files currently, for example), and they would only support aio_read and
80 aio_write, so the remaining functionality would have to be implemented 57 aio_write, so the remaining functionality would have to be implemented
81 using threads anyway. 58 using threads anyway.
82 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
83 Although the module will work in the presence of other (Perl-) threads, 64 Although the module will work in the presence of other (Perl-) threads,
84 it is currently not reentrant in any way, so use appropriate locking 65 it is currently not reentrant in any way, so use appropriate locking
85 yourself, always call "poll_cb" from within the same thread, or never 66 yourself, always call "poll_cb" from within the same thread, or never
86 call "poll_cb" (or other "aio_" functions) recursively. 67 call "poll_cb" (or other "aio_" functions) recursively.
87 68
88 EXAMPLE 69 EXAMPLE
89 This is a simple example that uses the Event module and loads 70 This is a simple example that uses the EV module and loads /etc/passwd
90 /etc/passwd asynchronously: 71 asynchronously:
91 72
92 use Fcntl;
93 use Event; 73 use EV;
94 use IO::AIO; 74 use IO::AIO;
95 75
96 # register the IO::AIO callback with Event 76 # register the IO::AIO callback with EV
97 Event->io (fd => IO::AIO::poll_fileno, 77 my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
98 poll => 'r',
99 cb => \&IO::AIO::poll_cb);
100 78
101 # queue the request to open /etc/passwd 79 # queue the request to open /etc/passwd
102 aio_open "/etc/passwd", O_RDONLY, 0, sub { 80 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
103 my $fh = shift 81 my $fh = shift
104 or die "error while opening: $!"; 82 or die "error while opening: $!";
105 83
106 # stat'ing filehandles is generally non-blocking 84 # stat'ing filehandles is generally non-blocking
107 my $size = -s $fh; 85 my $size = -s $fh;
… …
116 94
117 # file contents now in $contents 95 # file contents now in $contents
118 print $contents; 96 print $contents;
119 97
120 # exit event loop and program 98 # exit event loop and program
121 Event::unloop; 99 EV::break;
122 }; 100 };
123 }; 101 };
124 102
125 # possibly queue up other requests, or open GUI windows, 103 # possibly queue up other requests, or open GUI windows,
126 # check for sockets etc. etc. 104 # check for sockets etc. etc.
127 105
128 # process events as long as there are some: 106 # process events as long as there are some:
129 Event::loop; 107 EV::run;
130 108
131REQUEST ANATOMY AND LIFETIME 109REQUEST ANATOMY AND LIFETIME
132 Every "aio_*" function creates a request. which is a C data structure 110 Every "aio_*" function creates a request. which is a C data structure
133 not directly visible to Perl. 111 not directly visible to Perl.
134 112
… …
170 anymore (except possibly for the Perl object, but its connection to 148 anymore (except possibly for the Perl object, but its connection to
171 the actual aio request is severed and calling its methods will 149 the actual aio request is severed and calling its methods will
172 either do nothing or result in a runtime error). 150 either do nothing or result in a runtime error).
173 151
174FUNCTIONS 152FUNCTIONS
175 AIO REQUEST 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 $nfd = IO::AIO::get_fdlimit [EXPERIMENTAL]
227 IO::AIO::min_fdlimit $nfd [EXPERIMENTAL]
228
229 IO::AIO::sendfile $ofh, $ifh, $offset, $count
230 IO::AIO::fadvise $fh, $offset, $len, $advice
231 IO::AIO::mmap $scalar, $length, $prot, $flags[, $fh[, $offset]]
232 IO::AIO::munmap $scalar
233 IO::AIO::mremap $scalar, $new_length, $flags[, $new_address]
234 IO::AIO::madvise $scalar, $offset, $length, $advice
235 IO::AIO::mprotect $scalar, $offset, $length, $protect
236 IO::AIO::munlock $scalar, $offset = 0, $length = undef
237 IO::AIO::munlockall
238
239 API NOTES
176 All the "aio_*" calls are more or less thin wrappers around the syscall 240 All the "aio_*" calls are more or less thin wrappers around the syscall
177 with the same name (sans "aio_"). The arguments are similar or 241 with the same name (sans "aio_"). The arguments are similar or
178 identical, and they all accept an additional (and optional) $callback 242 identical, and they all accept an additional (and optional) $callback
179 argument which must be a code reference. This code reference will get 243 argument which must be a code reference. This code reference will be
180 called with the syscall return code (e.g. most syscalls return -1 on 244 called after the syscall has been executed in an asynchronous fashion.
181 error, unlike perl, which usually delivers "false") as it's sole 245 The results of the request will be passed as arguments to the callback
182 argument when the given syscall has been executed asynchronously. 246 (and, if an error occured, in $!) - for most requests the syscall return
247 code (e.g. most syscalls return -1 on error, unlike perl, which usually
248 delivers "false").
249
250 Some requests (such as "aio_readdir") pass the actual results and
251 communicate failures by passing "undef".
183 252
184 All functions expecting a filehandle keep a copy of the filehandle 253 All functions expecting a filehandle keep a copy of the filehandle
185 internally until the request has finished. 254 internally until the request has finished.
186 255
187 All functions return request objects of type IO::AIO::REQ that allow 256 All functions return request objects of type IO::AIO::REQ that allow
188 further manipulation of those requests while they are in-flight. 257 further manipulation of those requests while they are in-flight.
189 258
190 The pathnames you pass to these routines *must* be absolute and encoded 259 The pathnames you pass to these routines *should* be absolute. The
191 as octets. The reason for the former is that at the time the request is 260 reason for this is that at the time the request is being executed, the
192 being executed, the current working directory could have changed. 261 current working directory could have changed. Alternatively, you can
193 Alternatively, you can make sure that you never change the current 262 make sure that you never change the current working directory anywhere
194 working directory anywhere in the program and then use relative paths. 263 in the program and then use relative paths. You can also take advantage
264 of IO::AIOs working directory abstraction, that lets you specify paths
265 relative to some previously-opened "working directory object" - see the
266 description of the "IO::AIO::WD" class later in this document.
195 267
196 To encode pathnames as octets, either make sure you either: a) always 268 To encode pathnames as octets, either make sure you either: a) always
197 pass in filenames you got from outside (command line, readdir etc.) 269 pass in filenames you got from outside (command line, readdir etc.)
198 without tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module 270 without tinkering, b) are in your native filesystem encoding, c) use the
199 and encode your pathnames to the locale (or other) encoding in effect in 271 Encode module and encode your pathnames to the locale (or other)
200 the user environment, d) use Glib::filename_from_unicode on unicode 272 encoding in effect in the user environment, d) use
201 filenames or e) use something else to ensure your scalar has the correct 273 Glib::filename_from_unicode on unicode filenames or e) use something
202 contents. 274 else to ensure your scalar has the correct contents.
203 275
204 This works, btw. independent of the internal UTF-8 bit, which IO::AIO 276 This works, btw. independent of the internal UTF-8 bit, which IO::AIO
205 handles correctly wether it is set or not. 277 handles correctly whether it is set or not.
206 278
279 AIO REQUEST FUNCTIONS
207 $prev_pri = aioreq_pri [$pri] 280 $prev_pri = aioreq_pri [$pri]
208 Returns the priority value that would be used for the next request 281 Returns the priority value that would be used for the next request
209 and, if $pri is given, sets the priority for the next aio request. 282 and, if $pri is given, sets the priority for the next aio request.
210 283
211 The default priority is 0, the minimum and maximum priorities are -4 284 The default priority is 0, the minimum and maximum priorities are -4
… …
233 Similar to "aioreq_pri", but subtracts the given value from the 306 Similar to "aioreq_pri", but subtracts the given value from the
234 current priority, so the effect is cumulative. 307 current priority, so the effect is cumulative.
235 308
236 aio_open $pathname, $flags, $mode, $callback->($fh) 309 aio_open $pathname, $flags, $mode, $callback->($fh)
237 Asynchronously open or create a file and call the callback with a 310 Asynchronously open or create a file and call the callback with a
238 newly created filehandle for the file. 311 newly created filehandle for the file (or "undef" in case of an
312 error).
239 313
240 The pathname passed to "aio_open" must be absolute. See API NOTES, 314 The pathname passed to "aio_open" must be absolute. See API NOTES,
241 above, for an explanation. 315 above, for an explanation.
242 316
243 The $flags argument is a bitmask. See the "Fcntl" module for a list. 317 The $flags argument is a bitmask. See the "Fcntl" module for a list.
… …
250 will be modified by the umask in effect then the request is being 324 will be modified by the umask in effect then the request is being
251 executed, so better never change the umask. 325 executed, so better never change the umask.
252 326
253 Example: 327 Example:
254 328
255 aio_open "/etc/passwd", O_RDONLY, 0, sub { 329 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
256 if ($_[0]) { 330 if ($_[0]) {
257 print "open successful, fh is $_[0]\n"; 331 print "open successful, fh is $_[0]\n";
258 ... 332 ...
259 } else { 333 } else {
260 die "open failed: $!\n"; 334 die "open failed: $!\n";
261 } 335 }
262 }; 336 };
263 337
338 In addition to all the common open modes/flags ("O_RDONLY",
339 "O_WRONLY", "O_RDWR", "O_CREAT", "O_TRUNC", "O_EXCL" and
340 "O_APPEND"), the following POSIX and non-POSIX constants are
341 available (missing ones on your system are, as usual, 0):
342
343 "O_ASYNC", "O_DIRECT", "O_NOATIME", "O_CLOEXEC", "O_NOCTTY",
344 "O_NOFOLLOW", "O_NONBLOCK", "O_EXEC", "O_SEARCH", "O_DIRECTORY",
345 "O_DSYNC", "O_RSYNC", "O_SYNC", "O_PATH", "O_TMPFILE", "O_TTY_INIT"
346 and "O_ACCMODE".
347
264 aio_close $fh, $callback->($status) 348 aio_close $fh, $callback->($status)
265 Asynchronously close a file and call the callback with the result 349 Asynchronously close a file and call the callback with the result
266 code. 350 code.
267 351
268 Unfortunately, you can't do this to perl. Perl *insists* very 352 Unfortunately, you can't do this to perl. Perl *insists* very
269 strongly on closing the file descriptor associated with the 353 strongly on closing the file descriptor associated with the
270 filehandle itself. Here is what aio_close will try: 354 filehandle itself.
271 355
272 1. dup()licate the fd 356 Therefore, "aio_close" will not close the filehandle - instead it
273 2. asynchronously close() the duplicated fd 357 will use dup2 to overwrite the file descriptor with the write-end of
274 3. dup()licate the fd once more 358 a pipe (the pipe fd will be created on demand and will be cached).
275 4. let perl close() the filehandle
276 5. asynchronously close the duplicated fd
277 359
278 The idea is that the first close() flushes stuff to disk that 360 Or in other words: the file descriptor will be closed, but it will
279 closing an fd will flush, so when perl closes the fd, nothing much 361 not be free for reuse until the perl filehandle is closed.
280 will need to be flushed. The second async. close() will then flush
281 stuff to disk that closing the last fd to the file will flush.
282 362
283 Just FYI, SuSv3 has this to say on close: 363 aio_seek $fh, $offset, $whence, $callback->($offs)
364 Seeks the filehandle to the new $offset, similarly to perl's
365 "sysseek". The $whence can use the traditional values (0 for
366 "IO::AIO::SEEK_SET", 1 for "IO::AIO::SEEK_CUR" or 2 for
367 "IO::AIO::SEEK_END").
284 368
285 All outstanding record locks owned by the process on the file 369 The resulting absolute offset will be passed to the callback, or -1
286 associated with the file descriptor shall be removed. 370 in case of an error.
287 371
288 If fildes refers to a socket, close() shall cause the socket to be 372 In theory, the $whence constants could be different than the
289 destroyed. ... close() shall block for up to the current linger 373 corresponding values from Fcntl, but perl guarantees they are the
290 interval until all data is transmitted. 374 same, so don't panic.
291 [this actually sounds like a specification bug, but who knows]
292 375
293 And at least Linux additionally actually flushes stuff on every 376 As a GNU/Linux (and maybe Solaris) extension, also the constants
294 close, even when the file itself is still open. 377 "IO::AIO::SEEK_DATA" and "IO::AIO::SEEK_HOLE" are available, if they
295 378 could be found. No guarantees about suitability for use in
296 Sounds enourmously inefficient and complicated? Yes... please show 379 "aio_seek" or Perl's "sysseek" can be made though, although I would
297 me how to nuke perl's fd out of existence... 380 naively assume they "just work".
298 381
299 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval) 382 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
300 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval) 383 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
301 Reads or writes $length bytes from the specified $fh and $offset 384 Reads or writes $length bytes from or to the specified $fh and
302 into the scalar given by $data and offset $dataoffset and calls the 385 $offset into the scalar given by $data and offset $dataoffset and
303 callback without the actual number of bytes read (or -1 on error, 386 calls the callback with the actual number of bytes transferred (or
304 just like the syscall). 387 -1 on error, just like the syscall).
388
389 "aio_read" will, like "sysread", shrink or grow the $data scalar to
390 offset plus the actual number of bytes read.
305 391
306 If $offset is undefined, then the current file descriptor offset 392 If $offset is undefined, then the current file descriptor offset
307 will be used (and updated), otherwise the file descriptor offset 393 will be used (and updated), otherwise the file descriptor offset
308 will not be changed by these calls. 394 will not be changed by these calls.
309 395
… …
328 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval) 414 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
329 Tries to copy $length bytes from $in_fh to $out_fh. It starts 415 Tries to copy $length bytes from $in_fh to $out_fh. It starts
330 reading at byte offset $in_offset, and starts writing at the current 416 reading at byte offset $in_offset, and starts writing at the current
331 file offset of $out_fh. Because of that, it is not safe to issue 417 file offset of $out_fh. Because of that, it is not safe to issue
332 more than one "aio_sendfile" per $out_fh, as they will interfere 418 more than one "aio_sendfile" per $out_fh, as they will interfere
333 with each other. 419 with each other. The same $in_fh works fine though, as this function
420 does not move or use the file offset of $in_fh.
334 421
422 Please note that "aio_sendfile" can read more bytes from $in_fh than
423 are written, and there is no way to find out how many more bytes
424 have been read from "aio_sendfile" alone, as "aio_sendfile" only
425 provides the number of bytes written to $out_fh. Only if the result
426 value equals $length one can assume that $length bytes have been
427 read.
428
429 Unlike with other "aio_" functions, it makes a lot of sense to use
430 "aio_sendfile" on non-blocking sockets, as long as one end
431 (typically the $in_fh) is a file - the file I/O will then be
432 asynchronous, while the socket I/O will be non-blocking. Note,
433 however, that you can run into a trap where "aio_sendfile" reads
434 some data with readahead, then fails to write all data, and when the
435 socket is ready the next time, the data in the cache is already
436 lost, forcing "aio_sendfile" to again hit the disk. Explicit
437 "aio_read" + "aio_write" let's you better control resource usage.
438
335 This call tries to make use of a native "sendfile" syscall to 439 This call tries to make use of a native "sendfile"-like syscall to
336 provide zero-copy operation. For this to work, $out_fh should refer 440 provide zero-copy operation. For this to work, $out_fh should refer
337 to a socket, and $in_fh should refer to mmap'able file. 441 to a socket, and $in_fh should refer to an mmap'able file.
338 442
339 If the native sendfile call fails or is not implemented, it will be 443 If a native sendfile cannot be found or it fails with "ENOSYS",
340 emulated, so you can call "aio_sendfile" on any type of filehandle 444 "EINVAL", "ENOTSUP", "EOPNOTSUPP", "EAFNOSUPPORT", "EPROTOTYPE" or
341 regardless of the limitations of the operating system. 445 "ENOTSOCK", it will be emulated, so you can call "aio_sendfile" on
446 any type of filehandle regardless of the limitations of the
447 operating system.
342 448
343 Please note, however, that "aio_sendfile" can read more bytes from 449 As native sendfile syscalls (as practically any non-POSIX interface
344 $in_fh than are written, and there is no way to find out how many 450 hacked together in a hurry to improve benchmark numbers) tend to be
345 bytes have been read from "aio_sendfile" alone, as "aio_sendfile" 451 rather buggy on many systems, this implementation tries to work
346 only provides the number of bytes written to $out_fh. Only if the 452 around some known bugs in Linux and FreeBSD kernels (probably
347 result value equals $length one can assume that $length bytes have 453 others, too), but that might fail, so you really really should check
348 been read. 454 the return value of "aio_sendfile" - fewer bytes than expected might
455 have been transferred.
349 456
350 aio_readahead $fh,$offset,$length, $callback->($retval) 457 aio_readahead $fh,$offset,$length, $callback->($retval)
351 "aio_readahead" populates the page cache with data from a file so 458 "aio_readahead" populates the page cache with data from a file so
352 that subsequent reads from that file will not block on disk I/O. The 459 that subsequent reads from that file will not block on disk I/O. The
353 $offset argument specifies the starting point from which data is to 460 $offset argument specifies the starting point from which data is to
… …
356 to a page boundary and bytes are read up to the next page boundary 463 to a page boundary and bytes are read up to the next page boundary
357 greater than or equal to (off-set+length). "aio_readahead" does not 464 greater than or equal to (off-set+length). "aio_readahead" does not
358 read beyond the end of the file. The current file offset of the file 465 read beyond the end of the file. The current file offset of the file
359 is left unchanged. 466 is left unchanged.
360 467
361 If that syscall doesn't exist (likely if your OS isn't Linux) it 468 If that syscall doesn't exist (likely if your kernel isn't Linux) it
362 will be emulated by simply reading the data, which would have a 469 will be emulated by simply reading the data, which would have a
363 similar effect. 470 similar effect.
364 471
365 aio_stat $fh_or_path, $callback->($status) 472 aio_stat $fh_or_path, $callback->($status)
366 aio_lstat $fh, $callback->($status) 473 aio_lstat $fh, $callback->($status)
367 Works like perl's "stat" or "lstat" in void context. The callback 474 Works almost exactly like perl's "stat" or "lstat" in void context.
368 will be called after the stat and the results will be available 475 The callback will be called after the stat and the results will be
369 using "stat _" or "-s _" etc... 476 available using "stat _" or "-s _" and other tests (with the
477 exception of "-B" and "-T").
370 478
371 The pathname passed to "aio_stat" must be absolute. See API NOTES, 479 The pathname passed to "aio_stat" must be absolute. See API NOTES,
372 above, for an explanation. 480 above, for an explanation.
373 481
374 Currently, the stats are always 64-bit-stats, i.e. instead of 482 Currently, the stats are always 64-bit-stats, i.e. instead of
375 returning an error when stat'ing a large file, the results will be 483 returning an error when stat'ing a large file, the results will be
376 silently truncated unless perl itself is compiled with large file 484 silently truncated unless perl itself is compiled with large file
377 support. 485 support.
378 486
487 To help interpret the mode and dev/rdev stat values, IO::AIO offers
488 the following constants and functions (if not implemented, the
489 constants will be 0 and the functions will either "croak" or fall
490 back on traditional behaviour).
491
492 "S_IFMT", "S_IFIFO", "S_IFCHR", "S_IFBLK", "S_IFLNK", "S_IFREG",
493 "S_IFDIR", "S_IFWHT", "S_IFSOCK", "IO::AIO::major $dev_t",
494 "IO::AIO::minor $dev_t", "IO::AIO::makedev $major, $minor".
495
496 To access higher resolution stat timestamps, see "SUBSECOND STAT
497 TIME ACCESS".
498
379 Example: Print the length of /etc/passwd: 499 Example: Print the length of /etc/passwd:
380 500
381 aio_stat "/etc/passwd", sub { 501 aio_stat "/etc/passwd", sub {
382 $_[0] and die "stat failed: $!"; 502 $_[0] and die "stat failed: $!";
383 print "size is ", -s _, "\n"; 503 print "size is ", -s _, "\n";
384 }; 504 };
385 505
506 aio_statvfs $fh_or_path, $callback->($statvfs)
507 Works like the POSIX "statvfs" or "fstatvfs" syscalls, depending on
508 whether a file handle or path was passed.
509
510 On success, the callback is passed a hash reference with the
511 following members: "bsize", "frsize", "blocks", "bfree", "bavail",
512 "files", "ffree", "favail", "fsid", "flag" and "namemax". On
513 failure, "undef" is passed.
514
515 The following POSIX IO::AIO::ST_* constants are defined: "ST_RDONLY"
516 and "ST_NOSUID".
517
518 The following non-POSIX IO::AIO::ST_* flag masks are defined to
519 their correct value when available, or to 0 on systems that do not
520 support them: "ST_NODEV", "ST_NOEXEC", "ST_SYNCHRONOUS",
521 "ST_MANDLOCK", "ST_WRITE", "ST_APPEND", "ST_IMMUTABLE",
522 "ST_NOATIME", "ST_NODIRATIME" and "ST_RELATIME".
523
524 Example: stat "/wd" and dump out the data if successful.
525
526 aio_statvfs "/wd", sub {
527 my $f = $_[0]
528 or die "statvfs: $!";
529
530 use Data::Dumper;
531 say Dumper $f;
532 };
533
534 # result:
535 {
536 bsize => 1024,
537 bfree => 4333064312,
538 blocks => 10253828096,
539 files => 2050765568,
540 flag => 4096,
541 favail => 2042092649,
542 bavail => 4333064312,
543 ffree => 2042092649,
544 namemax => 255,
545 frsize => 1024,
546 fsid => 1810
547 }
548
386 aio_utime $fh_or_path, $atime, $mtime, $callback->($status) 549 aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
387 Works like perl's "utime" function (including the special case of 550 Works like perl's "utime" function (including the special case of
388 $atime and $mtime being undef). Fractional times are supported if 551 $atime and $mtime being undef). Fractional times are supported if
389 the underlying syscalls support them. 552 the underlying syscalls support them.
390 553
391 When called with a pathname, uses utimes(2) if available, otherwise 554 When called with a pathname, uses utimensat(2) or utimes(2) if
392 utime(2). If called on a file descriptor, uses futimes(2) if 555 available, otherwise utime(2). If called on a file descriptor, uses
393 available, otherwise returns ENOSYS, so this is not portable. 556 futimens(2) or futimes(2) if available, otherwise returns ENOSYS, so
557 this is not portable.
394 558
395 Examples: 559 Examples:
396 560
397 # set atime and mtime to current time (basically touch(1)): 561 # set atime and mtime to current time (basically touch(1)):
398 aio_utime "path", undef, undef; 562 aio_utime "path", undef, undef;
… …
412 aio_chown "path", 0, undef; 576 aio_chown "path", 0, undef;
413 577
414 aio_truncate $fh_or_path, $offset, $callback->($status) 578 aio_truncate $fh_or_path, $offset, $callback->($status)
415 Works like truncate(2) or ftruncate(2). 579 Works like truncate(2) or ftruncate(2).
416 580
581 aio_allocate $fh, $mode, $offset, $len, $callback->($status)
582 Allocates or frees disk space according to the $mode argument. See
583 the linux "fallocate" documentation for details.
584
585 $mode is usually 0 or "IO::AIO::FALLOC_FL_KEEP_SIZE" to allocate
586 space, or "IO::AIO::FALLOC_FL_PUNCH_HOLE |
587 IO::AIO::FALLOC_FL_KEEP_SIZE", to deallocate a file range.
588
589 IO::AIO also supports "FALLOC_FL_COLLAPSE_RANGE", to remove a range
590 (without leaving a hole), "FALLOC_FL_ZERO_RANGE", to zero a range,
591 "FALLOC_FL_INSERT_RANGE" to insert a range and
592 "FALLOC_FL_UNSHARE_RANGE" to unshare shared blocks (see your
593 fallocate(2) manpage).
594
595 The file system block size used by "fallocate" is presumably the
596 "f_bsize" returned by "statvfs", but different filesystems and
597 filetypes can dictate other limitations.
598
599 If "fallocate" isn't available or cannot be emulated (currently no
600 emulation will be attempted), passes -1 and sets $! to "ENOSYS".
601
417 aio_chmod $fh_or_path, $mode, $callback->($status) 602 aio_chmod $fh_or_path, $mode, $callback->($status)
418 Works like perl's "chmod" function. 603 Works like perl's "chmod" function.
419 604
420 aio_unlink $pathname, $callback->($status) 605 aio_unlink $pathname, $callback->($status)
421 Asynchronously unlink (delete) a file and call the callback with the 606 Asynchronously unlink (delete) a file and call the callback with the
422 result code. 607 result code.
423 608
424 aio_mknod $path, $mode, $dev, $callback->($status) 609 aio_mknod $pathname, $mode, $dev, $callback->($status)
425 [EXPERIMENTAL] 610 [EXPERIMENTAL]
426 611
427 Asynchronously create a device node (or fifo). See mknod(2). 612 Asynchronously create a device node (or fifo). See mknod(2).
428 613
429 The only (POSIX-) portable way of calling this function is: 614 The only (POSIX-) portable way of calling this function is:
430 615
431 aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ... 616 aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
617
618 See "aio_stat" for info about some potentially helpful extra
619 constants and functions.
432 620
433 aio_link $srcpath, $dstpath, $callback->($status) 621 aio_link $srcpath, $dstpath, $callback->($status)
434 Asynchronously create a new link to the existing object at $srcpath 622 Asynchronously create a new link to the existing object at $srcpath
435 at the path $dstpath and call the callback with the result code. 623 at the path $dstpath and call the callback with the result code.
436 624
437 aio_symlink $srcpath, $dstpath, $callback->($status) 625 aio_symlink $srcpath, $dstpath, $callback->($status)
438 Asynchronously create a new symbolic link to the existing object at 626 Asynchronously create a new symbolic link to the existing object at
439 $srcpath at the path $dstpath and call the callback with the result 627 $srcpath at the path $dstpath and call the callback with the result
440 code. 628 code.
441 629
442 aio_readlink $path, $callback->($link) 630 aio_readlink $pathname, $callback->($link)
443 Asynchronously read the symlink specified by $path and pass it to 631 Asynchronously read the symlink specified by $path and pass it to
444 the callback. If an error occurs, nothing or undef gets passed to 632 the callback. If an error occurs, nothing or undef gets passed to
445 the callback. 633 the callback.
446 634
635 aio_realpath $pathname, $callback->($path)
636 Asynchronously make the path absolute and resolve any symlinks in
637 $path. The resulting path only consists of directories (same as
638 Cwd::realpath).
639
640 This request can be used to get the absolute path of the current
641 working directory by passing it a path of . (a single dot).
642
447 aio_rename $srcpath, $dstpath, $callback->($status) 643 aio_rename $srcpath, $dstpath, $callback->($status)
448 Asynchronously rename the object at $srcpath to $dstpath, just as 644 Asynchronously rename the object at $srcpath to $dstpath, just as
449 rename(2) and call the callback with the result code. 645 rename(2) and call the callback with the result code.
646
647 On systems that support the AIO::WD working directory abstraction
648 natively, the case "[$wd, "."]" as $srcpath is specialcased -
649 instead of failing, "rename" is called on the absolute path of $wd.
650
651 aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
652 Basically a version of "aio_rename" with an additional $flags
653 argument. Calling this with "$flags=0" is the same as calling
654 "aio_rename".
655
656 Non-zero flags are currently only supported on GNU/Linux systems
657 that support renameat2. Other systems fail with "ENOSYS" in this
658 case.
659
660 The following constants are available (missing ones are, as usual
661 0), see renameat2(2) for details:
662
663 "IO::AIO::RENAME_NOREPLACE", "IO::AIO::RENAME_EXCHANGE" and
664 "IO::AIO::RENAME_WHITEOUT".
450 665
451 aio_mkdir $pathname, $mode, $callback->($status) 666 aio_mkdir $pathname, $mode, $callback->($status)
452 Asynchronously mkdir (create) a directory and call the callback with 667 Asynchronously mkdir (create) a directory and call the callback with
453 the result code. $mode will be modified by the umask at the time the 668 the result code. $mode will be modified by the umask at the time the
454 request is executed, so do not change your umask. 669 request is executed, so do not change your umask.
455 670
456 aio_rmdir $pathname, $callback->($status) 671 aio_rmdir $pathname, $callback->($status)
457 Asynchronously rmdir (delete) a directory and call the callback with 672 Asynchronously rmdir (delete) a directory and call the callback with
458 the result code. 673 the result code.
459 674
675 On systems that support the AIO::WD working directory abstraction
676 natively, the case "[$wd, "."]" is specialcased - instead of
677 failing, "rmdir" is called on the absolute path of $wd.
678
460 aio_readdir $pathname, $callback->($entries) 679 aio_readdir $pathname, $callback->($entries)
461 Unlike the POSIX call of the same name, "aio_readdir" reads an 680 Unlike the POSIX call of the same name, "aio_readdir" reads an
462 entire directory (i.e. opendir + readdir + closedir). The entries 681 entire directory (i.e. opendir + readdir + closedir). The entries
463 will not be sorted, and will NOT include the "." and ".." entries. 682 will not be sorted, and will NOT include the "." and ".." entries.
464 683
465 The callback a single argument which is either "undef" or an 684 The callback is passed a single argument which is either "undef" or
466 array-ref with the filenames. 685 an array-ref with the filenames.
467 686
687 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
688 Quite similar to "aio_readdir", but the $flags argument allows one
689 to tune behaviour and output format. In case of an error, $entries
690 will be "undef".
691
692 The flags are a combination of the following constants, ORed
693 together (the flags will also be passed to the callback, possibly
694 modified):
695
696 IO::AIO::READDIR_DENTS
697 Normally the callback gets an arrayref consisting of names only
698 (as with "aio_readdir"). If this flag is set, then the callback
699 gets an arrayref with "[$name, $type, $inode]" arrayrefs, each
700 describing a single directory entry in more detail:
701
702 $name is the name of the entry.
703
704 $type is one of the "IO::AIO::DT_xxx" constants:
705
706 "IO::AIO::DT_UNKNOWN", "IO::AIO::DT_FIFO", "IO::AIO::DT_CHR",
707 "IO::AIO::DT_DIR", "IO::AIO::DT_BLK", "IO::AIO::DT_REG",
708 "IO::AIO::DT_LNK", "IO::AIO::DT_SOCK", "IO::AIO::DT_WHT".
709
710 "IO::AIO::DT_UNKNOWN" means just that: readdir does not know. If
711 you need to know, you have to run stat yourself. Also, for
712 speed/memory reasons, the $type scalars are read-only: you must
713 not modify them.
714
715 $inode is the inode number (which might not be exact on systems
716 with 64 bit inode numbers and 32 bit perls). This field has
717 unspecified content on systems that do not deliver the inode
718 information.
719
720 IO::AIO::READDIR_DIRS_FIRST
721 When this flag is set, then the names will be returned in an
722 order where likely directories come first, in optimal stat
723 order. This is useful when you need to quickly find directories,
724 or you want to find all directories while avoiding to stat()
725 each entry.
726
727 If the system returns type information in readdir, then this is
728 used to find directories directly. Otherwise, likely directories
729 are names beginning with ".", or otherwise names with no dots,
730 of which names with short names are tried first.
731
732 IO::AIO::READDIR_STAT_ORDER
733 When this flag is set, then the names will be returned in an
734 order suitable for stat()'ing each one. That is, when you plan
735 to stat() most or all files in the given directory, then the
736 returned order will likely be faster.
737
738 If both this flag and "IO::AIO::READDIR_DIRS_FIRST" are
739 specified, then the likely dirs come first, resulting in a less
740 optimal stat order for stat'ing all entries, but likely a more
741 optimal order for finding subdirectories.
742
743 IO::AIO::READDIR_FOUND_UNKNOWN
744 This flag should not be set when calling "aio_readdirx".
745 Instead, it is being set by "aio_readdirx", when any of the
746 $type's found were "IO::AIO::DT_UNKNOWN". The absence of this
747 flag therefore indicates that all $type's are known, which can
748 be used to speed up some algorithms.
749
750 aio_slurp $pathname, $offset, $length, $data, $callback->($status)
751 Opens, reads and closes the given file. The data is put into $data,
752 which is resized as required.
753
754 If $offset is negative, then it is counted from the end of the file.
755
756 If $length is zero, then the remaining length of the file is used.
757 Also, in this case, the same limitations to modifying $data apply as
758 when IO::AIO::mmap is used, i.e. it must only be modified in-place
759 with "substr". If the size of the file is known, specifying a
760 non-zero $length results in a performance advantage.
761
762 This request is similar to the older "aio_load" request, but since
763 it is a single request, it might be more efficient to use.
764
765 Example: load /etc/passwd into $passwd.
766
767 my $passwd;
768 aio_slurp "/etc/passwd", 0, 0, $passwd, sub {
769 $_[0] >= 0
770 or die "/etc/passwd: $!\n";
771
772 printf "/etc/passwd is %d bytes long, and contains:\n", length $passwd;
773 print $passwd;
774 };
775 IO::AIO::flush;
776
468 aio_load $path, $data, $callback->($status) 777 aio_load $pathname, $data, $callback->($status)
469 This is a composite request that tries to fully load the given file 778 This is a composite request that tries to fully load the given file
470 into memory. Status is the same as with aio_read. 779 into memory. Status is the same as with aio_read.
780
781 Using "aio_slurp" might be more efficient, as it is a single
782 request.
471 783
472 aio_copy $srcpath, $dstpath, $callback->($status) 784 aio_copy $srcpath, $dstpath, $callback->($status)
473 Try to copy the *file* (directories not supported as either source 785 Try to copy the *file* (directories not supported as either source
474 or destination) from $srcpath to $dstpath and call the callback with 786 or destination) from $srcpath to $dstpath and call the callback with
475 the 0 (error) or -1 ok. 787 a status of 0 (ok) or -1 (error, see $!).
476 788
789 Existing destination files will be truncated.
790
477 This is a composite request that it creates the destination file 791 This is a composite request that creates the destination file with
478 with mode 0200 and copies the contents of the source file into it 792 mode 0200 and copies the contents of the source file into it using
479 using "aio_sendfile", followed by restoring atime, mtime, access 793 "aio_sendfile", followed by restoring atime, mtime, access mode and
480 mode and uid/gid, in that order. 794 uid/gid, in that order.
481 795
482 If an error occurs, the partial destination file will be unlinked, 796 If an error occurs, the partial destination file will be unlinked,
483 if possible, except when setting atime, mtime, access mode and 797 if possible, except when setting atime, mtime, access mode and
484 uid/gid, where errors are being ignored. 798 uid/gid, where errors are being ignored.
485 799
486 aio_move $srcpath, $dstpath, $callback->($status) 800 aio_move $srcpath, $dstpath, $callback->($status)
487 Try to move the *file* (directories not supported as either source 801 Try to move the *file* (directories not supported as either source
488 or destination) from $srcpath to $dstpath and call the callback with 802 or destination) from $srcpath to $dstpath and call the callback with
489 the 0 (error) or -1 ok. 803 a status of 0 (ok) or -1 (error, see $!).
490 804
491 This is a composite request that tries to rename(2) the file first. 805 This is a composite request that tries to rename(2) the file first;
492 If rename files with "EXDEV", it copies the file with "aio_copy" 806 if rename fails with "EXDEV", it copies the file with "aio_copy"
493 and, if that is successful, unlinking the $srcpath. 807 and, if that is successful, unlinks the $srcpath.
494 808
495 aio_scandir $path, $maxreq, $callback->($dirs, $nondirs) 809 aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
496 Scans a directory (similar to "aio_readdir") but additionally tries 810 Scans a directory (similar to "aio_readdir") but additionally tries
497 to efficiently separate the entries of directory $path into two sets 811 to efficiently separate the entries of directory $path into two sets
498 of names, directories you can recurse into (directories), and ones 812 of names, directories you can recurse into (directories), and ones
499 you cannot recurse into (everything else, including symlinks to 813 you cannot recurse into (everything else, including symlinks to
500 directories). 814 directories).
501 815
502 "aio_scandir" is a composite request that creates of many sub 816 "aio_scandir" is a composite request that generates many sub
503 requests_ $maxreq specifies the maximum number of outstanding aio 817 requests. $maxreq specifies the maximum number of outstanding aio
504 requests that this function generates. If it is "<= 0", then a 818 requests that this function generates. If it is "<= 0", then a
505 suitable default will be chosen (currently 4). 819 suitable default will be chosen (currently 4).
506 820
507 On error, the callback is called without arguments, otherwise it 821 On error, the callback is called without arguments, otherwise it
508 receives two array-refs with path-relative entry names. 822 receives two array-refs with path-relative entry names.
… …
518 Implementation notes. 832 Implementation notes.
519 833
520 The "aio_readdir" cannot be avoided, but "stat()"'ing every entry 834 The "aio_readdir" cannot be avoided, but "stat()"'ing every entry
521 can. 835 can.
522 836
837 If readdir returns file type information, then this is used directly
838 to find directories.
839
523 After reading the directory, the modification time, size etc. of the 840 Otherwise, after reading the directory, the modification time, size
524 directory before and after the readdir is checked, and if they match 841 etc. of the directory before and after the readdir is checked, and
525 (and isn't the current time), the link count will be used to decide 842 if they match (and isn't the current time), the link count will be
526 how many entries are directories (if >= 2). Otherwise, no knowledge 843 used to decide how many entries are directories (if >= 2).
527 of the number of subdirectories will be assumed. 844 Otherwise, no knowledge of the number of subdirectories will be
845 assumed.
528 846
529 Then entries will be sorted into likely directories (everything 847 Then entries will be sorted into likely directories a non-initial
530 without a non-initial dot currently) and likely non-directories 848 dot currently) and likely non-directories (see "aio_readdirx"). Then
531 (everything else). Then every entry plus an appended "/." will be 849 every entry plus an appended "/." will be "stat"'ed, likely
532 "stat"'ed, likely directories first. If that succeeds, it assumes 850 directories first, in order of their inode numbers. If that
533 that the entry is a directory or a symlink to directory (which will 851 succeeds, it assumes that the entry is a directory or a symlink to
534 be checked seperately). This is often faster than stat'ing the entry 852 directory (which will be checked separately). This is often faster
535 itself because filesystems might detect the type of the entry 853 than stat'ing the entry itself because filesystems might detect the
536 without reading the inode data (e.g. ext2fs filetype feature). 854 type of the entry without reading the inode data (e.g. ext2fs
855 filetype feature), even on systems that cannot return the filetype
856 information on readdir.
537 857
538 If the known number of directories (link count - 2) has been 858 If the known number of directories (link count - 2) has been
539 reached, the rest of the entries is assumed to be non-directories. 859 reached, the rest of the entries is assumed to be non-directories.
540 860
541 This only works with certainty on POSIX (= UNIX) filesystems, which 861 This only works with certainty on POSIX (= UNIX) filesystems, which
… …
543 863
544 It will also likely work on non-POSIX filesystems with reduced 864 It will also likely work on non-POSIX filesystems with reduced
545 efficiency as those tend to return 0 or 1 as link counts, which 865 efficiency as those tend to return 0 or 1 as link counts, which
546 disables the directory counting heuristic. 866 disables the directory counting heuristic.
547 867
548 aio_rmtree $path, $callback->($status) 868 aio_rmtree $pathname, $callback->($status)
549 Delete a directory tree starting (and including) $path, return the 869 Delete a directory tree starting (and including) $path, return the
550 status of the final "rmdir" only. This is a composite request that 870 status of the final "rmdir" only. This is a composite request that
551 uses "aio_scandir" to recurse into and rmdir directories, and unlink 871 uses "aio_scandir" to recurse into and rmdir directories, and unlink
552 everything else. 872 everything else.
553 873
874 aio_fcntl $fh, $cmd, $arg, $callback->($status)
875 aio_ioctl $fh, $request, $buf, $callback->($status)
876 These work just like the "fcntl" and "ioctl" built-in functions,
877 except they execute asynchronously and pass the return value to the
878 callback.
879
880 Both calls can be used for a lot of things, some of which make more
881 sense to run asynchronously in their own thread, while some others
882 make less sense. For example, calls that block waiting for external
883 events, such as locking, will also lock down an I/O thread while it
884 is waiting, which can deadlock the whole I/O system. At the same
885 time, there might be no alternative to using a thread to wait.
886
887 So in general, you should only use these calls for things that do
888 (filesystem) I/O, not for things that wait for other events
889 (network, other processes), although if you are careful and know
890 what you are doing, you still can.
891
892 The following constants are available (missing ones are, as usual
893 0):
894
895 "F_DUPFD_CLOEXEC",
896
897 "F_OFD_GETLK", "F_OFD_SETLK", "F_OFD_GETLKW",
898
899 "FIFREEZE", "FITHAW", "FITRIM", "FICLONE", "FICLONERANGE",
900 "FIDEDUPERANGE".
901
902 "FS_IOC_GETFLAGS", "FS_IOC_SETFLAGS", "FS_IOC_GETVERSION",
903 "FS_IOC_SETVERSION", "FS_IOC_FIEMAP".
904
905 "FS_IOC_FSGETXATTR", "FS_IOC_FSSETXATTR",
906 "FS_IOC_SET_ENCRYPTION_POLICY", "FS_IOC_GET_ENCRYPTION_PWSALT",
907 "FS_IOC_GET_ENCRYPTION_POLICY", "FS_KEY_DESCRIPTOR_SIZE".
908
909 "FS_SECRM_FL", "FS_UNRM_FL", "FS_COMPR_FL", "FS_SYNC_FL",
910 "FS_IMMUTABLE_FL", "FS_APPEND_FL", "FS_NODUMP_FL", "FS_NOATIME_FL",
911 "FS_DIRTY_FL", "FS_COMPRBLK_FL", "FS_NOCOMP_FL", "FS_ENCRYPT_FL",
912 "FS_BTREE_FL", "FS_INDEX_FL", "FS_JOURNAL_DATA_FL", "FS_NOTAIL_FL",
913 "FS_DIRSYNC_FL", "FS_TOPDIR_FL", "FS_FL_USER_MODIFIABLE".
914
915 "FS_XFLAG_REALTIME", "FS_XFLAG_PREALLOC", "FS_XFLAG_IMMUTABLE",
916 "FS_XFLAG_APPEND", "FS_XFLAG_SYNC", "FS_XFLAG_NOATIME",
917 "FS_XFLAG_NODUMP", "FS_XFLAG_RTINHERIT", "FS_XFLAG_PROJINHERIT",
918 "FS_XFLAG_NOSYMLINKS", "FS_XFLAG_EXTSIZE", "FS_XFLAG_EXTSZINHERIT",
919 "FS_XFLAG_NODEFRAG", "FS_XFLAG_FILESTREAM", "FS_XFLAG_DAX",
920 "FS_XFLAG_HASATTR",
921
554 aio_sync $callback->($status) 922 aio_sync $callback->($status)
555 Asynchronously call sync and call the callback when finished. 923 Asynchronously call sync and call the callback when finished.
556 924
557 aio_fsync $fh, $callback->($status) 925 aio_fsync $fh, $callback->($status)
558 Asynchronously call fsync on the given filehandle and call the 926 Asynchronously call fsync on the given filehandle and call the
… …
563 callback with the fdatasync result code. 931 callback with the fdatasync result code.
564 932
565 If this call isn't available because your OS lacks it or it couldn't 933 If this call isn't available because your OS lacks it or it couldn't
566 be detected, it will be emulated by calling "fsync" instead. 934 be detected, it will be emulated by calling "fsync" instead.
567 935
936 aio_syncfs $fh, $callback->($status)
937 Asynchronously call the syncfs syscall to sync the filesystem
938 associated to the given filehandle and call the callback with the
939 syncfs result code. If syncfs is not available, calls sync(), but
940 returns -1 and sets errno to "ENOSYS" nevertheless.
941
942 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
943 Sync the data portion of the file specified by $offset and $length
944 to disk (but NOT the metadata), by calling the Linux-specific
945 sync_file_range call. If sync_file_range is not available or it
946 returns ENOSYS, then fdatasync or fsync is being substituted.
947
948 $flags can be a combination of
949 "IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE",
950 "IO::AIO::SYNC_FILE_RANGE_WRITE" and
951 "IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER": refer to the sync_file_range
952 manpage for details.
953
568 aio_pathsync $path, $callback->($status) 954 aio_pathsync $pathname, $callback->($status)
569 This request tries to open, fsync and close the given path. This is 955 This request tries to open, fsync and close the given path. This is
570 a composite request intended tosync directories after directory 956 a composite request intended to sync directories after directory
571 operations (E.g. rename). This might not work on all operating 957 operations (E.g. rename). This might not work on all operating
572 systems or have any specific effect, but usually it makes sure that 958 systems or have any specific effect, but usually it makes sure that
573 directory changes get written to disc. It works for anything that 959 directory changes get written to disc. It works for anything that
574 can be opened for read-only, not just directories. 960 can be opened for read-only, not just directories.
575 961
962 Future versions of this function might fall back to other methods
963 when "fsync" on the directory fails (such as calling "sync").
964
576 Passes 0 when everything went ok, and -1 on error. 965 Passes 0 when everything went ok, and -1 on error.
966
967 aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC,
968 $callback->($status)
969 This is a rather advanced IO::AIO call, which only works on
970 mmap(2)ed scalars (see the "IO::AIO::mmap" function, although it
971 also works on data scalars managed by the Sys::Mmap or Mmap modules,
972 note that the scalar must only be modified in-place while an aio
973 operation is pending on it).
974
975 It calls the "msync" function of your OS, if available, with the
976 memory area starting at $offset in the string and ending $length
977 bytes later. If $length is negative, counts from the end, and if
978 $length is "undef", then it goes till the end of the string. The
979 flags can be either "IO::AIO::MS_ASYNC" or "IO::AIO::MS_SYNC", plus
980 an optional "IO::AIO::MS_INVALIDATE".
981
982 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0,
983 $callback->($status)
984 This is a rather advanced IO::AIO call, which works best on
985 mmap(2)ed scalars.
986
987 It touches (reads or writes) all memory pages in the specified range
988 inside the scalar. All caveats and parameters are the same as for
989 "aio_msync", above, except for flags, which must be either 0 (which
990 reads all pages and ensures they are instantiated) or
991 "IO::AIO::MT_MODIFY", which modifies the memory pages (by reading
992 and writing an octet from it, which dirties the page).
993
994 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
995 This is a rather advanced IO::AIO call, which works best on
996 mmap(2)ed scalars.
997
998 It reads in all the pages of the underlying storage into memory (if
999 any) and locks them, so they are not getting swapped/paged out or
1000 removed.
1001
1002 If $length is undefined, then the scalar will be locked till the
1003 end.
1004
1005 On systems that do not implement "mlock", this function returns -1
1006 and sets errno to "ENOSYS".
1007
1008 Note that the corresponding "munlock" is synchronous and is
1009 documented under "MISCELLANEOUS FUNCTIONS".
1010
1011 Example: open a file, mmap and mlock it - both will be undone when
1012 $data gets destroyed.
1013
1014 open my $fh, "<", $path or die "$path: $!";
1015 my $data;
1016 IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
1017 aio_mlock $data; # mlock in background
1018
1019 aio_mlockall $flags, $callback->($status)
1020 Calls the "mlockall" function with the given $flags (a combination
1021 of "IO::AIO::MCL_CURRENT" and "IO::AIO::MCL_FUTURE").
1022
1023 On systems that do not implement "mlockall", this function returns
1024 -1 and sets errno to "ENOSYS".
1025
1026 Note that the corresponding "munlockall" is synchronous and is
1027 documented under "MISCELLANEOUS FUNCTIONS".
1028
1029 Example: asynchronously lock all current and future pages into
1030 memory.
1031
1032 aio_mlockall IO::AIO::MCL_FUTURE;
1033
1034 aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
1035 Queries the extents of the given file (by calling the Linux "FIEMAP"
1036 ioctl, see <http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for
1037 details). If the ioctl is not available on your OS, then this
1038 request will fail with "ENOSYS".
1039
1040 $start is the starting offset to query extents for, $length is the
1041 size of the range to query - if it is "undef", then the whole file
1042 will be queried.
1043
1044 $flags is a combination of flags ("IO::AIO::FIEMAP_FLAG_SYNC" or
1045 "IO::AIO::FIEMAP_FLAG_XATTR" - "IO::AIO::FIEMAP_FLAGS_COMPAT" is
1046 also exported), and is normally 0 or "IO::AIO::FIEMAP_FLAG_SYNC" to
1047 query the data portion.
1048
1049 $count is the maximum number of extent records to return. If it is
1050 "undef", then IO::AIO queries all extents of the range. As a very
1051 special case, if it is 0, then the callback receives the number of
1052 extents instead of the extents themselves (which is unreliable, see
1053 below).
1054
1055 If an error occurs, the callback receives no arguments. The special
1056 "errno" value "IO::AIO::EBADR" is available to test for flag errors.
1057
1058 Otherwise, the callback receives an array reference with extent
1059 structures. Each extent structure is an array reference itself, with
1060 the following members:
1061
1062 [$logical, $physical, $length, $flags]
1063
1064 Flags is any combination of the following flag values (typically
1065 either 0 or "IO::AIO::FIEMAP_EXTENT_LAST" (1)):
1066
1067 "IO::AIO::FIEMAP_EXTENT_LAST", "IO::AIO::FIEMAP_EXTENT_UNKNOWN",
1068 "IO::AIO::FIEMAP_EXTENT_DELALLOC", "IO::AIO::FIEMAP_EXTENT_ENCODED",
1069 "IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED",
1070 "IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED",
1071 "IO::AIO::FIEMAP_EXTENT_DATA_INLINE",
1072 "IO::AIO::FIEMAP_EXTENT_DATA_TAIL",
1073 "IO::AIO::FIEMAP_EXTENT_UNWRITTEN", "IO::AIO::FIEMAP_EXTENT_MERGED"
1074 or "IO::AIO::FIEMAP_EXTENT_SHARED".
1075
1076 At the time of this writing (Linux 3.2), this request is unreliable
1077 unless $count is "undef", as the kernel has all sorts of bugs
1078 preventing it to return all extents of a range for files with a
1079 large number of extents. The code (only) works around all these
1080 issues if $count is "undef".
577 1081
578 aio_group $callback->(...) 1082 aio_group $callback->(...)
579 This is a very special aio request: Instead of doing something, it 1083 This is a very special aio request: Instead of doing something, it
580 is a container for other aio requests, which is useful if you want 1084 is a container for other aio requests, which is useful if you want
581 to bundle many requests into a single, composite, request with a 1085 to bundle many requests into a single, composite, request with a
… …
616 requests like sleep and file handle readable/writable, the overhead 1120 requests like sleep and file handle readable/writable, the overhead
617 this creates is immense (it blocks a thread for a long time) so do 1121 this creates is immense (it blocks a thread for a long time) so do
618 not use this function except to put your application under 1122 not use this function except to put your application under
619 artificial I/O pressure. 1123 artificial I/O pressure.
620 1124
1125 IO::AIO::WD - multiple working directories
1126 Your process only has one current working directory, which is used by
1127 all threads. This makes it hard to use relative paths (some other
1128 component could call "chdir" at any time, and it is hard to control when
1129 the path will be used by IO::AIO).
1130
1131 One solution for this is to always use absolute paths. This usually
1132 works, but can be quite slow (the kernel has to walk the whole path on
1133 every access), and can also be a hassle to implement.
1134
1135 Newer POSIX systems have a number of functions (openat, fdopendir,
1136 futimensat and so on) that make it possible to specify working
1137 directories per operation.
1138
1139 For portability, and because the clowns who "designed", or shall I
1140 write, perpetrated this new interface were obviously half-drunk, this
1141 abstraction cannot be perfect, though.
1142
1143 IO::AIO allows you to convert directory paths into a so-called
1144 IO::AIO::WD object. This object stores the canonicalised, absolute
1145 version of the path, and on systems that allow it, also a directory file
1146 descriptor.
1147
1148 Everywhere where a pathname is accepted by IO::AIO (e.g. in "aio_stat"
1149 or "aio_unlink"), one can specify an array reference with an IO::AIO::WD
1150 object and a pathname instead (or the IO::AIO::WD object alone, which
1151 gets interpreted as "[$wd, "."]"). If the pathname is absolute, the
1152 IO::AIO::WD object is ignored, otherwise the pathname is resolved
1153 relative to that IO::AIO::WD object.
1154
1155 For example, to get a wd object for /etc and then stat passwd inside,
1156 you would write:
1157
1158 aio_wd "/etc", sub {
1159 my $etcdir = shift;
1160
1161 # although $etcdir can be undef on error, there is generally no reason
1162 # to check for errors here, as aio_stat will fail with ENOENT
1163 # when $etcdir is undef.
1164
1165 aio_stat [$etcdir, "passwd"], sub {
1166 # yay
1167 };
1168 };
1169
1170 The fact that "aio_wd" is a request and not a normal function shows that
1171 creating an IO::AIO::WD object is itself a potentially blocking
1172 operation, which is why it is done asynchronously.
1173
1174 To stat the directory obtained with "aio_wd" above, one could write
1175 either of the following three request calls:
1176
1177 aio_lstat "/etc" , sub { ... # pathname as normal string
1178 aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
1179 aio_lstat $wd , sub { ... # shorthand for the previous
1180
1181 As with normal pathnames, IO::AIO keeps a copy of the working directory
1182 object and the pathname string, so you could write the following without
1183 causing any issues due to $path getting reused:
1184
1185 my $path = [$wd, undef];
1186
1187 for my $name (qw(abc def ghi)) {
1188 $path->[1] = $name;
1189 aio_stat $path, sub {
1190 # ...
1191 };
1192 }
1193
1194 There are some caveats: when directories get renamed (or deleted), the
1195 pathname string doesn't change, so will point to the new directory (or
1196 nowhere at all), while the directory fd, if available on the system,
1197 will still point to the original directory. Most functions accepting a
1198 pathname will use the directory fd on newer systems, and the string on
1199 older systems. Some functions (such as "aio_realpath") will always rely
1200 on the string form of the pathname.
1201
1202 So this functionality is mainly useful to get some protection against
1203 "chdir", to easily get an absolute path out of a relative path for
1204 future reference, and to speed up doing many operations in the same
1205 directory (e.g. when stat'ing all files in a directory).
1206
1207 The following functions implement this working directory abstraction:
1208
1209 aio_wd $pathname, $callback->($wd)
1210 Asynchonously canonicalise the given pathname and convert it to an
1211 IO::AIO::WD object representing it. If possible and supported on the
1212 system, also open a directory fd to speed up pathname resolution
1213 relative to this working directory.
1214
1215 If something goes wrong, then "undef" is passwd to the callback
1216 instead of a working directory object and $! is set appropriately.
1217 Since passing "undef" as working directory component of a pathname
1218 fails the request with "ENOENT", there is often no need for error
1219 checking in the "aio_wd" callback, as future requests using the
1220 value will fail in the expected way.
1221
1222 IO::AIO::CWD
1223 This is a compiletime constant (object) that represents the process
1224 current working directory.
1225
1226 Specifying this object as working directory object for a pathname is
1227 as if the pathname would be specified directly, without a directory
1228 object. For example, these calls are functionally identical:
1229
1230 aio_stat "somefile", sub { ... };
1231 aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
1232
1233 To recover the path associated with an IO::AIO::WD object, you can use
1234 "aio_realpath":
1235
1236 aio_realpath $wd, sub {
1237 warn "path is $_[0]\n";
1238 };
1239
1240 Currently, "aio_statvfs" always, and "aio_rename" and "aio_rmdir"
1241 sometimes, fall back to using an absolue path.
1242
621 IO::AIO::REQ CLASS 1243 IO::AIO::REQ CLASS
622 All non-aggregate "aio_*" functions return an object of this class when 1244 All non-aggregate "aio_*" functions return an object of this class when
623 called in non-void context. 1245 called in non-void context.
624 1246
625 cancel $req 1247 cancel $req
626 Cancels the request, if possible. Has the effect of skipping 1248 Cancels the request, if possible. Has the effect of skipping
627 execution when entering the execute state and skipping calling the 1249 execution when entering the execute state and skipping calling the
628 callback when entering the the result state, but will leave the 1250 callback when entering the the result state, but will leave the
629 request otherwise untouched. That means that requests that currently 1251 request otherwise untouched (with the exception of readdir). That
630 execute will not be stopped and resources held by the request will 1252 means that requests that currently execute will not be stopped and
631 not be freed prematurely. 1253 resources held by the request will not be freed prematurely.
632 1254
633 cb $req $callback->(...) 1255 cb $req $callback->(...)
634 Replace (or simply set) the callback registered to the request. 1256 Replace (or simply set) the callback registered to the request.
635 1257
636 IO::AIO::GRP CLASS 1258 IO::AIO::GRP CLASS
… …
679 Their lifetime, simplified, looks like this: when they are empty, they 1301 Their lifetime, simplified, looks like this: when they are empty, they
680 will finish very quickly. If they contain only requests that are in the 1302 will finish very quickly. If they contain only requests that are in the
681 "done" state, they will also finish. Otherwise they will continue to 1303 "done" state, they will also finish. Otherwise they will continue to
682 exist. 1304 exist.
683 1305
684 That means after creating a group you have some time to add requests. 1306 That means after creating a group you have some time to add requests
685 And in the callbacks of those requests, you can add further requests to 1307 (precisely before the callback has been invoked, which is only done
686 the group. And only when all those requests have finished will the the 1308 within the "poll_cb"). And in the callbacks of those requests, you can
687 group itself finish. 1309 add further requests to the group. And only when all those requests have
1310 finished will the the group itself finish.
688 1311
689 add $grp ... 1312 add $grp ...
690 $grp->add (...) 1313 $grp->add (...)
691 Add one or more requests to the group. Any type of IO::AIO::REQ can 1314 Add one or more requests to the group. Any type of IO::AIO::REQ can
692 be added, including other groups, as long as you do not create 1315 be added, including other groups, as long as you do not create
… …
696 1319
697 $grp->cancel_subs 1320 $grp->cancel_subs
698 Cancel all subrequests and clears any feeder, but not the group 1321 Cancel all subrequests and clears any feeder, but not the group
699 request itself. Useful when you queued a lot of events but got a 1322 request itself. Useful when you queued a lot of events but got a
700 result early. 1323 result early.
1324
1325 The group request will finish normally (you cannot add requests to
1326 the group).
701 1327
702 $grp->result (...) 1328 $grp->result (...)
703 Set the result value(s) that will be passed to the group callback 1329 Set the result value(s) that will be passed to the group callback
704 when all subrequests have finished and set the groups errno to the 1330 when all subrequests have finished and set the groups errno to the
705 current value of errno (just like calling "errno" without an error 1331 current value of errno (just like calling "errno" without an error
… …
720 Sets a feeder/generator on this group: every group can have an 1346 Sets a feeder/generator on this group: every group can have an
721 attached generator that generates requests if idle. The idea behind 1347 attached generator that generates requests if idle. The idea behind
722 this is that, although you could just queue as many requests as you 1348 this is that, although you could just queue as many requests as you
723 want in a group, this might starve other requests for a potentially 1349 want in a group, this might starve other requests for a potentially
724 long time. For example, "aio_scandir" might generate hundreds of 1350 long time. For example, "aio_scandir" might generate hundreds of
725 thousands "aio_stat" requests, delaying any later requests for a 1351 thousands of "aio_stat" requests, delaying any later requests for a
726 long time. 1352 long time.
727 1353
728 To avoid this, and allow incremental generation of requests, you can 1354 To avoid this, and allow incremental generation of requests, you can
729 instead a group and set a feeder on it that generates those 1355 instead a group and set a feeder on it that generates those
730 requests. The feed callback will be called whenever there are few 1356 requests. The feed callback will be called whenever there are few
… …
735 does not impose any limits). 1361 does not impose any limits).
736 1362
737 If the feed does not queue more requests when called, it will be 1363 If the feed does not queue more requests when called, it will be
738 automatically removed from the group. 1364 automatically removed from the group.
739 1365
740 If the feed limit is 0, it will be set to 2 automatically. 1366 If the feed limit is 0 when this method is called, it will be set to
1367 2 automatically.
741 1368
742 Example: 1369 Example:
743 1370
744 # stat all files in @files, but only ever use four aio requests concurrently: 1371 # stat all files in @files, but only ever use four aio requests concurrently:
745 1372
… …
756 Sets the feeder limit for the group: The feeder will be called 1383 Sets the feeder limit for the group: The feeder will be called
757 whenever the group contains less than this many requests. 1384 whenever the group contains less than this many requests.
758 1385
759 Setting the limit to 0 will pause the feeding process. 1386 Setting the limit to 0 will pause the feeding process.
760 1387
1388 The default value for the limit is 0, but note that setting a feeder
1389 automatically bumps it up to 2.
1390
761 SUPPORT FUNCTIONS 1391 SUPPORT FUNCTIONS
762 EVENT PROCESSING AND EVENT LOOP INTEGRATION 1392 EVENT PROCESSING AND EVENT LOOP INTEGRATION
763 $fileno = IO::AIO::poll_fileno 1393 $fileno = IO::AIO::poll_fileno
764 Return the *request result pipe file descriptor*. This filehandle 1394 Return the *request result pipe file descriptor*. This filehandle
765 must be polled for reading by some mechanism outside this module 1395 must be polled for reading by some mechanism outside this module
766 (e.g. Event or select, see below or the SYNOPSIS). If the pipe 1396 (e.g. EV, Glib, select and so on, see below or the SYNOPSIS). If the
767 becomes readable you have to call "poll_cb" to check the results. 1397 pipe becomes readable you have to call "poll_cb" to check the
1398 results.
768 1399
769 See "poll_cb" for an example. 1400 See "poll_cb" for an example.
770 1401
771 IO::AIO::poll_cb 1402 IO::AIO::poll_cb
772 Process some outstanding events on the result pipe. You have to call 1403 Process some requests that have reached the result phase (i.e. they
773 this regularly. Returns the number of events processed. Returns 1404 have been executed but the results are not yet reported). You have
1405 to call this "regularly" to finish outstanding requests.
1406
1407 Returns 0 if all events could be processed (or there were no events
1408 to process), or -1 if it returned earlier for whatever reason.
774 immediately when no events are outstanding. The amount of events 1409 Returns immediately when no events are outstanding. The amount of
775 processed depends on the settings of "IO::AIO::max_poll_req" and 1410 events processed depends on the settings of "IO::AIO::max_poll_req",
776 "IO::AIO::max_poll_time". 1411 "IO::AIO::max_poll_time" and "IO::AIO::max_outstanding".
777 1412
778 If not all requests were processed for whatever reason, the 1413 If not all requests were processed for whatever reason, the poll
779 filehandle will still be ready when "poll_cb" returns. 1414 file descriptor will still be ready when "poll_cb" returns, so
1415 normally you don't have to do anything special to have it called
1416 later.
1417
1418 Apart from calling "IO::AIO::poll_cb" when the event filehandle
1419 becomes ready, it can be beneficial to call this function from loops
1420 which submit a lot of requests, to make sure the results get
1421 processed when they become available and not just when the loop is
1422 finished and the event loop takes over again. This function returns
1423 very fast when there are no outstanding requests.
780 1424
781 Example: Install an Event watcher that automatically calls 1425 Example: Install an Event watcher that automatically calls
782 IO::AIO::poll_cb with high priority: 1426 IO::AIO::poll_cb with high priority (more examples can be found in
1427 the SYNOPSIS section, at the top of this document):
783 1428
784 Event->io (fd => IO::AIO::poll_fileno, 1429 Event->io (fd => IO::AIO::poll_fileno,
785 poll => 'r', async => 1, 1430 poll => 'r', async => 1,
786 cb => \&IO::AIO::poll_cb); 1431 cb => \&IO::AIO::poll_cb);
1432
1433 IO::AIO::poll_wait
1434 Wait until either at least one request is in the result phase or no
1435 requests are outstanding anymore.
1436
1437 This is useful if you want to synchronously wait for some requests
1438 to become ready, without actually handling them.
1439
1440 See "nreqs" for an example.
1441
1442 IO::AIO::poll
1443 Waits until some requests have been handled.
1444
1445 Returns the number of requests processed, but is otherwise strictly
1446 equivalent to:
1447
1448 IO::AIO::poll_wait, IO::AIO::poll_cb
1449
1450 IO::AIO::flush
1451 Wait till all outstanding AIO requests have been handled.
1452
1453 Strictly equivalent to:
1454
1455 IO::AIO::poll_wait, IO::AIO::poll_cb
1456 while IO::AIO::nreqs;
1457
1458 This function can be useful at program aborts, to make sure
1459 outstanding I/O has been done ("IO::AIO" uses an "END" block which
1460 already calls this function on normal exits), or when you are merely
1461 using "IO::AIO" for its more advanced functions, rather than for
1462 async I/O, e.g.:
1463
1464 my ($dirs, $nondirs);
1465 IO::AIO::aio_scandir "/tmp", 0, sub { ($dirs, $nondirs) = @_ };
1466 IO::AIO::flush;
1467 # $dirs, $nondirs are now set
787 1468
788 IO::AIO::max_poll_reqs $nreqs 1469 IO::AIO::max_poll_reqs $nreqs
789 IO::AIO::max_poll_time $seconds 1470 IO::AIO::max_poll_time $seconds
790 These set the maximum number of requests (default 0, meaning 1471 These set the maximum number of requests (default 0, meaning
791 infinity) that are being processed by "IO::AIO::poll_cb" in one 1472 infinity) that are being processed by "IO::AIO::poll_cb" in one
… …
815 # use a low priority so other tasks have priority 1496 # use a low priority so other tasks have priority
816 Event->io (fd => IO::AIO::poll_fileno, 1497 Event->io (fd => IO::AIO::poll_fileno,
817 poll => 'r', nice => 1, 1498 poll => 'r', nice => 1,
818 cb => &IO::AIO::poll_cb); 1499 cb => &IO::AIO::poll_cb);
819 1500
820 IO::AIO::poll_wait
821 If there are any outstanding requests and none of them in the result
822 phase, wait till the result filehandle becomes ready for reading
823 (simply does a "select" on the filehandle. This is useful if you
824 want to synchronously wait for some requests to finish).
825
826 See "nreqs" for an example.
827
828 IO::AIO::poll
829 Waits until some requests have been handled.
830
831 Returns the number of requests processed, but is otherwise strictly
832 equivalent to:
833
834 IO::AIO::poll_wait, IO::AIO::poll_cb
835
836 IO::AIO::flush
837 Wait till all outstanding AIO requests have been handled.
838
839 Strictly equivalent to:
840
841 IO::AIO::poll_wait, IO::AIO::poll_cb
842 while IO::AIO::nreqs;
843
844 CONTROLLING THE NUMBER OF THREADS 1501 CONTROLLING THE NUMBER OF THREADS
845 IO::AIO::min_parallel $nthreads 1502 IO::AIO::min_parallel $nthreads
846 Set the minimum number of AIO threads to $nthreads. The current 1503 Set the minimum number of AIO threads to $nthreads. The current
847 default is 8, which means eight asynchronous operations can execute 1504 default is 8, which means eight asynchronous operations can execute
848 concurrently at any one time (the number of outstanding requests, 1505 concurrently at any one time (the number of outstanding requests,
… …
877 1534
878 Under normal circumstances you don't need to call this function. 1535 Under normal circumstances you don't need to call this function.
879 1536
880 IO::AIO::max_idle $nthreads 1537 IO::AIO::max_idle $nthreads
881 Limit the number of threads (default: 4) that are allowed to idle 1538 Limit the number of threads (default: 4) that are allowed to idle
882 (i.e., threads that did not get a request to process within 10 1539 (i.e., threads that did not get a request to process within the idle
883 seconds). That means if a thread becomes idle while $nthreads other 1540 timeout (default: 10 seconds). That means if a thread becomes idle
884 threads are also idle, it will free its resources and exit. 1541 while $nthreads other threads are also idle, it will free its
1542 resources and exit.
885 1543
886 This is useful when you allow a large number of threads (e.g. 100 or 1544 This is useful when you allow a large number of threads (e.g. 100 or
887 1000) to allow for extremely high load situations, but want to free 1545 1000) to allow for extremely high load situations, but want to free
888 resources under normal circumstances (1000 threads can easily 1546 resources under normal circumstances (1000 threads can easily
889 consume 30MB of RAM). 1547 consume 30MB of RAM).
890 1548
891 The default is probably ok in most situations, especially if thread 1549 The default is probably ok in most situations, especially if thread
892 creation is fast. If thread creation is very slow on your system you 1550 creation is fast. If thread creation is very slow on your system you
893 might want to use larger values. 1551 might want to use larger values.
894 1552
1553 IO::AIO::idle_timeout $seconds
1554 Sets the minimum idle timeout (default 10) after which worker
1555 threads are allowed to exit. SEe "IO::AIO::max_idle".
1556
895 $oldmaxreqs = IO::AIO::max_outstanding $maxreqs 1557 IO::AIO::max_outstanding $maxreqs
1558 Sets the maximum number of outstanding requests to $nreqs. If you do
1559 queue up more than this number of requests, the next call to
1560 "IO::AIO::poll_cb" (and other functions calling "poll_cb", such as
1561 "IO::AIO::flush" or "IO::AIO::poll") will block until the limit is
1562 no longer exceeded.
1563
1564 In other words, this setting does not enforce a queue limit, but can
1565 be used to make poll functions block if the limit is exceeded.
1566
896 This is a very bad function to use in interactive programs because 1567 This is a very bad function to use in interactive programs because
897 it blocks, and a bad way to reduce concurrency because it is 1568 it blocks, and a bad way to reduce concurrency because it is
898 inexact: Better use an "aio_group" together with a feed callback. 1569 inexact: Better use an "aio_group" together with a feed callback.
899 1570
900 Sets the maximum number of outstanding requests to $nreqs. If you do 1571 Its main use is in scripts without an event loop - when you want to
901 queue up more than this number of requests, the next call to the 1572 stat a lot of files, you can write something like this:
902 "poll_cb" (and "poll_some" and other functions calling "poll_cb")
903 function will block until the limit is no longer exceeded.
904 1573
905 The default value is very large, so there is no practical limit on 1574 IO::AIO::max_outstanding 32;
1575
1576 for my $path (...) {
1577 aio_stat $path , ...;
1578 IO::AIO::poll_cb;
1579 }
1580
1581 IO::AIO::flush;
1582
1583 The call to "poll_cb" inside the loop will normally return
1584 instantly, but as soon as more thna 32 reqeusts are in-flight, it
1585 will block until some requests have been handled. This keeps the
1586 loop from pushing a large number of "aio_stat" requests onto the
1587 queue.
1588
1589 The default value for "max_outstanding" is very large, so there is
906 the number of outstanding requests. 1590 no practical limit on the number of outstanding requests.
907
908 You can still queue as many requests as you want. Therefore,
909 "max_oustsanding" is mainly useful in simple scripts (with low
910 values) or as a stop gap to shield against fatal memory overflow
911 (with large values).
912 1591
913 STATISTICAL INFORMATION 1592 STATISTICAL INFORMATION
914 IO::AIO::nreqs 1593 IO::AIO::nreqs
915 Returns the number of requests currently in the ready, execute or 1594 Returns the number of requests currently in the ready, execute or
916 pending states (i.e. for which their callback has not been invoked 1595 pending states (i.e. for which their callback has not been invoked
… …
927 1606
928 IO::AIO::npending 1607 IO::AIO::npending
929 Returns the number of requests currently in the pending state 1608 Returns the number of requests currently in the pending state
930 (executed, but not yet processed by poll_cb). 1609 (executed, but not yet processed by poll_cb).
931 1610
1611 SUBSECOND STAT TIME ACCESS
1612 Both "aio_stat"/"aio_lstat" and perl's "stat"/"lstat" functions can
1613 generally find access/modification and change times with subsecond time
1614 accuracy of the system supports it, but perl's built-in functions only
1615 return the integer part.
1616
1617 The following functions return the timestamps of the most recent stat
1618 with subsecond precision on most systems and work both after
1619 "aio_stat"/"aio_lstat" and perl's "stat"/"lstat" calls. Their return
1620 value is only meaningful after a successful "stat"/"lstat" call, or
1621 during/after a successful "aio_stat"/"aio_lstat" callback.
1622
1623 This is similar to the Time::HiRes "stat" functions, but can return full
1624 resolution without rounding and work with standard perl "stat",
1625 alleviating the need to call the special "Time::HiRes" functions, which
1626 do not act like their perl counterparts.
1627
1628 On operating systems or file systems where subsecond time resolution is
1629 not supported or could not be detected, a fractional part of 0 is
1630 returned, so it is always safe to call these functions.
1631
1632 $seconds = IO::AIO::st_atime, IO::AIO::st_mtime, IO::AIO::st_ctime,
1633 IO::AIO::st_btime
1634 Return the access, modication, change or birth time, respectively,
1635 including fractional part. Due to the limited precision of floating
1636 point, the accuracy on most platforms is only a bit better than
1637 milliseconds for times around now - see the *nsec* function family,
1638 below, for full accuracy.
1639
1640 File birth time is only available when the OS and perl support it
1641 (on FreeBSD and NetBSD at the time of this writing, although support
1642 is adaptive, so if your OS/perl gains support, IO::AIO can take
1643 avdantage of it). On systems where it isn't available, 0 is
1644 currently returned, but this might change to "undef" in a future
1645 version.
1646
1647 ($atime, $mtime, $ctime, $btime, ...) = IO::AIO::st_xtime
1648 Returns access, modification, change and birth time all in one go,
1649 and maybe more times in the future version.
1650
1651 $nanoseconds = IO::AIO::st_atimensec, IO::AIO::st_mtimensec,
1652 IO::AIO::st_ctimensec, IO::AIO::st_btimensec
1653 Return the fractional access, modifcation, change or birth time, in
1654 nanoseconds, as an integer in the range 0 to 999999999.
1655
1656 Note that no accessors are provided for access, modification and
1657 change times - you need to get those from "stat _" if required ("int
1658 IO::AIO::st_atime" and so on will *not* generally give you the
1659 correct value).
1660
1661 $seconds = IO::AIO::st_btimesec
1662 The (integral) seconds part of the file birth time, if available.
1663
1664 ($atime, $mtime, $ctime, $btime, ...) = IO::AIO::st_xtimensec
1665 Like the functions above, but returns all four times in one go (and
1666 maybe more in future versions).
1667
1668 $counter = IO::AIO::st_gen
1669 Returns the generation counter of the file. This is only available
1670 on platforms which have this member in their "struct stat" (most
1671 BSDs at the time of this writing) and generally only to the root
1672 usert. If unsupported, 0 is returned, but this might change to
1673 "undef" in a future version.
1674
1675 Example: print the high resolution modification time of /etc, using
1676 "stat", and "IO::AIO::aio_stat".
1677
1678 if (stat "/etc") {
1679 printf "stat(/etc) mtime: %f\n", IO::AIO::st_mtime;
1680 }
1681
1682 IO::AIO::aio_stat "/etc", sub {
1683 $_[0]
1684 and return;
1685
1686 printf "aio_stat(/etc) mtime: %d.%09d\n", (stat _)[9], IO::AIO::st_mtimensec;
1687 };
1688
1689 IO::AIO::flush;
1690
1691 Output of the awbove on my system, showing reduced and full accuracy:
1692
1693 stat(/etc) mtime: 1534043702.020808
1694 aio_stat(/etc) mtime: 1534043702.020807792
1695
1696 MISCELLANEOUS FUNCTIONS
1697 IO::AIO implements some functions that are useful when you want to use
1698 some "Advanced I/O" function not available to in Perl, without going the
1699 "Asynchronous I/O" route. Many of these have an asynchronous "aio_*"
1700 counterpart.
1701
1702 $numfd = IO::AIO::get_fdlimit
1703 This function is *EXPERIMENTAL* and subject to change.
1704
1705 Tries to find the current file descriptor limit and returns it, or
1706 "undef" and sets $! in case of an error. The limit is one larger
1707 than the highest valid file descriptor number.
1708
1709 IO::AIO::min_fdlimit [$numfd]
1710 This function is *EXPERIMENTAL* and subject to change.
1711
1712 Try to increase the current file descriptor limit(s) to at least
1713 $numfd by changing the soft or hard file descriptor resource limit.
1714 If $numfd is missing, it will try to set a very high limit, although
1715 this is not recommended when you know the actual minimum that you
1716 require.
1717
1718 If the limit cannot be raised enough, the function makes a
1719 best-effort attempt to increase the limit as much as possible, using
1720 various tricks, while still failing. You can query the resulting
1721 limit using "IO::AIO::get_fdlimit".
1722
1723 If an error occurs, returns "undef" and sets $!, otherwise returns
1724 true.
1725
1726 IO::AIO::sendfile $ofh, $ifh, $offset, $count
1727 Calls the "eio_sendfile_sync" function, which is like
1728 "aio_sendfile", but is blocking (this makes most sense if you know
1729 the input data is likely cached already and the output filehandle is
1730 set to non-blocking operations).
1731
1732 Returns the number of bytes copied, or -1 on error.
1733
1734 IO::AIO::fadvise $fh, $offset, $len, $advice
1735 Simply calls the "posix_fadvise" function (see its manpage for
1736 details). The following advice constants are available:
1737 "IO::AIO::FADV_NORMAL", "IO::AIO::FADV_SEQUENTIAL",
1738 "IO::AIO::FADV_RANDOM", "IO::AIO::FADV_NOREUSE",
1739 "IO::AIO::FADV_WILLNEED", "IO::AIO::FADV_DONTNEED".
1740
1741 On systems that do not implement "posix_fadvise", this function
1742 returns ENOSYS, otherwise the return value of "posix_fadvise".
1743
1744 IO::AIO::madvise $scalar, $offset, $len, $advice
1745 Simply calls the "posix_madvise" function (see its manpage for
1746 details). The following advice constants are available:
1747 "IO::AIO::MADV_NORMAL", "IO::AIO::MADV_SEQUENTIAL",
1748 "IO::AIO::MADV_RANDOM", "IO::AIO::MADV_WILLNEED",
1749 "IO::AIO::MADV_DONTNEED".
1750
1751 If $offset is negative, counts from the end. If $length is negative,
1752 the remaining length of the $scalar is used. If possible, $length
1753 will be reduced to fit into the $scalar.
1754
1755 On systems that do not implement "posix_madvise", this function
1756 returns ENOSYS, otherwise the return value of "posix_madvise".
1757
1758 IO::AIO::mprotect $scalar, $offset, $len, $protect
1759 Simply calls the "mprotect" function on the preferably AIO::mmap'ed
1760 $scalar (see its manpage for details). The following protect
1761 constants are available: "IO::AIO::PROT_NONE", "IO::AIO::PROT_READ",
1762 "IO::AIO::PROT_WRITE", "IO::AIO::PROT_EXEC".
1763
1764 If $offset is negative, counts from the end. If $length is negative,
1765 the remaining length of the $scalar is used. If possible, $length
1766 will be reduced to fit into the $scalar.
1767
1768 On systems that do not implement "mprotect", this function returns
1769 ENOSYS, otherwise the return value of "mprotect".
1770
1771 IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
1772 Memory-maps a file (or anonymous memory range) and attaches it to
1773 the given $scalar, which will act like a string scalar. Returns true
1774 on success, and false otherwise.
1775
1776 The scalar must exist, but its contents do not matter - this means
1777 you cannot use a nonexistant array or hash element. When in doubt,
1778 "undef" the scalar first.
1779
1780 The only operations allowed on the mmapped scalar are
1781 "substr"/"vec", which don't change the string length, and most
1782 read-only operations such as copying it or searching it with regexes
1783 and so on.
1784
1785 Anything else is unsafe and will, at best, result in memory leaks.
1786
1787 The memory map associated with the $scalar is automatically removed
1788 when the $scalar is undef'd or destroyed, or when the
1789 "IO::AIO::mmap" or "IO::AIO::munmap" functions are called on it.
1790
1791 This calls the "mmap"(2) function internally. See your system's
1792 manual page for details on the $length, $prot and $flags parameters.
1793
1794 The $length must be larger than zero and smaller than the actual
1795 filesize.
1796
1797 $prot is a combination of "IO::AIO::PROT_NONE",
1798 "IO::AIO::PROT_EXEC", "IO::AIO::PROT_READ" and/or
1799 "IO::AIO::PROT_WRITE",
1800
1801 $flags can be a combination of "IO::AIO::MAP_SHARED" or
1802 "IO::AIO::MAP_PRIVATE", or a number of system-specific flags (when
1803 not available, the are 0): "IO::AIO::MAP_ANONYMOUS" (which is set to
1804 "MAP_ANON" if your system only provides this constant),
1805 "IO::AIO::MAP_LOCKED", "IO::AIO::MAP_NORESERVE",
1806 "IO::AIO::MAP_POPULATE", "IO::AIO::MAP_NONBLOCK",
1807 "IO::AIO::MAP_FIXED", "IO::AIO::MAP_GROWSDOWN",
1808 "IO::AIO::MAP_32BIT", "IO::AIO::MAP_HUGETLB" or
1809 "IO::AIO::MAP_STACK".
1810
1811 If $fh is "undef", then a file descriptor of -1 is passed.
1812
1813 $offset is the offset from the start of the file - it generally must
1814 be a multiple of "IO::AIO::PAGESIZE" and defaults to 0.
1815
1816 Example:
1817
1818 use Digest::MD5;
1819 use IO::AIO;
1820
1821 open my $fh, "<verybigfile"
1822 or die "$!";
1823
1824 IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
1825 or die "verybigfile: $!";
1826
1827 my $fast_md5 = md5 $data;
1828
1829 IO::AIO::munmap $scalar
1830 Removes a previous mmap and undefines the $scalar.
1831
1832 IO::AIO::mremap $scalar, $new_length, $flags = MREMAP_MAYMOVE[,
1833 $new_address = 0]
1834 Calls the Linux-specific mremap(2) system call. The $scalar must
1835 have been mapped by "IO::AIO::mmap", and $flags must currently
1836 either be 0 or "IO::AIO::MREMAP_MAYMOVE".
1837
1838 Returns true if successful, and false otherwise. If the underlying
1839 mmapped region has changed address, then the true value has the
1840 numerical value 1, otherwise it has the numerical value 0:
1841
1842 my $success = IO::AIO::mremap $mmapped, 8192, IO::AIO::MREMAP_MAYMOVE
1843 or die "mremap: $!";
1844
1845 if ($success*1) {
1846 warn "scalar has chanegd address in memory\n";
1847 }
1848
1849 "IO::AIO::MREMAP_FIXED" and the $new_address argument are currently
1850 implemented, but not supported and might go away in a future
1851 version.
1852
1853 On systems where this call is not supported or is not emulated, this
1854 call returns falls and sets $! to "ENOSYS".
1855
1856 IO::AIO::munlock $scalar, $offset = 0, $length = undef
1857 Calls the "munlock" function, undoing the effects of a previous
1858 "aio_mlock" call (see its description for details).
1859
1860 IO::AIO::munlockall
1861 Calls the "munlockall" function.
1862
1863 On systems that do not implement "munlockall", this function returns
1864 ENOSYS, otherwise the return value of "munlockall".
1865
1866 IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
1867 Calls the GNU/Linux splice(2) syscall, if available. If $r_off or
1868 $w_off are "undef", then "NULL" is passed for these, otherwise they
1869 should be the file offset.
1870
1871 $r_fh and $w_fh should not refer to the same file, as splice might
1872 silently corrupt the data in this case.
1873
1874 The following symbol flag values are available:
1875 "IO::AIO::SPLICE_F_MOVE", "IO::AIO::SPLICE_F_NONBLOCK",
1876 "IO::AIO::SPLICE_F_MORE" and "IO::AIO::SPLICE_F_GIFT".
1877
1878 See the splice(2) manpage for details.
1879
1880 IO::AIO::tee $r_fh, $w_fh, $length, $flags
1881 Calls the GNU/Linux tee(2) syscall, see its manpage and the
1882 description for "IO::AIO::splice" above for details.
1883
1884 $actual_size = IO::AIO::pipesize $r_fh[, $new_size]
1885 Attempts to query or change the pipe buffer size. Obviously works
1886 only on pipes, and currently works only on GNU/Linux systems, and
1887 fails with -1/"ENOSYS" everywhere else. If anybody knows how to
1888 influence pipe buffer size on other systems, drop me a note.
1889
1890 ($rfh, $wfh) = IO::AIO::pipe2 [$flags]
1891 This is a direct interface to the Linux pipe2(2) system call. If
1892 $flags is missing or 0, then this should be the same as a call to
1893 perl's built-in "pipe" function and create a new pipe, and works on
1894 systems that lack the pipe2 syscall. On win32, this case invokes
1895 "_pipe (..., 4096, O_BINARY)".
1896
1897 If $flags is non-zero, it tries to invoke the pipe2 system call with
1898 the given flags (Linux 2.6.27, glibc 2.9).
1899
1900 On success, the read and write file handles are returned.
1901
1902 On error, nothing will be returned. If the pipe2 syscall is missing
1903 and $flags is non-zero, fails with "ENOSYS".
1904
1905 Please refer to pipe2(2) for more info on the $flags, but at the
1906 time of this writing, "IO::AIO::O_CLOEXEC", "IO::AIO::O_NONBLOCK"
1907 and "IO::AIO::O_DIRECT" (Linux 3.4, for packet-based pipes) were
1908 supported.
1909
1910 Example: create a pipe race-free w.r.t. threads and fork:
1911
1912 my ($rfh, $wfh) = IO::AIO::pipe2 IO::AIO::O_CLOEXEC
1913 or die "pipe2: $!\n";
1914
1915 $fh = IO::AIO::eventfd [$initval, [$flags]]
1916 This is a direct interface to the Linux eventfd(2) system call. The
1917 (unhelpful) defaults for $initval and $flags are 0 for both.
1918
1919 On success, the new eventfd filehandle is returned, otherwise
1920 returns "undef". If the eventfd syscall is missing, fails with
1921 "ENOSYS".
1922
1923 Please refer to eventfd(2) for more info on this call.
1924
1925 The following symbol flag values are available:
1926 "IO::AIO::EFD_CLOEXEC", "IO::AIO::EFD_NONBLOCK" and
1927 "IO::AIO::EFD_SEMAPHORE" (Linux 2.6.30).
1928
1929 Example: create a new eventfd filehandle:
1930
1931 $fh = IO::AIO::eventfd 0, IO::AIO::O_CLOEXEC
1932 or die "eventfd: $!\n";
1933
1934 $fh = IO::AIO::timerfd_create $clockid[, $flags]
1935 This is a direct interface to the Linux timerfd_create(2) system
1936 call. The (unhelpful) default for $flags is 0.
1937
1938 On success, the new timerfd filehandle is returned, otherwise
1939 returns "undef". If the eventfd syscall is missing, fails with
1940 "ENOSYS".
1941
1942 Please refer to timerfd_create(2) for more info on this call.
1943
1944 The following $clockid values are available:
1945 "IO::AIO::CLOCK_REALTIME", "IO::AIO::CLOCK_MONOTONIC"
1946 "IO::AIO::CLOCK_CLOCK_BOOTTIME" (Linux 3.15)
1947 "IO::AIO::CLOCK_CLOCK_REALTIME_ALARM" (Linux 3.11) and
1948 "IO::AIO::CLOCK_CLOCK_BOOTTIME_ALARM" (Linux 3.11).
1949
1950 The following $flags values are available (Linux 2.6.27):
1951 "IO::AIO::TFD_NONBLOCK" and "IO::AIO::TFD_CLOEXEC".
1952
1953 Example: create a new timerfd and set it to one-second repeated
1954 alarms, then wait for two alarms:
1955
1956 my $fh = IO::AIO::timerfd_create IO::AIO::CLOCK_BOOTTIME, IO::AIO::TFD_CLOEXEC
1957 or die "timerfd_create: $!\n";
1958
1959 defined IO::AIO::timerfd_settime $fh, 0, 1, 1
1960 or die "timerfd_settime: $!\n";
1961
1962 for (1..2) {
1963 8 == sysread $fh, my $buf, 8
1964 or die "timerfd read failure\n";
1965
1966 printf "number of expirations (likely 1): %d\n",
1967 unpack "Q", $buf;
1968 }
1969
1970 ($cur_interval, $cur_value) = IO::AIO::timerfd_settime $fh, $flags,
1971 $new_interval, $nbw_value
1972 This is a direct interface to the Linux timerfd_settime(2) system
1973 call. Please refer to its manpage for more info on this call.
1974
1975 The new itimerspec is specified using two (possibly fractional)
1976 second values, $new_interval and $new_value).
1977
1978 On success, the current interval and value are returned (as per
1979 "timerfd_gettime"). On failure, the empty list is returned.
1980
1981 The following $flags values are available:
1982 "IO::AIO::TFD_TIMER_ABSTIME" and "IO::AIO::TFD_TIMER_CANCEL_ON_SET".
1983
1984 See "IO::AIO::timerfd_create" for a full example.
1985
1986 ($cur_interval, $cur_value) = IO::AIO::timerfd_gettime $fh
1987 This is a direct interface to the Linux timerfd_gettime(2) system
1988 call. Please refer to its manpage for more info on this call.
1989
1990 On success, returns the current values of interval and value for the
1991 given timerfd (as potentially fractional second values). On failure,
1992 the empty list is returned.
1993
1994EVENT LOOP INTEGRATION
1995 It is recommended to use AnyEvent::AIO to integrate IO::AIO
1996 automatically into many event loops:
1997
1998 # AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
1999 use AnyEvent::AIO;
2000
2001 You can also integrate IO::AIO manually into many event loops, here are
2002 some examples of how to do this:
2003
2004 # EV integration
2005 my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
2006
2007 # Event integration
2008 Event->io (fd => IO::AIO::poll_fileno,
2009 poll => 'r',
2010 cb => \&IO::AIO::poll_cb);
2011
2012 # Glib/Gtk2 integration
2013 add_watch Glib::IO IO::AIO::poll_fileno,
2014 in => sub { IO::AIO::poll_cb; 1 };
2015
2016 # Tk integration
2017 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
2018 readable => \&IO::AIO::poll_cb);
2019
2020 # Danga::Socket integration
2021 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
2022 \&IO::AIO::poll_cb);
2023
932 FORK BEHAVIOUR 2024 FORK BEHAVIOUR
933 This module should do "the right thing" when the process using it forks: 2025 Usage of pthreads in a program changes the semantics of fork
2026 considerably. Specifically, only async-safe functions can be called
2027 after fork. Perl doesn't know about this, so in general, you cannot call
2028 fork with defined behaviour in perl if pthreads are involved. IO::AIO
2029 uses pthreads, so this applies, but many other extensions and (for
2030 inexplicable reasons) perl itself often is linked against pthreads, so
2031 this limitation applies to quite a lot of perls.
934 2032
935 Before the fork, IO::AIO enters a quiescent state where no requests can 2033 This module no longer tries to fight your OS, or POSIX. That means
936 be added in other threads and no results will be processed. After the 2034 IO::AIO only works in the process that loaded it. Forking is fully
937 fork the parent simply leaves the quiescent state and continues 2035 supported, but using IO::AIO in the child is not.
938 request/result processing, while the child frees the request/result
939 queue (so that the requests started before the fork will only be handled
940 in the parent). Threads will be started on demand until the limit set in
941 the parent process has been reached again.
942 2036
943 In short: the parent will, after a short pause, continue as if fork had 2037 You might get around by not *using* IO::AIO before (or after) forking.
944 not been called, while the child will act as if IO::AIO has not been 2038 You could also try to call the IO::AIO::reinit function in the child:
945 used yet. 2039
2040 IO::AIO::reinit
2041 Abandons all current requests and I/O threads and simply
2042 reinitialises all data structures. This is not an operation
2043 supported by any standards, but happens to work on GNU/Linux and
2044 some newer BSD systems.
2045
2046 The only reasonable use for this function is to call it after
2047 forking, if "IO::AIO" was used in the parent. Calling it while
2048 IO::AIO is active in the process will result in undefined behaviour.
2049 Calling it at any time will also result in any undefined (by POSIX)
2050 behaviour.
2051
2052 LINUX-SPECIFIC CALLS
2053 When a call is documented as "linux-specific" then this means it
2054 originated on GNU/Linux. "IO::AIO" will usually try to autodetect the
2055 availability and compatibility of such calls regardless of the platform
2056 it is compiled on, so platforms such as FreeBSD which often implement
2057 these calls will work. When in doubt, call them and see if they fail wth
2058 "ENOSYS".
946 2059
947 MEMORY USAGE 2060 MEMORY USAGE
948 Per-request usage: 2061 Per-request usage:
949 2062
950 Each aio request uses - depending on your architecture - around 100-200 2063 Each aio request uses - depending on your architecture - around 100-200
… …
961 In the execution phase, some aio requests require more memory for 2074 In the execution phase, some aio requests require more memory for
962 temporary buffers, and each thread requires a stack and other data 2075 temporary buffers, and each thread requires a stack and other data
963 structures (usually around 16k-128k, depending on the OS). 2076 structures (usually around 16k-128k, depending on the OS).
964 2077
965KNOWN BUGS 2078KNOWN BUGS
966 Known bugs will be fixed in the next release. 2079 Known bugs will be fixed in the next release :)
2080
2081KNOWN ISSUES
2082 Calls that try to "import" foreign memory areas (such as "IO::AIO::mmap"
2083 or "IO::AIO::aio_slurp") do not work with generic lvalues, such as
2084 non-created hash slots or other scalars I didn't think of. It's best to
2085 avoid such and either use scalar variables or making sure that the
2086 scalar exists (e.g. by storing "undef") and isn't "funny" (e.g. tied).
2087
2088 I am not sure anything can be done about this, so this is considered a
2089 known issue, rather than a bug.
967 2090
968SEE ALSO 2091SEE ALSO
969 Coro::AIO. 2092 AnyEvent::AIO for easy integration into event loops, Coro::AIO for a
2093 more natural syntax.
970 2094
971AUTHOR 2095AUTHOR
972 Marc Lehmann <schmorp@schmorp.de> 2096 Marc Lehmann <schmorp@schmorp.de>
973 http://home.schmorp.de/ 2097 http://home.schmorp.de/
974 2098

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