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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) = @_; 8 my $fh = shift
9 or die "/etc/passwd: $!";
9 ... 10 ...
10 }; 11 };
11 12
12 aio_unlink "/tmp/file", sub { }; 13 aio_unlink "/tmp/file", sub { };
13 14
… …
23 $req->cancel; # cancel request if still in queue 24 $req->cancel; # cancel request if still in queue
24 25
25 my $grp = aio_group sub { print "all stats done\n" }; 26 my $grp = aio_group sub { print "all stats done\n" };
26 add $grp aio_stat "..." for ...; 27 add $grp aio_stat "..." for ...;
27 28
28 # AnyEvent integration
29 open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
30 my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
31
32 # Event integration
33 Event->io (fd => IO::AIO::poll_fileno,
34 poll => 'r',
35 cb => \&IO::AIO::poll_cb);
36
37 # Glib/Gtk2 integration
38 add_watch Glib::IO IO::AIO::poll_fileno,
39 in => sub { IO::AIO::poll_cb; 1 };
40
41 # Tk integration
42 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
43 readable => \&IO::AIO::poll_cb);
44
45 # Danga::Socket integration
46 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
47 \&IO::AIO::poll_cb);
48
49DESCRIPTION 29DESCRIPTION
50 This module implements asynchronous I/O using whatever means your 30 This module implements asynchronous I/O using whatever means your
51 operating system supports. 31 operating system supports. It is implemented as an interface to "libeio"
32 (<http://software.schmorp.de/pkg/libeio.html>).
33
34 Asynchronous means that operations that can normally block your program
35 (e.g. reading from disk) will be done asynchronously: the operation will
36 still block, but you can do something else in the meantime. This is
37 extremely useful for programs that need to stay interactive even when
38 doing heavy I/O (GUI programs, high performance network servers etc.),
39 but can also be used to easily do operations in parallel that are
40 normally done sequentially, e.g. stat'ing many files, which is much
41 faster on a RAID volume or over NFS when you do a number of stat
42 operations concurrently.
43
44 While most of this works on all types of file descriptors (for example
45 sockets), using these functions on file descriptors that support
46 nonblocking operation (again, sockets, pipes etc.) is very inefficient.
47 Use an event loop for that (such as the EV module): IO::AIO will
48 naturally fit into such an event loop itself.
52 49
53 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
54 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
55 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
56 perl. In the future, this module might make use of the native aio 53 perl. In the future, this module might make use of the native aio
57 functions available on many operating systems. However, they are often 54 functions available on many operating systems. However, they are often
58 not well-supported or restricted (Linux doesn't allow them on normal 55 not well-supported or restricted (GNU/Linux doesn't allow them on normal
59 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
60 aio_write, so the remaining functionality would have to be implemented 57 aio_write, so the remaining functionality would have to be implemented
61 using threads anyway. 58 using threads anyway.
62 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
63 Although the module will work with in the presence of other (Perl-) 64 Although the module will work in the presence of other (Perl-) threads,
64 threads, it is currently not reentrant in any way, so use appropriate 65 it is currently not reentrant in any way, so use appropriate locking
65 locking yourself, always call "poll_cb" from within the same thread, or 66 yourself, always call "poll_cb" from within the same thread, or never
66 never call "poll_cb" (or other "aio_" functions) recursively. 67 call "poll_cb" (or other "aio_" functions) recursively.
68
69 EXAMPLE
70 This is a simple example that uses the EV module and loads /etc/passwd
71 asynchronously:
72
73 use EV;
74 use IO::AIO;
75
76 # register the IO::AIO callback with EV
77 my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
78
79 # queue the request to open /etc/passwd
80 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
81 my $fh = shift
82 or die "error while opening: $!";
83
84 # stat'ing filehandles is generally non-blocking
85 my $size = -s $fh;
86
87 # queue a request to read the file
88 my $contents;
89 aio_read $fh, 0, $size, $contents, 0, sub {
90 $_[0] == $size
91 or die "short read: $!";
92
93 close $fh;
94
95 # file contents now in $contents
96 print $contents;
97
98 # exit event loop and program
99 EV::break;
100 };
101 };
102
103 # possibly queue up other requests, or open GUI windows,
104 # check for sockets etc. etc.
105
106 # process events as long as there are some:
107 EV::run;
67 108
68REQUEST ANATOMY AND LIFETIME 109REQUEST ANATOMY AND LIFETIME
69 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
70 not directly visible to Perl. 111 not directly visible to Perl.
71 112
… …
107 anymore (except possibly for the Perl object, but its connection to 148 anymore (except possibly for the Perl object, but its connection to
108 the actual aio request is severed and calling its methods will 149 the actual aio request is severed and calling its methods will
109 either do nothing or result in a runtime error). 150 either do nothing or result in a runtime error).
110 151
111FUNCTIONS 152FUNCTIONS
112 AIO FUNCTIONS 153 QUICK OVERVIEW
113 All the "aio_*" calls are more or less thin wrappers around the 154 This section simply lists the prototypes most of the functions for quick
114 syscall with the same name (sans "aio_"). The arguments are similar 155 reference. See the following sections for function-by-function
115 or identical, and they all accept an additional (and optional) 156 documentation.
116 $callback argument which must be a code reference. This code
117 reference will get called with the syscall return code (e.g. most
118 syscalls return -1 on error, unlike perl, which usually delivers
119 "false") as it's sole argument when the given syscall has been
120 executed asynchronously.
121 157
122 All functions expecting a filehandle keep a copy of the filehandle 158 aio_wd $pathname, $callback->($wd)
123 internally until the request has finished.
124
125 All requests return objects of type IO::AIO::REQ that allow further
126 manipulation of those requests while they are in-flight.
127
128 The pathnames you pass to these routines *must* be absolute and
129 encoded in byte form. The reason for the former is that at the time
130 the request is being executed, the current working directory could
131 have changed. Alternatively, you can make sure that you never change
132 the current working directory.
133
134 To encode pathnames to byte form, either make sure you either: a)
135 always pass in filenames you got from outside (command line, readdir
136 etc.), b) are ASCII or ISO 8859-1, c) use the Encode module and
137 encode your pathnames to the locale (or other) encoding in effect in
138 the user environment, d) use Glib::filename_from_unicode on unicode
139 filenames or e) use something else.
140
141 $prev_pri = aioreq_pri [$pri]
142 Returns the priority value that would be used for the next
143 request and, if $pri is given, sets the priority for the next
144 aio request.
145
146 The default priority is 0, the minimum and maximum priorities
147 are -4 and 4, respectively. Requests with higher priority will
148 be serviced first.
149
150 The priority will be reset to 0 after each call to one of the
151 "aio_*" functions.
152
153 Example: open a file with low priority, then read something from
154 it with higher priority so the read request is serviced before
155 other low priority open requests (potentially spamming the
156 cache):
157
158 aioreq_pri -3;
159 aio_open ..., sub {
160 return unless $_[0];
161
162 aioreq_pri -2;
163 aio_read $_[0], ..., sub {
164 ...
165 };
166 };
167
168 aioreq_nice $pri_adjust
169 Similar to "aioreq_pri", but subtracts the given value from the
170 current priority, so effects are cumulative.
171
172 aio_open $pathname, $flags, $mode, $callback->($fh) 159 aio_open $pathname, $flags, $mode, $callback->($fh)
173 Asynchronously open or create a file and call the callback with
174 a newly created filehandle for the file.
175
176 The pathname passed to "aio_open" must be absolute. See API
177 NOTES, above, for an explanation.
178
179 The $flags argument is a bitmask. See the "Fcntl" module for a
180 list. They are the same as used by "sysopen".
181
182 Likewise, $mode specifies the mode of the newly created file, if
183 it didn't exist and "O_CREAT" has been given, just like perl's
184 "sysopen", except that it is mandatory (i.e. use 0 if you don't
185 create new files, and 0666 or 0777 if you do).
186
187 Example:
188
189 aio_open "/etc/passwd", O_RDONLY, 0, sub {
190 if ($_[0]) {
191 print "open successful, fh is $_[0]\n";
192 ...
193 } else {
194 die "open failed: $!\n";
195 }
196 };
197
198 aio_close $fh, $callback->($status) 160 aio_close $fh, $callback->($status)
199 Asynchronously close a file and call the callback with the 161 aio_seek $fh,$offset,$whence, $callback->($offs)
200 result code. *WARNING:* although accepted, you should not pass
201 in a perl filehandle here, as perl will likely close the file
202 descriptor another time when the filehandle is destroyed.
203 Normally, you can safely call perls "close" or just let
204 filehandles go out of scope.
205
206 This is supposed to be a bug in the API, so that might change.
207 It's therefore best to avoid this function.
208
209 aio_read $fh,$offset,$length, $data,$dataoffset, 162 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
210 $callback->($retval)
211 aio_write $fh,$offset,$length, $data,$dataoffset, 163 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
212 $callback->($retval)
213 Reads or writes "length" bytes from the specified "fh" and
214 "offset" into the scalar given by "data" and offset "dataoffset"
215 and calls the callback without the actual number of bytes read
216 (or -1 on error, just like the syscall).
217
218 The $data scalar *MUST NOT* be modified in any way while the
219 request is outstanding. Modifying it can result in segfaults or
220 WW3 (if the necessary/optional hardware is installed).
221
222 Example: Read 15 bytes at offset 7 into scalar $buffer, starting
223 at offset 0 within the scalar:
224
225 aio_read $fh, 7, 15, $buffer, 0, sub {
226 $_[0] > 0 or die "read error: $!";
227 print "read $_[0] bytes: <$buffer>\n";
228 };
229
230 aio_move $srcpath, $dstpath, $callback->($status)
231 Try to move the *file* (directories not supported as either
232 source or destination) from $srcpath to $dstpath and call the
233 callback with the 0 (error) or -1 ok.
234
235 This is a composite request that tries to rename(2) the file
236 first. If rename files with "EXDEV", it creates the destination
237 file with mode 0200 and copies the contents of the source file
238 into it using "aio_sendfile", followed by restoring atime,
239 mtime, access mode and uid/gid, in that order, and unlinking the
240 $srcpath.
241
242 If an error occurs, the partial destination file will be
243 unlinked, if possible, except when setting atime, mtime, access
244 mode and uid/gid, where errors are being ignored.
245
246 aio_sendfile $out_fh, $in_fh, $in_offset, $length, 164 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
247 $callback->($retval)
248 Tries to copy $length bytes from $in_fh to $out_fh. It starts
249 reading at byte offset $in_offset, and starts writing at the
250 current file offset of $out_fh. Because of that, it is not safe
251 to issue more than one "aio_sendfile" per $out_fh, as they will
252 interfere with each other.
253
254 This call tries to make use of a native "sendfile" syscall to
255 provide zero-copy operation. For this to work, $out_fh should
256 refer to a socket, and $in_fh should refer to mmap'able file.
257
258 If the native sendfile call fails or is not implemented, it will
259 be emulated, so you can call "aio_sendfile" on any type of
260 filehandle regardless of the limitations of the operating
261 system.
262
263 Please note, however, that "aio_sendfile" can read more bytes
264 from $in_fh than are written, and there is no way to find out
265 how many bytes have been read from "aio_sendfile" alone, as
266 "aio_sendfile" only provides the number of bytes written to
267 $out_fh. Only if the result value equals $length one can assume
268 that $length bytes have been read.
269
270 aio_readahead $fh,$offset,$length, $callback->($retval) 165 aio_readahead $fh,$offset,$length, $callback->($retval)
271 "aio_readahead" populates the page cache with data from a file
272 so that subsequent reads from that file will not block on disk
273 I/O. The $offset argument specifies the starting point from
274 which data is to be read and $length specifies the number of
275 bytes to be read. I/O is performed in whole pages, so that
276 offset is effectively rounded down to a page boundary and bytes
277 are read up to the next page boundary greater than or equal to
278 (off-set+length). "aio_readahead" does not read beyond the end
279 of the file. The current file offset of the file is left
280 unchanged.
281
282 If that syscall doesn't exist (likely if your OS isn't Linux) it
283 will be emulated by simply reading the data, which would have a
284 similar effect.
285
286 aio_stat $fh_or_path, $callback->($status) 166 aio_stat $fh_or_path, $callback->($status)
287 aio_lstat $fh, $callback->($status) 167 aio_lstat $fh, $callback->($status)
288 Works like perl's "stat" or "lstat" in void context. The 168 aio_statvfs $fh_or_path, $callback->($statvfs)
289 callback will be called after the stat and the results will be 169 aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
290 available using "stat _" or "-s _" etc... 170 aio_chown $fh_or_path, $uid, $gid, $callback->($status)
291 171 aio_chmod $fh_or_path, $mode, $callback->($status)
292 The pathname passed to "aio_stat" must be absolute. See API 172 aio_truncate $fh_or_path, $offset, $callback->($status)
293 NOTES, above, for an explanation. 173 aio_allocate $fh, $mode, $offset, $len, $callback->($status)
294 174 aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
295 Currently, the stats are always 64-bit-stats, i.e. instead of
296 returning an error when stat'ing a large file, the results will
297 be silently truncated unless perl itself is compiled with large
298 file support.
299
300 Example: Print the length of /etc/passwd:
301
302 aio_stat "/etc/passwd", sub {
303 $_[0] and die "stat failed: $!";
304 print "size is ", -s _, "\n";
305 };
306
307 aio_unlink $pathname, $callback->($status) 175 aio_unlink $pathname, $callback->($status)
308 Asynchronously unlink (delete) a file and call the callback with 176 aio_mknod $pathname, $mode, $dev, $callback->($status)
309 the result code.
310
311 aio_link $srcpath, $dstpath, $callback->($status) 177 aio_link $srcpath, $dstpath, $callback->($status)
312 Asynchronously create a new link to the existing object at
313 $srcpath at the path $dstpath and call the callback with the
314 result code.
315
316 aio_symlink $srcpath, $dstpath, $callback->($status) 178 aio_symlink $srcpath, $dstpath, $callback->($status)
317 Asynchronously create a new symbolic link to the existing object 179 aio_readlink $pathname, $callback->($link)
318 at $srcpath at the path $dstpath and call the callback with the 180 aio_realpath $pathname, $callback->($path)
319 result code.
320
321 aio_rename $srcpath, $dstpath, $callback->($status) 181 aio_rename $srcpath, $dstpath, $callback->($status)
322 Asynchronously rename the object at $srcpath to $dstpath, just 182 aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
323 as rename(2) and call the callback with the result code. 183 aio_mkdir $pathname, $mode, $callback->($status)
324
325 aio_rmdir $pathname, $callback->($status) 184 aio_rmdir $pathname, $callback->($status)
326 Asynchronously rmdir (delete) a directory and call the callback
327 with the result code.
328
329 aio_readdir $pathname, $callback->($entries) 185 aio_readdir $pathname, $callback->($entries)
330 Unlike the POSIX call of the same name, "aio_readdir" reads an 186 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
331 entire directory (i.e. opendir + readdir + closedir). The 187 IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
332 entries will not be sorted, and will NOT include the "." and 188 IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
333 ".." entries.
334
335 The callback a single argument which is either "undef" or an
336 array-ref with the filenames.
337
338 aio_scandir $path, $maxreq, $callback->($dirs, $nondirs) 189 aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
339 Scans a directory (similar to "aio_readdir") but additionally 190 aio_load $pathname, $data, $callback->($status)
340 tries to efficiently separate the entries of directory $path 191 aio_copy $srcpath, $dstpath, $callback->($status)
341 into two sets of names, directories you can recurse into 192 aio_move $srcpath, $dstpath, $callback->($status)
342 (directories), and ones you cannot recurse into (everything 193 aio_rmtree $pathname, $callback->($status)
343 else, including symlinks to directories). 194 aio_fcntl $fh, $cmd, $arg, $callback->($status)
344 195 aio_ioctl $fh, $request, $buf, $callback->($status)
345 "aio_scandir" is a composite request that creates of many sub 196 aio_sync $callback->($status)
346 requests_ $maxreq specifies the maximum number of outstanding 197 aio_syncfs $fh, $callback->($status)
347 aio requests that this function generates. If it is "<= 0", then
348 a suitable default will be chosen (currently 6).
349
350 On error, the callback is called without arguments, otherwise it
351 receives two array-refs with path-relative entry names.
352
353 Example:
354
355 aio_scandir $dir, 0, sub {
356 my ($dirs, $nondirs) = @_;
357 print "real directories: @$dirs\n";
358 print "everything else: @$nondirs\n";
359 };
360
361 Implementation notes.
362
363 The "aio_readdir" cannot be avoided, but "stat()"'ing every
364 entry can.
365
366 After reading the directory, the modification time, size etc. of
367 the directory before and after the readdir is checked, and if
368 they match (and isn't the current time), the link count will be
369 used to decide how many entries are directories (if >= 2).
370 Otherwise, no knowledge of the number of subdirectories will be
371 assumed.
372
373 Then entries will be sorted into likely directories (everything
374 without a non-initial dot currently) and likely non-directories
375 (everything else). Then every entry plus an appended "/." will
376 be "stat"'ed, likely directories first. If that succeeds, it
377 assumes that the entry is a directory or a symlink to directory
378 (which will be checked seperately). This is often faster than
379 stat'ing the entry itself because filesystems might detect the
380 type of the entry without reading the inode data (e.g. ext2fs
381 filetype feature).
382
383 If the known number of directories (link count - 2) has been
384 reached, the rest of the entries is assumed to be
385 non-directories.
386
387 This only works with certainty on POSIX (= UNIX) filesystems,
388 which fortunately are the vast majority of filesystems around.
389
390 It will also likely work on non-POSIX filesystems with reduced
391 efficiency as those tend to return 0 or 1 as link counts, which
392 disables the directory counting heuristic.
393
394 aio_fsync $fh, $callback->($status) 198 aio_fsync $fh, $callback->($status)
395 Asynchronously call fsync on the given filehandle and call the
396 callback with the fsync result code.
397
398 aio_fdatasync $fh, $callback->($status) 199 aio_fdatasync $fh, $callback->($status)
399 Asynchronously call fdatasync on the given filehandle and call 200 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
400 the callback with the fdatasync result code. 201 aio_pathsync $pathname, $callback->($status)
401 202 aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
402 If this call isn't available because your OS lacks it or it 203 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
403 couldn't be detected, it will be emulated by calling "fsync" 204 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
404 instead. 205 aio_mlockall $flags, $callback->($status)
405
406 aio_group $callback->(...) 206 aio_group $callback->(...)
407 This is a very special aio request: Instead of doing something,
408 it is a container for other aio requests, which is useful if you
409 want to bundle many requests into a single, composite, request
410 with a definite callback and the ability to cancel the whole
411 request with its subrequests.
412
413 Returns an object of class IO::AIO::GRP. See its documentation
414 below for more info.
415
416 Example:
417
418 my $grp = aio_group sub {
419 print "all stats done\n";
420 };
421
422 add $grp
423 (aio_stat ...),
424 (aio_stat ...),
425 ...;
426
427 aio_nop $callback->() 207 aio_nop $callback->()
428 This is a special request - it does nothing in itself and is
429 only used for side effects, such as when you want to add a dummy
430 request to a group so that finishing the requests in the group
431 depends on executing the given code.
432 208
433 While this request does nothing, it still goes through the 209 $prev_pri = aioreq_pri [$pri]
434 execution phase and still requires a worker thread. Thus, the 210 aioreq_nice $pri_adjust
435 callback will not be executed immediately but only after other
436 requests in the queue have entered their execution phase. This
437 can be used to measure request latency.
438 211
439 IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED* 212 IO::AIO::poll_wait
440 Mainly used for debugging and benchmarking, this aio request 213 IO::AIO::poll_cb
441 puts one of the request workers to sleep for the given time. 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]
442 228
443 While it is theoretically handy to have simple I/O scheduling 229 IO::AIO::sendfile $ofh, $ifh, $offset, $count
444 requests like sleep and file handle readable/writable, the 230 IO::AIO::fadvise $fh, $offset, $len, $advice
445 overhead this creates is immense (it blocks a thread for a long 231 IO::AIO::mmap $scalar, $length, $prot, $flags[, $fh[, $offset]]
446 time) so do not use this function except to put your application 232 IO::AIO::munmap $scalar
447 under artificial I/O pressure. 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
448 238
449 IO::AIO::REQ CLASS 239 API NOTES
450 All non-aggregate "aio_*" functions return an object of this class 240 All the "aio_*" calls are more or less thin wrappers around the syscall
451 when called in non-void context. 241 with the same name (sans "aio_"). The arguments are similar or
242 identical, and they all accept an additional (and optional) $callback
243 argument which must be a code reference. This code reference will be
244 called after the syscall has been executed in an asynchronous fashion.
245 The results of the request will be passed as arguments to the callback
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").
452 249
453 cancel $req 250 Some requests (such as "aio_readdir") pass the actual results and
454 Cancels the request, if possible. Has the effect of skipping 251 communicate failures by passing "undef".
455 execution when entering the execute state and skipping calling
456 the callback when entering the the result state, but will leave
457 the request otherwise untouched. That means that requests that
458 currently execute will not be stopped and resources held by the
459 request will not be freed prematurely.
460 252
461 cb $req $callback->(...) 253 All functions expecting a filehandle keep a copy of the filehandle
462 Replace (or simply set) the callback registered to the request. 254 internally until the request has finished.
463 255
464 IO::AIO::GRP CLASS 256 All functions return request objects of type IO::AIO::REQ that allow
465 This class is a subclass of IO::AIO::REQ, so all its methods apply 257 further manipulation of those requests while they are in-flight.
466 to objects of this class, too.
467 258
468 A IO::AIO::GRP object is a special request that can contain multiple 259 The pathnames you pass to these routines *should* be absolute. The
469 other aio requests. 260 reason for this is that at the time the request is being executed, the
261 current working directory could have changed. Alternatively, you can
262 make sure that you never change the current working directory anywhere
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.
470 267
471 You create one by calling the "aio_group" constructing function with 268 To encode pathnames as octets, either make sure you either: a) always
472 a callback that will be called when all contained requests have 269 pass in filenames you got from outside (command line, readdir etc.)
473 entered the "done" state: 270 without tinkering, b) are in your native filesystem encoding, c) use the
271 Encode module and encode your pathnames to the locale (or other)
272 encoding in effect in the user environment, d) use
273 Glib::filename_from_unicode on unicode filenames or e) use something
274 else to ensure your scalar has the correct contents.
474 275
475 my $grp = aio_group sub { 276 This works, btw. independent of the internal UTF-8 bit, which IO::AIO
476 print "all requests are done\n"; 277 handles correctly whether it is set or not.
477 };
478 278
479 You add requests by calling the "add" method with one or more 279 AIO REQUEST FUNCTIONS
480 "IO::AIO::REQ" objects: 280 $prev_pri = aioreq_pri [$pri]
281 Returns the priority value that would be used for the next request
282 and, if $pri is given, sets the priority for the next aio request.
481 283
482 $grp->add (aio_unlink "..."); 284 The default priority is 0, the minimum and maximum priorities are -4
285 and 4, respectively. Requests with higher priority will be serviced
286 first.
483 287
484 add $grp aio_stat "...", sub { 288 The priority will be reset to 0 after each call to one of the
485 $_[0] or return $grp->result ("error"); 289 "aio_*" functions.
486 290
487 # add another request dynamically, if first succeeded 291 Example: open a file with low priority, then read something from it
292 with higher priority so the read request is serviced before other
293 low priority open requests (potentially spamming the cache):
294
295 aioreq_pri -3;
488 add $grp aio_open "...", sub { 296 aio_open ..., sub {
489 $grp->result ("ok"); 297 return unless $_[0];
298
299 aioreq_pri -2;
300 aio_read $_[0], ..., sub {
301 ...
490 }; 302 };
491 }; 303 };
492 304
305 aioreq_nice $pri_adjust
306 Similar to "aioreq_pri", but subtracts the given value from the
307 current priority, so the effect is cumulative.
308
309 aio_open $pathname, $flags, $mode, $callback->($fh)
310 Asynchronously open or create a file and call the callback with a
311 newly created filehandle for the file (or "undef" in case of an
312 error).
313
314 The pathname passed to "aio_open" must be absolute. See API NOTES,
315 above, for an explanation.
316
317 The $flags argument is a bitmask. See the "Fcntl" module for a list.
318 They are the same as used by "sysopen".
319
320 Likewise, $mode specifies the mode of the newly created file, if it
321 didn't exist and "O_CREAT" has been given, just like perl's
322 "sysopen", except that it is mandatory (i.e. use 0 if you don't
323 create new files, and 0666 or 0777 if you do). Note that the $mode
324 will be modified by the umask in effect then the request is being
325 executed, so better never change the umask.
326
327 Example:
328
329 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
330 if ($_[0]) {
331 print "open successful, fh is $_[0]\n";
332 ...
333 } else {
334 die "open failed: $!\n";
335 }
336 };
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
348 aio_close $fh, $callback->($status)
349 Asynchronously close a file and call the callback with the result
350 code.
351
352 Unfortunately, you can't do this to perl. Perl *insists* very
353 strongly on closing the file descriptor associated with the
354 filehandle itself.
355
356 Therefore, "aio_close" will not close the filehandle - instead it
357 will use dup2 to overwrite the file descriptor with the write-end of
358 a pipe (the pipe fd will be created on demand and will be cached).
359
360 Or in other words: the file descriptor will be closed, but it will
361 not be free for reuse until the perl filehandle is closed.
362
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").
368
369 The resulting absolute offset will be passed to the callback, or -1
370 in case of an error.
371
372 In theory, the $whence constants could be different than the
373 corresponding values from Fcntl, but perl guarantees they are the
374 same, so don't panic.
375
376 As a GNU/Linux (and maybe Solaris) extension, also the constants
377 "IO::AIO::SEEK_DATA" and "IO::AIO::SEEK_HOLE" are available, if they
378 could be found. No guarantees about suitability for use in
379 "aio_seek" or Perl's "sysseek" can be made though, although I would
380 naively assume they "just work".
381
382 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
383 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
384 Reads or writes $length bytes from or to the specified $fh and
385 $offset into the scalar given by $data and offset $dataoffset and
386 calls the callback with the actual number of bytes transferred (or
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.
391
392 If $offset is undefined, then the current file descriptor offset
393 will be used (and updated), otherwise the file descriptor offset
394 will not be changed by these calls.
395
396 If $length is undefined in "aio_write", use the remaining length of
397 $data.
398
399 If $dataoffset is less than zero, it will be counted from the end of
400 $data.
401
402 The $data scalar *MUST NOT* be modified in any way while the request
403 is outstanding. Modifying it can result in segfaults or World War
404 III (if the necessary/optional hardware is installed).
405
406 Example: Read 15 bytes at offset 7 into scalar $buffer, starting at
407 offset 0 within the scalar:
408
409 aio_read $fh, 7, 15, $buffer, 0, sub {
410 $_[0] > 0 or die "read error: $!";
411 print "read $_[0] bytes: <$buffer>\n";
412 };
413
414 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
415 Tries to copy $length bytes from $in_fh to $out_fh. It starts
416 reading at byte offset $in_offset, and starts writing at the current
417 file offset of $out_fh. Because of that, it is not safe to issue
418 more than one "aio_sendfile" per $out_fh, as they will interfere
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.
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
439 This call tries to make use of a native "sendfile"-like syscall to
440 provide zero-copy operation. For this to work, $out_fh should refer
441 to a socket, and $in_fh should refer to an mmap'able file.
442
443 If a native sendfile cannot be found or it fails with "ENOSYS",
444 "EINVAL", "ENOTSUP", "EOPNOTSUPP", "EAFNOSUPPORT", "EPROTOTYPE" or
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.
448
449 As native sendfile syscalls (as practically any non-POSIX interface
450 hacked together in a hurry to improve benchmark numbers) tend to be
451 rather buggy on many systems, this implementation tries to work
452 around some known bugs in Linux and FreeBSD kernels (probably
453 others, too), but that might fail, so you really really should check
454 the return value of "aio_sendfile" - fewer bytes than expected might
455 have been transferred.
456
457 aio_readahead $fh,$offset,$length, $callback->($retval)
458 "aio_readahead" populates the page cache with data from a file so
459 that subsequent reads from that file will not block on disk I/O. The
460 $offset argument specifies the starting point from which data is to
461 be read and $length specifies the number of bytes to be read. I/O is
462 performed in whole pages, so that offset is effectively rounded down
463 to a page boundary and bytes are read up to the next page boundary
464 greater than or equal to (off-set+length). "aio_readahead" does not
465 read beyond the end of the file. The current file offset of the file
466 is left unchanged.
467
468 If that syscall doesn't exist (likely if your kernel isn't Linux) it
469 will be emulated by simply reading the data, which would have a
470 similar effect.
471
472 aio_stat $fh_or_path, $callback->($status)
473 aio_lstat $fh, $callback->($status)
474 Works almost exactly like perl's "stat" or "lstat" in void context.
475 The callback will be called after the stat and the results will be
476 available using "stat _" or "-s _" and other tests (with the
477 exception of "-B" and "-T").
478
479 The pathname passed to "aio_stat" must be absolute. See API NOTES,
480 above, for an explanation.
481
482 Currently, the stats are always 64-bit-stats, i.e. instead of
483 returning an error when stat'ing a large file, the results will be
484 silently truncated unless perl itself is compiled with large file
485 support.
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
499 Example: Print the length of /etc/passwd:
500
501 aio_stat "/etc/passwd", sub {
502 $_[0] and die "stat failed: $!";
503 print "size is ", -s _, "\n";
504 };
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
549 aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
550 Works like perl's "utime" function (including the special case of
551 $atime and $mtime being undef). Fractional times are supported if
552 the underlying syscalls support them.
553
554 When called with a pathname, uses utimensat(2) or utimes(2) if
555 available, otherwise utime(2). If called on a file descriptor, uses
556 futimens(2) or futimes(2) if available, otherwise returns ENOSYS, so
557 this is not portable.
558
559 Examples:
560
561 # set atime and mtime to current time (basically touch(1)):
562 aio_utime "path", undef, undef;
563 # set atime to current time and mtime to beginning of the epoch:
564 aio_utime "path", time, undef; # undef==0
565
566 aio_chown $fh_or_path, $uid, $gid, $callback->($status)
567 Works like perl's "chown" function, except that "undef" for either
568 $uid or $gid is being interpreted as "do not change" (but -1 can
569 also be used).
570
571 Examples:
572
573 # same as "chown root path" in the shell:
574 aio_chown "path", 0, -1;
575 # same as above:
576 aio_chown "path", 0, undef;
577
578 aio_truncate $fh_or_path, $offset, $callback->($status)
579 Works like truncate(2) or ftruncate(2).
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
602 aio_chmod $fh_or_path, $mode, $callback->($status)
603 Works like perl's "chmod" function.
604
605 aio_unlink $pathname, $callback->($status)
606 Asynchronously unlink (delete) a file and call the callback with the
607 result code.
608
609 aio_mknod $pathname, $mode, $dev, $callback->($status)
610 [EXPERIMENTAL]
611
612 Asynchronously create a device node (or fifo). See mknod(2).
613
614 The only (POSIX-) portable way of calling this function is:
615
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.
620
621 aio_link $srcpath, $dstpath, $callback->($status)
622 Asynchronously create a new link to the existing object at $srcpath
623 at the path $dstpath and call the callback with the result code.
624
625 aio_symlink $srcpath, $dstpath, $callback->($status)
626 Asynchronously create a new symbolic link to the existing object at
627 $srcpath at the path $dstpath and call the callback with the result
628 code.
629
630 aio_readlink $pathname, $callback->($link)
631 Asynchronously read the symlink specified by $path and pass it to
632 the callback. If an error occurs, nothing or undef gets passed to
633 the callback.
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
643 aio_rename $srcpath, $dstpath, $callback->($status)
644 Asynchronously rename the object at $srcpath to $dstpath, just as
645 rename(2) and call the callback with the result code.
646
647 On systems that support the AIO::WD working directory abstraction
648 natively, the case "[$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".
665
666 aio_mkdir $pathname, $mode, $callback->($status)
667 Asynchronously mkdir (create) a directory and call the callback with
668 the result code. $mode will be modified by the umask at the time the
669 request is executed, so do not change your umask.
670
671 aio_rmdir $pathname, $callback->($status)
672 Asynchronously rmdir (delete) a directory and call the callback with
673 the result code.
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
679 aio_readdir $pathname, $callback->($entries)
680 Unlike the POSIX call of the same name, "aio_readdir" reads an
681 entire directory (i.e. opendir + readdir + closedir). The entries
682 will not be sorted, and will NOT include the "." and ".." entries.
683
684 The callback is passed a single argument which is either "undef" or
685 an array-ref with the filenames.
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
777 aio_load $pathname, $data, $callback->($status)
778 This is a composite request that tries to fully load the given file
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.
783
784 aio_copy $srcpath, $dstpath, $callback->($status)
785 Try to copy the *file* (directories not supported as either source
786 or destination) from $srcpath to $dstpath and call the callback with
787 a status of 0 (ok) or -1 (error, see $!).
788
789 Existing destination files will be truncated.
790
791 This is a composite request that creates the destination file with
792 mode 0200 and copies the contents of the source file into it using
793 "aio_sendfile", followed by restoring atime, mtime, access mode and
794 uid/gid, in that order.
795
796 If an error occurs, the partial destination file will be unlinked,
797 if possible, except when setting atime, mtime, access mode and
798 uid/gid, where errors are being ignored.
799
800 aio_move $srcpath, $dstpath, $callback->($status)
801 Try to move the *file* (directories not supported as either source
802 or destination) from $srcpath to $dstpath and call the callback with
803 a status of 0 (ok) or -1 (error, see $!).
804
805 This is a composite request that tries to rename(2) the file first;
806 if rename fails with "EXDEV", it copies the file with "aio_copy"
807 and, if that is successful, unlinks the $srcpath.
808
809 aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
810 Scans a directory (similar to "aio_readdir") but additionally tries
811 to efficiently separate the entries of directory $path into two sets
812 of names, directories you can recurse into (directories), and ones
813 you cannot recurse into (everything else, including symlinks to
814 directories).
815
816 "aio_scandir" is a composite request that generates many sub
817 requests. $maxreq specifies the maximum number of outstanding aio
818 requests that this function generates. If it is "<= 0", then a
819 suitable default will be chosen (currently 4).
820
821 On error, the callback is called without arguments, otherwise it
822 receives two array-refs with path-relative entry names.
823
824 Example:
825
826 aio_scandir $dir, 0, sub {
827 my ($dirs, $nondirs) = @_;
828 print "real directories: @$dirs\n";
829 print "everything else: @$nondirs\n";
830 };
831
832 Implementation notes.
833
834 The "aio_readdir" cannot be avoided, but "stat()"'ing every entry
835 can.
836
837 If readdir returns file type information, then this is used directly
838 to find directories.
839
840 Otherwise, after reading the directory, the modification time, size
841 etc. of the directory before and after the readdir is checked, and
842 if they match (and isn't the current time), the link count will be
843 used to decide how many entries are directories (if >= 2).
844 Otherwise, no knowledge of the number of subdirectories will be
845 assumed.
846
847 Then entries will be sorted into likely directories a non-initial
848 dot currently) and likely non-directories (see "aio_readdirx"). Then
849 every entry plus an appended "/." will be "stat"'ed, likely
850 directories first, in order of their inode numbers. If that
851 succeeds, it assumes that the entry is a directory or a symlink to
852 directory (which will be checked separately). This is often faster
853 than stat'ing the entry itself because filesystems might detect the
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.
857
858 If the known number of directories (link count - 2) has been
859 reached, the rest of the entries is assumed to be non-directories.
860
861 This only works with certainty on POSIX (= UNIX) filesystems, which
862 fortunately are the vast majority of filesystems around.
863
864 It will also likely work on non-POSIX filesystems with reduced
865 efficiency as those tend to return 0 or 1 as link counts, which
866 disables the directory counting heuristic.
867
868 aio_rmtree $pathname, $callback->($status)
869 Delete a directory tree starting (and including) $path, return the
870 status of the final "rmdir" only. This is a composite request that
871 uses "aio_scandir" to recurse into and rmdir directories, and unlink
872 everything else.
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
922 aio_sync $callback->($status)
923 Asynchronously call sync and call the callback when finished.
924
925 aio_fsync $fh, $callback->($status)
926 Asynchronously call fsync on the given filehandle and call the
927 callback with the fsync result code.
928
929 aio_fdatasync $fh, $callback->($status)
930 Asynchronously call fdatasync on the given filehandle and call the
931 callback with the fdatasync result code.
932
933 If this call isn't available because your OS lacks it or it couldn't
934 be detected, it will be emulated by calling "fsync" instead.
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
954 aio_pathsync $pathname, $callback->($status)
955 This request tries to open, fsync and close the given path. This is
956 a composite request intended to sync directories after directory
957 operations (E.g. rename). This might not work on all operating
958 systems or have any specific effect, but usually it makes sure that
959 directory changes get written to disc. It works for anything that
960 can be opened for read-only, not just directories.
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
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".
1081
1082 aio_group $callback->(...)
1083 This is a very special aio request: Instead of doing something, it
1084 is a container for other aio requests, which is useful if you want
1085 to bundle many requests into a single, composite, request with a
1086 definite callback and the ability to cancel the whole request with
1087 its subrequests.
1088
1089 Returns an object of class IO::AIO::GRP. See its documentation below
1090 for more info.
1091
1092 Example:
1093
1094 my $grp = aio_group sub {
1095 print "all stats done\n";
1096 };
1097
1098 add $grp
1099 (aio_stat ...),
1100 (aio_stat ...),
1101 ...;
1102
1103 aio_nop $callback->()
1104 This is a special request - it does nothing in itself and is only
1105 used for side effects, such as when you want to add a dummy request
1106 to a group so that finishing the requests in the group depends on
1107 executing the given code.
1108
1109 While this request does nothing, it still goes through the execution
1110 phase and still requires a worker thread. Thus, the callback will
1111 not be executed immediately but only after other requests in the
1112 queue have entered their execution phase. This can be used to
1113 measure request latency.
1114
1115 IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
1116 Mainly used for debugging and benchmarking, this aio request puts
1117 one of the request workers to sleep for the given time.
1118
1119 While it is theoretically handy to have simple I/O scheduling
1120 requests like sleep and file handle readable/writable, the overhead
1121 this creates is immense (it blocks a thread for a long time) so do
1122 not use this function except to put your application under
1123 artificial I/O pressure.
1124
1125 IO::AIO::WD - multiple working directories
1126 Your process only has one current working directory, which is used by
1127 all threads. This makes it hard to use relative paths (some other
1128 component could call "chdir" at any time, and it is hard to control when
1129 the path will be used by IO::AIO).
1130
1131 One solution for this is to always use absolute paths. This usually
1132 works, but can be quite slow (the kernel has to walk the whole path on
1133 every access), and can also be a hassle to implement.
1134
1135 Newer POSIX systems have a number of functions (openat, fdopendir,
1136 futimensat and so on) that make it possible to specify working
1137 directories per operation.
1138
1139 For portability, and because the clowns who "designed", or shall I
1140 write, perpetrated this new interface were obviously half-drunk, this
1141 abstraction cannot be perfect, though.
1142
1143 IO::AIO allows you to convert directory paths into a so-called
1144 IO::AIO::WD object. This object stores the canonicalised, absolute
1145 version of the path, and on systems that allow it, also a directory file
1146 descriptor.
1147
1148 Everywhere where a pathname is accepted by IO::AIO (e.g. in "aio_stat"
1149 or "aio_unlink"), one can specify an array reference with an IO::AIO::WD
1150 object and a pathname instead (or the IO::AIO::WD object alone, which
1151 gets interpreted as "[$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
1243 IO::AIO::REQ CLASS
1244 All non-aggregate "aio_*" functions return an object of this class when
1245 called in non-void context.
1246
1247 cancel $req
1248 Cancels the request, if possible. Has the effect of skipping
1249 execution when entering the execute state and skipping calling the
1250 callback when entering the the result state, but will leave the
1251 request otherwise untouched (with the exception of readdir). That
1252 means that requests that currently execute will not be stopped and
1253 resources held by the request will not be freed prematurely.
1254
1255 cb $req $callback->(...)
1256 Replace (or simply set) the callback registered to the request.
1257
1258 IO::AIO::GRP CLASS
1259 This class is a subclass of IO::AIO::REQ, so all its methods apply to
1260 objects of this class, too.
1261
1262 A IO::AIO::GRP object is a special request that can contain multiple
1263 other aio requests.
1264
1265 You create one by calling the "aio_group" constructing function with a
1266 callback that will be called when all contained requests have entered
1267 the "done" state:
1268
1269 my $grp = aio_group sub {
1270 print "all requests are done\n";
1271 };
1272
1273 You add requests by calling the "add" method with one or more
1274 "IO::AIO::REQ" objects:
1275
1276 $grp->add (aio_unlink "...");
1277
1278 add $grp aio_stat "...", sub {
1279 $_[0] or return $grp->result ("error");
1280
1281 # add another request dynamically, if first succeeded
1282 add $grp aio_open "...", sub {
1283 $grp->result ("ok");
1284 };
1285 };
1286
493 This makes it very easy to create composite requests (see the source 1287 This makes it very easy to create composite requests (see the source of
494 of "aio_move" for an application) that work and feel like simple 1288 "aio_move" for an application) that work and feel like simple requests.
1289
1290 * The IO::AIO::GRP objects will be cleaned up during calls to
1291 "IO::AIO::poll_cb", just like any other request.
1292
1293 * They can be canceled like any other request. Canceling will cancel
1294 not only the request itself, but also all requests it contains.
1295
1296 * They can also can also be added to other IO::AIO::GRP objects.
1297
1298 * You must not add requests to a group from within the group callback
1299 (or any later time).
1300
1301 Their lifetime, simplified, looks like this: when they are empty, they
1302 will finish very quickly. If they contain only requests that are in the
1303 "done" state, they will also finish. Otherwise they will continue to
1304 exist.
1305
1306 That means after creating a group you have some time to add requests
1307 (precisely before the callback has been invoked, which is only done
1308 within the "poll_cb"). And in the callbacks of those requests, you can
1309 add further requests to the group. And only when all those requests have
1310 finished will the the group itself finish.
1311
1312 add $grp ...
1313 $grp->add (...)
1314 Add one or more requests to the group. Any type of IO::AIO::REQ can
1315 be added, including other groups, as long as you do not create
1316 circular dependencies.
1317
1318 Returns all its arguments.
1319
1320 $grp->cancel_subs
1321 Cancel all subrequests and clears any feeder, but not the group
1322 request itself. Useful when you queued a lot of events but got a
1323 result early.
1324
1325 The group request will finish normally (you cannot add requests to
1326 the group).
1327
1328 $grp->result (...)
1329 Set the result value(s) that will be passed to the group callback
1330 when all subrequests have finished and set the groups errno to the
1331 current value of errno (just like calling "errno" without an error
1332 number). By default, no argument will be passed and errno is zero.
1333
1334 $grp->errno ([$errno])
1335 Sets the group errno value to $errno, or the current value of errno
1336 when the argument is missing.
1337
1338 Every aio request has an associated errno value that is restored
1339 when the callback is invoked. This method lets you change this value
1340 from its default (0).
1341
1342 Calling "result" will also set errno, so make sure you either set $!
1343 before the call to "result", or call c<errno> after it.
1344
1345 feed $grp $callback->($grp)
1346 Sets a feeder/generator on this group: every group can have an
1347 attached generator that generates requests if idle. The idea behind
1348 this is that, although you could just queue as many requests as you
1349 want in a group, this might starve other requests for a potentially
1350 long time. For example, "aio_scandir" might generate hundreds of
1351 thousands of "aio_stat" requests, delaying any later requests for a
1352 long time.
1353
1354 To avoid this, and allow incremental generation of requests, you can
1355 instead a group and set a feeder on it that generates those
1356 requests. The feed callback will be called whenever there are few
1357 enough (see "limit", below) requests active in the group itself and
1358 is expected to queue more requests.
1359
1360 The feed callback can queue as many requests as it likes (i.e. "add"
1361 does not impose any limits).
1362
1363 If the feed does not queue more requests when called, it will be
1364 automatically removed from the group.
1365
1366 If the feed limit is 0 when this method is called, it will be set to
1367 2 automatically.
1368
1369 Example:
1370
1371 # stat all files in @files, but only ever use four aio requests concurrently:
1372
1373 my $grp = aio_group sub { print "finished\n" };
1374 limit $grp 4;
1375 feed $grp sub {
1376 my $file = pop @files
1377 or return;
1378
1379 add $grp aio_stat $file, sub { ... };
1380 };
1381
1382 limit $grp $num
1383 Sets the feeder limit for the group: The feeder will be called
1384 whenever the group contains less than this many requests.
1385
1386 Setting the limit to 0 will pause the feeding process.
1387
1388 The default value for the limit is 0, but note that setting a feeder
1389 automatically bumps it up to 2.
1390
1391 SUPPORT FUNCTIONS
1392 EVENT PROCESSING AND EVENT LOOP INTEGRATION
1393 $fileno = IO::AIO::poll_fileno
1394 Return the *request result pipe file descriptor*. This filehandle
1395 must be polled for reading by some mechanism outside this module
1396 (e.g. EV, Glib, select and so on, see below or the SYNOPSIS). If the
1397 pipe becomes readable you have to call "poll_cb" to check the
1398 results.
1399
1400 See "poll_cb" for an example.
1401
1402 IO::AIO::poll_cb
1403 Process some requests that have reached the result phase (i.e. they
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.
1409 Returns immediately when no events are outstanding. The amount of
1410 events processed depends on the settings of "IO::AIO::max_poll_req",
1411 "IO::AIO::max_poll_time" and "IO::AIO::max_outstanding".
1412
1413 If not all requests were processed for whatever reason, the poll
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.
1424
1425 Example: Install an Event watcher that automatically calls
1426 IO::AIO::poll_cb with high priority (more examples can be found in
1427 the SYNOPSIS section, at the top of this document):
1428
1429 Event->io (fd => IO::AIO::poll_fileno,
1430 poll => 'r', async => 1,
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
1468
1469 IO::AIO::max_poll_reqs $nreqs
1470 IO::AIO::max_poll_time $seconds
1471 These set the maximum number of requests (default 0, meaning
1472 infinity) that are being processed by "IO::AIO::poll_cb" in one
1473 call, respectively the maximum amount of time (default 0, meaning
1474 infinity) spent in "IO::AIO::poll_cb" to process requests (more
1475 correctly the mininum amount of time "poll_cb" is allowed to use).
1476
1477 Setting "max_poll_time" to a non-zero value creates an overhead of
1478 one syscall per request processed, which is not normally a problem
1479 unless your callbacks are really really fast or your OS is really
1480 really slow (I am not mentioning Solaris here). Using
1481 "max_poll_reqs" incurs no overhead.
1482
1483 Setting these is useful if you want to ensure some level of
1484 interactiveness when perl is not fast enough to process all requests
1485 in time.
1486
1487 For interactive programs, values such as 0.01 to 0.1 should be fine.
1488
1489 Example: Install an Event watcher that automatically calls
1490 IO::AIO::poll_cb with low priority, to ensure that other parts of
1491 the program get the CPU sometimes even under high AIO load.
1492
1493 # try not to spend much more than 0.1s in poll_cb
1494 IO::AIO::max_poll_time 0.1;
1495
1496 # use a low priority so other tasks have priority
1497 Event->io (fd => IO::AIO::poll_fileno,
1498 poll => 'r', nice => 1,
1499 cb => &IO::AIO::poll_cb);
1500
1501 CONTROLLING THE NUMBER OF THREADS
1502 IO::AIO::min_parallel $nthreads
1503 Set the minimum number of AIO threads to $nthreads. The current
1504 default is 8, which means eight asynchronous operations can execute
1505 concurrently at any one time (the number of outstanding requests,
1506 however, is unlimited).
1507
1508 IO::AIO starts threads only on demand, when an AIO request is queued
1509 and no free thread exists. Please note that queueing up a hundred
1510 requests can create demand for a hundred threads, even if it turns
1511 out that everything is in the cache and could have been processed
1512 faster by a single thread.
1513
1514 It is recommended to keep the number of threads relatively low, as
1515 some Linux kernel versions will scale negatively with the number of
1516 threads (higher parallelity => MUCH higher latency). With current
1517 Linux 2.6 versions, 4-32 threads should be fine.
1518
1519 Under most circumstances you don't need to call this function, as
1520 the module selects a default that is suitable for low to moderate
1521 load.
1522
1523 IO::AIO::max_parallel $nthreads
1524 Sets the maximum number of AIO threads to $nthreads. If more than
1525 the specified number of threads are currently running, this function
1526 kills them. This function blocks until the limit is reached.
1527
1528 While $nthreads are zero, aio requests get queued but not executed
1529 until the number of threads has been increased again.
1530
1531 This module automatically runs "max_parallel 0" at program end, to
1532 ensure that all threads are killed and that there are no outstanding
495 requests. 1533 requests.
496 1534
497 * The IO::AIO::GRP objects will be cleaned up during calls to
498 "IO::AIO::poll_cb", just like any other request.
499 * They can be canceled like any other request. Canceling will cancel
500 not only the request itself, but also all requests it contains.
501 * They can also can also be added to other IO::AIO::GRP objects.
502 * You must not add requests to a group from within the group
503 callback (or any later time).
504
505 Their lifetime, simplified, looks like this: when they are empty,
506 they will finish very quickly. If they contain only requests that
507 are in the "done" state, they will also finish. Otherwise they will
508 continue to exist.
509
510 That means after creating a group you have some time to add
511 requests. And in the callbacks of those requests, you can add
512 further requests to the group. And only when all those requests have
513 finished will the the group itself finish.
514
515 add $grp ...
516 $grp->add (...)
517 Add one or more requests to the group. Any type of IO::AIO::REQ
518 can be added, including other groups, as long as you do not
519 create circular dependencies.
520
521 Returns all its arguments.
522
523 $grp->cancel_subs
524 Cancel all subrequests and clears any feeder, but not the group
525 request itself. Useful when you queued a lot of events but got a
526 result early.
527
528 $grp->result (...)
529 Set the result value(s) that will be passed to the group
530 callback when all subrequests have finished and set thre groups
531 errno to the current value of errno (just like calling "errno"
532 without an error number). By default, no argument will be passed
533 and errno is zero.
534
535 $grp->errno ([$errno])
536 Sets the group errno value to $errno, or the current value of
537 errno when the argument is missing.
538
539 Every aio request has an associated errno value that is restored
540 when the callback is invoked. This method lets you change this
541 value from its default (0).
542
543 Calling "result" will also set errno, so make sure you either
544 set $! before the call to "result", or call c<errno> after it.
545
546 feed $grp $callback->($grp)
547 Sets a feeder/generator on this group: every group can have an
548 attached generator that generates requests if idle. The idea
549 behind this is that, although you could just queue as many
550 requests as you want in a group, this might starve other
551 requests for a potentially long time. For example, "aio_scandir"
552 might generate hundreds of thousands "aio_stat" requests,
553 delaying any later requests for a long time.
554
555 To avoid this, and allow incremental generation of requests, you
556 can instead a group and set a feeder on it that generates those
557 requests. The feed callback will be called whenever there are
558 few enough (see "limit", below) requests active in the group
559 itself and is expected to queue more requests.
560
561 The feed callback can queue as many requests as it likes (i.e.
562 "add" does not impose any limits).
563
564 If the feed does not queue more requests when called, it will be
565 automatically removed from the group.
566
567 If the feed limit is 0, it will be set to 2 automatically.
568
569 Example:
570
571 # stat all files in @files, but only ever use four aio requests concurrently:
572
573 my $grp = aio_group sub { print "finished\n" };
574 limit $grp 4;
575 feed $grp sub {
576 my $file = pop @files
577 or return;
578
579 add $grp aio_stat $file, sub { ... };
580 };
581
582 limit $grp $num
583 Sets the feeder limit for the group: The feeder will be called
584 whenever the group contains less than this many requests.
585
586 Setting the limit to 0 will pause the feeding process.
587
588 SUPPORT FUNCTIONS
589 $fileno = IO::AIO::poll_fileno
590 Return the *request result pipe file descriptor*. This
591 filehandle must be polled for reading by some mechanism outside
592 this module (e.g. Event or select, see below or the SYNOPSIS).
593 If the pipe becomes readable you have to call "poll_cb" to check
594 the results.
595
596 See "poll_cb" for an example.
597
598 IO::AIO::poll_cb
599 Process all outstanding events on the result pipe. You have to
600 call this regularly. Returns the number of events processed.
601 Returns immediately when no events are outstanding.
602
603 If not all requests were processed for whatever reason, the
604 filehandle will still be ready when "poll_cb" returns.
605
606 Example: Install an Event watcher that automatically calls
607 IO::AIO::poll_cb with high priority:
608
609 Event->io (fd => IO::AIO::poll_fileno,
610 poll => 'r', async => 1,
611 cb => \&IO::AIO::poll_cb);
612
613 IO::AIO::poll_some $max_requests
614 Similar to "poll_cb", but only processes up to $max_requests
615 requests at a time.
616
617 Useful if you want to ensure some level of interactiveness when
618 perl is not fast enough to process all requests in time.
619
620 Example: Install an Event watcher that automatically calls
621 IO::AIO::poll_some with low priority, to ensure that other parts
622 of the program get the CPU sometimes even under high AIO load.
623
624 Event->io (fd => IO::AIO::poll_fileno,
625 poll => 'r', nice => 1,
626 cb => sub { IO::AIO::poll_some 256 });
627
628 IO::AIO::poll_wait
629 Wait till the result filehandle becomes ready for reading
630 (simply does a "select" on the filehandle. This is useful if you
631 want to synchronously wait for some requests to finish).
632
633 See "nreqs" for an example.
634
635 IO::AIO::nreqs
636 Returns the number of requests currently in the ready, execute
637 or pending states (i.e. for which their callback has not been
638 invoked yet).
639
640 Example: wait till there are no outstanding requests anymore:
641
642 IO::AIO::poll_wait, IO::AIO::poll_cb
643 while IO::AIO::nreqs;
644
645 IO::AIO::nready
646 Returns the number of requests currently in the ready state (not
647 yet executed).
648
649 IO::AIO::npending
650 Returns the number of requests currently in the pending state
651 (executed, but not yet processed by poll_cb).
652
653 IO::AIO::flush
654 Wait till all outstanding AIO requests have been handled.
655
656 Strictly equivalent to:
657
658 IO::AIO::poll_wait, IO::AIO::poll_cb
659 while IO::AIO::nreqs;
660
661 IO::AIO::poll
662 Waits until some requests have been handled.
663
664 Strictly equivalent to:
665
666 IO::AIO::poll_wait, IO::AIO::poll_cb
667 if IO::AIO::nreqs;
668
669 IO::AIO::min_parallel $nthreads
670 Set the minimum number of AIO threads to $nthreads. The current
671 default is 8, which means eight asynchronous operations can
672 execute concurrently at any one time (the number of outstanding
673 requests, however, is unlimited).
674
675 IO::AIO starts threads only on demand, when an AIO request is
676 queued and no free thread exists.
677
678 It is recommended to keep the number of threads relatively low,
679 as some Linux kernel versions will scale negatively with the
680 number of threads (higher parallelity => MUCH higher latency).
681 With current Linux 2.6 versions, 4-32 threads should be fine.
682
683 Under most circumstances you don't need to call this function,
684 as the module selects a default that is suitable for low to
685 moderate load.
686
687 IO::AIO::max_parallel $nthreads
688 Sets the maximum number of AIO threads to $nthreads. If more
689 than the specified number of threads are currently running, this
690 function kills them. This function blocks until the limit is
691 reached.
692
693 While $nthreads are zero, aio requests get queued but not
694 executed until the number of threads has been increased again.
695
696 This module automatically runs "max_parallel 0" at program end,
697 to ensure that all threads are killed and that there are no
698 outstanding requests.
699
700 Under normal circumstances you don't need to call this function. 1535 Under normal circumstances you don't need to call this function.
701 1536
1537 IO::AIO::max_idle $nthreads
1538 Limit the number of threads (default: 4) that are allowed to idle
1539 (i.e., threads that did not get a request to process within the idle
1540 timeout (default: 10 seconds). That means if a thread becomes idle
1541 while $nthreads other threads are also idle, it will free its
1542 resources and exit.
1543
1544 This is useful when you allow a large number of threads (e.g. 100 or
1545 1000) to allow for extremely high load situations, but want to free
1546 resources under normal circumstances (1000 threads can easily
1547 consume 30MB of RAM).
1548
1549 The default is probably ok in most situations, especially if thread
1550 creation is fast. If thread creation is very slow on your system you
1551 might want to use larger values.
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
702 $oldmaxreqs = IO::AIO::max_outstanding $maxreqs 1557 IO::AIO::max_outstanding $maxreqs
703 This is a very bad function to use in interactive programs
704 because it blocks, and a bad way to reduce concurrency because
705 it is inexact: Better use an "aio_group" together with a feed
706 callback.
707
708 Sets the maximum number of outstanding requests to $nreqs. If 1558 Sets the maximum number of outstanding requests to $nreqs. If you do
709 you to queue up more than this number of requests, the next call 1559 queue up more than this number of requests, the next call to
710 to the "poll_cb" (and "poll_some" and other functions calling 1560 "IO::AIO::poll_cb" (and other functions calling "poll_cb", such as
711 "poll_cb") function will block until the limit is no longer 1561 "IO::AIO::flush" or "IO::AIO::poll") will block until the limit is
712 exceeded. 1562 no longer exceeded.
713 1563
714 The default value is very large, so there is no practical limit 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
1567 This is a very bad function to use in interactive programs because
1568 it blocks, and a bad way to reduce concurrency because it is
1569 inexact: Better use an "aio_group" together with a feed callback.
1570
1571 Its main use is in scripts without an event loop - when you want to
1572 stat a lot of files, you can write something like this:
1573
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
715 on the number of outstanding requests. 1590 no practical limit on the number of outstanding requests.
716 1591
717 You can still queue as many requests as you want. Therefore, 1592 STATISTICAL INFORMATION
718 "max_oustsanding" is mainly useful in simple scripts (with low 1593 IO::AIO::nreqs
719 values) or as a stop gap to shield against fatal memory overflow 1594 Returns the number of requests currently in the ready, execute or
720 (with large values). 1595 pending states (i.e. for which their callback has not been invoked
1596 yet).
1597
1598 Example: wait till there are no outstanding requests anymore:
1599
1600 IO::AIO::poll_wait, IO::AIO::poll_cb
1601 while IO::AIO::nreqs;
1602
1603 IO::AIO::nready
1604 Returns the number of requests currently in the ready state (not yet
1605 executed).
1606
1607 IO::AIO::npending
1608 Returns the number of requests currently in the pending state
1609 (executed, but not yet processed by poll_cb).
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);
721 2023
722 FORK BEHAVIOUR 2024 FORK BEHAVIOUR
723 This module should do "the right thing" when the process using it 2025 Usage of pthreads in a program changes the semantics of fork
724 forks: 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.
725 2032
726 Before the fork, IO::AIO enters a quiescent state where no requests 2033 This module no longer tries to fight your OS, or POSIX. That means
727 can be added in other threads and no results will be processed. 2034 IO::AIO only works in the process that loaded it. Forking is fully
728 After the fork the parent simply leaves the quiescent state and 2035 supported, but using IO::AIO in the child is not.
729 continues request/result processing, while the child frees the
730 request/result queue (so that the requests started before the fork
731 will only be handled in the parent). Threads will be started on
732 demand until the limit set in the parent process has been reached
733 again.
734 2036
735 In short: the parent will, after a short pause, continue as if fork 2037 You might get around by not *using* IO::AIO before (or after) forking.
736 had not been called, while the child will act as if IO::AIO has not 2038 You could also try to call the IO::AIO::reinit function in the child:
737 been 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".
738 2059
739 MEMORY USAGE 2060 MEMORY USAGE
740 Per-request usage: 2061 Per-request usage:
741 2062
742 Each aio request uses - depending on your architecture - around 2063 Each aio request uses - depending on your architecture - around 100-200
743 100-200 bytes of memory. In addition, stat requests need a stat 2064 bytes of memory. In addition, stat requests need a stat buffer (possibly
744 buffer (possibly a few hundred bytes), readdir requires a result 2065 a few hundred bytes), readdir requires a result buffer and so on. Perl
745 buffer and so on. Perl scalars and other data passed into aio 2066 scalars and other data passed into aio requests will also be locked and
746 requests will also be locked and will consume memory till the 2067 will consume memory till the request has entered the done state.
747 request has entered the done state.
748 2068
749 This is now awfully much, so queuing lots of requests is not usually 2069 This is not awfully much, so queuing lots of requests is not usually a
750 a problem. 2070 problem.
751 2071
752 Per-thread usage: 2072 Per-thread usage:
753 2073
754 In the execution phase, some aio requests require more memory for 2074 In the execution phase, some aio requests require more memory for
755 temporary buffers, and each thread requires a stack and other data 2075 temporary buffers, and each thread requires a stack and other data
756 structures (usually around 16k-128k, depending on the OS). 2076 structures (usually around 16k-128k, depending on the OS).
757 2077
758KNOWN BUGS 2078KNOWN BUGS
759 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.
760 2090
761SEE ALSO 2091SEE ALSO
762 Coro::AIO. 2092 AnyEvent::AIO for easy integration into event loops, Coro::AIO for a
2093 more natural syntax.
763 2094
764AUTHOR 2095AUTHOR
765 Marc Lehmann <schmorp@schmorp.de> 2096 Marc Lehmann <schmorp@schmorp.de>
766 http://home.schmorp.de/ 2097 http://home.schmorp.de/
767 2098

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