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… …
2 IO::AIO - Asynchronous Input/Output 2 IO::AIO - Asynchronous Input/Output
3 3
4SYNOPSIS 4SYNOPSIS
5 use IO::AIO; 5 use IO::AIO;
6 6
7 aio_open "/etc/passwd", O_RDONLY, 0, sub { 7 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
8 my ($fh) = @_; 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
63 Although the module will work with in the presence of other (Perl-) 60 Although the module will work in the presence of other (Perl-) threads,
64 threads, it is currently not reentrant in any way, so use appropriate 61 it is currently not reentrant in any way, so use appropriate locking
65 locking yourself, always call "poll_cb" from within the same thread, or 62 yourself, always call "poll_cb" from within the same thread, or never
66 never call "poll_cb" (or other "aio_" functions) recursively. 63 call "poll_cb" (or other "aio_" functions) recursively.
64
65 EXAMPLE
66 This is a simple example that uses the EV module and loads /etc/passwd
67 asynchronously:
68
69 use Fcntl;
70 use EV;
71 use IO::AIO;
72
73 # register the IO::AIO callback with EV
74 my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
75
76 # queue the request to open /etc/passwd
77 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
78 my $fh = shift
79 or die "error while opening: $!";
80
81 # stat'ing filehandles is generally non-blocking
82 my $size = -s $fh;
83
84 # queue a request to read the file
85 my $contents;
86 aio_read $fh, 0, $size, $contents, 0, sub {
87 $_[0] == $size
88 or die "short read: $!";
89
90 close $fh;
91
92 # file contents now in $contents
93 print $contents;
94
95 # exit event loop and program
96 EV::unloop;
97 };
98 };
99
100 # possibly queue up other requests, or open GUI windows,
101 # check for sockets etc. etc.
102
103 # process events as long as there are some:
104 EV::loop;
67 105
68REQUEST ANATOMY AND LIFETIME 106REQUEST ANATOMY AND LIFETIME
69 Every "aio_*" function creates a request. which is a C data structure 107 Every "aio_*" function creates a request. which is a C data structure
70 not directly visible to Perl. 108 not directly visible to Perl.
71 109
… …
107 anymore (except possibly for the Perl object, but its connection to 145 anymore (except possibly for the Perl object, but its connection to
108 the actual aio request is severed and calling its methods will 146 the actual aio request is severed and calling its methods will
109 either do nothing or result in a runtime error). 147 either do nothing or result in a runtime error).
110 148
111FUNCTIONS 149FUNCTIONS
112 AIO FUNCTIONS 150 QUICK OVERVIEW
113 All the "aio_*" calls are more or less thin wrappers around the 151 This section simply lists the prototypes of the most important functions
114 syscall with the same name (sans "aio_"). The arguments are similar 152 for quick reference. See the following sections for function-by-function
115 or identical, and they all accept an additional (and optional) 153 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.
121 154
122 All functions expecting a filehandle keep a copy of the filehandle
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) 155 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) 156 aio_close $fh, $callback->($status)
199 Asynchronously close a file and call the callback with the
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, 157 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
210 $callback->($retval)
211 aio_write $fh,$offset,$length, $data,$dataoffset, 158 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, 159 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) 160 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) 161 aio_stat $fh_or_path, $callback->($status)
287 aio_lstat $fh, $callback->($status) 162 aio_lstat $fh, $callback->($status)
288 Works like perl's "stat" or "lstat" in void context. The 163 aio_statvfs $fh_or_path, $callback->($statvfs)
289 callback will be called after the stat and the results will be 164 aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
290 available using "stat _" or "-s _" etc... 165 aio_chown $fh_or_path, $uid, $gid, $callback->($status)
291 166 aio_truncate $fh_or_path, $offset, $callback->($status)
292 The pathname passed to "aio_stat" must be absolute. See API 167 aio_chmod $fh_or_path, $mode, $callback->($status)
293 NOTES, above, for an explanation.
294
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) 168 aio_unlink $pathname, $callback->($status)
308 Asynchronously unlink (delete) a file and call the callback with 169 aio_mknod $path, $mode, $dev, $callback->($status)
309 the result code.
310
311 aio_link $srcpath, $dstpath, $callback->($status) 170 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) 171 aio_symlink $srcpath, $dstpath, $callback->($status)
317 Asynchronously create a new symbolic link to the existing object 172 aio_readlink $path, $callback->($link)
318 at $srcpath at the path $dstpath and call the callback with the
319 result code.
320
321 aio_rename $srcpath, $dstpath, $callback->($status) 173 aio_rename $srcpath, $dstpath, $callback->($status)
322 Asynchronously rename the object at $srcpath to $dstpath, just 174 aio_mkdir $pathname, $mode, $callback->($status)
323 as rename(2) and call the callback with the result code.
324
325 aio_rmdir $pathname, $callback->($status) 175 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) 176 aio_readdir $pathname, $callback->($entries)
330 Unlike the POSIX call of the same name, "aio_readdir" reads an 177 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
331 entire directory (i.e. opendir + readdir + closedir). The 178 IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
332 entries will not be sorted, and will NOT include the "." and 179 IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
333 ".." entries. 180 aio_load $path, $data, $callback->($status)
334 181 aio_copy $srcpath, $dstpath, $callback->($status)
335 The callback a single argument which is either "undef" or an 182 aio_move $srcpath, $dstpath, $callback->($status)
336 array-ref with the filenames.
337
338 aio_scandir $path, $maxreq, $callback->($dirs, $nondirs) 183 aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
339 Scans a directory (similar to "aio_readdir") but additionally 184 aio_rmtree $path, $callback->($status)
340 tries to efficiently separate the entries of directory $path 185 aio_sync $callback->($status)
341 into two sets of names, directories you can recurse into
342 (directories), and ones you cannot recurse into (everything
343 else, including symlinks to directories).
344
345 "aio_scandir" is a composite request that creates of many sub
346 requests_ $maxreq specifies the maximum number of outstanding
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) 186 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) 187 aio_fdatasync $fh, $callback->($status)
399 Asynchronously call fdatasync on the given filehandle and call 188 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
400 the callback with the fdatasync result code. 189 aio_pathsync $path, $callback->($status)
401 190 aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
402 If this call isn't available because your OS lacks it or it 191 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
403 couldn't be detected, it will be emulated by calling "fsync" 192 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
404 instead. 193 aio_mlockall $flags, $callback->($status)
405
406 aio_group $callback->(...) 194 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->() 195 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.
432 196
433 While this request does nothing, it still goes through the 197 $prev_pri = aioreq_pri [$pri]
434 execution phase and still requires a worker thread. Thus, the 198 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.
438 199
439 IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED* 200 IO::AIO::poll_wait
440 Mainly used for debugging and benchmarking, this aio request 201 IO::AIO::poll_cb
441 puts one of the request workers to sleep for the given time. 202 IO::AIO::poll
203 IO::AIO::flush
204 IO::AIO::max_poll_reqs $nreqs
205 IO::AIO::max_poll_time $seconds
206 IO::AIO::min_parallel $nthreads
207 IO::AIO::max_parallel $nthreads
208 IO::AIO::max_idle $nthreads
209 IO::AIO::max_outstanding $maxreqs
210 IO::AIO::nreqs
211 IO::AIO::nready
212 IO::AIO::npending
442 213
443 While it is theoretically handy to have simple I/O scheduling 214 IO::AIO::sendfile $ofh, $ifh, $offset, $count
444 requests like sleep and file handle readable/writable, the 215 IO::AIO::fadvise $fh, $offset, $len, $advice
445 overhead this creates is immense (it blocks a thread for a long 216 IO::AIO::madvise $scalar, $offset, $length, $advice
446 time) so do not use this function except to put your application 217 IO::AIO::mprotect $scalar, $offset, $length, $protect
447 under artificial I/O pressure. 218 IO::AIO::munlock $scalar, $offset = 0, $length = undef
219 IO::AIO::munlockall
448 220
449 IO::AIO::REQ CLASS 221 AIO REQUEST FUNCTIONS
450 All non-aggregate "aio_*" functions return an object of this class 222 All the "aio_*" calls are more or less thin wrappers around the syscall
451 when called in non-void context. 223 with the same name (sans "aio_"). The arguments are similar or
224 identical, and they all accept an additional (and optional) $callback
225 argument which must be a code reference. This code reference will get
226 called with the syscall return code (e.g. most syscalls return -1 on
227 error, unlike perl, which usually delivers "false") as its sole argument
228 after the given syscall has been executed asynchronously.
452 229
453 cancel $req 230 All functions expecting a filehandle keep a copy of the filehandle
454 Cancels the request, if possible. Has the effect of skipping 231 internally until the request has finished.
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.
460 232
461 cb $req $callback->(...) 233 All functions return request objects of type IO::AIO::REQ that allow
462 Replace (or simply set) the callback registered to the request. 234 further manipulation of those requests while they are in-flight.
463 235
464 IO::AIO::GRP CLASS 236 The pathnames you pass to these routines *must* be absolute and encoded
465 This class is a subclass of IO::AIO::REQ, so all its methods apply 237 as octets. The reason for the former is that at the time the request is
466 to objects of this class, too. 238 being executed, the current working directory could have changed.
239 Alternatively, you can make sure that you never change the current
240 working directory anywhere in the program and then use relative paths.
467 241
468 A IO::AIO::GRP object is a special request that can contain multiple 242 To encode pathnames as octets, either make sure you either: a) always
469 other aio requests. 243 pass in filenames you got from outside (command line, readdir etc.)
244 without tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module
245 and encode your pathnames to the locale (or other) encoding in effect in
246 the user environment, d) use Glib::filename_from_unicode on unicode
247 filenames or e) use something else to ensure your scalar has the correct
248 contents.
470 249
471 You create one by calling the "aio_group" constructing function with 250 This works, btw. independent of the internal UTF-8 bit, which IO::AIO
472 a callback that will be called when all contained requests have 251 handles correctly whether it is set or not.
473 entered the "done" state:
474 252
475 my $grp = aio_group sub { 253 $prev_pri = aioreq_pri [$pri]
476 print "all requests are done\n"; 254 Returns the priority value that would be used for the next request
477 }; 255 and, if $pri is given, sets the priority for the next aio request.
478 256
479 You add requests by calling the "add" method with one or more 257 The default priority is 0, the minimum and maximum priorities are -4
480 "IO::AIO::REQ" objects: 258 and 4, respectively. Requests with higher priority will be serviced
259 first.
481 260
482 $grp->add (aio_unlink "..."); 261 The priority will be reset to 0 after each call to one of the
262 "aio_*" functions.
483 263
484 add $grp aio_stat "...", sub { 264 Example: open a file with low priority, then read something from it
485 $_[0] or return $grp->result ("error"); 265 with higher priority so the read request is serviced before other
266 low priority open requests (potentially spamming the cache):
486 267
487 # add another request dynamically, if first succeeded 268 aioreq_pri -3;
488 add $grp aio_open "...", sub { 269 aio_open ..., sub {
489 $grp->result ("ok"); 270 return unless $_[0];
271
272 aioreq_pri -2;
273 aio_read $_[0], ..., sub {
274 ...
490 }; 275 };
491 }; 276 };
492 277
278 aioreq_nice $pri_adjust
279 Similar to "aioreq_pri", but subtracts the given value from the
280 current priority, so the effect is cumulative.
281
282 aio_open $pathname, $flags, $mode, $callback->($fh)
283 Asynchronously open or create a file and call the callback with a
284 newly created filehandle for the file.
285
286 The pathname passed to "aio_open" must be absolute. See API NOTES,
287 above, for an explanation.
288
289 The $flags argument is a bitmask. See the "Fcntl" module for a list.
290 They are the same as used by "sysopen".
291
292 Likewise, $mode specifies the mode of the newly created file, if it
293 didn't exist and "O_CREAT" has been given, just like perl's
294 "sysopen", except that it is mandatory (i.e. use 0 if you don't
295 create new files, and 0666 or 0777 if you do). Note that the $mode
296 will be modified by the umask in effect then the request is being
297 executed, so better never change the umask.
298
299 Example:
300
301 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
302 if ($_[0]) {
303 print "open successful, fh is $_[0]\n";
304 ...
305 } else {
306 die "open failed: $!\n";
307 }
308 };
309
310 aio_close $fh, $callback->($status)
311 Asynchronously close a file and call the callback with the result
312 code.
313
314 Unfortunately, you can't do this to perl. Perl *insists* very
315 strongly on closing the file descriptor associated with the
316 filehandle itself.
317
318 Therefore, "aio_close" will not close the filehandle - instead it
319 will use dup2 to overwrite the file descriptor with the write-end of
320 a pipe (the pipe fd will be created on demand and will be cached).
321
322 Or in other words: the file descriptor will be closed, but it will
323 not be free for reuse until the perl filehandle is closed.
324
325 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
326 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
327 Reads or writes $length bytes from or to the specified $fh and
328 $offset into the scalar given by $data and offset $dataoffset and
329 calls the callback without the actual number of bytes read (or -1 on
330 error, just like the syscall).
331
332 "aio_read" will, like "sysread", shrink or grow the $data scalar to
333 offset plus the actual number of bytes read.
334
335 If $offset is undefined, then the current file descriptor offset
336 will be used (and updated), otherwise the file descriptor offset
337 will not be changed by these calls.
338
339 If $length is undefined in "aio_write", use the remaining length of
340 $data.
341
342 If $dataoffset is less than zero, it will be counted from the end of
343 $data.
344
345 The $data scalar *MUST NOT* be modified in any way while the request
346 is outstanding. Modifying it can result in segfaults or World War
347 III (if the necessary/optional hardware is installed).
348
349 Example: Read 15 bytes at offset 7 into scalar $buffer, starting at
350 offset 0 within the scalar:
351
352 aio_read $fh, 7, 15, $buffer, 0, sub {
353 $_[0] > 0 or die "read error: $!";
354 print "read $_[0] bytes: <$buffer>\n";
355 };
356
357 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
358 Tries to copy $length bytes from $in_fh to $out_fh. It starts
359 reading at byte offset $in_offset, and starts writing at the current
360 file offset of $out_fh. Because of that, it is not safe to issue
361 more than one "aio_sendfile" per $out_fh, as they will interfere
362 with each other.
363
364 This call tries to make use of a native "sendfile" syscall to
365 provide zero-copy operation. For this to work, $out_fh should refer
366 to a socket, and $in_fh should refer to an mmap'able file.
367
368 If a native sendfile cannot be found or it fails with "ENOSYS",
369 "ENOTSUP", "EOPNOTSUPP", "EAFNOSUPPORT", "EPROTOTYPE" or "ENOTSOCK",
370 it will be emulated, so you can call "aio_sendfile" on any type of
371 filehandle regardless of the limitations of the operating system.
372
373 Please note, however, that "aio_sendfile" can read more bytes from
374 $in_fh than are written, and there is no way to find out how many
375 bytes have been read from "aio_sendfile" alone, as "aio_sendfile"
376 only provides the number of bytes written to $out_fh. Only if the
377 result value equals $length one can assume that $length bytes have
378 been read.
379
380 aio_readahead $fh,$offset,$length, $callback->($retval)
381 "aio_readahead" populates the page cache with data from a file so
382 that subsequent reads from that file will not block on disk I/O. The
383 $offset argument specifies the starting point from which data is to
384 be read and $length specifies the number of bytes to be read. I/O is
385 performed in whole pages, so that offset is effectively rounded down
386 to a page boundary and bytes are read up to the next page boundary
387 greater than or equal to (off-set+length). "aio_readahead" does not
388 read beyond the end of the file. The current file offset of the file
389 is left unchanged.
390
391 If that syscall doesn't exist (likely if your OS isn't Linux) it
392 will be emulated by simply reading the data, which would have a
393 similar effect.
394
395 aio_stat $fh_or_path, $callback->($status)
396 aio_lstat $fh, $callback->($status)
397 Works like perl's "stat" or "lstat" in void context. The callback
398 will be called after the stat and the results will be available
399 using "stat _" or "-s _" etc...
400
401 The pathname passed to "aio_stat" must be absolute. See API NOTES,
402 above, for an explanation.
403
404 Currently, the stats are always 64-bit-stats, i.e. instead of
405 returning an error when stat'ing a large file, the results will be
406 silently truncated unless perl itself is compiled with large file
407 support.
408
409 Example: Print the length of /etc/passwd:
410
411 aio_stat "/etc/passwd", sub {
412 $_[0] and die "stat failed: $!";
413 print "size is ", -s _, "\n";
414 };
415
416 aio_statvfs $fh_or_path, $callback->($statvfs)
417 Works like the POSIX "statvfs" or "fstatvfs" syscalls, depending on
418 whether a file handle or path was passed.
419
420 On success, the callback is passed a hash reference with the
421 following members: "bsize", "frsize", "blocks", "bfree", "bavail",
422 "files", "ffree", "favail", "fsid", "flag" and "namemax". On
423 failure, "undef" is passed.
424
425 The following POSIX IO::AIO::ST_* constants are defined: "ST_RDONLY"
426 and "ST_NOSUID".
427
428 The following non-POSIX IO::AIO::ST_* flag masks are defined to
429 their correct value when available, or to 0 on systems that do not
430 support them: "ST_NODEV", "ST_NOEXEC", "ST_SYNCHRONOUS",
431 "ST_MANDLOCK", "ST_WRITE", "ST_APPEND", "ST_IMMUTABLE",
432 "ST_NOATIME", "ST_NODIRATIME" and "ST_RELATIME".
433
434 Example: stat "/wd" and dump out the data if successful.
435
436 aio_statvfs "/wd", sub {
437 my $f = $_[0]
438 or die "statvfs: $!";
439
440 use Data::Dumper;
441 say Dumper $f;
442 };
443
444 # result:
445 {
446 bsize => 1024,
447 bfree => 4333064312,
448 blocks => 10253828096,
449 files => 2050765568,
450 flag => 4096,
451 favail => 2042092649,
452 bavail => 4333064312,
453 ffree => 2042092649,
454 namemax => 255,
455 frsize => 1024,
456 fsid => 1810
457 }
458
459 aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
460 Works like perl's "utime" function (including the special case of
461 $atime and $mtime being undef). Fractional times are supported if
462 the underlying syscalls support them.
463
464 When called with a pathname, uses utimes(2) if available, otherwise
465 utime(2). If called on a file descriptor, uses futimes(2) if
466 available, otherwise returns ENOSYS, so this is not portable.
467
468 Examples:
469
470 # set atime and mtime to current time (basically touch(1)):
471 aio_utime "path", undef, undef;
472 # set atime to current time and mtime to beginning of the epoch:
473 aio_utime "path", time, undef; # undef==0
474
475 aio_chown $fh_or_path, $uid, $gid, $callback->($status)
476 Works like perl's "chown" function, except that "undef" for either
477 $uid or $gid is being interpreted as "do not change" (but -1 can
478 also be used).
479
480 Examples:
481
482 # same as "chown root path" in the shell:
483 aio_chown "path", 0, -1;
484 # same as above:
485 aio_chown "path", 0, undef;
486
487 aio_truncate $fh_or_path, $offset, $callback->($status)
488 Works like truncate(2) or ftruncate(2).
489
490 aio_chmod $fh_or_path, $mode, $callback->($status)
491 Works like perl's "chmod" function.
492
493 aio_unlink $pathname, $callback->($status)
494 Asynchronously unlink (delete) a file and call the callback with the
495 result code.
496
497 aio_mknod $path, $mode, $dev, $callback->($status)
498 [EXPERIMENTAL]
499
500 Asynchronously create a device node (or fifo). See mknod(2).
501
502 The only (POSIX-) portable way of calling this function is:
503
504 aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...
505
506 aio_link $srcpath, $dstpath, $callback->($status)
507 Asynchronously create a new link to the existing object at $srcpath
508 at the path $dstpath and call the callback with the result code.
509
510 aio_symlink $srcpath, $dstpath, $callback->($status)
511 Asynchronously create a new symbolic link to the existing object at
512 $srcpath at the path $dstpath and call the callback with the result
513 code.
514
515 aio_readlink $path, $callback->($link)
516 Asynchronously read the symlink specified by $path and pass it to
517 the callback. If an error occurs, nothing or undef gets passed to
518 the callback.
519
520 aio_rename $srcpath, $dstpath, $callback->($status)
521 Asynchronously rename the object at $srcpath to $dstpath, just as
522 rename(2) and call the callback with the result code.
523
524 aio_mkdir $pathname, $mode, $callback->($status)
525 Asynchronously mkdir (create) a directory and call the callback with
526 the result code. $mode will be modified by the umask at the time the
527 request is executed, so do not change your umask.
528
529 aio_rmdir $pathname, $callback->($status)
530 Asynchronously rmdir (delete) a directory and call the callback with
531 the result code.
532
533 aio_readdir $pathname, $callback->($entries)
534 Unlike the POSIX call of the same name, "aio_readdir" reads an
535 entire directory (i.e. opendir + readdir + closedir). The entries
536 will not be sorted, and will NOT include the "." and ".." entries.
537
538 The callback is passed a single argument which is either "undef" or
539 an array-ref with the filenames.
540
541 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
542 Quite similar to "aio_readdir", but the $flags argument allows to
543 tune behaviour and output format. In case of an error, $entries will
544 be "undef".
545
546 The flags are a combination of the following constants, ORed
547 together (the flags will also be passed to the callback, possibly
548 modified):
549
550 IO::AIO::READDIR_DENTS
551 When this flag is off, then the callback gets an arrayref with
552 of names only (as with "aio_readdir"), otherwise it gets an
553 arrayref with "[$name, $type, $inode]" arrayrefs, each
554 describing a single directory entry in more detail.
555
556 $name is the name of the entry.
557
558 $type is one of the "IO::AIO::DT_xxx" constants:
559
560 "IO::AIO::DT_UNKNOWN", "IO::AIO::DT_FIFO", "IO::AIO::DT_CHR",
561 "IO::AIO::DT_DIR", "IO::AIO::DT_BLK", "IO::AIO::DT_REG",
562 "IO::AIO::DT_LNK", "IO::AIO::DT_SOCK", "IO::AIO::DT_WHT".
563
564 "IO::AIO::DT_UNKNOWN" means just that: readdir does not know. If
565 you need to know, you have to run stat yourself. Also, for speed
566 reasons, the $type scalars are read-only: you can not modify
567 them.
568
569 $inode is the inode number (which might not be exact on systems
570 with 64 bit inode numbers and 32 bit perls). This field has
571 unspecified content on systems that do not deliver the inode
572 information.
573
574 IO::AIO::READDIR_DIRS_FIRST
575 When this flag is set, then the names will be returned in an
576 order where likely directories come first. This is useful when
577 you need to quickly find directories, or you want to find all
578 directories while avoiding to stat() each entry.
579
580 If the system returns type information in readdir, then this is
581 used to find directories directly. Otherwise, likely directories
582 are files beginning with ".", or otherwise files with no dots,
583 of which files with short names are tried first.
584
585 IO::AIO::READDIR_STAT_ORDER
586 When this flag is set, then the names will be returned in an
587 order suitable for stat()'ing each one. That is, when you plan
588 to stat() all files in the given directory, then the returned
589 order will likely be fastest.
590
591 If both this flag and "IO::AIO::READDIR_DIRS_FIRST" are
592 specified, then the likely dirs come first, resulting in a less
593 optimal stat order.
594
595 IO::AIO::READDIR_FOUND_UNKNOWN
596 This flag should not be set when calling "aio_readdirx".
597 Instead, it is being set by "aio_readdirx", when any of the
598 $type's found were "IO::AIO::DT_UNKNOWN". The absense of this
599 flag therefore indicates that all $type's are known, which can
600 be used to speed up some algorithms.
601
602 aio_load $path, $data, $callback->($status)
603 This is a composite request that tries to fully load the given file
604 into memory. Status is the same as with aio_read.
605
606 aio_copy $srcpath, $dstpath, $callback->($status)
607 Try to copy the *file* (directories not supported as either source
608 or destination) from $srcpath to $dstpath and call the callback with
609 a status of 0 (ok) or -1 (error, see $!).
610
611 This is a composite request that creates the destination file with
612 mode 0200 and copies the contents of the source file into it using
613 "aio_sendfile", followed by restoring atime, mtime, access mode and
614 uid/gid, in that order.
615
616 If an error occurs, the partial destination file will be unlinked,
617 if possible, except when setting atime, mtime, access mode and
618 uid/gid, where errors are being ignored.
619
620 aio_move $srcpath, $dstpath, $callback->($status)
621 Try to move the *file* (directories not supported as either source
622 or destination) from $srcpath to $dstpath and call the callback with
623 a status of 0 (ok) or -1 (error, see $!).
624
625 This is a composite request that tries to rename(2) the file first;
626 if rename fails with "EXDEV", it copies the file with "aio_copy"
627 and, if that is successful, unlinks the $srcpath.
628
629 aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
630 Scans a directory (similar to "aio_readdir") but additionally tries
631 to efficiently separate the entries of directory $path into two sets
632 of names, directories you can recurse into (directories), and ones
633 you cannot recurse into (everything else, including symlinks to
634 directories).
635
636 "aio_scandir" is a composite request that creates of many sub
637 requests_ $maxreq specifies the maximum number of outstanding aio
638 requests that this function generates. If it is "<= 0", then a
639 suitable default will be chosen (currently 4).
640
641 On error, the callback is called without arguments, otherwise it
642 receives two array-refs with path-relative entry names.
643
644 Example:
645
646 aio_scandir $dir, 0, sub {
647 my ($dirs, $nondirs) = @_;
648 print "real directories: @$dirs\n";
649 print "everything else: @$nondirs\n";
650 };
651
652 Implementation notes.
653
654 The "aio_readdir" cannot be avoided, but "stat()"'ing every entry
655 can.
656
657 If readdir returns file type information, then this is used directly
658 to find directories.
659
660 Otherwise, after reading the directory, the modification time, size
661 etc. of the directory before and after the readdir is checked, and
662 if they match (and isn't the current time), the link count will be
663 used to decide how many entries are directories (if >= 2).
664 Otherwise, no knowledge of the number of subdirectories will be
665 assumed.
666
667 Then entries will be sorted into likely directories a non-initial
668 dot currently) and likely non-directories (see "aio_readdirx"). Then
669 every entry plus an appended "/." will be "stat"'ed, likely
670 directories first, in order of their inode numbers. If that
671 succeeds, it assumes that the entry is a directory or a symlink to
672 directory (which will be checked seperately). This is often faster
673 than stat'ing the entry itself because filesystems might detect the
674 type of the entry without reading the inode data (e.g. ext2fs
675 filetype feature), even on systems that cannot return the filetype
676 information on readdir.
677
678 If the known number of directories (link count - 2) has been
679 reached, the rest of the entries is assumed to be non-directories.
680
681 This only works with certainty on POSIX (= UNIX) filesystems, which
682 fortunately are the vast majority of filesystems around.
683
684 It will also likely work on non-POSIX filesystems with reduced
685 efficiency as those tend to return 0 or 1 as link counts, which
686 disables the directory counting heuristic.
687
688 aio_rmtree $path, $callback->($status)
689 Delete a directory tree starting (and including) $path, return the
690 status of the final "rmdir" only. This is a composite request that
691 uses "aio_scandir" to recurse into and rmdir directories, and unlink
692 everything else.
693
694 aio_sync $callback->($status)
695 Asynchronously call sync and call the callback when finished.
696
697 aio_fsync $fh, $callback->($status)
698 Asynchronously call fsync on the given filehandle and call the
699 callback with the fsync result code.
700
701 aio_fdatasync $fh, $callback->($status)
702 Asynchronously call fdatasync on the given filehandle and call the
703 callback with the fdatasync result code.
704
705 If this call isn't available because your OS lacks it or it couldn't
706 be detected, it will be emulated by calling "fsync" instead.
707
708 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
709 Sync the data portion of the file specified by $offset and $length
710 to disk (but NOT the metadata), by calling the Linux-specific
711 sync_file_range call. If sync_file_range is not available or it
712 returns ENOSYS, then fdatasync or fsync is being substituted.
713
714 $flags can be a combination of
715 "IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE",
716 "IO::AIO::SYNC_FILE_RANGE_WRITE" and
717 "IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER": refer to the sync_file_range
718 manpage for details.
719
720 aio_pathsync $path, $callback->($status)
721 This request tries to open, fsync and close the given path. This is
722 a composite request intended to sync directories after directory
723 operations (E.g. rename). This might not work on all operating
724 systems or have any specific effect, but usually it makes sure that
725 directory changes get written to disc. It works for anything that
726 can be opened for read-only, not just directories.
727
728 Future versions of this function might fall back to other methods
729 when "fsync" on the directory fails (such as calling "sync").
730
731 Passes 0 when everything went ok, and -1 on error.
732
733 aio_msync $scalar, $offset = 0, $length = undef, flags = 0,
734 $callback->($status)
735 This is a rather advanced IO::AIO call, which only works on
736 mmap(2)ed scalars (see the "IO::AIO::mmap" function, although it
737 also works on data scalars managed by the Sys::Mmap or Mmap modules,
738 note that the scalar must only be modified in-place while an aio
739 operation is pending on it).
740
741 It calls the "msync" function of your OS, if available, with the
742 memory area starting at $offset in the string and ending $length
743 bytes later. If $length is negative, counts from the end, and if
744 $length is "undef", then it goes till the end of the string. The
745 flags can be a combination of "IO::AIO::MS_ASYNC",
746 "IO::AIO::MS_INVALIDATE" and "IO::AIO::MS_SYNC".
747
748 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0,
749 $callback->($status)
750 This is a rather advanced IO::AIO call, which works best on
751 mmap(2)ed scalars.
752
753 It touches (reads or writes) all memory pages in the specified range
754 inside the scalar. All caveats and parameters are the same as for
755 "aio_msync", above, except for flags, which must be either 0 (which
756 reads all pages and ensures they are instantiated) or
757 "IO::AIO::MT_MODIFY", which modifies the memory page s(by reading
758 and writing an octet from it, which dirties the page).
759
760 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
761 This is a rather advanced IO::AIO call, which works best on
762 mmap(2)ed scalars.
763
764 It reads in all the pages of the underlying storage into memory (if
765 any) and locks them, so they are not getting swapped/paged out or
766 removed.
767
768 If $length is undefined, then the scalar will be locked till the
769 end.
770
771 On systems that do not implement "mlock", this function returns -1
772 and sets errno to "ENOSYS".
773
774 Note that the corresponding "munlock" is synchronous and is
775 documented under "MISCELLANEOUS FUNCTIONS".
776
777 Example: open a file, mmap and mlock it - both will be undone when
778 $data gets destroyed.
779
780 open my $fh, "<", $path or die "$path: $!";
781 my $data;
782 IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
783 aio_mlock $data; # mlock in background
784
785 aio_mlockall $flags, $callback->($status)
786 Calls the "mlockall" function with the given $flags (a combination
787 of "IO::AIO::MCL_CURRENT" and "IO::AIO::MCL_FUTURE").
788
789 On systems that do not implement "mlockall", this function returns
790 -1 and sets errno to "ENOSYS".
791
792 Note that the corresponding "munlockall" is synchronous and is
793 documented under "MISCELLANEOUS FUNCTIONS".
794
795 Example: asynchronously lock all current and future pages into
796 memory.
797
798 aio_mlockall IO::AIO::MCL_FUTURE;
799
800 aio_group $callback->(...)
801 This is a very special aio request: Instead of doing something, it
802 is a container for other aio requests, which is useful if you want
803 to bundle many requests into a single, composite, request with a
804 definite callback and the ability to cancel the whole request with
805 its subrequests.
806
807 Returns an object of class IO::AIO::GRP. See its documentation below
808 for more info.
809
810 Example:
811
812 my $grp = aio_group sub {
813 print "all stats done\n";
814 };
815
816 add $grp
817 (aio_stat ...),
818 (aio_stat ...),
819 ...;
820
821 aio_nop $callback->()
822 This is a special request - it does nothing in itself and is only
823 used for side effects, such as when you want to add a dummy request
824 to a group so that finishing the requests in the group depends on
825 executing the given code.
826
827 While this request does nothing, it still goes through the execution
828 phase and still requires a worker thread. Thus, the callback will
829 not be executed immediately but only after other requests in the
830 queue have entered their execution phase. This can be used to
831 measure request latency.
832
833 IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
834 Mainly used for debugging and benchmarking, this aio request puts
835 one of the request workers to sleep for the given time.
836
837 While it is theoretically handy to have simple I/O scheduling
838 requests like sleep and file handle readable/writable, the overhead
839 this creates is immense (it blocks a thread for a long time) so do
840 not use this function except to put your application under
841 artificial I/O pressure.
842
843 IO::AIO::REQ CLASS
844 All non-aggregate "aio_*" functions return an object of this class when
845 called in non-void context.
846
847 cancel $req
848 Cancels the request, if possible. Has the effect of skipping
849 execution when entering the execute state and skipping calling the
850 callback when entering the the result state, but will leave the
851 request otherwise untouched (with the exception of readdir). That
852 means that requests that currently execute will not be stopped and
853 resources held by the request will not be freed prematurely.
854
855 cb $req $callback->(...)
856 Replace (or simply set) the callback registered to the request.
857
858 IO::AIO::GRP CLASS
859 This class is a subclass of IO::AIO::REQ, so all its methods apply to
860 objects of this class, too.
861
862 A IO::AIO::GRP object is a special request that can contain multiple
863 other aio requests.
864
865 You create one by calling the "aio_group" constructing function with a
866 callback that will be called when all contained requests have entered
867 the "done" state:
868
869 my $grp = aio_group sub {
870 print "all requests are done\n";
871 };
872
873 You add requests by calling the "add" method with one or more
874 "IO::AIO::REQ" objects:
875
876 $grp->add (aio_unlink "...");
877
878 add $grp aio_stat "...", sub {
879 $_[0] or return $grp->result ("error");
880
881 # add another request dynamically, if first succeeded
882 add $grp aio_open "...", sub {
883 $grp->result ("ok");
884 };
885 };
886
493 This makes it very easy to create composite requests (see the source 887 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 888 "aio_move" for an application) that work and feel like simple requests.
889
890 * The IO::AIO::GRP objects will be cleaned up during calls to
891 "IO::AIO::poll_cb", just like any other request.
892
893 * They can be canceled like any other request. Canceling will cancel
894 not only the request itself, but also all requests it contains.
895
896 * They can also can also be added to other IO::AIO::GRP objects.
897
898 * You must not add requests to a group from within the group callback
899 (or any later time).
900
901 Their lifetime, simplified, looks like this: when they are empty, they
902 will finish very quickly. If they contain only requests that are in the
903 "done" state, they will also finish. Otherwise they will continue to
904 exist.
905
906 That means after creating a group you have some time to add requests
907 (precisely before the callback has been invoked, which is only done
908 within the "poll_cb"). And in the callbacks of those requests, you can
909 add further requests to the group. And only when all those requests have
910 finished will the the group itself finish.
911
912 add $grp ...
913 $grp->add (...)
914 Add one or more requests to the group. Any type of IO::AIO::REQ can
915 be added, including other groups, as long as you do not create
916 circular dependencies.
917
918 Returns all its arguments.
919
920 $grp->cancel_subs
921 Cancel all subrequests and clears any feeder, but not the group
922 request itself. Useful when you queued a lot of events but got a
923 result early.
924
925 The group request will finish normally (you cannot add requests to
926 the group).
927
928 $grp->result (...)
929 Set the result value(s) that will be passed to the group callback
930 when all subrequests have finished and set the groups errno to the
931 current value of errno (just like calling "errno" without an error
932 number). By default, no argument will be passed and errno is zero.
933
934 $grp->errno ([$errno])
935 Sets the group errno value to $errno, or the current value of errno
936 when the argument is missing.
937
938 Every aio request has an associated errno value that is restored
939 when the callback is invoked. This method lets you change this value
940 from its default (0).
941
942 Calling "result" will also set errno, so make sure you either set $!
943 before the call to "result", or call c<errno> after it.
944
945 feed $grp $callback->($grp)
946 Sets a feeder/generator on this group: every group can have an
947 attached generator that generates requests if idle. The idea behind
948 this is that, although you could just queue as many requests as you
949 want in a group, this might starve other requests for a potentially
950 long time. For example, "aio_scandir" might generate hundreds of
951 thousands "aio_stat" requests, delaying any later requests for a
952 long time.
953
954 To avoid this, and allow incremental generation of requests, you can
955 instead a group and set a feeder on it that generates those
956 requests. The feed callback will be called whenever there are few
957 enough (see "limit", below) requests active in the group itself and
958 is expected to queue more requests.
959
960 The feed callback can queue as many requests as it likes (i.e. "add"
961 does not impose any limits).
962
963 If the feed does not queue more requests when called, it will be
964 automatically removed from the group.
965
966 If the feed limit is 0 when this method is called, it will be set to
967 2 automatically.
968
969 Example:
970
971 # stat all files in @files, but only ever use four aio requests concurrently:
972
973 my $grp = aio_group sub { print "finished\n" };
974 limit $grp 4;
975 feed $grp sub {
976 my $file = pop @files
977 or return;
978
979 add $grp aio_stat $file, sub { ... };
980 };
981
982 limit $grp $num
983 Sets the feeder limit for the group: The feeder will be called
984 whenever the group contains less than this many requests.
985
986 Setting the limit to 0 will pause the feeding process.
987
988 The default value for the limit is 0, but note that setting a feeder
989 automatically bumps it up to 2.
990
991 SUPPORT FUNCTIONS
992 EVENT PROCESSING AND EVENT LOOP INTEGRATION
993 $fileno = IO::AIO::poll_fileno
994 Return the *request result pipe file descriptor*. This filehandle
995 must be polled for reading by some mechanism outside this module
996 (e.g. EV, Glib, select and so on, see below or the SYNOPSIS). If the
997 pipe becomes readable you have to call "poll_cb" to check the
998 results.
999
1000 See "poll_cb" for an example.
1001
1002 IO::AIO::poll_cb
1003 Process some outstanding events on the result pipe. You have to call
1004 this regularly. Returns 0 if all events could be processed, or -1 if
1005 it returned earlier for whatever reason. Returns immediately when no
1006 events are outstanding. The amount of events processed depends on
1007 the settings of "IO::AIO::max_poll_req" and
1008 "IO::AIO::max_poll_time".
1009
1010 If not all requests were processed for whatever reason, the
1011 filehandle will still be ready when "poll_cb" returns, so normally
1012 you don't have to do anything special to have it called later.
1013
1014 Example: Install an Event watcher that automatically calls
1015 IO::AIO::poll_cb with high priority (more examples can be found in
1016 the SYNOPSIS section, at the top of this document):
1017
1018 Event->io (fd => IO::AIO::poll_fileno,
1019 poll => 'r', async => 1,
1020 cb => \&IO::AIO::poll_cb);
1021
1022 IO::AIO::poll_wait
1023 If there are any outstanding requests and none of them in the result
1024 phase, wait till the result filehandle becomes ready for reading
1025 (simply does a "select" on the filehandle. This is useful if you
1026 want to synchronously wait for some requests to finish).
1027
1028 See "nreqs" for an example.
1029
1030 IO::AIO::poll
1031 Waits until some requests have been handled.
1032
1033 Returns the number of requests processed, but is otherwise strictly
1034 equivalent to:
1035
1036 IO::AIO::poll_wait, IO::AIO::poll_cb
1037
1038 IO::AIO::flush
1039 Wait till all outstanding AIO requests have been handled.
1040
1041 Strictly equivalent to:
1042
1043 IO::AIO::poll_wait, IO::AIO::poll_cb
1044 while IO::AIO::nreqs;
1045
1046 IO::AIO::max_poll_reqs $nreqs
1047 IO::AIO::max_poll_time $seconds
1048 These set the maximum number of requests (default 0, meaning
1049 infinity) that are being processed by "IO::AIO::poll_cb" in one
1050 call, respectively the maximum amount of time (default 0, meaning
1051 infinity) spent in "IO::AIO::poll_cb" to process requests (more
1052 correctly the mininum amount of time "poll_cb" is allowed to use).
1053
1054 Setting "max_poll_time" to a non-zero value creates an overhead of
1055 one syscall per request processed, which is not normally a problem
1056 unless your callbacks are really really fast or your OS is really
1057 really slow (I am not mentioning Solaris here). Using
1058 "max_poll_reqs" incurs no overhead.
1059
1060 Setting these is useful if you want to ensure some level of
1061 interactiveness when perl is not fast enough to process all requests
1062 in time.
1063
1064 For interactive programs, values such as 0.01 to 0.1 should be fine.
1065
1066 Example: Install an Event watcher that automatically calls
1067 IO::AIO::poll_cb with low priority, to ensure that other parts of
1068 the program get the CPU sometimes even under high AIO load.
1069
1070 # try not to spend much more than 0.1s in poll_cb
1071 IO::AIO::max_poll_time 0.1;
1072
1073 # use a low priority so other tasks have priority
1074 Event->io (fd => IO::AIO::poll_fileno,
1075 poll => 'r', nice => 1,
1076 cb => &IO::AIO::poll_cb);
1077
1078 CONTROLLING THE NUMBER OF THREADS
1079 IO::AIO::min_parallel $nthreads
1080 Set the minimum number of AIO threads to $nthreads. The current
1081 default is 8, which means eight asynchronous operations can execute
1082 concurrently at any one time (the number of outstanding requests,
1083 however, is unlimited).
1084
1085 IO::AIO starts threads only on demand, when an AIO request is queued
1086 and no free thread exists. Please note that queueing up a hundred
1087 requests can create demand for a hundred threads, even if it turns
1088 out that everything is in the cache and could have been processed
1089 faster by a single thread.
1090
1091 It is recommended to keep the number of threads relatively low, as
1092 some Linux kernel versions will scale negatively with the number of
1093 threads (higher parallelity => MUCH higher latency). With current
1094 Linux 2.6 versions, 4-32 threads should be fine.
1095
1096 Under most circumstances you don't need to call this function, as
1097 the module selects a default that is suitable for low to moderate
1098 load.
1099
1100 IO::AIO::max_parallel $nthreads
1101 Sets the maximum number of AIO threads to $nthreads. If more than
1102 the specified number of threads are currently running, this function
1103 kills them. This function blocks until the limit is reached.
1104
1105 While $nthreads are zero, aio requests get queued but not executed
1106 until the number of threads has been increased again.
1107
1108 This module automatically runs "max_parallel 0" at program end, to
1109 ensure that all threads are killed and that there are no outstanding
495 requests. 1110 requests.
496 1111
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. 1112 Under normal circumstances you don't need to call this function.
701 1113
1114 IO::AIO::max_idle $nthreads
1115 Limit the number of threads (default: 4) that are allowed to idle
1116 (i.e., threads that did not get a request to process within 10
1117 seconds). That means if a thread becomes idle while $nthreads other
1118 threads are also idle, it will free its resources and exit.
1119
1120 This is useful when you allow a large number of threads (e.g. 100 or
1121 1000) to allow for extremely high load situations, but want to free
1122 resources under normal circumstances (1000 threads can easily
1123 consume 30MB of RAM).
1124
1125 The default is probably ok in most situations, especially if thread
1126 creation is fast. If thread creation is very slow on your system you
1127 might want to use larger values.
1128
702 $oldmaxreqs = IO::AIO::max_outstanding $maxreqs 1129 IO::AIO::max_outstanding $maxreqs
703 This is a very bad function to use in interactive programs 1130 This is a very bad function to use in interactive programs because
704 because it blocks, and a bad way to reduce concurrency because 1131 it blocks, and a bad way to reduce concurrency because it is
705 it is inexact: Better use an "aio_group" together with a feed 1132 inexact: Better use an "aio_group" together with a feed callback.
706 callback.
707 1133
708 Sets the maximum number of outstanding requests to $nreqs. If 1134 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 1135 queue up more than this number of requests, the next call to the
710 to the "poll_cb" (and "poll_some" and other functions calling 1136 "poll_cb" (and "poll_some" and other functions calling "poll_cb")
711 "poll_cb") function will block until the limit is no longer 1137 function will block until the limit is no longer exceeded.
712 exceeded.
713 1138
714 The default value is very large, so there is no practical limit 1139 The default value is very large, so there is no practical limit on
715 on the number of outstanding requests. 1140 the number of outstanding requests.
716 1141
717 You can still queue as many requests as you want. Therefore, 1142 You can still queue as many requests as you want. Therefore,
718 "max_oustsanding" is mainly useful in simple scripts (with low 1143 "max_outstanding" is mainly useful in simple scripts (with low
719 values) or as a stop gap to shield against fatal memory overflow 1144 values) or as a stop gap to shield against fatal memory overflow
720 (with large values). 1145 (with large values).
1146
1147 STATISTICAL INFORMATION
1148 IO::AIO::nreqs
1149 Returns the number of requests currently in the ready, execute or
1150 pending states (i.e. for which their callback has not been invoked
1151 yet).
1152
1153 Example: wait till there are no outstanding requests anymore:
1154
1155 IO::AIO::poll_wait, IO::AIO::poll_cb
1156 while IO::AIO::nreqs;
1157
1158 IO::AIO::nready
1159 Returns the number of requests currently in the ready state (not yet
1160 executed).
1161
1162 IO::AIO::npending
1163 Returns the number of requests currently in the pending state
1164 (executed, but not yet processed by poll_cb).
1165
1166 MISCELLANEOUS FUNCTIONS
1167 IO::AIO implements some functions that might be useful, but are not
1168 asynchronous.
1169
1170 IO::AIO::sendfile $ofh, $ifh, $offset, $count
1171 Calls the "eio_sendfile_sync" function, which is like
1172 "aio_sendfile", but is blocking (this makes most sense if you know
1173 the input data is likely cached already and the output filehandle is
1174 set to non-blocking operations).
1175
1176 Returns the number of bytes copied, or -1 on error.
1177
1178 IO::AIO::fadvise $fh, $offset, $len, $advice
1179 Simply calls the "posix_fadvise" function (see its manpage for
1180 details). The following advice constants are avaiable:
1181 "IO::AIO::FADV_NORMAL", "IO::AIO::FADV_SEQUENTIAL",
1182 "IO::AIO::FADV_RANDOM", "IO::AIO::FADV_NOREUSE",
1183 "IO::AIO::FADV_WILLNEED", "IO::AIO::FADV_DONTNEED".
1184
1185 On systems that do not implement "posix_fadvise", this function
1186 returns ENOSYS, otherwise the return value of "posix_fadvise".
1187
1188 IO::AIO::madvise $scalar, $offset, $len, $advice
1189 Simply calls the "posix_madvise" function (see its manpage for
1190 details). The following advice constants are avaiable:
1191 "IO::AIO::MADV_NORMAL", "IO::AIO::MADV_SEQUENTIAL",
1192 "IO::AIO::MADV_RANDOM", "IO::AIO::MADV_WILLNEED",
1193 "IO::AIO::MADV_DONTNEED".
1194
1195 On systems that do not implement "posix_madvise", this function
1196 returns ENOSYS, otherwise the return value of "posix_madvise".
1197
1198 IO::AIO::mprotect $scalar, $offset, $len, $protect
1199 Simply calls the "mprotect" function on the preferably AIO::mmap'ed
1200 $scalar (see its manpage for details). The following protect
1201 constants are avaiable: "IO::AIO::PROT_NONE", "IO::AIO::PROT_READ",
1202 "IO::AIO::PROT_WRITE", "IO::AIO::PROT_EXEC".
1203
1204 On systems that do not implement "mprotect", this function returns
1205 ENOSYS, otherwise the return value of "mprotect".
1206
1207 IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
1208 Memory-maps a file (or anonymous memory range) and attaches it to
1209 the given $scalar, which will act like a string scalar.
1210
1211 The only operations allowed on the scalar are "substr"/"vec" that
1212 don't change the string length, and most read-only operations such
1213 as copying it or searching it with regexes and so on.
1214
1215 Anything else is unsafe and will, at best, result in memory leaks.
1216
1217 The memory map associated with the $scalar is automatically removed
1218 when the $scalar is destroyed, or when the "IO::AIO::mmap" or
1219 "IO::AIO::munmap" functions are called.
1220
1221 This calls the "mmap"(2) function internally. See your system's
1222 manual page for details on the $length, $prot and $flags parameters.
1223
1224 The $length must be larger than zero and smaller than the actual
1225 filesize.
1226
1227 $prot is a combination of "IO::AIO::PROT_NONE",
1228 "IO::AIO::PROT_EXEC", "IO::AIO::PROT_READ" and/or
1229 "IO::AIO::PROT_WRITE",
1230
1231 $flags can be a combination of "IO::AIO::MAP_SHARED" or
1232 "IO::AIO::MAP_PRIVATE", or a number of system-specific flags (when
1233 not available, the are defined as 0): "IO::AIO::MAP_ANONYMOUS"
1234 (which is set to "MAP_ANON" if your system only provides this
1235 constant), "IO::AIO::MAP_HUGETLB", "IO::AIO::MAP_LOCKED",
1236 "IO::AIO::MAP_NORESERVE", "IO::AIO::MAP_POPULATE" or
1237 "IO::AIO::MAP_NONBLOCK"
1238
1239 If $fh is "undef", then a file descriptor of -1 is passed.
1240
1241 $offset is the offset from the start of the file - it generally must
1242 be a multiple of "IO::AIO::PAGESIZE" and defaults to 0.
1243
1244 Example:
1245
1246 use Digest::MD5;
1247 use IO::AIO;
1248
1249 open my $fh, "<verybigfile"
1250 or die "$!";
1251
1252 IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
1253 or die "verybigfile: $!";
1254
1255 my $fast_md5 = md5 $data;
1256
1257 IO::AIO::munmap $scalar
1258 Removes a previous mmap and undefines the $scalar.
1259
1260 IO::AIO::munlock $scalar, $offset = 0, $length = undef
1261 Calls the "munlock" function, undoing the effects of a previous
1262 "aio_mlock" call (see its description for details).
1263
1264 IO::AIO::munlockall
1265 Calls the "munlockall" function.
1266
1267 On systems that do not implement "munlockall", this function returns
1268 ENOSYS, otherwise the return value of "munlockall".
1269
1270EVENT LOOP INTEGRATION
1271 It is recommended to use AnyEvent::AIO to integrate IO::AIO
1272 automatically into many event loops:
1273
1274 # AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
1275 use AnyEvent::AIO;
1276
1277 You can also integrate IO::AIO manually into many event loops, here are
1278 some examples of how to do this:
1279
1280 # EV integration
1281 my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
1282
1283 # Event integration
1284 Event->io (fd => IO::AIO::poll_fileno,
1285 poll => 'r',
1286 cb => \&IO::AIO::poll_cb);
1287
1288 # Glib/Gtk2 integration
1289 add_watch Glib::IO IO::AIO::poll_fileno,
1290 in => sub { IO::AIO::poll_cb; 1 };
1291
1292 # Tk integration
1293 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
1294 readable => \&IO::AIO::poll_cb);
1295
1296 # Danga::Socket integration
1297 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
1298 \&IO::AIO::poll_cb);
721 1299
722 FORK BEHAVIOUR 1300 FORK BEHAVIOUR
723 This module should do "the right thing" when the process using it 1301 This module should do "the right thing" when the process using it forks:
724 forks:
725 1302
726 Before the fork, IO::AIO enters a quiescent state where no requests 1303 Before the fork, IO::AIO enters a quiescent state where no requests can
727 can be added in other threads and no results will be processed. 1304 be added in other threads and no results will be processed. After the
728 After the fork the parent simply leaves the quiescent state and 1305 fork the parent simply leaves the quiescent state and continues
729 continues request/result processing, while the child frees the 1306 request/result processing, while the child frees the request/result
730 request/result queue (so that the requests started before the fork 1307 queue (so that the requests started before the fork will only be handled
731 will only be handled in the parent). Threads will be started on 1308 in the parent). Threads will be started on demand until the limit set in
732 demand until the limit set in the parent process has been reached 1309 the parent process has been reached again.
733 again.
734 1310
735 In short: the parent will, after a short pause, continue as if fork 1311 In short: the parent will, after a short pause, continue as if fork had
736 had not been called, while the child will act as if IO::AIO has not 1312 not been called, while the child will act as if IO::AIO has not been
737 been used yet. 1313 used yet.
738 1314
739 MEMORY USAGE 1315 MEMORY USAGE
740 Per-request usage: 1316 Per-request usage:
741 1317
742 Each aio request uses - depending on your architecture - around 1318 Each aio request uses - depending on your architecture - around 100-200
743 100-200 bytes of memory. In addition, stat requests need a stat 1319 bytes of memory. In addition, stat requests need a stat buffer (possibly
744 buffer (possibly a few hundred bytes), readdir requires a result 1320 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 1321 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 1322 will consume memory till the request has entered the done state.
747 request has entered the done state.
748 1323
749 This is now awfully much, so queuing lots of requests is not usually 1324 This is not awfully much, so queuing lots of requests is not usually a
750 a problem. 1325 problem.
751 1326
752 Per-thread usage: 1327 Per-thread usage:
753 1328
754 In the execution phase, some aio requests require more memory for 1329 In the execution phase, some aio requests require more memory for
755 temporary buffers, and each thread requires a stack and other data 1330 temporary buffers, and each thread requires a stack and other data
756 structures (usually around 16k-128k, depending on the OS). 1331 structures (usually around 16k-128k, depending on the OS).
757 1332
758KNOWN BUGS 1333KNOWN BUGS
759 Known bugs will be fixed in the next release. 1334 Known bugs will be fixed in the next release.
760 1335
761SEE ALSO 1336SEE ALSO
762 Coro::AIO. 1337 AnyEvent::AIO for easy integration into event loops, Coro::AIO for a
1338 more natural syntax.
763 1339
764AUTHOR 1340AUTHOR
765 Marc Lehmann <schmorp@schmorp.de> 1341 Marc Lehmann <schmorp@schmorp.de>
766 http://home.schmorp.de/ 1342 http://home.schmorp.de/
767 1343

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