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Revision 1.47 by root, Fri May 27 00:44:49 2011 UTC

… …
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::idle_timeout $seconds
210 IO::AIO::max_outstanding $maxreqs
211 IO::AIO::nreqs
212 IO::AIO::nready
213 IO::AIO::npending
442 214
443 While it is theoretically handy to have simple I/O scheduling 215 IO::AIO::sendfile $ofh, $ifh, $offset, $count
444 requests like sleep and file handle readable/writable, the 216 IO::AIO::fadvise $fh, $offset, $len, $advice
445 overhead this creates is immense (it blocks a thread for a long 217 IO::AIO::madvise $scalar, $offset, $length, $advice
446 time) so do not use this function except to put your application 218 IO::AIO::mprotect $scalar, $offset, $length, $protect
447 under artificial I/O pressure. 219 IO::AIO::munlock $scalar, $offset = 0, $length = undef
220 IO::AIO::munlockall
448 221
449 IO::AIO::REQ CLASS 222 AIO REQUEST FUNCTIONS
450 All non-aggregate "aio_*" functions return an object of this class 223 All the "aio_*" calls are more or less thin wrappers around the syscall
451 when called in non-void context. 224 with the same name (sans "aio_"). The arguments are similar or
225 identical, and they all accept an additional (and optional) $callback
226 argument which must be a code reference. This code reference will get
227 called with the syscall return code (e.g. most syscalls return -1 on
228 error, unlike perl, which usually delivers "false") as its sole argument
229 after the given syscall has been executed asynchronously.
452 230
453 cancel $req 231 All functions expecting a filehandle keep a copy of the filehandle
454 Cancels the request, if possible. Has the effect of skipping 232 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.
460 233
461 cb $req $callback->(...) 234 All functions return request objects of type IO::AIO::REQ that allow
462 Replace (or simply set) the callback registered to the request. 235 further manipulation of those requests while they are in-flight.
463 236
464 IO::AIO::GRP CLASS 237 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 238 as octets. The reason for the former is that at the time the request is
466 to objects of this class, too. 239 being executed, the current working directory could have changed.
240 Alternatively, you can make sure that you never change the current
241 working directory anywhere in the program and then use relative paths.
467 242
468 A IO::AIO::GRP object is a special request that can contain multiple 243 To encode pathnames as octets, either make sure you either: a) always
469 other aio requests. 244 pass in filenames you got from outside (command line, readdir etc.)
245 without tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module
246 and encode your pathnames to the locale (or other) encoding in effect in
247 the user environment, d) use Glib::filename_from_unicode on unicode
248 filenames or e) use something else to ensure your scalar has the correct
249 contents.
470 250
471 You create one by calling the "aio_group" constructing function with 251 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 252 handles correctly whether it is set or not.
473 entered the "done" state:
474 253
475 my $grp = aio_group sub { 254 $prev_pri = aioreq_pri [$pri]
476 print "all requests are done\n"; 255 Returns the priority value that would be used for the next request
477 }; 256 and, if $pri is given, sets the priority for the next aio request.
478 257
479 You add requests by calling the "add" method with one or more 258 The default priority is 0, the minimum and maximum priorities are -4
480 "IO::AIO::REQ" objects: 259 and 4, respectively. Requests with higher priority will be serviced
260 first.
481 261
482 $grp->add (aio_unlink "..."); 262 The priority will be reset to 0 after each call to one of the
263 "aio_*" functions.
483 264
484 add $grp aio_stat "...", sub { 265 Example: open a file with low priority, then read something from it
485 $_[0] or return $grp->result ("error"); 266 with higher priority so the read request is serviced before other
267 low priority open requests (potentially spamming the cache):
486 268
487 # add another request dynamically, if first succeeded 269 aioreq_pri -3;
488 add $grp aio_open "...", sub { 270 aio_open ..., sub {
489 $grp->result ("ok"); 271 return unless $_[0];
272
273 aioreq_pri -2;
274 aio_read $_[0], ..., sub {
275 ...
490 }; 276 };
491 }; 277 };
492 278
279 aioreq_nice $pri_adjust
280 Similar to "aioreq_pri", but subtracts the given value from the
281 current priority, so the effect is cumulative.
282
283 aio_open $pathname, $flags, $mode, $callback->($fh)
284 Asynchronously open or create a file and call the callback with a
285 newly created filehandle for the file.
286
287 The pathname passed to "aio_open" must be absolute. See API NOTES,
288 above, for an explanation.
289
290 The $flags argument is a bitmask. See the "Fcntl" module for a list.
291 They are the same as used by "sysopen".
292
293 Likewise, $mode specifies the mode of the newly created file, if it
294 didn't exist and "O_CREAT" has been given, just like perl's
295 "sysopen", except that it is mandatory (i.e. use 0 if you don't
296 create new files, and 0666 or 0777 if you do). Note that the $mode
297 will be modified by the umask in effect then the request is being
298 executed, so better never change the umask.
299
300 Example:
301
302 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
303 if ($_[0]) {
304 print "open successful, fh is $_[0]\n";
305 ...
306 } else {
307 die "open failed: $!\n";
308 }
309 };
310
311 In addition to all the common open modes/flags ("O_RDONLY",
312 "O_WRONLY", "O_RDWR", "O_CREAT", "O_TRUNC", "O_EXCL" and
313 "O_APPEND"), the following POSIX and non-POSIX constants are
314 available (missing ones on your system are, as usual, 0):
315
316 "O_ASYNC", "O_DIRECT", "O_NOATIME", "O_CLOEXEC", "O_NOCTTY",
317 "O_NOFOLLOW", "O_NONBLOCK", "O_EXEC", "O_SEARCH", "O_DIRECTORY",
318 "O_DSYNC", "O_RSYNC", "O_SYNC" and "O_TTY_INIT".
319
320 aio_close $fh, $callback->($status)
321 Asynchronously close a file and call the callback with the result
322 code.
323
324 Unfortunately, you can't do this to perl. Perl *insists* very
325 strongly on closing the file descriptor associated with the
326 filehandle itself.
327
328 Therefore, "aio_close" will not close the filehandle - instead it
329 will use dup2 to overwrite the file descriptor with the write-end of
330 a pipe (the pipe fd will be created on demand and will be cached).
331
332 Or in other words: the file descriptor will be closed, but it will
333 not be free for reuse until the perl filehandle is closed.
334
335 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
336 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
337 Reads or writes $length bytes from or to the specified $fh and
338 $offset into the scalar given by $data and offset $dataoffset and
339 calls the callback without the actual number of bytes read (or -1 on
340 error, just like the syscall).
341
342 "aio_read" will, like "sysread", shrink or grow the $data scalar to
343 offset plus the actual number of bytes read.
344
345 If $offset is undefined, then the current file descriptor offset
346 will be used (and updated), otherwise the file descriptor offset
347 will not be changed by these calls.
348
349 If $length is undefined in "aio_write", use the remaining length of
350 $data.
351
352 If $dataoffset is less than zero, it will be counted from the end of
353 $data.
354
355 The $data scalar *MUST NOT* be modified in any way while the request
356 is outstanding. Modifying it can result in segfaults or World War
357 III (if the necessary/optional hardware is installed).
358
359 Example: Read 15 bytes at offset 7 into scalar $buffer, starting at
360 offset 0 within the scalar:
361
362 aio_read $fh, 7, 15, $buffer, 0, sub {
363 $_[0] > 0 or die "read error: $!";
364 print "read $_[0] bytes: <$buffer>\n";
365 };
366
367 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
368 Tries to copy $length bytes from $in_fh to $out_fh. It starts
369 reading at byte offset $in_offset, and starts writing at the current
370 file offset of $out_fh. Because of that, it is not safe to issue
371 more than one "aio_sendfile" per $out_fh, as they will interfere
372 with each other.
373
374 Please note that "aio_sendfile" can read more bytes from $in_fh than
375 are written, and there is no way to find out how many bytes have
376 been read from "aio_sendfile" alone, as "aio_sendfile" only provides
377 the number of bytes written to $out_fh. Only if the result value
378 equals $length one can assume that $length bytes have been read.
379
380 Unlike with other "aio_" functions, it makes a lot of sense to use
381 "aio_sendfile" on non-blocking sockets, as long as one end
382 (typically the $in_fh) is a file - the file I/O will then be
383 asynchronous, while the socket I/O will be non-blocking. Note,
384 however, that you can run into a trap where "aio_sendfile" reads
385 some data with readahead, then fails to write all data, and when the
386 socket is ready the next time, the data in the cache is already
387 lost, forcing "aio_sendfile" to again hit the disk. Explicit
388 "aio_read" + "aio_write" let's you control resource usage much
389 better.
390
391 This call tries to make use of a native "sendfile" syscall to
392 provide zero-copy operation. For this to work, $out_fh should refer
393 to a socket, and $in_fh should refer to an mmap'able file.
394
395 If a native sendfile cannot be found or it fails with "ENOSYS",
396 "ENOTSUP", "EOPNOTSUPP", "EAFNOSUPPORT", "EPROTOTYPE" or "ENOTSOCK",
397 it will be emulated, so you can call "aio_sendfile" on any type of
398 filehandle regardless of the limitations of the operating system.
399
400 aio_readahead $fh,$offset,$length, $callback->($retval)
401 "aio_readahead" populates the page cache with data from a file so
402 that subsequent reads from that file will not block on disk I/O. The
403 $offset argument specifies the starting point from which data is to
404 be read and $length specifies the number of bytes to be read. I/O is
405 performed in whole pages, so that offset is effectively rounded down
406 to a page boundary and bytes are read up to the next page boundary
407 greater than or equal to (off-set+length). "aio_readahead" does not
408 read beyond the end of the file. The current file offset of the file
409 is left unchanged.
410
411 If that syscall doesn't exist (likely if your OS isn't Linux) it
412 will be emulated by simply reading the data, which would have a
413 similar effect.
414
415 aio_stat $fh_or_path, $callback->($status)
416 aio_lstat $fh, $callback->($status)
417 Works like perl's "stat" or "lstat" in void context. The callback
418 will be called after the stat and the results will be available
419 using "stat _" or "-s _" etc...
420
421 The pathname passed to "aio_stat" must be absolute. See API NOTES,
422 above, for an explanation.
423
424 Currently, the stats are always 64-bit-stats, i.e. instead of
425 returning an error when stat'ing a large file, the results will be
426 silently truncated unless perl itself is compiled with large file
427 support.
428
429 To help interpret the mode and dev/rdev stat values, IO::AIO offers
430 the following constants and functions (if not implemented, the
431 constants will be 0 and the functions will either "croak" or fall
432 back on traditional behaviour).
433
434 "S_IFMT", "S_IFIFO", "S_IFCHR", "S_IFBLK", "S_IFLNK", "S_IFREG",
435 "S_IFDIR", "S_IFWHT", "S_IFSOCK", "IO::AIO::major $dev_t",
436 "IO::AIO::minor $dev_t", "IO::AIO::makedev $major, $minor".
437
438 Example: Print the length of /etc/passwd:
439
440 aio_stat "/etc/passwd", sub {
441 $_[0] and die "stat failed: $!";
442 print "size is ", -s _, "\n";
443 };
444
445 aio_statvfs $fh_or_path, $callback->($statvfs)
446 Works like the POSIX "statvfs" or "fstatvfs" syscalls, depending on
447 whether a file handle or path was passed.
448
449 On success, the callback is passed a hash reference with the
450 following members: "bsize", "frsize", "blocks", "bfree", "bavail",
451 "files", "ffree", "favail", "fsid", "flag" and "namemax". On
452 failure, "undef" is passed.
453
454 The following POSIX IO::AIO::ST_* constants are defined: "ST_RDONLY"
455 and "ST_NOSUID".
456
457 The following non-POSIX IO::AIO::ST_* flag masks are defined to
458 their correct value when available, or to 0 on systems that do not
459 support them: "ST_NODEV", "ST_NOEXEC", "ST_SYNCHRONOUS",
460 "ST_MANDLOCK", "ST_WRITE", "ST_APPEND", "ST_IMMUTABLE",
461 "ST_NOATIME", "ST_NODIRATIME" and "ST_RELATIME".
462
463 Example: stat "/wd" and dump out the data if successful.
464
465 aio_statvfs "/wd", sub {
466 my $f = $_[0]
467 or die "statvfs: $!";
468
469 use Data::Dumper;
470 say Dumper $f;
471 };
472
473 # result:
474 {
475 bsize => 1024,
476 bfree => 4333064312,
477 blocks => 10253828096,
478 files => 2050765568,
479 flag => 4096,
480 favail => 2042092649,
481 bavail => 4333064312,
482 ffree => 2042092649,
483 namemax => 255,
484 frsize => 1024,
485 fsid => 1810
486 }
487
488 aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
489 Works like perl's "utime" function (including the special case of
490 $atime and $mtime being undef). Fractional times are supported if
491 the underlying syscalls support them.
492
493 When called with a pathname, uses utimes(2) if available, otherwise
494 utime(2). If called on a file descriptor, uses futimes(2) if
495 available, otherwise returns ENOSYS, so this is not portable.
496
497 Examples:
498
499 # set atime and mtime to current time (basically touch(1)):
500 aio_utime "path", undef, undef;
501 # set atime to current time and mtime to beginning of the epoch:
502 aio_utime "path", time, undef; # undef==0
503
504 aio_chown $fh_or_path, $uid, $gid, $callback->($status)
505 Works like perl's "chown" function, except that "undef" for either
506 $uid or $gid is being interpreted as "do not change" (but -1 can
507 also be used).
508
509 Examples:
510
511 # same as "chown root path" in the shell:
512 aio_chown "path", 0, -1;
513 # same as above:
514 aio_chown "path", 0, undef;
515
516 aio_truncate $fh_or_path, $offset, $callback->($status)
517 Works like truncate(2) or ftruncate(2).
518
519 aio_chmod $fh_or_path, $mode, $callback->($status)
520 Works like perl's "chmod" function.
521
522 aio_unlink $pathname, $callback->($status)
523 Asynchronously unlink (delete) a file and call the callback with the
524 result code.
525
526 aio_mknod $path, $mode, $dev, $callback->($status)
527 [EXPERIMENTAL]
528
529 Asynchronously create a device node (or fifo). See mknod(2).
530
531 The only (POSIX-) portable way of calling this function is:
532
533 aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...
534
535 See "aio_stat" for info about some potentially helpful extra
536 constants and functions.
537
538 aio_link $srcpath, $dstpath, $callback->($status)
539 Asynchronously create a new link to the existing object at $srcpath
540 at the path $dstpath and call the callback with the result code.
541
542 aio_symlink $srcpath, $dstpath, $callback->($status)
543 Asynchronously create a new symbolic link to the existing object at
544 $srcpath at the path $dstpath and call the callback with the result
545 code.
546
547 aio_readlink $path, $callback->($link)
548 Asynchronously read the symlink specified by $path and pass it to
549 the callback. If an error occurs, nothing or undef gets passed to
550 the callback.
551
552 aio_rename $srcpath, $dstpath, $callback->($status)
553 Asynchronously rename the object at $srcpath to $dstpath, just as
554 rename(2) and call the callback with the result code.
555
556 aio_mkdir $pathname, $mode, $callback->($status)
557 Asynchronously mkdir (create) a directory and call the callback with
558 the result code. $mode will be modified by the umask at the time the
559 request is executed, so do not change your umask.
560
561 aio_rmdir $pathname, $callback->($status)
562 Asynchronously rmdir (delete) a directory and call the callback with
563 the result code.
564
565 aio_readdir $pathname, $callback->($entries)
566 Unlike the POSIX call of the same name, "aio_readdir" reads an
567 entire directory (i.e. opendir + readdir + closedir). The entries
568 will not be sorted, and will NOT include the "." and ".." entries.
569
570 The callback is passed a single argument which is either "undef" or
571 an array-ref with the filenames.
572
573 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
574 Quite similar to "aio_readdir", but the $flags argument allows to
575 tune behaviour and output format. In case of an error, $entries will
576 be "undef".
577
578 The flags are a combination of the following constants, ORed
579 together (the flags will also be passed to the callback, possibly
580 modified):
581
582 IO::AIO::READDIR_DENTS
583 When this flag is off, then the callback gets an arrayref
584 consisting of names only (as with "aio_readdir"), otherwise it
585 gets an arrayref with "[$name, $type, $inode]" arrayrefs, each
586 describing a single directory entry in more detail.
587
588 $name is the name of the entry.
589
590 $type is one of the "IO::AIO::DT_xxx" constants:
591
592 "IO::AIO::DT_UNKNOWN", "IO::AIO::DT_FIFO", "IO::AIO::DT_CHR",
593 "IO::AIO::DT_DIR", "IO::AIO::DT_BLK", "IO::AIO::DT_REG",
594 "IO::AIO::DT_LNK", "IO::AIO::DT_SOCK", "IO::AIO::DT_WHT".
595
596 "IO::AIO::DT_UNKNOWN" means just that: readdir does not know. If
597 you need to know, you have to run stat yourself. Also, for speed
598 reasons, the $type scalars are read-only: you can not modify
599 them.
600
601 $inode is the inode number (which might not be exact on systems
602 with 64 bit inode numbers and 32 bit perls). This field has
603 unspecified content on systems that do not deliver the inode
604 information.
605
606 IO::AIO::READDIR_DIRS_FIRST
607 When this flag is set, then the names will be returned in an
608 order where likely directories come first, in optimal stat
609 order. This is useful when you need to quickly find directories,
610 or you want to find all directories while avoiding to stat()
611 each entry.
612
613 If the system returns type information in readdir, then this is
614 used to find directories directly. Otherwise, likely directories
615 are names beginning with ".", or otherwise names with no dots,
616 of which names with short names are tried first.
617
618 IO::AIO::READDIR_STAT_ORDER
619 When this flag is set, then the names will be returned in an
620 order suitable for stat()'ing each one. That is, when you plan
621 to stat() all files in the given directory, then the returned
622 order will likely be fastest.
623
624 If both this flag and "IO::AIO::READDIR_DIRS_FIRST" are
625 specified, then the likely dirs come first, resulting in a less
626 optimal stat order.
627
628 IO::AIO::READDIR_FOUND_UNKNOWN
629 This flag should not be set when calling "aio_readdirx".
630 Instead, it is being set by "aio_readdirx", when any of the
631 $type's found were "IO::AIO::DT_UNKNOWN". The absense of this
632 flag therefore indicates that all $type's are known, which can
633 be used to speed up some algorithms.
634
635 aio_load $path, $data, $callback->($status)
636 This is a composite request that tries to fully load the given file
637 into memory. Status is the same as with aio_read.
638
639 aio_copy $srcpath, $dstpath, $callback->($status)
640 Try to copy the *file* (directories not supported as either source
641 or destination) from $srcpath to $dstpath and call the callback with
642 a status of 0 (ok) or -1 (error, see $!).
643
644 This is a composite request that creates the destination file with
645 mode 0200 and copies the contents of the source file into it using
646 "aio_sendfile", followed by restoring atime, mtime, access mode and
647 uid/gid, in that order.
648
649 If an error occurs, the partial destination file will be unlinked,
650 if possible, except when setting atime, mtime, access mode and
651 uid/gid, where errors are being ignored.
652
653 aio_move $srcpath, $dstpath, $callback->($status)
654 Try to move the *file* (directories not supported as either source
655 or destination) from $srcpath to $dstpath and call the callback with
656 a status of 0 (ok) or -1 (error, see $!).
657
658 This is a composite request that tries to rename(2) the file first;
659 if rename fails with "EXDEV", it copies the file with "aio_copy"
660 and, if that is successful, unlinks the $srcpath.
661
662 aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
663 Scans a directory (similar to "aio_readdir") but additionally tries
664 to efficiently separate the entries of directory $path into two sets
665 of names, directories you can recurse into (directories), and ones
666 you cannot recurse into (everything else, including symlinks to
667 directories).
668
669 "aio_scandir" is a composite request that creates of many sub
670 requests_ $maxreq specifies the maximum number of outstanding aio
671 requests that this function generates. If it is "<= 0", then a
672 suitable default will be chosen (currently 4).
673
674 On error, the callback is called without arguments, otherwise it
675 receives two array-refs with path-relative entry names.
676
677 Example:
678
679 aio_scandir $dir, 0, sub {
680 my ($dirs, $nondirs) = @_;
681 print "real directories: @$dirs\n";
682 print "everything else: @$nondirs\n";
683 };
684
685 Implementation notes.
686
687 The "aio_readdir" cannot be avoided, but "stat()"'ing every entry
688 can.
689
690 If readdir returns file type information, then this is used directly
691 to find directories.
692
693 Otherwise, after reading the directory, the modification time, size
694 etc. of the directory before and after the readdir is checked, and
695 if they match (and isn't the current time), the link count will be
696 used to decide how many entries are directories (if >= 2).
697 Otherwise, no knowledge of the number of subdirectories will be
698 assumed.
699
700 Then entries will be sorted into likely directories a non-initial
701 dot currently) and likely non-directories (see "aio_readdirx"). Then
702 every entry plus an appended "/." will be "stat"'ed, likely
703 directories first, in order of their inode numbers. If that
704 succeeds, it assumes that the entry is a directory or a symlink to
705 directory (which will be checked seperately). This is often faster
706 than stat'ing the entry itself because filesystems might detect the
707 type of the entry without reading the inode data (e.g. ext2fs
708 filetype feature), even on systems that cannot return the filetype
709 information on readdir.
710
711 If the known number of directories (link count - 2) has been
712 reached, the rest of the entries is assumed to be non-directories.
713
714 This only works with certainty on POSIX (= UNIX) filesystems, which
715 fortunately are the vast majority of filesystems around.
716
717 It will also likely work on non-POSIX filesystems with reduced
718 efficiency as those tend to return 0 or 1 as link counts, which
719 disables the directory counting heuristic.
720
721 aio_rmtree $path, $callback->($status)
722 Delete a directory tree starting (and including) $path, return the
723 status of the final "rmdir" only. This is a composite request that
724 uses "aio_scandir" to recurse into and rmdir directories, and unlink
725 everything else.
726
727 aio_sync $callback->($status)
728 Asynchronously call sync and call the callback when finished.
729
730 aio_fsync $fh, $callback->($status)
731 Asynchronously call fsync on the given filehandle and call the
732 callback with the fsync result code.
733
734 aio_fdatasync $fh, $callback->($status)
735 Asynchronously call fdatasync on the given filehandle and call the
736 callback with the fdatasync result code.
737
738 If this call isn't available because your OS lacks it or it couldn't
739 be detected, it will be emulated by calling "fsync" instead.
740
741 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
742 Sync the data portion of the file specified by $offset and $length
743 to disk (but NOT the metadata), by calling the Linux-specific
744 sync_file_range call. If sync_file_range is not available or it
745 returns ENOSYS, then fdatasync or fsync is being substituted.
746
747 $flags can be a combination of
748 "IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE",
749 "IO::AIO::SYNC_FILE_RANGE_WRITE" and
750 "IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER": refer to the sync_file_range
751 manpage for details.
752
753 aio_pathsync $path, $callback->($status)
754 This request tries to open, fsync and close the given path. This is
755 a composite request intended to sync directories after directory
756 operations (E.g. rename). This might not work on all operating
757 systems or have any specific effect, but usually it makes sure that
758 directory changes get written to disc. It works for anything that
759 can be opened for read-only, not just directories.
760
761 Future versions of this function might fall back to other methods
762 when "fsync" on the directory fails (such as calling "sync").
763
764 Passes 0 when everything went ok, and -1 on error.
765
766 aio_msync $scalar, $offset = 0, $length = undef, flags = 0,
767 $callback->($status)
768 This is a rather advanced IO::AIO call, which only works on
769 mmap(2)ed scalars (see the "IO::AIO::mmap" function, although it
770 also works on data scalars managed by the Sys::Mmap or Mmap modules,
771 note that the scalar must only be modified in-place while an aio
772 operation is pending on it).
773
774 It calls the "msync" function of your OS, if available, with the
775 memory area starting at $offset in the string and ending $length
776 bytes later. If $length is negative, counts from the end, and if
777 $length is "undef", then it goes till the end of the string. The
778 flags can be a combination of "IO::AIO::MS_ASYNC",
779 "IO::AIO::MS_INVALIDATE" and "IO::AIO::MS_SYNC".
780
781 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0,
782 $callback->($status)
783 This is a rather advanced IO::AIO call, which works best on
784 mmap(2)ed scalars.
785
786 It touches (reads or writes) all memory pages in the specified range
787 inside the scalar. All caveats and parameters are the same as for
788 "aio_msync", above, except for flags, which must be either 0 (which
789 reads all pages and ensures they are instantiated) or
790 "IO::AIO::MT_MODIFY", which modifies the memory page s(by reading
791 and writing an octet from it, which dirties the page).
792
793 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
794 This is a rather advanced IO::AIO call, which works best on
795 mmap(2)ed scalars.
796
797 It reads in all the pages of the underlying storage into memory (if
798 any) and locks them, so they are not getting swapped/paged out or
799 removed.
800
801 If $length is undefined, then the scalar will be locked till the
802 end.
803
804 On systems that do not implement "mlock", this function returns -1
805 and sets errno to "ENOSYS".
806
807 Note that the corresponding "munlock" is synchronous and is
808 documented under "MISCELLANEOUS FUNCTIONS".
809
810 Example: open a file, mmap and mlock it - both will be undone when
811 $data gets destroyed.
812
813 open my $fh, "<", $path or die "$path: $!";
814 my $data;
815 IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
816 aio_mlock $data; # mlock in background
817
818 aio_mlockall $flags, $callback->($status)
819 Calls the "mlockall" function with the given $flags (a combination
820 of "IO::AIO::MCL_CURRENT" and "IO::AIO::MCL_FUTURE").
821
822 On systems that do not implement "mlockall", this function returns
823 -1 and sets errno to "ENOSYS".
824
825 Note that the corresponding "munlockall" is synchronous and is
826 documented under "MISCELLANEOUS FUNCTIONS".
827
828 Example: asynchronously lock all current and future pages into
829 memory.
830
831 aio_mlockall IO::AIO::MCL_FUTURE;
832
833 aio_group $callback->(...)
834 This is a very special aio request: Instead of doing something, it
835 is a container for other aio requests, which is useful if you want
836 to bundle many requests into a single, composite, request with a
837 definite callback and the ability to cancel the whole request with
838 its subrequests.
839
840 Returns an object of class IO::AIO::GRP. See its documentation below
841 for more info.
842
843 Example:
844
845 my $grp = aio_group sub {
846 print "all stats done\n";
847 };
848
849 add $grp
850 (aio_stat ...),
851 (aio_stat ...),
852 ...;
853
854 aio_nop $callback->()
855 This is a special request - it does nothing in itself and is only
856 used for side effects, such as when you want to add a dummy request
857 to a group so that finishing the requests in the group depends on
858 executing the given code.
859
860 While this request does nothing, it still goes through the execution
861 phase and still requires a worker thread. Thus, the callback will
862 not be executed immediately but only after other requests in the
863 queue have entered their execution phase. This can be used to
864 measure request latency.
865
866 IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
867 Mainly used for debugging and benchmarking, this aio request puts
868 one of the request workers to sleep for the given time.
869
870 While it is theoretically handy to have simple I/O scheduling
871 requests like sleep and file handle readable/writable, the overhead
872 this creates is immense (it blocks a thread for a long time) so do
873 not use this function except to put your application under
874 artificial I/O pressure.
875
876 IO::AIO::REQ CLASS
877 All non-aggregate "aio_*" functions return an object of this class when
878 called in non-void context.
879
880 cancel $req
881 Cancels the request, if possible. Has the effect of skipping
882 execution when entering the execute state and skipping calling the
883 callback when entering the the result state, but will leave the
884 request otherwise untouched (with the exception of readdir). That
885 means that requests that currently execute will not be stopped and
886 resources held by the request will not be freed prematurely.
887
888 cb $req $callback->(...)
889 Replace (or simply set) the callback registered to the request.
890
891 IO::AIO::GRP CLASS
892 This class is a subclass of IO::AIO::REQ, so all its methods apply to
893 objects of this class, too.
894
895 A IO::AIO::GRP object is a special request that can contain multiple
896 other aio requests.
897
898 You create one by calling the "aio_group" constructing function with a
899 callback that will be called when all contained requests have entered
900 the "done" state:
901
902 my $grp = aio_group sub {
903 print "all requests are done\n";
904 };
905
906 You add requests by calling the "add" method with one or more
907 "IO::AIO::REQ" objects:
908
909 $grp->add (aio_unlink "...");
910
911 add $grp aio_stat "...", sub {
912 $_[0] or return $grp->result ("error");
913
914 # add another request dynamically, if first succeeded
915 add $grp aio_open "...", sub {
916 $grp->result ("ok");
917 };
918 };
919
493 This makes it very easy to create composite requests (see the source 920 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 921 "aio_move" for an application) that work and feel like simple requests.
922
923 * The IO::AIO::GRP objects will be cleaned up during calls to
924 "IO::AIO::poll_cb", just like any other request.
925
926 * They can be canceled like any other request. Canceling will cancel
927 not only the request itself, but also all requests it contains.
928
929 * They can also can also be added to other IO::AIO::GRP objects.
930
931 * You must not add requests to a group from within the group callback
932 (or any later time).
933
934 Their lifetime, simplified, looks like this: when they are empty, they
935 will finish very quickly. If they contain only requests that are in the
936 "done" state, they will also finish. Otherwise they will continue to
937 exist.
938
939 That means after creating a group you have some time to add requests
940 (precisely before the callback has been invoked, which is only done
941 within the "poll_cb"). And in the callbacks of those requests, you can
942 add further requests to the group. And only when all those requests have
943 finished will the the group itself finish.
944
945 add $grp ...
946 $grp->add (...)
947 Add one or more requests to the group. Any type of IO::AIO::REQ can
948 be added, including other groups, as long as you do not create
949 circular dependencies.
950
951 Returns all its arguments.
952
953 $grp->cancel_subs
954 Cancel all subrequests and clears any feeder, but not the group
955 request itself. Useful when you queued a lot of events but got a
956 result early.
957
958 The group request will finish normally (you cannot add requests to
959 the group).
960
961 $grp->result (...)
962 Set the result value(s) that will be passed to the group callback
963 when all subrequests have finished and set the groups errno to the
964 current value of errno (just like calling "errno" without an error
965 number). By default, no argument will be passed and errno is zero.
966
967 $grp->errno ([$errno])
968 Sets the group errno value to $errno, or the current value of errno
969 when the argument is missing.
970
971 Every aio request has an associated errno value that is restored
972 when the callback is invoked. This method lets you change this value
973 from its default (0).
974
975 Calling "result" will also set errno, so make sure you either set $!
976 before the call to "result", or call c<errno> after it.
977
978 feed $grp $callback->($grp)
979 Sets a feeder/generator on this group: every group can have an
980 attached generator that generates requests if idle. The idea behind
981 this is that, although you could just queue as many requests as you
982 want in a group, this might starve other requests for a potentially
983 long time. For example, "aio_scandir" might generate hundreds of
984 thousands "aio_stat" requests, delaying any later requests for a
985 long time.
986
987 To avoid this, and allow incremental generation of requests, you can
988 instead a group and set a feeder on it that generates those
989 requests. The feed callback will be called whenever there are few
990 enough (see "limit", below) requests active in the group itself and
991 is expected to queue more requests.
992
993 The feed callback can queue as many requests as it likes (i.e. "add"
994 does not impose any limits).
995
996 If the feed does not queue more requests when called, it will be
997 automatically removed from the group.
998
999 If the feed limit is 0 when this method is called, it will be set to
1000 2 automatically.
1001
1002 Example:
1003
1004 # stat all files in @files, but only ever use four aio requests concurrently:
1005
1006 my $grp = aio_group sub { print "finished\n" };
1007 limit $grp 4;
1008 feed $grp sub {
1009 my $file = pop @files
1010 or return;
1011
1012 add $grp aio_stat $file, sub { ... };
1013 };
1014
1015 limit $grp $num
1016 Sets the feeder limit for the group: The feeder will be called
1017 whenever the group contains less than this many requests.
1018
1019 Setting the limit to 0 will pause the feeding process.
1020
1021 The default value for the limit is 0, but note that setting a feeder
1022 automatically bumps it up to 2.
1023
1024 SUPPORT FUNCTIONS
1025 EVENT PROCESSING AND EVENT LOOP INTEGRATION
1026 $fileno = IO::AIO::poll_fileno
1027 Return the *request result pipe file descriptor*. This filehandle
1028 must be polled for reading by some mechanism outside this module
1029 (e.g. EV, Glib, select and so on, see below or the SYNOPSIS). If the
1030 pipe becomes readable you have to call "poll_cb" to check the
1031 results.
1032
1033 See "poll_cb" for an example.
1034
1035 IO::AIO::poll_cb
1036 Process some outstanding events on the result pipe. You have to call
1037 this regularly. Returns 0 if all events could be processed (or there
1038 were no events to process), or -1 if it returned earlier for
1039 whatever reason. Returns immediately when no events are outstanding.
1040 The amount of events processed depends on the settings of
1041 "IO::AIO::max_poll_req" and "IO::AIO::max_poll_time".
1042
1043 If not all requests were processed for whatever reason, the
1044 filehandle will still be ready when "poll_cb" returns, so normally
1045 you don't have to do anything special to have it called later.
1046
1047 Apart from calling "IO::AIO::poll_cb" when the event filehandle
1048 becomes ready, it can be beneficial to call this function from loops
1049 which submit a lot of requests, to make sure the results get
1050 processed when they become available and not just when the loop is
1051 finished and the event loop takes over again. This function returns
1052 very fast when there are no outstanding requests.
1053
1054 Example: Install an Event watcher that automatically calls
1055 IO::AIO::poll_cb with high priority (more examples can be found in
1056 the SYNOPSIS section, at the top of this document):
1057
1058 Event->io (fd => IO::AIO::poll_fileno,
1059 poll => 'r', async => 1,
1060 cb => \&IO::AIO::poll_cb);
1061
1062 IO::AIO::poll_wait
1063 If there are any outstanding requests and none of them in the result
1064 phase, wait till the result filehandle becomes ready for reading
1065 (simply does a "select" on the filehandle. This is useful if you
1066 want to synchronously wait for some requests to finish).
1067
1068 See "nreqs" for an example.
1069
1070 IO::AIO::poll
1071 Waits until some requests have been handled.
1072
1073 Returns the number of requests processed, but is otherwise strictly
1074 equivalent to:
1075
1076 IO::AIO::poll_wait, IO::AIO::poll_cb
1077
1078 IO::AIO::flush
1079 Wait till all outstanding AIO requests have been handled.
1080
1081 Strictly equivalent to:
1082
1083 IO::AIO::poll_wait, IO::AIO::poll_cb
1084 while IO::AIO::nreqs;
1085
1086 IO::AIO::max_poll_reqs $nreqs
1087 IO::AIO::max_poll_time $seconds
1088 These set the maximum number of requests (default 0, meaning
1089 infinity) that are being processed by "IO::AIO::poll_cb" in one
1090 call, respectively the maximum amount of time (default 0, meaning
1091 infinity) spent in "IO::AIO::poll_cb" to process requests (more
1092 correctly the mininum amount of time "poll_cb" is allowed to use).
1093
1094 Setting "max_poll_time" to a non-zero value creates an overhead of
1095 one syscall per request processed, which is not normally a problem
1096 unless your callbacks are really really fast or your OS is really
1097 really slow (I am not mentioning Solaris here). Using
1098 "max_poll_reqs" incurs no overhead.
1099
1100 Setting these is useful if you want to ensure some level of
1101 interactiveness when perl is not fast enough to process all requests
1102 in time.
1103
1104 For interactive programs, values such as 0.01 to 0.1 should be fine.
1105
1106 Example: Install an Event watcher that automatically calls
1107 IO::AIO::poll_cb with low priority, to ensure that other parts of
1108 the program get the CPU sometimes even under high AIO load.
1109
1110 # try not to spend much more than 0.1s in poll_cb
1111 IO::AIO::max_poll_time 0.1;
1112
1113 # use a low priority so other tasks have priority
1114 Event->io (fd => IO::AIO::poll_fileno,
1115 poll => 'r', nice => 1,
1116 cb => &IO::AIO::poll_cb);
1117
1118 CONTROLLING THE NUMBER OF THREADS
1119 IO::AIO::min_parallel $nthreads
1120 Set the minimum number of AIO threads to $nthreads. The current
1121 default is 8, which means eight asynchronous operations can execute
1122 concurrently at any one time (the number of outstanding requests,
1123 however, is unlimited).
1124
1125 IO::AIO starts threads only on demand, when an AIO request is queued
1126 and no free thread exists. Please note that queueing up a hundred
1127 requests can create demand for a hundred threads, even if it turns
1128 out that everything is in the cache and could have been processed
1129 faster by a single thread.
1130
1131 It is recommended to keep the number of threads relatively low, as
1132 some Linux kernel versions will scale negatively with the number of
1133 threads (higher parallelity => MUCH higher latency). With current
1134 Linux 2.6 versions, 4-32 threads should be fine.
1135
1136 Under most circumstances you don't need to call this function, as
1137 the module selects a default that is suitable for low to moderate
1138 load.
1139
1140 IO::AIO::max_parallel $nthreads
1141 Sets the maximum number of AIO threads to $nthreads. If more than
1142 the specified number of threads are currently running, this function
1143 kills them. This function blocks until the limit is reached.
1144
1145 While $nthreads are zero, aio requests get queued but not executed
1146 until the number of threads has been increased again.
1147
1148 This module automatically runs "max_parallel 0" at program end, to
1149 ensure that all threads are killed and that there are no outstanding
495 requests. 1150 requests.
496 1151
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. 1152 Under normal circumstances you don't need to call this function.
701 1153
1154 IO::AIO::max_idle $nthreads
1155 Limit the number of threads (default: 4) that are allowed to idle
1156 (i.e., threads that did not get a request to process within the idle
1157 timeout (default: 10 seconds). That means if a thread becomes idle
1158 while $nthreads other threads are also idle, it will free its
1159 resources and exit.
1160
1161 This is useful when you allow a large number of threads (e.g. 100 or
1162 1000) to allow for extremely high load situations, but want to free
1163 resources under normal circumstances (1000 threads can easily
1164 consume 30MB of RAM).
1165
1166 The default is probably ok in most situations, especially if thread
1167 creation is fast. If thread creation is very slow on your system you
1168 might want to use larger values.
1169
1170 IO::AIO::idle_timeout $seconds
1171 Sets the minimum idle timeout (default 10) after which worker
1172 threads are allowed to exit. SEe "IO::AIO::max_idle".
1173
702 $oldmaxreqs = IO::AIO::max_outstanding $maxreqs 1174 IO::AIO::max_outstanding $maxreqs
703 This is a very bad function to use in interactive programs 1175 This is a very bad function to use in interactive programs because
704 because it blocks, and a bad way to reduce concurrency because 1176 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 1177 inexact: Better use an "aio_group" together with a feed callback.
706 callback.
707 1178
708 Sets the maximum number of outstanding requests to $nreqs. If 1179 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 1180 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 1181 "poll_cb" (and "poll_some" and other functions calling "poll_cb")
711 "poll_cb") function will block until the limit is no longer 1182 function will block until the limit is no longer exceeded.
712 exceeded.
713 1183
714 The default value is very large, so there is no practical limit 1184 The default value is very large, so there is no practical limit on
715 on the number of outstanding requests. 1185 the number of outstanding requests.
716 1186
717 You can still queue as many requests as you want. Therefore, 1187 You can still queue as many requests as you want. Therefore,
718 "max_oustsanding" is mainly useful in simple scripts (with low 1188 "max_outstanding" is mainly useful in simple scripts (with low
719 values) or as a stop gap to shield against fatal memory overflow 1189 values) or as a stop gap to shield against fatal memory overflow
720 (with large values). 1190 (with large values).
1191
1192 STATISTICAL INFORMATION
1193 IO::AIO::nreqs
1194 Returns the number of requests currently in the ready, execute or
1195 pending states (i.e. for which their callback has not been invoked
1196 yet).
1197
1198 Example: wait till there are no outstanding requests anymore:
1199
1200 IO::AIO::poll_wait, IO::AIO::poll_cb
1201 while IO::AIO::nreqs;
1202
1203 IO::AIO::nready
1204 Returns the number of requests currently in the ready state (not yet
1205 executed).
1206
1207 IO::AIO::npending
1208 Returns the number of requests currently in the pending state
1209 (executed, but not yet processed by poll_cb).
1210
1211 MISCELLANEOUS FUNCTIONS
1212 IO::AIO implements some functions that might be useful, but are not
1213 asynchronous.
1214
1215 IO::AIO::sendfile $ofh, $ifh, $offset, $count
1216 Calls the "eio_sendfile_sync" function, which is like
1217 "aio_sendfile", but is blocking (this makes most sense if you know
1218 the input data is likely cached already and the output filehandle is
1219 set to non-blocking operations).
1220
1221 Returns the number of bytes copied, or -1 on error.
1222
1223 IO::AIO::fadvise $fh, $offset, $len, $advice
1224 Simply calls the "posix_fadvise" function (see its manpage for
1225 details). The following advice constants are avaiable:
1226 "IO::AIO::FADV_NORMAL", "IO::AIO::FADV_SEQUENTIAL",
1227 "IO::AIO::FADV_RANDOM", "IO::AIO::FADV_NOREUSE",
1228 "IO::AIO::FADV_WILLNEED", "IO::AIO::FADV_DONTNEED".
1229
1230 On systems that do not implement "posix_fadvise", this function
1231 returns ENOSYS, otherwise the return value of "posix_fadvise".
1232
1233 IO::AIO::madvise $scalar, $offset, $len, $advice
1234 Simply calls the "posix_madvise" function (see its manpage for
1235 details). The following advice constants are avaiable:
1236 "IO::AIO::MADV_NORMAL", "IO::AIO::MADV_SEQUENTIAL",
1237 "IO::AIO::MADV_RANDOM", "IO::AIO::MADV_WILLNEED",
1238 "IO::AIO::MADV_DONTNEED".
1239
1240 On systems that do not implement "posix_madvise", this function
1241 returns ENOSYS, otherwise the return value of "posix_madvise".
1242
1243 IO::AIO::mprotect $scalar, $offset, $len, $protect
1244 Simply calls the "mprotect" function on the preferably AIO::mmap'ed
1245 $scalar (see its manpage for details). The following protect
1246 constants are avaiable: "IO::AIO::PROT_NONE", "IO::AIO::PROT_READ",
1247 "IO::AIO::PROT_WRITE", "IO::AIO::PROT_EXEC".
1248
1249 On systems that do not implement "mprotect", this function returns
1250 ENOSYS, otherwise the return value of "mprotect".
1251
1252 IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
1253 Memory-maps a file (or anonymous memory range) and attaches it to
1254 the given $scalar, which will act like a string scalar.
1255
1256 The only operations allowed on the scalar are "substr"/"vec" that
1257 don't change the string length, and most read-only operations such
1258 as copying it or searching it with regexes and so on.
1259
1260 Anything else is unsafe and will, at best, result in memory leaks.
1261
1262 The memory map associated with the $scalar is automatically removed
1263 when the $scalar is destroyed, or when the "IO::AIO::mmap" or
1264 "IO::AIO::munmap" functions are called.
1265
1266 This calls the "mmap"(2) function internally. See your system's
1267 manual page for details on the $length, $prot and $flags parameters.
1268
1269 The $length must be larger than zero and smaller than the actual
1270 filesize.
1271
1272 $prot is a combination of "IO::AIO::PROT_NONE",
1273 "IO::AIO::PROT_EXEC", "IO::AIO::PROT_READ" and/or
1274 "IO::AIO::PROT_WRITE",
1275
1276 $flags can be a combination of "IO::AIO::MAP_SHARED" or
1277 "IO::AIO::MAP_PRIVATE", or a number of system-specific flags (when
1278 not available, the are defined as 0): "IO::AIO::MAP_ANONYMOUS"
1279 (which is set to "MAP_ANON" if your system only provides this
1280 constant), "IO::AIO::MAP_HUGETLB", "IO::AIO::MAP_LOCKED",
1281 "IO::AIO::MAP_NORESERVE", "IO::AIO::MAP_POPULATE" or
1282 "IO::AIO::MAP_NONBLOCK"
1283
1284 If $fh is "undef", then a file descriptor of -1 is passed.
1285
1286 $offset is the offset from the start of the file - it generally must
1287 be a multiple of "IO::AIO::PAGESIZE" and defaults to 0.
1288
1289 Example:
1290
1291 use Digest::MD5;
1292 use IO::AIO;
1293
1294 open my $fh, "<verybigfile"
1295 or die "$!";
1296
1297 IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
1298 or die "verybigfile: $!";
1299
1300 my $fast_md5 = md5 $data;
1301
1302 IO::AIO::munmap $scalar
1303 Removes a previous mmap and undefines the $scalar.
1304
1305 IO::AIO::munlock $scalar, $offset = 0, $length = undef
1306 Calls the "munlock" function, undoing the effects of a previous
1307 "aio_mlock" call (see its description for details).
1308
1309 IO::AIO::munlockall
1310 Calls the "munlockall" function.
1311
1312 On systems that do not implement "munlockall", this function returns
1313 ENOSYS, otherwise the return value of "munlockall".
1314
1315EVENT LOOP INTEGRATION
1316 It is recommended to use AnyEvent::AIO to integrate IO::AIO
1317 automatically into many event loops:
1318
1319 # AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
1320 use AnyEvent::AIO;
1321
1322 You can also integrate IO::AIO manually into many event loops, here are
1323 some examples of how to do this:
1324
1325 # EV integration
1326 my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
1327
1328 # Event integration
1329 Event->io (fd => IO::AIO::poll_fileno,
1330 poll => 'r',
1331 cb => \&IO::AIO::poll_cb);
1332
1333 # Glib/Gtk2 integration
1334 add_watch Glib::IO IO::AIO::poll_fileno,
1335 in => sub { IO::AIO::poll_cb; 1 };
1336
1337 # Tk integration
1338 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
1339 readable => \&IO::AIO::poll_cb);
1340
1341 # Danga::Socket integration
1342 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
1343 \&IO::AIO::poll_cb);
721 1344
722 FORK BEHAVIOUR 1345 FORK BEHAVIOUR
723 This module should do "the right thing" when the process using it 1346 This module should do "the right thing" when the process using it forks:
724 forks:
725 1347
726 Before the fork, IO::AIO enters a quiescent state where no requests 1348 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. 1349 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 1350 fork the parent simply leaves the quiescent state and continues
729 continues request/result processing, while the child frees the 1351 request/result processing, while the child frees the request/result
730 request/result queue (so that the requests started before the fork 1352 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 1353 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 1354 the parent process has been reached again.
733 again.
734 1355
735 In short: the parent will, after a short pause, continue as if fork 1356 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 1357 not been called, while the child will act as if IO::AIO has not been
737 been used yet. 1358 used yet.
738 1359
739 MEMORY USAGE 1360 MEMORY USAGE
740 Per-request usage: 1361 Per-request usage:
741 1362
742 Each aio request uses - depending on your architecture - around 1363 Each aio request uses - depending on your architecture - around 100-200
743 100-200 bytes of memory. In addition, stat requests need a stat 1364 bytes of memory. In addition, stat requests need a stat buffer (possibly
744 buffer (possibly a few hundred bytes), readdir requires a result 1365 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 1366 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 1367 will consume memory till the request has entered the done state.
747 request has entered the done state.
748 1368
749 This is now awfully much, so queuing lots of requests is not usually 1369 This is not awfully much, so queuing lots of requests is not usually a
750 a problem. 1370 problem.
751 1371
752 Per-thread usage: 1372 Per-thread usage:
753 1373
754 In the execution phase, some aio requests require more memory for 1374 In the execution phase, some aio requests require more memory for
755 temporary buffers, and each thread requires a stack and other data 1375 temporary buffers, and each thread requires a stack and other data
756 structures (usually around 16k-128k, depending on the OS). 1376 structures (usually around 16k-128k, depending on the OS).
757 1377
758KNOWN BUGS 1378KNOWN BUGS
759 Known bugs will be fixed in the next release. 1379 Known bugs will be fixed in the next release.
760 1380
761SEE ALSO 1381SEE ALSO
762 Coro::AIO. 1382 AnyEvent::AIO for easy integration into event loops, Coro::AIO for a
1383 more natural syntax.
763 1384
764AUTHOR 1385AUTHOR
765 Marc Lehmann <schmorp@schmorp.de> 1386 Marc Lehmann <schmorp@schmorp.de>
766 http://home.schmorp.de/ 1387 http://home.schmorp.de/
767 1388

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