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Revision 1.46 by root, Sun Mar 27 10:26:08 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 aio_close $fh, $callback->($status)
312 Asynchronously close a file and call the callback with the result
313 code.
314
315 Unfortunately, you can't do this to perl. Perl *insists* very
316 strongly on closing the file descriptor associated with the
317 filehandle itself.
318
319 Therefore, "aio_close" will not close the filehandle - instead it
320 will use dup2 to overwrite the file descriptor with the write-end of
321 a pipe (the pipe fd will be created on demand and will be cached).
322
323 Or in other words: the file descriptor will be closed, but it will
324 not be free for reuse until the perl filehandle is closed.
325
326 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
327 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
328 Reads or writes $length bytes from or to the specified $fh and
329 $offset into the scalar given by $data and offset $dataoffset and
330 calls the callback without the actual number of bytes read (or -1 on
331 error, just like the syscall).
332
333 "aio_read" will, like "sysread", shrink or grow the $data scalar to
334 offset plus the actual number of bytes read.
335
336 If $offset is undefined, then the current file descriptor offset
337 will be used (and updated), otherwise the file descriptor offset
338 will not be changed by these calls.
339
340 If $length is undefined in "aio_write", use the remaining length of
341 $data.
342
343 If $dataoffset is less than zero, it will be counted from the end of
344 $data.
345
346 The $data scalar *MUST NOT* be modified in any way while the request
347 is outstanding. Modifying it can result in segfaults or World War
348 III (if the necessary/optional hardware is installed).
349
350 Example: Read 15 bytes at offset 7 into scalar $buffer, starting at
351 offset 0 within the scalar:
352
353 aio_read $fh, 7, 15, $buffer, 0, sub {
354 $_[0] > 0 or die "read error: $!";
355 print "read $_[0] bytes: <$buffer>\n";
356 };
357
358 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
359 Tries to copy $length bytes from $in_fh to $out_fh. It starts
360 reading at byte offset $in_offset, and starts writing at the current
361 file offset of $out_fh. Because of that, it is not safe to issue
362 more than one "aio_sendfile" per $out_fh, as they will interfere
363 with each other.
364
365 Please note that "aio_sendfile" can read more bytes from $in_fh than
366 are written, and there is no way to find out how many bytes have
367 been read from "aio_sendfile" alone, as "aio_sendfile" only provides
368 the number of bytes written to $out_fh. Only if the result value
369 equals $length one can assume that $length bytes have been read.
370
371 Unlike with other "aio_" functions, it makes a lot of sense to use
372 "aio_sendfile" on non-blocking sockets, as long as one end
373 (typically the $in_fh) is a file - the file I/O will then be
374 asynchronous, while the socket I/O will be non-blocking. Note,
375 however, that you can run into a trap where "aio_sendfile" reads
376 some data with readahead, then fails to write all data, and when the
377 socket is ready the next time, the data in the cache is already
378 lost, forcing "aio_sendfile" to again hit the disk. Explicit
379 "aio_read" + "aio_write" let's you control resource usage much
380 better.
381
382 This call tries to make use of a native "sendfile" syscall to
383 provide zero-copy operation. For this to work, $out_fh should refer
384 to a socket, and $in_fh should refer to an mmap'able file.
385
386 If a native sendfile cannot be found or it fails with "ENOSYS",
387 "ENOTSUP", "EOPNOTSUPP", "EAFNOSUPPORT", "EPROTOTYPE" or "ENOTSOCK",
388 it will be emulated, so you can call "aio_sendfile" on any type of
389 filehandle regardless of the limitations of the operating system.
390
391 aio_readahead $fh,$offset,$length, $callback->($retval)
392 "aio_readahead" populates the page cache with data from a file so
393 that subsequent reads from that file will not block on disk I/O. The
394 $offset argument specifies the starting point from which data is to
395 be read and $length specifies the number of bytes to be read. I/O is
396 performed in whole pages, so that offset is effectively rounded down
397 to a page boundary and bytes are read up to the next page boundary
398 greater than or equal to (off-set+length). "aio_readahead" does not
399 read beyond the end of the file. The current file offset of the file
400 is left unchanged.
401
402 If that syscall doesn't exist (likely if your OS isn't Linux) it
403 will be emulated by simply reading the data, which would have a
404 similar effect.
405
406 aio_stat $fh_or_path, $callback->($status)
407 aio_lstat $fh, $callback->($status)
408 Works like perl's "stat" or "lstat" in void context. The callback
409 will be called after the stat and the results will be available
410 using "stat _" or "-s _" etc...
411
412 The pathname passed to "aio_stat" must be absolute. See API NOTES,
413 above, for an explanation.
414
415 Currently, the stats are always 64-bit-stats, i.e. instead of
416 returning an error when stat'ing a large file, the results will be
417 silently truncated unless perl itself is compiled with large file
418 support.
419
420 To help interpret the mode and dev/rdev stat values, IO::AIO offers
421 the following constants and functions (if not implemented, the
422 constants will be 0 and the functions will either "croak" or fall
423 back on traditional behaviour).
424
425 "S_IFMT", "S_IFIFO", "S_IFCHR", "S_IFBLK", "S_IFLNK", "S_IFREG",
426 "S_IFDIR", "S_IFWHT", "S_IFSOCK", "IO::AIO::major $dev_t",
427 "IO::AIO::minor $dev_t", "IO::AIO::makedev $major, $minor".
428
429 Example: Print the length of /etc/passwd:
430
431 aio_stat "/etc/passwd", sub {
432 $_[0] and die "stat failed: $!";
433 print "size is ", -s _, "\n";
434 };
435
436 aio_statvfs $fh_or_path, $callback->($statvfs)
437 Works like the POSIX "statvfs" or "fstatvfs" syscalls, depending on
438 whether a file handle or path was passed.
439
440 On success, the callback is passed a hash reference with the
441 following members: "bsize", "frsize", "blocks", "bfree", "bavail",
442 "files", "ffree", "favail", "fsid", "flag" and "namemax". On
443 failure, "undef" is passed.
444
445 The following POSIX IO::AIO::ST_* constants are defined: "ST_RDONLY"
446 and "ST_NOSUID".
447
448 The following non-POSIX IO::AIO::ST_* flag masks are defined to
449 their correct value when available, or to 0 on systems that do not
450 support them: "ST_NODEV", "ST_NOEXEC", "ST_SYNCHRONOUS",
451 "ST_MANDLOCK", "ST_WRITE", "ST_APPEND", "ST_IMMUTABLE",
452 "ST_NOATIME", "ST_NODIRATIME" and "ST_RELATIME".
453
454 Example: stat "/wd" and dump out the data if successful.
455
456 aio_statvfs "/wd", sub {
457 my $f = $_[0]
458 or die "statvfs: $!";
459
460 use Data::Dumper;
461 say Dumper $f;
462 };
463
464 # result:
465 {
466 bsize => 1024,
467 bfree => 4333064312,
468 blocks => 10253828096,
469 files => 2050765568,
470 flag => 4096,
471 favail => 2042092649,
472 bavail => 4333064312,
473 ffree => 2042092649,
474 namemax => 255,
475 frsize => 1024,
476 fsid => 1810
477 }
478
479 aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
480 Works like perl's "utime" function (including the special case of
481 $atime and $mtime being undef). Fractional times are supported if
482 the underlying syscalls support them.
483
484 When called with a pathname, uses utimes(2) if available, otherwise
485 utime(2). If called on a file descriptor, uses futimes(2) if
486 available, otherwise returns ENOSYS, so this is not portable.
487
488 Examples:
489
490 # set atime and mtime to current time (basically touch(1)):
491 aio_utime "path", undef, undef;
492 # set atime to current time and mtime to beginning of the epoch:
493 aio_utime "path", time, undef; # undef==0
494
495 aio_chown $fh_or_path, $uid, $gid, $callback->($status)
496 Works like perl's "chown" function, except that "undef" for either
497 $uid or $gid is being interpreted as "do not change" (but -1 can
498 also be used).
499
500 Examples:
501
502 # same as "chown root path" in the shell:
503 aio_chown "path", 0, -1;
504 # same as above:
505 aio_chown "path", 0, undef;
506
507 aio_truncate $fh_or_path, $offset, $callback->($status)
508 Works like truncate(2) or ftruncate(2).
509
510 aio_chmod $fh_or_path, $mode, $callback->($status)
511 Works like perl's "chmod" function.
512
513 aio_unlink $pathname, $callback->($status)
514 Asynchronously unlink (delete) a file and call the callback with the
515 result code.
516
517 aio_mknod $path, $mode, $dev, $callback->($status)
518 [EXPERIMENTAL]
519
520 Asynchronously create a device node (or fifo). See mknod(2).
521
522 The only (POSIX-) portable way of calling this function is:
523
524 aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...
525
526 See "aio_stat" for info about some potentially helpful extra
527 constants and functions.
528
529 aio_link $srcpath, $dstpath, $callback->($status)
530 Asynchronously create a new link to the existing object at $srcpath
531 at the path $dstpath and call the callback with the result code.
532
533 aio_symlink $srcpath, $dstpath, $callback->($status)
534 Asynchronously create a new symbolic link to the existing object at
535 $srcpath at the path $dstpath and call the callback with the result
536 code.
537
538 aio_readlink $path, $callback->($link)
539 Asynchronously read the symlink specified by $path and pass it to
540 the callback. If an error occurs, nothing or undef gets passed to
541 the callback.
542
543 aio_rename $srcpath, $dstpath, $callback->($status)
544 Asynchronously rename the object at $srcpath to $dstpath, just as
545 rename(2) and call the callback with the result code.
546
547 aio_mkdir $pathname, $mode, $callback->($status)
548 Asynchronously mkdir (create) a directory and call the callback with
549 the result code. $mode will be modified by the umask at the time the
550 request is executed, so do not change your umask.
551
552 aio_rmdir $pathname, $callback->($status)
553 Asynchronously rmdir (delete) a directory and call the callback with
554 the result code.
555
556 aio_readdir $pathname, $callback->($entries)
557 Unlike the POSIX call of the same name, "aio_readdir" reads an
558 entire directory (i.e. opendir + readdir + closedir). The entries
559 will not be sorted, and will NOT include the "." and ".." entries.
560
561 The callback is passed a single argument which is either "undef" or
562 an array-ref with the filenames.
563
564 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
565 Quite similar to "aio_readdir", but the $flags argument allows to
566 tune behaviour and output format. In case of an error, $entries will
567 be "undef".
568
569 The flags are a combination of the following constants, ORed
570 together (the flags will also be passed to the callback, possibly
571 modified):
572
573 IO::AIO::READDIR_DENTS
574 When this flag is off, then the callback gets an arrayref with
575 of names only (as with "aio_readdir"), otherwise it gets an
576 arrayref with "[$name, $type, $inode]" arrayrefs, each
577 describing a single directory entry in more detail.
578
579 $name is the name of the entry.
580
581 $type is one of the "IO::AIO::DT_xxx" constants:
582
583 "IO::AIO::DT_UNKNOWN", "IO::AIO::DT_FIFO", "IO::AIO::DT_CHR",
584 "IO::AIO::DT_DIR", "IO::AIO::DT_BLK", "IO::AIO::DT_REG",
585 "IO::AIO::DT_LNK", "IO::AIO::DT_SOCK", "IO::AIO::DT_WHT".
586
587 "IO::AIO::DT_UNKNOWN" means just that: readdir does not know. If
588 you need to know, you have to run stat yourself. Also, for speed
589 reasons, the $type scalars are read-only: you can not modify
590 them.
591
592 $inode is the inode number (which might not be exact on systems
593 with 64 bit inode numbers and 32 bit perls). This field has
594 unspecified content on systems that do not deliver the inode
595 information.
596
597 IO::AIO::READDIR_DIRS_FIRST
598 When this flag is set, then the names will be returned in an
599 order where likely directories come first. This is useful when
600 you need to quickly find directories, or you want to find all
601 directories while avoiding to stat() each entry.
602
603 If the system returns type information in readdir, then this is
604 used to find directories directly. Otherwise, likely directories
605 are files beginning with ".", or otherwise files with no dots,
606 of which files with short names are tried first.
607
608 IO::AIO::READDIR_STAT_ORDER
609 When this flag is set, then the names will be returned in an
610 order suitable for stat()'ing each one. That is, when you plan
611 to stat() all files in the given directory, then the returned
612 order will likely be fastest.
613
614 If both this flag and "IO::AIO::READDIR_DIRS_FIRST" are
615 specified, then the likely dirs come first, resulting in a less
616 optimal stat order.
617
618 IO::AIO::READDIR_FOUND_UNKNOWN
619 This flag should not be set when calling "aio_readdirx".
620 Instead, it is being set by "aio_readdirx", when any of the
621 $type's found were "IO::AIO::DT_UNKNOWN". The absense of this
622 flag therefore indicates that all $type's are known, which can
623 be used to speed up some algorithms.
624
625 aio_load $path, $data, $callback->($status)
626 This is a composite request that tries to fully load the given file
627 into memory. Status is the same as with aio_read.
628
629 aio_copy $srcpath, $dstpath, $callback->($status)
630 Try to copy the *file* (directories not supported as either source
631 or destination) from $srcpath to $dstpath and call the callback with
632 a status of 0 (ok) or -1 (error, see $!).
633
634 This is a composite request that creates the destination file with
635 mode 0200 and copies the contents of the source file into it using
636 "aio_sendfile", followed by restoring atime, mtime, access mode and
637 uid/gid, in that order.
638
639 If an error occurs, the partial destination file will be unlinked,
640 if possible, except when setting atime, mtime, access mode and
641 uid/gid, where errors are being ignored.
642
643 aio_move $srcpath, $dstpath, $callback->($status)
644 Try to move the *file* (directories not supported as either source
645 or destination) from $srcpath to $dstpath and call the callback with
646 a status of 0 (ok) or -1 (error, see $!).
647
648 This is a composite request that tries to rename(2) the file first;
649 if rename fails with "EXDEV", it copies the file with "aio_copy"
650 and, if that is successful, unlinks the $srcpath.
651
652 aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
653 Scans a directory (similar to "aio_readdir") but additionally tries
654 to efficiently separate the entries of directory $path into two sets
655 of names, directories you can recurse into (directories), and ones
656 you cannot recurse into (everything else, including symlinks to
657 directories).
658
659 "aio_scandir" is a composite request that creates of many sub
660 requests_ $maxreq specifies the maximum number of outstanding aio
661 requests that this function generates. If it is "<= 0", then a
662 suitable default will be chosen (currently 4).
663
664 On error, the callback is called without arguments, otherwise it
665 receives two array-refs with path-relative entry names.
666
667 Example:
668
669 aio_scandir $dir, 0, sub {
670 my ($dirs, $nondirs) = @_;
671 print "real directories: @$dirs\n";
672 print "everything else: @$nondirs\n";
673 };
674
675 Implementation notes.
676
677 The "aio_readdir" cannot be avoided, but "stat()"'ing every entry
678 can.
679
680 If readdir returns file type information, then this is used directly
681 to find directories.
682
683 Otherwise, after reading the directory, the modification time, size
684 etc. of the directory before and after the readdir is checked, and
685 if they match (and isn't the current time), the link count will be
686 used to decide how many entries are directories (if >= 2).
687 Otherwise, no knowledge of the number of subdirectories will be
688 assumed.
689
690 Then entries will be sorted into likely directories a non-initial
691 dot currently) and likely non-directories (see "aio_readdirx"). Then
692 every entry plus an appended "/." will be "stat"'ed, likely
693 directories first, in order of their inode numbers. If that
694 succeeds, it assumes that the entry is a directory or a symlink to
695 directory (which will be checked seperately). This is often faster
696 than stat'ing the entry itself because filesystems might detect the
697 type of the entry without reading the inode data (e.g. ext2fs
698 filetype feature), even on systems that cannot return the filetype
699 information on readdir.
700
701 If the known number of directories (link count - 2) has been
702 reached, the rest of the entries is assumed to be non-directories.
703
704 This only works with certainty on POSIX (= UNIX) filesystems, which
705 fortunately are the vast majority of filesystems around.
706
707 It will also likely work on non-POSIX filesystems with reduced
708 efficiency as those tend to return 0 or 1 as link counts, which
709 disables the directory counting heuristic.
710
711 aio_rmtree $path, $callback->($status)
712 Delete a directory tree starting (and including) $path, return the
713 status of the final "rmdir" only. This is a composite request that
714 uses "aio_scandir" to recurse into and rmdir directories, and unlink
715 everything else.
716
717 aio_sync $callback->($status)
718 Asynchronously call sync and call the callback when finished.
719
720 aio_fsync $fh, $callback->($status)
721 Asynchronously call fsync on the given filehandle and call the
722 callback with the fsync result code.
723
724 aio_fdatasync $fh, $callback->($status)
725 Asynchronously call fdatasync on the given filehandle and call the
726 callback with the fdatasync result code.
727
728 If this call isn't available because your OS lacks it or it couldn't
729 be detected, it will be emulated by calling "fsync" instead.
730
731 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
732 Sync the data portion of the file specified by $offset and $length
733 to disk (but NOT the metadata), by calling the Linux-specific
734 sync_file_range call. If sync_file_range is not available or it
735 returns ENOSYS, then fdatasync or fsync is being substituted.
736
737 $flags can be a combination of
738 "IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE",
739 "IO::AIO::SYNC_FILE_RANGE_WRITE" and
740 "IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER": refer to the sync_file_range
741 manpage for details.
742
743 aio_pathsync $path, $callback->($status)
744 This request tries to open, fsync and close the given path. This is
745 a composite request intended to sync directories after directory
746 operations (E.g. rename). This might not work on all operating
747 systems or have any specific effect, but usually it makes sure that
748 directory changes get written to disc. It works for anything that
749 can be opened for read-only, not just directories.
750
751 Future versions of this function might fall back to other methods
752 when "fsync" on the directory fails (such as calling "sync").
753
754 Passes 0 when everything went ok, and -1 on error.
755
756 aio_msync $scalar, $offset = 0, $length = undef, flags = 0,
757 $callback->($status)
758 This is a rather advanced IO::AIO call, which only works on
759 mmap(2)ed scalars (see the "IO::AIO::mmap" function, although it
760 also works on data scalars managed by the Sys::Mmap or Mmap modules,
761 note that the scalar must only be modified in-place while an aio
762 operation is pending on it).
763
764 It calls the "msync" function of your OS, if available, with the
765 memory area starting at $offset in the string and ending $length
766 bytes later. If $length is negative, counts from the end, and if
767 $length is "undef", then it goes till the end of the string. The
768 flags can be a combination of "IO::AIO::MS_ASYNC",
769 "IO::AIO::MS_INVALIDATE" and "IO::AIO::MS_SYNC".
770
771 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0,
772 $callback->($status)
773 This is a rather advanced IO::AIO call, which works best on
774 mmap(2)ed scalars.
775
776 It touches (reads or writes) all memory pages in the specified range
777 inside the scalar. All caveats and parameters are the same as for
778 "aio_msync", above, except for flags, which must be either 0 (which
779 reads all pages and ensures they are instantiated) or
780 "IO::AIO::MT_MODIFY", which modifies the memory page s(by reading
781 and writing an octet from it, which dirties the page).
782
783 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
784 This is a rather advanced IO::AIO call, which works best on
785 mmap(2)ed scalars.
786
787 It reads in all the pages of the underlying storage into memory (if
788 any) and locks them, so they are not getting swapped/paged out or
789 removed.
790
791 If $length is undefined, then the scalar will be locked till the
792 end.
793
794 On systems that do not implement "mlock", this function returns -1
795 and sets errno to "ENOSYS".
796
797 Note that the corresponding "munlock" is synchronous and is
798 documented under "MISCELLANEOUS FUNCTIONS".
799
800 Example: open a file, mmap and mlock it - both will be undone when
801 $data gets destroyed.
802
803 open my $fh, "<", $path or die "$path: $!";
804 my $data;
805 IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
806 aio_mlock $data; # mlock in background
807
808 aio_mlockall $flags, $callback->($status)
809 Calls the "mlockall" function with the given $flags (a combination
810 of "IO::AIO::MCL_CURRENT" and "IO::AIO::MCL_FUTURE").
811
812 On systems that do not implement "mlockall", this function returns
813 -1 and sets errno to "ENOSYS".
814
815 Note that the corresponding "munlockall" is synchronous and is
816 documented under "MISCELLANEOUS FUNCTIONS".
817
818 Example: asynchronously lock all current and future pages into
819 memory.
820
821 aio_mlockall IO::AIO::MCL_FUTURE;
822
823 aio_group $callback->(...)
824 This is a very special aio request: Instead of doing something, it
825 is a container for other aio requests, which is useful if you want
826 to bundle many requests into a single, composite, request with a
827 definite callback and the ability to cancel the whole request with
828 its subrequests.
829
830 Returns an object of class IO::AIO::GRP. See its documentation below
831 for more info.
832
833 Example:
834
835 my $grp = aio_group sub {
836 print "all stats done\n";
837 };
838
839 add $grp
840 (aio_stat ...),
841 (aio_stat ...),
842 ...;
843
844 aio_nop $callback->()
845 This is a special request - it does nothing in itself and is only
846 used for side effects, such as when you want to add a dummy request
847 to a group so that finishing the requests in the group depends on
848 executing the given code.
849
850 While this request does nothing, it still goes through the execution
851 phase and still requires a worker thread. Thus, the callback will
852 not be executed immediately but only after other requests in the
853 queue have entered their execution phase. This can be used to
854 measure request latency.
855
856 IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
857 Mainly used for debugging and benchmarking, this aio request puts
858 one of the request workers to sleep for the given time.
859
860 While it is theoretically handy to have simple I/O scheduling
861 requests like sleep and file handle readable/writable, the overhead
862 this creates is immense (it blocks a thread for a long time) so do
863 not use this function except to put your application under
864 artificial I/O pressure.
865
866 IO::AIO::REQ CLASS
867 All non-aggregate "aio_*" functions return an object of this class when
868 called in non-void context.
869
870 cancel $req
871 Cancels the request, if possible. Has the effect of skipping
872 execution when entering the execute state and skipping calling the
873 callback when entering the the result state, but will leave the
874 request otherwise untouched (with the exception of readdir). That
875 means that requests that currently execute will not be stopped and
876 resources held by the request will not be freed prematurely.
877
878 cb $req $callback->(...)
879 Replace (or simply set) the callback registered to the request.
880
881 IO::AIO::GRP CLASS
882 This class is a subclass of IO::AIO::REQ, so all its methods apply to
883 objects of this class, too.
884
885 A IO::AIO::GRP object is a special request that can contain multiple
886 other aio requests.
887
888 You create one by calling the "aio_group" constructing function with a
889 callback that will be called when all contained requests have entered
890 the "done" state:
891
892 my $grp = aio_group sub {
893 print "all requests are done\n";
894 };
895
896 You add requests by calling the "add" method with one or more
897 "IO::AIO::REQ" objects:
898
899 $grp->add (aio_unlink "...");
900
901 add $grp aio_stat "...", sub {
902 $_[0] or return $grp->result ("error");
903
904 # add another request dynamically, if first succeeded
905 add $grp aio_open "...", sub {
906 $grp->result ("ok");
907 };
908 };
909
493 This makes it very easy to create composite requests (see the source 910 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 911 "aio_move" for an application) that work and feel like simple requests.
912
913 * The IO::AIO::GRP objects will be cleaned up during calls to
914 "IO::AIO::poll_cb", just like any other request.
915
916 * They can be canceled like any other request. Canceling will cancel
917 not only the request itself, but also all requests it contains.
918
919 * They can also can also be added to other IO::AIO::GRP objects.
920
921 * You must not add requests to a group from within the group callback
922 (or any later time).
923
924 Their lifetime, simplified, looks like this: when they are empty, they
925 will finish very quickly. If they contain only requests that are in the
926 "done" state, they will also finish. Otherwise they will continue to
927 exist.
928
929 That means after creating a group you have some time to add requests
930 (precisely before the callback has been invoked, which is only done
931 within the "poll_cb"). And in the callbacks of those requests, you can
932 add further requests to the group. And only when all those requests have
933 finished will the the group itself finish.
934
935 add $grp ...
936 $grp->add (...)
937 Add one or more requests to the group. Any type of IO::AIO::REQ can
938 be added, including other groups, as long as you do not create
939 circular dependencies.
940
941 Returns all its arguments.
942
943 $grp->cancel_subs
944 Cancel all subrequests and clears any feeder, but not the group
945 request itself. Useful when you queued a lot of events but got a
946 result early.
947
948 The group request will finish normally (you cannot add requests to
949 the group).
950
951 $grp->result (...)
952 Set the result value(s) that will be passed to the group callback
953 when all subrequests have finished and set the groups errno to the
954 current value of errno (just like calling "errno" without an error
955 number). By default, no argument will be passed and errno is zero.
956
957 $grp->errno ([$errno])
958 Sets the group errno value to $errno, or the current value of errno
959 when the argument is missing.
960
961 Every aio request has an associated errno value that is restored
962 when the callback is invoked. This method lets you change this value
963 from its default (0).
964
965 Calling "result" will also set errno, so make sure you either set $!
966 before the call to "result", or call c<errno> after it.
967
968 feed $grp $callback->($grp)
969 Sets a feeder/generator on this group: every group can have an
970 attached generator that generates requests if idle. The idea behind
971 this is that, although you could just queue as many requests as you
972 want in a group, this might starve other requests for a potentially
973 long time. For example, "aio_scandir" might generate hundreds of
974 thousands "aio_stat" requests, delaying any later requests for a
975 long time.
976
977 To avoid this, and allow incremental generation of requests, you can
978 instead a group and set a feeder on it that generates those
979 requests. The feed callback will be called whenever there are few
980 enough (see "limit", below) requests active in the group itself and
981 is expected to queue more requests.
982
983 The feed callback can queue as many requests as it likes (i.e. "add"
984 does not impose any limits).
985
986 If the feed does not queue more requests when called, it will be
987 automatically removed from the group.
988
989 If the feed limit is 0 when this method is called, it will be set to
990 2 automatically.
991
992 Example:
993
994 # stat all files in @files, but only ever use four aio requests concurrently:
995
996 my $grp = aio_group sub { print "finished\n" };
997 limit $grp 4;
998 feed $grp sub {
999 my $file = pop @files
1000 or return;
1001
1002 add $grp aio_stat $file, sub { ... };
1003 };
1004
1005 limit $grp $num
1006 Sets the feeder limit for the group: The feeder will be called
1007 whenever the group contains less than this many requests.
1008
1009 Setting the limit to 0 will pause the feeding process.
1010
1011 The default value for the limit is 0, but note that setting a feeder
1012 automatically bumps it up to 2.
1013
1014 SUPPORT FUNCTIONS
1015 EVENT PROCESSING AND EVENT LOOP INTEGRATION
1016 $fileno = IO::AIO::poll_fileno
1017 Return the *request result pipe file descriptor*. This filehandle
1018 must be polled for reading by some mechanism outside this module
1019 (e.g. EV, Glib, select and so on, see below or the SYNOPSIS). If the
1020 pipe becomes readable you have to call "poll_cb" to check the
1021 results.
1022
1023 See "poll_cb" for an example.
1024
1025 IO::AIO::poll_cb
1026 Process some outstanding events on the result pipe. You have to call
1027 this regularly. Returns 0 if all events could be processed, or -1 if
1028 it returned earlier for whatever reason. Returns immediately when no
1029 events are outstanding. The amount of events processed depends on
1030 the settings of "IO::AIO::max_poll_req" and
1031 "IO::AIO::max_poll_time".
1032
1033 If not all requests were processed for whatever reason, the
1034 filehandle will still be ready when "poll_cb" returns, so normally
1035 you don't have to do anything special to have it called later.
1036
1037 Example: Install an Event watcher that automatically calls
1038 IO::AIO::poll_cb with high priority (more examples can be found in
1039 the SYNOPSIS section, at the top of this document):
1040
1041 Event->io (fd => IO::AIO::poll_fileno,
1042 poll => 'r', async => 1,
1043 cb => \&IO::AIO::poll_cb);
1044
1045 IO::AIO::poll_wait
1046 If there are any outstanding requests and none of them in the result
1047 phase, wait till the result filehandle becomes ready for reading
1048 (simply does a "select" on the filehandle. This is useful if you
1049 want to synchronously wait for some requests to finish).
1050
1051 See "nreqs" for an example.
1052
1053 IO::AIO::poll
1054 Waits until some requests have been handled.
1055
1056 Returns the number of requests processed, but is otherwise strictly
1057 equivalent to:
1058
1059 IO::AIO::poll_wait, IO::AIO::poll_cb
1060
1061 IO::AIO::flush
1062 Wait till all outstanding AIO requests have been handled.
1063
1064 Strictly equivalent to:
1065
1066 IO::AIO::poll_wait, IO::AIO::poll_cb
1067 while IO::AIO::nreqs;
1068
1069 IO::AIO::max_poll_reqs $nreqs
1070 IO::AIO::max_poll_time $seconds
1071 These set the maximum number of requests (default 0, meaning
1072 infinity) that are being processed by "IO::AIO::poll_cb" in one
1073 call, respectively the maximum amount of time (default 0, meaning
1074 infinity) spent in "IO::AIO::poll_cb" to process requests (more
1075 correctly the mininum amount of time "poll_cb" is allowed to use).
1076
1077 Setting "max_poll_time" to a non-zero value creates an overhead of
1078 one syscall per request processed, which is not normally a problem
1079 unless your callbacks are really really fast or your OS is really
1080 really slow (I am not mentioning Solaris here). Using
1081 "max_poll_reqs" incurs no overhead.
1082
1083 Setting these is useful if you want to ensure some level of
1084 interactiveness when perl is not fast enough to process all requests
1085 in time.
1086
1087 For interactive programs, values such as 0.01 to 0.1 should be fine.
1088
1089 Example: Install an Event watcher that automatically calls
1090 IO::AIO::poll_cb with low priority, to ensure that other parts of
1091 the program get the CPU sometimes even under high AIO load.
1092
1093 # try not to spend much more than 0.1s in poll_cb
1094 IO::AIO::max_poll_time 0.1;
1095
1096 # use a low priority so other tasks have priority
1097 Event->io (fd => IO::AIO::poll_fileno,
1098 poll => 'r', nice => 1,
1099 cb => &IO::AIO::poll_cb);
1100
1101 CONTROLLING THE NUMBER OF THREADS
1102 IO::AIO::min_parallel $nthreads
1103 Set the minimum number of AIO threads to $nthreads. The current
1104 default is 8, which means eight asynchronous operations can execute
1105 concurrently at any one time (the number of outstanding requests,
1106 however, is unlimited).
1107
1108 IO::AIO starts threads only on demand, when an AIO request is queued
1109 and no free thread exists. Please note that queueing up a hundred
1110 requests can create demand for a hundred threads, even if it turns
1111 out that everything is in the cache and could have been processed
1112 faster by a single thread.
1113
1114 It is recommended to keep the number of threads relatively low, as
1115 some Linux kernel versions will scale negatively with the number of
1116 threads (higher parallelity => MUCH higher latency). With current
1117 Linux 2.6 versions, 4-32 threads should be fine.
1118
1119 Under most circumstances you don't need to call this function, as
1120 the module selects a default that is suitable for low to moderate
1121 load.
1122
1123 IO::AIO::max_parallel $nthreads
1124 Sets the maximum number of AIO threads to $nthreads. If more than
1125 the specified number of threads are currently running, this function
1126 kills them. This function blocks until the limit is reached.
1127
1128 While $nthreads are zero, aio requests get queued but not executed
1129 until the number of threads has been increased again.
1130
1131 This module automatically runs "max_parallel 0" at program end, to
1132 ensure that all threads are killed and that there are no outstanding
495 requests. 1133 requests.
496 1134
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. 1135 Under normal circumstances you don't need to call this function.
701 1136
1137 IO::AIO::max_idle $nthreads
1138 Limit the number of threads (default: 4) that are allowed to idle
1139 (i.e., threads that did not get a request to process within the idle
1140 timeout (default: 10 seconds). That means if a thread becomes idle
1141 while $nthreads other threads are also idle, it will free its
1142 resources and exit.
1143
1144 This is useful when you allow a large number of threads (e.g. 100 or
1145 1000) to allow for extremely high load situations, but want to free
1146 resources under normal circumstances (1000 threads can easily
1147 consume 30MB of RAM).
1148
1149 The default is probably ok in most situations, especially if thread
1150 creation is fast. If thread creation is very slow on your system you
1151 might want to use larger values.
1152
1153 IO::AIO::idle_timeout $seconds
1154 Sets the minimum idle timeout (default 10) after which worker
1155 threads are allowed to exit. SEe "IO::AIO::max_idle".
1156
702 $oldmaxreqs = IO::AIO::max_outstanding $maxreqs 1157 IO::AIO::max_outstanding $maxreqs
703 This is a very bad function to use in interactive programs 1158 This is a very bad function to use in interactive programs because
704 because it blocks, and a bad way to reduce concurrency because 1159 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 1160 inexact: Better use an "aio_group" together with a feed callback.
706 callback.
707 1161
708 Sets the maximum number of outstanding requests to $nreqs. If 1162 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 1163 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 1164 "poll_cb" (and "poll_some" and other functions calling "poll_cb")
711 "poll_cb") function will block until the limit is no longer 1165 function will block until the limit is no longer exceeded.
712 exceeded.
713 1166
714 The default value is very large, so there is no practical limit 1167 The default value is very large, so there is no practical limit on
715 on the number of outstanding requests. 1168 the number of outstanding requests.
716 1169
717 You can still queue as many requests as you want. Therefore, 1170 You can still queue as many requests as you want. Therefore,
718 "max_oustsanding" is mainly useful in simple scripts (with low 1171 "max_outstanding" is mainly useful in simple scripts (with low
719 values) or as a stop gap to shield against fatal memory overflow 1172 values) or as a stop gap to shield against fatal memory overflow
720 (with large values). 1173 (with large values).
1174
1175 STATISTICAL INFORMATION
1176 IO::AIO::nreqs
1177 Returns the number of requests currently in the ready, execute or
1178 pending states (i.e. for which their callback has not been invoked
1179 yet).
1180
1181 Example: wait till there are no outstanding requests anymore:
1182
1183 IO::AIO::poll_wait, IO::AIO::poll_cb
1184 while IO::AIO::nreqs;
1185
1186 IO::AIO::nready
1187 Returns the number of requests currently in the ready state (not yet
1188 executed).
1189
1190 IO::AIO::npending
1191 Returns the number of requests currently in the pending state
1192 (executed, but not yet processed by poll_cb).
1193
1194 MISCELLANEOUS FUNCTIONS
1195 IO::AIO implements some functions that might be useful, but are not
1196 asynchronous.
1197
1198 IO::AIO::sendfile $ofh, $ifh, $offset, $count
1199 Calls the "eio_sendfile_sync" function, which is like
1200 "aio_sendfile", but is blocking (this makes most sense if you know
1201 the input data is likely cached already and the output filehandle is
1202 set to non-blocking operations).
1203
1204 Returns the number of bytes copied, or -1 on error.
1205
1206 IO::AIO::fadvise $fh, $offset, $len, $advice
1207 Simply calls the "posix_fadvise" function (see its manpage for
1208 details). The following advice constants are avaiable:
1209 "IO::AIO::FADV_NORMAL", "IO::AIO::FADV_SEQUENTIAL",
1210 "IO::AIO::FADV_RANDOM", "IO::AIO::FADV_NOREUSE",
1211 "IO::AIO::FADV_WILLNEED", "IO::AIO::FADV_DONTNEED".
1212
1213 On systems that do not implement "posix_fadvise", this function
1214 returns ENOSYS, otherwise the return value of "posix_fadvise".
1215
1216 IO::AIO::madvise $scalar, $offset, $len, $advice
1217 Simply calls the "posix_madvise" function (see its manpage for
1218 details). The following advice constants are avaiable:
1219 "IO::AIO::MADV_NORMAL", "IO::AIO::MADV_SEQUENTIAL",
1220 "IO::AIO::MADV_RANDOM", "IO::AIO::MADV_WILLNEED",
1221 "IO::AIO::MADV_DONTNEED".
1222
1223 On systems that do not implement "posix_madvise", this function
1224 returns ENOSYS, otherwise the return value of "posix_madvise".
1225
1226 IO::AIO::mprotect $scalar, $offset, $len, $protect
1227 Simply calls the "mprotect" function on the preferably AIO::mmap'ed
1228 $scalar (see its manpage for details). The following protect
1229 constants are avaiable: "IO::AIO::PROT_NONE", "IO::AIO::PROT_READ",
1230 "IO::AIO::PROT_WRITE", "IO::AIO::PROT_EXEC".
1231
1232 On systems that do not implement "mprotect", this function returns
1233 ENOSYS, otherwise the return value of "mprotect".
1234
1235 IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
1236 Memory-maps a file (or anonymous memory range) and attaches it to
1237 the given $scalar, which will act like a string scalar.
1238
1239 The only operations allowed on the scalar are "substr"/"vec" that
1240 don't change the string length, and most read-only operations such
1241 as copying it or searching it with regexes and so on.
1242
1243 Anything else is unsafe and will, at best, result in memory leaks.
1244
1245 The memory map associated with the $scalar is automatically removed
1246 when the $scalar is destroyed, or when the "IO::AIO::mmap" or
1247 "IO::AIO::munmap" functions are called.
1248
1249 This calls the "mmap"(2) function internally. See your system's
1250 manual page for details on the $length, $prot and $flags parameters.
1251
1252 The $length must be larger than zero and smaller than the actual
1253 filesize.
1254
1255 $prot is a combination of "IO::AIO::PROT_NONE",
1256 "IO::AIO::PROT_EXEC", "IO::AIO::PROT_READ" and/or
1257 "IO::AIO::PROT_WRITE",
1258
1259 $flags can be a combination of "IO::AIO::MAP_SHARED" or
1260 "IO::AIO::MAP_PRIVATE", or a number of system-specific flags (when
1261 not available, the are defined as 0): "IO::AIO::MAP_ANONYMOUS"
1262 (which is set to "MAP_ANON" if your system only provides this
1263 constant), "IO::AIO::MAP_HUGETLB", "IO::AIO::MAP_LOCKED",
1264 "IO::AIO::MAP_NORESERVE", "IO::AIO::MAP_POPULATE" or
1265 "IO::AIO::MAP_NONBLOCK"
1266
1267 If $fh is "undef", then a file descriptor of -1 is passed.
1268
1269 $offset is the offset from the start of the file - it generally must
1270 be a multiple of "IO::AIO::PAGESIZE" and defaults to 0.
1271
1272 Example:
1273
1274 use Digest::MD5;
1275 use IO::AIO;
1276
1277 open my $fh, "<verybigfile"
1278 or die "$!";
1279
1280 IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
1281 or die "verybigfile: $!";
1282
1283 my $fast_md5 = md5 $data;
1284
1285 IO::AIO::munmap $scalar
1286 Removes a previous mmap and undefines the $scalar.
1287
1288 IO::AIO::munlock $scalar, $offset = 0, $length = undef
1289 Calls the "munlock" function, undoing the effects of a previous
1290 "aio_mlock" call (see its description for details).
1291
1292 IO::AIO::munlockall
1293 Calls the "munlockall" function.
1294
1295 On systems that do not implement "munlockall", this function returns
1296 ENOSYS, otherwise the return value of "munlockall".
1297
1298EVENT LOOP INTEGRATION
1299 It is recommended to use AnyEvent::AIO to integrate IO::AIO
1300 automatically into many event loops:
1301
1302 # AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
1303 use AnyEvent::AIO;
1304
1305 You can also integrate IO::AIO manually into many event loops, here are
1306 some examples of how to do this:
1307
1308 # EV integration
1309 my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
1310
1311 # Event integration
1312 Event->io (fd => IO::AIO::poll_fileno,
1313 poll => 'r',
1314 cb => \&IO::AIO::poll_cb);
1315
1316 # Glib/Gtk2 integration
1317 add_watch Glib::IO IO::AIO::poll_fileno,
1318 in => sub { IO::AIO::poll_cb; 1 };
1319
1320 # Tk integration
1321 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
1322 readable => \&IO::AIO::poll_cb);
1323
1324 # Danga::Socket integration
1325 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
1326 \&IO::AIO::poll_cb);
721 1327
722 FORK BEHAVIOUR 1328 FORK BEHAVIOUR
723 This module should do "the right thing" when the process using it 1329 This module should do "the right thing" when the process using it forks:
724 forks:
725 1330
726 Before the fork, IO::AIO enters a quiescent state where no requests 1331 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. 1332 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 1333 fork the parent simply leaves the quiescent state and continues
729 continues request/result processing, while the child frees the 1334 request/result processing, while the child frees the request/result
730 request/result queue (so that the requests started before the fork 1335 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 1336 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 1337 the parent process has been reached again.
733 again.
734 1338
735 In short: the parent will, after a short pause, continue as if fork 1339 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 1340 not been called, while the child will act as if IO::AIO has not been
737 been used yet. 1341 used yet.
738 1342
739 MEMORY USAGE 1343 MEMORY USAGE
740 Per-request usage: 1344 Per-request usage:
741 1345
742 Each aio request uses - depending on your architecture - around 1346 Each aio request uses - depending on your architecture - around 100-200
743 100-200 bytes of memory. In addition, stat requests need a stat 1347 bytes of memory. In addition, stat requests need a stat buffer (possibly
744 buffer (possibly a few hundred bytes), readdir requires a result 1348 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 1349 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 1350 will consume memory till the request has entered the done state.
747 request has entered the done state.
748 1351
749 This is now awfully much, so queuing lots of requests is not usually 1352 This is not awfully much, so queuing lots of requests is not usually a
750 a problem. 1353 problem.
751 1354
752 Per-thread usage: 1355 Per-thread usage:
753 1356
754 In the execution phase, some aio requests require more memory for 1357 In the execution phase, some aio requests require more memory for
755 temporary buffers, and each thread requires a stack and other data 1358 temporary buffers, and each thread requires a stack and other data
756 structures (usually around 16k-128k, depending on the OS). 1359 structures (usually around 16k-128k, depending on the OS).
757 1360
758KNOWN BUGS 1361KNOWN BUGS
759 Known bugs will be fixed in the next release. 1362 Known bugs will be fixed in the next release.
760 1363
761SEE ALSO 1364SEE ALSO
762 Coro::AIO. 1365 AnyEvent::AIO for easy integration into event loops, Coro::AIO for a
1366 more natural syntax.
763 1367
764AUTHOR 1368AUTHOR
765 Marc Lehmann <schmorp@schmorp.de> 1369 Marc Lehmann <schmorp@schmorp.de>
766 http://home.schmorp.de/ 1370 http://home.schmorp.de/
767 1371

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