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Revision 1.49 by root, Mon Jul 18 03:09:06 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 173 aio_realpath $path, $callback->($link)
319 result code.
320
321 aio_rename $srcpath, $dstpath, $callback->($status) 174 aio_rename $srcpath, $dstpath, $callback->($status)
322 Asynchronously rename the object at $srcpath to $dstpath, just 175 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) 176 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) 177 aio_readdir $pathname, $callback->($entries)
330 Unlike the POSIX call of the same name, "aio_readdir" reads an 178 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
331 entire directory (i.e. opendir + readdir + closedir). The 179 IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
332 entries will not be sorted, and will NOT include the "." and 180 IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
333 ".." entries. 181 aio_load $path, $data, $callback->($status)
334 182 aio_copy $srcpath, $dstpath, $callback->($status)
335 The callback a single argument which is either "undef" or an 183 aio_move $srcpath, $dstpath, $callback->($status)
336 array-ref with the filenames.
337
338 aio_scandir $path, $maxreq, $callback->($dirs, $nondirs) 184 aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
339 Scans a directory (similar to "aio_readdir") but additionally 185 aio_rmtree $path, $callback->($status)
340 tries to efficiently separate the entries of directory $path 186 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) 187 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) 188 aio_fdatasync $fh, $callback->($status)
399 Asynchronously call fdatasync on the given filehandle and call 189 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
400 the callback with the fdatasync result code. 190 aio_pathsync $path, $callback->($status)
401 191 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 192 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
403 couldn't be detected, it will be emulated by calling "fsync" 193 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
404 instead. 194 aio_mlockall $flags, $callback->($status)
405
406 aio_group $callback->(...) 195 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->() 196 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.
432 197
433 While this request does nothing, it still goes through the 198 $prev_pri = aioreq_pri [$pri]
434 execution phase and still requires a worker thread. Thus, the 199 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.
438 200
439 IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED* 201 IO::AIO::poll_wait
440 Mainly used for debugging and benchmarking, this aio request 202 IO::AIO::poll_cb
441 puts one of the request workers to sleep for the given time. 203 IO::AIO::poll
204 IO::AIO::flush
205 IO::AIO::max_poll_reqs $nreqs
206 IO::AIO::max_poll_time $seconds
207 IO::AIO::min_parallel $nthreads
208 IO::AIO::max_parallel $nthreads
209 IO::AIO::max_idle $nthreads
210 IO::AIO::idle_timeout $seconds
211 IO::AIO::max_outstanding $maxreqs
212 IO::AIO::nreqs
213 IO::AIO::nready
214 IO::AIO::npending
442 215
443 While it is theoretically handy to have simple I/O scheduling 216 IO::AIO::sendfile $ofh, $ifh, $offset, $count
444 requests like sleep and file handle readable/writable, the 217 IO::AIO::fadvise $fh, $offset, $len, $advice
445 overhead this creates is immense (it blocks a thread for a long 218 IO::AIO::madvise $scalar, $offset, $length, $advice
446 time) so do not use this function except to put your application 219 IO::AIO::mprotect $scalar, $offset, $length, $protect
447 under artificial I/O pressure. 220 IO::AIO::munlock $scalar, $offset = 0, $length = undef
221 IO::AIO::munlockall
448 222
449 IO::AIO::REQ CLASS 223 AIO REQUEST FUNCTIONS
450 All non-aggregate "aio_*" functions return an object of this class 224 All the "aio_*" calls are more or less thin wrappers around the syscall
451 when called in non-void context. 225 with the same name (sans "aio_"). The arguments are similar or
226 identical, and they all accept an additional (and optional) $callback
227 argument which must be a code reference. This code reference will get
228 called with the syscall return code (e.g. most syscalls return -1 on
229 error, unlike perl, which usually delivers "false") as its sole argument
230 after the given syscall has been executed asynchronously.
452 231
453 cancel $req 232 All functions expecting a filehandle keep a copy of the filehandle
454 Cancels the request, if possible. Has the effect of skipping 233 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.
460 234
461 cb $req $callback->(...) 235 All functions return request objects of type IO::AIO::REQ that allow
462 Replace (or simply set) the callback registered to the request. 236 further manipulation of those requests while they are in-flight.
463 237
464 IO::AIO::GRP CLASS 238 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 239 as octets. The reason for the former is that at the time the request is
466 to objects of this class, too. 240 being executed, the current working directory could have changed.
241 Alternatively, you can make sure that you never change the current
242 working directory anywhere in the program and then use relative paths.
467 243
468 A IO::AIO::GRP object is a special request that can contain multiple 244 To encode pathnames as octets, either make sure you either: a) always
469 other aio requests. 245 pass in filenames you got from outside (command line, readdir etc.)
246 without tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module
247 and encode your pathnames to the locale (or other) encoding in effect in
248 the user environment, d) use Glib::filename_from_unicode on unicode
249 filenames or e) use something else to ensure your scalar has the correct
250 contents.
470 251
471 You create one by calling the "aio_group" constructing function with 252 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 253 handles correctly whether it is set or not.
473 entered the "done" state:
474 254
475 my $grp = aio_group sub { 255 $prev_pri = aioreq_pri [$pri]
476 print "all requests are done\n"; 256 Returns the priority value that would be used for the next request
477 }; 257 and, if $pri is given, sets the priority for the next aio request.
478 258
479 You add requests by calling the "add" method with one or more 259 The default priority is 0, the minimum and maximum priorities are -4
480 "IO::AIO::REQ" objects: 260 and 4, respectively. Requests with higher priority will be serviced
261 first.
481 262
482 $grp->add (aio_unlink "..."); 263 The priority will be reset to 0 after each call to one of the
264 "aio_*" functions.
483 265
484 add $grp aio_stat "...", sub { 266 Example: open a file with low priority, then read something from it
485 $_[0] or return $grp->result ("error"); 267 with higher priority so the read request is serviced before other
268 low priority open requests (potentially spamming the cache):
486 269
487 # add another request dynamically, if first succeeded 270 aioreq_pri -3;
488 add $grp aio_open "...", sub { 271 aio_open ..., sub {
489 $grp->result ("ok"); 272 return unless $_[0];
273
274 aioreq_pri -2;
275 aio_read $_[0], ..., sub {
276 ...
490 }; 277 };
491 }; 278 };
492 279
280 aioreq_nice $pri_adjust
281 Similar to "aioreq_pri", but subtracts the given value from the
282 current priority, so the effect is cumulative.
283
284 aio_open $pathname, $flags, $mode, $callback->($fh)
285 Asynchronously open or create a file and call the callback with a
286 newly created filehandle for the file.
287
288 The pathname passed to "aio_open" must be absolute. See API NOTES,
289 above, for an explanation.
290
291 The $flags argument is a bitmask. See the "Fcntl" module for a list.
292 They are the same as used by "sysopen".
293
294 Likewise, $mode specifies the mode of the newly created file, if it
295 didn't exist and "O_CREAT" has been given, just like perl's
296 "sysopen", except that it is mandatory (i.e. use 0 if you don't
297 create new files, and 0666 or 0777 if you do). Note that the $mode
298 will be modified by the umask in effect then the request is being
299 executed, so better never change the umask.
300
301 Example:
302
303 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
304 if ($_[0]) {
305 print "open successful, fh is $_[0]\n";
306 ...
307 } else {
308 die "open failed: $!\n";
309 }
310 };
311
312 In addition to all the common open modes/flags ("O_RDONLY",
313 "O_WRONLY", "O_RDWR", "O_CREAT", "O_TRUNC", "O_EXCL" and
314 "O_APPEND"), the following POSIX and non-POSIX constants are
315 available (missing ones on your system are, as usual, 0):
316
317 "O_ASYNC", "O_DIRECT", "O_NOATIME", "O_CLOEXEC", "O_NOCTTY",
318 "O_NOFOLLOW", "O_NONBLOCK", "O_EXEC", "O_SEARCH", "O_DIRECTORY",
319 "O_DSYNC", "O_RSYNC", "O_SYNC" and "O_TTY_INIT".
320
321 aio_close $fh, $callback->($status)
322 Asynchronously close a file and call the callback with the result
323 code.
324
325 Unfortunately, you can't do this to perl. Perl *insists* very
326 strongly on closing the file descriptor associated with the
327 filehandle itself.
328
329 Therefore, "aio_close" will not close the filehandle - instead it
330 will use dup2 to overwrite the file descriptor with the write-end of
331 a pipe (the pipe fd will be created on demand and will be cached).
332
333 Or in other words: the file descriptor will be closed, but it will
334 not be free for reuse until the perl filehandle is closed.
335
336 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
337 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
338 Reads or writes $length bytes from or to the specified $fh and
339 $offset into the scalar given by $data and offset $dataoffset and
340 calls the callback without the actual number of bytes read (or -1 on
341 error, just like the syscall).
342
343 "aio_read" will, like "sysread", shrink or grow the $data scalar to
344 offset plus the actual number of bytes read.
345
346 If $offset is undefined, then the current file descriptor offset
347 will be used (and updated), otherwise the file descriptor offset
348 will not be changed by these calls.
349
350 If $length is undefined in "aio_write", use the remaining length of
351 $data.
352
353 If $dataoffset is less than zero, it will be counted from the end of
354 $data.
355
356 The $data scalar *MUST NOT* be modified in any way while the request
357 is outstanding. Modifying it can result in segfaults or World War
358 III (if the necessary/optional hardware is installed).
359
360 Example: Read 15 bytes at offset 7 into scalar $buffer, starting at
361 offset 0 within the scalar:
362
363 aio_read $fh, 7, 15, $buffer, 0, sub {
364 $_[0] > 0 or die "read error: $!";
365 print "read $_[0] bytes: <$buffer>\n";
366 };
367
368 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
369 Tries to copy $length bytes from $in_fh to $out_fh. It starts
370 reading at byte offset $in_offset, and starts writing at the current
371 file offset of $out_fh. Because of that, it is not safe to issue
372 more than one "aio_sendfile" per $out_fh, as they will interfere
373 with each other. The same $in_fh works fine though, as this function
374 does not move or use the file offset of $in_fh.
375
376 Please note that "aio_sendfile" can read more bytes from $in_fh than
377 are written, and there is no way to find out how many more bytes
378 have been read from "aio_sendfile" alone, as "aio_sendfile" only
379 provides the number of bytes written to $out_fh. Only if the result
380 value equals $length one can assume that $length bytes have been
381 read.
382
383 Unlike with other "aio_" functions, it makes a lot of sense to use
384 "aio_sendfile" on non-blocking sockets, as long as one end
385 (typically the $in_fh) is a file - the file I/O will then be
386 asynchronous, while the socket I/O will be non-blocking. Note,
387 however, that you can run into a trap where "aio_sendfile" reads
388 some data with readahead, then fails to write all data, and when the
389 socket is ready the next time, the data in the cache is already
390 lost, forcing "aio_sendfile" to again hit the disk. Explicit
391 "aio_read" + "aio_write" let's you better control resource usage.
392
393 This call tries to make use of a native "sendfile"-like syscall to
394 provide zero-copy operation. For this to work, $out_fh should refer
395 to a socket, and $in_fh should refer to an mmap'able file.
396
397 If a native sendfile cannot be found or it fails with "ENOSYS",
398 "EINVAL", "ENOTSUP", "EOPNOTSUPP", "EAFNOSUPPORT", "EPROTOTYPE" or
399 "ENOTSOCK", it will be emulated, so you can call "aio_sendfile" on
400 any type of filehandle regardless of the limitations of the
401 operating system.
402
403 As native sendfile syscalls (as practically any non-POSIX interface
404 hacked together in a hurry to improve benchmark numbers) tend to be
405 rather buggy on many systems, this implementation tries to work
406 around some known bugs in Linux and FreeBSD kernels (probably
407 others, too), but that might fail, so you really really should check
408 the return value of "aio_sendfile" - fewre bytes than expected might
409 have been transferred.
410
411 aio_readahead $fh,$offset,$length, $callback->($retval)
412 "aio_readahead" populates the page cache with data from a file so
413 that subsequent reads from that file will not block on disk I/O. The
414 $offset argument specifies the starting point from which data is to
415 be read and $length specifies the number of bytes to be read. I/O is
416 performed in whole pages, so that offset is effectively rounded down
417 to a page boundary and bytes are read up to the next page boundary
418 greater than or equal to (off-set+length). "aio_readahead" does not
419 read beyond the end of the file. The current file offset of the file
420 is left unchanged.
421
422 If that syscall doesn't exist (likely if your OS isn't Linux) it
423 will be emulated by simply reading the data, which would have a
424 similar effect.
425
426 aio_stat $fh_or_path, $callback->($status)
427 aio_lstat $fh, $callback->($status)
428 Works like perl's "stat" or "lstat" in void context. The callback
429 will be called after the stat and the results will be available
430 using "stat _" or "-s _" etc...
431
432 The pathname passed to "aio_stat" must be absolute. See API NOTES,
433 above, for an explanation.
434
435 Currently, the stats are always 64-bit-stats, i.e. instead of
436 returning an error when stat'ing a large file, the results will be
437 silently truncated unless perl itself is compiled with large file
438 support.
439
440 To help interpret the mode and dev/rdev stat values, IO::AIO offers
441 the following constants and functions (if not implemented, the
442 constants will be 0 and the functions will either "croak" or fall
443 back on traditional behaviour).
444
445 "S_IFMT", "S_IFIFO", "S_IFCHR", "S_IFBLK", "S_IFLNK", "S_IFREG",
446 "S_IFDIR", "S_IFWHT", "S_IFSOCK", "IO::AIO::major $dev_t",
447 "IO::AIO::minor $dev_t", "IO::AIO::makedev $major, $minor".
448
449 Example: Print the length of /etc/passwd:
450
451 aio_stat "/etc/passwd", sub {
452 $_[0] and die "stat failed: $!";
453 print "size is ", -s _, "\n";
454 };
455
456 aio_statvfs $fh_or_path, $callback->($statvfs)
457 Works like the POSIX "statvfs" or "fstatvfs" syscalls, depending on
458 whether a file handle or path was passed.
459
460 On success, the callback is passed a hash reference with the
461 following members: "bsize", "frsize", "blocks", "bfree", "bavail",
462 "files", "ffree", "favail", "fsid", "flag" and "namemax". On
463 failure, "undef" is passed.
464
465 The following POSIX IO::AIO::ST_* constants are defined: "ST_RDONLY"
466 and "ST_NOSUID".
467
468 The following non-POSIX IO::AIO::ST_* flag masks are defined to
469 their correct value when available, or to 0 on systems that do not
470 support them: "ST_NODEV", "ST_NOEXEC", "ST_SYNCHRONOUS",
471 "ST_MANDLOCK", "ST_WRITE", "ST_APPEND", "ST_IMMUTABLE",
472 "ST_NOATIME", "ST_NODIRATIME" and "ST_RELATIME".
473
474 Example: stat "/wd" and dump out the data if successful.
475
476 aio_statvfs "/wd", sub {
477 my $f = $_[0]
478 or die "statvfs: $!";
479
480 use Data::Dumper;
481 say Dumper $f;
482 };
483
484 # result:
485 {
486 bsize => 1024,
487 bfree => 4333064312,
488 blocks => 10253828096,
489 files => 2050765568,
490 flag => 4096,
491 favail => 2042092649,
492 bavail => 4333064312,
493 ffree => 2042092649,
494 namemax => 255,
495 frsize => 1024,
496 fsid => 1810
497 }
498
499 aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
500 Works like perl's "utime" function (including the special case of
501 $atime and $mtime being undef). Fractional times are supported if
502 the underlying syscalls support them.
503
504 When called with a pathname, uses utimes(2) if available, otherwise
505 utime(2). If called on a file descriptor, uses futimes(2) if
506 available, otherwise returns ENOSYS, so this is not portable.
507
508 Examples:
509
510 # set atime and mtime to current time (basically touch(1)):
511 aio_utime "path", undef, undef;
512 # set atime to current time and mtime to beginning of the epoch:
513 aio_utime "path", time, undef; # undef==0
514
515 aio_chown $fh_or_path, $uid, $gid, $callback->($status)
516 Works like perl's "chown" function, except that "undef" for either
517 $uid or $gid is being interpreted as "do not change" (but -1 can
518 also be used).
519
520 Examples:
521
522 # same as "chown root path" in the shell:
523 aio_chown "path", 0, -1;
524 # same as above:
525 aio_chown "path", 0, undef;
526
527 aio_truncate $fh_or_path, $offset, $callback->($status)
528 Works like truncate(2) or ftruncate(2).
529
530 aio_chmod $fh_or_path, $mode, $callback->($status)
531 Works like perl's "chmod" function.
532
533 aio_unlink $pathname, $callback->($status)
534 Asynchronously unlink (delete) a file and call the callback with the
535 result code.
536
537 aio_mknod $path, $mode, $dev, $callback->($status)
538 [EXPERIMENTAL]
539
540 Asynchronously create a device node (or fifo). See mknod(2).
541
542 The only (POSIX-) portable way of calling this function is:
543
544 aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...
545
546 See "aio_stat" for info about some potentially helpful extra
547 constants and functions.
548
549 aio_link $srcpath, $dstpath, $callback->($status)
550 Asynchronously create a new link to the existing object at $srcpath
551 at the path $dstpath and call the callback with the result code.
552
553 aio_symlink $srcpath, $dstpath, $callback->($status)
554 Asynchronously create a new symbolic link to the existing object at
555 $srcpath at the path $dstpath and call the callback with the result
556 code.
557
558 aio_readlink $path, $callback->($link)
559 Asynchronously read the symlink specified by $path and pass it to
560 the callback. If an error occurs, nothing or undef gets passed to
561 the callback.
562
563 aio_realpath $path, $callback->($path)
564 Asynchronously make the path absolute and resolve any symlinks in
565 $path. The resulting path only consists of directories (Same as
566 Cwd::realpath).
567
568 This request can be used to get the absolute path of the current
569 working directory by passing it a path of . (a single dot).
570
571 aio_rename $srcpath, $dstpath, $callback->($status)
572 Asynchronously rename the object at $srcpath to $dstpath, just as
573 rename(2) and call the callback with the result code.
574
575 aio_mkdir $pathname, $mode, $callback->($status)
576 Asynchronously mkdir (create) a directory and call the callback with
577 the result code. $mode will be modified by the umask at the time the
578 request is executed, so do not change your umask.
579
580 aio_rmdir $pathname, $callback->($status)
581 Asynchronously rmdir (delete) a directory and call the callback with
582 the result code.
583
584 aio_readdir $pathname, $callback->($entries)
585 Unlike the POSIX call of the same name, "aio_readdir" reads an
586 entire directory (i.e. opendir + readdir + closedir). The entries
587 will not be sorted, and will NOT include the "." and ".." entries.
588
589 The callback is passed a single argument which is either "undef" or
590 an array-ref with the filenames.
591
592 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
593 Quite similar to "aio_readdir", but the $flags argument allows to
594 tune behaviour and output format. In case of an error, $entries will
595 be "undef".
596
597 The flags are a combination of the following constants, ORed
598 together (the flags will also be passed to the callback, possibly
599 modified):
600
601 IO::AIO::READDIR_DENTS
602 When this flag is off, then the callback gets an arrayref
603 consisting of names only (as with "aio_readdir"), otherwise it
604 gets an arrayref with "[$name, $type, $inode]" arrayrefs, each
605 describing a single directory entry in more detail.
606
607 $name is the name of the entry.
608
609 $type is one of the "IO::AIO::DT_xxx" constants:
610
611 "IO::AIO::DT_UNKNOWN", "IO::AIO::DT_FIFO", "IO::AIO::DT_CHR",
612 "IO::AIO::DT_DIR", "IO::AIO::DT_BLK", "IO::AIO::DT_REG",
613 "IO::AIO::DT_LNK", "IO::AIO::DT_SOCK", "IO::AIO::DT_WHT".
614
615 "IO::AIO::DT_UNKNOWN" means just that: readdir does not know. If
616 you need to know, you have to run stat yourself. Also, for speed
617 reasons, the $type scalars are read-only: you can not modify
618 them.
619
620 $inode is the inode number (which might not be exact on systems
621 with 64 bit inode numbers and 32 bit perls). This field has
622 unspecified content on systems that do not deliver the inode
623 information.
624
625 IO::AIO::READDIR_DIRS_FIRST
626 When this flag is set, then the names will be returned in an
627 order where likely directories come first, in optimal stat
628 order. This is useful when you need to quickly find directories,
629 or you want to find all directories while avoiding to stat()
630 each entry.
631
632 If the system returns type information in readdir, then this is
633 used to find directories directly. Otherwise, likely directories
634 are names beginning with ".", or otherwise names with no dots,
635 of which names with short names are tried first.
636
637 IO::AIO::READDIR_STAT_ORDER
638 When this flag is set, then the names will be returned in an
639 order suitable for stat()'ing each one. That is, when you plan
640 to stat() all files in the given directory, then the returned
641 order will likely be fastest.
642
643 If both this flag and "IO::AIO::READDIR_DIRS_FIRST" are
644 specified, then the likely dirs come first, resulting in a less
645 optimal stat order.
646
647 IO::AIO::READDIR_FOUND_UNKNOWN
648 This flag should not be set when calling "aio_readdirx".
649 Instead, it is being set by "aio_readdirx", when any of the
650 $type's found were "IO::AIO::DT_UNKNOWN". The absense of this
651 flag therefore indicates that all $type's are known, which can
652 be used to speed up some algorithms.
653
654 aio_load $path, $data, $callback->($status)
655 This is a composite request that tries to fully load the given file
656 into memory. Status is the same as with aio_read.
657
658 aio_copy $srcpath, $dstpath, $callback->($status)
659 Try to copy the *file* (directories not supported as either source
660 or destination) from $srcpath to $dstpath and call the callback with
661 a status of 0 (ok) or -1 (error, see $!).
662
663 This is a composite request that creates the destination file with
664 mode 0200 and copies the contents of the source file into it using
665 "aio_sendfile", followed by restoring atime, mtime, access mode and
666 uid/gid, in that order.
667
668 If an error occurs, the partial destination file will be unlinked,
669 if possible, except when setting atime, mtime, access mode and
670 uid/gid, where errors are being ignored.
671
672 aio_move $srcpath, $dstpath, $callback->($status)
673 Try to move the *file* (directories not supported as either source
674 or destination) from $srcpath to $dstpath and call the callback with
675 a status of 0 (ok) or -1 (error, see $!).
676
677 This is a composite request that tries to rename(2) the file first;
678 if rename fails with "EXDEV", it copies the file with "aio_copy"
679 and, if that is successful, unlinks the $srcpath.
680
681 aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
682 Scans a directory (similar to "aio_readdir") but additionally tries
683 to efficiently separate the entries of directory $path into two sets
684 of names, directories you can recurse into (directories), and ones
685 you cannot recurse into (everything else, including symlinks to
686 directories).
687
688 "aio_scandir" is a composite request that creates of many sub
689 requests_ $maxreq specifies the maximum number of outstanding aio
690 requests that this function generates. If it is "<= 0", then a
691 suitable default will be chosen (currently 4).
692
693 On error, the callback is called without arguments, otherwise it
694 receives two array-refs with path-relative entry names.
695
696 Example:
697
698 aio_scandir $dir, 0, sub {
699 my ($dirs, $nondirs) = @_;
700 print "real directories: @$dirs\n";
701 print "everything else: @$nondirs\n";
702 };
703
704 Implementation notes.
705
706 The "aio_readdir" cannot be avoided, but "stat()"'ing every entry
707 can.
708
709 If readdir returns file type information, then this is used directly
710 to find directories.
711
712 Otherwise, after reading the directory, the modification time, size
713 etc. of the directory before and after the readdir is checked, and
714 if they match (and isn't the current time), the link count will be
715 used to decide how many entries are directories (if >= 2).
716 Otherwise, no knowledge of the number of subdirectories will be
717 assumed.
718
719 Then entries will be sorted into likely directories a non-initial
720 dot currently) and likely non-directories (see "aio_readdirx"). Then
721 every entry plus an appended "/." will be "stat"'ed, likely
722 directories first, in order of their inode numbers. If that
723 succeeds, it assumes that the entry is a directory or a symlink to
724 directory (which will be checked seperately). This is often faster
725 than stat'ing the entry itself because filesystems might detect the
726 type of the entry without reading the inode data (e.g. ext2fs
727 filetype feature), even on systems that cannot return the filetype
728 information on readdir.
729
730 If the known number of directories (link count - 2) has been
731 reached, the rest of the entries is assumed to be non-directories.
732
733 This only works with certainty on POSIX (= UNIX) filesystems, which
734 fortunately are the vast majority of filesystems around.
735
736 It will also likely work on non-POSIX filesystems with reduced
737 efficiency as those tend to return 0 or 1 as link counts, which
738 disables the directory counting heuristic.
739
740 aio_rmtree $path, $callback->($status)
741 Delete a directory tree starting (and including) $path, return the
742 status of the final "rmdir" only. This is a composite request that
743 uses "aio_scandir" to recurse into and rmdir directories, and unlink
744 everything else.
745
746 aio_sync $callback->($status)
747 Asynchronously call sync and call the callback when finished.
748
749 aio_fsync $fh, $callback->($status)
750 Asynchronously call fsync on the given filehandle and call the
751 callback with the fsync result code.
752
753 aio_fdatasync $fh, $callback->($status)
754 Asynchronously call fdatasync on the given filehandle and call the
755 callback with the fdatasync result code.
756
757 If this call isn't available because your OS lacks it or it couldn't
758 be detected, it will be emulated by calling "fsync" instead.
759
760 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
761 Sync the data portion of the file specified by $offset and $length
762 to disk (but NOT the metadata), by calling the Linux-specific
763 sync_file_range call. If sync_file_range is not available or it
764 returns ENOSYS, then fdatasync or fsync is being substituted.
765
766 $flags can be a combination of
767 "IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE",
768 "IO::AIO::SYNC_FILE_RANGE_WRITE" and
769 "IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER": refer to the sync_file_range
770 manpage for details.
771
772 aio_pathsync $path, $callback->($status)
773 This request tries to open, fsync and close the given path. This is
774 a composite request intended to sync directories after directory
775 operations (E.g. rename). This might not work on all operating
776 systems or have any specific effect, but usually it makes sure that
777 directory changes get written to disc. It works for anything that
778 can be opened for read-only, not just directories.
779
780 Future versions of this function might fall back to other methods
781 when "fsync" on the directory fails (such as calling "sync").
782
783 Passes 0 when everything went ok, and -1 on error.
784
785 aio_msync $scalar, $offset = 0, $length = undef, flags = 0,
786 $callback->($status)
787 This is a rather advanced IO::AIO call, which only works on
788 mmap(2)ed scalars (see the "IO::AIO::mmap" function, although it
789 also works on data scalars managed by the Sys::Mmap or Mmap modules,
790 note that the scalar must only be modified in-place while an aio
791 operation is pending on it).
792
793 It calls the "msync" function of your OS, if available, with the
794 memory area starting at $offset in the string and ending $length
795 bytes later. If $length is negative, counts from the end, and if
796 $length is "undef", then it goes till the end of the string. The
797 flags can be a combination of "IO::AIO::MS_ASYNC",
798 "IO::AIO::MS_INVALIDATE" and "IO::AIO::MS_SYNC".
799
800 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0,
801 $callback->($status)
802 This is a rather advanced IO::AIO call, which works best on
803 mmap(2)ed scalars.
804
805 It touches (reads or writes) all memory pages in the specified range
806 inside the scalar. All caveats and parameters are the same as for
807 "aio_msync", above, except for flags, which must be either 0 (which
808 reads all pages and ensures they are instantiated) or
809 "IO::AIO::MT_MODIFY", which modifies the memory page s(by reading
810 and writing an octet from it, which dirties the page).
811
812 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
813 This is a rather advanced IO::AIO call, which works best on
814 mmap(2)ed scalars.
815
816 It reads in all the pages of the underlying storage into memory (if
817 any) and locks them, so they are not getting swapped/paged out or
818 removed.
819
820 If $length is undefined, then the scalar will be locked till the
821 end.
822
823 On systems that do not implement "mlock", this function returns -1
824 and sets errno to "ENOSYS".
825
826 Note that the corresponding "munlock" is synchronous and is
827 documented under "MISCELLANEOUS FUNCTIONS".
828
829 Example: open a file, mmap and mlock it - both will be undone when
830 $data gets destroyed.
831
832 open my $fh, "<", $path or die "$path: $!";
833 my $data;
834 IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
835 aio_mlock $data; # mlock in background
836
837 aio_mlockall $flags, $callback->($status)
838 Calls the "mlockall" function with the given $flags (a combination
839 of "IO::AIO::MCL_CURRENT" and "IO::AIO::MCL_FUTURE").
840
841 On systems that do not implement "mlockall", this function returns
842 -1 and sets errno to "ENOSYS".
843
844 Note that the corresponding "munlockall" is synchronous and is
845 documented under "MISCELLANEOUS FUNCTIONS".
846
847 Example: asynchronously lock all current and future pages into
848 memory.
849
850 aio_mlockall IO::AIO::MCL_FUTURE;
851
852 aio_group $callback->(...)
853 This is a very special aio request: Instead of doing something, it
854 is a container for other aio requests, which is useful if you want
855 to bundle many requests into a single, composite, request with a
856 definite callback and the ability to cancel the whole request with
857 its subrequests.
858
859 Returns an object of class IO::AIO::GRP. See its documentation below
860 for more info.
861
862 Example:
863
864 my $grp = aio_group sub {
865 print "all stats done\n";
866 };
867
868 add $grp
869 (aio_stat ...),
870 (aio_stat ...),
871 ...;
872
873 aio_nop $callback->()
874 This is a special request - it does nothing in itself and is only
875 used for side effects, such as when you want to add a dummy request
876 to a group so that finishing the requests in the group depends on
877 executing the given code.
878
879 While this request does nothing, it still goes through the execution
880 phase and still requires a worker thread. Thus, the callback will
881 not be executed immediately but only after other requests in the
882 queue have entered their execution phase. This can be used to
883 measure request latency.
884
885 IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
886 Mainly used for debugging and benchmarking, this aio request puts
887 one of the request workers to sleep for the given time.
888
889 While it is theoretically handy to have simple I/O scheduling
890 requests like sleep and file handle readable/writable, the overhead
891 this creates is immense (it blocks a thread for a long time) so do
892 not use this function except to put your application under
893 artificial I/O pressure.
894
895 IO::AIO::REQ CLASS
896 All non-aggregate "aio_*" functions return an object of this class when
897 called in non-void context.
898
899 cancel $req
900 Cancels the request, if possible. Has the effect of skipping
901 execution when entering the execute state and skipping calling the
902 callback when entering the the result state, but will leave the
903 request otherwise untouched (with the exception of readdir). That
904 means that requests that currently execute will not be stopped and
905 resources held by the request will not be freed prematurely.
906
907 cb $req $callback->(...)
908 Replace (or simply set) the callback registered to the request.
909
910 IO::AIO::GRP CLASS
911 This class is a subclass of IO::AIO::REQ, so all its methods apply to
912 objects of this class, too.
913
914 A IO::AIO::GRP object is a special request that can contain multiple
915 other aio requests.
916
917 You create one by calling the "aio_group" constructing function with a
918 callback that will be called when all contained requests have entered
919 the "done" state:
920
921 my $grp = aio_group sub {
922 print "all requests are done\n";
923 };
924
925 You add requests by calling the "add" method with one or more
926 "IO::AIO::REQ" objects:
927
928 $grp->add (aio_unlink "...");
929
930 add $grp aio_stat "...", sub {
931 $_[0] or return $grp->result ("error");
932
933 # add another request dynamically, if first succeeded
934 add $grp aio_open "...", sub {
935 $grp->result ("ok");
936 };
937 };
938
493 This makes it very easy to create composite requests (see the source 939 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 940 "aio_move" for an application) that work and feel like simple requests.
941
942 * The IO::AIO::GRP objects will be cleaned up during calls to
943 "IO::AIO::poll_cb", just like any other request.
944
945 * They can be canceled like any other request. Canceling will cancel
946 not only the request itself, but also all requests it contains.
947
948 * They can also can also be added to other IO::AIO::GRP objects.
949
950 * You must not add requests to a group from within the group callback
951 (or any later time).
952
953 Their lifetime, simplified, looks like this: when they are empty, they
954 will finish very quickly. If they contain only requests that are in the
955 "done" state, they will also finish. Otherwise they will continue to
956 exist.
957
958 That means after creating a group you have some time to add requests
959 (precisely before the callback has been invoked, which is only done
960 within the "poll_cb"). And in the callbacks of those requests, you can
961 add further requests to the group. And only when all those requests have
962 finished will the the group itself finish.
963
964 add $grp ...
965 $grp->add (...)
966 Add one or more requests to the group. Any type of IO::AIO::REQ can
967 be added, including other groups, as long as you do not create
968 circular dependencies.
969
970 Returns all its arguments.
971
972 $grp->cancel_subs
973 Cancel all subrequests and clears any feeder, but not the group
974 request itself. Useful when you queued a lot of events but got a
975 result early.
976
977 The group request will finish normally (you cannot add requests to
978 the group).
979
980 $grp->result (...)
981 Set the result value(s) that will be passed to the group callback
982 when all subrequests have finished and set the groups errno to the
983 current value of errno (just like calling "errno" without an error
984 number). By default, no argument will be passed and errno is zero.
985
986 $grp->errno ([$errno])
987 Sets the group errno value to $errno, or the current value of errno
988 when the argument is missing.
989
990 Every aio request has an associated errno value that is restored
991 when the callback is invoked. This method lets you change this value
992 from its default (0).
993
994 Calling "result" will also set errno, so make sure you either set $!
995 before the call to "result", or call c<errno> after it.
996
997 feed $grp $callback->($grp)
998 Sets a feeder/generator on this group: every group can have an
999 attached generator that generates requests if idle. The idea behind
1000 this is that, although you could just queue as many requests as you
1001 want in a group, this might starve other requests for a potentially
1002 long time. For example, "aio_scandir" might generate hundreds of
1003 thousands "aio_stat" requests, delaying any later requests for a
1004 long time.
1005
1006 To avoid this, and allow incremental generation of requests, you can
1007 instead a group and set a feeder on it that generates those
1008 requests. The feed callback will be called whenever there are few
1009 enough (see "limit", below) requests active in the group itself and
1010 is expected to queue more requests.
1011
1012 The feed callback can queue as many requests as it likes (i.e. "add"
1013 does not impose any limits).
1014
1015 If the feed does not queue more requests when called, it will be
1016 automatically removed from the group.
1017
1018 If the feed limit is 0 when this method is called, it will be set to
1019 2 automatically.
1020
1021 Example:
1022
1023 # stat all files in @files, but only ever use four aio requests concurrently:
1024
1025 my $grp = aio_group sub { print "finished\n" };
1026 limit $grp 4;
1027 feed $grp sub {
1028 my $file = pop @files
1029 or return;
1030
1031 add $grp aio_stat $file, sub { ... };
1032 };
1033
1034 limit $grp $num
1035 Sets the feeder limit for the group: The feeder will be called
1036 whenever the group contains less than this many requests.
1037
1038 Setting the limit to 0 will pause the feeding process.
1039
1040 The default value for the limit is 0, but note that setting a feeder
1041 automatically bumps it up to 2.
1042
1043 SUPPORT FUNCTIONS
1044 EVENT PROCESSING AND EVENT LOOP INTEGRATION
1045 $fileno = IO::AIO::poll_fileno
1046 Return the *request result pipe file descriptor*. This filehandle
1047 must be polled for reading by some mechanism outside this module
1048 (e.g. EV, Glib, select and so on, see below or the SYNOPSIS). If the
1049 pipe becomes readable you have to call "poll_cb" to check the
1050 results.
1051
1052 See "poll_cb" for an example.
1053
1054 IO::AIO::poll_cb
1055 Process some outstanding events on the result pipe. You have to call
1056 this regularly. Returns 0 if all events could be processed (or there
1057 were no events to process), or -1 if it returned earlier for
1058 whatever reason. Returns immediately when no events are outstanding.
1059 The amount of events processed depends on the settings of
1060 "IO::AIO::max_poll_req" and "IO::AIO::max_poll_time".
1061
1062 If not all requests were processed for whatever reason, the
1063 filehandle will still be ready when "poll_cb" returns, so normally
1064 you don't have to do anything special to have it called later.
1065
1066 Apart from calling "IO::AIO::poll_cb" when the event filehandle
1067 becomes ready, it can be beneficial to call this function from loops
1068 which submit a lot of requests, to make sure the results get
1069 processed when they become available and not just when the loop is
1070 finished and the event loop takes over again. This function returns
1071 very fast when there are no outstanding requests.
1072
1073 Example: Install an Event watcher that automatically calls
1074 IO::AIO::poll_cb with high priority (more examples can be found in
1075 the SYNOPSIS section, at the top of this document):
1076
1077 Event->io (fd => IO::AIO::poll_fileno,
1078 poll => 'r', async => 1,
1079 cb => \&IO::AIO::poll_cb);
1080
1081 IO::AIO::poll_wait
1082 If there are any outstanding requests and none of them in the result
1083 phase, wait till the result filehandle becomes ready for reading
1084 (simply does a "select" on the filehandle. This is useful if you
1085 want to synchronously wait for some requests to finish).
1086
1087 See "nreqs" for an example.
1088
1089 IO::AIO::poll
1090 Waits until some requests have been handled.
1091
1092 Returns the number of requests processed, but is otherwise strictly
1093 equivalent to:
1094
1095 IO::AIO::poll_wait, IO::AIO::poll_cb
1096
1097 IO::AIO::flush
1098 Wait till all outstanding AIO requests have been handled.
1099
1100 Strictly equivalent to:
1101
1102 IO::AIO::poll_wait, IO::AIO::poll_cb
1103 while IO::AIO::nreqs;
1104
1105 IO::AIO::max_poll_reqs $nreqs
1106 IO::AIO::max_poll_time $seconds
1107 These set the maximum number of requests (default 0, meaning
1108 infinity) that are being processed by "IO::AIO::poll_cb" in one
1109 call, respectively the maximum amount of time (default 0, meaning
1110 infinity) spent in "IO::AIO::poll_cb" to process requests (more
1111 correctly the mininum amount of time "poll_cb" is allowed to use).
1112
1113 Setting "max_poll_time" to a non-zero value creates an overhead of
1114 one syscall per request processed, which is not normally a problem
1115 unless your callbacks are really really fast or your OS is really
1116 really slow (I am not mentioning Solaris here). Using
1117 "max_poll_reqs" incurs no overhead.
1118
1119 Setting these is useful if you want to ensure some level of
1120 interactiveness when perl is not fast enough to process all requests
1121 in time.
1122
1123 For interactive programs, values such as 0.01 to 0.1 should be fine.
1124
1125 Example: Install an Event watcher that automatically calls
1126 IO::AIO::poll_cb with low priority, to ensure that other parts of
1127 the program get the CPU sometimes even under high AIO load.
1128
1129 # try not to spend much more than 0.1s in poll_cb
1130 IO::AIO::max_poll_time 0.1;
1131
1132 # use a low priority so other tasks have priority
1133 Event->io (fd => IO::AIO::poll_fileno,
1134 poll => 'r', nice => 1,
1135 cb => &IO::AIO::poll_cb);
1136
1137 CONTROLLING THE NUMBER OF THREADS
1138 IO::AIO::min_parallel $nthreads
1139 Set the minimum number of AIO threads to $nthreads. The current
1140 default is 8, which means eight asynchronous operations can execute
1141 concurrently at any one time (the number of outstanding requests,
1142 however, is unlimited).
1143
1144 IO::AIO starts threads only on demand, when an AIO request is queued
1145 and no free thread exists. Please note that queueing up a hundred
1146 requests can create demand for a hundred threads, even if it turns
1147 out that everything is in the cache and could have been processed
1148 faster by a single thread.
1149
1150 It is recommended to keep the number of threads relatively low, as
1151 some Linux kernel versions will scale negatively with the number of
1152 threads (higher parallelity => MUCH higher latency). With current
1153 Linux 2.6 versions, 4-32 threads should be fine.
1154
1155 Under most circumstances you don't need to call this function, as
1156 the module selects a default that is suitable for low to moderate
1157 load.
1158
1159 IO::AIO::max_parallel $nthreads
1160 Sets the maximum number of AIO threads to $nthreads. If more than
1161 the specified number of threads are currently running, this function
1162 kills them. This function blocks until the limit is reached.
1163
1164 While $nthreads are zero, aio requests get queued but not executed
1165 until the number of threads has been increased again.
1166
1167 This module automatically runs "max_parallel 0" at program end, to
1168 ensure that all threads are killed and that there are no outstanding
495 requests. 1169 requests.
496 1170
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. 1171 Under normal circumstances you don't need to call this function.
701 1172
1173 IO::AIO::max_idle $nthreads
1174 Limit the number of threads (default: 4) that are allowed to idle
1175 (i.e., threads that did not get a request to process within the idle
1176 timeout (default: 10 seconds). That means if a thread becomes idle
1177 while $nthreads other threads are also idle, it will free its
1178 resources and exit.
1179
1180 This is useful when you allow a large number of threads (e.g. 100 or
1181 1000) to allow for extremely high load situations, but want to free
1182 resources under normal circumstances (1000 threads can easily
1183 consume 30MB of RAM).
1184
1185 The default is probably ok in most situations, especially if thread
1186 creation is fast. If thread creation is very slow on your system you
1187 might want to use larger values.
1188
1189 IO::AIO::idle_timeout $seconds
1190 Sets the minimum idle timeout (default 10) after which worker
1191 threads are allowed to exit. SEe "IO::AIO::max_idle".
1192
702 $oldmaxreqs = IO::AIO::max_outstanding $maxreqs 1193 IO::AIO::max_outstanding $maxreqs
703 This is a very bad function to use in interactive programs
704 because it blocks, and a bad way to reduce concurrency because
705 it is inexact: Better use an "aio_group" together with a feed
706 callback.
707
708 Sets the maximum number of outstanding requests to $nreqs. If 1194 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 1195 queue up more than this number of requests, the next call to
710 to the "poll_cb" (and "poll_some" and other functions calling 1196 "IO::AIO::poll_cb" (and other functions calling "poll_cb", such as
711 "poll_cb") function will block until the limit is no longer 1197 "IO::AIO::flush" or "IO::AIO::poll") will block until the limit is
712 exceeded. 1198 no longer exceeded.
713 1199
714 The default value is very large, so there is no practical limit 1200 In other words, this setting does not enforce a queue limit, but can
1201 be used to make poll functions block if the limit is exceeded.
1202
1203 This is a very bad function to use in interactive programs because
1204 it blocks, and a bad way to reduce concurrency because it is
1205 inexact: Better use an "aio_group" together with a feed callback.
1206
1207 It's main use is in scripts without an event loop - when you want to
1208 stat a lot of files, you can write somehting like this:
1209
1210 IO::AIO::max_outstanding 32;
1211
1212 for my $path (...) {
1213 aio_stat $path , ...;
1214 IO::AIO::poll_cb;
1215 }
1216
1217 IO::AIO::flush;
1218
1219 The call to "poll_cb" inside the loop will normally return
1220 instantly, but as soon as more thna 32 reqeusts are in-flight, it
1221 will block until some requests have been handled. This keeps the
1222 loop from pushing a large number of "aio_stat" requests onto the
1223 queue.
1224
1225 The default value for "max_outstanding" is very large, so there is
715 on the number of outstanding requests. 1226 no practical limit on the number of outstanding requests.
716 1227
717 You can still queue as many requests as you want. Therefore, 1228 STATISTICAL INFORMATION
718 "max_oustsanding" is mainly useful in simple scripts (with low 1229 IO::AIO::nreqs
719 values) or as a stop gap to shield against fatal memory overflow 1230 Returns the number of requests currently in the ready, execute or
720 (with large values). 1231 pending states (i.e. for which their callback has not been invoked
1232 yet).
1233
1234 Example: wait till there are no outstanding requests anymore:
1235
1236 IO::AIO::poll_wait, IO::AIO::poll_cb
1237 while IO::AIO::nreqs;
1238
1239 IO::AIO::nready
1240 Returns the number of requests currently in the ready state (not yet
1241 executed).
1242
1243 IO::AIO::npending
1244 Returns the number of requests currently in the pending state
1245 (executed, but not yet processed by poll_cb).
1246
1247 MISCELLANEOUS FUNCTIONS
1248 IO::AIO implements some functions that might be useful, but are not
1249 asynchronous.
1250
1251 IO::AIO::sendfile $ofh, $ifh, $offset, $count
1252 Calls the "eio_sendfile_sync" function, which is like
1253 "aio_sendfile", but is blocking (this makes most sense if you know
1254 the input data is likely cached already and the output filehandle is
1255 set to non-blocking operations).
1256
1257 Returns the number of bytes copied, or -1 on error.
1258
1259 IO::AIO::fadvise $fh, $offset, $len, $advice
1260 Simply calls the "posix_fadvise" function (see its manpage for
1261 details). The following advice constants are avaiable:
1262 "IO::AIO::FADV_NORMAL", "IO::AIO::FADV_SEQUENTIAL",
1263 "IO::AIO::FADV_RANDOM", "IO::AIO::FADV_NOREUSE",
1264 "IO::AIO::FADV_WILLNEED", "IO::AIO::FADV_DONTNEED".
1265
1266 On systems that do not implement "posix_fadvise", this function
1267 returns ENOSYS, otherwise the return value of "posix_fadvise".
1268
1269 IO::AIO::madvise $scalar, $offset, $len, $advice
1270 Simply calls the "posix_madvise" function (see its manpage for
1271 details). The following advice constants are avaiable:
1272 "IO::AIO::MADV_NORMAL", "IO::AIO::MADV_SEQUENTIAL",
1273 "IO::AIO::MADV_RANDOM", "IO::AIO::MADV_WILLNEED",
1274 "IO::AIO::MADV_DONTNEED".
1275
1276 On systems that do not implement "posix_madvise", this function
1277 returns ENOSYS, otherwise the return value of "posix_madvise".
1278
1279 IO::AIO::mprotect $scalar, $offset, $len, $protect
1280 Simply calls the "mprotect" function on the preferably AIO::mmap'ed
1281 $scalar (see its manpage for details). The following protect
1282 constants are avaiable: "IO::AIO::PROT_NONE", "IO::AIO::PROT_READ",
1283 "IO::AIO::PROT_WRITE", "IO::AIO::PROT_EXEC".
1284
1285 On systems that do not implement "mprotect", this function returns
1286 ENOSYS, otherwise the return value of "mprotect".
1287
1288 IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
1289 Memory-maps a file (or anonymous memory range) and attaches it to
1290 the given $scalar, which will act like a string scalar.
1291
1292 The only operations allowed on the scalar are "substr"/"vec" that
1293 don't change the string length, and most read-only operations such
1294 as copying it or searching it with regexes and so on.
1295
1296 Anything else is unsafe and will, at best, result in memory leaks.
1297
1298 The memory map associated with the $scalar is automatically removed
1299 when the $scalar is destroyed, or when the "IO::AIO::mmap" or
1300 "IO::AIO::munmap" functions are called.
1301
1302 This calls the "mmap"(2) function internally. See your system's
1303 manual page for details on the $length, $prot and $flags parameters.
1304
1305 The $length must be larger than zero and smaller than the actual
1306 filesize.
1307
1308 $prot is a combination of "IO::AIO::PROT_NONE",
1309 "IO::AIO::PROT_EXEC", "IO::AIO::PROT_READ" and/or
1310 "IO::AIO::PROT_WRITE",
1311
1312 $flags can be a combination of "IO::AIO::MAP_SHARED" or
1313 "IO::AIO::MAP_PRIVATE", or a number of system-specific flags (when
1314 not available, the are defined as 0): "IO::AIO::MAP_ANONYMOUS"
1315 (which is set to "MAP_ANON" if your system only provides this
1316 constant), "IO::AIO::MAP_HUGETLB", "IO::AIO::MAP_LOCKED",
1317 "IO::AIO::MAP_NORESERVE", "IO::AIO::MAP_POPULATE" or
1318 "IO::AIO::MAP_NONBLOCK"
1319
1320 If $fh is "undef", then a file descriptor of -1 is passed.
1321
1322 $offset is the offset from the start of the file - it generally must
1323 be a multiple of "IO::AIO::PAGESIZE" and defaults to 0.
1324
1325 Example:
1326
1327 use Digest::MD5;
1328 use IO::AIO;
1329
1330 open my $fh, "<verybigfile"
1331 or die "$!";
1332
1333 IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
1334 or die "verybigfile: $!";
1335
1336 my $fast_md5 = md5 $data;
1337
1338 IO::AIO::munmap $scalar
1339 Removes a previous mmap and undefines the $scalar.
1340
1341 IO::AIO::munlock $scalar, $offset = 0, $length = undef
1342 Calls the "munlock" function, undoing the effects of a previous
1343 "aio_mlock" call (see its description for details).
1344
1345 IO::AIO::munlockall
1346 Calls the "munlockall" function.
1347
1348 On systems that do not implement "munlockall", this function returns
1349 ENOSYS, otherwise the return value of "munlockall".
1350
1351EVENT LOOP INTEGRATION
1352 It is recommended to use AnyEvent::AIO to integrate IO::AIO
1353 automatically into many event loops:
1354
1355 # AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
1356 use AnyEvent::AIO;
1357
1358 You can also integrate IO::AIO manually into many event loops, here are
1359 some examples of how to do this:
1360
1361 # EV integration
1362 my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
1363
1364 # Event integration
1365 Event->io (fd => IO::AIO::poll_fileno,
1366 poll => 'r',
1367 cb => \&IO::AIO::poll_cb);
1368
1369 # Glib/Gtk2 integration
1370 add_watch Glib::IO IO::AIO::poll_fileno,
1371 in => sub { IO::AIO::poll_cb; 1 };
1372
1373 # Tk integration
1374 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
1375 readable => \&IO::AIO::poll_cb);
1376
1377 # Danga::Socket integration
1378 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
1379 \&IO::AIO::poll_cb);
721 1380
722 FORK BEHAVIOUR 1381 FORK BEHAVIOUR
723 This module should do "the right thing" when the process using it 1382 Usage of pthreads in a program changes the semantics of fork
724 forks: 1383 considerably. Specifically, only async-safe functions can be called
1384 after fork. Perl doesn't know about this, so in general, you cannot call
1385 fork with defined behaviour in perl if pthreads are involved. IO::AIO
1386 uses pthreads, so this applies, but many other extensions and (for
1387 inexplicable reasons) perl itself often is linked against pthreads, so
1388 this limitation applies to quite a lot of perls.
725 1389
726 Before the fork, IO::AIO enters a quiescent state where no requests 1390 This module no longer tries to fight your OS, or POSIX. That means
727 can be added in other threads and no results will be processed. 1391 IO::AIO only works in the process that loaded it. Forking is fully
728 After the fork the parent simply leaves the quiescent state and 1392 supported, but using IO::AIO in the child is not.
729 continues request/result processing, while the child frees the
730 request/result queue (so that the requests started before the fork
731 will only be handled in the parent). Threads will be started on
732 demand until the limit set in the parent process has been reached
733 again.
734 1393
735 In short: the parent will, after a short pause, continue as if fork 1394 You might get around by not *using* IO::AIO before (or after) forking.
736 had not been called, while the child will act as if IO::AIO has not 1395 You could also try to call the IO::AIO::reinit function in the child:
737 been used yet. 1396
1397 IO::AIO::reinit
1398 Abondons all current requests and I/O threads and simply
1399 reinitialises all data structures. This is not an operation
1400 suppported by any standards, but happens to work on GNU/Linux and
1401 some newer BSD systems.
1402
1403 The only reasonable use for this function is to call it after
1404 forking, if "IO::AIO" was used in the parent. Calling it while
1405 IO::AIO is active in the process will result in undefined behaviour.
1406 Calling it at any time will also result in any undefined (by POSIX)
1407 behaviour.
738 1408
739 MEMORY USAGE 1409 MEMORY USAGE
740 Per-request usage: 1410 Per-request usage:
741 1411
742 Each aio request uses - depending on your architecture - around 1412 Each aio request uses - depending on your architecture - around 100-200
743 100-200 bytes of memory. In addition, stat requests need a stat 1413 bytes of memory. In addition, stat requests need a stat buffer (possibly
744 buffer (possibly a few hundred bytes), readdir requires a result 1414 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 1415 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 1416 will consume memory till the request has entered the done state.
747 request has entered the done state.
748 1417
749 This is now awfully much, so queuing lots of requests is not usually 1418 This is not awfully much, so queuing lots of requests is not usually a
750 a problem. 1419 problem.
751 1420
752 Per-thread usage: 1421 Per-thread usage:
753 1422
754 In the execution phase, some aio requests require more memory for 1423 In the execution phase, some aio requests require more memory for
755 temporary buffers, and each thread requires a stack and other data 1424 temporary buffers, and each thread requires a stack and other data
756 structures (usually around 16k-128k, depending on the OS). 1425 structures (usually around 16k-128k, depending on the OS).
757 1426
758KNOWN BUGS 1427KNOWN BUGS
759 Known bugs will be fixed in the next release. 1428 Known bugs will be fixed in the next release.
760 1429
761SEE ALSO 1430SEE ALSO
762 Coro::AIO. 1431 AnyEvent::AIO for easy integration into event loops, Coro::AIO for a
1432 more natural syntax.
763 1433
764AUTHOR 1434AUTHOR
765 Marc Lehmann <schmorp@schmorp.de> 1435 Marc Lehmann <schmorp@schmorp.de>
766 http://home.schmorp.de/ 1436 http://home.schmorp.de/
767 1437

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