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Revision 1.44 by root, Mon Nov 1 22:03:43 2010 UTC

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2 IO::AIO - Asynchronous Input/Output 2 IO::AIO - Asynchronous Input/Output
3 3
4SYNOPSIS 4SYNOPSIS
5 use IO::AIO; 5 use IO::AIO;
6 6
7 aio_open "/etc/passwd", O_RDONLY, 0, sub { 7 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
8 my ($fh) = @_; 8 my $fh = shift
9 or die "/etc/passwd: $!";
9 ... 10 ...
10 }; 11 };
11 12
12 aio_unlink "/tmp/file", sub { }; 13 aio_unlink "/tmp/file", sub { };
13 14
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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>).
52 33
53 Asynchronous means that operations that can normally block your program 34 Asynchronous means that operations that can normally block your program
54 (e.g. reading from disk) will be done asynchronously: the operation will 35 (e.g. reading from disk) will be done asynchronously: the operation will
55 still block, but you can do something else in the meantime. This is 36 still block, but you can do something else in the meantime. This is
56 extremely useful for programs that need to stay interactive even when 37 extremely useful for programs that need to stay interactive even when
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58 but can also be used to easily do operations in parallel that are 39 but can also be used to easily do operations in parallel that are
59 normally done sequentially, e.g. stat'ing many files, which is much 40 normally done sequentially, e.g. stat'ing many files, which is much
60 faster on a RAID volume or over NFS when you do a number of stat 41 faster on a RAID volume or over NFS when you do a number of stat
61 operations concurrently. 42 operations concurrently.
62 43
63 While this works on all types of file descriptors (for example sockets), 44 While most of this works on all types of file descriptors (for example
64 using these functions on file descriptors that support nonblocking 45 sockets), using these functions on file descriptors that support
65 operation (again, sockets, pipes etc.) is very inefficient. Use an event 46 nonblocking operation (again, sockets, pipes etc.) is very inefficient.
66 loop for that (such as the Event module): IO::AIO will naturally fit 47 Use an event loop for that (such as the EV module): IO::AIO will
67 into such an event loop itself. 48 naturally fit into such an event loop itself.
68 49
69 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
70 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
71 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
72 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
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74 not well-supported or restricted (GNU/Linux doesn't allow them on normal 55 not well-supported or restricted (GNU/Linux doesn't allow them on normal
75 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
76 aio_write, so the remaining functionality would have to be implemented 57 aio_write, so the remaining functionality would have to be implemented
77 using threads anyway. 58 using threads anyway.
78 59
79 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,
80 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
81 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
82 never call "poll_cb" (or other "aio_" functions) recursively. 63 call "poll_cb" (or other "aio_" functions) recursively.
83 64
84 EXAMPLE 65 EXAMPLE
85 This is a simple example that uses the Event module and loads 66 This is a simple example that uses the EV module and loads /etc/passwd
86 /etc/passwd asynchronously: 67 asynchronously:
87 68
88 use Fcntl; 69 use Fcntl;
89 use Event; 70 use EV;
90 use IO::AIO; 71 use IO::AIO;
91 72
92 # register the IO::AIO callback with Event 73 # register the IO::AIO callback with EV
93 Event->io (fd => IO::AIO::poll_fileno, 74 my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
94 poll => 'r',
95 cb => \&IO::AIO::poll_cb);
96 75
97 # queue the request to open /etc/passwd 76 # queue the request to open /etc/passwd
98 aio_open "/etc/passwd", O_RDONLY, 0, sub { 77 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
99 my $fh = $_[0] 78 my $fh = shift
100 or die "error while opening: $!"; 79 or die "error while opening: $!";
101 80
102 # stat'ing filehandles is generally non-blocking 81 # stat'ing filehandles is generally non-blocking
103 my $size = -s $fh; 82 my $size = -s $fh;
104 83
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112 91
113 # file contents now in $contents 92 # file contents now in $contents
114 print $contents; 93 print $contents;
115 94
116 # exit event loop and program 95 # exit event loop and program
117 Event::unloop; 96 EV::unloop;
118 }; 97 };
119 }; 98 };
120 99
121 # possibly queue up other requests, or open GUI windows, 100 # possibly queue up other requests, or open GUI windows,
122 # check for sockets etc. etc. 101 # check for sockets etc. etc.
123 102
124 # process events as long as there are some: 103 # process events as long as there are some:
125 Event::loop; 104 EV::loop;
126 105
127REQUEST ANATOMY AND LIFETIME 106REQUEST ANATOMY AND LIFETIME
128 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
129 not directly visible to Perl. 108 not directly visible to Perl.
130 109
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166 anymore (except possibly for the Perl object, but its connection to 145 anymore (except possibly for the Perl object, but its connection to
167 the actual aio request is severed and calling its methods will 146 the actual aio request is severed and calling its methods will
168 either do nothing or result in a runtime error). 147 either do nothing or result in a runtime error).
169 148
170FUNCTIONS 149FUNCTIONS
150 QUICK OVERVIEW
151 This section simply lists the prototypes of the most important functions
152 for quick reference. See the following sections for function-by-function
153 documentation.
154
155 aio_open $pathname, $flags, $mode, $callback->($fh)
156 aio_close $fh, $callback->($status)
157 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
158 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
159 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
160 aio_readahead $fh,$offset,$length, $callback->($retval)
161 aio_stat $fh_or_path, $callback->($status)
162 aio_lstat $fh, $callback->($status)
163 aio_statvfs $fh_or_path, $callback->($statvfs)
164 aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
165 aio_chown $fh_or_path, $uid, $gid, $callback->($status)
166 aio_truncate $fh_or_path, $offset, $callback->($status)
167 aio_chmod $fh_or_path, $mode, $callback->($status)
168 aio_unlink $pathname, $callback->($status)
169 aio_mknod $path, $mode, $dev, $callback->($status)
170 aio_link $srcpath, $dstpath, $callback->($status)
171 aio_symlink $srcpath, $dstpath, $callback->($status)
172 aio_readlink $path, $callback->($link)
173 aio_rename $srcpath, $dstpath, $callback->($status)
174 aio_mkdir $pathname, $mode, $callback->($status)
175 aio_rmdir $pathname, $callback->($status)
176 aio_readdir $pathname, $callback->($entries)
177 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
178 IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
179 IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
180 aio_load $path, $data, $callback->($status)
181 aio_copy $srcpath, $dstpath, $callback->($status)
182 aio_move $srcpath, $dstpath, $callback->($status)
183 aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
184 aio_rmtree $path, $callback->($status)
185 aio_sync $callback->($status)
186 aio_fsync $fh, $callback->($status)
187 aio_fdatasync $fh, $callback->($status)
188 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
189 aio_pathsync $path, $callback->($status)
190 aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
191 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
192 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
193 aio_mlockall $flags, $callback->($status)
194 aio_group $callback->(...)
195 aio_nop $callback->()
196
197 $prev_pri = aioreq_pri [$pri]
198 aioreq_nice $pri_adjust
199
200 IO::AIO::poll_wait
201 IO::AIO::poll_cb
202 IO::AIO::poll
203 IO::AIO::flush
204 IO::AIO::max_poll_reqs $nreqs
205 IO::AIO::max_poll_time $seconds
206 IO::AIO::min_parallel $nthreads
207 IO::AIO::max_parallel $nthreads
208 IO::AIO::max_idle $nthreads
209 IO::AIO::max_outstanding $maxreqs
210 IO::AIO::nreqs
211 IO::AIO::nready
212 IO::AIO::npending
213
214 IO::AIO::sendfile $ofh, $ifh, $offset, $count
215 IO::AIO::fadvise $fh, $offset, $len, $advice
216 IO::AIO::madvise $scalar, $offset, $length, $advice
217 IO::AIO::mprotect $scalar, $offset, $length, $protect
218 IO::AIO::munlock $scalar, $offset = 0, $length = undef
219 IO::AIO::munlockall
220
171 AIO REQUEST FUNCTIONS 221 AIO REQUEST FUNCTIONS
172 All the "aio_*" calls are more or less thin wrappers around the 222 All the "aio_*" calls are more or less thin wrappers around the syscall
173 syscall with the same name (sans "aio_"). The arguments are similar 223 with the same name (sans "aio_"). The arguments are similar or
174 or identical, and they all accept an additional (and optional) 224 identical, and they all accept an additional (and optional) $callback
175 $callback argument which must be a code reference. This code 225 argument which must be a code reference. This code reference will get
176 reference will get called with the syscall return code (e.g. most 226 called with the syscall return code (e.g. most syscalls return -1 on
177 syscalls return -1 on error, unlike perl, which usually delivers 227 error, unlike perl, which usually delivers "false") as its sole argument
178 "false") as it's sole argument when the given syscall has been 228 after the given syscall has been executed asynchronously.
179 executed asynchronously.
180 229
181 All functions expecting a filehandle keep a copy of the filehandle 230 All functions expecting a filehandle keep a copy of the filehandle
182 internally until the request has finished. 231 internally until the request has finished.
183 232
184 All functions return request objects of type IO::AIO::REQ that allow 233 All functions return request objects of type IO::AIO::REQ that allow
185 further manipulation of those requests while they are in-flight. 234 further manipulation of those requests while they are in-flight.
186 235
187 The pathnames you pass to these routines *must* be absolute and 236 The pathnames you pass to these routines *must* be absolute and encoded
188 encoded as octets. The reason for the former is that at the time the 237 as octets. The reason for the former is that at the time the request is
189 request is being executed, the current working directory could have 238 being executed, the current working directory could have changed.
190 changed. Alternatively, you can make sure that you never change the 239 Alternatively, you can make sure that you never change the current
191 current working directory anywhere in the program and then use 240 working directory anywhere in the program and then use relative paths.
192 relative paths.
193 241
194 To encode pathnames as octets, either make sure you either: a) 242 To encode pathnames as octets, either make sure you either: a) always
195 always pass in filenames you got from outside (command line, readdir 243 pass in filenames you got from outside (command line, readdir etc.)
196 etc.) without tinkering, b) are ASCII or ISO 8859-1, c) use the 244 without tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module
197 Encode module and encode your pathnames to the locale (or other) 245 and encode your pathnames to the locale (or other) encoding in effect in
198 encoding in effect in the user environment, d) use 246 the user environment, d) use Glib::filename_from_unicode on unicode
199 Glib::filename_from_unicode on unicode filenames or e) use something 247 filenames or e) use something else to ensure your scalar has the correct
200 else to ensure your scalar has the correct contents. 248 contents.
201 249
202 This works, btw. independent of the internal UTF-8 bit, which 250 This works, btw. independent of the internal UTF-8 bit, which IO::AIO
203 IO::AIO handles correctly wether it is set or not. 251 handles correctly whether it is set or not.
204 252
205 $prev_pri = aioreq_pri [$pri] 253 $prev_pri = aioreq_pri [$pri]
206 Returns the priority value that would be used for the next 254 Returns the priority value that would be used for the next request
207 request and, if $pri is given, sets the priority for the next 255 and, if $pri is given, sets the priority for the next aio request.
208 aio request.
209 256
210 The default priority is 0, the minimum and maximum priorities 257 The default priority is 0, the minimum and maximum priorities are -4
211 are -4 and 4, respectively. Requests with higher priority will 258 and 4, respectively. Requests with higher priority will be serviced
212 be serviced first. 259 first.
213 260
214 The priority will be reset to 0 after each call to one of the 261 The priority will be reset to 0 after each call to one of the
215 "aio_*" functions. 262 "aio_*" functions.
216 263
217 Example: open a file with low priority, then read something from 264 Example: open a file with low priority, then read something from it
218 it with higher priority so the read request is serviced before 265 with higher priority so the read request is serviced before other
219 other low priority open requests (potentially spamming the 266 low priority open requests (potentially spamming the cache):
220 cache):
221 267
268 aioreq_pri -3;
269 aio_open ..., sub {
270 return unless $_[0];
271
222 aioreq_pri -3; 272 aioreq_pri -2;
223 aio_open ..., sub {
224 return unless $_[0];
225
226 aioreq_pri -2;
227 aio_read $_[0], ..., sub { 273 aio_read $_[0], ..., sub {
228 ...
229 };
230 };
231
232 aioreq_nice $pri_adjust
233 Similar to "aioreq_pri", but subtracts the given value from the
234 current priority, so the effect is cumulative.
235
236 aio_open $pathname, $flags, $mode, $callback->($fh)
237 Asynchronously open or create a file and call the callback with
238 a newly created filehandle for the file.
239
240 The pathname passed to "aio_open" must be absolute. See API
241 NOTES, above, for an explanation.
242
243 The $flags argument is a bitmask. See the "Fcntl" module for a
244 list. They are the same as used by "sysopen".
245
246 Likewise, $mode specifies the mode of the newly created file, if
247 it didn't exist and "O_CREAT" has been given, just like perl's
248 "sysopen", except that it is mandatory (i.e. use 0 if you don't
249 create new files, and 0666 or 0777 if you do).
250
251 Example:
252
253 aio_open "/etc/passwd", O_RDONLY, 0, sub {
254 if ($_[0]) {
255 print "open successful, fh is $_[0]\n";
256 ...
257 } else {
258 die "open failed: $!\n";
259 }
260 };
261
262 aio_close $fh, $callback->($status)
263 Asynchronously close a file and call the callback with the
264 result code. *WARNING:* although accepted, you should not pass
265 in a perl filehandle here, as perl will likely close the file
266 descriptor another time when the filehandle is destroyed.
267 Normally, you can safely call perls "close" or just let
268 filehandles go out of scope.
269
270 This is supposed to be a bug in the API, so that might change.
271 It's therefore best to avoid this function.
272
273 aio_read $fh,$offset,$length, $data,$dataoffset,
274 $callback->($retval)
275 aio_write $fh,$offset,$length, $data,$dataoffset,
276 $callback->($retval)
277 Reads or writes "length" bytes from the specified "fh" and
278 "offset" into the scalar given by "data" and offset "dataoffset"
279 and calls the callback without the actual number of bytes read
280 (or -1 on error, just like the syscall).
281
282 The $data scalar *MUST NOT* be modified in any way while the
283 request is outstanding. Modifying it can result in segfaults or
284 WW3 (if the necessary/optional hardware is installed).
285
286 Example: Read 15 bytes at offset 7 into scalar $buffer, starting
287 at offset 0 within the scalar:
288
289 aio_read $fh, 7, 15, $buffer, 0, sub {
290 $_[0] > 0 or die "read error: $!";
291 print "read $_[0] bytes: <$buffer>\n";
292 };
293
294 aio_sendfile $out_fh, $in_fh, $in_offset, $length,
295 $callback->($retval)
296 Tries to copy $length bytes from $in_fh to $out_fh. It starts
297 reading at byte offset $in_offset, and starts writing at the
298 current file offset of $out_fh. Because of that, it is not safe
299 to issue more than one "aio_sendfile" per $out_fh, as they will
300 interfere with each other.
301
302 This call tries to make use of a native "sendfile" syscall to
303 provide zero-copy operation. For this to work, $out_fh should
304 refer to a socket, and $in_fh should refer to mmap'able file.
305
306 If the native sendfile call fails or is not implemented, it will
307 be emulated, so you can call "aio_sendfile" on any type of
308 filehandle regardless of the limitations of the operating
309 system.
310
311 Please note, however, that "aio_sendfile" can read more bytes
312 from $in_fh than are written, and there is no way to find out
313 how many bytes have been read from "aio_sendfile" alone, as
314 "aio_sendfile" only provides the number of bytes written to
315 $out_fh. Only if the result value equals $length one can assume
316 that $length bytes have been read.
317
318 aio_readahead $fh,$offset,$length, $callback->($retval)
319 "aio_readahead" populates the page cache with data from a file
320 so that subsequent reads from that file will not block on disk
321 I/O. The $offset argument specifies the starting point from
322 which data is to be read and $length specifies the number of
323 bytes to be read. I/O is performed in whole pages, so that
324 offset is effectively rounded down to a page boundary and bytes
325 are read up to the next page boundary greater than or equal to
326 (off-set+length). "aio_readahead" does not read beyond the end
327 of the file. The current file offset of the file is left
328 unchanged.
329
330 If that syscall doesn't exist (likely if your OS isn't Linux) it
331 will be emulated by simply reading the data, which would have a
332 similar effect.
333
334 aio_stat $fh_or_path, $callback->($status)
335 aio_lstat $fh, $callback->($status)
336 Works like perl's "stat" or "lstat" in void context. The
337 callback will be called after the stat and the results will be
338 available using "stat _" or "-s _" etc...
339
340 The pathname passed to "aio_stat" must be absolute. See API
341 NOTES, above, for an explanation.
342
343 Currently, the stats are always 64-bit-stats, i.e. instead of
344 returning an error when stat'ing a large file, the results will
345 be silently truncated unless perl itself is compiled with large
346 file support.
347
348 Example: Print the length of /etc/passwd:
349
350 aio_stat "/etc/passwd", sub {
351 $_[0] and die "stat failed: $!";
352 print "size is ", -s _, "\n";
353 };
354
355 aio_unlink $pathname, $callback->($status)
356 Asynchronously unlink (delete) a file and call the callback with
357 the result code.
358
359 aio_mknod $path, $mode, $dev, $callback->($status)
360 [EXPERIMENTAL]
361
362 Asynchronously create a device node (or fifo). See mknod(2).
363
364 The only (POSIX-) portable way of calling this function is:
365
366 aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...
367
368 aio_link $srcpath, $dstpath, $callback->($status)
369 Asynchronously create a new link to the existing object at
370 $srcpath at the path $dstpath and call the callback with the
371 result code.
372
373 aio_symlink $srcpath, $dstpath, $callback->($status)
374 Asynchronously create a new symbolic link to the existing object
375 at $srcpath at the path $dstpath and call the callback with the
376 result code.
377
378 aio_rename $srcpath, $dstpath, $callback->($status)
379 Asynchronously rename the object at $srcpath to $dstpath, just
380 as rename(2) and call the callback with the result code.
381
382 aio_rmdir $pathname, $callback->($status)
383 Asynchronously rmdir (delete) a directory and call the callback
384 with the result code.
385
386 aio_readdir $pathname, $callback->($entries)
387 Unlike the POSIX call of the same name, "aio_readdir" reads an
388 entire directory (i.e. opendir + readdir + closedir). The
389 entries will not be sorted, and will NOT include the "." and
390 ".." entries.
391
392 The callback a single argument which is either "undef" or an
393 array-ref with the filenames.
394
395 aio_copy $srcpath, $dstpath, $callback->($status)
396 Try to copy the *file* (directories not supported as either
397 source or destination) from $srcpath to $dstpath and call the
398 callback with the 0 (error) or -1 ok.
399
400 This is a composite request that it creates the destination file
401 with mode 0200 and copies the contents of the source file into
402 it using "aio_sendfile", followed by restoring atime, mtime,
403 access mode and uid/gid, in that order.
404
405 If an error occurs, the partial destination file will be
406 unlinked, if possible, except when setting atime, mtime, access
407 mode and uid/gid, where errors are being ignored.
408
409 aio_move $srcpath, $dstpath, $callback->($status)
410 Try to move the *file* (directories not supported as either
411 source or destination) from $srcpath to $dstpath and call the
412 callback with the 0 (error) or -1 ok.
413
414 This is a composite request that tries to rename(2) the file
415 first. If rename files with "EXDEV", it copies the file with
416 "aio_copy" and, if that is successful, unlinking the $srcpath.
417
418 aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
419 Scans a directory (similar to "aio_readdir") but additionally
420 tries to efficiently separate the entries of directory $path
421 into two sets of names, directories you can recurse into
422 (directories), and ones you cannot recurse into (everything
423 else, including symlinks to directories).
424
425 "aio_scandir" is a composite request that creates of many sub
426 requests_ $maxreq specifies the maximum number of outstanding
427 aio requests that this function generates. If it is "<= 0", then
428 a suitable default will be chosen (currently 4).
429
430 On error, the callback is called without arguments, otherwise it
431 receives two array-refs with path-relative entry names.
432
433 Example:
434
435 aio_scandir $dir, 0, sub {
436 my ($dirs, $nondirs) = @_;
437 print "real directories: @$dirs\n";
438 print "everything else: @$nondirs\n";
439 };
440
441 Implementation notes.
442
443 The "aio_readdir" cannot be avoided, but "stat()"'ing every
444 entry can.
445
446 After reading the directory, the modification time, size etc. of
447 the directory before and after the readdir is checked, and if
448 they match (and isn't the current time), the link count will be
449 used to decide how many entries are directories (if >= 2).
450 Otherwise, no knowledge of the number of subdirectories will be
451 assumed.
452
453 Then entries will be sorted into likely directories (everything
454 without a non-initial dot currently) and likely non-directories
455 (everything else). Then every entry plus an appended "/." will
456 be "stat"'ed, likely directories first. If that succeeds, it
457 assumes that the entry is a directory or a symlink to directory
458 (which will be checked seperately). This is often faster than
459 stat'ing the entry itself because filesystems might detect the
460 type of the entry without reading the inode data (e.g. ext2fs
461 filetype feature).
462
463 If the known number of directories (link count - 2) has been
464 reached, the rest of the entries is assumed to be
465 non-directories.
466
467 This only works with certainty on POSIX (= UNIX) filesystems,
468 which fortunately are the vast majority of filesystems around.
469
470 It will also likely work on non-POSIX filesystems with reduced
471 efficiency as those tend to return 0 or 1 as link counts, which
472 disables the directory counting heuristic.
473
474 aio_fsync $fh, $callback->($status)
475 Asynchronously call fsync on the given filehandle and call the
476 callback with the fsync result code.
477
478 aio_fdatasync $fh, $callback->($status)
479 Asynchronously call fdatasync on the given filehandle and call
480 the callback with the fdatasync result code.
481
482 If this call isn't available because your OS lacks it or it
483 couldn't be detected, it will be emulated by calling "fsync"
484 instead.
485
486 aio_group $callback->(...)
487 This is a very special aio request: Instead of doing something,
488 it is a container for other aio requests, which is useful if you
489 want to bundle many requests into a single, composite, request
490 with a definite callback and the ability to cancel the whole
491 request with its subrequests.
492
493 Returns an object of class IO::AIO::GRP. See its documentation
494 below for more info.
495
496 Example:
497
498 my $grp = aio_group sub {
499 print "all stats done\n";
500 };
501
502 add $grp
503 (aio_stat ...),
504 (aio_stat ...),
505 ...; 274 ...
506
507 aio_nop $callback->()
508 This is a special request - it does nothing in itself and is
509 only used for side effects, such as when you want to add a dummy
510 request to a group so that finishing the requests in the group
511 depends on executing the given code.
512
513 While this request does nothing, it still goes through the
514 execution phase and still requires a worker thread. Thus, the
515 callback will not be executed immediately but only after other
516 requests in the queue have entered their execution phase. This
517 can be used to measure request latency.
518
519 IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
520 Mainly used for debugging and benchmarking, this aio request
521 puts one of the request workers to sleep for the given time.
522
523 While it is theoretically handy to have simple I/O scheduling
524 requests like sleep and file handle readable/writable, the
525 overhead this creates is immense (it blocks a thread for a long
526 time) so do not use this function except to put your application
527 under artificial I/O pressure.
528
529 IO::AIO::REQ CLASS
530 All non-aggregate "aio_*" functions return an object of this class
531 when called in non-void context.
532
533 cancel $req
534 Cancels the request, if possible. Has the effect of skipping
535 execution when entering the execute state and skipping calling
536 the callback when entering the the result state, but will leave
537 the request otherwise untouched. That means that requests that
538 currently execute will not be stopped and resources held by the
539 request will not be freed prematurely.
540
541 cb $req $callback->(...)
542 Replace (or simply set) the callback registered to the request.
543
544 IO::AIO::GRP CLASS
545 This class is a subclass of IO::AIO::REQ, so all its methods apply
546 to objects of this class, too.
547
548 A IO::AIO::GRP object is a special request that can contain multiple
549 other aio requests.
550
551 You create one by calling the "aio_group" constructing function with
552 a callback that will be called when all contained requests have
553 entered the "done" state:
554
555 my $grp = aio_group sub {
556 print "all requests are done\n";
557 };
558
559 You add requests by calling the "add" method with one or more
560 "IO::AIO::REQ" objects:
561
562 $grp->add (aio_unlink "...");
563
564 add $grp aio_stat "...", sub {
565 $_[0] or return $grp->result ("error");
566
567 # add another request dynamically, if first succeeded
568 add $grp aio_open "...", sub {
569 $grp->result ("ok");
570 }; 275 };
571 }; 276 };
572 277
278 aioreq_nice $pri_adjust
279 Similar to "aioreq_pri", but subtracts the given value from the
280 current priority, so the effect is cumulative.
281
282 aio_open $pathname, $flags, $mode, $callback->($fh)
283 Asynchronously open or create a file and call the callback with a
284 newly created filehandle for the file.
285
286 The pathname passed to "aio_open" must be absolute. See API NOTES,
287 above, for an explanation.
288
289 The $flags argument is a bitmask. See the "Fcntl" module for a list.
290 They are the same as used by "sysopen".
291
292 Likewise, $mode specifies the mode of the newly created file, if it
293 didn't exist and "O_CREAT" has been given, just like perl's
294 "sysopen", except that it is mandatory (i.e. use 0 if you don't
295 create new files, and 0666 or 0777 if you do). Note that the $mode
296 will be modified by the umask in effect then the request is being
297 executed, so better never change the umask.
298
299 Example:
300
301 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
302 if ($_[0]) {
303 print "open successful, fh is $_[0]\n";
304 ...
305 } else {
306 die "open failed: $!\n";
307 }
308 };
309
310 aio_close $fh, $callback->($status)
311 Asynchronously close a file and call the callback with the result
312 code.
313
314 Unfortunately, you can't do this to perl. Perl *insists* very
315 strongly on closing the file descriptor associated with the
316 filehandle itself.
317
318 Therefore, "aio_close" will not close the filehandle - instead it
319 will use dup2 to overwrite the file descriptor with the write-end of
320 a pipe (the pipe fd will be created on demand and will be cached).
321
322 Or in other words: the file descriptor will be closed, but it will
323 not be free for reuse until the perl filehandle is closed.
324
325 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
326 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
327 Reads or writes $length bytes from or to the specified $fh and
328 $offset into the scalar given by $data and offset $dataoffset and
329 calls the callback without the actual number of bytes read (or -1 on
330 error, just like the syscall).
331
332 "aio_read" will, like "sysread", shrink or grow the $data scalar to
333 offset plus the actual number of bytes read.
334
335 If $offset is undefined, then the current file descriptor offset
336 will be used (and updated), otherwise the file descriptor offset
337 will not be changed by these calls.
338
339 If $length is undefined in "aio_write", use the remaining length of
340 $data.
341
342 If $dataoffset is less than zero, it will be counted from the end of
343 $data.
344
345 The $data scalar *MUST NOT* be modified in any way while the request
346 is outstanding. Modifying it can result in segfaults or World War
347 III (if the necessary/optional hardware is installed).
348
349 Example: Read 15 bytes at offset 7 into scalar $buffer, starting at
350 offset 0 within the scalar:
351
352 aio_read $fh, 7, 15, $buffer, 0, sub {
353 $_[0] > 0 or die "read error: $!";
354 print "read $_[0] bytes: <$buffer>\n";
355 };
356
357 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
358 Tries to copy $length bytes from $in_fh to $out_fh. It starts
359 reading at byte offset $in_offset, and starts writing at the current
360 file offset of $out_fh. Because of that, it is not safe to issue
361 more than one "aio_sendfile" per $out_fh, as they will interfere
362 with each other.
363
364 This call tries to make use of a native "sendfile" syscall to
365 provide zero-copy operation. For this to work, $out_fh should refer
366 to a socket, and $in_fh should refer to an mmap'able file.
367
368 If a native sendfile cannot be found or it fails with "ENOSYS",
369 "ENOTSUP", "EOPNOTSUPP", "EAFNOSUPPORT", "EPROTOTYPE" or "ENOTSOCK",
370 it will be emulated, so you can call "aio_sendfile" on any type of
371 filehandle regardless of the limitations of the operating system.
372
373 Please note, however, that "aio_sendfile" can read more bytes from
374 $in_fh than are written, and there is no way to find out how many
375 bytes have been read from "aio_sendfile" alone, as "aio_sendfile"
376 only provides the number of bytes written to $out_fh. Only if the
377 result value equals $length one can assume that $length bytes have
378 been read.
379
380 aio_readahead $fh,$offset,$length, $callback->($retval)
381 "aio_readahead" populates the page cache with data from a file so
382 that subsequent reads from that file will not block on disk I/O. The
383 $offset argument specifies the starting point from which data is to
384 be read and $length specifies the number of bytes to be read. I/O is
385 performed in whole pages, so that offset is effectively rounded down
386 to a page boundary and bytes are read up to the next page boundary
387 greater than or equal to (off-set+length). "aio_readahead" does not
388 read beyond the end of the file. The current file offset of the file
389 is left unchanged.
390
391 If that syscall doesn't exist (likely if your OS isn't Linux) it
392 will be emulated by simply reading the data, which would have a
393 similar effect.
394
395 aio_stat $fh_or_path, $callback->($status)
396 aio_lstat $fh, $callback->($status)
397 Works like perl's "stat" or "lstat" in void context. The callback
398 will be called after the stat and the results will be available
399 using "stat _" or "-s _" etc...
400
401 The pathname passed to "aio_stat" must be absolute. See API NOTES,
402 above, for an explanation.
403
404 Currently, the stats are always 64-bit-stats, i.e. instead of
405 returning an error when stat'ing a large file, the results will be
406 silently truncated unless perl itself is compiled with large file
407 support.
408
409 Example: Print the length of /etc/passwd:
410
411 aio_stat "/etc/passwd", sub {
412 $_[0] and die "stat failed: $!";
413 print "size is ", -s _, "\n";
414 };
415
416 aio_statvfs $fh_or_path, $callback->($statvfs)
417 Works like the POSIX "statvfs" or "fstatvfs" syscalls, depending on
418 whether a file handle or path was passed.
419
420 On success, the callback is passed a hash reference with the
421 following members: "bsize", "frsize", "blocks", "bfree", "bavail",
422 "files", "ffree", "favail", "fsid", "flag" and "namemax". On
423 failure, "undef" is passed.
424
425 The following POSIX IO::AIO::ST_* constants are defined: "ST_RDONLY"
426 and "ST_NOSUID".
427
428 The following non-POSIX IO::AIO::ST_* flag masks are defined to
429 their correct value when available, or to 0 on systems that do not
430 support them: "ST_NODEV", "ST_NOEXEC", "ST_SYNCHRONOUS",
431 "ST_MANDLOCK", "ST_WRITE", "ST_APPEND", "ST_IMMUTABLE",
432 "ST_NOATIME", "ST_NODIRATIME" and "ST_RELATIME".
433
434 Example: stat "/wd" and dump out the data if successful.
435
436 aio_statvfs "/wd", sub {
437 my $f = $_[0]
438 or die "statvfs: $!";
439
440 use Data::Dumper;
441 say Dumper $f;
442 };
443
444 # result:
445 {
446 bsize => 1024,
447 bfree => 4333064312,
448 blocks => 10253828096,
449 files => 2050765568,
450 flag => 4096,
451 favail => 2042092649,
452 bavail => 4333064312,
453 ffree => 2042092649,
454 namemax => 255,
455 frsize => 1024,
456 fsid => 1810
457 }
458
459 aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
460 Works like perl's "utime" function (including the special case of
461 $atime and $mtime being undef). Fractional times are supported if
462 the underlying syscalls support them.
463
464 When called with a pathname, uses utimes(2) if available, otherwise
465 utime(2). If called on a file descriptor, uses futimes(2) if
466 available, otherwise returns ENOSYS, so this is not portable.
467
468 Examples:
469
470 # set atime and mtime to current time (basically touch(1)):
471 aio_utime "path", undef, undef;
472 # set atime to current time and mtime to beginning of the epoch:
473 aio_utime "path", time, undef; # undef==0
474
475 aio_chown $fh_or_path, $uid, $gid, $callback->($status)
476 Works like perl's "chown" function, except that "undef" for either
477 $uid or $gid is being interpreted as "do not change" (but -1 can
478 also be used).
479
480 Examples:
481
482 # same as "chown root path" in the shell:
483 aio_chown "path", 0, -1;
484 # same as above:
485 aio_chown "path", 0, undef;
486
487 aio_truncate $fh_or_path, $offset, $callback->($status)
488 Works like truncate(2) or ftruncate(2).
489
490 aio_chmod $fh_or_path, $mode, $callback->($status)
491 Works like perl's "chmod" function.
492
493 aio_unlink $pathname, $callback->($status)
494 Asynchronously unlink (delete) a file and call the callback with the
495 result code.
496
497 aio_mknod $path, $mode, $dev, $callback->($status)
498 [EXPERIMENTAL]
499
500 Asynchronously create a device node (or fifo). See mknod(2).
501
502 The only (POSIX-) portable way of calling this function is:
503
504 aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...
505
506 aio_link $srcpath, $dstpath, $callback->($status)
507 Asynchronously create a new link to the existing object at $srcpath
508 at the path $dstpath and call the callback with the result code.
509
510 aio_symlink $srcpath, $dstpath, $callback->($status)
511 Asynchronously create a new symbolic link to the existing object at
512 $srcpath at the path $dstpath and call the callback with the result
513 code.
514
515 aio_readlink $path, $callback->($link)
516 Asynchronously read the symlink specified by $path and pass it to
517 the callback. If an error occurs, nothing or undef gets passed to
518 the callback.
519
520 aio_rename $srcpath, $dstpath, $callback->($status)
521 Asynchronously rename the object at $srcpath to $dstpath, just as
522 rename(2) and call the callback with the result code.
523
524 aio_mkdir $pathname, $mode, $callback->($status)
525 Asynchronously mkdir (create) a directory and call the callback with
526 the result code. $mode will be modified by the umask at the time the
527 request is executed, so do not change your umask.
528
529 aio_rmdir $pathname, $callback->($status)
530 Asynchronously rmdir (delete) a directory and call the callback with
531 the result code.
532
533 aio_readdir $pathname, $callback->($entries)
534 Unlike the POSIX call of the same name, "aio_readdir" reads an
535 entire directory (i.e. opendir + readdir + closedir). The entries
536 will not be sorted, and will NOT include the "." and ".." entries.
537
538 The callback is passed a single argument which is either "undef" or
539 an array-ref with the filenames.
540
541 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
542 Quite similar to "aio_readdir", but the $flags argument allows to
543 tune behaviour and output format. In case of an error, $entries will
544 be "undef".
545
546 The flags are a combination of the following constants, ORed
547 together (the flags will also be passed to the callback, possibly
548 modified):
549
550 IO::AIO::READDIR_DENTS
551 When this flag is off, then the callback gets an arrayref with
552 of names only (as with "aio_readdir"), otherwise it gets an
553 arrayref with "[$name, $type, $inode]" arrayrefs, each
554 describing a single directory entry in more detail.
555
556 $name is the name of the entry.
557
558 $type is one of the "IO::AIO::DT_xxx" constants:
559
560 "IO::AIO::DT_UNKNOWN", "IO::AIO::DT_FIFO", "IO::AIO::DT_CHR",
561 "IO::AIO::DT_DIR", "IO::AIO::DT_BLK", "IO::AIO::DT_REG",
562 "IO::AIO::DT_LNK", "IO::AIO::DT_SOCK", "IO::AIO::DT_WHT".
563
564 "IO::AIO::DT_UNKNOWN" means just that: readdir does not know. If
565 you need to know, you have to run stat yourself. Also, for speed
566 reasons, the $type scalars are read-only: you can not modify
567 them.
568
569 $inode is the inode number (which might not be exact on systems
570 with 64 bit inode numbers and 32 bit perls). This field has
571 unspecified content on systems that do not deliver the inode
572 information.
573
574 IO::AIO::READDIR_DIRS_FIRST
575 When this flag is set, then the names will be returned in an
576 order where likely directories come first. This is useful when
577 you need to quickly find directories, or you want to find all
578 directories while avoiding to stat() each entry.
579
580 If the system returns type information in readdir, then this is
581 used to find directories directly. Otherwise, likely directories
582 are files beginning with ".", or otherwise files with no dots,
583 of which files with short names are tried first.
584
585 IO::AIO::READDIR_STAT_ORDER
586 When this flag is set, then the names will be returned in an
587 order suitable for stat()'ing each one. That is, when you plan
588 to stat() all files in the given directory, then the returned
589 order will likely be fastest.
590
591 If both this flag and "IO::AIO::READDIR_DIRS_FIRST" are
592 specified, then the likely dirs come first, resulting in a less
593 optimal stat order.
594
595 IO::AIO::READDIR_FOUND_UNKNOWN
596 This flag should not be set when calling "aio_readdirx".
597 Instead, it is being set by "aio_readdirx", when any of the
598 $type's found were "IO::AIO::DT_UNKNOWN". The absense of this
599 flag therefore indicates that all $type's are known, which can
600 be used to speed up some algorithms.
601
602 aio_load $path, $data, $callback->($status)
603 This is a composite request that tries to fully load the given file
604 into memory. Status is the same as with aio_read.
605
606 aio_copy $srcpath, $dstpath, $callback->($status)
607 Try to copy the *file* (directories not supported as either source
608 or destination) from $srcpath to $dstpath and call the callback with
609 a status of 0 (ok) or -1 (error, see $!).
610
611 This is a composite request that creates the destination file with
612 mode 0200 and copies the contents of the source file into it using
613 "aio_sendfile", followed by restoring atime, mtime, access mode and
614 uid/gid, in that order.
615
616 If an error occurs, the partial destination file will be unlinked,
617 if possible, except when setting atime, mtime, access mode and
618 uid/gid, where errors are being ignored.
619
620 aio_move $srcpath, $dstpath, $callback->($status)
621 Try to move the *file* (directories not supported as either source
622 or destination) from $srcpath to $dstpath and call the callback with
623 a status of 0 (ok) or -1 (error, see $!).
624
625 This is a composite request that tries to rename(2) the file first;
626 if rename fails with "EXDEV", it copies the file with "aio_copy"
627 and, if that is successful, unlinks the $srcpath.
628
629 aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
630 Scans a directory (similar to "aio_readdir") but additionally tries
631 to efficiently separate the entries of directory $path into two sets
632 of names, directories you can recurse into (directories), and ones
633 you cannot recurse into (everything else, including symlinks to
634 directories).
635
636 "aio_scandir" is a composite request that creates of many sub
637 requests_ $maxreq specifies the maximum number of outstanding aio
638 requests that this function generates. If it is "<= 0", then a
639 suitable default will be chosen (currently 4).
640
641 On error, the callback is called without arguments, otherwise it
642 receives two array-refs with path-relative entry names.
643
644 Example:
645
646 aio_scandir $dir, 0, sub {
647 my ($dirs, $nondirs) = @_;
648 print "real directories: @$dirs\n";
649 print "everything else: @$nondirs\n";
650 };
651
652 Implementation notes.
653
654 The "aio_readdir" cannot be avoided, but "stat()"'ing every entry
655 can.
656
657 If readdir returns file type information, then this is used directly
658 to find directories.
659
660 Otherwise, after reading the directory, the modification time, size
661 etc. of the directory before and after the readdir is checked, and
662 if they match (and isn't the current time), the link count will be
663 used to decide how many entries are directories (if >= 2).
664 Otherwise, no knowledge of the number of subdirectories will be
665 assumed.
666
667 Then entries will be sorted into likely directories a non-initial
668 dot currently) and likely non-directories (see "aio_readdirx"). Then
669 every entry plus an appended "/." will be "stat"'ed, likely
670 directories first, in order of their inode numbers. If that
671 succeeds, it assumes that the entry is a directory or a symlink to
672 directory (which will be checked seperately). This is often faster
673 than stat'ing the entry itself because filesystems might detect the
674 type of the entry without reading the inode data (e.g. ext2fs
675 filetype feature), even on systems that cannot return the filetype
676 information on readdir.
677
678 If the known number of directories (link count - 2) has been
679 reached, the rest of the entries is assumed to be non-directories.
680
681 This only works with certainty on POSIX (= UNIX) filesystems, which
682 fortunately are the vast majority of filesystems around.
683
684 It will also likely work on non-POSIX filesystems with reduced
685 efficiency as those tend to return 0 or 1 as link counts, which
686 disables the directory counting heuristic.
687
688 aio_rmtree $path, $callback->($status)
689 Delete a directory tree starting (and including) $path, return the
690 status of the final "rmdir" only. This is a composite request that
691 uses "aio_scandir" to recurse into and rmdir directories, and unlink
692 everything else.
693
694 aio_sync $callback->($status)
695 Asynchronously call sync and call the callback when finished.
696
697 aio_fsync $fh, $callback->($status)
698 Asynchronously call fsync on the given filehandle and call the
699 callback with the fsync result code.
700
701 aio_fdatasync $fh, $callback->($status)
702 Asynchronously call fdatasync on the given filehandle and call the
703 callback with the fdatasync result code.
704
705 If this call isn't available because your OS lacks it or it couldn't
706 be detected, it will be emulated by calling "fsync" instead.
707
708 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
709 Sync the data portion of the file specified by $offset and $length
710 to disk (but NOT the metadata), by calling the Linux-specific
711 sync_file_range call. If sync_file_range is not available or it
712 returns ENOSYS, then fdatasync or fsync is being substituted.
713
714 $flags can be a combination of
715 "IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE",
716 "IO::AIO::SYNC_FILE_RANGE_WRITE" and
717 "IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER": refer to the sync_file_range
718 manpage for details.
719
720 aio_pathsync $path, $callback->($status)
721 This request tries to open, fsync and close the given path. This is
722 a composite request intended to sync directories after directory
723 operations (E.g. rename). This might not work on all operating
724 systems or have any specific effect, but usually it makes sure that
725 directory changes get written to disc. It works for anything that
726 can be opened for read-only, not just directories.
727
728 Future versions of this function might fall back to other methods
729 when "fsync" on the directory fails (such as calling "sync").
730
731 Passes 0 when everything went ok, and -1 on error.
732
733 aio_msync $scalar, $offset = 0, $length = undef, flags = 0,
734 $callback->($status)
735 This is a rather advanced IO::AIO call, which only works on
736 mmap(2)ed scalars (see the "IO::AIO::mmap" function, although it
737 also works on data scalars managed by the Sys::Mmap or Mmap modules,
738 note that the scalar must only be modified in-place while an aio
739 operation is pending on it).
740
741 It calls the "msync" function of your OS, if available, with the
742 memory area starting at $offset in the string and ending $length
743 bytes later. If $length is negative, counts from the end, and if
744 $length is "undef", then it goes till the end of the string. The
745 flags can be a combination of "IO::AIO::MS_ASYNC",
746 "IO::AIO::MS_INVALIDATE" and "IO::AIO::MS_SYNC".
747
748 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0,
749 $callback->($status)
750 This is a rather advanced IO::AIO call, which works best on
751 mmap(2)ed scalars.
752
753 It touches (reads or writes) all memory pages in the specified range
754 inside the scalar. All caveats and parameters are the same as for
755 "aio_msync", above, except for flags, which must be either 0 (which
756 reads all pages and ensures they are instantiated) or
757 "IO::AIO::MT_MODIFY", which modifies the memory page s(by reading
758 and writing an octet from it, which dirties the page).
759
760 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
761 This is a rather advanced IO::AIO call, which works best on
762 mmap(2)ed scalars.
763
764 It reads in all the pages of the underlying storage into memory (if
765 any) and locks them, so they are not getting swapped/paged out or
766 removed.
767
768 If $length is undefined, then the scalar will be locked till the
769 end.
770
771 On systems that do not implement "mlock", this function returns -1
772 and sets errno to "ENOSYS".
773
774 Note that the corresponding "munlock" is synchronous and is
775 documented under "MISCELLANEOUS FUNCTIONS".
776
777 Example: open a file, mmap and mlock it - both will be undone when
778 $data gets destroyed.
779
780 open my $fh, "<", $path or die "$path: $!";
781 my $data;
782 IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
783 aio_mlock $data; # mlock in background
784
785 aio_mlockall $flags, $callback->($status)
786 Calls the "mlockall" function with the given $flags (a combination
787 of "IO::AIO::MCL_CURRENT" and "IO::AIO::MCL_FUTURE").
788
789 On systems that do not implement "mlockall", this function returns
790 -1 and sets errno to "ENOSYS".
791
792 Note that the corresponding "munlockall" is synchronous and is
793 documented under "MISCELLANEOUS FUNCTIONS".
794
795 Example: asynchronously lock all current and future pages into
796 memory.
797
798 aio_mlockall IO::AIO::MCL_FUTURE;
799
800 aio_group $callback->(...)
801 This is a very special aio request: Instead of doing something, it
802 is a container for other aio requests, which is useful if you want
803 to bundle many requests into a single, composite, request with a
804 definite callback and the ability to cancel the whole request with
805 its subrequests.
806
807 Returns an object of class IO::AIO::GRP. See its documentation below
808 for more info.
809
810 Example:
811
812 my $grp = aio_group sub {
813 print "all stats done\n";
814 };
815
816 add $grp
817 (aio_stat ...),
818 (aio_stat ...),
819 ...;
820
821 aio_nop $callback->()
822 This is a special request - it does nothing in itself and is only
823 used for side effects, such as when you want to add a dummy request
824 to a group so that finishing the requests in the group depends on
825 executing the given code.
826
827 While this request does nothing, it still goes through the execution
828 phase and still requires a worker thread. Thus, the callback will
829 not be executed immediately but only after other requests in the
830 queue have entered their execution phase. This can be used to
831 measure request latency.
832
833 IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
834 Mainly used for debugging and benchmarking, this aio request puts
835 one of the request workers to sleep for the given time.
836
837 While it is theoretically handy to have simple I/O scheduling
838 requests like sleep and file handle readable/writable, the overhead
839 this creates is immense (it blocks a thread for a long time) so do
840 not use this function except to put your application under
841 artificial I/O pressure.
842
843 IO::AIO::REQ CLASS
844 All non-aggregate "aio_*" functions return an object of this class when
845 called in non-void context.
846
847 cancel $req
848 Cancels the request, if possible. Has the effect of skipping
849 execution when entering the execute state and skipping calling the
850 callback when entering the the result state, but will leave the
851 request otherwise untouched (with the exception of readdir). That
852 means that requests that currently execute will not be stopped and
853 resources held by the request will not be freed prematurely.
854
855 cb $req $callback->(...)
856 Replace (or simply set) the callback registered to the request.
857
858 IO::AIO::GRP CLASS
859 This class is a subclass of IO::AIO::REQ, so all its methods apply to
860 objects of this class, too.
861
862 A IO::AIO::GRP object is a special request that can contain multiple
863 other aio requests.
864
865 You create one by calling the "aio_group" constructing function with a
866 callback that will be called when all contained requests have entered
867 the "done" state:
868
869 my $grp = aio_group sub {
870 print "all requests are done\n";
871 };
872
873 You add requests by calling the "add" method with one or more
874 "IO::AIO::REQ" objects:
875
876 $grp->add (aio_unlink "...");
877
878 add $grp aio_stat "...", sub {
879 $_[0] or return $grp->result ("error");
880
881 # add another request dynamically, if first succeeded
882 add $grp aio_open "...", sub {
883 $grp->result ("ok");
884 };
885 };
886
573 This makes it very easy to create composite requests (see the source 887 This makes it very easy to create composite requests (see the source of
574 of "aio_move" for an application) that work and feel like simple 888 "aio_move" for an application) that work and feel like simple requests.
575 requests.
576 889
577 * The IO::AIO::GRP objects will be cleaned up during calls to 890 * The IO::AIO::GRP objects will be cleaned up during calls to
578 "IO::AIO::poll_cb", just like any other request. 891 "IO::AIO::poll_cb", just like any other request.
892
579 * They can be canceled like any other request. Canceling will cancel 893 * They can be canceled like any other request. Canceling will cancel
580 not only the request itself, but also all requests it contains. 894 not only the request itself, but also all requests it contains.
895
581 * They can also can also be added to other IO::AIO::GRP objects. 896 * They can also can also be added to other IO::AIO::GRP objects.
897
582 * You must not add requests to a group from within the group 898 * You must not add requests to a group from within the group callback
583 callback (or any later time). 899 (or any later time).
584 900
585 Their lifetime, simplified, looks like this: when they are empty, 901 Their lifetime, simplified, looks like this: when they are empty, they
586 they will finish very quickly. If they contain only requests that 902 will finish very quickly. If they contain only requests that are in the
587 are in the "done" state, they will also finish. Otherwise they will 903 "done" state, they will also finish. Otherwise they will continue to
588 continue to exist. 904 exist.
589 905
590 That means after creating a group you have some time to add 906 That means after creating a group you have some time to add requests
907 (precisely before the callback has been invoked, which is only done
591 requests. And in the callbacks of those requests, you can add 908 within the "poll_cb"). And in the callbacks of those requests, you can
592 further requests to the group. And only when all those requests have 909 add further requests to the group. And only when all those requests have
593 finished will the the group itself finish. 910 finished will the the group itself finish.
594 911
595 add $grp ... 912 add $grp ...
596 $grp->add (...) 913 $grp->add (...)
597 Add one or more requests to the group. Any type of IO::AIO::REQ 914 Add one or more requests to the group. Any type of IO::AIO::REQ can
598 can be added, including other groups, as long as you do not 915 be added, including other groups, as long as you do not create
599 create circular dependencies. 916 circular dependencies.
600 917
601 Returns all its arguments. 918 Returns all its arguments.
602 919
603 $grp->cancel_subs 920 $grp->cancel_subs
604 Cancel all subrequests and clears any feeder, but not the group 921 Cancel all subrequests and clears any feeder, but not the group
605 request itself. Useful when you queued a lot of events but got a 922 request itself. Useful when you queued a lot of events but got a
606 result early. 923 result early.
607 924
925 The group request will finish normally (you cannot add requests to
926 the group).
927
608 $grp->result (...) 928 $grp->result (...)
609 Set the result value(s) that will be passed to the group 929 Set the result value(s) that will be passed to the group callback
610 callback when all subrequests have finished and set thre groups 930 when all subrequests have finished and set the groups errno to the
611 errno to the current value of errno (just like calling "errno" 931 current value of errno (just like calling "errno" without an error
612 without an error number). By default, no argument will be passed 932 number). By default, no argument will be passed and errno is zero.
613 and errno is zero.
614 933
615 $grp->errno ([$errno]) 934 $grp->errno ([$errno])
616 Sets the group errno value to $errno, or the current value of 935 Sets the group errno value to $errno, or the current value of errno
617 errno when the argument is missing. 936 when the argument is missing.
618 937
619 Every aio request has an associated errno value that is restored 938 Every aio request has an associated errno value that is restored
620 when the callback is invoked. This method lets you change this 939 when the callback is invoked. This method lets you change this value
621 value from its default (0). 940 from its default (0).
622 941
623 Calling "result" will also set errno, so make sure you either 942 Calling "result" will also set errno, so make sure you either set $!
624 set $! before the call to "result", or call c<errno> after it. 943 before the call to "result", or call c<errno> after it.
625 944
626 feed $grp $callback->($grp) 945 feed $grp $callback->($grp)
627 Sets a feeder/generator on this group: every group can have an 946 Sets a feeder/generator on this group: every group can have an
628 attached generator that generates requests if idle. The idea 947 attached generator that generates requests if idle. The idea behind
629 behind this is that, although you could just queue as many 948 this is that, although you could just queue as many requests as you
630 requests as you want in a group, this might starve other 949 want in a group, this might starve other requests for a potentially
631 requests for a potentially long time. For example, "aio_scandir" 950 long time. For example, "aio_scandir" might generate hundreds of
632 might generate hundreds of thousands "aio_stat" requests, 951 thousands "aio_stat" requests, delaying any later requests for a
633 delaying any later requests for a long time. 952 long time.
634 953
635 To avoid this, and allow incremental generation of requests, you 954 To avoid this, and allow incremental generation of requests, you can
636 can instead a group and set a feeder on it that generates those 955 instead a group and set a feeder on it that generates those
637 requests. The feed callback will be called whenever there are 956 requests. The feed callback will be called whenever there are few
638 few enough (see "limit", below) requests active in the group 957 enough (see "limit", below) requests active in the group itself and
639 itself and is expected to queue more requests. 958 is expected to queue more requests.
640 959
641 The feed callback can queue as many requests as it likes (i.e. 960 The feed callback can queue as many requests as it likes (i.e. "add"
642 "add" does not impose any limits). 961 does not impose any limits).
643 962
644 If the feed does not queue more requests when called, it will be 963 If the feed does not queue more requests when called, it will be
645 automatically removed from the group. 964 automatically removed from the group.
646 965
647 If the feed limit is 0, it will be set to 2 automatically. 966 If the feed limit is 0 when this method is called, it will be set to
967 2 automatically.
648 968
649 Example: 969 Example:
650 970
651 # stat all files in @files, but only ever use four aio requests concurrently: 971 # stat all files in @files, but only ever use four aio requests concurrently:
652 972
653 my $grp = aio_group sub { print "finished\n" }; 973 my $grp = aio_group sub { print "finished\n" };
654 limit $grp 4; 974 limit $grp 4;
655 feed $grp sub { 975 feed $grp sub {
656 my $file = pop @files 976 my $file = pop @files
657 or return; 977 or return;
658 978
659 add $grp aio_stat $file, sub { ... }; 979 add $grp aio_stat $file, sub { ... };
660 }; 980 };
661 981
662 limit $grp $num 982 limit $grp $num
663 Sets the feeder limit for the group: The feeder will be called 983 Sets the feeder limit for the group: The feeder will be called
664 whenever the group contains less than this many requests. 984 whenever the group contains less than this many requests.
665 985
666 Setting the limit to 0 will pause the feeding process. 986 Setting the limit to 0 will pause the feeding process.
987
988 The default value for the limit is 0, but note that setting a feeder
989 automatically bumps it up to 2.
667 990
668 SUPPORT FUNCTIONS 991 SUPPORT FUNCTIONS
669 EVENT PROCESSING AND EVENT LOOP INTEGRATION 992 EVENT PROCESSING AND EVENT LOOP INTEGRATION
670 $fileno = IO::AIO::poll_fileno 993 $fileno = IO::AIO::poll_fileno
671 Return the *request result pipe file descriptor*. This 994 Return the *request result pipe file descriptor*. This filehandle
672 filehandle must be polled for reading by some mechanism outside 995 must be polled for reading by some mechanism outside this module
673 this module (e.g. Event or select, see below or the SYNOPSIS). 996 (e.g. EV, Glib, select and so on, see below or the SYNOPSIS). If the
674 If the pipe becomes readable you have to call "poll_cb" to check 997 pipe becomes readable you have to call "poll_cb" to check the
675 the results. 998 results.
676 999
677 See "poll_cb" for an example. 1000 See "poll_cb" for an example.
678 1001
679 IO::AIO::poll_cb 1002 IO::AIO::poll_cb
680 Process some outstanding events on the result pipe. You have to 1003 Process some outstanding events on the result pipe. You have to call
681 call this regularly. Returns the number of events processed. 1004 this regularly. Returns 0 if all events could be processed, or -1 if
682 Returns immediately when no events are outstanding. The amount 1005 it returned earlier for whatever reason. Returns immediately when no
683 of events processed depends on the settings of 1006 events are outstanding. The amount of events processed depends on
684 "IO::AIO::max_poll_req" and "IO::AIO::max_poll_time". 1007 the settings of "IO::AIO::max_poll_req" and
1008 "IO::AIO::max_poll_time".
685 1009
686 If not all requests were processed for whatever reason, the 1010 If not all requests were processed for whatever reason, the
687 filehandle will still be ready when "poll_cb" returns. 1011 filehandle will still be ready when "poll_cb" returns, so normally
1012 you don't have to do anything special to have it called later.
688 1013
689 Example: Install an Event watcher that automatically calls 1014 Example: Install an Event watcher that automatically calls
690 IO::AIO::poll_cb with high priority: 1015 IO::AIO::poll_cb with high priority (more examples can be found in
1016 the SYNOPSIS section, at the top of this document):
691 1017
692 Event->io (fd => IO::AIO::poll_fileno, 1018 Event->io (fd => IO::AIO::poll_fileno,
693 poll => 'r', async => 1, 1019 poll => 'r', async => 1,
694 cb => \&IO::AIO::poll_cb); 1020 cb => \&IO::AIO::poll_cb);
695 1021
696 IO::AIO::max_poll_reqs $nreqs
697 IO::AIO::max_poll_time $seconds
698 These set the maximum number of requests (default 0, meaning
699 infinity) that are being processed by "IO::AIO::poll_cb" in one
700 call, respectively the maximum amount of time (default 0,
701 meaning infinity) spent in "IO::AIO::poll_cb" to process
702 requests (more correctly the mininum amount of time "poll_cb" is
703 allowed to use).
704
705 Setting these is useful if you want to ensure some level of
706 interactiveness when perl is not fast enough to process all
707 requests in time.
708
709 For interactive programs, values such as 0.01 to 0.1 should be
710 fine.
711
712 Example: Install an Event watcher that automatically calls
713 IO::AIO::poll_some with low priority, to ensure that other parts
714 of the program get the CPU sometimes even under high AIO load.
715
716 # try not to spend much more than 0.1s in poll_cb
717 IO::AIO::max_poll_time 0.1;
718
719 # use a low priority so other tasks have priority
720 Event->io (fd => IO::AIO::poll_fileno,
721 poll => 'r', nice => 1,
722 cb => &IO::AIO::poll_cb);
723
724 IO::AIO::poll_wait 1022 IO::AIO::poll_wait
1023 If there are any outstanding requests and none of them in the result
725 Wait till the result filehandle becomes ready for reading 1024 phase, wait till the result filehandle becomes ready for reading
726 (simply does a "select" on the filehandle. This is useful if you 1025 (simply does a "select" on the filehandle. This is useful if you
727 want to synchronously wait for some requests to finish). 1026 want to synchronously wait for some requests to finish).
728 1027
729 See "nreqs" for an example. 1028 See "nreqs" for an example.
730 1029
731 IO::AIO::poll 1030 IO::AIO::poll
732 Waits until some requests have been handled. 1031 Waits until some requests have been handled.
733 1032
1033 Returns the number of requests processed, but is otherwise strictly
734 Strictly equivalent to: 1034 equivalent to:
735 1035
736 IO::AIO::poll_wait, IO::AIO::poll_cb 1036 IO::AIO::poll_wait, IO::AIO::poll_cb
737 if IO::AIO::nreqs;
738 1037
739 IO::AIO::flush 1038 IO::AIO::flush
740 Wait till all outstanding AIO requests have been handled. 1039 Wait till all outstanding AIO requests have been handled.
741 1040
742 Strictly equivalent to: 1041 Strictly equivalent to:
743 1042
744 IO::AIO::poll_wait, IO::AIO::poll_cb 1043 IO::AIO::poll_wait, IO::AIO::poll_cb
745 while IO::AIO::nreqs; 1044 while IO::AIO::nreqs;
1045
1046 IO::AIO::max_poll_reqs $nreqs
1047 IO::AIO::max_poll_time $seconds
1048 These set the maximum number of requests (default 0, meaning
1049 infinity) that are being processed by "IO::AIO::poll_cb" in one
1050 call, respectively the maximum amount of time (default 0, meaning
1051 infinity) spent in "IO::AIO::poll_cb" to process requests (more
1052 correctly the mininum amount of time "poll_cb" is allowed to use).
1053
1054 Setting "max_poll_time" to a non-zero value creates an overhead of
1055 one syscall per request processed, which is not normally a problem
1056 unless your callbacks are really really fast or your OS is really
1057 really slow (I am not mentioning Solaris here). Using
1058 "max_poll_reqs" incurs no overhead.
1059
1060 Setting these is useful if you want to ensure some level of
1061 interactiveness when perl is not fast enough to process all requests
1062 in time.
1063
1064 For interactive programs, values such as 0.01 to 0.1 should be fine.
1065
1066 Example: Install an Event watcher that automatically calls
1067 IO::AIO::poll_cb with low priority, to ensure that other parts of
1068 the program get the CPU sometimes even under high AIO load.
1069
1070 # try not to spend much more than 0.1s in poll_cb
1071 IO::AIO::max_poll_time 0.1;
1072
1073 # use a low priority so other tasks have priority
1074 Event->io (fd => IO::AIO::poll_fileno,
1075 poll => 'r', nice => 1,
1076 cb => &IO::AIO::poll_cb);
746 1077
747 CONTROLLING THE NUMBER OF THREADS 1078 CONTROLLING THE NUMBER OF THREADS
748 IO::AIO::min_parallel $nthreads 1079 IO::AIO::min_parallel $nthreads
749 Set the minimum number of AIO threads to $nthreads. The current 1080 Set the minimum number of AIO threads to $nthreads. The current
750 default is 8, which means eight asynchronous operations can 1081 default is 8, which means eight asynchronous operations can execute
751 execute concurrently at any one time (the number of outstanding 1082 concurrently at any one time (the number of outstanding requests,
752 requests, however, is unlimited). 1083 however, is unlimited).
753 1084
754 IO::AIO starts threads only on demand, when an AIO request is 1085 IO::AIO starts threads only on demand, when an AIO request is queued
755 queued and no free thread exists. Please note that queueing up a 1086 and no free thread exists. Please note that queueing up a hundred
756 hundred requests can create demand for a hundred threads, even 1087 requests can create demand for a hundred threads, even if it turns
757 if it turns out that everything is in the cache and could have 1088 out that everything is in the cache and could have been processed
758 been processed faster by a single thread. 1089 faster by a single thread.
759 1090
760 It is recommended to keep the number of threads relatively low, 1091 It is recommended to keep the number of threads relatively low, as
761 as some Linux kernel versions will scale negatively with the 1092 some Linux kernel versions will scale negatively with the number of
762 number of threads (higher parallelity => MUCH higher latency). 1093 threads (higher parallelity => MUCH higher latency). With current
763 With current Linux 2.6 versions, 4-32 threads should be fine. 1094 Linux 2.6 versions, 4-32 threads should be fine.
764 1095
765 Under most circumstances you don't need to call this function, 1096 Under most circumstances you don't need to call this function, as
766 as the module selects a default that is suitable for low to 1097 the module selects a default that is suitable for low to moderate
767 moderate load. 1098 load.
768 1099
769 IO::AIO::max_parallel $nthreads 1100 IO::AIO::max_parallel $nthreads
770 Sets the maximum number of AIO threads to $nthreads. If more 1101 Sets the maximum number of AIO threads to $nthreads. If more than
771 than the specified number of threads are currently running, this 1102 the specified number of threads are currently running, this function
772 function kills them. This function blocks until the limit is 1103 kills them. This function blocks until the limit is reached.
773 reached.
774 1104
775 While $nthreads are zero, aio requests get queued but not 1105 While $nthreads are zero, aio requests get queued but not executed
776 executed until the number of threads has been increased again. 1106 until the number of threads has been increased again.
777 1107
778 This module automatically runs "max_parallel 0" at program end, 1108 This module automatically runs "max_parallel 0" at program end, to
779 to ensure that all threads are killed and that there are no 1109 ensure that all threads are killed and that there are no outstanding
780 outstanding requests. 1110 requests.
781 1111
782 Under normal circumstances you don't need to call this function. 1112 Under normal circumstances you don't need to call this function.
783 1113
784 IO::AIO::max_idle $nthreads 1114 IO::AIO::max_idle $nthreads
785 Limit the number of threads (default: 4) that are allowed to 1115 Limit the number of threads (default: 4) that are allowed to idle
786 idle (i.e., threads that did not get a request to process within 1116 (i.e., threads that did not get a request to process within 10
787 10 seconds). That means if a thread becomes idle while $nthreads 1117 seconds). That means if a thread becomes idle while $nthreads other
788 other threads are also idle, it will free its resources and 1118 threads are also idle, it will free its resources and exit.
789 exit.
790 1119
791 This is useful when you allow a large number of threads (e.g. 1120 This is useful when you allow a large number of threads (e.g. 100 or
792 100 or 1000) to allow for extremely high load situations, but 1121 1000) to allow for extremely high load situations, but want to free
793 want to free resources under normal circumstances (1000 threads 1122 resources under normal circumstances (1000 threads can easily
794 can easily consume 30MB of RAM). 1123 consume 30MB of RAM).
795 1124
796 The default is probably ok in most situations, especially if 1125 The default is probably ok in most situations, especially if thread
797 thread creation is fast. If thread creation is very slow on your 1126 creation is fast. If thread creation is very slow on your system you
798 system you might want to use larger values. 1127 might want to use larger values.
799 1128
800 $oldmaxreqs = IO::AIO::max_outstanding $maxreqs 1129 IO::AIO::max_outstanding $maxreqs
801 This is a very bad function to use in interactive programs 1130 This is a very bad function to use in interactive programs because
802 because it blocks, and a bad way to reduce concurrency because 1131 it blocks, and a bad way to reduce concurrency because it is
803 it is inexact: Better use an "aio_group" together with a feed 1132 inexact: Better use an "aio_group" together with a feed callback.
804 callback.
805 1133
806 Sets the maximum number of outstanding requests to $nreqs. If 1134 Sets the maximum number of outstanding requests to $nreqs. If you do
807 you to queue up more than this number of requests, the next call 1135 queue up more than this number of requests, the next call to the
808 to the "poll_cb" (and "poll_some" and other functions calling 1136 "poll_cb" (and "poll_some" and other functions calling "poll_cb")
809 "poll_cb") function will block until the limit is no longer 1137 function will block until the limit is no longer exceeded.
810 exceeded.
811 1138
812 The default value is very large, so there is no practical limit 1139 The default value is very large, so there is no practical limit on
813 on the number of outstanding requests. 1140 the number of outstanding requests.
814 1141
815 You can still queue as many requests as you want. Therefore, 1142 You can still queue as many requests as you want. Therefore,
816 "max_oustsanding" is mainly useful in simple scripts (with low 1143 "max_outstanding" is mainly useful in simple scripts (with low
817 values) or as a stop gap to shield against fatal memory overflow 1144 values) or as a stop gap to shield against fatal memory overflow
818 (with large values). 1145 (with large values).
819 1146
820 STATISTICAL INFORMATION 1147 STATISTICAL INFORMATION
821 IO::AIO::nreqs 1148 IO::AIO::nreqs
822 Returns the number of requests currently in the ready, execute 1149 Returns the number of requests currently in the ready, execute or
823 or pending states (i.e. for which their callback has not been 1150 pending states (i.e. for which their callback has not been invoked
824 invoked yet). 1151 yet).
825 1152
826 Example: wait till there are no outstanding requests anymore: 1153 Example: wait till there are no outstanding requests anymore:
827 1154
828 IO::AIO::poll_wait, IO::AIO::poll_cb 1155 IO::AIO::poll_wait, IO::AIO::poll_cb
829 while IO::AIO::nreqs; 1156 while IO::AIO::nreqs;
830 1157
831 IO::AIO::nready 1158 IO::AIO::nready
832 Returns the number of requests currently in the ready state (not 1159 Returns the number of requests currently in the ready state (not yet
833 yet executed). 1160 executed).
834 1161
835 IO::AIO::npending 1162 IO::AIO::npending
836 Returns the number of requests currently in the pending state 1163 Returns the number of requests currently in the pending state
837 (executed, but not yet processed by poll_cb). 1164 (executed, but not yet processed by poll_cb).
1165
1166 MISCELLANEOUS FUNCTIONS
1167 IO::AIO implements some functions that might be useful, but are not
1168 asynchronous.
1169
1170 IO::AIO::sendfile $ofh, $ifh, $offset, $count
1171 Calls the "eio_sendfile_sync" function, which is like
1172 "aio_sendfile", but is blocking (this makes most sense if you know
1173 the input data is likely cached already and the output filehandle is
1174 set to non-blocking operations).
1175
1176 Returns the number of bytes copied, or -1 on error.
1177
1178 IO::AIO::fadvise $fh, $offset, $len, $advice
1179 Simply calls the "posix_fadvise" function (see its manpage for
1180 details). The following advice constants are avaiable:
1181 "IO::AIO::FADV_NORMAL", "IO::AIO::FADV_SEQUENTIAL",
1182 "IO::AIO::FADV_RANDOM", "IO::AIO::FADV_NOREUSE",
1183 "IO::AIO::FADV_WILLNEED", "IO::AIO::FADV_DONTNEED".
1184
1185 On systems that do not implement "posix_fadvise", this function
1186 returns ENOSYS, otherwise the return value of "posix_fadvise".
1187
1188 IO::AIO::madvise $scalar, $offset, $len, $advice
1189 Simply calls the "posix_madvise" function (see its manpage for
1190 details). The following advice constants are avaiable:
1191 "IO::AIO::MADV_NORMAL", "IO::AIO::MADV_SEQUENTIAL",
1192 "IO::AIO::MADV_RANDOM", "IO::AIO::MADV_WILLNEED",
1193 "IO::AIO::MADV_DONTNEED".
1194
1195 On systems that do not implement "posix_madvise", this function
1196 returns ENOSYS, otherwise the return value of "posix_madvise".
1197
1198 IO::AIO::mprotect $scalar, $offset, $len, $protect
1199 Simply calls the "mprotect" function on the preferably AIO::mmap'ed
1200 $scalar (see its manpage for details). The following protect
1201 constants are avaiable: "IO::AIO::PROT_NONE", "IO::AIO::PROT_READ",
1202 "IO::AIO::PROT_WRITE", "IO::AIO::PROT_EXEC".
1203
1204 On systems that do not implement "mprotect", this function returns
1205 ENOSYS, otherwise the return value of "mprotect".
1206
1207 IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
1208 Memory-maps a file (or anonymous memory range) and attaches it to
1209 the given $scalar, which will act like a string scalar.
1210
1211 The only operations allowed on the scalar are "substr"/"vec" that
1212 don't change the string length, and most read-only operations such
1213 as copying it or searching it with regexes and so on.
1214
1215 Anything else is unsafe and will, at best, result in memory leaks.
1216
1217 The memory map associated with the $scalar is automatically removed
1218 when the $scalar is destroyed, or when the "IO::AIO::mmap" or
1219 "IO::AIO::munmap" functions are called.
1220
1221 This calls the "mmap"(2) function internally. See your system's
1222 manual page for details on the $length, $prot and $flags parameters.
1223
1224 The $length must be larger than zero and smaller than the actual
1225 filesize.
1226
1227 $prot is a combination of "IO::AIO::PROT_NONE",
1228 "IO::AIO::PROT_EXEC", "IO::AIO::PROT_READ" and/or
1229 "IO::AIO::PROT_WRITE",
1230
1231 $flags can be a combination of "IO::AIO::MAP_SHARED" or
1232 "IO::AIO::MAP_PRIVATE", or a number of system-specific flags (when
1233 not available, the are defined as 0): "IO::AIO::MAP_ANONYMOUS"
1234 (which is set to "MAP_ANON" if your system only provides this
1235 constant), "IO::AIO::MAP_HUGETLB", "IO::AIO::MAP_LOCKED",
1236 "IO::AIO::MAP_NORESERVE", "IO::AIO::MAP_POPULATE" or
1237 "IO::AIO::MAP_NONBLOCK"
1238
1239 If $fh is "undef", then a file descriptor of -1 is passed.
1240
1241 $offset is the offset from the start of the file - it generally must
1242 be a multiple of "IO::AIO::PAGESIZE" and defaults to 0.
1243
1244 Example:
1245
1246 use Digest::MD5;
1247 use IO::AIO;
1248
1249 open my $fh, "<verybigfile"
1250 or die "$!";
1251
1252 IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
1253 or die "verybigfile: $!";
1254
1255 my $fast_md5 = md5 $data;
1256
1257 IO::AIO::munmap $scalar
1258 Removes a previous mmap and undefines the $scalar.
1259
1260 IO::AIO::munlock $scalar, $offset = 0, $length = undef
1261 Calls the "munlock" function, undoing the effects of a previous
1262 "aio_mlock" call (see its description for details).
1263
1264 IO::AIO::munlockall
1265 Calls the "munlockall" function.
1266
1267 On systems that do not implement "munlockall", this function returns
1268 ENOSYS, otherwise the return value of "munlockall".
1269
1270EVENT LOOP INTEGRATION
1271 It is recommended to use AnyEvent::AIO to integrate IO::AIO
1272 automatically into many event loops:
1273
1274 # AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
1275 use AnyEvent::AIO;
1276
1277 You can also integrate IO::AIO manually into many event loops, here are
1278 some examples of how to do this:
1279
1280 # EV integration
1281 my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
1282
1283 # Event integration
1284 Event->io (fd => IO::AIO::poll_fileno,
1285 poll => 'r',
1286 cb => \&IO::AIO::poll_cb);
1287
1288 # Glib/Gtk2 integration
1289 add_watch Glib::IO IO::AIO::poll_fileno,
1290 in => sub { IO::AIO::poll_cb; 1 };
1291
1292 # Tk integration
1293 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
1294 readable => \&IO::AIO::poll_cb);
1295
1296 # Danga::Socket integration
1297 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
1298 \&IO::AIO::poll_cb);
838 1299
839 FORK BEHAVIOUR 1300 FORK BEHAVIOUR
840 This module should do "the right thing" when the process using it 1301 This module should do "the right thing" when the process using it forks:
841 forks:
842 1302
843 Before the fork, IO::AIO enters a quiescent state where no requests 1303 Before the fork, IO::AIO enters a quiescent state where no requests can
844 can be added in other threads and no results will be processed. 1304 be added in other threads and no results will be processed. After the
845 After the fork the parent simply leaves the quiescent state and 1305 fork the parent simply leaves the quiescent state and continues
846 continues request/result processing, while the child frees the 1306 request/result processing, while the child frees the request/result
847 request/result queue (so that the requests started before the fork 1307 queue (so that the requests started before the fork will only be handled
848 will only be handled in the parent). Threads will be started on 1308 in the parent). Threads will be started on demand until the limit set in
849 demand until the limit set in the parent process has been reached 1309 the parent process has been reached again.
850 again.
851 1310
852 In short: the parent will, after a short pause, continue as if fork 1311 In short: the parent will, after a short pause, continue as if fork had
853 had not been called, while the child will act as if IO::AIO has not 1312 not been called, while the child will act as if IO::AIO has not been
854 been used yet. 1313 used yet.
855 1314
856 MEMORY USAGE 1315 MEMORY USAGE
857 Per-request usage: 1316 Per-request usage:
858 1317
859 Each aio request uses - depending on your architecture - around 1318 Each aio request uses - depending on your architecture - around 100-200
860 100-200 bytes of memory. In addition, stat requests need a stat 1319 bytes of memory. In addition, stat requests need a stat buffer (possibly
861 buffer (possibly a few hundred bytes), readdir requires a result 1320 a few hundred bytes), readdir requires a result buffer and so on. Perl
862 buffer and so on. Perl scalars and other data passed into aio 1321 scalars and other data passed into aio requests will also be locked and
863 requests will also be locked and will consume memory till the 1322 will consume memory till the request has entered the done state.
864 request has entered the done state.
865 1323
866 This is now awfully much, so queuing lots of requests is not usually 1324 This is not awfully much, so queuing lots of requests is not usually a
867 a problem. 1325 problem.
868 1326
869 Per-thread usage: 1327 Per-thread usage:
870 1328
871 In the execution phase, some aio requests require more memory for 1329 In the execution phase, some aio requests require more memory for
872 temporary buffers, and each thread requires a stack and other data 1330 temporary buffers, and each thread requires a stack and other data
873 structures (usually around 16k-128k, depending on the OS). 1331 structures (usually around 16k-128k, depending on the OS).
874 1332
875KNOWN BUGS 1333KNOWN BUGS
876 Known bugs will be fixed in the next release. 1334 Known bugs will be fixed in the next release.
877 1335
878SEE ALSO 1336SEE ALSO
879 Coro::AIO. 1337 AnyEvent::AIO for easy integration into event loops, Coro::AIO for a
1338 more natural syntax.
880 1339
881AUTHOR 1340AUTHOR
882 Marc Lehmann <schmorp@schmorp.de> 1341 Marc Lehmann <schmorp@schmorp.de>
883 http://home.schmorp.de/ 1342 http://home.schmorp.de/
884 1343

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