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Revision 1.45 by root, Thu Dec 30 07:19:31 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 Please note that "aio_sendfile" can read more bytes from $in_fh than
365 are written, and there is no way to find out how many bytes have
366 been read from "aio_sendfile" alone, as "aio_sendfile" only provides
367 the number of bytes written to $out_fh. Only if the result value
368 equals $length one can assume that $length bytes have been read.
369
370 Unlike with other "aio_" functions, it makes a lot of sense to use
371 "aio_sendfile" on non-blocking sockets, as long as one end
372 (typically the $in_fh) is a file - the file I/O will then be
373 asynchronous, while the socket I/O will be non-blocking. Note,
374 however, that you can run into a trap where "aio_sendfile" reads
375 some data with readahead, then fails to write all data, and when the
376 socket is ready the next time, the data in the cache is already
377 lost, forcing "aio_sendfile" to again hit the disk. Explicit
378 "aio_read" + "aio_write" let's you control resource usage much
379 better.
380
381 This call tries to make use of a native "sendfile" syscall to
382 provide zero-copy operation. For this to work, $out_fh should refer
383 to a socket, and $in_fh should refer to an mmap'able file.
384
385 If a native sendfile cannot be found or it fails with "ENOSYS",
386 "ENOTSUP", "EOPNOTSUPP", "EAFNOSUPPORT", "EPROTOTYPE" or "ENOTSOCK",
387 it will be emulated, so you can call "aio_sendfile" on any type of
388 filehandle regardless of the limitations of the operating system.
389
390 aio_readahead $fh,$offset,$length, $callback->($retval)
391 "aio_readahead" populates the page cache with data from a file so
392 that subsequent reads from that file will not block on disk I/O. The
393 $offset argument specifies the starting point from which data is to
394 be read and $length specifies the number of bytes to be read. I/O is
395 performed in whole pages, so that offset is effectively rounded down
396 to a page boundary and bytes are read up to the next page boundary
397 greater than or equal to (off-set+length). "aio_readahead" does not
398 read beyond the end of the file. The current file offset of the file
399 is left unchanged.
400
401 If that syscall doesn't exist (likely if your OS isn't Linux) it
402 will be emulated by simply reading the data, which would have a
403 similar effect.
404
405 aio_stat $fh_or_path, $callback->($status)
406 aio_lstat $fh, $callback->($status)
407 Works like perl's "stat" or "lstat" in void context. The callback
408 will be called after the stat and the results will be available
409 using "stat _" or "-s _" etc...
410
411 The pathname passed to "aio_stat" must be absolute. See API NOTES,
412 above, for an explanation.
413
414 Currently, the stats are always 64-bit-stats, i.e. instead of
415 returning an error when stat'ing a large file, the results will be
416 silently truncated unless perl itself is compiled with large file
417 support.
418
419 Example: Print the length of /etc/passwd:
420
421 aio_stat "/etc/passwd", sub {
422 $_[0] and die "stat failed: $!";
423 print "size is ", -s _, "\n";
424 };
425
426 aio_statvfs $fh_or_path, $callback->($statvfs)
427 Works like the POSIX "statvfs" or "fstatvfs" syscalls, depending on
428 whether a file handle or path was passed.
429
430 On success, the callback is passed a hash reference with the
431 following members: "bsize", "frsize", "blocks", "bfree", "bavail",
432 "files", "ffree", "favail", "fsid", "flag" and "namemax". On
433 failure, "undef" is passed.
434
435 The following POSIX IO::AIO::ST_* constants are defined: "ST_RDONLY"
436 and "ST_NOSUID".
437
438 The following non-POSIX IO::AIO::ST_* flag masks are defined to
439 their correct value when available, or to 0 on systems that do not
440 support them: "ST_NODEV", "ST_NOEXEC", "ST_SYNCHRONOUS",
441 "ST_MANDLOCK", "ST_WRITE", "ST_APPEND", "ST_IMMUTABLE",
442 "ST_NOATIME", "ST_NODIRATIME" and "ST_RELATIME".
443
444 Example: stat "/wd" and dump out the data if successful.
445
446 aio_statvfs "/wd", sub {
447 my $f = $_[0]
448 or die "statvfs: $!";
449
450 use Data::Dumper;
451 say Dumper $f;
452 };
453
454 # result:
455 {
456 bsize => 1024,
457 bfree => 4333064312,
458 blocks => 10253828096,
459 files => 2050765568,
460 flag => 4096,
461 favail => 2042092649,
462 bavail => 4333064312,
463 ffree => 2042092649,
464 namemax => 255,
465 frsize => 1024,
466 fsid => 1810
467 }
468
469 aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
470 Works like perl's "utime" function (including the special case of
471 $atime and $mtime being undef). Fractional times are supported if
472 the underlying syscalls support them.
473
474 When called with a pathname, uses utimes(2) if available, otherwise
475 utime(2). If called on a file descriptor, uses futimes(2) if
476 available, otherwise returns ENOSYS, so this is not portable.
477
478 Examples:
479
480 # set atime and mtime to current time (basically touch(1)):
481 aio_utime "path", undef, undef;
482 # set atime to current time and mtime to beginning of the epoch:
483 aio_utime "path", time, undef; # undef==0
484
485 aio_chown $fh_or_path, $uid, $gid, $callback->($status)
486 Works like perl's "chown" function, except that "undef" for either
487 $uid or $gid is being interpreted as "do not change" (but -1 can
488 also be used).
489
490 Examples:
491
492 # same as "chown root path" in the shell:
493 aio_chown "path", 0, -1;
494 # same as above:
495 aio_chown "path", 0, undef;
496
497 aio_truncate $fh_or_path, $offset, $callback->($status)
498 Works like truncate(2) or ftruncate(2).
499
500 aio_chmod $fh_or_path, $mode, $callback->($status)
501 Works like perl's "chmod" function.
502
503 aio_unlink $pathname, $callback->($status)
504 Asynchronously unlink (delete) a file and call the callback with the
505 result code.
506
507 aio_mknod $path, $mode, $dev, $callback->($status)
508 [EXPERIMENTAL]
509
510 Asynchronously create a device node (or fifo). See mknod(2).
511
512 The only (POSIX-) portable way of calling this function is:
513
514 aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...
515
516 aio_link $srcpath, $dstpath, $callback->($status)
517 Asynchronously create a new link to the existing object at $srcpath
518 at the path $dstpath and call the callback with the result code.
519
520 aio_symlink $srcpath, $dstpath, $callback->($status)
521 Asynchronously create a new symbolic link to the existing object at
522 $srcpath at the path $dstpath and call the callback with the result
523 code.
524
525 aio_readlink $path, $callback->($link)
526 Asynchronously read the symlink specified by $path and pass it to
527 the callback. If an error occurs, nothing or undef gets passed to
528 the callback.
529
530 aio_rename $srcpath, $dstpath, $callback->($status)
531 Asynchronously rename the object at $srcpath to $dstpath, just as
532 rename(2) and call the callback with the result code.
533
534 aio_mkdir $pathname, $mode, $callback->($status)
535 Asynchronously mkdir (create) a directory and call the callback with
536 the result code. $mode will be modified by the umask at the time the
537 request is executed, so do not change your umask.
538
539 aio_rmdir $pathname, $callback->($status)
540 Asynchronously rmdir (delete) a directory and call the callback with
541 the result code.
542
543 aio_readdir $pathname, $callback->($entries)
544 Unlike the POSIX call of the same name, "aio_readdir" reads an
545 entire directory (i.e. opendir + readdir + closedir). The entries
546 will not be sorted, and will NOT include the "." and ".." entries.
547
548 The callback is passed a single argument which is either "undef" or
549 an array-ref with the filenames.
550
551 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
552 Quite similar to "aio_readdir", but the $flags argument allows to
553 tune behaviour and output format. In case of an error, $entries will
554 be "undef".
555
556 The flags are a combination of the following constants, ORed
557 together (the flags will also be passed to the callback, possibly
558 modified):
559
560 IO::AIO::READDIR_DENTS
561 When this flag is off, then the callback gets an arrayref with
562 of names only (as with "aio_readdir"), otherwise it gets an
563 arrayref with "[$name, $type, $inode]" arrayrefs, each
564 describing a single directory entry in more detail.
565
566 $name is the name of the entry.
567
568 $type is one of the "IO::AIO::DT_xxx" constants:
569
570 "IO::AIO::DT_UNKNOWN", "IO::AIO::DT_FIFO", "IO::AIO::DT_CHR",
571 "IO::AIO::DT_DIR", "IO::AIO::DT_BLK", "IO::AIO::DT_REG",
572 "IO::AIO::DT_LNK", "IO::AIO::DT_SOCK", "IO::AIO::DT_WHT".
573
574 "IO::AIO::DT_UNKNOWN" means just that: readdir does not know. If
575 you need to know, you have to run stat yourself. Also, for speed
576 reasons, the $type scalars are read-only: you can not modify
577 them.
578
579 $inode is the inode number (which might not be exact on systems
580 with 64 bit inode numbers and 32 bit perls). This field has
581 unspecified content on systems that do not deliver the inode
582 information.
583
584 IO::AIO::READDIR_DIRS_FIRST
585 When this flag is set, then the names will be returned in an
586 order where likely directories come first. This is useful when
587 you need to quickly find directories, or you want to find all
588 directories while avoiding to stat() each entry.
589
590 If the system returns type information in readdir, then this is
591 used to find directories directly. Otherwise, likely directories
592 are files beginning with ".", or otherwise files with no dots,
593 of which files with short names are tried first.
594
595 IO::AIO::READDIR_STAT_ORDER
596 When this flag is set, then the names will be returned in an
597 order suitable for stat()'ing each one. That is, when you plan
598 to stat() all files in the given directory, then the returned
599 order will likely be fastest.
600
601 If both this flag and "IO::AIO::READDIR_DIRS_FIRST" are
602 specified, then the likely dirs come first, resulting in a less
603 optimal stat order.
604
605 IO::AIO::READDIR_FOUND_UNKNOWN
606 This flag should not be set when calling "aio_readdirx".
607 Instead, it is being set by "aio_readdirx", when any of the
608 $type's found were "IO::AIO::DT_UNKNOWN". The absense of this
609 flag therefore indicates that all $type's are known, which can
610 be used to speed up some algorithms.
611
612 aio_load $path, $data, $callback->($status)
613 This is a composite request that tries to fully load the given file
614 into memory. Status is the same as with aio_read.
615
616 aio_copy $srcpath, $dstpath, $callback->($status)
617 Try to copy the *file* (directories not supported as either source
618 or destination) from $srcpath to $dstpath and call the callback with
619 a status of 0 (ok) or -1 (error, see $!).
620
621 This is a composite request that creates the destination file with
622 mode 0200 and copies the contents of the source file into it using
623 "aio_sendfile", followed by restoring atime, mtime, access mode and
624 uid/gid, in that order.
625
626 If an error occurs, the partial destination file will be unlinked,
627 if possible, except when setting atime, mtime, access mode and
628 uid/gid, where errors are being ignored.
629
630 aio_move $srcpath, $dstpath, $callback->($status)
631 Try to move the *file* (directories not supported as either source
632 or destination) from $srcpath to $dstpath and call the callback with
633 a status of 0 (ok) or -1 (error, see $!).
634
635 This is a composite request that tries to rename(2) the file first;
636 if rename fails with "EXDEV", it copies the file with "aio_copy"
637 and, if that is successful, unlinks the $srcpath.
638
639 aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
640 Scans a directory (similar to "aio_readdir") but additionally tries
641 to efficiently separate the entries of directory $path into two sets
642 of names, directories you can recurse into (directories), and ones
643 you cannot recurse into (everything else, including symlinks to
644 directories).
645
646 "aio_scandir" is a composite request that creates of many sub
647 requests_ $maxreq specifies the maximum number of outstanding aio
648 requests that this function generates. If it is "<= 0", then a
649 suitable default will be chosen (currently 4).
650
651 On error, the callback is called without arguments, otherwise it
652 receives two array-refs with path-relative entry names.
653
654 Example:
655
656 aio_scandir $dir, 0, sub {
657 my ($dirs, $nondirs) = @_;
658 print "real directories: @$dirs\n";
659 print "everything else: @$nondirs\n";
660 };
661
662 Implementation notes.
663
664 The "aio_readdir" cannot be avoided, but "stat()"'ing every entry
665 can.
666
667 If readdir returns file type information, then this is used directly
668 to find directories.
669
670 Otherwise, after reading the directory, the modification time, size
671 etc. of the directory before and after the readdir is checked, and
672 if they match (and isn't the current time), the link count will be
673 used to decide how many entries are directories (if >= 2).
674 Otherwise, no knowledge of the number of subdirectories will be
675 assumed.
676
677 Then entries will be sorted into likely directories a non-initial
678 dot currently) and likely non-directories (see "aio_readdirx"). Then
679 every entry plus an appended "/." will be "stat"'ed, likely
680 directories first, in order of their inode numbers. If that
681 succeeds, it assumes that the entry is a directory or a symlink to
682 directory (which will be checked seperately). This is often faster
683 than stat'ing the entry itself because filesystems might detect the
684 type of the entry without reading the inode data (e.g. ext2fs
685 filetype feature), even on systems that cannot return the filetype
686 information on readdir.
687
688 If the known number of directories (link count - 2) has been
689 reached, the rest of the entries is assumed to be non-directories.
690
691 This only works with certainty on POSIX (= UNIX) filesystems, which
692 fortunately are the vast majority of filesystems around.
693
694 It will also likely work on non-POSIX filesystems with reduced
695 efficiency as those tend to return 0 or 1 as link counts, which
696 disables the directory counting heuristic.
697
698 aio_rmtree $path, $callback->($status)
699 Delete a directory tree starting (and including) $path, return the
700 status of the final "rmdir" only. This is a composite request that
701 uses "aio_scandir" to recurse into and rmdir directories, and unlink
702 everything else.
703
704 aio_sync $callback->($status)
705 Asynchronously call sync and call the callback when finished.
706
707 aio_fsync $fh, $callback->($status)
708 Asynchronously call fsync on the given filehandle and call the
709 callback with the fsync result code.
710
711 aio_fdatasync $fh, $callback->($status)
712 Asynchronously call fdatasync on the given filehandle and call the
713 callback with the fdatasync result code.
714
715 If this call isn't available because your OS lacks it or it couldn't
716 be detected, it will be emulated by calling "fsync" instead.
717
718 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
719 Sync the data portion of the file specified by $offset and $length
720 to disk (but NOT the metadata), by calling the Linux-specific
721 sync_file_range call. If sync_file_range is not available or it
722 returns ENOSYS, then fdatasync or fsync is being substituted.
723
724 $flags can be a combination of
725 "IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE",
726 "IO::AIO::SYNC_FILE_RANGE_WRITE" and
727 "IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER": refer to the sync_file_range
728 manpage for details.
729
730 aio_pathsync $path, $callback->($status)
731 This request tries to open, fsync and close the given path. This is
732 a composite request intended to sync directories after directory
733 operations (E.g. rename). This might not work on all operating
734 systems or have any specific effect, but usually it makes sure that
735 directory changes get written to disc. It works for anything that
736 can be opened for read-only, not just directories.
737
738 Future versions of this function might fall back to other methods
739 when "fsync" on the directory fails (such as calling "sync").
740
741 Passes 0 when everything went ok, and -1 on error.
742
743 aio_msync $scalar, $offset = 0, $length = undef, flags = 0,
744 $callback->($status)
745 This is a rather advanced IO::AIO call, which only works on
746 mmap(2)ed scalars (see the "IO::AIO::mmap" function, although it
747 also works on data scalars managed by the Sys::Mmap or Mmap modules,
748 note that the scalar must only be modified in-place while an aio
749 operation is pending on it).
750
751 It calls the "msync" function of your OS, if available, with the
752 memory area starting at $offset in the string and ending $length
753 bytes later. If $length is negative, counts from the end, and if
754 $length is "undef", then it goes till the end of the string. The
755 flags can be a combination of "IO::AIO::MS_ASYNC",
756 "IO::AIO::MS_INVALIDATE" and "IO::AIO::MS_SYNC".
757
758 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0,
759 $callback->($status)
760 This is a rather advanced IO::AIO call, which works best on
761 mmap(2)ed scalars.
762
763 It touches (reads or writes) all memory pages in the specified range
764 inside the scalar. All caveats and parameters are the same as for
765 "aio_msync", above, except for flags, which must be either 0 (which
766 reads all pages and ensures they are instantiated) or
767 "IO::AIO::MT_MODIFY", which modifies the memory page s(by reading
768 and writing an octet from it, which dirties the page).
769
770 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
771 This is a rather advanced IO::AIO call, which works best on
772 mmap(2)ed scalars.
773
774 It reads in all the pages of the underlying storage into memory (if
775 any) and locks them, so they are not getting swapped/paged out or
776 removed.
777
778 If $length is undefined, then the scalar will be locked till the
779 end.
780
781 On systems that do not implement "mlock", this function returns -1
782 and sets errno to "ENOSYS".
783
784 Note that the corresponding "munlock" is synchronous and is
785 documented under "MISCELLANEOUS FUNCTIONS".
786
787 Example: open a file, mmap and mlock it - both will be undone when
788 $data gets destroyed.
789
790 open my $fh, "<", $path or die "$path: $!";
791 my $data;
792 IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
793 aio_mlock $data; # mlock in background
794
795 aio_mlockall $flags, $callback->($status)
796 Calls the "mlockall" function with the given $flags (a combination
797 of "IO::AIO::MCL_CURRENT" and "IO::AIO::MCL_FUTURE").
798
799 On systems that do not implement "mlockall", this function returns
800 -1 and sets errno to "ENOSYS".
801
802 Note that the corresponding "munlockall" is synchronous and is
803 documented under "MISCELLANEOUS FUNCTIONS".
804
805 Example: asynchronously lock all current and future pages into
806 memory.
807
808 aio_mlockall IO::AIO::MCL_FUTURE;
809
810 aio_group $callback->(...)
811 This is a very special aio request: Instead of doing something, it
812 is a container for other aio requests, which is useful if you want
813 to bundle many requests into a single, composite, request with a
814 definite callback and the ability to cancel the whole request with
815 its subrequests.
816
817 Returns an object of class IO::AIO::GRP. See its documentation below
818 for more info.
819
820 Example:
821
822 my $grp = aio_group sub {
823 print "all stats done\n";
824 };
825
826 add $grp
827 (aio_stat ...),
828 (aio_stat ...),
829 ...;
830
831 aio_nop $callback->()
832 This is a special request - it does nothing in itself and is only
833 used for side effects, such as when you want to add a dummy request
834 to a group so that finishing the requests in the group depends on
835 executing the given code.
836
837 While this request does nothing, it still goes through the execution
838 phase and still requires a worker thread. Thus, the callback will
839 not be executed immediately but only after other requests in the
840 queue have entered their execution phase. This can be used to
841 measure request latency.
842
843 IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
844 Mainly used for debugging and benchmarking, this aio request puts
845 one of the request workers to sleep for the given time.
846
847 While it is theoretically handy to have simple I/O scheduling
848 requests like sleep and file handle readable/writable, the overhead
849 this creates is immense (it blocks a thread for a long time) so do
850 not use this function except to put your application under
851 artificial I/O pressure.
852
853 IO::AIO::REQ CLASS
854 All non-aggregate "aio_*" functions return an object of this class when
855 called in non-void context.
856
857 cancel $req
858 Cancels the request, if possible. Has the effect of skipping
859 execution when entering the execute state and skipping calling the
860 callback when entering the the result state, but will leave the
861 request otherwise untouched (with the exception of readdir). That
862 means that requests that currently execute will not be stopped and
863 resources held by the request will not be freed prematurely.
864
865 cb $req $callback->(...)
866 Replace (or simply set) the callback registered to the request.
867
868 IO::AIO::GRP CLASS
869 This class is a subclass of IO::AIO::REQ, so all its methods apply to
870 objects of this class, too.
871
872 A IO::AIO::GRP object is a special request that can contain multiple
873 other aio requests.
874
875 You create one by calling the "aio_group" constructing function with a
876 callback that will be called when all contained requests have entered
877 the "done" state:
878
879 my $grp = aio_group sub {
880 print "all requests are done\n";
881 };
882
883 You add requests by calling the "add" method with one or more
884 "IO::AIO::REQ" objects:
885
886 $grp->add (aio_unlink "...");
887
888 add $grp aio_stat "...", sub {
889 $_[0] or return $grp->result ("error");
890
891 # add another request dynamically, if first succeeded
892 add $grp aio_open "...", sub {
893 $grp->result ("ok");
894 };
895 };
896
573 This makes it very easy to create composite requests (see the source 897 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 898 "aio_move" for an application) that work and feel like simple requests.
575 requests.
576 899
577 * The IO::AIO::GRP objects will be cleaned up during calls to 900 * The IO::AIO::GRP objects will be cleaned up during calls to
578 "IO::AIO::poll_cb", just like any other request. 901 "IO::AIO::poll_cb", just like any other request.
902
579 * They can be canceled like any other request. Canceling will cancel 903 * They can be canceled like any other request. Canceling will cancel
580 not only the request itself, but also all requests it contains. 904 not only the request itself, but also all requests it contains.
905
581 * They can also can also be added to other IO::AIO::GRP objects. 906 * They can also can also be added to other IO::AIO::GRP objects.
907
582 * You must not add requests to a group from within the group 908 * You must not add requests to a group from within the group callback
583 callback (or any later time). 909 (or any later time).
584 910
585 Their lifetime, simplified, looks like this: when they are empty, 911 Their lifetime, simplified, looks like this: when they are empty, they
586 they will finish very quickly. If they contain only requests that 912 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 913 "done" state, they will also finish. Otherwise they will continue to
588 continue to exist. 914 exist.
589 915
590 That means after creating a group you have some time to add 916 That means after creating a group you have some time to add requests
917 (precisely before the callback has been invoked, which is only done
591 requests. And in the callbacks of those requests, you can add 918 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 919 add further requests to the group. And only when all those requests have
593 finished will the the group itself finish. 920 finished will the the group itself finish.
594 921
595 add $grp ... 922 add $grp ...
596 $grp->add (...) 923 $grp->add (...)
597 Add one or more requests to the group. Any type of IO::AIO::REQ 924 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 925 be added, including other groups, as long as you do not create
599 create circular dependencies. 926 circular dependencies.
600 927
601 Returns all its arguments. 928 Returns all its arguments.
602 929
603 $grp->cancel_subs 930 $grp->cancel_subs
604 Cancel all subrequests and clears any feeder, but not the group 931 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 932 request itself. Useful when you queued a lot of events but got a
606 result early. 933 result early.
607 934
935 The group request will finish normally (you cannot add requests to
936 the group).
937
608 $grp->result (...) 938 $grp->result (...)
609 Set the result value(s) that will be passed to the group 939 Set the result value(s) that will be passed to the group callback
610 callback when all subrequests have finished and set thre groups 940 when all subrequests have finished and set the groups errno to the
611 errno to the current value of errno (just like calling "errno" 941 current value of errno (just like calling "errno" without an error
612 without an error number). By default, no argument will be passed 942 number). By default, no argument will be passed and errno is zero.
613 and errno is zero.
614 943
615 $grp->errno ([$errno]) 944 $grp->errno ([$errno])
616 Sets the group errno value to $errno, or the current value of 945 Sets the group errno value to $errno, or the current value of errno
617 errno when the argument is missing. 946 when the argument is missing.
618 947
619 Every aio request has an associated errno value that is restored 948 Every aio request has an associated errno value that is restored
620 when the callback is invoked. This method lets you change this 949 when the callback is invoked. This method lets you change this value
621 value from its default (0). 950 from its default (0).
622 951
623 Calling "result" will also set errno, so make sure you either 952 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. 953 before the call to "result", or call c<errno> after it.
625 954
626 feed $grp $callback->($grp) 955 feed $grp $callback->($grp)
627 Sets a feeder/generator on this group: every group can have an 956 Sets a feeder/generator on this group: every group can have an
628 attached generator that generates requests if idle. The idea 957 attached generator that generates requests if idle. The idea behind
629 behind this is that, although you could just queue as many 958 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 959 want in a group, this might starve other requests for a potentially
631 requests for a potentially long time. For example, "aio_scandir" 960 long time. For example, "aio_scandir" might generate hundreds of
632 might generate hundreds of thousands "aio_stat" requests, 961 thousands "aio_stat" requests, delaying any later requests for a
633 delaying any later requests for a long time. 962 long time.
634 963
635 To avoid this, and allow incremental generation of requests, you 964 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 965 instead a group and set a feeder on it that generates those
637 requests. The feed callback will be called whenever there are 966 requests. The feed callback will be called whenever there are few
638 few enough (see "limit", below) requests active in the group 967 enough (see "limit", below) requests active in the group itself and
639 itself and is expected to queue more requests. 968 is expected to queue more requests.
640 969
641 The feed callback can queue as many requests as it likes (i.e. 970 The feed callback can queue as many requests as it likes (i.e. "add"
642 "add" does not impose any limits). 971 does not impose any limits).
643 972
644 If the feed does not queue more requests when called, it will be 973 If the feed does not queue more requests when called, it will be
645 automatically removed from the group. 974 automatically removed from the group.
646 975
647 If the feed limit is 0, it will be set to 2 automatically. 976 If the feed limit is 0 when this method is called, it will be set to
977 2 automatically.
648 978
649 Example: 979 Example:
650 980
651 # stat all files in @files, but only ever use four aio requests concurrently: 981 # stat all files in @files, but only ever use four aio requests concurrently:
652 982
653 my $grp = aio_group sub { print "finished\n" }; 983 my $grp = aio_group sub { print "finished\n" };
654 limit $grp 4; 984 limit $grp 4;
655 feed $grp sub { 985 feed $grp sub {
656 my $file = pop @files 986 my $file = pop @files
657 or return; 987 or return;
658 988
659 add $grp aio_stat $file, sub { ... }; 989 add $grp aio_stat $file, sub { ... };
660 }; 990 };
661 991
662 limit $grp $num 992 limit $grp $num
663 Sets the feeder limit for the group: The feeder will be called 993 Sets the feeder limit for the group: The feeder will be called
664 whenever the group contains less than this many requests. 994 whenever the group contains less than this many requests.
665 995
666 Setting the limit to 0 will pause the feeding process. 996 Setting the limit to 0 will pause the feeding process.
997
998 The default value for the limit is 0, but note that setting a feeder
999 automatically bumps it up to 2.
667 1000
668 SUPPORT FUNCTIONS 1001 SUPPORT FUNCTIONS
669 EVENT PROCESSING AND EVENT LOOP INTEGRATION 1002 EVENT PROCESSING AND EVENT LOOP INTEGRATION
670 $fileno = IO::AIO::poll_fileno 1003 $fileno = IO::AIO::poll_fileno
671 Return the *request result pipe file descriptor*. This 1004 Return the *request result pipe file descriptor*. This filehandle
672 filehandle must be polled for reading by some mechanism outside 1005 must be polled for reading by some mechanism outside this module
673 this module (e.g. Event or select, see below or the SYNOPSIS). 1006 (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 1007 pipe becomes readable you have to call "poll_cb" to check the
675 the results. 1008 results.
676 1009
677 See "poll_cb" for an example. 1010 See "poll_cb" for an example.
678 1011
679 IO::AIO::poll_cb 1012 IO::AIO::poll_cb
680 Process some outstanding events on the result pipe. You have to 1013 Process some outstanding events on the result pipe. You have to call
681 call this regularly. Returns the number of events processed. 1014 this regularly. Returns 0 if all events could be processed, or -1 if
682 Returns immediately when no events are outstanding. The amount 1015 it returned earlier for whatever reason. Returns immediately when no
683 of events processed depends on the settings of 1016 events are outstanding. The amount of events processed depends on
684 "IO::AIO::max_poll_req" and "IO::AIO::max_poll_time". 1017 the settings of "IO::AIO::max_poll_req" and
1018 "IO::AIO::max_poll_time".
685 1019
686 If not all requests were processed for whatever reason, the 1020 If not all requests were processed for whatever reason, the
687 filehandle will still be ready when "poll_cb" returns. 1021 filehandle will still be ready when "poll_cb" returns, so normally
1022 you don't have to do anything special to have it called later.
688 1023
689 Example: Install an Event watcher that automatically calls 1024 Example: Install an Event watcher that automatically calls
690 IO::AIO::poll_cb with high priority: 1025 IO::AIO::poll_cb with high priority (more examples can be found in
1026 the SYNOPSIS section, at the top of this document):
691 1027
692 Event->io (fd => IO::AIO::poll_fileno, 1028 Event->io (fd => IO::AIO::poll_fileno,
693 poll => 'r', async => 1, 1029 poll => 'r', async => 1,
694 cb => \&IO::AIO::poll_cb); 1030 cb => \&IO::AIO::poll_cb);
695 1031
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 1032 IO::AIO::poll_wait
1033 If there are any outstanding requests and none of them in the result
725 Wait till the result filehandle becomes ready for reading 1034 phase, wait till the result filehandle becomes ready for reading
726 (simply does a "select" on the filehandle. This is useful if you 1035 (simply does a "select" on the filehandle. This is useful if you
727 want to synchronously wait for some requests to finish). 1036 want to synchronously wait for some requests to finish).
728 1037
729 See "nreqs" for an example. 1038 See "nreqs" for an example.
730 1039
731 IO::AIO::poll 1040 IO::AIO::poll
732 Waits until some requests have been handled. 1041 Waits until some requests have been handled.
733 1042
1043 Returns the number of requests processed, but is otherwise strictly
734 Strictly equivalent to: 1044 equivalent to:
735 1045
736 IO::AIO::poll_wait, IO::AIO::poll_cb 1046 IO::AIO::poll_wait, IO::AIO::poll_cb
737 if IO::AIO::nreqs;
738 1047
739 IO::AIO::flush 1048 IO::AIO::flush
740 Wait till all outstanding AIO requests have been handled. 1049 Wait till all outstanding AIO requests have been handled.
741 1050
742 Strictly equivalent to: 1051 Strictly equivalent to:
743 1052
744 IO::AIO::poll_wait, IO::AIO::poll_cb 1053 IO::AIO::poll_wait, IO::AIO::poll_cb
745 while IO::AIO::nreqs; 1054 while IO::AIO::nreqs;
1055
1056 IO::AIO::max_poll_reqs $nreqs
1057 IO::AIO::max_poll_time $seconds
1058 These set the maximum number of requests (default 0, meaning
1059 infinity) that are being processed by "IO::AIO::poll_cb" in one
1060 call, respectively the maximum amount of time (default 0, meaning
1061 infinity) spent in "IO::AIO::poll_cb" to process requests (more
1062 correctly the mininum amount of time "poll_cb" is allowed to use).
1063
1064 Setting "max_poll_time" to a non-zero value creates an overhead of
1065 one syscall per request processed, which is not normally a problem
1066 unless your callbacks are really really fast or your OS is really
1067 really slow (I am not mentioning Solaris here). Using
1068 "max_poll_reqs" incurs no overhead.
1069
1070 Setting these is useful if you want to ensure some level of
1071 interactiveness when perl is not fast enough to process all requests
1072 in time.
1073
1074 For interactive programs, values such as 0.01 to 0.1 should be fine.
1075
1076 Example: Install an Event watcher that automatically calls
1077 IO::AIO::poll_cb with low priority, to ensure that other parts of
1078 the program get the CPU sometimes even under high AIO load.
1079
1080 # try not to spend much more than 0.1s in poll_cb
1081 IO::AIO::max_poll_time 0.1;
1082
1083 # use a low priority so other tasks have priority
1084 Event->io (fd => IO::AIO::poll_fileno,
1085 poll => 'r', nice => 1,
1086 cb => &IO::AIO::poll_cb);
746 1087
747 CONTROLLING THE NUMBER OF THREADS 1088 CONTROLLING THE NUMBER OF THREADS
748 IO::AIO::min_parallel $nthreads 1089 IO::AIO::min_parallel $nthreads
749 Set the minimum number of AIO threads to $nthreads. The current 1090 Set the minimum number of AIO threads to $nthreads. The current
750 default is 8, which means eight asynchronous operations can 1091 default is 8, which means eight asynchronous operations can execute
751 execute concurrently at any one time (the number of outstanding 1092 concurrently at any one time (the number of outstanding requests,
752 requests, however, is unlimited). 1093 however, is unlimited).
753 1094
754 IO::AIO starts threads only on demand, when an AIO request is 1095 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 1096 and no free thread exists. Please note that queueing up a hundred
756 hundred requests can create demand for a hundred threads, even 1097 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 1098 out that everything is in the cache and could have been processed
758 been processed faster by a single thread. 1099 faster by a single thread.
759 1100
760 It is recommended to keep the number of threads relatively low, 1101 It is recommended to keep the number of threads relatively low, as
761 as some Linux kernel versions will scale negatively with the 1102 some Linux kernel versions will scale negatively with the number of
762 number of threads (higher parallelity => MUCH higher latency). 1103 threads (higher parallelity => MUCH higher latency). With current
763 With current Linux 2.6 versions, 4-32 threads should be fine. 1104 Linux 2.6 versions, 4-32 threads should be fine.
764 1105
765 Under most circumstances you don't need to call this function, 1106 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 1107 the module selects a default that is suitable for low to moderate
767 moderate load. 1108 load.
768 1109
769 IO::AIO::max_parallel $nthreads 1110 IO::AIO::max_parallel $nthreads
770 Sets the maximum number of AIO threads to $nthreads. If more 1111 Sets the maximum number of AIO threads to $nthreads. If more than
771 than the specified number of threads are currently running, this 1112 the specified number of threads are currently running, this function
772 function kills them. This function blocks until the limit is 1113 kills them. This function blocks until the limit is reached.
773 reached.
774 1114
775 While $nthreads are zero, aio requests get queued but not 1115 While $nthreads are zero, aio requests get queued but not executed
776 executed until the number of threads has been increased again. 1116 until the number of threads has been increased again.
777 1117
778 This module automatically runs "max_parallel 0" at program end, 1118 This module automatically runs "max_parallel 0" at program end, to
779 to ensure that all threads are killed and that there are no 1119 ensure that all threads are killed and that there are no outstanding
780 outstanding requests. 1120 requests.
781 1121
782 Under normal circumstances you don't need to call this function. 1122 Under normal circumstances you don't need to call this function.
783 1123
784 IO::AIO::max_idle $nthreads 1124 IO::AIO::max_idle $nthreads
785 Limit the number of threads (default: 4) that are allowed to 1125 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 1126 (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 1127 seconds). That means if a thread becomes idle while $nthreads other
788 other threads are also idle, it will free its resources and 1128 threads are also idle, it will free its resources and exit.
789 exit.
790 1129
791 This is useful when you allow a large number of threads (e.g. 1130 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 1131 1000) to allow for extremely high load situations, but want to free
793 want to free resources under normal circumstances (1000 threads 1132 resources under normal circumstances (1000 threads can easily
794 can easily consume 30MB of RAM). 1133 consume 30MB of RAM).
795 1134
796 The default is probably ok in most situations, especially if 1135 The default is probably ok in most situations, especially if thread
797 thread creation is fast. If thread creation is very slow on your 1136 creation is fast. If thread creation is very slow on your system you
798 system you might want to use larger values. 1137 might want to use larger values.
799 1138
800 $oldmaxreqs = IO::AIO::max_outstanding $maxreqs 1139 IO::AIO::max_outstanding $maxreqs
801 This is a very bad function to use in interactive programs 1140 This is a very bad function to use in interactive programs because
802 because it blocks, and a bad way to reduce concurrency because 1141 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 1142 inexact: Better use an "aio_group" together with a feed callback.
804 callback.
805 1143
806 Sets the maximum number of outstanding requests to $nreqs. If 1144 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 1145 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 1146 "poll_cb" (and "poll_some" and other functions calling "poll_cb")
809 "poll_cb") function will block until the limit is no longer 1147 function will block until the limit is no longer exceeded.
810 exceeded.
811 1148
812 The default value is very large, so there is no practical limit 1149 The default value is very large, so there is no practical limit on
813 on the number of outstanding requests. 1150 the number of outstanding requests.
814 1151
815 You can still queue as many requests as you want. Therefore, 1152 You can still queue as many requests as you want. Therefore,
816 "max_oustsanding" is mainly useful in simple scripts (with low 1153 "max_outstanding" is mainly useful in simple scripts (with low
817 values) or as a stop gap to shield against fatal memory overflow 1154 values) or as a stop gap to shield against fatal memory overflow
818 (with large values). 1155 (with large values).
819 1156
820 STATISTICAL INFORMATION 1157 STATISTICAL INFORMATION
821 IO::AIO::nreqs 1158 IO::AIO::nreqs
822 Returns the number of requests currently in the ready, execute 1159 Returns the number of requests currently in the ready, execute or
823 or pending states (i.e. for which their callback has not been 1160 pending states (i.e. for which their callback has not been invoked
824 invoked yet). 1161 yet).
825 1162
826 Example: wait till there are no outstanding requests anymore: 1163 Example: wait till there are no outstanding requests anymore:
827 1164
828 IO::AIO::poll_wait, IO::AIO::poll_cb 1165 IO::AIO::poll_wait, IO::AIO::poll_cb
829 while IO::AIO::nreqs; 1166 while IO::AIO::nreqs;
830 1167
831 IO::AIO::nready 1168 IO::AIO::nready
832 Returns the number of requests currently in the ready state (not 1169 Returns the number of requests currently in the ready state (not yet
833 yet executed). 1170 executed).
834 1171
835 IO::AIO::npending 1172 IO::AIO::npending
836 Returns the number of requests currently in the pending state 1173 Returns the number of requests currently in the pending state
837 (executed, but not yet processed by poll_cb). 1174 (executed, but not yet processed by poll_cb).
1175
1176 MISCELLANEOUS FUNCTIONS
1177 IO::AIO implements some functions that might be useful, but are not
1178 asynchronous.
1179
1180 IO::AIO::sendfile $ofh, $ifh, $offset, $count
1181 Calls the "eio_sendfile_sync" function, which is like
1182 "aio_sendfile", but is blocking (this makes most sense if you know
1183 the input data is likely cached already and the output filehandle is
1184 set to non-blocking operations).
1185
1186 Returns the number of bytes copied, or -1 on error.
1187
1188 IO::AIO::fadvise $fh, $offset, $len, $advice
1189 Simply calls the "posix_fadvise" function (see its manpage for
1190 details). The following advice constants are avaiable:
1191 "IO::AIO::FADV_NORMAL", "IO::AIO::FADV_SEQUENTIAL",
1192 "IO::AIO::FADV_RANDOM", "IO::AIO::FADV_NOREUSE",
1193 "IO::AIO::FADV_WILLNEED", "IO::AIO::FADV_DONTNEED".
1194
1195 On systems that do not implement "posix_fadvise", this function
1196 returns ENOSYS, otherwise the return value of "posix_fadvise".
1197
1198 IO::AIO::madvise $scalar, $offset, $len, $advice
1199 Simply calls the "posix_madvise" function (see its manpage for
1200 details). The following advice constants are avaiable:
1201 "IO::AIO::MADV_NORMAL", "IO::AIO::MADV_SEQUENTIAL",
1202 "IO::AIO::MADV_RANDOM", "IO::AIO::MADV_WILLNEED",
1203 "IO::AIO::MADV_DONTNEED".
1204
1205 On systems that do not implement "posix_madvise", this function
1206 returns ENOSYS, otherwise the return value of "posix_madvise".
1207
1208 IO::AIO::mprotect $scalar, $offset, $len, $protect
1209 Simply calls the "mprotect" function on the preferably AIO::mmap'ed
1210 $scalar (see its manpage for details). The following protect
1211 constants are avaiable: "IO::AIO::PROT_NONE", "IO::AIO::PROT_READ",
1212 "IO::AIO::PROT_WRITE", "IO::AIO::PROT_EXEC".
1213
1214 On systems that do not implement "mprotect", this function returns
1215 ENOSYS, otherwise the return value of "mprotect".
1216
1217 IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
1218 Memory-maps a file (or anonymous memory range) and attaches it to
1219 the given $scalar, which will act like a string scalar.
1220
1221 The only operations allowed on the scalar are "substr"/"vec" that
1222 don't change the string length, and most read-only operations such
1223 as copying it or searching it with regexes and so on.
1224
1225 Anything else is unsafe and will, at best, result in memory leaks.
1226
1227 The memory map associated with the $scalar is automatically removed
1228 when the $scalar is destroyed, or when the "IO::AIO::mmap" or
1229 "IO::AIO::munmap" functions are called.
1230
1231 This calls the "mmap"(2) function internally. See your system's
1232 manual page for details on the $length, $prot and $flags parameters.
1233
1234 The $length must be larger than zero and smaller than the actual
1235 filesize.
1236
1237 $prot is a combination of "IO::AIO::PROT_NONE",
1238 "IO::AIO::PROT_EXEC", "IO::AIO::PROT_READ" and/or
1239 "IO::AIO::PROT_WRITE",
1240
1241 $flags can be a combination of "IO::AIO::MAP_SHARED" or
1242 "IO::AIO::MAP_PRIVATE", or a number of system-specific flags (when
1243 not available, the are defined as 0): "IO::AIO::MAP_ANONYMOUS"
1244 (which is set to "MAP_ANON" if your system only provides this
1245 constant), "IO::AIO::MAP_HUGETLB", "IO::AIO::MAP_LOCKED",
1246 "IO::AIO::MAP_NORESERVE", "IO::AIO::MAP_POPULATE" or
1247 "IO::AIO::MAP_NONBLOCK"
1248
1249 If $fh is "undef", then a file descriptor of -1 is passed.
1250
1251 $offset is the offset from the start of the file - it generally must
1252 be a multiple of "IO::AIO::PAGESIZE" and defaults to 0.
1253
1254 Example:
1255
1256 use Digest::MD5;
1257 use IO::AIO;
1258
1259 open my $fh, "<verybigfile"
1260 or die "$!";
1261
1262 IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
1263 or die "verybigfile: $!";
1264
1265 my $fast_md5 = md5 $data;
1266
1267 IO::AIO::munmap $scalar
1268 Removes a previous mmap and undefines the $scalar.
1269
1270 IO::AIO::munlock $scalar, $offset = 0, $length = undef
1271 Calls the "munlock" function, undoing the effects of a previous
1272 "aio_mlock" call (see its description for details).
1273
1274 IO::AIO::munlockall
1275 Calls the "munlockall" function.
1276
1277 On systems that do not implement "munlockall", this function returns
1278 ENOSYS, otherwise the return value of "munlockall".
1279
1280EVENT LOOP INTEGRATION
1281 It is recommended to use AnyEvent::AIO to integrate IO::AIO
1282 automatically into many event loops:
1283
1284 # AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
1285 use AnyEvent::AIO;
1286
1287 You can also integrate IO::AIO manually into many event loops, here are
1288 some examples of how to do this:
1289
1290 # EV integration
1291 my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
1292
1293 # Event integration
1294 Event->io (fd => IO::AIO::poll_fileno,
1295 poll => 'r',
1296 cb => \&IO::AIO::poll_cb);
1297
1298 # Glib/Gtk2 integration
1299 add_watch Glib::IO IO::AIO::poll_fileno,
1300 in => sub { IO::AIO::poll_cb; 1 };
1301
1302 # Tk integration
1303 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
1304 readable => \&IO::AIO::poll_cb);
1305
1306 # Danga::Socket integration
1307 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
1308 \&IO::AIO::poll_cb);
838 1309
839 FORK BEHAVIOUR 1310 FORK BEHAVIOUR
840 This module should do "the right thing" when the process using it 1311 This module should do "the right thing" when the process using it forks:
841 forks:
842 1312
843 Before the fork, IO::AIO enters a quiescent state where no requests 1313 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. 1314 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 1315 fork the parent simply leaves the quiescent state and continues
846 continues request/result processing, while the child frees the 1316 request/result processing, while the child frees the request/result
847 request/result queue (so that the requests started before the fork 1317 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 1318 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 1319 the parent process has been reached again.
850 again.
851 1320
852 In short: the parent will, after a short pause, continue as if fork 1321 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 1322 not been called, while the child will act as if IO::AIO has not been
854 been used yet. 1323 used yet.
855 1324
856 MEMORY USAGE 1325 MEMORY USAGE
857 Per-request usage: 1326 Per-request usage:
858 1327
859 Each aio request uses - depending on your architecture - around 1328 Each aio request uses - depending on your architecture - around 100-200
860 100-200 bytes of memory. In addition, stat requests need a stat 1329 bytes of memory. In addition, stat requests need a stat buffer (possibly
861 buffer (possibly a few hundred bytes), readdir requires a result 1330 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 1331 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 1332 will consume memory till the request has entered the done state.
864 request has entered the done state.
865 1333
866 This is now awfully much, so queuing lots of requests is not usually 1334 This is not awfully much, so queuing lots of requests is not usually a
867 a problem. 1335 problem.
868 1336
869 Per-thread usage: 1337 Per-thread usage:
870 1338
871 In the execution phase, some aio requests require more memory for 1339 In the execution phase, some aio requests require more memory for
872 temporary buffers, and each thread requires a stack and other data 1340 temporary buffers, and each thread requires a stack and other data
873 structures (usually around 16k-128k, depending on the OS). 1341 structures (usually around 16k-128k, depending on the OS).
874 1342
875KNOWN BUGS 1343KNOWN BUGS
876 Known bugs will be fixed in the next release. 1344 Known bugs will be fixed in the next release.
877 1345
878SEE ALSO 1346SEE ALSO
879 Coro::AIO. 1347 AnyEvent::AIO for easy integration into event loops, Coro::AIO for a
1348 more natural syntax.
880 1349
881AUTHOR 1350AUTHOR
882 Marc Lehmann <schmorp@schmorp.de> 1351 Marc Lehmann <schmorp@schmorp.de>
883 http://home.schmorp.de/ 1352 http://home.schmorp.de/
884 1353

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