ViewVC Help
View File | Revision Log | Show Annotations | Download File
/cvs/IO-AIO/README
(Generate patch)

Comparing IO-AIO/README (file contents):
Revision 1.19 by root, Sun Oct 29 01:03:13 2006 UTC vs.
Revision 1.47 by root, Fri May 27 00:44:49 2011 UTC

… …
2 IO::AIO - Asynchronous Input/Output 2 IO::AIO - Asynchronous Input/Output
3 3
4SYNOPSIS 4SYNOPSIS
5 use IO::AIO; 5 use IO::AIO;
6 6
7 aio_open "/etc/passwd", O_RDONLY, 0, sub { 7 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
8 my ($fh) = @_; 8 my $fh = shift
9 or die "/etc/passwd: $!";
9 ... 10 ...
10 }; 11 };
11 12
12 aio_unlink "/tmp/file", sub { }; 13 aio_unlink "/tmp/file", sub { };
13 14
… …
23 $req->cancel; # cancel request if still in queue 24 $req->cancel; # cancel request if still in queue
24 25
25 my $grp = aio_group sub { print "all stats done\n" }; 26 my $grp = aio_group sub { print "all stats done\n" };
26 add $grp aio_stat "..." for ...; 27 add $grp aio_stat "..." for ...;
27 28
28 # AnyEvent integration
29 open my $fh, "<&=" . IO::AIO::poll_fileno or die "$!";
30 my $w = AnyEvent->io (fh => $fh, poll => 'r', cb => sub { IO::AIO::poll_cb });
31
32 # Event integration
33 Event->io (fd => IO::AIO::poll_fileno,
34 poll => 'r',
35 cb => \&IO::AIO::poll_cb);
36
37 # Glib/Gtk2 integration
38 add_watch Glib::IO IO::AIO::poll_fileno,
39 in => sub { IO::AIO::poll_cb; 1 };
40
41 # Tk integration
42 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
43 readable => \&IO::AIO::poll_cb);
44
45 # Danga::Socket integration
46 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
47 \&IO::AIO::poll_cb);
48
49DESCRIPTION 29DESCRIPTION
50 This module implements asynchronous I/O using whatever means your 30 This module implements asynchronous I/O using whatever means your
51 operating system supports. 31 operating system supports. It is implemented as an interface to "libeio"
32 (<http://software.schmorp.de/pkg/libeio.html>).
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
… …
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
… …
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
… …
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
… …
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::idle_timeout $seconds
210 IO::AIO::max_outstanding $maxreqs
211 IO::AIO::nreqs
212 IO::AIO::nready
213 IO::AIO::npending
214
215 IO::AIO::sendfile $ofh, $ifh, $offset, $count
216 IO::AIO::fadvise $fh, $offset, $len, $advice
217 IO::AIO::madvise $scalar, $offset, $length, $advice
218 IO::AIO::mprotect $scalar, $offset, $length, $protect
219 IO::AIO::munlock $scalar, $offset = 0, $length = undef
220 IO::AIO::munlockall
221
171 AIO REQUEST FUNCTIONS 222 AIO REQUEST FUNCTIONS
172 All the "aio_*" calls are more or less thin wrappers around the 223 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 224 with the same name (sans "aio_"). The arguments are similar or
174 or identical, and they all accept an additional (and optional) 225 identical, and they all accept an additional (and optional) $callback
175 $callback argument which must be a code reference. This code 226 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 227 called with the syscall return code (e.g. most syscalls return -1 on
177 syscalls return -1 on error, unlike perl, which usually delivers 228 error, unlike perl, which usually delivers "false") as its sole argument
178 "false") as it's sole argument when the given syscall has been 229 after the given syscall has been executed asynchronously.
179 executed asynchronously.
180 230
181 All functions expecting a filehandle keep a copy of the filehandle 231 All functions expecting a filehandle keep a copy of the filehandle
182 internally until the request has finished. 232 internally until the request has finished.
183 233
184 All functions return request objects of type IO::AIO::REQ that allow 234 All functions return request objects of type IO::AIO::REQ that allow
185 further manipulation of those requests while they are in-flight. 235 further manipulation of those requests while they are in-flight.
186 236
187 The pathnames you pass to these routines *must* be absolute and 237 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 238 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 239 being executed, the current working directory could have changed.
190 changed. Alternatively, you can make sure that you never change the 240 Alternatively, you can make sure that you never change the current
191 current working directory anywhere in the program and then use 241 working directory anywhere in the program and then use relative paths.
192 relative paths.
193 242
194 To encode pathnames as octets, either make sure you either: a) 243 To encode pathnames as octets, either make sure you either: a) always
195 always pass in filenames you got from outside (command line, readdir 244 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 245 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) 246 and encode your pathnames to the locale (or other) encoding in effect in
198 encoding in effect in the user environment, d) use 247 the user environment, d) use Glib::filename_from_unicode on unicode
199 Glib::filename_from_unicode on unicode filenames or e) use something 248 filenames or e) use something else to ensure your scalar has the correct
200 else to ensure your scalar has the correct contents. 249 contents.
201 250
202 This works, btw. independent of the internal UTF-8 bit, which 251 This works, btw. independent of the internal UTF-8 bit, which IO::AIO
203 IO::AIO handles correctly wether it is set or not. 252 handles correctly whether it is set or not.
204 253
205 $prev_pri = aioreq_pri [$pri] 254 $prev_pri = aioreq_pri [$pri]
206 Returns the priority value that would be used for the next 255 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 256 and, if $pri is given, sets the priority for the next aio request.
208 aio request.
209 257
210 The default priority is 0, the minimum and maximum priorities 258 The default priority is 0, the minimum and maximum priorities are -4
211 are -4 and 4, respectively. Requests with higher priority will 259 and 4, respectively. Requests with higher priority will be serviced
212 be serviced first. 260 first.
213 261
214 The priority will be reset to 0 after each call to one of the 262 The priority will be reset to 0 after each call to one of the
215 "aio_*" functions. 263 "aio_*" functions.
216 264
217 Example: open a file with low priority, then read something from 265 Example: open a file with low priority, then read something from it
218 it with higher priority so the read request is serviced before 266 with higher priority so the read request is serviced before other
219 other low priority open requests (potentially spamming the 267 low priority open requests (potentially spamming the cache):
220 cache):
221 268
269 aioreq_pri -3;
270 aio_open ..., sub {
271 return unless $_[0];
272
222 aioreq_pri -3; 273 aioreq_pri -2;
223 aio_open ..., sub {
224 return unless $_[0];
225
226 aioreq_pri -2;
227 aio_read $_[0], ..., sub { 274 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 ...; 275 ...
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 }; 276 };
571 }; 277 };
572 278
279 aioreq_nice $pri_adjust
280 Similar to "aioreq_pri", but subtracts the given value from the
281 current priority, so the effect is cumulative.
282
283 aio_open $pathname, $flags, $mode, $callback->($fh)
284 Asynchronously open or create a file and call the callback with a
285 newly created filehandle for the file.
286
287 The pathname passed to "aio_open" must be absolute. See API NOTES,
288 above, for an explanation.
289
290 The $flags argument is a bitmask. See the "Fcntl" module for a list.
291 They are the same as used by "sysopen".
292
293 Likewise, $mode specifies the mode of the newly created file, if it
294 didn't exist and "O_CREAT" has been given, just like perl's
295 "sysopen", except that it is mandatory (i.e. use 0 if you don't
296 create new files, and 0666 or 0777 if you do). Note that the $mode
297 will be modified by the umask in effect then the request is being
298 executed, so better never change the umask.
299
300 Example:
301
302 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
303 if ($_[0]) {
304 print "open successful, fh is $_[0]\n";
305 ...
306 } else {
307 die "open failed: $!\n";
308 }
309 };
310
311 In addition to all the common open modes/flags ("O_RDONLY",
312 "O_WRONLY", "O_RDWR", "O_CREAT", "O_TRUNC", "O_EXCL" and
313 "O_APPEND"), the following POSIX and non-POSIX constants are
314 available (missing ones on your system are, as usual, 0):
315
316 "O_ASYNC", "O_DIRECT", "O_NOATIME", "O_CLOEXEC", "O_NOCTTY",
317 "O_NOFOLLOW", "O_NONBLOCK", "O_EXEC", "O_SEARCH", "O_DIRECTORY",
318 "O_DSYNC", "O_RSYNC", "O_SYNC" and "O_TTY_INIT".
319
320 aio_close $fh, $callback->($status)
321 Asynchronously close a file and call the callback with the result
322 code.
323
324 Unfortunately, you can't do this to perl. Perl *insists* very
325 strongly on closing the file descriptor associated with the
326 filehandle itself.
327
328 Therefore, "aio_close" will not close the filehandle - instead it
329 will use dup2 to overwrite the file descriptor with the write-end of
330 a pipe (the pipe fd will be created on demand and will be cached).
331
332 Or in other words: the file descriptor will be closed, but it will
333 not be free for reuse until the perl filehandle is closed.
334
335 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
336 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
337 Reads or writes $length bytes from or to the specified $fh and
338 $offset into the scalar given by $data and offset $dataoffset and
339 calls the callback without the actual number of bytes read (or -1 on
340 error, just like the syscall).
341
342 "aio_read" will, like "sysread", shrink or grow the $data scalar to
343 offset plus the actual number of bytes read.
344
345 If $offset is undefined, then the current file descriptor offset
346 will be used (and updated), otherwise the file descriptor offset
347 will not be changed by these calls.
348
349 If $length is undefined in "aio_write", use the remaining length of
350 $data.
351
352 If $dataoffset is less than zero, it will be counted from the end of
353 $data.
354
355 The $data scalar *MUST NOT* be modified in any way while the request
356 is outstanding. Modifying it can result in segfaults or World War
357 III (if the necessary/optional hardware is installed).
358
359 Example: Read 15 bytes at offset 7 into scalar $buffer, starting at
360 offset 0 within the scalar:
361
362 aio_read $fh, 7, 15, $buffer, 0, sub {
363 $_[0] > 0 or die "read error: $!";
364 print "read $_[0] bytes: <$buffer>\n";
365 };
366
367 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
368 Tries to copy $length bytes from $in_fh to $out_fh. It starts
369 reading at byte offset $in_offset, and starts writing at the current
370 file offset of $out_fh. Because of that, it is not safe to issue
371 more than one "aio_sendfile" per $out_fh, as they will interfere
372 with each other.
373
374 Please note that "aio_sendfile" can read more bytes from $in_fh than
375 are written, and there is no way to find out how many bytes have
376 been read from "aio_sendfile" alone, as "aio_sendfile" only provides
377 the number of bytes written to $out_fh. Only if the result value
378 equals $length one can assume that $length bytes have been read.
379
380 Unlike with other "aio_" functions, it makes a lot of sense to use
381 "aio_sendfile" on non-blocking sockets, as long as one end
382 (typically the $in_fh) is a file - the file I/O will then be
383 asynchronous, while the socket I/O will be non-blocking. Note,
384 however, that you can run into a trap where "aio_sendfile" reads
385 some data with readahead, then fails to write all data, and when the
386 socket is ready the next time, the data in the cache is already
387 lost, forcing "aio_sendfile" to again hit the disk. Explicit
388 "aio_read" + "aio_write" let's you control resource usage much
389 better.
390
391 This call tries to make use of a native "sendfile" syscall to
392 provide zero-copy operation. For this to work, $out_fh should refer
393 to a socket, and $in_fh should refer to an mmap'able file.
394
395 If a native sendfile cannot be found or it fails with "ENOSYS",
396 "ENOTSUP", "EOPNOTSUPP", "EAFNOSUPPORT", "EPROTOTYPE" or "ENOTSOCK",
397 it will be emulated, so you can call "aio_sendfile" on any type of
398 filehandle regardless of the limitations of the operating system.
399
400 aio_readahead $fh,$offset,$length, $callback->($retval)
401 "aio_readahead" populates the page cache with data from a file so
402 that subsequent reads from that file will not block on disk I/O. The
403 $offset argument specifies the starting point from which data is to
404 be read and $length specifies the number of bytes to be read. I/O is
405 performed in whole pages, so that offset is effectively rounded down
406 to a page boundary and bytes are read up to the next page boundary
407 greater than or equal to (off-set+length). "aio_readahead" does not
408 read beyond the end of the file. The current file offset of the file
409 is left unchanged.
410
411 If that syscall doesn't exist (likely if your OS isn't Linux) it
412 will be emulated by simply reading the data, which would have a
413 similar effect.
414
415 aio_stat $fh_or_path, $callback->($status)
416 aio_lstat $fh, $callback->($status)
417 Works like perl's "stat" or "lstat" in void context. The callback
418 will be called after the stat and the results will be available
419 using "stat _" or "-s _" etc...
420
421 The pathname passed to "aio_stat" must be absolute. See API NOTES,
422 above, for an explanation.
423
424 Currently, the stats are always 64-bit-stats, i.e. instead of
425 returning an error when stat'ing a large file, the results will be
426 silently truncated unless perl itself is compiled with large file
427 support.
428
429 To help interpret the mode and dev/rdev stat values, IO::AIO offers
430 the following constants and functions (if not implemented, the
431 constants will be 0 and the functions will either "croak" or fall
432 back on traditional behaviour).
433
434 "S_IFMT", "S_IFIFO", "S_IFCHR", "S_IFBLK", "S_IFLNK", "S_IFREG",
435 "S_IFDIR", "S_IFWHT", "S_IFSOCK", "IO::AIO::major $dev_t",
436 "IO::AIO::minor $dev_t", "IO::AIO::makedev $major, $minor".
437
438 Example: Print the length of /etc/passwd:
439
440 aio_stat "/etc/passwd", sub {
441 $_[0] and die "stat failed: $!";
442 print "size is ", -s _, "\n";
443 };
444
445 aio_statvfs $fh_or_path, $callback->($statvfs)
446 Works like the POSIX "statvfs" or "fstatvfs" syscalls, depending on
447 whether a file handle or path was passed.
448
449 On success, the callback is passed a hash reference with the
450 following members: "bsize", "frsize", "blocks", "bfree", "bavail",
451 "files", "ffree", "favail", "fsid", "flag" and "namemax". On
452 failure, "undef" is passed.
453
454 The following POSIX IO::AIO::ST_* constants are defined: "ST_RDONLY"
455 and "ST_NOSUID".
456
457 The following non-POSIX IO::AIO::ST_* flag masks are defined to
458 their correct value when available, or to 0 on systems that do not
459 support them: "ST_NODEV", "ST_NOEXEC", "ST_SYNCHRONOUS",
460 "ST_MANDLOCK", "ST_WRITE", "ST_APPEND", "ST_IMMUTABLE",
461 "ST_NOATIME", "ST_NODIRATIME" and "ST_RELATIME".
462
463 Example: stat "/wd" and dump out the data if successful.
464
465 aio_statvfs "/wd", sub {
466 my $f = $_[0]
467 or die "statvfs: $!";
468
469 use Data::Dumper;
470 say Dumper $f;
471 };
472
473 # result:
474 {
475 bsize => 1024,
476 bfree => 4333064312,
477 blocks => 10253828096,
478 files => 2050765568,
479 flag => 4096,
480 favail => 2042092649,
481 bavail => 4333064312,
482 ffree => 2042092649,
483 namemax => 255,
484 frsize => 1024,
485 fsid => 1810
486 }
487
488 aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
489 Works like perl's "utime" function (including the special case of
490 $atime and $mtime being undef). Fractional times are supported if
491 the underlying syscalls support them.
492
493 When called with a pathname, uses utimes(2) if available, otherwise
494 utime(2). If called on a file descriptor, uses futimes(2) if
495 available, otherwise returns ENOSYS, so this is not portable.
496
497 Examples:
498
499 # set atime and mtime to current time (basically touch(1)):
500 aio_utime "path", undef, undef;
501 # set atime to current time and mtime to beginning of the epoch:
502 aio_utime "path", time, undef; # undef==0
503
504 aio_chown $fh_or_path, $uid, $gid, $callback->($status)
505 Works like perl's "chown" function, except that "undef" for either
506 $uid or $gid is being interpreted as "do not change" (but -1 can
507 also be used).
508
509 Examples:
510
511 # same as "chown root path" in the shell:
512 aio_chown "path", 0, -1;
513 # same as above:
514 aio_chown "path", 0, undef;
515
516 aio_truncate $fh_or_path, $offset, $callback->($status)
517 Works like truncate(2) or ftruncate(2).
518
519 aio_chmod $fh_or_path, $mode, $callback->($status)
520 Works like perl's "chmod" function.
521
522 aio_unlink $pathname, $callback->($status)
523 Asynchronously unlink (delete) a file and call the callback with the
524 result code.
525
526 aio_mknod $path, $mode, $dev, $callback->($status)
527 [EXPERIMENTAL]
528
529 Asynchronously create a device node (or fifo). See mknod(2).
530
531 The only (POSIX-) portable way of calling this function is:
532
533 aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...
534
535 See "aio_stat" for info about some potentially helpful extra
536 constants and functions.
537
538 aio_link $srcpath, $dstpath, $callback->($status)
539 Asynchronously create a new link to the existing object at $srcpath
540 at the path $dstpath and call the callback with the result code.
541
542 aio_symlink $srcpath, $dstpath, $callback->($status)
543 Asynchronously create a new symbolic link to the existing object at
544 $srcpath at the path $dstpath and call the callback with the result
545 code.
546
547 aio_readlink $path, $callback->($link)
548 Asynchronously read the symlink specified by $path and pass it to
549 the callback. If an error occurs, nothing or undef gets passed to
550 the callback.
551
552 aio_rename $srcpath, $dstpath, $callback->($status)
553 Asynchronously rename the object at $srcpath to $dstpath, just as
554 rename(2) and call the callback with the result code.
555
556 aio_mkdir $pathname, $mode, $callback->($status)
557 Asynchronously mkdir (create) a directory and call the callback with
558 the result code. $mode will be modified by the umask at the time the
559 request is executed, so do not change your umask.
560
561 aio_rmdir $pathname, $callback->($status)
562 Asynchronously rmdir (delete) a directory and call the callback with
563 the result code.
564
565 aio_readdir $pathname, $callback->($entries)
566 Unlike the POSIX call of the same name, "aio_readdir" reads an
567 entire directory (i.e. opendir + readdir + closedir). The entries
568 will not be sorted, and will NOT include the "." and ".." entries.
569
570 The callback is passed a single argument which is either "undef" or
571 an array-ref with the filenames.
572
573 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
574 Quite similar to "aio_readdir", but the $flags argument allows to
575 tune behaviour and output format. In case of an error, $entries will
576 be "undef".
577
578 The flags are a combination of the following constants, ORed
579 together (the flags will also be passed to the callback, possibly
580 modified):
581
582 IO::AIO::READDIR_DENTS
583 When this flag is off, then the callback gets an arrayref
584 consisting of names only (as with "aio_readdir"), otherwise it
585 gets an arrayref with "[$name, $type, $inode]" arrayrefs, each
586 describing a single directory entry in more detail.
587
588 $name is the name of the entry.
589
590 $type is one of the "IO::AIO::DT_xxx" constants:
591
592 "IO::AIO::DT_UNKNOWN", "IO::AIO::DT_FIFO", "IO::AIO::DT_CHR",
593 "IO::AIO::DT_DIR", "IO::AIO::DT_BLK", "IO::AIO::DT_REG",
594 "IO::AIO::DT_LNK", "IO::AIO::DT_SOCK", "IO::AIO::DT_WHT".
595
596 "IO::AIO::DT_UNKNOWN" means just that: readdir does not know. If
597 you need to know, you have to run stat yourself. Also, for speed
598 reasons, the $type scalars are read-only: you can not modify
599 them.
600
601 $inode is the inode number (which might not be exact on systems
602 with 64 bit inode numbers and 32 bit perls). This field has
603 unspecified content on systems that do not deliver the inode
604 information.
605
606 IO::AIO::READDIR_DIRS_FIRST
607 When this flag is set, then the names will be returned in an
608 order where likely directories come first, in optimal stat
609 order. This is useful when you need to quickly find directories,
610 or you want to find all directories while avoiding to stat()
611 each entry.
612
613 If the system returns type information in readdir, then this is
614 used to find directories directly. Otherwise, likely directories
615 are names beginning with ".", or otherwise names with no dots,
616 of which names with short names are tried first.
617
618 IO::AIO::READDIR_STAT_ORDER
619 When this flag is set, then the names will be returned in an
620 order suitable for stat()'ing each one. That is, when you plan
621 to stat() all files in the given directory, then the returned
622 order will likely be fastest.
623
624 If both this flag and "IO::AIO::READDIR_DIRS_FIRST" are
625 specified, then the likely dirs come first, resulting in a less
626 optimal stat order.
627
628 IO::AIO::READDIR_FOUND_UNKNOWN
629 This flag should not be set when calling "aio_readdirx".
630 Instead, it is being set by "aio_readdirx", when any of the
631 $type's found were "IO::AIO::DT_UNKNOWN". The absense of this
632 flag therefore indicates that all $type's are known, which can
633 be used to speed up some algorithms.
634
635 aio_load $path, $data, $callback->($status)
636 This is a composite request that tries to fully load the given file
637 into memory. Status is the same as with aio_read.
638
639 aio_copy $srcpath, $dstpath, $callback->($status)
640 Try to copy the *file* (directories not supported as either source
641 or destination) from $srcpath to $dstpath and call the callback with
642 a status of 0 (ok) or -1 (error, see $!).
643
644 This is a composite request that creates the destination file with
645 mode 0200 and copies the contents of the source file into it using
646 "aio_sendfile", followed by restoring atime, mtime, access mode and
647 uid/gid, in that order.
648
649 If an error occurs, the partial destination file will be unlinked,
650 if possible, except when setting atime, mtime, access mode and
651 uid/gid, where errors are being ignored.
652
653 aio_move $srcpath, $dstpath, $callback->($status)
654 Try to move the *file* (directories not supported as either source
655 or destination) from $srcpath to $dstpath and call the callback with
656 a status of 0 (ok) or -1 (error, see $!).
657
658 This is a composite request that tries to rename(2) the file first;
659 if rename fails with "EXDEV", it copies the file with "aio_copy"
660 and, if that is successful, unlinks the $srcpath.
661
662 aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
663 Scans a directory (similar to "aio_readdir") but additionally tries
664 to efficiently separate the entries of directory $path into two sets
665 of names, directories you can recurse into (directories), and ones
666 you cannot recurse into (everything else, including symlinks to
667 directories).
668
669 "aio_scandir" is a composite request that creates of many sub
670 requests_ $maxreq specifies the maximum number of outstanding aio
671 requests that this function generates. If it is "<= 0", then a
672 suitable default will be chosen (currently 4).
673
674 On error, the callback is called without arguments, otherwise it
675 receives two array-refs with path-relative entry names.
676
677 Example:
678
679 aio_scandir $dir, 0, sub {
680 my ($dirs, $nondirs) = @_;
681 print "real directories: @$dirs\n";
682 print "everything else: @$nondirs\n";
683 };
684
685 Implementation notes.
686
687 The "aio_readdir" cannot be avoided, but "stat()"'ing every entry
688 can.
689
690 If readdir returns file type information, then this is used directly
691 to find directories.
692
693 Otherwise, after reading the directory, the modification time, size
694 etc. of the directory before and after the readdir is checked, and
695 if they match (and isn't the current time), the link count will be
696 used to decide how many entries are directories (if >= 2).
697 Otherwise, no knowledge of the number of subdirectories will be
698 assumed.
699
700 Then entries will be sorted into likely directories a non-initial
701 dot currently) and likely non-directories (see "aio_readdirx"). Then
702 every entry plus an appended "/." will be "stat"'ed, likely
703 directories first, in order of their inode numbers. If that
704 succeeds, it assumes that the entry is a directory or a symlink to
705 directory (which will be checked seperately). This is often faster
706 than stat'ing the entry itself because filesystems might detect the
707 type of the entry without reading the inode data (e.g. ext2fs
708 filetype feature), even on systems that cannot return the filetype
709 information on readdir.
710
711 If the known number of directories (link count - 2) has been
712 reached, the rest of the entries is assumed to be non-directories.
713
714 This only works with certainty on POSIX (= UNIX) filesystems, which
715 fortunately are the vast majority of filesystems around.
716
717 It will also likely work on non-POSIX filesystems with reduced
718 efficiency as those tend to return 0 or 1 as link counts, which
719 disables the directory counting heuristic.
720
721 aio_rmtree $path, $callback->($status)
722 Delete a directory tree starting (and including) $path, return the
723 status of the final "rmdir" only. This is a composite request that
724 uses "aio_scandir" to recurse into and rmdir directories, and unlink
725 everything else.
726
727 aio_sync $callback->($status)
728 Asynchronously call sync and call the callback when finished.
729
730 aio_fsync $fh, $callback->($status)
731 Asynchronously call fsync on the given filehandle and call the
732 callback with the fsync result code.
733
734 aio_fdatasync $fh, $callback->($status)
735 Asynchronously call fdatasync on the given filehandle and call the
736 callback with the fdatasync result code.
737
738 If this call isn't available because your OS lacks it or it couldn't
739 be detected, it will be emulated by calling "fsync" instead.
740
741 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
742 Sync the data portion of the file specified by $offset and $length
743 to disk (but NOT the metadata), by calling the Linux-specific
744 sync_file_range call. If sync_file_range is not available or it
745 returns ENOSYS, then fdatasync or fsync is being substituted.
746
747 $flags can be a combination of
748 "IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE",
749 "IO::AIO::SYNC_FILE_RANGE_WRITE" and
750 "IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER": refer to the sync_file_range
751 manpage for details.
752
753 aio_pathsync $path, $callback->($status)
754 This request tries to open, fsync and close the given path. This is
755 a composite request intended to sync directories after directory
756 operations (E.g. rename). This might not work on all operating
757 systems or have any specific effect, but usually it makes sure that
758 directory changes get written to disc. It works for anything that
759 can be opened for read-only, not just directories.
760
761 Future versions of this function might fall back to other methods
762 when "fsync" on the directory fails (such as calling "sync").
763
764 Passes 0 when everything went ok, and -1 on error.
765
766 aio_msync $scalar, $offset = 0, $length = undef, flags = 0,
767 $callback->($status)
768 This is a rather advanced IO::AIO call, which only works on
769 mmap(2)ed scalars (see the "IO::AIO::mmap" function, although it
770 also works on data scalars managed by the Sys::Mmap or Mmap modules,
771 note that the scalar must only be modified in-place while an aio
772 operation is pending on it).
773
774 It calls the "msync" function of your OS, if available, with the
775 memory area starting at $offset in the string and ending $length
776 bytes later. If $length is negative, counts from the end, and if
777 $length is "undef", then it goes till the end of the string. The
778 flags can be a combination of "IO::AIO::MS_ASYNC",
779 "IO::AIO::MS_INVALIDATE" and "IO::AIO::MS_SYNC".
780
781 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0,
782 $callback->($status)
783 This is a rather advanced IO::AIO call, which works best on
784 mmap(2)ed scalars.
785
786 It touches (reads or writes) all memory pages in the specified range
787 inside the scalar. All caveats and parameters are the same as for
788 "aio_msync", above, except for flags, which must be either 0 (which
789 reads all pages and ensures they are instantiated) or
790 "IO::AIO::MT_MODIFY", which modifies the memory page s(by reading
791 and writing an octet from it, which dirties the page).
792
793 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
794 This is a rather advanced IO::AIO call, which works best on
795 mmap(2)ed scalars.
796
797 It reads in all the pages of the underlying storage into memory (if
798 any) and locks them, so they are not getting swapped/paged out or
799 removed.
800
801 If $length is undefined, then the scalar will be locked till the
802 end.
803
804 On systems that do not implement "mlock", this function returns -1
805 and sets errno to "ENOSYS".
806
807 Note that the corresponding "munlock" is synchronous and is
808 documented under "MISCELLANEOUS FUNCTIONS".
809
810 Example: open a file, mmap and mlock it - both will be undone when
811 $data gets destroyed.
812
813 open my $fh, "<", $path or die "$path: $!";
814 my $data;
815 IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
816 aio_mlock $data; # mlock in background
817
818 aio_mlockall $flags, $callback->($status)
819 Calls the "mlockall" function with the given $flags (a combination
820 of "IO::AIO::MCL_CURRENT" and "IO::AIO::MCL_FUTURE").
821
822 On systems that do not implement "mlockall", this function returns
823 -1 and sets errno to "ENOSYS".
824
825 Note that the corresponding "munlockall" is synchronous and is
826 documented under "MISCELLANEOUS FUNCTIONS".
827
828 Example: asynchronously lock all current and future pages into
829 memory.
830
831 aio_mlockall IO::AIO::MCL_FUTURE;
832
833 aio_group $callback->(...)
834 This is a very special aio request: Instead of doing something, it
835 is a container for other aio requests, which is useful if you want
836 to bundle many requests into a single, composite, request with a
837 definite callback and the ability to cancel the whole request with
838 its subrequests.
839
840 Returns an object of class IO::AIO::GRP. See its documentation below
841 for more info.
842
843 Example:
844
845 my $grp = aio_group sub {
846 print "all stats done\n";
847 };
848
849 add $grp
850 (aio_stat ...),
851 (aio_stat ...),
852 ...;
853
854 aio_nop $callback->()
855 This is a special request - it does nothing in itself and is only
856 used for side effects, such as when you want to add a dummy request
857 to a group so that finishing the requests in the group depends on
858 executing the given code.
859
860 While this request does nothing, it still goes through the execution
861 phase and still requires a worker thread. Thus, the callback will
862 not be executed immediately but only after other requests in the
863 queue have entered their execution phase. This can be used to
864 measure request latency.
865
866 IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
867 Mainly used for debugging and benchmarking, this aio request puts
868 one of the request workers to sleep for the given time.
869
870 While it is theoretically handy to have simple I/O scheduling
871 requests like sleep and file handle readable/writable, the overhead
872 this creates is immense (it blocks a thread for a long time) so do
873 not use this function except to put your application under
874 artificial I/O pressure.
875
876 IO::AIO::REQ CLASS
877 All non-aggregate "aio_*" functions return an object of this class when
878 called in non-void context.
879
880 cancel $req
881 Cancels the request, if possible. Has the effect of skipping
882 execution when entering the execute state and skipping calling the
883 callback when entering the the result state, but will leave the
884 request otherwise untouched (with the exception of readdir). That
885 means that requests that currently execute will not be stopped and
886 resources held by the request will not be freed prematurely.
887
888 cb $req $callback->(...)
889 Replace (or simply set) the callback registered to the request.
890
891 IO::AIO::GRP CLASS
892 This class is a subclass of IO::AIO::REQ, so all its methods apply to
893 objects of this class, too.
894
895 A IO::AIO::GRP object is a special request that can contain multiple
896 other aio requests.
897
898 You create one by calling the "aio_group" constructing function with a
899 callback that will be called when all contained requests have entered
900 the "done" state:
901
902 my $grp = aio_group sub {
903 print "all requests are done\n";
904 };
905
906 You add requests by calling the "add" method with one or more
907 "IO::AIO::REQ" objects:
908
909 $grp->add (aio_unlink "...");
910
911 add $grp aio_stat "...", sub {
912 $_[0] or return $grp->result ("error");
913
914 # add another request dynamically, if first succeeded
915 add $grp aio_open "...", sub {
916 $grp->result ("ok");
917 };
918 };
919
573 This makes it very easy to create composite requests (see the source 920 This makes it very easy to create composite requests (see the source of
574 of "aio_move" for an application) that work and feel like simple 921 "aio_move" for an application) that work and feel like simple requests.
575 requests.
576 922
577 * The IO::AIO::GRP objects will be cleaned up during calls to 923 * The IO::AIO::GRP objects will be cleaned up during calls to
578 "IO::AIO::poll_cb", just like any other request. 924 "IO::AIO::poll_cb", just like any other request.
925
579 * They can be canceled like any other request. Canceling will cancel 926 * They can be canceled like any other request. Canceling will cancel
580 not only the request itself, but also all requests it contains. 927 not only the request itself, but also all requests it contains.
928
581 * They can also can also be added to other IO::AIO::GRP objects. 929 * They can also can also be added to other IO::AIO::GRP objects.
930
582 * You must not add requests to a group from within the group 931 * You must not add requests to a group from within the group callback
583 callback (or any later time). 932 (or any later time).
584 933
585 Their lifetime, simplified, looks like this: when they are empty, 934 Their lifetime, simplified, looks like this: when they are empty, they
586 they will finish very quickly. If they contain only requests that 935 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 936 "done" state, they will also finish. Otherwise they will continue to
588 continue to exist. 937 exist.
589 938
590 That means after creating a group you have some time to add 939 That means after creating a group you have some time to add requests
940 (precisely before the callback has been invoked, which is only done
591 requests. And in the callbacks of those requests, you can add 941 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 942 add further requests to the group. And only when all those requests have
593 finished will the the group itself finish. 943 finished will the the group itself finish.
594 944
595 add $grp ... 945 add $grp ...
596 $grp->add (...) 946 $grp->add (...)
597 Add one or more requests to the group. Any type of IO::AIO::REQ 947 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 948 be added, including other groups, as long as you do not create
599 create circular dependencies. 949 circular dependencies.
600 950
601 Returns all its arguments. 951 Returns all its arguments.
602 952
603 $grp->cancel_subs 953 $grp->cancel_subs
604 Cancel all subrequests and clears any feeder, but not the group 954 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 955 request itself. Useful when you queued a lot of events but got a
606 result early. 956 result early.
607 957
958 The group request will finish normally (you cannot add requests to
959 the group).
960
608 $grp->result (...) 961 $grp->result (...)
609 Set the result value(s) that will be passed to the group 962 Set the result value(s) that will be passed to the group callback
610 callback when all subrequests have finished and set thre groups 963 when all subrequests have finished and set the groups errno to the
611 errno to the current value of errno (just like calling "errno" 964 current value of errno (just like calling "errno" without an error
612 without an error number). By default, no argument will be passed 965 number). By default, no argument will be passed and errno is zero.
613 and errno is zero.
614 966
615 $grp->errno ([$errno]) 967 $grp->errno ([$errno])
616 Sets the group errno value to $errno, or the current value of 968 Sets the group errno value to $errno, or the current value of errno
617 errno when the argument is missing. 969 when the argument is missing.
618 970
619 Every aio request has an associated errno value that is restored 971 Every aio request has an associated errno value that is restored
620 when the callback is invoked. This method lets you change this 972 when the callback is invoked. This method lets you change this value
621 value from its default (0). 973 from its default (0).
622 974
623 Calling "result" will also set errno, so make sure you either 975 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. 976 before the call to "result", or call c<errno> after it.
625 977
626 feed $grp $callback->($grp) 978 feed $grp $callback->($grp)
627 Sets a feeder/generator on this group: every group can have an 979 Sets a feeder/generator on this group: every group can have an
628 attached generator that generates requests if idle. The idea 980 attached generator that generates requests if idle. The idea behind
629 behind this is that, although you could just queue as many 981 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 982 want in a group, this might starve other requests for a potentially
631 requests for a potentially long time. For example, "aio_scandir" 983 long time. For example, "aio_scandir" might generate hundreds of
632 might generate hundreds of thousands "aio_stat" requests, 984 thousands "aio_stat" requests, delaying any later requests for a
633 delaying any later requests for a long time. 985 long time.
634 986
635 To avoid this, and allow incremental generation of requests, you 987 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 988 instead a group and set a feeder on it that generates those
637 requests. The feed callback will be called whenever there are 989 requests. The feed callback will be called whenever there are few
638 few enough (see "limit", below) requests active in the group 990 enough (see "limit", below) requests active in the group itself and
639 itself and is expected to queue more requests. 991 is expected to queue more requests.
640 992
641 The feed callback can queue as many requests as it likes (i.e. 993 The feed callback can queue as many requests as it likes (i.e. "add"
642 "add" does not impose any limits). 994 does not impose any limits).
643 995
644 If the feed does not queue more requests when called, it will be 996 If the feed does not queue more requests when called, it will be
645 automatically removed from the group. 997 automatically removed from the group.
646 998
647 If the feed limit is 0, it will be set to 2 automatically. 999 If the feed limit is 0 when this method is called, it will be set to
1000 2 automatically.
648 1001
649 Example: 1002 Example:
650 1003
651 # stat all files in @files, but only ever use four aio requests concurrently: 1004 # stat all files in @files, but only ever use four aio requests concurrently:
652 1005
653 my $grp = aio_group sub { print "finished\n" }; 1006 my $grp = aio_group sub { print "finished\n" };
654 limit $grp 4; 1007 limit $grp 4;
655 feed $grp sub { 1008 feed $grp sub {
656 my $file = pop @files 1009 my $file = pop @files
657 or return; 1010 or return;
658 1011
659 add $grp aio_stat $file, sub { ... }; 1012 add $grp aio_stat $file, sub { ... };
660 }; 1013 };
661 1014
662 limit $grp $num 1015 limit $grp $num
663 Sets the feeder limit for the group: The feeder will be called 1016 Sets the feeder limit for the group: The feeder will be called
664 whenever the group contains less than this many requests. 1017 whenever the group contains less than this many requests.
665 1018
666 Setting the limit to 0 will pause the feeding process. 1019 Setting the limit to 0 will pause the feeding process.
1020
1021 The default value for the limit is 0, but note that setting a feeder
1022 automatically bumps it up to 2.
667 1023
668 SUPPORT FUNCTIONS 1024 SUPPORT FUNCTIONS
669 EVENT PROCESSING AND EVENT LOOP INTEGRATION 1025 EVENT PROCESSING AND EVENT LOOP INTEGRATION
670 $fileno = IO::AIO::poll_fileno 1026 $fileno = IO::AIO::poll_fileno
671 Return the *request result pipe file descriptor*. This 1027 Return the *request result pipe file descriptor*. This filehandle
672 filehandle must be polled for reading by some mechanism outside 1028 must be polled for reading by some mechanism outside this module
673 this module (e.g. Event or select, see below or the SYNOPSIS). 1029 (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 1030 pipe becomes readable you have to call "poll_cb" to check the
675 the results. 1031 results.
676 1032
677 See "poll_cb" for an example. 1033 See "poll_cb" for an example.
678 1034
679 IO::AIO::poll_cb 1035 IO::AIO::poll_cb
680 Process some outstanding events on the result pipe. You have to 1036 Process some outstanding events on the result pipe. You have to call
681 call this regularly. Returns the number of events processed. 1037 this regularly. Returns 0 if all events could be processed (or there
1038 were no events to process), or -1 if it returned earlier for
682 Returns immediately when no events are outstanding. The amount 1039 whatever reason. Returns immediately when no events are outstanding.
683 of events processed depends on the settings of 1040 The amount of events processed depends on the settings of
684 "IO::AIO::max_poll_req" and "IO::AIO::max_poll_time". 1041 "IO::AIO::max_poll_req" and "IO::AIO::max_poll_time".
685 1042
686 If not all requests were processed for whatever reason, the 1043 If not all requests were processed for whatever reason, the
687 filehandle will still be ready when "poll_cb" returns. 1044 filehandle will still be ready when "poll_cb" returns, so normally
1045 you don't have to do anything special to have it called later.
688 1046
1047 Apart from calling "IO::AIO::poll_cb" when the event filehandle
1048 becomes ready, it can be beneficial to call this function from loops
1049 which submit a lot of requests, to make sure the results get
1050 processed when they become available and not just when the loop is
1051 finished and the event loop takes over again. This function returns
1052 very fast when there are no outstanding requests.
1053
689 Example: Install an Event watcher that automatically calls 1054 Example: Install an Event watcher that automatically calls
690 IO::AIO::poll_cb with high priority: 1055 IO::AIO::poll_cb with high priority (more examples can be found in
1056 the SYNOPSIS section, at the top of this document):
691 1057
692 Event->io (fd => IO::AIO::poll_fileno, 1058 Event->io (fd => IO::AIO::poll_fileno,
693 poll => 'r', async => 1, 1059 poll => 'r', async => 1,
694 cb => \&IO::AIO::poll_cb); 1060 cb => \&IO::AIO::poll_cb);
695 1061
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 1062 IO::AIO::poll_wait
1063 If there are any outstanding requests and none of them in the result
725 Wait till the result filehandle becomes ready for reading 1064 phase, wait till the result filehandle becomes ready for reading
726 (simply does a "select" on the filehandle. This is useful if you 1065 (simply does a "select" on the filehandle. This is useful if you
727 want to synchronously wait for some requests to finish). 1066 want to synchronously wait for some requests to finish).
728 1067
729 See "nreqs" for an example. 1068 See "nreqs" for an example.
730 1069
731 IO::AIO::poll 1070 IO::AIO::poll
732 Waits until some requests have been handled. 1071 Waits until some requests have been handled.
733 1072
1073 Returns the number of requests processed, but is otherwise strictly
734 Strictly equivalent to: 1074 equivalent to:
735 1075
736 IO::AIO::poll_wait, IO::AIO::poll_cb 1076 IO::AIO::poll_wait, IO::AIO::poll_cb
737 if IO::AIO::nreqs;
738 1077
739 IO::AIO::flush 1078 IO::AIO::flush
740 Wait till all outstanding AIO requests have been handled. 1079 Wait till all outstanding AIO requests have been handled.
741 1080
742 Strictly equivalent to: 1081 Strictly equivalent to:
743 1082
744 IO::AIO::poll_wait, IO::AIO::poll_cb 1083 IO::AIO::poll_wait, IO::AIO::poll_cb
745 while IO::AIO::nreqs; 1084 while IO::AIO::nreqs;
1085
1086 IO::AIO::max_poll_reqs $nreqs
1087 IO::AIO::max_poll_time $seconds
1088 These set the maximum number of requests (default 0, meaning
1089 infinity) that are being processed by "IO::AIO::poll_cb" in one
1090 call, respectively the maximum amount of time (default 0, meaning
1091 infinity) spent in "IO::AIO::poll_cb" to process requests (more
1092 correctly the mininum amount of time "poll_cb" is allowed to use).
1093
1094 Setting "max_poll_time" to a non-zero value creates an overhead of
1095 one syscall per request processed, which is not normally a problem
1096 unless your callbacks are really really fast or your OS is really
1097 really slow (I am not mentioning Solaris here). Using
1098 "max_poll_reqs" incurs no overhead.
1099
1100 Setting these is useful if you want to ensure some level of
1101 interactiveness when perl is not fast enough to process all requests
1102 in time.
1103
1104 For interactive programs, values such as 0.01 to 0.1 should be fine.
1105
1106 Example: Install an Event watcher that automatically calls
1107 IO::AIO::poll_cb with low priority, to ensure that other parts of
1108 the program get the CPU sometimes even under high AIO load.
1109
1110 # try not to spend much more than 0.1s in poll_cb
1111 IO::AIO::max_poll_time 0.1;
1112
1113 # use a low priority so other tasks have priority
1114 Event->io (fd => IO::AIO::poll_fileno,
1115 poll => 'r', nice => 1,
1116 cb => &IO::AIO::poll_cb);
746 1117
747 CONTROLLING THE NUMBER OF THREADS 1118 CONTROLLING THE NUMBER OF THREADS
748 IO::AIO::min_parallel $nthreads 1119 IO::AIO::min_parallel $nthreads
749 Set the minimum number of AIO threads to $nthreads. The current 1120 Set the minimum number of AIO threads to $nthreads. The current
750 default is 8, which means eight asynchronous operations can 1121 default is 8, which means eight asynchronous operations can execute
751 execute concurrently at any one time (the number of outstanding 1122 concurrently at any one time (the number of outstanding requests,
752 requests, however, is unlimited). 1123 however, is unlimited).
753 1124
754 IO::AIO starts threads only on demand, when an AIO request is 1125 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 1126 and no free thread exists. Please note that queueing up a hundred
756 hundred requests can create demand for a hundred threads, even 1127 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 1128 out that everything is in the cache and could have been processed
758 been processed faster by a single thread. 1129 faster by a single thread.
759 1130
760 It is recommended to keep the number of threads relatively low, 1131 It is recommended to keep the number of threads relatively low, as
761 as some Linux kernel versions will scale negatively with the 1132 some Linux kernel versions will scale negatively with the number of
762 number of threads (higher parallelity => MUCH higher latency). 1133 threads (higher parallelity => MUCH higher latency). With current
763 With current Linux 2.6 versions, 4-32 threads should be fine. 1134 Linux 2.6 versions, 4-32 threads should be fine.
764 1135
765 Under most circumstances you don't need to call this function, 1136 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 1137 the module selects a default that is suitable for low to moderate
767 moderate load. 1138 load.
768 1139
769 IO::AIO::max_parallel $nthreads 1140 IO::AIO::max_parallel $nthreads
770 Sets the maximum number of AIO threads to $nthreads. If more 1141 Sets the maximum number of AIO threads to $nthreads. If more than
771 than the specified number of threads are currently running, this 1142 the specified number of threads are currently running, this function
772 function kills them. This function blocks until the limit is 1143 kills them. This function blocks until the limit is reached.
773 reached.
774 1144
775 While $nthreads are zero, aio requests get queued but not 1145 While $nthreads are zero, aio requests get queued but not executed
776 executed until the number of threads has been increased again. 1146 until the number of threads has been increased again.
777 1147
778 This module automatically runs "max_parallel 0" at program end, 1148 This module automatically runs "max_parallel 0" at program end, to
779 to ensure that all threads are killed and that there are no 1149 ensure that all threads are killed and that there are no outstanding
780 outstanding requests. 1150 requests.
781 1151
782 Under normal circumstances you don't need to call this function. 1152 Under normal circumstances you don't need to call this function.
783 1153
784 IO::AIO::max_idle $nthreads 1154 IO::AIO::max_idle $nthreads
785 Limit the number of threads (default: 4) that are allowed to 1155 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 1156 (i.e., threads that did not get a request to process within the idle
787 10 seconds). That means if a thread becomes idle while $nthreads 1157 timeout (default: 10 seconds). That means if a thread becomes idle
788 other threads are also idle, it will free its resources and 1158 while $nthreads other threads are also idle, it will free its
789 exit. 1159 resources and exit.
790 1160
791 This is useful when you allow a large number of threads (e.g. 1161 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 1162 1000) to allow for extremely high load situations, but want to free
793 want to free resources under normal circumstances (1000 threads 1163 resources under normal circumstances (1000 threads can easily
794 can easily consume 30MB of RAM). 1164 consume 30MB of RAM).
795 1165
796 The default is probably ok in most situations, especially if 1166 The default is probably ok in most situations, especially if thread
797 thread creation is fast. If thread creation is very slow on your 1167 creation is fast. If thread creation is very slow on your system you
798 system you might want to use larger values. 1168 might want to use larger values.
799 1169
1170 IO::AIO::idle_timeout $seconds
1171 Sets the minimum idle timeout (default 10) after which worker
1172 threads are allowed to exit. SEe "IO::AIO::max_idle".
1173
800 $oldmaxreqs = IO::AIO::max_outstanding $maxreqs 1174 IO::AIO::max_outstanding $maxreqs
801 This is a very bad function to use in interactive programs 1175 This is a very bad function to use in interactive programs because
802 because it blocks, and a bad way to reduce concurrency because 1176 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 1177 inexact: Better use an "aio_group" together with a feed callback.
804 callback.
805 1178
806 Sets the maximum number of outstanding requests to $nreqs. If 1179 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 1180 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 1181 "poll_cb" (and "poll_some" and other functions calling "poll_cb")
809 "poll_cb") function will block until the limit is no longer 1182 function will block until the limit is no longer exceeded.
810 exceeded.
811 1183
812 The default value is very large, so there is no practical limit 1184 The default value is very large, so there is no practical limit on
813 on the number of outstanding requests. 1185 the number of outstanding requests.
814 1186
815 You can still queue as many requests as you want. Therefore, 1187 You can still queue as many requests as you want. Therefore,
816 "max_oustsanding" is mainly useful in simple scripts (with low 1188 "max_outstanding" is mainly useful in simple scripts (with low
817 values) or as a stop gap to shield against fatal memory overflow 1189 values) or as a stop gap to shield against fatal memory overflow
818 (with large values). 1190 (with large values).
819 1191
820 STATISTICAL INFORMATION 1192 STATISTICAL INFORMATION
821 IO::AIO::nreqs 1193 IO::AIO::nreqs
822 Returns the number of requests currently in the ready, execute 1194 Returns the number of requests currently in the ready, execute or
823 or pending states (i.e. for which their callback has not been 1195 pending states (i.e. for which their callback has not been invoked
824 invoked yet). 1196 yet).
825 1197
826 Example: wait till there are no outstanding requests anymore: 1198 Example: wait till there are no outstanding requests anymore:
827 1199
828 IO::AIO::poll_wait, IO::AIO::poll_cb 1200 IO::AIO::poll_wait, IO::AIO::poll_cb
829 while IO::AIO::nreqs; 1201 while IO::AIO::nreqs;
830 1202
831 IO::AIO::nready 1203 IO::AIO::nready
832 Returns the number of requests currently in the ready state (not 1204 Returns the number of requests currently in the ready state (not yet
833 yet executed). 1205 executed).
834 1206
835 IO::AIO::npending 1207 IO::AIO::npending
836 Returns the number of requests currently in the pending state 1208 Returns the number of requests currently in the pending state
837 (executed, but not yet processed by poll_cb). 1209 (executed, but not yet processed by poll_cb).
1210
1211 MISCELLANEOUS FUNCTIONS
1212 IO::AIO implements some functions that might be useful, but are not
1213 asynchronous.
1214
1215 IO::AIO::sendfile $ofh, $ifh, $offset, $count
1216 Calls the "eio_sendfile_sync" function, which is like
1217 "aio_sendfile", but is blocking (this makes most sense if you know
1218 the input data is likely cached already and the output filehandle is
1219 set to non-blocking operations).
1220
1221 Returns the number of bytes copied, or -1 on error.
1222
1223 IO::AIO::fadvise $fh, $offset, $len, $advice
1224 Simply calls the "posix_fadvise" function (see its manpage for
1225 details). The following advice constants are avaiable:
1226 "IO::AIO::FADV_NORMAL", "IO::AIO::FADV_SEQUENTIAL",
1227 "IO::AIO::FADV_RANDOM", "IO::AIO::FADV_NOREUSE",
1228 "IO::AIO::FADV_WILLNEED", "IO::AIO::FADV_DONTNEED".
1229
1230 On systems that do not implement "posix_fadvise", this function
1231 returns ENOSYS, otherwise the return value of "posix_fadvise".
1232
1233 IO::AIO::madvise $scalar, $offset, $len, $advice
1234 Simply calls the "posix_madvise" function (see its manpage for
1235 details). The following advice constants are avaiable:
1236 "IO::AIO::MADV_NORMAL", "IO::AIO::MADV_SEQUENTIAL",
1237 "IO::AIO::MADV_RANDOM", "IO::AIO::MADV_WILLNEED",
1238 "IO::AIO::MADV_DONTNEED".
1239
1240 On systems that do not implement "posix_madvise", this function
1241 returns ENOSYS, otherwise the return value of "posix_madvise".
1242
1243 IO::AIO::mprotect $scalar, $offset, $len, $protect
1244 Simply calls the "mprotect" function on the preferably AIO::mmap'ed
1245 $scalar (see its manpage for details). The following protect
1246 constants are avaiable: "IO::AIO::PROT_NONE", "IO::AIO::PROT_READ",
1247 "IO::AIO::PROT_WRITE", "IO::AIO::PROT_EXEC".
1248
1249 On systems that do not implement "mprotect", this function returns
1250 ENOSYS, otherwise the return value of "mprotect".
1251
1252 IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
1253 Memory-maps a file (or anonymous memory range) and attaches it to
1254 the given $scalar, which will act like a string scalar.
1255
1256 The only operations allowed on the scalar are "substr"/"vec" that
1257 don't change the string length, and most read-only operations such
1258 as copying it or searching it with regexes and so on.
1259
1260 Anything else is unsafe and will, at best, result in memory leaks.
1261
1262 The memory map associated with the $scalar is automatically removed
1263 when the $scalar is destroyed, or when the "IO::AIO::mmap" or
1264 "IO::AIO::munmap" functions are called.
1265
1266 This calls the "mmap"(2) function internally. See your system's
1267 manual page for details on the $length, $prot and $flags parameters.
1268
1269 The $length must be larger than zero and smaller than the actual
1270 filesize.
1271
1272 $prot is a combination of "IO::AIO::PROT_NONE",
1273 "IO::AIO::PROT_EXEC", "IO::AIO::PROT_READ" and/or
1274 "IO::AIO::PROT_WRITE",
1275
1276 $flags can be a combination of "IO::AIO::MAP_SHARED" or
1277 "IO::AIO::MAP_PRIVATE", or a number of system-specific flags (when
1278 not available, the are defined as 0): "IO::AIO::MAP_ANONYMOUS"
1279 (which is set to "MAP_ANON" if your system only provides this
1280 constant), "IO::AIO::MAP_HUGETLB", "IO::AIO::MAP_LOCKED",
1281 "IO::AIO::MAP_NORESERVE", "IO::AIO::MAP_POPULATE" or
1282 "IO::AIO::MAP_NONBLOCK"
1283
1284 If $fh is "undef", then a file descriptor of -1 is passed.
1285
1286 $offset is the offset from the start of the file - it generally must
1287 be a multiple of "IO::AIO::PAGESIZE" and defaults to 0.
1288
1289 Example:
1290
1291 use Digest::MD5;
1292 use IO::AIO;
1293
1294 open my $fh, "<verybigfile"
1295 or die "$!";
1296
1297 IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
1298 or die "verybigfile: $!";
1299
1300 my $fast_md5 = md5 $data;
1301
1302 IO::AIO::munmap $scalar
1303 Removes a previous mmap and undefines the $scalar.
1304
1305 IO::AIO::munlock $scalar, $offset = 0, $length = undef
1306 Calls the "munlock" function, undoing the effects of a previous
1307 "aio_mlock" call (see its description for details).
1308
1309 IO::AIO::munlockall
1310 Calls the "munlockall" function.
1311
1312 On systems that do not implement "munlockall", this function returns
1313 ENOSYS, otherwise the return value of "munlockall".
1314
1315EVENT LOOP INTEGRATION
1316 It is recommended to use AnyEvent::AIO to integrate IO::AIO
1317 automatically into many event loops:
1318
1319 # AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
1320 use AnyEvent::AIO;
1321
1322 You can also integrate IO::AIO manually into many event loops, here are
1323 some examples of how to do this:
1324
1325 # EV integration
1326 my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
1327
1328 # Event integration
1329 Event->io (fd => IO::AIO::poll_fileno,
1330 poll => 'r',
1331 cb => \&IO::AIO::poll_cb);
1332
1333 # Glib/Gtk2 integration
1334 add_watch Glib::IO IO::AIO::poll_fileno,
1335 in => sub { IO::AIO::poll_cb; 1 };
1336
1337 # Tk integration
1338 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
1339 readable => \&IO::AIO::poll_cb);
1340
1341 # Danga::Socket integration
1342 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
1343 \&IO::AIO::poll_cb);
838 1344
839 FORK BEHAVIOUR 1345 FORK BEHAVIOUR
840 This module should do "the right thing" when the process using it 1346 This module should do "the right thing" when the process using it forks:
841 forks:
842 1347
843 Before the fork, IO::AIO enters a quiescent state where no requests 1348 Before the fork, IO::AIO enters a quiescent state where no requests can
844 can be added in other threads and no results will be processed. 1349 be added in other threads and no results will be processed. After the
845 After the fork the parent simply leaves the quiescent state and 1350 fork the parent simply leaves the quiescent state and continues
846 continues request/result processing, while the child frees the 1351 request/result processing, while the child frees the request/result
847 request/result queue (so that the requests started before the fork 1352 queue (so that the requests started before the fork will only be handled
848 will only be handled in the parent). Threads will be started on 1353 in the parent). Threads will be started on demand until the limit set in
849 demand until the limit set in the parent process has been reached 1354 the parent process has been reached again.
850 again.
851 1355
852 In short: the parent will, after a short pause, continue as if fork 1356 In short: the parent will, after a short pause, continue as if fork had
853 had not been called, while the child will act as if IO::AIO has not 1357 not been called, while the child will act as if IO::AIO has not been
854 been used yet. 1358 used yet.
855 1359
856 MEMORY USAGE 1360 MEMORY USAGE
857 Per-request usage: 1361 Per-request usage:
858 1362
859 Each aio request uses - depending on your architecture - around 1363 Each aio request uses - depending on your architecture - around 100-200
860 100-200 bytes of memory. In addition, stat requests need a stat 1364 bytes of memory. In addition, stat requests need a stat buffer (possibly
861 buffer (possibly a few hundred bytes), readdir requires a result 1365 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 1366 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 1367 will consume memory till the request has entered the done state.
864 request has entered the done state.
865 1368
866 This is now awfully much, so queuing lots of requests is not usually 1369 This is not awfully much, so queuing lots of requests is not usually a
867 a problem. 1370 problem.
868 1371
869 Per-thread usage: 1372 Per-thread usage:
870 1373
871 In the execution phase, some aio requests require more memory for 1374 In the execution phase, some aio requests require more memory for
872 temporary buffers, and each thread requires a stack and other data 1375 temporary buffers, and each thread requires a stack and other data
873 structures (usually around 16k-128k, depending on the OS). 1376 structures (usually around 16k-128k, depending on the OS).
874 1377
875KNOWN BUGS 1378KNOWN BUGS
876 Known bugs will be fixed in the next release. 1379 Known bugs will be fixed in the next release.
877 1380
878SEE ALSO 1381SEE ALSO
879 Coro::AIO. 1382 AnyEvent::AIO for easy integration into event loops, Coro::AIO for a
1383 more natural syntax.
880 1384
881AUTHOR 1385AUTHOR
882 Marc Lehmann <schmorp@schmorp.de> 1386 Marc Lehmann <schmorp@schmorp.de>
883 http://home.schmorp.de/ 1387 http://home.schmorp.de/
884 1388

Diff Legend

– Removed lines
+ Added lines
< Changed lines
> Changed lines