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Revision 1.49 by root, Mon Jul 18 03:09:06 2011 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_realpath $path, $callback->($link)
174 aio_rename $srcpath, $dstpath, $callback->($status)
175 aio_mkdir $pathname, $mode, $callback->($status)
176 aio_rmdir $pathname, $callback->($status)
177 aio_readdir $pathname, $callback->($entries)
178 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
179 IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
180 IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
181 aio_load $path, $data, $callback->($status)
182 aio_copy $srcpath, $dstpath, $callback->($status)
183 aio_move $srcpath, $dstpath, $callback->($status)
184 aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
185 aio_rmtree $path, $callback->($status)
186 aio_sync $callback->($status)
187 aio_fsync $fh, $callback->($status)
188 aio_fdatasync $fh, $callback->($status)
189 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
190 aio_pathsync $path, $callback->($status)
191 aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
192 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
193 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
194 aio_mlockall $flags, $callback->($status)
195 aio_group $callback->(...)
196 aio_nop $callback->()
197
198 $prev_pri = aioreq_pri [$pri]
199 aioreq_nice $pri_adjust
200
201 IO::AIO::poll_wait
202 IO::AIO::poll_cb
203 IO::AIO::poll
204 IO::AIO::flush
205 IO::AIO::max_poll_reqs $nreqs
206 IO::AIO::max_poll_time $seconds
207 IO::AIO::min_parallel $nthreads
208 IO::AIO::max_parallel $nthreads
209 IO::AIO::max_idle $nthreads
210 IO::AIO::idle_timeout $seconds
211 IO::AIO::max_outstanding $maxreqs
212 IO::AIO::nreqs
213 IO::AIO::nready
214 IO::AIO::npending
215
216 IO::AIO::sendfile $ofh, $ifh, $offset, $count
217 IO::AIO::fadvise $fh, $offset, $len, $advice
218 IO::AIO::madvise $scalar, $offset, $length, $advice
219 IO::AIO::mprotect $scalar, $offset, $length, $protect
220 IO::AIO::munlock $scalar, $offset = 0, $length = undef
221 IO::AIO::munlockall
222
171 AIO REQUEST FUNCTIONS 223 AIO REQUEST FUNCTIONS
172 All the "aio_*" calls are more or less thin wrappers around the 224 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 225 with the same name (sans "aio_"). The arguments are similar or
174 or identical, and they all accept an additional (and optional) 226 identical, and they all accept an additional (and optional) $callback
175 $callback argument which must be a code reference. This code 227 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 228 called with the syscall return code (e.g. most syscalls return -1 on
177 syscalls return -1 on error, unlike perl, which usually delivers 229 error, unlike perl, which usually delivers "false") as its sole argument
178 "false") as it's sole argument when the given syscall has been 230 after the given syscall has been executed asynchronously.
179 executed asynchronously.
180 231
181 All functions expecting a filehandle keep a copy of the filehandle 232 All functions expecting a filehandle keep a copy of the filehandle
182 internally until the request has finished. 233 internally until the request has finished.
183 234
184 All functions return request objects of type IO::AIO::REQ that allow 235 All functions return request objects of type IO::AIO::REQ that allow
185 further manipulation of those requests while they are in-flight. 236 further manipulation of those requests while they are in-flight.
186 237
187 The pathnames you pass to these routines *must* be absolute and 238 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 239 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 240 being executed, the current working directory could have changed.
190 changed. Alternatively, you can make sure that you never change the 241 Alternatively, you can make sure that you never change the current
191 current working directory anywhere in the program and then use 242 working directory anywhere in the program and then use relative paths.
192 relative paths.
193 243
194 To encode pathnames as octets, either make sure you either: a) 244 To encode pathnames as octets, either make sure you either: a) always
195 always pass in filenames you got from outside (command line, readdir 245 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 246 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) 247 and encode your pathnames to the locale (or other) encoding in effect in
198 encoding in effect in the user environment, d) use 248 the user environment, d) use Glib::filename_from_unicode on unicode
199 Glib::filename_from_unicode on unicode filenames or e) use something 249 filenames or e) use something else to ensure your scalar has the correct
200 else to ensure your scalar has the correct contents. 250 contents.
201 251
202 This works, btw. independent of the internal UTF-8 bit, which 252 This works, btw. independent of the internal UTF-8 bit, which IO::AIO
203 IO::AIO handles correctly wether it is set or not. 253 handles correctly whether it is set or not.
204 254
205 $prev_pri = aioreq_pri [$pri] 255 $prev_pri = aioreq_pri [$pri]
206 Returns the priority value that would be used for the next 256 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 257 and, if $pri is given, sets the priority for the next aio request.
208 aio request.
209 258
210 The default priority is 0, the minimum and maximum priorities 259 The default priority is 0, the minimum and maximum priorities are -4
211 are -4 and 4, respectively. Requests with higher priority will 260 and 4, respectively. Requests with higher priority will be serviced
212 be serviced first. 261 first.
213 262
214 The priority will be reset to 0 after each call to one of the 263 The priority will be reset to 0 after each call to one of the
215 "aio_*" functions. 264 "aio_*" functions.
216 265
217 Example: open a file with low priority, then read something from 266 Example: open a file with low priority, then read something from it
218 it with higher priority so the read request is serviced before 267 with higher priority so the read request is serviced before other
219 other low priority open requests (potentially spamming the 268 low priority open requests (potentially spamming the cache):
220 cache):
221 269
270 aioreq_pri -3;
271 aio_open ..., sub {
272 return unless $_[0];
273
222 aioreq_pri -3; 274 aioreq_pri -2;
223 aio_open ..., sub {
224 return unless $_[0];
225
226 aioreq_pri -2;
227 aio_read $_[0], ..., sub { 275 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 ...; 276 ...
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 }; 277 };
571 }; 278 };
572 279
280 aioreq_nice $pri_adjust
281 Similar to "aioreq_pri", but subtracts the given value from the
282 current priority, so the effect is cumulative.
283
284 aio_open $pathname, $flags, $mode, $callback->($fh)
285 Asynchronously open or create a file and call the callback with a
286 newly created filehandle for the file.
287
288 The pathname passed to "aio_open" must be absolute. See API NOTES,
289 above, for an explanation.
290
291 The $flags argument is a bitmask. See the "Fcntl" module for a list.
292 They are the same as used by "sysopen".
293
294 Likewise, $mode specifies the mode of the newly created file, if it
295 didn't exist and "O_CREAT" has been given, just like perl's
296 "sysopen", except that it is mandatory (i.e. use 0 if you don't
297 create new files, and 0666 or 0777 if you do). Note that the $mode
298 will be modified by the umask in effect then the request is being
299 executed, so better never change the umask.
300
301 Example:
302
303 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
304 if ($_[0]) {
305 print "open successful, fh is $_[0]\n";
306 ...
307 } else {
308 die "open failed: $!\n";
309 }
310 };
311
312 In addition to all the common open modes/flags ("O_RDONLY",
313 "O_WRONLY", "O_RDWR", "O_CREAT", "O_TRUNC", "O_EXCL" and
314 "O_APPEND"), the following POSIX and non-POSIX constants are
315 available (missing ones on your system are, as usual, 0):
316
317 "O_ASYNC", "O_DIRECT", "O_NOATIME", "O_CLOEXEC", "O_NOCTTY",
318 "O_NOFOLLOW", "O_NONBLOCK", "O_EXEC", "O_SEARCH", "O_DIRECTORY",
319 "O_DSYNC", "O_RSYNC", "O_SYNC" and "O_TTY_INIT".
320
321 aio_close $fh, $callback->($status)
322 Asynchronously close a file and call the callback with the result
323 code.
324
325 Unfortunately, you can't do this to perl. Perl *insists* very
326 strongly on closing the file descriptor associated with the
327 filehandle itself.
328
329 Therefore, "aio_close" will not close the filehandle - instead it
330 will use dup2 to overwrite the file descriptor with the write-end of
331 a pipe (the pipe fd will be created on demand and will be cached).
332
333 Or in other words: the file descriptor will be closed, but it will
334 not be free for reuse until the perl filehandle is closed.
335
336 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
337 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
338 Reads or writes $length bytes from or to the specified $fh and
339 $offset into the scalar given by $data and offset $dataoffset and
340 calls the callback without the actual number of bytes read (or -1 on
341 error, just like the syscall).
342
343 "aio_read" will, like "sysread", shrink or grow the $data scalar to
344 offset plus the actual number of bytes read.
345
346 If $offset is undefined, then the current file descriptor offset
347 will be used (and updated), otherwise the file descriptor offset
348 will not be changed by these calls.
349
350 If $length is undefined in "aio_write", use the remaining length of
351 $data.
352
353 If $dataoffset is less than zero, it will be counted from the end of
354 $data.
355
356 The $data scalar *MUST NOT* be modified in any way while the request
357 is outstanding. Modifying it can result in segfaults or World War
358 III (if the necessary/optional hardware is installed).
359
360 Example: Read 15 bytes at offset 7 into scalar $buffer, starting at
361 offset 0 within the scalar:
362
363 aio_read $fh, 7, 15, $buffer, 0, sub {
364 $_[0] > 0 or die "read error: $!";
365 print "read $_[0] bytes: <$buffer>\n";
366 };
367
368 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
369 Tries to copy $length bytes from $in_fh to $out_fh. It starts
370 reading at byte offset $in_offset, and starts writing at the current
371 file offset of $out_fh. Because of that, it is not safe to issue
372 more than one "aio_sendfile" per $out_fh, as they will interfere
373 with each other. The same $in_fh works fine though, as this function
374 does not move or use the file offset of $in_fh.
375
376 Please note that "aio_sendfile" can read more bytes from $in_fh than
377 are written, and there is no way to find out how many more bytes
378 have been read from "aio_sendfile" alone, as "aio_sendfile" only
379 provides the number of bytes written to $out_fh. Only if the result
380 value equals $length one can assume that $length bytes have been
381 read.
382
383 Unlike with other "aio_" functions, it makes a lot of sense to use
384 "aio_sendfile" on non-blocking sockets, as long as one end
385 (typically the $in_fh) is a file - the file I/O will then be
386 asynchronous, while the socket I/O will be non-blocking. Note,
387 however, that you can run into a trap where "aio_sendfile" reads
388 some data with readahead, then fails to write all data, and when the
389 socket is ready the next time, the data in the cache is already
390 lost, forcing "aio_sendfile" to again hit the disk. Explicit
391 "aio_read" + "aio_write" let's you better control resource usage.
392
393 This call tries to make use of a native "sendfile"-like syscall to
394 provide zero-copy operation. For this to work, $out_fh should refer
395 to a socket, and $in_fh should refer to an mmap'able file.
396
397 If a native sendfile cannot be found or it fails with "ENOSYS",
398 "EINVAL", "ENOTSUP", "EOPNOTSUPP", "EAFNOSUPPORT", "EPROTOTYPE" or
399 "ENOTSOCK", it will be emulated, so you can call "aio_sendfile" on
400 any type of filehandle regardless of the limitations of the
401 operating system.
402
403 As native sendfile syscalls (as practically any non-POSIX interface
404 hacked together in a hurry to improve benchmark numbers) tend to be
405 rather buggy on many systems, this implementation tries to work
406 around some known bugs in Linux and FreeBSD kernels (probably
407 others, too), but that might fail, so you really really should check
408 the return value of "aio_sendfile" - fewre bytes than expected might
409 have been transferred.
410
411 aio_readahead $fh,$offset,$length, $callback->($retval)
412 "aio_readahead" populates the page cache with data from a file so
413 that subsequent reads from that file will not block on disk I/O. The
414 $offset argument specifies the starting point from which data is to
415 be read and $length specifies the number of bytes to be read. I/O is
416 performed in whole pages, so that offset is effectively rounded down
417 to a page boundary and bytes are read up to the next page boundary
418 greater than or equal to (off-set+length). "aio_readahead" does not
419 read beyond the end of the file. The current file offset of the file
420 is left unchanged.
421
422 If that syscall doesn't exist (likely if your OS isn't Linux) it
423 will be emulated by simply reading the data, which would have a
424 similar effect.
425
426 aio_stat $fh_or_path, $callback->($status)
427 aio_lstat $fh, $callback->($status)
428 Works like perl's "stat" or "lstat" in void context. The callback
429 will be called after the stat and the results will be available
430 using "stat _" or "-s _" etc...
431
432 The pathname passed to "aio_stat" must be absolute. See API NOTES,
433 above, for an explanation.
434
435 Currently, the stats are always 64-bit-stats, i.e. instead of
436 returning an error when stat'ing a large file, the results will be
437 silently truncated unless perl itself is compiled with large file
438 support.
439
440 To help interpret the mode and dev/rdev stat values, IO::AIO offers
441 the following constants and functions (if not implemented, the
442 constants will be 0 and the functions will either "croak" or fall
443 back on traditional behaviour).
444
445 "S_IFMT", "S_IFIFO", "S_IFCHR", "S_IFBLK", "S_IFLNK", "S_IFREG",
446 "S_IFDIR", "S_IFWHT", "S_IFSOCK", "IO::AIO::major $dev_t",
447 "IO::AIO::minor $dev_t", "IO::AIO::makedev $major, $minor".
448
449 Example: Print the length of /etc/passwd:
450
451 aio_stat "/etc/passwd", sub {
452 $_[0] and die "stat failed: $!";
453 print "size is ", -s _, "\n";
454 };
455
456 aio_statvfs $fh_or_path, $callback->($statvfs)
457 Works like the POSIX "statvfs" or "fstatvfs" syscalls, depending on
458 whether a file handle or path was passed.
459
460 On success, the callback is passed a hash reference with the
461 following members: "bsize", "frsize", "blocks", "bfree", "bavail",
462 "files", "ffree", "favail", "fsid", "flag" and "namemax". On
463 failure, "undef" is passed.
464
465 The following POSIX IO::AIO::ST_* constants are defined: "ST_RDONLY"
466 and "ST_NOSUID".
467
468 The following non-POSIX IO::AIO::ST_* flag masks are defined to
469 their correct value when available, or to 0 on systems that do not
470 support them: "ST_NODEV", "ST_NOEXEC", "ST_SYNCHRONOUS",
471 "ST_MANDLOCK", "ST_WRITE", "ST_APPEND", "ST_IMMUTABLE",
472 "ST_NOATIME", "ST_NODIRATIME" and "ST_RELATIME".
473
474 Example: stat "/wd" and dump out the data if successful.
475
476 aio_statvfs "/wd", sub {
477 my $f = $_[0]
478 or die "statvfs: $!";
479
480 use Data::Dumper;
481 say Dumper $f;
482 };
483
484 # result:
485 {
486 bsize => 1024,
487 bfree => 4333064312,
488 blocks => 10253828096,
489 files => 2050765568,
490 flag => 4096,
491 favail => 2042092649,
492 bavail => 4333064312,
493 ffree => 2042092649,
494 namemax => 255,
495 frsize => 1024,
496 fsid => 1810
497 }
498
499 aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
500 Works like perl's "utime" function (including the special case of
501 $atime and $mtime being undef). Fractional times are supported if
502 the underlying syscalls support them.
503
504 When called with a pathname, uses utimes(2) if available, otherwise
505 utime(2). If called on a file descriptor, uses futimes(2) if
506 available, otherwise returns ENOSYS, so this is not portable.
507
508 Examples:
509
510 # set atime and mtime to current time (basically touch(1)):
511 aio_utime "path", undef, undef;
512 # set atime to current time and mtime to beginning of the epoch:
513 aio_utime "path", time, undef; # undef==0
514
515 aio_chown $fh_or_path, $uid, $gid, $callback->($status)
516 Works like perl's "chown" function, except that "undef" for either
517 $uid or $gid is being interpreted as "do not change" (but -1 can
518 also be used).
519
520 Examples:
521
522 # same as "chown root path" in the shell:
523 aio_chown "path", 0, -1;
524 # same as above:
525 aio_chown "path", 0, undef;
526
527 aio_truncate $fh_or_path, $offset, $callback->($status)
528 Works like truncate(2) or ftruncate(2).
529
530 aio_chmod $fh_or_path, $mode, $callback->($status)
531 Works like perl's "chmod" function.
532
533 aio_unlink $pathname, $callback->($status)
534 Asynchronously unlink (delete) a file and call the callback with the
535 result code.
536
537 aio_mknod $path, $mode, $dev, $callback->($status)
538 [EXPERIMENTAL]
539
540 Asynchronously create a device node (or fifo). See mknod(2).
541
542 The only (POSIX-) portable way of calling this function is:
543
544 aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...
545
546 See "aio_stat" for info about some potentially helpful extra
547 constants and functions.
548
549 aio_link $srcpath, $dstpath, $callback->($status)
550 Asynchronously create a new link to the existing object at $srcpath
551 at the path $dstpath and call the callback with the result code.
552
553 aio_symlink $srcpath, $dstpath, $callback->($status)
554 Asynchronously create a new symbolic link to the existing object at
555 $srcpath at the path $dstpath and call the callback with the result
556 code.
557
558 aio_readlink $path, $callback->($link)
559 Asynchronously read the symlink specified by $path and pass it to
560 the callback. If an error occurs, nothing or undef gets passed to
561 the callback.
562
563 aio_realpath $path, $callback->($path)
564 Asynchronously make the path absolute and resolve any symlinks in
565 $path. The resulting path only consists of directories (Same as
566 Cwd::realpath).
567
568 This request can be used to get the absolute path of the current
569 working directory by passing it a path of . (a single dot).
570
571 aio_rename $srcpath, $dstpath, $callback->($status)
572 Asynchronously rename the object at $srcpath to $dstpath, just as
573 rename(2) and call the callback with the result code.
574
575 aio_mkdir $pathname, $mode, $callback->($status)
576 Asynchronously mkdir (create) a directory and call the callback with
577 the result code. $mode will be modified by the umask at the time the
578 request is executed, so do not change your umask.
579
580 aio_rmdir $pathname, $callback->($status)
581 Asynchronously rmdir (delete) a directory and call the callback with
582 the result code.
583
584 aio_readdir $pathname, $callback->($entries)
585 Unlike the POSIX call of the same name, "aio_readdir" reads an
586 entire directory (i.e. opendir + readdir + closedir). The entries
587 will not be sorted, and will NOT include the "." and ".." entries.
588
589 The callback is passed a single argument which is either "undef" or
590 an array-ref with the filenames.
591
592 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
593 Quite similar to "aio_readdir", but the $flags argument allows to
594 tune behaviour and output format. In case of an error, $entries will
595 be "undef".
596
597 The flags are a combination of the following constants, ORed
598 together (the flags will also be passed to the callback, possibly
599 modified):
600
601 IO::AIO::READDIR_DENTS
602 When this flag is off, then the callback gets an arrayref
603 consisting of names only (as with "aio_readdir"), otherwise it
604 gets an arrayref with "[$name, $type, $inode]" arrayrefs, each
605 describing a single directory entry in more detail.
606
607 $name is the name of the entry.
608
609 $type is one of the "IO::AIO::DT_xxx" constants:
610
611 "IO::AIO::DT_UNKNOWN", "IO::AIO::DT_FIFO", "IO::AIO::DT_CHR",
612 "IO::AIO::DT_DIR", "IO::AIO::DT_BLK", "IO::AIO::DT_REG",
613 "IO::AIO::DT_LNK", "IO::AIO::DT_SOCK", "IO::AIO::DT_WHT".
614
615 "IO::AIO::DT_UNKNOWN" means just that: readdir does not know. If
616 you need to know, you have to run stat yourself. Also, for speed
617 reasons, the $type scalars are read-only: you can not modify
618 them.
619
620 $inode is the inode number (which might not be exact on systems
621 with 64 bit inode numbers and 32 bit perls). This field has
622 unspecified content on systems that do not deliver the inode
623 information.
624
625 IO::AIO::READDIR_DIRS_FIRST
626 When this flag is set, then the names will be returned in an
627 order where likely directories come first, in optimal stat
628 order. This is useful when you need to quickly find directories,
629 or you want to find all directories while avoiding to stat()
630 each entry.
631
632 If the system returns type information in readdir, then this is
633 used to find directories directly. Otherwise, likely directories
634 are names beginning with ".", or otherwise names with no dots,
635 of which names with short names are tried first.
636
637 IO::AIO::READDIR_STAT_ORDER
638 When this flag is set, then the names will be returned in an
639 order suitable for stat()'ing each one. That is, when you plan
640 to stat() all files in the given directory, then the returned
641 order will likely be fastest.
642
643 If both this flag and "IO::AIO::READDIR_DIRS_FIRST" are
644 specified, then the likely dirs come first, resulting in a less
645 optimal stat order.
646
647 IO::AIO::READDIR_FOUND_UNKNOWN
648 This flag should not be set when calling "aio_readdirx".
649 Instead, it is being set by "aio_readdirx", when any of the
650 $type's found were "IO::AIO::DT_UNKNOWN". The absense of this
651 flag therefore indicates that all $type's are known, which can
652 be used to speed up some algorithms.
653
654 aio_load $path, $data, $callback->($status)
655 This is a composite request that tries to fully load the given file
656 into memory. Status is the same as with aio_read.
657
658 aio_copy $srcpath, $dstpath, $callback->($status)
659 Try to copy the *file* (directories not supported as either source
660 or destination) from $srcpath to $dstpath and call the callback with
661 a status of 0 (ok) or -1 (error, see $!).
662
663 This is a composite request that creates the destination file with
664 mode 0200 and copies the contents of the source file into it using
665 "aio_sendfile", followed by restoring atime, mtime, access mode and
666 uid/gid, in that order.
667
668 If an error occurs, the partial destination file will be unlinked,
669 if possible, except when setting atime, mtime, access mode and
670 uid/gid, where errors are being ignored.
671
672 aio_move $srcpath, $dstpath, $callback->($status)
673 Try to move the *file* (directories not supported as either source
674 or destination) from $srcpath to $dstpath and call the callback with
675 a status of 0 (ok) or -1 (error, see $!).
676
677 This is a composite request that tries to rename(2) the file first;
678 if rename fails with "EXDEV", it copies the file with "aio_copy"
679 and, if that is successful, unlinks the $srcpath.
680
681 aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
682 Scans a directory (similar to "aio_readdir") but additionally tries
683 to efficiently separate the entries of directory $path into two sets
684 of names, directories you can recurse into (directories), and ones
685 you cannot recurse into (everything else, including symlinks to
686 directories).
687
688 "aio_scandir" is a composite request that creates of many sub
689 requests_ $maxreq specifies the maximum number of outstanding aio
690 requests that this function generates. If it is "<= 0", then a
691 suitable default will be chosen (currently 4).
692
693 On error, the callback is called without arguments, otherwise it
694 receives two array-refs with path-relative entry names.
695
696 Example:
697
698 aio_scandir $dir, 0, sub {
699 my ($dirs, $nondirs) = @_;
700 print "real directories: @$dirs\n";
701 print "everything else: @$nondirs\n";
702 };
703
704 Implementation notes.
705
706 The "aio_readdir" cannot be avoided, but "stat()"'ing every entry
707 can.
708
709 If readdir returns file type information, then this is used directly
710 to find directories.
711
712 Otherwise, after reading the directory, the modification time, size
713 etc. of the directory before and after the readdir is checked, and
714 if they match (and isn't the current time), the link count will be
715 used to decide how many entries are directories (if >= 2).
716 Otherwise, no knowledge of the number of subdirectories will be
717 assumed.
718
719 Then entries will be sorted into likely directories a non-initial
720 dot currently) and likely non-directories (see "aio_readdirx"). Then
721 every entry plus an appended "/." will be "stat"'ed, likely
722 directories first, in order of their inode numbers. If that
723 succeeds, it assumes that the entry is a directory or a symlink to
724 directory (which will be checked seperately). This is often faster
725 than stat'ing the entry itself because filesystems might detect the
726 type of the entry without reading the inode data (e.g. ext2fs
727 filetype feature), even on systems that cannot return the filetype
728 information on readdir.
729
730 If the known number of directories (link count - 2) has been
731 reached, the rest of the entries is assumed to be non-directories.
732
733 This only works with certainty on POSIX (= UNIX) filesystems, which
734 fortunately are the vast majority of filesystems around.
735
736 It will also likely work on non-POSIX filesystems with reduced
737 efficiency as those tend to return 0 or 1 as link counts, which
738 disables the directory counting heuristic.
739
740 aio_rmtree $path, $callback->($status)
741 Delete a directory tree starting (and including) $path, return the
742 status of the final "rmdir" only. This is a composite request that
743 uses "aio_scandir" to recurse into and rmdir directories, and unlink
744 everything else.
745
746 aio_sync $callback->($status)
747 Asynchronously call sync and call the callback when finished.
748
749 aio_fsync $fh, $callback->($status)
750 Asynchronously call fsync on the given filehandle and call the
751 callback with the fsync result code.
752
753 aio_fdatasync $fh, $callback->($status)
754 Asynchronously call fdatasync on the given filehandle and call the
755 callback with the fdatasync result code.
756
757 If this call isn't available because your OS lacks it or it couldn't
758 be detected, it will be emulated by calling "fsync" instead.
759
760 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
761 Sync the data portion of the file specified by $offset and $length
762 to disk (but NOT the metadata), by calling the Linux-specific
763 sync_file_range call. If sync_file_range is not available or it
764 returns ENOSYS, then fdatasync or fsync is being substituted.
765
766 $flags can be a combination of
767 "IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE",
768 "IO::AIO::SYNC_FILE_RANGE_WRITE" and
769 "IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER": refer to the sync_file_range
770 manpage for details.
771
772 aio_pathsync $path, $callback->($status)
773 This request tries to open, fsync and close the given path. This is
774 a composite request intended to sync directories after directory
775 operations (E.g. rename). This might not work on all operating
776 systems or have any specific effect, but usually it makes sure that
777 directory changes get written to disc. It works for anything that
778 can be opened for read-only, not just directories.
779
780 Future versions of this function might fall back to other methods
781 when "fsync" on the directory fails (such as calling "sync").
782
783 Passes 0 when everything went ok, and -1 on error.
784
785 aio_msync $scalar, $offset = 0, $length = undef, flags = 0,
786 $callback->($status)
787 This is a rather advanced IO::AIO call, which only works on
788 mmap(2)ed scalars (see the "IO::AIO::mmap" function, although it
789 also works on data scalars managed by the Sys::Mmap or Mmap modules,
790 note that the scalar must only be modified in-place while an aio
791 operation is pending on it).
792
793 It calls the "msync" function of your OS, if available, with the
794 memory area starting at $offset in the string and ending $length
795 bytes later. If $length is negative, counts from the end, and if
796 $length is "undef", then it goes till the end of the string. The
797 flags can be a combination of "IO::AIO::MS_ASYNC",
798 "IO::AIO::MS_INVALIDATE" and "IO::AIO::MS_SYNC".
799
800 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0,
801 $callback->($status)
802 This is a rather advanced IO::AIO call, which works best on
803 mmap(2)ed scalars.
804
805 It touches (reads or writes) all memory pages in the specified range
806 inside the scalar. All caveats and parameters are the same as for
807 "aio_msync", above, except for flags, which must be either 0 (which
808 reads all pages and ensures they are instantiated) or
809 "IO::AIO::MT_MODIFY", which modifies the memory page s(by reading
810 and writing an octet from it, which dirties the page).
811
812 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
813 This is a rather advanced IO::AIO call, which works best on
814 mmap(2)ed scalars.
815
816 It reads in all the pages of the underlying storage into memory (if
817 any) and locks them, so they are not getting swapped/paged out or
818 removed.
819
820 If $length is undefined, then the scalar will be locked till the
821 end.
822
823 On systems that do not implement "mlock", this function returns -1
824 and sets errno to "ENOSYS".
825
826 Note that the corresponding "munlock" is synchronous and is
827 documented under "MISCELLANEOUS FUNCTIONS".
828
829 Example: open a file, mmap and mlock it - both will be undone when
830 $data gets destroyed.
831
832 open my $fh, "<", $path or die "$path: $!";
833 my $data;
834 IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
835 aio_mlock $data; # mlock in background
836
837 aio_mlockall $flags, $callback->($status)
838 Calls the "mlockall" function with the given $flags (a combination
839 of "IO::AIO::MCL_CURRENT" and "IO::AIO::MCL_FUTURE").
840
841 On systems that do not implement "mlockall", this function returns
842 -1 and sets errno to "ENOSYS".
843
844 Note that the corresponding "munlockall" is synchronous and is
845 documented under "MISCELLANEOUS FUNCTIONS".
846
847 Example: asynchronously lock all current and future pages into
848 memory.
849
850 aio_mlockall IO::AIO::MCL_FUTURE;
851
852 aio_group $callback->(...)
853 This is a very special aio request: Instead of doing something, it
854 is a container for other aio requests, which is useful if you want
855 to bundle many requests into a single, composite, request with a
856 definite callback and the ability to cancel the whole request with
857 its subrequests.
858
859 Returns an object of class IO::AIO::GRP. See its documentation below
860 for more info.
861
862 Example:
863
864 my $grp = aio_group sub {
865 print "all stats done\n";
866 };
867
868 add $grp
869 (aio_stat ...),
870 (aio_stat ...),
871 ...;
872
873 aio_nop $callback->()
874 This is a special request - it does nothing in itself and is only
875 used for side effects, such as when you want to add a dummy request
876 to a group so that finishing the requests in the group depends on
877 executing the given code.
878
879 While this request does nothing, it still goes through the execution
880 phase and still requires a worker thread. Thus, the callback will
881 not be executed immediately but only after other requests in the
882 queue have entered their execution phase. This can be used to
883 measure request latency.
884
885 IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
886 Mainly used for debugging and benchmarking, this aio request puts
887 one of the request workers to sleep for the given time.
888
889 While it is theoretically handy to have simple I/O scheduling
890 requests like sleep and file handle readable/writable, the overhead
891 this creates is immense (it blocks a thread for a long time) so do
892 not use this function except to put your application under
893 artificial I/O pressure.
894
895 IO::AIO::REQ CLASS
896 All non-aggregate "aio_*" functions return an object of this class when
897 called in non-void context.
898
899 cancel $req
900 Cancels the request, if possible. Has the effect of skipping
901 execution when entering the execute state and skipping calling the
902 callback when entering the the result state, but will leave the
903 request otherwise untouched (with the exception of readdir). That
904 means that requests that currently execute will not be stopped and
905 resources held by the request will not be freed prematurely.
906
907 cb $req $callback->(...)
908 Replace (or simply set) the callback registered to the request.
909
910 IO::AIO::GRP CLASS
911 This class is a subclass of IO::AIO::REQ, so all its methods apply to
912 objects of this class, too.
913
914 A IO::AIO::GRP object is a special request that can contain multiple
915 other aio requests.
916
917 You create one by calling the "aio_group" constructing function with a
918 callback that will be called when all contained requests have entered
919 the "done" state:
920
921 my $grp = aio_group sub {
922 print "all requests are done\n";
923 };
924
925 You add requests by calling the "add" method with one or more
926 "IO::AIO::REQ" objects:
927
928 $grp->add (aio_unlink "...");
929
930 add $grp aio_stat "...", sub {
931 $_[0] or return $grp->result ("error");
932
933 # add another request dynamically, if first succeeded
934 add $grp aio_open "...", sub {
935 $grp->result ("ok");
936 };
937 };
938
573 This makes it very easy to create composite requests (see the source 939 This makes it very easy to create composite requests (see the source of
574 of "aio_move" for an application) that work and feel like simple 940 "aio_move" for an application) that work and feel like simple requests.
575 requests.
576 941
577 * The IO::AIO::GRP objects will be cleaned up during calls to 942 * The IO::AIO::GRP objects will be cleaned up during calls to
578 "IO::AIO::poll_cb", just like any other request. 943 "IO::AIO::poll_cb", just like any other request.
944
579 * They can be canceled like any other request. Canceling will cancel 945 * They can be canceled like any other request. Canceling will cancel
580 not only the request itself, but also all requests it contains. 946 not only the request itself, but also all requests it contains.
947
581 * They can also can also be added to other IO::AIO::GRP objects. 948 * They can also can also be added to other IO::AIO::GRP objects.
949
582 * You must not add requests to a group from within the group 950 * You must not add requests to a group from within the group callback
583 callback (or any later time). 951 (or any later time).
584 952
585 Their lifetime, simplified, looks like this: when they are empty, 953 Their lifetime, simplified, looks like this: when they are empty, they
586 they will finish very quickly. If they contain only requests that 954 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 955 "done" state, they will also finish. Otherwise they will continue to
588 continue to exist. 956 exist.
589 957
590 That means after creating a group you have some time to add 958 That means after creating a group you have some time to add requests
959 (precisely before the callback has been invoked, which is only done
591 requests. And in the callbacks of those requests, you can add 960 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 961 add further requests to the group. And only when all those requests have
593 finished will the the group itself finish. 962 finished will the the group itself finish.
594 963
595 add $grp ... 964 add $grp ...
596 $grp->add (...) 965 $grp->add (...)
597 Add one or more requests to the group. Any type of IO::AIO::REQ 966 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 967 be added, including other groups, as long as you do not create
599 create circular dependencies. 968 circular dependencies.
600 969
601 Returns all its arguments. 970 Returns all its arguments.
602 971
603 $grp->cancel_subs 972 $grp->cancel_subs
604 Cancel all subrequests and clears any feeder, but not the group 973 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 974 request itself. Useful when you queued a lot of events but got a
606 result early. 975 result early.
607 976
977 The group request will finish normally (you cannot add requests to
978 the group).
979
608 $grp->result (...) 980 $grp->result (...)
609 Set the result value(s) that will be passed to the group 981 Set the result value(s) that will be passed to the group callback
610 callback when all subrequests have finished and set thre groups 982 when all subrequests have finished and set the groups errno to the
611 errno to the current value of errno (just like calling "errno" 983 current value of errno (just like calling "errno" without an error
612 without an error number). By default, no argument will be passed 984 number). By default, no argument will be passed and errno is zero.
613 and errno is zero.
614 985
615 $grp->errno ([$errno]) 986 $grp->errno ([$errno])
616 Sets the group errno value to $errno, or the current value of 987 Sets the group errno value to $errno, or the current value of errno
617 errno when the argument is missing. 988 when the argument is missing.
618 989
619 Every aio request has an associated errno value that is restored 990 Every aio request has an associated errno value that is restored
620 when the callback is invoked. This method lets you change this 991 when the callback is invoked. This method lets you change this value
621 value from its default (0). 992 from its default (0).
622 993
623 Calling "result" will also set errno, so make sure you either 994 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. 995 before the call to "result", or call c<errno> after it.
625 996
626 feed $grp $callback->($grp) 997 feed $grp $callback->($grp)
627 Sets a feeder/generator on this group: every group can have an 998 Sets a feeder/generator on this group: every group can have an
628 attached generator that generates requests if idle. The idea 999 attached generator that generates requests if idle. The idea behind
629 behind this is that, although you could just queue as many 1000 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 1001 want in a group, this might starve other requests for a potentially
631 requests for a potentially long time. For example, "aio_scandir" 1002 long time. For example, "aio_scandir" might generate hundreds of
632 might generate hundreds of thousands "aio_stat" requests, 1003 thousands "aio_stat" requests, delaying any later requests for a
633 delaying any later requests for a long time. 1004 long time.
634 1005
635 To avoid this, and allow incremental generation of requests, you 1006 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 1007 instead a group and set a feeder on it that generates those
637 requests. The feed callback will be called whenever there are 1008 requests. The feed callback will be called whenever there are few
638 few enough (see "limit", below) requests active in the group 1009 enough (see "limit", below) requests active in the group itself and
639 itself and is expected to queue more requests. 1010 is expected to queue more requests.
640 1011
641 The feed callback can queue as many requests as it likes (i.e. 1012 The feed callback can queue as many requests as it likes (i.e. "add"
642 "add" does not impose any limits). 1013 does not impose any limits).
643 1014
644 If the feed does not queue more requests when called, it will be 1015 If the feed does not queue more requests when called, it will be
645 automatically removed from the group. 1016 automatically removed from the group.
646 1017
647 If the feed limit is 0, it will be set to 2 automatically. 1018 If the feed limit is 0 when this method is called, it will be set to
1019 2 automatically.
648 1020
649 Example: 1021 Example:
650 1022
651 # stat all files in @files, but only ever use four aio requests concurrently: 1023 # stat all files in @files, but only ever use four aio requests concurrently:
652 1024
653 my $grp = aio_group sub { print "finished\n" }; 1025 my $grp = aio_group sub { print "finished\n" };
654 limit $grp 4; 1026 limit $grp 4;
655 feed $grp sub { 1027 feed $grp sub {
656 my $file = pop @files 1028 my $file = pop @files
657 or return; 1029 or return;
658 1030
659 add $grp aio_stat $file, sub { ... }; 1031 add $grp aio_stat $file, sub { ... };
660 }; 1032 };
661 1033
662 limit $grp $num 1034 limit $grp $num
663 Sets the feeder limit for the group: The feeder will be called 1035 Sets the feeder limit for the group: The feeder will be called
664 whenever the group contains less than this many requests. 1036 whenever the group contains less than this many requests.
665 1037
666 Setting the limit to 0 will pause the feeding process. 1038 Setting the limit to 0 will pause the feeding process.
1039
1040 The default value for the limit is 0, but note that setting a feeder
1041 automatically bumps it up to 2.
667 1042
668 SUPPORT FUNCTIONS 1043 SUPPORT FUNCTIONS
669 EVENT PROCESSING AND EVENT LOOP INTEGRATION 1044 EVENT PROCESSING AND EVENT LOOP INTEGRATION
670 $fileno = IO::AIO::poll_fileno 1045 $fileno = IO::AIO::poll_fileno
671 Return the *request result pipe file descriptor*. This 1046 Return the *request result pipe file descriptor*. This filehandle
672 filehandle must be polled for reading by some mechanism outside 1047 must be polled for reading by some mechanism outside this module
673 this module (e.g. Event or select, see below or the SYNOPSIS). 1048 (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 1049 pipe becomes readable you have to call "poll_cb" to check the
675 the results. 1050 results.
676 1051
677 See "poll_cb" for an example. 1052 See "poll_cb" for an example.
678 1053
679 IO::AIO::poll_cb 1054 IO::AIO::poll_cb
680 Process some outstanding events on the result pipe. You have to 1055 Process some outstanding events on the result pipe. You have to call
681 call this regularly. Returns the number of events processed. 1056 this regularly. Returns 0 if all events could be processed (or there
1057 were no events to process), or -1 if it returned earlier for
682 Returns immediately when no events are outstanding. The amount 1058 whatever reason. Returns immediately when no events are outstanding.
683 of events processed depends on the settings of 1059 The amount of events processed depends on the settings of
684 "IO::AIO::max_poll_req" and "IO::AIO::max_poll_time". 1060 "IO::AIO::max_poll_req" and "IO::AIO::max_poll_time".
685 1061
686 If not all requests were processed for whatever reason, the 1062 If not all requests were processed for whatever reason, the
687 filehandle will still be ready when "poll_cb" returns. 1063 filehandle will still be ready when "poll_cb" returns, so normally
1064 you don't have to do anything special to have it called later.
688 1065
1066 Apart from calling "IO::AIO::poll_cb" when the event filehandle
1067 becomes ready, it can be beneficial to call this function from loops
1068 which submit a lot of requests, to make sure the results get
1069 processed when they become available and not just when the loop is
1070 finished and the event loop takes over again. This function returns
1071 very fast when there are no outstanding requests.
1072
689 Example: Install an Event watcher that automatically calls 1073 Example: Install an Event watcher that automatically calls
690 IO::AIO::poll_cb with high priority: 1074 IO::AIO::poll_cb with high priority (more examples can be found in
1075 the SYNOPSIS section, at the top of this document):
691 1076
692 Event->io (fd => IO::AIO::poll_fileno, 1077 Event->io (fd => IO::AIO::poll_fileno,
693 poll => 'r', async => 1, 1078 poll => 'r', async => 1,
694 cb => \&IO::AIO::poll_cb); 1079 cb => \&IO::AIO::poll_cb);
695 1080
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 1081 IO::AIO::poll_wait
1082 If there are any outstanding requests and none of them in the result
725 Wait till the result filehandle becomes ready for reading 1083 phase, wait till the result filehandle becomes ready for reading
726 (simply does a "select" on the filehandle. This is useful if you 1084 (simply does a "select" on the filehandle. This is useful if you
727 want to synchronously wait for some requests to finish). 1085 want to synchronously wait for some requests to finish).
728 1086
729 See "nreqs" for an example. 1087 See "nreqs" for an example.
730 1088
731 IO::AIO::poll 1089 IO::AIO::poll
732 Waits until some requests have been handled. 1090 Waits until some requests have been handled.
733 1091
1092 Returns the number of requests processed, but is otherwise strictly
734 Strictly equivalent to: 1093 equivalent to:
735 1094
736 IO::AIO::poll_wait, IO::AIO::poll_cb 1095 IO::AIO::poll_wait, IO::AIO::poll_cb
737 if IO::AIO::nreqs;
738 1096
739 IO::AIO::flush 1097 IO::AIO::flush
740 Wait till all outstanding AIO requests have been handled. 1098 Wait till all outstanding AIO requests have been handled.
741 1099
742 Strictly equivalent to: 1100 Strictly equivalent to:
743 1101
744 IO::AIO::poll_wait, IO::AIO::poll_cb 1102 IO::AIO::poll_wait, IO::AIO::poll_cb
745 while IO::AIO::nreqs; 1103 while IO::AIO::nreqs;
1104
1105 IO::AIO::max_poll_reqs $nreqs
1106 IO::AIO::max_poll_time $seconds
1107 These set the maximum number of requests (default 0, meaning
1108 infinity) that are being processed by "IO::AIO::poll_cb" in one
1109 call, respectively the maximum amount of time (default 0, meaning
1110 infinity) spent in "IO::AIO::poll_cb" to process requests (more
1111 correctly the mininum amount of time "poll_cb" is allowed to use).
1112
1113 Setting "max_poll_time" to a non-zero value creates an overhead of
1114 one syscall per request processed, which is not normally a problem
1115 unless your callbacks are really really fast or your OS is really
1116 really slow (I am not mentioning Solaris here). Using
1117 "max_poll_reqs" incurs no overhead.
1118
1119 Setting these is useful if you want to ensure some level of
1120 interactiveness when perl is not fast enough to process all requests
1121 in time.
1122
1123 For interactive programs, values such as 0.01 to 0.1 should be fine.
1124
1125 Example: Install an Event watcher that automatically calls
1126 IO::AIO::poll_cb with low priority, to ensure that other parts of
1127 the program get the CPU sometimes even under high AIO load.
1128
1129 # try not to spend much more than 0.1s in poll_cb
1130 IO::AIO::max_poll_time 0.1;
1131
1132 # use a low priority so other tasks have priority
1133 Event->io (fd => IO::AIO::poll_fileno,
1134 poll => 'r', nice => 1,
1135 cb => &IO::AIO::poll_cb);
746 1136
747 CONTROLLING THE NUMBER OF THREADS 1137 CONTROLLING THE NUMBER OF THREADS
748 IO::AIO::min_parallel $nthreads 1138 IO::AIO::min_parallel $nthreads
749 Set the minimum number of AIO threads to $nthreads. The current 1139 Set the minimum number of AIO threads to $nthreads. The current
750 default is 8, which means eight asynchronous operations can 1140 default is 8, which means eight asynchronous operations can execute
751 execute concurrently at any one time (the number of outstanding 1141 concurrently at any one time (the number of outstanding requests,
752 requests, however, is unlimited). 1142 however, is unlimited).
753 1143
754 IO::AIO starts threads only on demand, when an AIO request is 1144 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 1145 and no free thread exists. Please note that queueing up a hundred
756 hundred requests can create demand for a hundred threads, even 1146 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 1147 out that everything is in the cache and could have been processed
758 been processed faster by a single thread. 1148 faster by a single thread.
759 1149
760 It is recommended to keep the number of threads relatively low, 1150 It is recommended to keep the number of threads relatively low, as
761 as some Linux kernel versions will scale negatively with the 1151 some Linux kernel versions will scale negatively with the number of
762 number of threads (higher parallelity => MUCH higher latency). 1152 threads (higher parallelity => MUCH higher latency). With current
763 With current Linux 2.6 versions, 4-32 threads should be fine. 1153 Linux 2.6 versions, 4-32 threads should be fine.
764 1154
765 Under most circumstances you don't need to call this function, 1155 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 1156 the module selects a default that is suitable for low to moderate
767 moderate load. 1157 load.
768 1158
769 IO::AIO::max_parallel $nthreads 1159 IO::AIO::max_parallel $nthreads
770 Sets the maximum number of AIO threads to $nthreads. If more 1160 Sets the maximum number of AIO threads to $nthreads. If more than
771 than the specified number of threads are currently running, this 1161 the specified number of threads are currently running, this function
772 function kills them. This function blocks until the limit is 1162 kills them. This function blocks until the limit is reached.
773 reached.
774 1163
775 While $nthreads are zero, aio requests get queued but not 1164 While $nthreads are zero, aio requests get queued but not executed
776 executed until the number of threads has been increased again. 1165 until the number of threads has been increased again.
777 1166
778 This module automatically runs "max_parallel 0" at program end, 1167 This module automatically runs "max_parallel 0" at program end, to
779 to ensure that all threads are killed and that there are no 1168 ensure that all threads are killed and that there are no outstanding
780 outstanding requests. 1169 requests.
781 1170
782 Under normal circumstances you don't need to call this function. 1171 Under normal circumstances you don't need to call this function.
783 1172
784 IO::AIO::max_idle $nthreads 1173 IO::AIO::max_idle $nthreads
785 Limit the number of threads (default: 4) that are allowed to 1174 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 1175 (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 1176 timeout (default: 10 seconds). That means if a thread becomes idle
788 other threads are also idle, it will free its resources and 1177 while $nthreads other threads are also idle, it will free its
789 exit. 1178 resources and exit.
790 1179
791 This is useful when you allow a large number of threads (e.g. 1180 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 1181 1000) to allow for extremely high load situations, but want to free
793 want to free resources under normal circumstances (1000 threads 1182 resources under normal circumstances (1000 threads can easily
794 can easily consume 30MB of RAM). 1183 consume 30MB of RAM).
795 1184
796 The default is probably ok in most situations, especially if 1185 The default is probably ok in most situations, especially if thread
797 thread creation is fast. If thread creation is very slow on your 1186 creation is fast. If thread creation is very slow on your system you
798 system you might want to use larger values. 1187 might want to use larger values.
799 1188
1189 IO::AIO::idle_timeout $seconds
1190 Sets the minimum idle timeout (default 10) after which worker
1191 threads are allowed to exit. SEe "IO::AIO::max_idle".
1192
800 $oldmaxreqs = IO::AIO::max_outstanding $maxreqs 1193 IO::AIO::max_outstanding $maxreqs
801 This is a very bad function to use in interactive programs
802 because it blocks, and a bad way to reduce concurrency because
803 it is inexact: Better use an "aio_group" together with a feed
804 callback.
805
806 Sets the maximum number of outstanding requests to $nreqs. If 1194 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 1195 queue up more than this number of requests, the next call to
808 to the "poll_cb" (and "poll_some" and other functions calling 1196 "IO::AIO::poll_cb" (and other functions calling "poll_cb", such as
809 "poll_cb") function will block until the limit is no longer 1197 "IO::AIO::flush" or "IO::AIO::poll") will block until the limit is
810 exceeded. 1198 no longer exceeded.
811 1199
812 The default value is very large, so there is no practical limit 1200 In other words, this setting does not enforce a queue limit, but can
1201 be used to make poll functions block if the limit is exceeded.
1202
1203 This is a very bad function to use in interactive programs because
1204 it blocks, and a bad way to reduce concurrency because it is
1205 inexact: Better use an "aio_group" together with a feed callback.
1206
1207 It's main use is in scripts without an event loop - when you want to
1208 stat a lot of files, you can write somehting like this:
1209
1210 IO::AIO::max_outstanding 32;
1211
1212 for my $path (...) {
1213 aio_stat $path , ...;
1214 IO::AIO::poll_cb;
1215 }
1216
1217 IO::AIO::flush;
1218
1219 The call to "poll_cb" inside the loop will normally return
1220 instantly, but as soon as more thna 32 reqeusts are in-flight, it
1221 will block until some requests have been handled. This keeps the
1222 loop from pushing a large number of "aio_stat" requests onto the
1223 queue.
1224
1225 The default value for "max_outstanding" is very large, so there is
813 on the number of outstanding requests. 1226 no practical limit on the number of outstanding requests.
814
815 You can still queue as many requests as you want. Therefore,
816 "max_oustsanding" is mainly useful in simple scripts (with low
817 values) or as a stop gap to shield against fatal memory overflow
818 (with large values).
819 1227
820 STATISTICAL INFORMATION 1228 STATISTICAL INFORMATION
821 IO::AIO::nreqs 1229 IO::AIO::nreqs
822 Returns the number of requests currently in the ready, execute 1230 Returns the number of requests currently in the ready, execute or
823 or pending states (i.e. for which their callback has not been 1231 pending states (i.e. for which their callback has not been invoked
824 invoked yet). 1232 yet).
825 1233
826 Example: wait till there are no outstanding requests anymore: 1234 Example: wait till there are no outstanding requests anymore:
827 1235
828 IO::AIO::poll_wait, IO::AIO::poll_cb 1236 IO::AIO::poll_wait, IO::AIO::poll_cb
829 while IO::AIO::nreqs; 1237 while IO::AIO::nreqs;
830 1238
831 IO::AIO::nready 1239 IO::AIO::nready
832 Returns the number of requests currently in the ready state (not 1240 Returns the number of requests currently in the ready state (not yet
833 yet executed). 1241 executed).
834 1242
835 IO::AIO::npending 1243 IO::AIO::npending
836 Returns the number of requests currently in the pending state 1244 Returns the number of requests currently in the pending state
837 (executed, but not yet processed by poll_cb). 1245 (executed, but not yet processed by poll_cb).
1246
1247 MISCELLANEOUS FUNCTIONS
1248 IO::AIO implements some functions that might be useful, but are not
1249 asynchronous.
1250
1251 IO::AIO::sendfile $ofh, $ifh, $offset, $count
1252 Calls the "eio_sendfile_sync" function, which is like
1253 "aio_sendfile", but is blocking (this makes most sense if you know
1254 the input data is likely cached already and the output filehandle is
1255 set to non-blocking operations).
1256
1257 Returns the number of bytes copied, or -1 on error.
1258
1259 IO::AIO::fadvise $fh, $offset, $len, $advice
1260 Simply calls the "posix_fadvise" function (see its manpage for
1261 details). The following advice constants are avaiable:
1262 "IO::AIO::FADV_NORMAL", "IO::AIO::FADV_SEQUENTIAL",
1263 "IO::AIO::FADV_RANDOM", "IO::AIO::FADV_NOREUSE",
1264 "IO::AIO::FADV_WILLNEED", "IO::AIO::FADV_DONTNEED".
1265
1266 On systems that do not implement "posix_fadvise", this function
1267 returns ENOSYS, otherwise the return value of "posix_fadvise".
1268
1269 IO::AIO::madvise $scalar, $offset, $len, $advice
1270 Simply calls the "posix_madvise" function (see its manpage for
1271 details). The following advice constants are avaiable:
1272 "IO::AIO::MADV_NORMAL", "IO::AIO::MADV_SEQUENTIAL",
1273 "IO::AIO::MADV_RANDOM", "IO::AIO::MADV_WILLNEED",
1274 "IO::AIO::MADV_DONTNEED".
1275
1276 On systems that do not implement "posix_madvise", this function
1277 returns ENOSYS, otherwise the return value of "posix_madvise".
1278
1279 IO::AIO::mprotect $scalar, $offset, $len, $protect
1280 Simply calls the "mprotect" function on the preferably AIO::mmap'ed
1281 $scalar (see its manpage for details). The following protect
1282 constants are avaiable: "IO::AIO::PROT_NONE", "IO::AIO::PROT_READ",
1283 "IO::AIO::PROT_WRITE", "IO::AIO::PROT_EXEC".
1284
1285 On systems that do not implement "mprotect", this function returns
1286 ENOSYS, otherwise the return value of "mprotect".
1287
1288 IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
1289 Memory-maps a file (or anonymous memory range) and attaches it to
1290 the given $scalar, which will act like a string scalar.
1291
1292 The only operations allowed on the scalar are "substr"/"vec" that
1293 don't change the string length, and most read-only operations such
1294 as copying it or searching it with regexes and so on.
1295
1296 Anything else is unsafe and will, at best, result in memory leaks.
1297
1298 The memory map associated with the $scalar is automatically removed
1299 when the $scalar is destroyed, or when the "IO::AIO::mmap" or
1300 "IO::AIO::munmap" functions are called.
1301
1302 This calls the "mmap"(2) function internally. See your system's
1303 manual page for details on the $length, $prot and $flags parameters.
1304
1305 The $length must be larger than zero and smaller than the actual
1306 filesize.
1307
1308 $prot is a combination of "IO::AIO::PROT_NONE",
1309 "IO::AIO::PROT_EXEC", "IO::AIO::PROT_READ" and/or
1310 "IO::AIO::PROT_WRITE",
1311
1312 $flags can be a combination of "IO::AIO::MAP_SHARED" or
1313 "IO::AIO::MAP_PRIVATE", or a number of system-specific flags (when
1314 not available, the are defined as 0): "IO::AIO::MAP_ANONYMOUS"
1315 (which is set to "MAP_ANON" if your system only provides this
1316 constant), "IO::AIO::MAP_HUGETLB", "IO::AIO::MAP_LOCKED",
1317 "IO::AIO::MAP_NORESERVE", "IO::AIO::MAP_POPULATE" or
1318 "IO::AIO::MAP_NONBLOCK"
1319
1320 If $fh is "undef", then a file descriptor of -1 is passed.
1321
1322 $offset is the offset from the start of the file - it generally must
1323 be a multiple of "IO::AIO::PAGESIZE" and defaults to 0.
1324
1325 Example:
1326
1327 use Digest::MD5;
1328 use IO::AIO;
1329
1330 open my $fh, "<verybigfile"
1331 or die "$!";
1332
1333 IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
1334 or die "verybigfile: $!";
1335
1336 my $fast_md5 = md5 $data;
1337
1338 IO::AIO::munmap $scalar
1339 Removes a previous mmap and undefines the $scalar.
1340
1341 IO::AIO::munlock $scalar, $offset = 0, $length = undef
1342 Calls the "munlock" function, undoing the effects of a previous
1343 "aio_mlock" call (see its description for details).
1344
1345 IO::AIO::munlockall
1346 Calls the "munlockall" function.
1347
1348 On systems that do not implement "munlockall", this function returns
1349 ENOSYS, otherwise the return value of "munlockall".
1350
1351EVENT LOOP INTEGRATION
1352 It is recommended to use AnyEvent::AIO to integrate IO::AIO
1353 automatically into many event loops:
1354
1355 # AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
1356 use AnyEvent::AIO;
1357
1358 You can also integrate IO::AIO manually into many event loops, here are
1359 some examples of how to do this:
1360
1361 # EV integration
1362 my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
1363
1364 # Event integration
1365 Event->io (fd => IO::AIO::poll_fileno,
1366 poll => 'r',
1367 cb => \&IO::AIO::poll_cb);
1368
1369 # Glib/Gtk2 integration
1370 add_watch Glib::IO IO::AIO::poll_fileno,
1371 in => sub { IO::AIO::poll_cb; 1 };
1372
1373 # Tk integration
1374 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
1375 readable => \&IO::AIO::poll_cb);
1376
1377 # Danga::Socket integration
1378 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
1379 \&IO::AIO::poll_cb);
838 1380
839 FORK BEHAVIOUR 1381 FORK BEHAVIOUR
840 This module should do "the right thing" when the process using it 1382 Usage of pthreads in a program changes the semantics of fork
841 forks: 1383 considerably. Specifically, only async-safe functions can be called
1384 after fork. Perl doesn't know about this, so in general, you cannot call
1385 fork with defined behaviour in perl if pthreads are involved. IO::AIO
1386 uses pthreads, so this applies, but many other extensions and (for
1387 inexplicable reasons) perl itself often is linked against pthreads, so
1388 this limitation applies to quite a lot of perls.
842 1389
843 Before the fork, IO::AIO enters a quiescent state where no requests 1390 This module no longer tries to fight your OS, or POSIX. That means
844 can be added in other threads and no results will be processed. 1391 IO::AIO only works in the process that loaded it. Forking is fully
845 After the fork the parent simply leaves the quiescent state and 1392 supported, but using IO::AIO in the child is not.
846 continues request/result processing, while the child frees the
847 request/result queue (so that the requests started before the fork
848 will only be handled in the parent). Threads will be started on
849 demand until the limit set in the parent process has been reached
850 again.
851 1393
852 In short: the parent will, after a short pause, continue as if fork 1394 You might get around by not *using* IO::AIO before (or after) forking.
853 had not been called, while the child will act as if IO::AIO has not 1395 You could also try to call the IO::AIO::reinit function in the child:
854 been used yet. 1396
1397 IO::AIO::reinit
1398 Abondons all current requests and I/O threads and simply
1399 reinitialises all data structures. This is not an operation
1400 suppported by any standards, but happens to work on GNU/Linux and
1401 some newer BSD systems.
1402
1403 The only reasonable use for this function is to call it after
1404 forking, if "IO::AIO" was used in the parent. Calling it while
1405 IO::AIO is active in the process will result in undefined behaviour.
1406 Calling it at any time will also result in any undefined (by POSIX)
1407 behaviour.
855 1408
856 MEMORY USAGE 1409 MEMORY USAGE
857 Per-request usage: 1410 Per-request usage:
858 1411
859 Each aio request uses - depending on your architecture - around 1412 Each aio request uses - depending on your architecture - around 100-200
860 100-200 bytes of memory. In addition, stat requests need a stat 1413 bytes of memory. In addition, stat requests need a stat buffer (possibly
861 buffer (possibly a few hundred bytes), readdir requires a result 1414 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 1415 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 1416 will consume memory till the request has entered the done state.
864 request has entered the done state.
865 1417
866 This is now awfully much, so queuing lots of requests is not usually 1418 This is not awfully much, so queuing lots of requests is not usually a
867 a problem. 1419 problem.
868 1420
869 Per-thread usage: 1421 Per-thread usage:
870 1422
871 In the execution phase, some aio requests require more memory for 1423 In the execution phase, some aio requests require more memory for
872 temporary buffers, and each thread requires a stack and other data 1424 temporary buffers, and each thread requires a stack and other data
873 structures (usually around 16k-128k, depending on the OS). 1425 structures (usually around 16k-128k, depending on the OS).
874 1426
875KNOWN BUGS 1427KNOWN BUGS
876 Known bugs will be fixed in the next release. 1428 Known bugs will be fixed in the next release.
877 1429
878SEE ALSO 1430SEE ALSO
879 Coro::AIO. 1431 AnyEvent::AIO for easy integration into event loops, Coro::AIO for a
1432 more natural syntax.
880 1433
881AUTHOR 1434AUTHOR
882 Marc Lehmann <schmorp@schmorp.de> 1435 Marc Lehmann <schmorp@schmorp.de>
883 http://home.schmorp.de/ 1436 http://home.schmorp.de/
884 1437

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