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Revision 1.57 by root, Mon Jan 18 11:53:09 2016 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;
89 use Event; 69 use EV;
90 use IO::AIO; 70 use IO::AIO;
91 71
92 # register the IO::AIO callback with Event 72 # register the IO::AIO callback with EV
93 Event->io (fd => IO::AIO::poll_fileno, 73 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 74
97 # queue the request to open /etc/passwd 75 # queue the request to open /etc/passwd
98 aio_open "/etc/passwd", O_RDONLY, 0, sub { 76 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
99 my $fh = $_[0] 77 my $fh = shift
100 or die "error while opening: $!"; 78 or die "error while opening: $!";
101 79
102 # stat'ing filehandles is generally non-blocking 80 # stat'ing filehandles is generally non-blocking
103 my $size = -s $fh; 81 my $size = -s $fh;
104 82
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112 90
113 # file contents now in $contents 91 # file contents now in $contents
114 print $contents; 92 print $contents;
115 93
116 # exit event loop and program 94 # exit event loop and program
117 Event::unloop; 95 EV::break;
118 }; 96 };
119 }; 97 };
120 98
121 # possibly queue up other requests, or open GUI windows, 99 # possibly queue up other requests, or open GUI windows,
122 # check for sockets etc. etc. 100 # check for sockets etc. etc.
123 101
124 # process events as long as there are some: 102 # process events as long as there are some:
125 Event::loop; 103 EV::run;
126 104
127REQUEST ANATOMY AND LIFETIME 105REQUEST ANATOMY AND LIFETIME
128 Every "aio_*" function creates a request. which is a C data structure 106 Every "aio_*" function creates a request. which is a C data structure
129 not directly visible to Perl. 107 not directly visible to Perl.
130 108
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166 anymore (except possibly for the Perl object, but its connection to 144 anymore (except possibly for the Perl object, but its connection to
167 the actual aio request is severed and calling its methods will 145 the actual aio request is severed and calling its methods will
168 either do nothing or result in a runtime error). 146 either do nothing or result in a runtime error).
169 147
170FUNCTIONS 148FUNCTIONS
149 QUICK OVERVIEW
150 This section simply lists the prototypes most of the functions for quick
151 reference. See the following sections for function-by-function
152 documentation.
153
154 aio_wd $pathname, $callback->($wd)
155 aio_open $pathname, $flags, $mode, $callback->($fh)
156 aio_close $fh, $callback->($status)
157 aio_seek $fh,$offset,$whence, $callback->($offs)
158 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
159 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
160 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
161 aio_readahead $fh,$offset,$length, $callback->($retval)
162 aio_stat $fh_or_path, $callback->($status)
163 aio_lstat $fh, $callback->($status)
164 aio_statvfs $fh_or_path, $callback->($statvfs)
165 aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
166 aio_chown $fh_or_path, $uid, $gid, $callback->($status)
167 aio_chmod $fh_or_path, $mode, $callback->($status)
168 aio_truncate $fh_or_path, $offset, $callback->($status)
169 aio_allocate $fh, $mode, $offset, $len, $callback->($status)
170 aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
171 aio_unlink $pathname, $callback->($status)
172 aio_mknod $pathname, $mode, $dev, $callback->($status)
173 aio_link $srcpath, $dstpath, $callback->($status)
174 aio_symlink $srcpath, $dstpath, $callback->($status)
175 aio_readlink $pathname, $callback->($link)
176 aio_realpath $pathname, $callback->($path)
177 aio_rename $srcpath, $dstpath, $callback->($status)
178 aio_mkdir $pathname, $mode, $callback->($status)
179 aio_rmdir $pathname, $callback->($status)
180 aio_readdir $pathname, $callback->($entries)
181 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
182 IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
183 IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
184 aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
185 aio_load $pathname, $data, $callback->($status)
186 aio_copy $srcpath, $dstpath, $callback->($status)
187 aio_move $srcpath, $dstpath, $callback->($status)
188 aio_rmtree $pathname, $callback->($status)
189 aio_sync $callback->($status)
190 aio_syncfs $fh, $callback->($status)
191 aio_fsync $fh, $callback->($status)
192 aio_fdatasync $fh, $callback->($status)
193 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
194 aio_pathsync $pathname, $callback->($status)
195 aio_msync $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
196 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
197 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
198 aio_mlockall $flags, $callback->($status)
199 aio_group $callback->(...)
200 aio_nop $callback->()
201
202 $prev_pri = aioreq_pri [$pri]
203 aioreq_nice $pri_adjust
204
205 IO::AIO::poll_wait
206 IO::AIO::poll_cb
207 IO::AIO::poll
208 IO::AIO::flush
209 IO::AIO::max_poll_reqs $nreqs
210 IO::AIO::max_poll_time $seconds
211 IO::AIO::min_parallel $nthreads
212 IO::AIO::max_parallel $nthreads
213 IO::AIO::max_idle $nthreads
214 IO::AIO::idle_timeout $seconds
215 IO::AIO::max_outstanding $maxreqs
216 IO::AIO::nreqs
217 IO::AIO::nready
218 IO::AIO::npending
219
220 IO::AIO::sendfile $ofh, $ifh, $offset, $count
221 IO::AIO::fadvise $fh, $offset, $len, $advice
222 IO::AIO::mmap $scalar, $length, $prot, $flags[, $fh[, $offset]]
223 IO::AIO::munmap $scalar
224 IO::AIO::madvise $scalar, $offset, $length, $advice
225 IO::AIO::mprotect $scalar, $offset, $length, $protect
226 IO::AIO::munlock $scalar, $offset = 0, $length = undef
227 IO::AIO::munlockall
228
229 API NOTES
230 All the "aio_*" calls are more or less thin wrappers around the syscall
231 with the same name (sans "aio_"). The arguments are similar or
232 identical, and they all accept an additional (and optional) $callback
233 argument which must be a code reference. This code reference will be
234 called after the syscall has been executed in an asynchronous fashion.
235 The results of the request will be passed as arguments to the callback
236 (and, if an error occured, in $!) - for most requests the syscall return
237 code (e.g. most syscalls return -1 on error, unlike perl, which usually
238 delivers "false").
239
240 Some requests (such as "aio_readdir") pass the actual results and
241 communicate failures by passing "undef".
242
243 All functions expecting a filehandle keep a copy of the filehandle
244 internally until the request has finished.
245
246 All functions return request objects of type IO::AIO::REQ that allow
247 further manipulation of those requests while they are in-flight.
248
249 The pathnames you pass to these routines *should* be absolute. The
250 reason for this is that at the time the request is being executed, the
251 current working directory could have changed. Alternatively, you can
252 make sure that you never change the current working directory anywhere
253 in the program and then use relative paths. You can also take advantage
254 of IO::AIOs working directory abstraction, that lets you specify paths
255 relative to some previously-opened "working directory object" - see the
256 description of the "IO::AIO::WD" class later in this document.
257
258 To encode pathnames as octets, either make sure you either: a) always
259 pass in filenames you got from outside (command line, readdir etc.)
260 without tinkering, b) are in your native filesystem encoding, c) use the
261 Encode module and encode your pathnames to the locale (or other)
262 encoding in effect in the user environment, d) use
263 Glib::filename_from_unicode on unicode filenames or e) use something
264 else to ensure your scalar has the correct contents.
265
266 This works, btw. independent of the internal UTF-8 bit, which IO::AIO
267 handles correctly whether it is set or not.
268
171 AIO REQUEST FUNCTIONS 269 AIO REQUEST FUNCTIONS
172 All the "aio_*" calls are more or less thin wrappers around the
173 syscall with the same name (sans "aio_"). The arguments are similar
174 or identical, and they all accept an additional (and optional)
175 $callback argument which must be a code reference. This code
176 reference will get called with the syscall return code (e.g. most
177 syscalls return -1 on error, unlike perl, which usually delivers
178 "false") as it's sole argument when the given syscall has been
179 executed asynchronously.
180
181 All functions expecting a filehandle keep a copy of the filehandle
182 internally until the request has finished.
183
184 All functions return request objects of type IO::AIO::REQ that allow
185 further manipulation of those requests while they are in-flight.
186
187 The pathnames you pass to these routines *must* be absolute and
188 encoded as octets. The reason for the former is that at the time the
189 request is being executed, the current working directory could have
190 changed. Alternatively, you can make sure that you never change the
191 current working directory anywhere in the program and then use
192 relative paths.
193
194 To encode pathnames as octets, either make sure you either: a)
195 always pass in filenames you got from outside (command line, readdir
196 etc.) without tinkering, b) are ASCII or ISO 8859-1, c) use the
197 Encode module and encode your pathnames to the locale (or other)
198 encoding in effect in the user environment, d) use
199 Glib::filename_from_unicode on unicode filenames or e) use something
200 else to ensure your scalar has the correct contents.
201
202 This works, btw. independent of the internal UTF-8 bit, which
203 IO::AIO handles correctly wether it is set or not.
204
205 $prev_pri = aioreq_pri [$pri] 270 $prev_pri = aioreq_pri [$pri]
206 Returns the priority value that would be used for the next 271 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 272 and, if $pri is given, sets the priority for the next aio request.
208 aio request.
209 273
210 The default priority is 0, the minimum and maximum priorities 274 The default priority is 0, the minimum and maximum priorities are -4
211 are -4 and 4, respectively. Requests with higher priority will 275 and 4, respectively. Requests with higher priority will be serviced
212 be serviced first. 276 first.
213 277
214 The priority will be reset to 0 after each call to one of the 278 The priority will be reset to 0 after each call to one of the
215 "aio_*" functions. 279 "aio_*" functions.
216 280
217 Example: open a file with low priority, then read something from 281 Example: open a file with low priority, then read something from it
218 it with higher priority so the read request is serviced before 282 with higher priority so the read request is serviced before other
219 other low priority open requests (potentially spamming the 283 low priority open requests (potentially spamming the cache):
220 cache):
221 284
285 aioreq_pri -3;
286 aio_open ..., sub {
287 return unless $_[0];
288
222 aioreq_pri -3; 289 aioreq_pri -2;
223 aio_open ..., sub {
224 return unless $_[0];
225
226 aioreq_pri -2;
227 aio_read $_[0], ..., sub { 290 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 ...; 291 ...
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 }; 292 };
571 }; 293 };
572 294
295 aioreq_nice $pri_adjust
296 Similar to "aioreq_pri", but subtracts the given value from the
297 current priority, so the effect is cumulative.
298
299 aio_open $pathname, $flags, $mode, $callback->($fh)
300 Asynchronously open or create a file and call the callback with a
301 newly created filehandle for the file (or "undef" in case of an
302 error).
303
304 The pathname passed to "aio_open" must be absolute. See API NOTES,
305 above, for an explanation.
306
307 The $flags argument is a bitmask. See the "Fcntl" module for a list.
308 They are the same as used by "sysopen".
309
310 Likewise, $mode specifies the mode of the newly created file, if it
311 didn't exist and "O_CREAT" has been given, just like perl's
312 "sysopen", except that it is mandatory (i.e. use 0 if you don't
313 create new files, and 0666 or 0777 if you do). Note that the $mode
314 will be modified by the umask in effect then the request is being
315 executed, so better never change the umask.
316
317 Example:
318
319 aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
320 if ($_[0]) {
321 print "open successful, fh is $_[0]\n";
322 ...
323 } else {
324 die "open failed: $!\n";
325 }
326 };
327
328 In addition to all the common open modes/flags ("O_RDONLY",
329 "O_WRONLY", "O_RDWR", "O_CREAT", "O_TRUNC", "O_EXCL" and
330 "O_APPEND"), the following POSIX and non-POSIX constants are
331 available (missing ones on your system are, as usual, 0):
332
333 "O_ASYNC", "O_DIRECT", "O_NOATIME", "O_CLOEXEC", "O_NOCTTY",
334 "O_NOFOLLOW", "O_NONBLOCK", "O_EXEC", "O_SEARCH", "O_DIRECTORY",
335 "O_DSYNC", "O_RSYNC", "O_SYNC", "O_PATH", "O_TMPFILE", and
336 "O_TTY_INIT".
337
338 aio_close $fh, $callback->($status)
339 Asynchronously close a file and call the callback with the result
340 code.
341
342 Unfortunately, you can't do this to perl. Perl *insists* very
343 strongly on closing the file descriptor associated with the
344 filehandle itself.
345
346 Therefore, "aio_close" will not close the filehandle - instead it
347 will use dup2 to overwrite the file descriptor with the write-end of
348 a pipe (the pipe fd will be created on demand and will be cached).
349
350 Or in other words: the file descriptor will be closed, but it will
351 not be free for reuse until the perl filehandle is closed.
352
353 aio_seek $fh, $offset, $whence, $callback->($offs)
354 Seeks the filehandle to the new $offset, similarly to perl's
355 "sysseek". The $whence can use the traditional values (0 for
356 "IO::AIO::SEEK_SET", 1 for "IO::AIO::SEEK_CUR" or 2 for
357 "IO::AIO::SEEK_END").
358
359 The resulting absolute offset will be passed to the callback, or -1
360 in case of an error.
361
362 In theory, the $whence constants could be different than the
363 corresponding values from Fcntl, but perl guarantees they are the
364 same, so don't panic.
365
366 As a GNU/Linux (and maybe Solaris) extension, also the constants
367 "IO::AIO::SEEK_DATA" and "IO::AIO::SEEK_HOLE" are available, if they
368 could be found. No guarantees about suitability for use in
369 "aio_seek" or Perl's "sysseek" can be made though, although I would
370 naively assume they "just work".
371
372 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
373 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
374 Reads or writes $length bytes from or to the specified $fh and
375 $offset into the scalar given by $data and offset $dataoffset and
376 calls the callback without the actual number of bytes read (or -1 on
377 error, just like the syscall).
378
379 "aio_read" will, like "sysread", shrink or grow the $data scalar to
380 offset plus the actual number of bytes read.
381
382 If $offset is undefined, then the current file descriptor offset
383 will be used (and updated), otherwise the file descriptor offset
384 will not be changed by these calls.
385
386 If $length is undefined in "aio_write", use the remaining length of
387 $data.
388
389 If $dataoffset is less than zero, it will be counted from the end of
390 $data.
391
392 The $data scalar *MUST NOT* be modified in any way while the request
393 is outstanding. Modifying it can result in segfaults or World War
394 III (if the necessary/optional hardware is installed).
395
396 Example: Read 15 bytes at offset 7 into scalar $buffer, starting at
397 offset 0 within the scalar:
398
399 aio_read $fh, 7, 15, $buffer, 0, sub {
400 $_[0] > 0 or die "read error: $!";
401 print "read $_[0] bytes: <$buffer>\n";
402 };
403
404 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
405 Tries to copy $length bytes from $in_fh to $out_fh. It starts
406 reading at byte offset $in_offset, and starts writing at the current
407 file offset of $out_fh. Because of that, it is not safe to issue
408 more than one "aio_sendfile" per $out_fh, as they will interfere
409 with each other. The same $in_fh works fine though, as this function
410 does not move or use the file offset of $in_fh.
411
412 Please note that "aio_sendfile" can read more bytes from $in_fh than
413 are written, and there is no way to find out how many more bytes
414 have been read from "aio_sendfile" alone, as "aio_sendfile" only
415 provides the number of bytes written to $out_fh. Only if the result
416 value equals $length one can assume that $length bytes have been
417 read.
418
419 Unlike with other "aio_" functions, it makes a lot of sense to use
420 "aio_sendfile" on non-blocking sockets, as long as one end
421 (typically the $in_fh) is a file - the file I/O will then be
422 asynchronous, while the socket I/O will be non-blocking. Note,
423 however, that you can run into a trap where "aio_sendfile" reads
424 some data with readahead, then fails to write all data, and when the
425 socket is ready the next time, the data in the cache is already
426 lost, forcing "aio_sendfile" to again hit the disk. Explicit
427 "aio_read" + "aio_write" let's you better control resource usage.
428
429 This call tries to make use of a native "sendfile"-like syscall to
430 provide zero-copy operation. For this to work, $out_fh should refer
431 to a socket, and $in_fh should refer to an mmap'able file.
432
433 If a native sendfile cannot be found or it fails with "ENOSYS",
434 "EINVAL", "ENOTSUP", "EOPNOTSUPP", "EAFNOSUPPORT", "EPROTOTYPE" or
435 "ENOTSOCK", it will be emulated, so you can call "aio_sendfile" on
436 any type of filehandle regardless of the limitations of the
437 operating system.
438
439 As native sendfile syscalls (as practically any non-POSIX interface
440 hacked together in a hurry to improve benchmark numbers) tend to be
441 rather buggy on many systems, this implementation tries to work
442 around some known bugs in Linux and FreeBSD kernels (probably
443 others, too), but that might fail, so you really really should check
444 the return value of "aio_sendfile" - fewre bytes than expected might
445 have been transferred.
446
447 aio_readahead $fh,$offset,$length, $callback->($retval)
448 "aio_readahead" populates the page cache with data from a file so
449 that subsequent reads from that file will not block on disk I/O. The
450 $offset argument specifies the starting point from which data is to
451 be read and $length specifies the number of bytes to be read. I/O is
452 performed in whole pages, so that offset is effectively rounded down
453 to a page boundary and bytes are read up to the next page boundary
454 greater than or equal to (off-set+length). "aio_readahead" does not
455 read beyond the end of the file. The current file offset of the file
456 is left unchanged.
457
458 If that syscall doesn't exist (likely if your OS isn't Linux) it
459 will be emulated by simply reading the data, which would have a
460 similar effect.
461
462 aio_stat $fh_or_path, $callback->($status)
463 aio_lstat $fh, $callback->($status)
464 Works like perl's "stat" or "lstat" in void context. The callback
465 will be called after the stat and the results will be available
466 using "stat _" or "-s _" etc...
467
468 The pathname passed to "aio_stat" must be absolute. See API NOTES,
469 above, for an explanation.
470
471 Currently, the stats are always 64-bit-stats, i.e. instead of
472 returning an error when stat'ing a large file, the results will be
473 silently truncated unless perl itself is compiled with large file
474 support.
475
476 To help interpret the mode and dev/rdev stat values, IO::AIO offers
477 the following constants and functions (if not implemented, the
478 constants will be 0 and the functions will either "croak" or fall
479 back on traditional behaviour).
480
481 "S_IFMT", "S_IFIFO", "S_IFCHR", "S_IFBLK", "S_IFLNK", "S_IFREG",
482 "S_IFDIR", "S_IFWHT", "S_IFSOCK", "IO::AIO::major $dev_t",
483 "IO::AIO::minor $dev_t", "IO::AIO::makedev $major, $minor".
484
485 Example: Print the length of /etc/passwd:
486
487 aio_stat "/etc/passwd", sub {
488 $_[0] and die "stat failed: $!";
489 print "size is ", -s _, "\n";
490 };
491
492 aio_statvfs $fh_or_path, $callback->($statvfs)
493 Works like the POSIX "statvfs" or "fstatvfs" syscalls, depending on
494 whether a file handle or path was passed.
495
496 On success, the callback is passed a hash reference with the
497 following members: "bsize", "frsize", "blocks", "bfree", "bavail",
498 "files", "ffree", "favail", "fsid", "flag" and "namemax". On
499 failure, "undef" is passed.
500
501 The following POSIX IO::AIO::ST_* constants are defined: "ST_RDONLY"
502 and "ST_NOSUID".
503
504 The following non-POSIX IO::AIO::ST_* flag masks are defined to
505 their correct value when available, or to 0 on systems that do not
506 support them: "ST_NODEV", "ST_NOEXEC", "ST_SYNCHRONOUS",
507 "ST_MANDLOCK", "ST_WRITE", "ST_APPEND", "ST_IMMUTABLE",
508 "ST_NOATIME", "ST_NODIRATIME" and "ST_RELATIME".
509
510 Example: stat "/wd" and dump out the data if successful.
511
512 aio_statvfs "/wd", sub {
513 my $f = $_[0]
514 or die "statvfs: $!";
515
516 use Data::Dumper;
517 say Dumper $f;
518 };
519
520 # result:
521 {
522 bsize => 1024,
523 bfree => 4333064312,
524 blocks => 10253828096,
525 files => 2050765568,
526 flag => 4096,
527 favail => 2042092649,
528 bavail => 4333064312,
529 ffree => 2042092649,
530 namemax => 255,
531 frsize => 1024,
532 fsid => 1810
533 }
534
535 Here is a (likely partial - send me updates!) list of fsid values
536 used by Linux - it is safe to hardcode these when $^O is "linux":
537
538 0x0000adf5 adfs
539 0x0000adff affs
540 0x5346414f afs
541 0x09041934 anon-inode filesystem
542 0x00000187 autofs
543 0x42465331 befs
544 0x1badface bfs
545 0x42494e4d binfmt_misc
546 0x9123683e btrfs
547 0x0027e0eb cgroupfs
548 0xff534d42 cifs
549 0x73757245 coda
550 0x012ff7b7 coh
551 0x28cd3d45 cramfs
552 0x453dcd28 cramfs-wend (wrong endianness)
553 0x64626720 debugfs
554 0x00001373 devfs
555 0x00001cd1 devpts
556 0x0000f15f ecryptfs
557 0x00414a53 efs
558 0x0000137d ext
559 0x0000ef53 ext2/ext3/ext4
560 0x0000ef51 ext2
561 0xf2f52010 f2fs
562 0x00004006 fat
563 0x65735546 fuseblk
564 0x65735543 fusectl
565 0x0bad1dea futexfs
566 0x01161970 gfs2
567 0x47504653 gpfs
568 0x00004244 hfs
569 0xf995e849 hpfs
570 0x00c0ffee hostfs
571 0x958458f6 hugetlbfs
572 0x2bad1dea inotifyfs
573 0x00009660 isofs
574 0x000072b6 jffs2
575 0x3153464a jfs
576 0x6b414653 k-afs
577 0x0bd00bd0 lustre
578 0x0000137f minix
579 0x0000138f minix 30 char names
580 0x00002468 minix v2
581 0x00002478 minix v2 30 char names
582 0x00004d5a minix v3
583 0x19800202 mqueue
584 0x00004d44 msdos
585 0x0000564c novell
586 0x00006969 nfs
587 0x6e667364 nfsd
588 0x00003434 nilfs
589 0x5346544e ntfs
590 0x00009fa1 openprom
591 0x7461636F ocfs2
592 0x00009fa0 proc
593 0x6165676c pstorefs
594 0x0000002f qnx4
595 0x68191122 qnx6
596 0x858458f6 ramfs
597 0x52654973 reiserfs
598 0x00007275 romfs
599 0x67596969 rpc_pipefs
600 0x73636673 securityfs
601 0xf97cff8c selinux
602 0x0000517b smb
603 0x534f434b sockfs
604 0x73717368 squashfs
605 0x62656572 sysfs
606 0x012ff7b6 sysv2
607 0x012ff7b5 sysv4
608 0x01021994 tmpfs
609 0x15013346 udf
610 0x00011954 ufs
611 0x54190100 ufs byteswapped
612 0x00009fa2 usbdevfs
613 0x01021997 v9fs
614 0xa501fcf5 vxfs
615 0xabba1974 xenfs
616 0x012ff7b4 xenix
617 0x58465342 xfs
618 0x012fd16d xia
619
620 aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
621 Works like perl's "utime" function (including the special case of
622 $atime and $mtime being undef). Fractional times are supported if
623 the underlying syscalls support them.
624
625 When called with a pathname, uses utimes(2) if available, otherwise
626 utime(2). If called on a file descriptor, uses futimes(2) if
627 available, otherwise returns ENOSYS, so this is not portable.
628
629 Examples:
630
631 # set atime and mtime to current time (basically touch(1)):
632 aio_utime "path", undef, undef;
633 # set atime to current time and mtime to beginning of the epoch:
634 aio_utime "path", time, undef; # undef==0
635
636 aio_chown $fh_or_path, $uid, $gid, $callback->($status)
637 Works like perl's "chown" function, except that "undef" for either
638 $uid or $gid is being interpreted as "do not change" (but -1 can
639 also be used).
640
641 Examples:
642
643 # same as "chown root path" in the shell:
644 aio_chown "path", 0, -1;
645 # same as above:
646 aio_chown "path", 0, undef;
647
648 aio_truncate $fh_or_path, $offset, $callback->($status)
649 Works like truncate(2) or ftruncate(2).
650
651 aio_allocate $fh, $mode, $offset, $len, $callback->($status)
652 Allocates or frees disk space according to the $mode argument. See
653 the linux "fallocate" documentation for details.
654
655 $mode is usually 0 or "IO::AIO::FALLOC_FL_KEEP_SIZE" to allocate
656 space, or "IO::AIO::FALLOC_FL_PUNCH_HOLE |
657 IO::AIO::FALLOC_FL_KEEP_SIZE", to deallocate a file range.
658
659 IO::AIO also supports "FALLOC_FL_COLLAPSE_RANGE", to remove a range
660 (without leaving a hole) and "FALLOC_FL_ZERO_RANGE", to zero a range
661 (see your fallocate(2) manpage).
662
663 The file system block size used by "fallocate" is presumably the
664 "f_bsize" returned by "statvfs".
665
666 If "fallocate" isn't available or cannot be emulated (currently no
667 emulation will be attempted), passes -1 and sets $! to "ENOSYS".
668
669 aio_chmod $fh_or_path, $mode, $callback->($status)
670 Works like perl's "chmod" function.
671
672 aio_unlink $pathname, $callback->($status)
673 Asynchronously unlink (delete) a file and call the callback with the
674 result code.
675
676 aio_mknod $pathname, $mode, $dev, $callback->($status)
677 [EXPERIMENTAL]
678
679 Asynchronously create a device node (or fifo). See mknod(2).
680
681 The only (POSIX-) portable way of calling this function is:
682
683 aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
684
685 See "aio_stat" for info about some potentially helpful extra
686 constants and functions.
687
688 aio_link $srcpath, $dstpath, $callback->($status)
689 Asynchronously create a new link to the existing object at $srcpath
690 at the path $dstpath and call the callback with the result code.
691
692 aio_symlink $srcpath, $dstpath, $callback->($status)
693 Asynchronously create a new symbolic link to the existing object at
694 $srcpath at the path $dstpath and call the callback with the result
695 code.
696
697 aio_readlink $pathname, $callback->($link)
698 Asynchronously read the symlink specified by $path and pass it to
699 the callback. If an error occurs, nothing or undef gets passed to
700 the callback.
701
702 aio_realpath $pathname, $callback->($path)
703 Asynchronously make the path absolute and resolve any symlinks in
704 $path. The resulting path only consists of directories (same as
705 Cwd::realpath).
706
707 This request can be used to get the absolute path of the current
708 working directory by passing it a path of . (a single dot).
709
710 aio_rename $srcpath, $dstpath, $callback->($status)
711 Asynchronously rename the object at $srcpath to $dstpath, just as
712 rename(2) and call the callback with the result code.
713
714 On systems that support the AIO::WD working directory abstraction
715 natively, the case "[$wd, "."]" as $srcpath is specialcased -
716 instead of failing, "rename" is called on the absolute path of $wd.
717
718 aio_mkdir $pathname, $mode, $callback->($status)
719 Asynchronously mkdir (create) a directory and call the callback with
720 the result code. $mode will be modified by the umask at the time the
721 request is executed, so do not change your umask.
722
723 aio_rmdir $pathname, $callback->($status)
724 Asynchronously rmdir (delete) a directory and call the callback with
725 the result code.
726
727 On systems that support the AIO::WD working directory abstraction
728 natively, the case "[$wd, "."]" is specialcased - instead of
729 failing, "rmdir" is called on the absolute path of $wd.
730
731 aio_readdir $pathname, $callback->($entries)
732 Unlike the POSIX call of the same name, "aio_readdir" reads an
733 entire directory (i.e. opendir + readdir + closedir). The entries
734 will not be sorted, and will NOT include the "." and ".." entries.
735
736 The callback is passed a single argument which is either "undef" or
737 an array-ref with the filenames.
738
739 aio_readdirx $pathname, $flags, $callback->($entries, $flags)
740 Quite similar to "aio_readdir", but the $flags argument allows one
741 to tune behaviour and output format. In case of an error, $entries
742 will be "undef".
743
744 The flags are a combination of the following constants, ORed
745 together (the flags will also be passed to the callback, possibly
746 modified):
747
748 IO::AIO::READDIR_DENTS
749 When this flag is off, then the callback gets an arrayref
750 consisting of names only (as with "aio_readdir"), otherwise it
751 gets an arrayref with "[$name, $type, $inode]" arrayrefs, each
752 describing a single directory entry in more detail.
753
754 $name is the name of the entry.
755
756 $type is one of the "IO::AIO::DT_xxx" constants:
757
758 "IO::AIO::DT_UNKNOWN", "IO::AIO::DT_FIFO", "IO::AIO::DT_CHR",
759 "IO::AIO::DT_DIR", "IO::AIO::DT_BLK", "IO::AIO::DT_REG",
760 "IO::AIO::DT_LNK", "IO::AIO::DT_SOCK", "IO::AIO::DT_WHT".
761
762 "IO::AIO::DT_UNKNOWN" means just that: readdir does not know. If
763 you need to know, you have to run stat yourself. Also, for speed
764 reasons, the $type scalars are read-only: you can not modify
765 them.
766
767 $inode is the inode number (which might not be exact on systems
768 with 64 bit inode numbers and 32 bit perls). This field has
769 unspecified content on systems that do not deliver the inode
770 information.
771
772 IO::AIO::READDIR_DIRS_FIRST
773 When this flag is set, then the names will be returned in an
774 order where likely directories come first, in optimal stat
775 order. This is useful when you need to quickly find directories,
776 or you want to find all directories while avoiding to stat()
777 each entry.
778
779 If the system returns type information in readdir, then this is
780 used to find directories directly. Otherwise, likely directories
781 are names beginning with ".", or otherwise names with no dots,
782 of which names with short names are tried first.
783
784 IO::AIO::READDIR_STAT_ORDER
785 When this flag is set, then the names will be returned in an
786 order suitable for stat()'ing each one. That is, when you plan
787 to stat() all files in the given directory, then the returned
788 order will likely be fastest.
789
790 If both this flag and "IO::AIO::READDIR_DIRS_FIRST" are
791 specified, then the likely dirs come first, resulting in a less
792 optimal stat order.
793
794 IO::AIO::READDIR_FOUND_UNKNOWN
795 This flag should not be set when calling "aio_readdirx".
796 Instead, it is being set by "aio_readdirx", when any of the
797 $type's found were "IO::AIO::DT_UNKNOWN". The absence of this
798 flag therefore indicates that all $type's are known, which can
799 be used to speed up some algorithms.
800
801 aio_load $pathname, $data, $callback->($status)
802 This is a composite request that tries to fully load the given file
803 into memory. Status is the same as with aio_read.
804
805 aio_copy $srcpath, $dstpath, $callback->($status)
806 Try to copy the *file* (directories not supported as either source
807 or destination) from $srcpath to $dstpath and call the callback with
808 a status of 0 (ok) or -1 (error, see $!).
809
810 This is a composite request that creates the destination file with
811 mode 0200 and copies the contents of the source file into it using
812 "aio_sendfile", followed by restoring atime, mtime, access mode and
813 uid/gid, in that order.
814
815 If an error occurs, the partial destination file will be unlinked,
816 if possible, except when setting atime, mtime, access mode and
817 uid/gid, where errors are being ignored.
818
819 aio_move $srcpath, $dstpath, $callback->($status)
820 Try to move the *file* (directories not supported as either source
821 or destination) from $srcpath to $dstpath and call the callback with
822 a status of 0 (ok) or -1 (error, see $!).
823
824 This is a composite request that tries to rename(2) the file first;
825 if rename fails with "EXDEV", it copies the file with "aio_copy"
826 and, if that is successful, unlinks the $srcpath.
827
828 aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
829 Scans a directory (similar to "aio_readdir") but additionally tries
830 to efficiently separate the entries of directory $path into two sets
831 of names, directories you can recurse into (directories), and ones
832 you cannot recurse into (everything else, including symlinks to
833 directories).
834
835 "aio_scandir" is a composite request that creates of many sub
836 requests_ $maxreq specifies the maximum number of outstanding aio
837 requests that this function generates. If it is "<= 0", then a
838 suitable default will be chosen (currently 4).
839
840 On error, the callback is called without arguments, otherwise it
841 receives two array-refs with path-relative entry names.
842
843 Example:
844
845 aio_scandir $dir, 0, sub {
846 my ($dirs, $nondirs) = @_;
847 print "real directories: @$dirs\n";
848 print "everything else: @$nondirs\n";
849 };
850
851 Implementation notes.
852
853 The "aio_readdir" cannot be avoided, but "stat()"'ing every entry
854 can.
855
856 If readdir returns file type information, then this is used directly
857 to find directories.
858
859 Otherwise, after reading the directory, the modification time, size
860 etc. of the directory before and after the readdir is checked, and
861 if they match (and isn't the current time), the link count will be
862 used to decide how many entries are directories (if >= 2).
863 Otherwise, no knowledge of the number of subdirectories will be
864 assumed.
865
866 Then entries will be sorted into likely directories a non-initial
867 dot currently) and likely non-directories (see "aio_readdirx"). Then
868 every entry plus an appended "/." will be "stat"'ed, likely
869 directories first, in order of their inode numbers. If that
870 succeeds, it assumes that the entry is a directory or a symlink to
871 directory (which will be checked separately). This is often faster
872 than stat'ing the entry itself because filesystems might detect the
873 type of the entry without reading the inode data (e.g. ext2fs
874 filetype feature), even on systems that cannot return the filetype
875 information on readdir.
876
877 If the known number of directories (link count - 2) has been
878 reached, the rest of the entries is assumed to be non-directories.
879
880 This only works with certainty on POSIX (= UNIX) filesystems, which
881 fortunately are the vast majority of filesystems around.
882
883 It will also likely work on non-POSIX filesystems with reduced
884 efficiency as those tend to return 0 or 1 as link counts, which
885 disables the directory counting heuristic.
886
887 aio_rmtree $pathname, $callback->($status)
888 Delete a directory tree starting (and including) $path, return the
889 status of the final "rmdir" only. This is a composite request that
890 uses "aio_scandir" to recurse into and rmdir directories, and unlink
891 everything else.
892
893 aio_sync $callback->($status)
894 Asynchronously call sync and call the callback when finished.
895
896 aio_fsync $fh, $callback->($status)
897 Asynchronously call fsync on the given filehandle and call the
898 callback with the fsync result code.
899
900 aio_fdatasync $fh, $callback->($status)
901 Asynchronously call fdatasync on the given filehandle and call the
902 callback with the fdatasync result code.
903
904 If this call isn't available because your OS lacks it or it couldn't
905 be detected, it will be emulated by calling "fsync" instead.
906
907 aio_syncfs $fh, $callback->($status)
908 Asynchronously call the syncfs syscall to sync the filesystem
909 associated to the given filehandle and call the callback with the
910 syncfs result code. If syncfs is not available, calls sync(), but
911 returns -1 and sets errno to "ENOSYS" nevertheless.
912
913 aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
914 Sync the data portion of the file specified by $offset and $length
915 to disk (but NOT the metadata), by calling the Linux-specific
916 sync_file_range call. If sync_file_range is not available or it
917 returns ENOSYS, then fdatasync or fsync is being substituted.
918
919 $flags can be a combination of
920 "IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE",
921 "IO::AIO::SYNC_FILE_RANGE_WRITE" and
922 "IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER": refer to the sync_file_range
923 manpage for details.
924
925 aio_pathsync $pathname, $callback->($status)
926 This request tries to open, fsync and close the given path. This is
927 a composite request intended to sync directories after directory
928 operations (E.g. rename). This might not work on all operating
929 systems or have any specific effect, but usually it makes sure that
930 directory changes get written to disc. It works for anything that
931 can be opened for read-only, not just directories.
932
933 Future versions of this function might fall back to other methods
934 when "fsync" on the directory fails (such as calling "sync").
935
936 Passes 0 when everything went ok, and -1 on error.
937
938 aio_msync $scalar, $offset = 0, $length = undef, flags = 0,
939 $callback->($status)
940 This is a rather advanced IO::AIO call, which only works on
941 mmap(2)ed scalars (see the "IO::AIO::mmap" function, although it
942 also works on data scalars managed by the Sys::Mmap or Mmap modules,
943 note that the scalar must only be modified in-place while an aio
944 operation is pending on it).
945
946 It calls the "msync" function of your OS, if available, with the
947 memory area starting at $offset in the string and ending $length
948 bytes later. If $length is negative, counts from the end, and if
949 $length is "undef", then it goes till the end of the string. The
950 flags can be a combination of "IO::AIO::MS_ASYNC",
951 "IO::AIO::MS_INVALIDATE" and "IO::AIO::MS_SYNC".
952
953 aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0,
954 $callback->($status)
955 This is a rather advanced IO::AIO call, which works best on
956 mmap(2)ed scalars.
957
958 It touches (reads or writes) all memory pages in the specified range
959 inside the scalar. All caveats and parameters are the same as for
960 "aio_msync", above, except for flags, which must be either 0 (which
961 reads all pages and ensures they are instantiated) or
962 "IO::AIO::MT_MODIFY", which modifies the memory pages (by reading
963 and writing an octet from it, which dirties the page).
964
965 aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
966 This is a rather advanced IO::AIO call, which works best on
967 mmap(2)ed scalars.
968
969 It reads in all the pages of the underlying storage into memory (if
970 any) and locks them, so they are not getting swapped/paged out or
971 removed.
972
973 If $length is undefined, then the scalar will be locked till the
974 end.
975
976 On systems that do not implement "mlock", this function returns -1
977 and sets errno to "ENOSYS".
978
979 Note that the corresponding "munlock" is synchronous and is
980 documented under "MISCELLANEOUS FUNCTIONS".
981
982 Example: open a file, mmap and mlock it - both will be undone when
983 $data gets destroyed.
984
985 open my $fh, "<", $path or die "$path: $!";
986 my $data;
987 IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
988 aio_mlock $data; # mlock in background
989
990 aio_mlockall $flags, $callback->($status)
991 Calls the "mlockall" function with the given $flags (a combination
992 of "IO::AIO::MCL_CURRENT" and "IO::AIO::MCL_FUTURE").
993
994 On systems that do not implement "mlockall", this function returns
995 -1 and sets errno to "ENOSYS".
996
997 Note that the corresponding "munlockall" is synchronous and is
998 documented under "MISCELLANEOUS FUNCTIONS".
999
1000 Example: asynchronously lock all current and future pages into
1001 memory.
1002
1003 aio_mlockall IO::AIO::MCL_FUTURE;
1004
1005 aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
1006 Queries the extents of the given file (by calling the Linux "FIEMAP"
1007 ioctl, see <http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for
1008 details). If the ioctl is not available on your OS, then this
1009 request will fail with "ENOSYS".
1010
1011 $start is the starting offset to query extents for, $length is the
1012 size of the range to query - if it is "undef", then the whole file
1013 will be queried.
1014
1015 $flags is a combination of flags ("IO::AIO::FIEMAP_FLAG_SYNC" or
1016 "IO::AIO::FIEMAP_FLAG_XATTR" - "IO::AIO::FIEMAP_FLAGS_COMPAT" is
1017 also exported), and is normally 0 or "IO::AIO::FIEMAP_FLAG_SYNC" to
1018 query the data portion.
1019
1020 $count is the maximum number of extent records to return. If it is
1021 "undef", then IO::AIO queries all extents of the range. As a very
1022 special case, if it is 0, then the callback receives the number of
1023 extents instead of the extents themselves (which is unreliable, see
1024 below).
1025
1026 If an error occurs, the callback receives no arguments. The special
1027 "errno" value "IO::AIO::EBADR" is available to test for flag errors.
1028
1029 Otherwise, the callback receives an array reference with extent
1030 structures. Each extent structure is an array reference itself, with
1031 the following members:
1032
1033 [$logical, $physical, $length, $flags]
1034
1035 Flags is any combination of the following flag values (typically
1036 either 0 or "IO::AIO::FIEMAP_EXTENT_LAST" (1)):
1037
1038 "IO::AIO::FIEMAP_EXTENT_LAST", "IO::AIO::FIEMAP_EXTENT_UNKNOWN",
1039 "IO::AIO::FIEMAP_EXTENT_DELALLOC", "IO::AIO::FIEMAP_EXTENT_ENCODED",
1040 "IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED",
1041 "IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED",
1042 "IO::AIO::FIEMAP_EXTENT_DATA_INLINE",
1043 "IO::AIO::FIEMAP_EXTENT_DATA_TAIL",
1044 "IO::AIO::FIEMAP_EXTENT_UNWRITTEN", "IO::AIO::FIEMAP_EXTENT_MERGED"
1045 or "IO::AIO::FIEMAP_EXTENT_SHARED".
1046
1047 At the time of this writing (Linux 3.2), this requets is unreliable
1048 unless $count is "undef", as the kernel has all sorts of bugs
1049 preventing it to return all extents of a range for files with large
1050 number of extents. The code works around all these issues if $count
1051 is undef.
1052
1053 aio_group $callback->(...)
1054 This is a very special aio request: Instead of doing something, it
1055 is a container for other aio requests, which is useful if you want
1056 to bundle many requests into a single, composite, request with a
1057 definite callback and the ability to cancel the whole request with
1058 its subrequests.
1059
1060 Returns an object of class IO::AIO::GRP. See its documentation below
1061 for more info.
1062
1063 Example:
1064
1065 my $grp = aio_group sub {
1066 print "all stats done\n";
1067 };
1068
1069 add $grp
1070 (aio_stat ...),
1071 (aio_stat ...),
1072 ...;
1073
1074 aio_nop $callback->()
1075 This is a special request - it does nothing in itself and is only
1076 used for side effects, such as when you want to add a dummy request
1077 to a group so that finishing the requests in the group depends on
1078 executing the given code.
1079
1080 While this request does nothing, it still goes through the execution
1081 phase and still requires a worker thread. Thus, the callback will
1082 not be executed immediately but only after other requests in the
1083 queue have entered their execution phase. This can be used to
1084 measure request latency.
1085
1086 IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
1087 Mainly used for debugging and benchmarking, this aio request puts
1088 one of the request workers to sleep for the given time.
1089
1090 While it is theoretically handy to have simple I/O scheduling
1091 requests like sleep and file handle readable/writable, the overhead
1092 this creates is immense (it blocks a thread for a long time) so do
1093 not use this function except to put your application under
1094 artificial I/O pressure.
1095
1096 IO::AIO::WD - multiple working directories
1097 Your process only has one current working directory, which is used by
1098 all threads. This makes it hard to use relative paths (some other
1099 component could call "chdir" at any time, and it is hard to control when
1100 the path will be used by IO::AIO).
1101
1102 One solution for this is to always use absolute paths. This usually
1103 works, but can be quite slow (the kernel has to walk the whole path on
1104 every access), and can also be a hassle to implement.
1105
1106 Newer POSIX systems have a number of functions (openat, fdopendir,
1107 futimensat and so on) that make it possible to specify working
1108 directories per operation.
1109
1110 For portability, and because the clowns who "designed", or shall I
1111 write, perpetrated this new interface were obviously half-drunk, this
1112 abstraction cannot be perfect, though.
1113
1114 IO::AIO allows you to convert directory paths into a so-called
1115 IO::AIO::WD object. This object stores the canonicalised, absolute
1116 version of the path, and on systems that allow it, also a directory file
1117 descriptor.
1118
1119 Everywhere where a pathname is accepted by IO::AIO (e.g. in "aio_stat"
1120 or "aio_unlink"), one can specify an array reference with an IO::AIO::WD
1121 object and a pathname instead (or the IO::AIO::WD object alone, which
1122 gets interpreted as "[$wd, "."]"). If the pathname is absolute, the
1123 IO::AIO::WD object is ignored, otherwise the pathname is resolved
1124 relative to that IO::AIO::WD object.
1125
1126 For example, to get a wd object for /etc and then stat passwd inside,
1127 you would write:
1128
1129 aio_wd "/etc", sub {
1130 my $etcdir = shift;
1131
1132 # although $etcdir can be undef on error, there is generally no reason
1133 # to check for errors here, as aio_stat will fail with ENOENT
1134 # when $etcdir is undef.
1135
1136 aio_stat [$etcdir, "passwd"], sub {
1137 # yay
1138 };
1139 };
1140
1141 The fact that "aio_wd" is a request and not a normal function shows that
1142 creating an IO::AIO::WD object is itself a potentially blocking
1143 operation, which is why it is done asynchronously.
1144
1145 To stat the directory obtained with "aio_wd" above, one could write
1146 either of the following three request calls:
1147
1148 aio_lstat "/etc" , sub { ... # pathname as normal string
1149 aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
1150 aio_lstat $wd , sub { ... # shorthand for the previous
1151
1152 As with normal pathnames, IO::AIO keeps a copy of the working directory
1153 object and the pathname string, so you could write the following without
1154 causing any issues due to $path getting reused:
1155
1156 my $path = [$wd, undef];
1157
1158 for my $name (qw(abc def ghi)) {
1159 $path->[1] = $name;
1160 aio_stat $path, sub {
1161 # ...
1162 };
1163 }
1164
1165 There are some caveats: when directories get renamed (or deleted), the
1166 pathname string doesn't change, so will point to the new directory (or
1167 nowhere at all), while the directory fd, if available on the system,
1168 will still point to the original directory. Most functions accepting a
1169 pathname will use the directory fd on newer systems, and the string on
1170 older systems. Some functions (such as realpath) will always rely on the
1171 string form of the pathname.
1172
1173 So this functionality is mainly useful to get some protection against
1174 "chdir", to easily get an absolute path out of a relative path for
1175 future reference, and to speed up doing many operations in the same
1176 directory (e.g. when stat'ing all files in a directory).
1177
1178 The following functions implement this working directory abstraction:
1179
1180 aio_wd $pathname, $callback->($wd)
1181 Asynchonously canonicalise the given pathname and convert it to an
1182 IO::AIO::WD object representing it. If possible and supported on the
1183 system, also open a directory fd to speed up pathname resolution
1184 relative to this working directory.
1185
1186 If something goes wrong, then "undef" is passwd to the callback
1187 instead of a working directory object and $! is set appropriately.
1188 Since passing "undef" as working directory component of a pathname
1189 fails the request with "ENOENT", there is often no need for error
1190 checking in the "aio_wd" callback, as future requests using the
1191 value will fail in the expected way.
1192
1193 IO::AIO::CWD
1194 This is a compiletime constant (object) that represents the process
1195 current working directory.
1196
1197 Specifying this object as working directory object for a pathname is
1198 as if the pathname would be specified directly, without a directory
1199 object. For example, these calls are functionally identical:
1200
1201 aio_stat "somefile", sub { ... };
1202 aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
1203
1204 To recover the path associated with an IO::AIO::WD object, you can use
1205 "aio_realpath":
1206
1207 aio_realpath $wd, sub {
1208 warn "path is $_[0]\n";
1209 };
1210
1211 Currently, "aio_statvfs" always, and "aio_rename" and "aio_rmdir"
1212 sometimes, fall back to using an absolue path.
1213
1214 IO::AIO::REQ CLASS
1215 All non-aggregate "aio_*" functions return an object of this class when
1216 called in non-void context.
1217
1218 cancel $req
1219 Cancels the request, if possible. Has the effect of skipping
1220 execution when entering the execute state and skipping calling the
1221 callback when entering the the result state, but will leave the
1222 request otherwise untouched (with the exception of readdir). That
1223 means that requests that currently execute will not be stopped and
1224 resources held by the request will not be freed prematurely.
1225
1226 cb $req $callback->(...)
1227 Replace (or simply set) the callback registered to the request.
1228
1229 IO::AIO::GRP CLASS
1230 This class is a subclass of IO::AIO::REQ, so all its methods apply to
1231 objects of this class, too.
1232
1233 A IO::AIO::GRP object is a special request that can contain multiple
1234 other aio requests.
1235
1236 You create one by calling the "aio_group" constructing function with a
1237 callback that will be called when all contained requests have entered
1238 the "done" state:
1239
1240 my $grp = aio_group sub {
1241 print "all requests are done\n";
1242 };
1243
1244 You add requests by calling the "add" method with one or more
1245 "IO::AIO::REQ" objects:
1246
1247 $grp->add (aio_unlink "...");
1248
1249 add $grp aio_stat "...", sub {
1250 $_[0] or return $grp->result ("error");
1251
1252 # add another request dynamically, if first succeeded
1253 add $grp aio_open "...", sub {
1254 $grp->result ("ok");
1255 };
1256 };
1257
573 This makes it very easy to create composite requests (see the source 1258 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 1259 "aio_move" for an application) that work and feel like simple requests.
575 requests.
576 1260
577 * The IO::AIO::GRP objects will be cleaned up during calls to 1261 * The IO::AIO::GRP objects will be cleaned up during calls to
578 "IO::AIO::poll_cb", just like any other request. 1262 "IO::AIO::poll_cb", just like any other request.
1263
579 * They can be canceled like any other request. Canceling will cancel 1264 * They can be canceled like any other request. Canceling will cancel
580 not only the request itself, but also all requests it contains. 1265 not only the request itself, but also all requests it contains.
1266
581 * They can also can also be added to other IO::AIO::GRP objects. 1267 * They can also can also be added to other IO::AIO::GRP objects.
1268
582 * You must not add requests to a group from within the group 1269 * You must not add requests to a group from within the group callback
583 callback (or any later time). 1270 (or any later time).
584 1271
585 Their lifetime, simplified, looks like this: when they are empty, 1272 Their lifetime, simplified, looks like this: when they are empty, they
586 they will finish very quickly. If they contain only requests that 1273 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 1274 "done" state, they will also finish. Otherwise they will continue to
588 continue to exist. 1275 exist.
589 1276
590 That means after creating a group you have some time to add 1277 That means after creating a group you have some time to add requests
1278 (precisely before the callback has been invoked, which is only done
591 requests. And in the callbacks of those requests, you can add 1279 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 1280 add further requests to the group. And only when all those requests have
593 finished will the the group itself finish. 1281 finished will the the group itself finish.
594 1282
595 add $grp ... 1283 add $grp ...
596 $grp->add (...) 1284 $grp->add (...)
597 Add one or more requests to the group. Any type of IO::AIO::REQ 1285 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 1286 be added, including other groups, as long as you do not create
599 create circular dependencies. 1287 circular dependencies.
600 1288
601 Returns all its arguments. 1289 Returns all its arguments.
602 1290
603 $grp->cancel_subs 1291 $grp->cancel_subs
604 Cancel all subrequests and clears any feeder, but not the group 1292 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 1293 request itself. Useful when you queued a lot of events but got a
606 result early. 1294 result early.
607 1295
1296 The group request will finish normally (you cannot add requests to
1297 the group).
1298
608 $grp->result (...) 1299 $grp->result (...)
609 Set the result value(s) that will be passed to the group 1300 Set the result value(s) that will be passed to the group callback
610 callback when all subrequests have finished and set thre groups 1301 when all subrequests have finished and set the groups errno to the
611 errno to the current value of errno (just like calling "errno" 1302 current value of errno (just like calling "errno" without an error
612 without an error number). By default, no argument will be passed 1303 number). By default, no argument will be passed and errno is zero.
613 and errno is zero.
614 1304
615 $grp->errno ([$errno]) 1305 $grp->errno ([$errno])
616 Sets the group errno value to $errno, or the current value of 1306 Sets the group errno value to $errno, or the current value of errno
617 errno when the argument is missing. 1307 when the argument is missing.
618 1308
619 Every aio request has an associated errno value that is restored 1309 Every aio request has an associated errno value that is restored
620 when the callback is invoked. This method lets you change this 1310 when the callback is invoked. This method lets you change this value
621 value from its default (0). 1311 from its default (0).
622 1312
623 Calling "result" will also set errno, so make sure you either 1313 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. 1314 before the call to "result", or call c<errno> after it.
625 1315
626 feed $grp $callback->($grp) 1316 feed $grp $callback->($grp)
627 Sets a feeder/generator on this group: every group can have an 1317 Sets a feeder/generator on this group: every group can have an
628 attached generator that generates requests if idle. The idea 1318 attached generator that generates requests if idle. The idea behind
629 behind this is that, although you could just queue as many 1319 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 1320 want in a group, this might starve other requests for a potentially
631 requests for a potentially long time. For example, "aio_scandir" 1321 long time. For example, "aio_scandir" might generate hundreds of
632 might generate hundreds of thousands "aio_stat" requests, 1322 thousands of "aio_stat" requests, delaying any later requests for a
633 delaying any later requests for a long time. 1323 long time.
634 1324
635 To avoid this, and allow incremental generation of requests, you 1325 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 1326 instead a group and set a feeder on it that generates those
637 requests. The feed callback will be called whenever there are 1327 requests. The feed callback will be called whenever there are few
638 few enough (see "limit", below) requests active in the group 1328 enough (see "limit", below) requests active in the group itself and
639 itself and is expected to queue more requests. 1329 is expected to queue more requests.
640 1330
641 The feed callback can queue as many requests as it likes (i.e. 1331 The feed callback can queue as many requests as it likes (i.e. "add"
642 "add" does not impose any limits). 1332 does not impose any limits).
643 1333
644 If the feed does not queue more requests when called, it will be 1334 If the feed does not queue more requests when called, it will be
645 automatically removed from the group. 1335 automatically removed from the group.
646 1336
647 If the feed limit is 0, it will be set to 2 automatically. 1337 If the feed limit is 0 when this method is called, it will be set to
1338 2 automatically.
648 1339
649 Example: 1340 Example:
650 1341
651 # stat all files in @files, but only ever use four aio requests concurrently: 1342 # stat all files in @files, but only ever use four aio requests concurrently:
652 1343
653 my $grp = aio_group sub { print "finished\n" }; 1344 my $grp = aio_group sub { print "finished\n" };
654 limit $grp 4; 1345 limit $grp 4;
655 feed $grp sub { 1346 feed $grp sub {
656 my $file = pop @files 1347 my $file = pop @files
657 or return; 1348 or return;
658 1349
659 add $grp aio_stat $file, sub { ... }; 1350 add $grp aio_stat $file, sub { ... };
660 }; 1351 };
661 1352
662 limit $grp $num 1353 limit $grp $num
663 Sets the feeder limit for the group: The feeder will be called 1354 Sets the feeder limit for the group: The feeder will be called
664 whenever the group contains less than this many requests. 1355 whenever the group contains less than this many requests.
665 1356
666 Setting the limit to 0 will pause the feeding process. 1357 Setting the limit to 0 will pause the feeding process.
1358
1359 The default value for the limit is 0, but note that setting a feeder
1360 automatically bumps it up to 2.
667 1361
668 SUPPORT FUNCTIONS 1362 SUPPORT FUNCTIONS
669 EVENT PROCESSING AND EVENT LOOP INTEGRATION 1363 EVENT PROCESSING AND EVENT LOOP INTEGRATION
670 $fileno = IO::AIO::poll_fileno 1364 $fileno = IO::AIO::poll_fileno
671 Return the *request result pipe file descriptor*. This 1365 Return the *request result pipe file descriptor*. This filehandle
672 filehandle must be polled for reading by some mechanism outside 1366 must be polled for reading by some mechanism outside this module
673 this module (e.g. Event or select, see below or the SYNOPSIS). 1367 (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 1368 pipe becomes readable you have to call "poll_cb" to check the
675 the results. 1369 results.
676 1370
677 See "poll_cb" for an example. 1371 See "poll_cb" for an example.
678 1372
679 IO::AIO::poll_cb 1373 IO::AIO::poll_cb
680 Process some outstanding events on the result pipe. You have to 1374 Process some requests that have reached the result phase (i.e. they
681 call this regularly. Returns the number of events processed. 1375 have been executed but the results are not yet reported). You have
1376 to call this "regularly" to finish outstanding requests.
1377
1378 Returns 0 if all events could be processed (or there were no events
1379 to process), or -1 if it returned earlier for whatever reason.
682 Returns immediately when no events are outstanding. The amount 1380 Returns immediately when no events are outstanding. The amount of
683 of events processed depends on the settings of 1381 events processed depends on the settings of "IO::AIO::max_poll_req",
684 "IO::AIO::max_poll_req" and "IO::AIO::max_poll_time". 1382 "IO::AIO::max_poll_time" and "IO::AIO::max_outstanding".
685 1383
686 If not all requests were processed for whatever reason, the 1384 If not all requests were processed for whatever reason, the poll
687 filehandle will still be ready when "poll_cb" returns. 1385 file descriptor will still be ready when "poll_cb" returns, so
1386 normally you don't have to do anything special to have it called
1387 later.
688 1388
1389 Apart from calling "IO::AIO::poll_cb" when the event filehandle
1390 becomes ready, it can be beneficial to call this function from loops
1391 which submit a lot of requests, to make sure the results get
1392 processed when they become available and not just when the loop is
1393 finished and the event loop takes over again. This function returns
1394 very fast when there are no outstanding requests.
1395
689 Example: Install an Event watcher that automatically calls 1396 Example: Install an Event watcher that automatically calls
690 IO::AIO::poll_cb with high priority: 1397 IO::AIO::poll_cb with high priority (more examples can be found in
1398 the SYNOPSIS section, at the top of this document):
691 1399
692 Event->io (fd => IO::AIO::poll_fileno, 1400 Event->io (fd => IO::AIO::poll_fileno,
693 poll => 'r', async => 1, 1401 poll => 'r', async => 1,
694 cb => \&IO::AIO::poll_cb); 1402 cb => \&IO::AIO::poll_cb);
695 1403
1404 IO::AIO::poll_wait
1405 Wait until either at least one request is in the result phase or no
1406 requests are outstanding anymore.
1407
1408 This is useful if you want to synchronously wait for some requests
1409 to become ready, without actually handling them.
1410
1411 See "nreqs" for an example.
1412
1413 IO::AIO::poll
1414 Waits until some requests have been handled.
1415
1416 Returns the number of requests processed, but is otherwise strictly
1417 equivalent to:
1418
1419 IO::AIO::poll_wait, IO::AIO::poll_cb
1420
1421 IO::AIO::flush
1422 Wait till all outstanding AIO requests have been handled.
1423
1424 Strictly equivalent to:
1425
1426 IO::AIO::poll_wait, IO::AIO::poll_cb
1427 while IO::AIO::nreqs;
1428
696 IO::AIO::max_poll_reqs $nreqs 1429 IO::AIO::max_poll_reqs $nreqs
697 IO::AIO::max_poll_time $seconds 1430 IO::AIO::max_poll_time $seconds
698 These set the maximum number of requests (default 0, meaning 1431 These set the maximum number of requests (default 0, meaning
699 infinity) that are being processed by "IO::AIO::poll_cb" in one 1432 infinity) that are being processed by "IO::AIO::poll_cb" in one
700 call, respectively the maximum amount of time (default 0, 1433 call, respectively the maximum amount of time (default 0, meaning
701 meaning infinity) spent in "IO::AIO::poll_cb" to process 1434 infinity) spent in "IO::AIO::poll_cb" to process requests (more
702 requests (more correctly the mininum amount of time "poll_cb" is 1435 correctly the mininum amount of time "poll_cb" is allowed to use).
703 allowed to use).
704 1436
1437 Setting "max_poll_time" to a non-zero value creates an overhead of
1438 one syscall per request processed, which is not normally a problem
1439 unless your callbacks are really really fast or your OS is really
1440 really slow (I am not mentioning Solaris here). Using
1441 "max_poll_reqs" incurs no overhead.
1442
705 Setting these is useful if you want to ensure some level of 1443 Setting these is useful if you want to ensure some level of
706 interactiveness when perl is not fast enough to process all 1444 interactiveness when perl is not fast enough to process all requests
707 requests in time. 1445 in time.
708 1446
709 For interactive programs, values such as 0.01 to 0.1 should be 1447 For interactive programs, values such as 0.01 to 0.1 should be fine.
710 fine.
711 1448
712 Example: Install an Event watcher that automatically calls 1449 Example: Install an Event watcher that automatically calls
713 IO::AIO::poll_some with low priority, to ensure that other parts 1450 IO::AIO::poll_cb with low priority, to ensure that other parts of
714 of the program get the CPU sometimes even under high AIO load. 1451 the program get the CPU sometimes even under high AIO load.
715 1452
716 # try not to spend much more than 0.1s in poll_cb 1453 # try not to spend much more than 0.1s in poll_cb
717 IO::AIO::max_poll_time 0.1; 1454 IO::AIO::max_poll_time 0.1;
718 1455
719 # use a low priority so other tasks have priority 1456 # use a low priority so other tasks have priority
720 Event->io (fd => IO::AIO::poll_fileno, 1457 Event->io (fd => IO::AIO::poll_fileno,
721 poll => 'r', nice => 1, 1458 poll => 'r', nice => 1,
722 cb => &IO::AIO::poll_cb); 1459 cb => &IO::AIO::poll_cb);
723
724 IO::AIO::poll_wait
725 Wait till the result filehandle becomes ready for reading
726 (simply does a "select" on the filehandle. This is useful if you
727 want to synchronously wait for some requests to finish).
728
729 See "nreqs" for an example.
730
731 IO::AIO::poll
732 Waits until some requests have been handled.
733
734 Strictly equivalent to:
735
736 IO::AIO::poll_wait, IO::AIO::poll_cb
737 if IO::AIO::nreqs;
738
739 IO::AIO::flush
740 Wait till all outstanding AIO requests have been handled.
741
742 Strictly equivalent to:
743
744 IO::AIO::poll_wait, IO::AIO::poll_cb
745 while IO::AIO::nreqs;
746 1460
747 CONTROLLING THE NUMBER OF THREADS 1461 CONTROLLING THE NUMBER OF THREADS
748 IO::AIO::min_parallel $nthreads 1462 IO::AIO::min_parallel $nthreads
749 Set the minimum number of AIO threads to $nthreads. The current 1463 Set the minimum number of AIO threads to $nthreads. The current
750 default is 8, which means eight asynchronous operations can 1464 default is 8, which means eight asynchronous operations can execute
751 execute concurrently at any one time (the number of outstanding 1465 concurrently at any one time (the number of outstanding requests,
752 requests, however, is unlimited). 1466 however, is unlimited).
753 1467
754 IO::AIO starts threads only on demand, when an AIO request is 1468 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 1469 and no free thread exists. Please note that queueing up a hundred
756 hundred requests can create demand for a hundred threads, even 1470 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 1471 out that everything is in the cache and could have been processed
758 been processed faster by a single thread. 1472 faster by a single thread.
759 1473
760 It is recommended to keep the number of threads relatively low, 1474 It is recommended to keep the number of threads relatively low, as
761 as some Linux kernel versions will scale negatively with the 1475 some Linux kernel versions will scale negatively with the number of
762 number of threads (higher parallelity => MUCH higher latency). 1476 threads (higher parallelity => MUCH higher latency). With current
763 With current Linux 2.6 versions, 4-32 threads should be fine. 1477 Linux 2.6 versions, 4-32 threads should be fine.
764 1478
765 Under most circumstances you don't need to call this function, 1479 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 1480 the module selects a default that is suitable for low to moderate
767 moderate load. 1481 load.
768 1482
769 IO::AIO::max_parallel $nthreads 1483 IO::AIO::max_parallel $nthreads
770 Sets the maximum number of AIO threads to $nthreads. If more 1484 Sets the maximum number of AIO threads to $nthreads. If more than
771 than the specified number of threads are currently running, this 1485 the specified number of threads are currently running, this function
772 function kills them. This function blocks until the limit is 1486 kills them. This function blocks until the limit is reached.
773 reached.
774 1487
775 While $nthreads are zero, aio requests get queued but not 1488 While $nthreads are zero, aio requests get queued but not executed
776 executed until the number of threads has been increased again. 1489 until the number of threads has been increased again.
777 1490
778 This module automatically runs "max_parallel 0" at program end, 1491 This module automatically runs "max_parallel 0" at program end, to
779 to ensure that all threads are killed and that there are no 1492 ensure that all threads are killed and that there are no outstanding
780 outstanding requests. 1493 requests.
781 1494
782 Under normal circumstances you don't need to call this function. 1495 Under normal circumstances you don't need to call this function.
783 1496
784 IO::AIO::max_idle $nthreads 1497 IO::AIO::max_idle $nthreads
785 Limit the number of threads (default: 4) that are allowed to 1498 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 1499 (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 1500 timeout (default: 10 seconds). That means if a thread becomes idle
788 other threads are also idle, it will free its resources and 1501 while $nthreads other threads are also idle, it will free its
789 exit. 1502 resources and exit.
790 1503
791 This is useful when you allow a large number of threads (e.g. 1504 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 1505 1000) to allow for extremely high load situations, but want to free
793 want to free resources under normal circumstances (1000 threads 1506 resources under normal circumstances (1000 threads can easily
794 can easily consume 30MB of RAM). 1507 consume 30MB of RAM).
795 1508
796 The default is probably ok in most situations, especially if 1509 The default is probably ok in most situations, especially if thread
797 thread creation is fast. If thread creation is very slow on your 1510 creation is fast. If thread creation is very slow on your system you
798 system you might want to use larger values. 1511 might want to use larger values.
799 1512
1513 IO::AIO::idle_timeout $seconds
1514 Sets the minimum idle timeout (default 10) after which worker
1515 threads are allowed to exit. SEe "IO::AIO::max_idle".
1516
800 $oldmaxreqs = IO::AIO::max_outstanding $maxreqs 1517 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 1518 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 1519 queue up more than this number of requests, the next call to
808 to the "poll_cb" (and "poll_some" and other functions calling 1520 "IO::AIO::poll_cb" (and other functions calling "poll_cb", such as
809 "poll_cb") function will block until the limit is no longer 1521 "IO::AIO::flush" or "IO::AIO::poll") will block until the limit is
810 exceeded. 1522 no longer exceeded.
811 1523
812 The default value is very large, so there is no practical limit 1524 In other words, this setting does not enforce a queue limit, but can
1525 be used to make poll functions block if the limit is exceeded.
1526
1527 This is a very bad function to use in interactive programs because
1528 it blocks, and a bad way to reduce concurrency because it is
1529 inexact: Better use an "aio_group" together with a feed callback.
1530
1531 Its main use is in scripts without an event loop - when you want to
1532 stat a lot of files, you can write somehting like this:
1533
1534 IO::AIO::max_outstanding 32;
1535
1536 for my $path (...) {
1537 aio_stat $path , ...;
1538 IO::AIO::poll_cb;
1539 }
1540
1541 IO::AIO::flush;
1542
1543 The call to "poll_cb" inside the loop will normally return
1544 instantly, but as soon as more thna 32 reqeusts are in-flight, it
1545 will block until some requests have been handled. This keeps the
1546 loop from pushing a large number of "aio_stat" requests onto the
1547 queue.
1548
1549 The default value for "max_outstanding" is very large, so there is
813 on the number of outstanding requests. 1550 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 1551
820 STATISTICAL INFORMATION 1552 STATISTICAL INFORMATION
821 IO::AIO::nreqs 1553 IO::AIO::nreqs
822 Returns the number of requests currently in the ready, execute 1554 Returns the number of requests currently in the ready, execute or
823 or pending states (i.e. for which their callback has not been 1555 pending states (i.e. for which their callback has not been invoked
824 invoked yet). 1556 yet).
825 1557
826 Example: wait till there are no outstanding requests anymore: 1558 Example: wait till there are no outstanding requests anymore:
827 1559
828 IO::AIO::poll_wait, IO::AIO::poll_cb 1560 IO::AIO::poll_wait, IO::AIO::poll_cb
829 while IO::AIO::nreqs; 1561 while IO::AIO::nreqs;
830 1562
831 IO::AIO::nready 1563 IO::AIO::nready
832 Returns the number of requests currently in the ready state (not 1564 Returns the number of requests currently in the ready state (not yet
833 yet executed). 1565 executed).
834 1566
835 IO::AIO::npending 1567 IO::AIO::npending
836 Returns the number of requests currently in the pending state 1568 Returns the number of requests currently in the pending state
837 (executed, but not yet processed by poll_cb). 1569 (executed, but not yet processed by poll_cb).
1570
1571 MISCELLANEOUS FUNCTIONS
1572 IO::AIO implements some functions that are useful when you want to use
1573 some "Advanced I/O" function not available to in Perl, without going the
1574 "Asynchronous I/O" route. Many of these have an asynchronous "aio_*"
1575 counterpart.
1576
1577 IO::AIO::sendfile $ofh, $ifh, $offset, $count
1578 Calls the "eio_sendfile_sync" function, which is like
1579 "aio_sendfile", but is blocking (this makes most sense if you know
1580 the input data is likely cached already and the output filehandle is
1581 set to non-blocking operations).
1582
1583 Returns the number of bytes copied, or -1 on error.
1584
1585 IO::AIO::fadvise $fh, $offset, $len, $advice
1586 Simply calls the "posix_fadvise" function (see its manpage for
1587 details). The following advice constants are available:
1588 "IO::AIO::FADV_NORMAL", "IO::AIO::FADV_SEQUENTIAL",
1589 "IO::AIO::FADV_RANDOM", "IO::AIO::FADV_NOREUSE",
1590 "IO::AIO::FADV_WILLNEED", "IO::AIO::FADV_DONTNEED".
1591
1592 On systems that do not implement "posix_fadvise", this function
1593 returns ENOSYS, otherwise the return value of "posix_fadvise".
1594
1595 IO::AIO::madvise $scalar, $offset, $len, $advice
1596 Simply calls the "posix_madvise" function (see its manpage for
1597 details). The following advice constants are available:
1598 "IO::AIO::MADV_NORMAL", "IO::AIO::MADV_SEQUENTIAL",
1599 "IO::AIO::MADV_RANDOM", "IO::AIO::MADV_WILLNEED",
1600 "IO::AIO::MADV_DONTNEED".
1601
1602 On systems that do not implement "posix_madvise", this function
1603 returns ENOSYS, otherwise the return value of "posix_madvise".
1604
1605 IO::AIO::mprotect $scalar, $offset, $len, $protect
1606 Simply calls the "mprotect" function on the preferably AIO::mmap'ed
1607 $scalar (see its manpage for details). The following protect
1608 constants are available: "IO::AIO::PROT_NONE", "IO::AIO::PROT_READ",
1609 "IO::AIO::PROT_WRITE", "IO::AIO::PROT_EXEC".
1610
1611 On systems that do not implement "mprotect", this function returns
1612 ENOSYS, otherwise the return value of "mprotect".
1613
1614 IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
1615 Memory-maps a file (or anonymous memory range) and attaches it to
1616 the given $scalar, which will act like a string scalar. Returns true
1617 on success, and false otherwise.
1618
1619 The only operations allowed on the scalar are "substr"/"vec" that
1620 don't change the string length, and most read-only operations such
1621 as copying it or searching it with regexes and so on.
1622
1623 Anything else is unsafe and will, at best, result in memory leaks.
1624
1625 The memory map associated with the $scalar is automatically removed
1626 when the $scalar is destroyed, or when the "IO::AIO::mmap" or
1627 "IO::AIO::munmap" functions are called.
1628
1629 This calls the "mmap"(2) function internally. See your system's
1630 manual page for details on the $length, $prot and $flags parameters.
1631
1632 The $length must be larger than zero and smaller than the actual
1633 filesize.
1634
1635 $prot is a combination of "IO::AIO::PROT_NONE",
1636 "IO::AIO::PROT_EXEC", "IO::AIO::PROT_READ" and/or
1637 "IO::AIO::PROT_WRITE",
1638
1639 $flags can be a combination of "IO::AIO::MAP_SHARED" or
1640 "IO::AIO::MAP_PRIVATE", or a number of system-specific flags (when
1641 not available, the are 0): "IO::AIO::MAP_ANONYMOUS" (which is set to
1642 "MAP_ANON" if your system only provides this constant),
1643 "IO::AIO::MAP_HUGETLB", "IO::AIO::MAP_LOCKED",
1644 "IO::AIO::MAP_NORESERVE", "IO::AIO::MAP_POPULATE",
1645 "IO::AIO::MAP_NONBLOCK", "IO::AIO::MAP_FIXED",
1646 "IO::AIO::MAP_GROWSDOWN", "IO::AIO::MAP_32BIT",
1647 "IO::AIO::MAP_HUGETLB" or "IO::AIO::MAP_STACK".
1648
1649 If $fh is "undef", then a file descriptor of -1 is passed.
1650
1651 $offset is the offset from the start of the file - it generally must
1652 be a multiple of "IO::AIO::PAGESIZE" and defaults to 0.
1653
1654 Example:
1655
1656 use Digest::MD5;
1657 use IO::AIO;
1658
1659 open my $fh, "<verybigfile"
1660 or die "$!";
1661
1662 IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
1663 or die "verybigfile: $!";
1664
1665 my $fast_md5 = md5 $data;
1666
1667 IO::AIO::munmap $scalar
1668 Removes a previous mmap and undefines the $scalar.
1669
1670 IO::AIO::munlock $scalar, $offset = 0, $length = undef
1671 Calls the "munlock" function, undoing the effects of a previous
1672 "aio_mlock" call (see its description for details).
1673
1674 IO::AIO::munlockall
1675 Calls the "munlockall" function.
1676
1677 On systems that do not implement "munlockall", this function returns
1678 ENOSYS, otherwise the return value of "munlockall".
1679
1680 IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
1681 Calls the GNU/Linux splice(2) syscall, if available. If $r_off or
1682 $w_off are "undef", then "NULL" is passed for these, otherwise they
1683 should be the file offset.
1684
1685 $r_fh and $w_fh should not refer to the same file, as splice might
1686 silently corrupt the data in this case.
1687
1688 The following symbol flag values are available:
1689 "IO::AIO::SPLICE_F_MOVE", "IO::AIO::SPLICE_F_NONBLOCK",
1690 "IO::AIO::SPLICE_F_MORE" and "IO::AIO::SPLICE_F_GIFT".
1691
1692 See the splice(2) manpage for details.
1693
1694 IO::AIO::tee $r_fh, $w_fh, $length, $flags
1695 Calls the GNU/Linux tee(2) syscall, see its manpage and the
1696 description for "IO::AIO::splice" above for details.
1697
1698 $actual_size = IO::AIO::pipesize $r_fh[, $new_size]
1699 Attempts to query or change the pipe buffer size. Obviously works
1700 only on pipes, and currently works only on GNU/Linux systems, and
1701 fails with -1/"ENOSYS" everywhere else. If anybody knows how to
1702 influence pipe buffer size on other systems, drop me a note.
1703
1704 ($rfh, $wfh) = IO::AIO::pipe2 [$flags]
1705 This is a direct interface to the Linux pipe2(2) system call. If
1706 $flags is missing or 0, then this should be the same as a call to
1707 perl's built-in "pipe" function and create a new pipe, and works on
1708 systems that lack the pipe2 syscall. On win32, this case invokes
1709 "_pipe (..., 4096, O_BINARY)".
1710
1711 If $flags is non-zero, it tries to invoke the pipe2 system call with
1712 the given flags (Linux 2.6.27, glibc 2.9).
1713
1714 On success, the read and write file handles are returned.
1715
1716 On error, nothing will be returned. If the pipe2 syscall is missing
1717 and $flags is non-zero, fails with "ENOSYS".
1718
1719 Please refer to pipe2(2) for more info on the $flags, but at the
1720 time of this writing, "IO::AIO::O_CLOEXEC", "IO::AIO::O_NONBLOCK"
1721 and "IO::AIO::O_DIRECT" (Linux 3.4, for packet-based pipes) were
1722 supported.
1723
1724EVENT LOOP INTEGRATION
1725 It is recommended to use AnyEvent::AIO to integrate IO::AIO
1726 automatically into many event loops:
1727
1728 # AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
1729 use AnyEvent::AIO;
1730
1731 You can also integrate IO::AIO manually into many event loops, here are
1732 some examples of how to do this:
1733
1734 # EV integration
1735 my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
1736
1737 # Event integration
1738 Event->io (fd => IO::AIO::poll_fileno,
1739 poll => 'r',
1740 cb => \&IO::AIO::poll_cb);
1741
1742 # Glib/Gtk2 integration
1743 add_watch Glib::IO IO::AIO::poll_fileno,
1744 in => sub { IO::AIO::poll_cb; 1 };
1745
1746 # Tk integration
1747 Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
1748 readable => \&IO::AIO::poll_cb);
1749
1750 # Danga::Socket integration
1751 Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
1752 \&IO::AIO::poll_cb);
838 1753
839 FORK BEHAVIOUR 1754 FORK BEHAVIOUR
840 This module should do "the right thing" when the process using it 1755 Usage of pthreads in a program changes the semantics of fork
841 forks: 1756 considerably. Specifically, only async-safe functions can be called
1757 after fork. Perl doesn't know about this, so in general, you cannot call
1758 fork with defined behaviour in perl if pthreads are involved. IO::AIO
1759 uses pthreads, so this applies, but many other extensions and (for
1760 inexplicable reasons) perl itself often is linked against pthreads, so
1761 this limitation applies to quite a lot of perls.
842 1762
843 Before the fork, IO::AIO enters a quiescent state where no requests 1763 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. 1764 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 1765 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 1766
852 In short: the parent will, after a short pause, continue as if fork 1767 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 1768 You could also try to call the IO::AIO::reinit function in the child:
854 been used yet. 1769
1770 IO::AIO::reinit
1771 Abandons all current requests and I/O threads and simply
1772 reinitialises all data structures. This is not an operation
1773 supported by any standards, but happens to work on GNU/Linux and
1774 some newer BSD systems.
1775
1776 The only reasonable use for this function is to call it after
1777 forking, if "IO::AIO" was used in the parent. Calling it while
1778 IO::AIO is active in the process will result in undefined behaviour.
1779 Calling it at any time will also result in any undefined (by POSIX)
1780 behaviour.
855 1781
856 MEMORY USAGE 1782 MEMORY USAGE
857 Per-request usage: 1783 Per-request usage:
858 1784
859 Each aio request uses - depending on your architecture - around 1785 Each aio request uses - depending on your architecture - around 100-200
860 100-200 bytes of memory. In addition, stat requests need a stat 1786 bytes of memory. In addition, stat requests need a stat buffer (possibly
861 buffer (possibly a few hundred bytes), readdir requires a result 1787 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 1788 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 1789 will consume memory till the request has entered the done state.
864 request has entered the done state.
865 1790
866 This is now awfully much, so queuing lots of requests is not usually 1791 This is not awfully much, so queuing lots of requests is not usually a
867 a problem. 1792 problem.
868 1793
869 Per-thread usage: 1794 Per-thread usage:
870 1795
871 In the execution phase, some aio requests require more memory for 1796 In the execution phase, some aio requests require more memory for
872 temporary buffers, and each thread requires a stack and other data 1797 temporary buffers, and each thread requires a stack and other data
873 structures (usually around 16k-128k, depending on the OS). 1798 structures (usually around 16k-128k, depending on the OS).
874 1799
875KNOWN BUGS 1800KNOWN BUGS
876 Known bugs will be fixed in the next release. 1801 Known bugs will be fixed in the next release.
877 1802
878SEE ALSO 1803SEE ALSO
879 Coro::AIO. 1804 AnyEvent::AIO for easy integration into event loops, Coro::AIO for a
1805 more natural syntax.
880 1806
881AUTHOR 1807AUTHOR
882 Marc Lehmann <schmorp@schmorp.de> 1808 Marc Lehmann <schmorp@schmorp.de>
883 http://home.schmorp.de/ 1809 http://home.schmorp.de/
884 1810

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