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Revision 1.22 by root, Sat Jan 6 02:47:11 2007 UTC

… …
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", 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
… …
58 but can also be used to easily do operations in parallel that are 59 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 60 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 61 faster on a RAID volume or over NFS when you do a number of stat
61 operations concurrently. 62 operations concurrently.
62 63
63 While this works on all types of file descriptors (for example sockets), 64 While most of this works on all types of file descriptors (for example
64 using these functions on file descriptors that support nonblocking 65 sockets), using these functions on file descriptors that support
65 operation (again, sockets, pipes etc.) is very inefficient. Use an event 66 nonblocking operation (again, sockets, pipes etc.) is very inefficient
67 or might not work (aio_read fails on sockets/pipes/fifos). Use an event
66 loop for that (such as the Event module): IO::AIO will naturally fit 68 loop for that (such as the Event module): IO::AIO will naturally fit
67 into such an event loop itself. 69 into such an event loop itself.
68 70
69 In this version, a number of threads are started that execute your 71 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 72 requests and signal their completion. You don't need thread support in
… …
94 poll => 'r', 96 poll => 'r',
95 cb => \&IO::AIO::poll_cb); 97 cb => \&IO::AIO::poll_cb);
96 98
97 # queue the request to open /etc/passwd 99 # queue the request to open /etc/passwd
98 aio_open "/etc/passwd", O_RDONLY, 0, sub { 100 aio_open "/etc/passwd", O_RDONLY, 0, sub {
99 my $fh = $_[0] 101 my $fh = shift
100 or die "error while opening: $!"; 102 or die "error while opening: $!";
101 103
102 # stat'ing filehandles is generally non-blocking 104 # stat'ing filehandles is generally non-blocking
103 my $size = -s $fh; 105 my $size = -s $fh;
104 106
… …
167 the actual aio request is severed and calling its methods will 169 the actual aio request is severed and calling its methods will
168 either do nothing or result in a runtime error). 170 either do nothing or result in a runtime error).
169 171
170FUNCTIONS 172FUNCTIONS
171 AIO REQUEST FUNCTIONS 173 AIO REQUEST FUNCTIONS
172 All the "aio_*" calls are more or less thin wrappers around the 174 All the "aio_*" calls are more or less thin wrappers around the syscall
173 syscall with the same name (sans "aio_"). The arguments are similar 175 with the same name (sans "aio_"). The arguments are similar or
174 or identical, and they all accept an additional (and optional) 176 identical, and they all accept an additional (and optional) $callback
175 $callback argument which must be a code reference. This code 177 argument which must be a code reference. This code reference will get
176 reference will get called with the syscall return code (e.g. most 178 called with the syscall return code (e.g. most syscalls return -1 on
177 syscalls return -1 on error, unlike perl, which usually delivers 179 error, unlike perl, which usually delivers "false") as it's sole
178 "false") as it's sole argument when the given syscall has been 180 argument when the given syscall has been executed asynchronously.
179 executed asynchronously.
180 181
181 All functions expecting a filehandle keep a copy of the filehandle 182 All functions expecting a filehandle keep a copy of the filehandle
182 internally until the request has finished. 183 internally until the request has finished.
183 184
184 All functions return request objects of type IO::AIO::REQ that allow 185 All functions return request objects of type IO::AIO::REQ that allow
185 further manipulation of those requests while they are in-flight. 186 further manipulation of those requests while they are in-flight.
186 187
187 The pathnames you pass to these routines *must* be absolute and 188 The pathnames you pass to these routines *must* be absolute and encoded
188 encoded as octets. The reason for the former is that at the time the 189 as octets. The reason for the former is that at the time the request is
189 request is being executed, the current working directory could have 190 being executed, the current working directory could have changed.
190 changed. Alternatively, you can make sure that you never change the 191 Alternatively, you can make sure that you never change the current
191 current working directory anywhere in the program and then use 192 working directory anywhere in the program and then use relative paths.
192 relative paths.
193 193
194 To encode pathnames as octets, either make sure you either: a) 194 To encode pathnames as octets, either make sure you either: a) always
195 always pass in filenames you got from outside (command line, readdir 195 pass in filenames you got from outside (command line, readdir etc.)
196 etc.) without tinkering, b) are ASCII or ISO 8859-1, c) use the 196 without tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module
197 Encode module and encode your pathnames to the locale (or other) 197 and encode your pathnames to the locale (or other) encoding in effect in
198 encoding in effect in the user environment, d) use 198 the user environment, d) use Glib::filename_from_unicode on unicode
199 Glib::filename_from_unicode on unicode filenames or e) use something 199 filenames or e) use something else to ensure your scalar has the correct
200 else to ensure your scalar has the correct contents. 200 contents.
201 201
202 This works, btw. independent of the internal UTF-8 bit, which 202 This works, btw. independent of the internal UTF-8 bit, which IO::AIO
203 IO::AIO handles correctly wether it is set or not. 203 handles correctly wether it is set or not.
204 204
205 $prev_pri = aioreq_pri [$pri] 205 $prev_pri = aioreq_pri [$pri]
206 Returns the priority value that would be used for the next 206 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 207 and, if $pri is given, sets the priority for the next aio request.
208 aio request.
209 208
210 The default priority is 0, the minimum and maximum priorities 209 The default priority is 0, the minimum and maximum priorities are -4
211 are -4 and 4, respectively. Requests with higher priority will 210 and 4, respectively. Requests with higher priority will be serviced
212 be serviced first. 211 first.
213 212
214 The priority will be reset to 0 after each call to one of the 213 The priority will be reset to 0 after each call to one of the
215 "aio_*" functions. 214 "aio_*" functions.
216 215
217 Example: open a file with low priority, then read something from 216 Example: open a file with low priority, then read something from it
218 it with higher priority so the read request is serviced before 217 with higher priority so the read request is serviced before other
219 other low priority open requests (potentially spamming the 218 low priority open requests (potentially spamming the cache):
220 cache):
221 219
220 aioreq_pri -3;
221 aio_open ..., sub {
222 return unless $_[0];
223
222 aioreq_pri -3; 224 aioreq_pri -2;
223 aio_open ..., sub {
224 return unless $_[0];
225
226 aioreq_pri -2;
227 aio_read $_[0], ..., sub { 225 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 ...; 226 ...
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 }; 227 };
571 }; 228 };
572 229
230 aioreq_nice $pri_adjust
231 Similar to "aioreq_pri", but subtracts the given value from the
232 current priority, so the effect is cumulative.
233
234 aio_open $pathname, $flags, $mode, $callback->($fh)
235 Asynchronously open or create a file and call the callback with a
236 newly created filehandle for the file.
237
238 The pathname passed to "aio_open" must be absolute. See API NOTES,
239 above, for an explanation.
240
241 The $flags argument is a bitmask. See the "Fcntl" module for a list.
242 They are the same as used by "sysopen".
243
244 Likewise, $mode specifies the mode of the newly created file, if it
245 didn't exist and "O_CREAT" has been given, just like perl's
246 "sysopen", except that it is mandatory (i.e. use 0 if you don't
247 create new files, and 0666 or 0777 if you do).
248
249 Example:
250
251 aio_open "/etc/passwd", O_RDONLY, 0, sub {
252 if ($_[0]) {
253 print "open successful, fh is $_[0]\n";
254 ...
255 } else {
256 die "open failed: $!\n";
257 }
258 };
259
260 aio_close $fh, $callback->($status)
261 Asynchronously close a file and call the callback with the result
262 code. *WARNING:* although accepted, you should not pass in a perl
263 filehandle here, as perl will likely close the file descriptor
264 another time when the filehandle is destroyed. Normally, you can
265 safely call perls "close" or just let filehandles go out of scope.
266
267 This is supposed to be a bug in the API, so that might change. It's
268 therefore best to avoid this function.
269
270 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
271 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
272 Reads or writes "length" bytes from the specified "fh" and "offset"
273 into the scalar given by "data" and offset "dataoffset" and calls
274 the callback without the actual number of bytes read (or -1 on
275 error, just like the syscall).
276
277 The $data scalar *MUST NOT* be modified in any way while the request
278 is outstanding. Modifying it can result in segfaults or WW3 (if the
279 necessary/optional hardware is installed).
280
281 Example: Read 15 bytes at offset 7 into scalar $buffer, starting at
282 offset 0 within the scalar:
283
284 aio_read $fh, 7, 15, $buffer, 0, sub {
285 $_[0] > 0 or die "read error: $!";
286 print "read $_[0] bytes: <$buffer>\n";
287 };
288
289 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
290 Tries to copy $length bytes from $in_fh to $out_fh. It starts
291 reading at byte offset $in_offset, and starts writing at the current
292 file offset of $out_fh. Because of that, it is not safe to issue
293 more than one "aio_sendfile" per $out_fh, as they will interfere
294 with each other.
295
296 This call tries to make use of a native "sendfile" syscall to
297 provide zero-copy operation. For this to work, $out_fh should refer
298 to a socket, and $in_fh should refer to mmap'able file.
299
300 If the native sendfile call fails or is not implemented, it will be
301 emulated, so you can call "aio_sendfile" on any type of filehandle
302 regardless of the limitations of the operating system.
303
304 Please note, however, that "aio_sendfile" can read more bytes from
305 $in_fh than are written, and there is no way to find out how many
306 bytes have been read from "aio_sendfile" alone, as "aio_sendfile"
307 only provides the number of bytes written to $out_fh. Only if the
308 result value equals $length one can assume that $length bytes have
309 been read.
310
311 aio_readahead $fh,$offset,$length, $callback->($retval)
312 "aio_readahead" populates the page cache with data from a file so
313 that subsequent reads from that file will not block on disk I/O. The
314 $offset argument specifies the starting point from which data is to
315 be read and $length specifies the number of bytes to be read. I/O is
316 performed in whole pages, so that offset is effectively rounded down
317 to a page boundary and bytes are read up to the next page boundary
318 greater than or equal to (off-set+length). "aio_readahead" does not
319 read beyond the end of the file. The current file offset of the file
320 is left unchanged.
321
322 If that syscall doesn't exist (likely if your OS isn't Linux) it
323 will be emulated by simply reading the data, which would have a
324 similar effect.
325
326 aio_stat $fh_or_path, $callback->($status)
327 aio_lstat $fh, $callback->($status)
328 Works like perl's "stat" or "lstat" in void context. The callback
329 will be called after the stat and the results will be available
330 using "stat _" or "-s _" etc...
331
332 The pathname passed to "aio_stat" must be absolute. See API NOTES,
333 above, for an explanation.
334
335 Currently, the stats are always 64-bit-stats, i.e. instead of
336 returning an error when stat'ing a large file, the results will be
337 silently truncated unless perl itself is compiled with large file
338 support.
339
340 Example: Print the length of /etc/passwd:
341
342 aio_stat "/etc/passwd", sub {
343 $_[0] and die "stat failed: $!";
344 print "size is ", -s _, "\n";
345 };
346
347 aio_unlink $pathname, $callback->($status)
348 Asynchronously unlink (delete) a file and call the callback with the
349 result code.
350
351 aio_mknod $path, $mode, $dev, $callback->($status)
352 [EXPERIMENTAL]
353
354 Asynchronously create a device node (or fifo). See mknod(2).
355
356 The only (POSIX-) portable way of calling this function is:
357
358 aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...
359
360 aio_link $srcpath, $dstpath, $callback->($status)
361 Asynchronously create a new link to the existing object at $srcpath
362 at the path $dstpath and call the callback with the result code.
363
364 aio_symlink $srcpath, $dstpath, $callback->($status)
365 Asynchronously create a new symbolic link to the existing object at
366 $srcpath at the path $dstpath and call the callback with the result
367 code.
368
369 aio_readlink $path, $callback->($link)
370 Asynchronously read the symlink specified by $path and pass it to
371 the callback. If an error occurs, nothing or undef gets passed to
372 the callback.
373
374 aio_rename $srcpath, $dstpath, $callback->($status)
375 Asynchronously rename the object at $srcpath to $dstpath, just as
376 rename(2) and call the callback with the result code.
377
378 aio_rmdir $pathname, $callback->($status)
379 Asynchronously rmdir (delete) a directory and call the callback with
380 the result code.
381
382 aio_readdir $pathname, $callback->($entries)
383 Unlike the POSIX call of the same name, "aio_readdir" reads an
384 entire directory (i.e. opendir + readdir + closedir). The entries
385 will not be sorted, and will NOT include the "." and ".." entries.
386
387 The callback a single argument which is either "undef" or an
388 array-ref with the filenames.
389
390 aio_load $path, $data, $callback->($status)
391 This is a composite request that tries to fully load the given file
392 into memory. Status is the same as with aio_read.
393
394 aio_copy $srcpath, $dstpath, $callback->($status)
395 Try to copy the *file* (directories not supported as either source
396 or destination) from $srcpath to $dstpath and call the callback with
397 the 0 (error) or -1 ok.
398
399 This is a composite request that it creates the destination file
400 with mode 0200 and copies the contents of the source file into it
401 using "aio_sendfile", followed by restoring atime, mtime, access
402 mode and uid/gid, in that order.
403
404 If an error occurs, the partial destination file will be unlinked,
405 if possible, except when setting atime, mtime, access mode and
406 uid/gid, where errors are being ignored.
407
408 aio_move $srcpath, $dstpath, $callback->($status)
409 Try to move the *file* (directories not supported as either source
410 or destination) from $srcpath to $dstpath and call the callback with
411 the 0 (error) or -1 ok.
412
413 This is a composite request that tries to rename(2) the file first.
414 If rename files with "EXDEV", it copies the file with "aio_copy"
415 and, if that is successful, unlinking the $srcpath.
416
417 aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
418 Scans a directory (similar to "aio_readdir") but additionally tries
419 to efficiently separate the entries of directory $path into two sets
420 of names, directories you can recurse into (directories), and ones
421 you cannot recurse into (everything else, including symlinks to
422 directories).
423
424 "aio_scandir" is a composite request that creates of many sub
425 requests_ $maxreq specifies the maximum number of outstanding aio
426 requests that this function generates. If it is "<= 0", then a
427 suitable default will be chosen (currently 4).
428
429 On error, the callback is called without arguments, otherwise it
430 receives two array-refs with path-relative entry names.
431
432 Example:
433
434 aio_scandir $dir, 0, sub {
435 my ($dirs, $nondirs) = @_;
436 print "real directories: @$dirs\n";
437 print "everything else: @$nondirs\n";
438 };
439
440 Implementation notes.
441
442 The "aio_readdir" cannot be avoided, but "stat()"'ing every entry
443 can.
444
445 After reading the directory, the modification time, size etc. of the
446 directory before and after the readdir is checked, and if they match
447 (and isn't the current time), the link count will be used to decide
448 how many entries are directories (if >= 2). Otherwise, no knowledge
449 of the number of subdirectories will be assumed.
450
451 Then entries will be sorted into likely directories (everything
452 without a non-initial dot currently) and likely non-directories
453 (everything else). Then every entry plus an appended "/." will be
454 "stat"'ed, likely directories first. If that succeeds, it assumes
455 that the entry is a directory or a symlink to directory (which will
456 be checked seperately). This is often faster than stat'ing the entry
457 itself because filesystems might detect the type of the entry
458 without reading the inode data (e.g. ext2fs filetype feature).
459
460 If the known number of directories (link count - 2) has been
461 reached, the rest of the entries is assumed to be non-directories.
462
463 This only works with certainty on POSIX (= UNIX) filesystems, which
464 fortunately are the vast majority of filesystems around.
465
466 It will also likely work on non-POSIX filesystems with reduced
467 efficiency as those tend to return 0 or 1 as link counts, which
468 disables the directory counting heuristic.
469
470 aio_fsync $fh, $callback->($status)
471 Asynchronously call fsync on the given filehandle and call the
472 callback with the fsync result code.
473
474 aio_fdatasync $fh, $callback->($status)
475 Asynchronously call fdatasync on the given filehandle and call the
476 callback with the fdatasync result code.
477
478 If this call isn't available because your OS lacks it or it couldn't
479 be detected, it will be emulated by calling "fsync" instead.
480
481 aio_group $callback->(...)
482 This is a very special aio request: Instead of doing something, it
483 is a container for other aio requests, which is useful if you want
484 to bundle many requests into a single, composite, request with a
485 definite callback and the ability to cancel the whole request with
486 its subrequests.
487
488 Returns an object of class IO::AIO::GRP. See its documentation below
489 for more info.
490
491 Example:
492
493 my $grp = aio_group sub {
494 print "all stats done\n";
495 };
496
497 add $grp
498 (aio_stat ...),
499 (aio_stat ...),
500 ...;
501
502 aio_nop $callback->()
503 This is a special request - it does nothing in itself and is only
504 used for side effects, such as when you want to add a dummy request
505 to a group so that finishing the requests in the group depends on
506 executing the given code.
507
508 While this request does nothing, it still goes through the execution
509 phase and still requires a worker thread. Thus, the callback will
510 not be executed immediately but only after other requests in the
511 queue have entered their execution phase. This can be used to
512 measure request latency.
513
514 IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
515 Mainly used for debugging and benchmarking, this aio request puts
516 one of the request workers to sleep for the given time.
517
518 While it is theoretically handy to have simple I/O scheduling
519 requests like sleep and file handle readable/writable, the overhead
520 this creates is immense (it blocks a thread for a long time) so do
521 not use this function except to put your application under
522 artificial I/O pressure.
523
524 IO::AIO::REQ CLASS
525 All non-aggregate "aio_*" functions return an object of this class when
526 called in non-void context.
527
528 cancel $req
529 Cancels the request, if possible. Has the effect of skipping
530 execution when entering the execute state and skipping calling the
531 callback when entering the the result state, but will leave the
532 request otherwise untouched. That means that requests that currently
533 execute will not be stopped and resources held by the request will
534 not be freed prematurely.
535
536 cb $req $callback->(...)
537 Replace (or simply set) the callback registered to the request.
538
539 IO::AIO::GRP CLASS
540 This class is a subclass of IO::AIO::REQ, so all its methods apply to
541 objects of this class, too.
542
543 A IO::AIO::GRP object is a special request that can contain multiple
544 other aio requests.
545
546 You create one by calling the "aio_group" constructing function with a
547 callback that will be called when all contained requests have entered
548 the "done" state:
549
550 my $grp = aio_group sub {
551 print "all requests are done\n";
552 };
553
554 You add requests by calling the "add" method with one or more
555 "IO::AIO::REQ" objects:
556
557 $grp->add (aio_unlink "...");
558
559 add $grp aio_stat "...", sub {
560 $_[0] or return $grp->result ("error");
561
562 # add another request dynamically, if first succeeded
563 add $grp aio_open "...", sub {
564 $grp->result ("ok");
565 };
566 };
567
573 This makes it very easy to create composite requests (see the source 568 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 569 "aio_move" for an application) that work and feel like simple requests.
575 requests.
576 570
577 * The IO::AIO::GRP objects will be cleaned up during calls to 571 * The IO::AIO::GRP objects will be cleaned up during calls to
578 "IO::AIO::poll_cb", just like any other request. 572 "IO::AIO::poll_cb", just like any other request.
579 * They can be canceled like any other request. Canceling will cancel 573 * They can be canceled like any other request. Canceling will cancel not
580 not only the request itself, but also all requests it contains. 574 only the request itself, but also all requests it contains.
581 * They can also can also be added to other IO::AIO::GRP objects. 575 * They can also can also be added to other IO::AIO::GRP objects.
582 * You must not add requests to a group from within the group 576 * You must not add requests to a group from within the group callback
583 callback (or any later time). 577 (or any later time).
584 578
585 Their lifetime, simplified, looks like this: when they are empty, 579 Their lifetime, simplified, looks like this: when they are empty, they
586 they will finish very quickly. If they contain only requests that 580 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 581 "done" state, they will also finish. Otherwise they will continue to
588 continue to exist. 582 exist.
589 583
590 That means after creating a group you have some time to add 584 That means after creating a group you have some time to add requests.
591 requests. And in the callbacks of those requests, you can add 585 And in the callbacks of those requests, you can add further requests to
592 further requests to the group. And only when all those requests have 586 the group. And only when all those requests have finished will the the
593 finished will the the group itself finish. 587 group itself finish.
594 588
595 add $grp ... 589 add $grp ...
596 $grp->add (...) 590 $grp->add (...)
597 Add one or more requests to the group. Any type of IO::AIO::REQ 591 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 592 be added, including other groups, as long as you do not create
599 create circular dependencies. 593 circular dependencies.
600 594
601 Returns all its arguments. 595 Returns all its arguments.
602 596
603 $grp->cancel_subs 597 $grp->cancel_subs
604 Cancel all subrequests and clears any feeder, but not the group 598 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 599 request itself. Useful when you queued a lot of events but got a
606 result early. 600 result early.
607 601
608 $grp->result (...) 602 $grp->result (...)
609 Set the result value(s) that will be passed to the group 603 Set the result value(s) that will be passed to the group callback
610 callback when all subrequests have finished and set thre groups 604 when all subrequests have finished and set thre groups errno to the
611 errno to the current value of errno (just like calling "errno" 605 current value of errno (just like calling "errno" without an error
612 without an error number). By default, no argument will be passed 606 number). By default, no argument will be passed and errno is zero.
613 and errno is zero.
614 607
615 $grp->errno ([$errno]) 608 $grp->errno ([$errno])
616 Sets the group errno value to $errno, or the current value of 609 Sets the group errno value to $errno, or the current value of errno
617 errno when the argument is missing. 610 when the argument is missing.
618 611
619 Every aio request has an associated errno value that is restored 612 Every aio request has an associated errno value that is restored
620 when the callback is invoked. This method lets you change this 613 when the callback is invoked. This method lets you change this value
621 value from its default (0). 614 from its default (0).
622 615
623 Calling "result" will also set errno, so make sure you either 616 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. 617 before the call to "result", or call c<errno> after it.
625 618
626 feed $grp $callback->($grp) 619 feed $grp $callback->($grp)
627 Sets a feeder/generator on this group: every group can have an 620 Sets a feeder/generator on this group: every group can have an
628 attached generator that generates requests if idle. The idea 621 attached generator that generates requests if idle. The idea behind
629 behind this is that, although you could just queue as many 622 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 623 want in a group, this might starve other requests for a potentially
631 requests for a potentially long time. For example, "aio_scandir" 624 long time. For example, "aio_scandir" might generate hundreds of
632 might generate hundreds of thousands "aio_stat" requests, 625 thousands "aio_stat" requests, delaying any later requests for a
633 delaying any later requests for a long time. 626 long time.
634 627
635 To avoid this, and allow incremental generation of requests, you 628 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 629 instead a group and set a feeder on it that generates those
637 requests. The feed callback will be called whenever there are 630 requests. The feed callback will be called whenever there are few
638 few enough (see "limit", below) requests active in the group 631 enough (see "limit", below) requests active in the group itself and
639 itself and is expected to queue more requests. 632 is expected to queue more requests.
640 633
641 The feed callback can queue as many requests as it likes (i.e. 634 The feed callback can queue as many requests as it likes (i.e. "add"
642 "add" does not impose any limits). 635 does not impose any limits).
643 636
644 If the feed does not queue more requests when called, it will be 637 If the feed does not queue more requests when called, it will be
645 automatically removed from the group. 638 automatically removed from the group.
646 639
647 If the feed limit is 0, it will be set to 2 automatically. 640 If the feed limit is 0, it will be set to 2 automatically.
648 641
649 Example: 642 Example:
650 643
651 # stat all files in @files, but only ever use four aio requests concurrently: 644 # stat all files in @files, but only ever use four aio requests concurrently:
652 645
653 my $grp = aio_group sub { print "finished\n" }; 646 my $grp = aio_group sub { print "finished\n" };
654 limit $grp 4; 647 limit $grp 4;
655 feed $grp sub { 648 feed $grp sub {
656 my $file = pop @files 649 my $file = pop @files
657 or return; 650 or return;
658 651
659 add $grp aio_stat $file, sub { ... }; 652 add $grp aio_stat $file, sub { ... };
660 }; 653 };
661 654
662 limit $grp $num 655 limit $grp $num
663 Sets the feeder limit for the group: The feeder will be called 656 Sets the feeder limit for the group: The feeder will be called
664 whenever the group contains less than this many requests. 657 whenever the group contains less than this many requests.
665 658
666 Setting the limit to 0 will pause the feeding process. 659 Setting the limit to 0 will pause the feeding process.
667 660
668 SUPPORT FUNCTIONS 661 SUPPORT FUNCTIONS
669 EVENT PROCESSING AND EVENT LOOP INTEGRATION 662 EVENT PROCESSING AND EVENT LOOP INTEGRATION
670 $fileno = IO::AIO::poll_fileno 663 $fileno = IO::AIO::poll_fileno
671 Return the *request result pipe file descriptor*. This 664 Return the *request result pipe file descriptor*. This filehandle
672 filehandle must be polled for reading by some mechanism outside 665 must be polled for reading by some mechanism outside this module
673 this module (e.g. Event or select, see below or the SYNOPSIS). 666 (e.g. Event or select, see below or the SYNOPSIS). If the pipe
674 If the pipe becomes readable you have to call "poll_cb" to check 667 becomes readable you have to call "poll_cb" to check the results.
675 the results.
676 668
677 See "poll_cb" for an example. 669 See "poll_cb" for an example.
678 670
679 IO::AIO::poll_cb 671 IO::AIO::poll_cb
680 Process some outstanding events on the result pipe. You have to 672 Process some outstanding events on the result pipe. You have to call
681 call this regularly. Returns the number of events processed. 673 this regularly. Returns the number of events processed. Returns
682 Returns immediately when no events are outstanding. The amount 674 immediately when no events are outstanding. The amount of events
683 of events processed depends on the settings of 675 processed depends on the settings of "IO::AIO::max_poll_req" and
684 "IO::AIO::max_poll_req" and "IO::AIO::max_poll_time". 676 "IO::AIO::max_poll_time".
685 677
686 If not all requests were processed for whatever reason, the 678 If not all requests were processed for whatever reason, the
687 filehandle will still be ready when "poll_cb" returns. 679 filehandle will still be ready when "poll_cb" returns.
688 680
689 Example: Install an Event watcher that automatically calls 681 Example: Install an Event watcher that automatically calls
690 IO::AIO::poll_cb with high priority: 682 IO::AIO::poll_cb with high priority:
691 683
692 Event->io (fd => IO::AIO::poll_fileno, 684 Event->io (fd => IO::AIO::poll_fileno,
693 poll => 'r', async => 1, 685 poll => 'r', async => 1,
694 cb => \&IO::AIO::poll_cb); 686 cb => \&IO::AIO::poll_cb);
695 687
696 IO::AIO::max_poll_reqs $nreqs 688 IO::AIO::max_poll_reqs $nreqs
697 IO::AIO::max_poll_time $seconds 689 IO::AIO::max_poll_time $seconds
698 These set the maximum number of requests (default 0, meaning 690 These set the maximum number of requests (default 0, meaning
699 infinity) that are being processed by "IO::AIO::poll_cb" in one 691 infinity) that are being processed by "IO::AIO::poll_cb" in one
700 call, respectively the maximum amount of time (default 0, 692 call, respectively the maximum amount of time (default 0, meaning
701 meaning infinity) spent in "IO::AIO::poll_cb" to process 693 infinity) spent in "IO::AIO::poll_cb" to process requests (more
702 requests (more correctly the mininum amount of time "poll_cb" is 694 correctly the mininum amount of time "poll_cb" is allowed to use).
703 allowed to use).
704 695
696 Setting "max_poll_time" to a non-zero value creates an overhead of
697 one syscall per request processed, which is not normally a problem
698 unless your callbacks are really really fast or your OS is really
699 really slow (I am not mentioning Solaris here). Using
700 "max_poll_reqs" incurs no overhead.
701
705 Setting these is useful if you want to ensure some level of 702 Setting these is useful if you want to ensure some level of
706 interactiveness when perl is not fast enough to process all 703 interactiveness when perl is not fast enough to process all requests
707 requests in time. 704 in time.
708 705
709 For interactive programs, values such as 0.01 to 0.1 should be 706 For interactive programs, values such as 0.01 to 0.1 should be fine.
710 fine.
711 707
712 Example: Install an Event watcher that automatically calls 708 Example: Install an Event watcher that automatically calls
713 IO::AIO::poll_some with low priority, to ensure that other parts 709 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. 710 the program get the CPU sometimes even under high AIO load.
715 711
716 # try not to spend much more than 0.1s in poll_cb 712 # try not to spend much more than 0.1s in poll_cb
717 IO::AIO::max_poll_time 0.1; 713 IO::AIO::max_poll_time 0.1;
718 714
719 # use a low priority so other tasks have priority 715 # use a low priority so other tasks have priority
720 Event->io (fd => IO::AIO::poll_fileno, 716 Event->io (fd => IO::AIO::poll_fileno,
721 poll => 'r', nice => 1, 717 poll => 'r', nice => 1,
722 cb => &IO::AIO::poll_cb); 718 cb => &IO::AIO::poll_cb);
723 719
724 IO::AIO::poll_wait 720 IO::AIO::poll_wait
721 If there are any outstanding requests and none of them in the result
725 Wait till the result filehandle becomes ready for reading 722 phase, wait till the result filehandle becomes ready for reading
726 (simply does a "select" on the filehandle. This is useful if you 723 (simply does a "select" on the filehandle. This is useful if you
727 want to synchronously wait for some requests to finish). 724 want to synchronously wait for some requests to finish).
728 725
729 See "nreqs" for an example. 726 See "nreqs" for an example.
730 727
731 IO::AIO::poll 728 IO::AIO::poll
732 Waits until some requests have been handled. 729 Waits until some requests have been handled.
733 730
731 Returns the number of requests processed, but is otherwise strictly
734 Strictly equivalent to: 732 equivalent to:
735 733
736 IO::AIO::poll_wait, IO::AIO::poll_cb 734 IO::AIO::poll_wait, IO::AIO::poll_cb
737 if IO::AIO::nreqs;
738 735
739 IO::AIO::flush 736 IO::AIO::flush
740 Wait till all outstanding AIO requests have been handled. 737 Wait till all outstanding AIO requests have been handled.
741 738
742 Strictly equivalent to: 739 Strictly equivalent to:
743 740
744 IO::AIO::poll_wait, IO::AIO::poll_cb 741 IO::AIO::poll_wait, IO::AIO::poll_cb
745 while IO::AIO::nreqs; 742 while IO::AIO::nreqs;
746 743
747 CONTROLLING THE NUMBER OF THREADS 744 CONTROLLING THE NUMBER OF THREADS
748 IO::AIO::min_parallel $nthreads 745 IO::AIO::min_parallel $nthreads
749 Set the minimum number of AIO threads to $nthreads. The current 746 Set the minimum number of AIO threads to $nthreads. The current
750 default is 8, which means eight asynchronous operations can 747 default is 8, which means eight asynchronous operations can execute
751 execute concurrently at any one time (the number of outstanding 748 concurrently at any one time (the number of outstanding requests,
752 requests, however, is unlimited). 749 however, is unlimited).
753 750
754 IO::AIO starts threads only on demand, when an AIO request is 751 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 752 and no free thread exists. Please note that queueing up a hundred
756 hundred requests can create demand for a hundred threads, even 753 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 754 out that everything is in the cache and could have been processed
758 been processed faster by a single thread. 755 faster by a single thread.
759 756
760 It is recommended to keep the number of threads relatively low, 757 It is recommended to keep the number of threads relatively low, as
761 as some Linux kernel versions will scale negatively with the 758 some Linux kernel versions will scale negatively with the number of
762 number of threads (higher parallelity => MUCH higher latency). 759 threads (higher parallelity => MUCH higher latency). With current
763 With current Linux 2.6 versions, 4-32 threads should be fine. 760 Linux 2.6 versions, 4-32 threads should be fine.
764 761
765 Under most circumstances you don't need to call this function, 762 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 763 the module selects a default that is suitable for low to moderate
767 moderate load. 764 load.
768 765
769 IO::AIO::max_parallel $nthreads 766 IO::AIO::max_parallel $nthreads
770 Sets the maximum number of AIO threads to $nthreads. If more 767 Sets the maximum number of AIO threads to $nthreads. If more than
771 than the specified number of threads are currently running, this 768 the specified number of threads are currently running, this function
772 function kills them. This function blocks until the limit is 769 kills them. This function blocks until the limit is reached.
773 reached.
774 770
775 While $nthreads are zero, aio requests get queued but not 771 While $nthreads are zero, aio requests get queued but not executed
776 executed until the number of threads has been increased again. 772 until the number of threads has been increased again.
777 773
778 This module automatically runs "max_parallel 0" at program end, 774 This module automatically runs "max_parallel 0" at program end, to
779 to ensure that all threads are killed and that there are no 775 ensure that all threads are killed and that there are no outstanding
780 outstanding requests. 776 requests.
781 777
782 Under normal circumstances you don't need to call this function. 778 Under normal circumstances you don't need to call this function.
783 779
784 IO::AIO::max_idle $nthreads 780 IO::AIO::max_idle $nthreads
785 Limit the number of threads (default: 4) that are allowed to 781 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 782 (i.e., threads that did not get a request to process within 10
787 10 seconds). That means if a thread becomes idle while $nthreads 783 seconds). That means if a thread becomes idle while $nthreads other
788 other threads are also idle, it will free its resources and 784 threads are also idle, it will free its resources and exit.
789 exit.
790 785
791 This is useful when you allow a large number of threads (e.g. 786 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 787 1000) to allow for extremely high load situations, but want to free
793 want to free resources under normal circumstances (1000 threads 788 resources under normal circumstances (1000 threads can easily
794 can easily consume 30MB of RAM). 789 consume 30MB of RAM).
795 790
796 The default is probably ok in most situations, especially if 791 The default is probably ok in most situations, especially if thread
797 thread creation is fast. If thread creation is very slow on your 792 creation is fast. If thread creation is very slow on your system you
798 system you might want to use larger values. 793 might want to use larger values.
799 794
800 $oldmaxreqs = IO::AIO::max_outstanding $maxreqs 795 $oldmaxreqs = IO::AIO::max_outstanding $maxreqs
801 This is a very bad function to use in interactive programs 796 This is a very bad function to use in interactive programs because
802 because it blocks, and a bad way to reduce concurrency because 797 it blocks, and a bad way to reduce concurrency because it is
803 it is inexact: Better use an "aio_group" together with a feed 798 inexact: Better use an "aio_group" together with a feed callback.
804 callback.
805 799
806 Sets the maximum number of outstanding requests to $nreqs. If 800 Sets the maximum number of outstanding requests to $nreqs. If you to
807 you to queue up more than this number of requests, the next call 801 queue up more than this number of requests, the next call to the
808 to the "poll_cb" (and "poll_some" and other functions calling 802 "poll_cb" (and "poll_some" and other functions calling "poll_cb")
809 "poll_cb") function will block until the limit is no longer 803 function will block until the limit is no longer exceeded.
810 exceeded.
811 804
812 The default value is very large, so there is no practical limit 805 The default value is very large, so there is no practical limit on
813 on the number of outstanding requests. 806 the number of outstanding requests.
814 807
815 You can still queue as many requests as you want. Therefore, 808 You can still queue as many requests as you want. Therefore,
816 "max_oustsanding" is mainly useful in simple scripts (with low 809 "max_oustsanding" is mainly useful in simple scripts (with low
817 values) or as a stop gap to shield against fatal memory overflow 810 values) or as a stop gap to shield against fatal memory overflow
818 (with large values). 811 (with large values).
819 812
820 STATISTICAL INFORMATION 813 STATISTICAL INFORMATION
821 IO::AIO::nreqs 814 IO::AIO::nreqs
822 Returns the number of requests currently in the ready, execute 815 Returns the number of requests currently in the ready, execute or
823 or pending states (i.e. for which their callback has not been 816 pending states (i.e. for which their callback has not been invoked
824 invoked yet). 817 yet).
825 818
826 Example: wait till there are no outstanding requests anymore: 819 Example: wait till there are no outstanding requests anymore:
827 820
828 IO::AIO::poll_wait, IO::AIO::poll_cb 821 IO::AIO::poll_wait, IO::AIO::poll_cb
829 while IO::AIO::nreqs; 822 while IO::AIO::nreqs;
830 823
831 IO::AIO::nready 824 IO::AIO::nready
832 Returns the number of requests currently in the ready state (not 825 Returns the number of requests currently in the ready state (not yet
833 yet executed). 826 executed).
834 827
835 IO::AIO::npending 828 IO::AIO::npending
836 Returns the number of requests currently in the pending state 829 Returns the number of requests currently in the pending state
837 (executed, but not yet processed by poll_cb). 830 (executed, but not yet processed by poll_cb).
838 831
839 FORK BEHAVIOUR 832 FORK BEHAVIOUR
840 This module should do "the right thing" when the process using it 833 This module should do "the right thing" when the process using it forks:
841 forks:
842 834
843 Before the fork, IO::AIO enters a quiescent state where no requests 835 Before the fork, IO::AIO enters a quiescent state where no requests can
844 can be added in other threads and no results will be processed. 836 be added in other threads and no results will be processed. After the
845 After the fork the parent simply leaves the quiescent state and 837 fork the parent simply leaves the quiescent state and continues
846 continues request/result processing, while the child frees the 838 request/result processing, while the child frees the request/result
847 request/result queue (so that the requests started before the fork 839 queue (so that the requests started before the fork will only be handled
848 will only be handled in the parent). Threads will be started on 840 in the parent). Threads will be started on demand until the limit set in
849 demand until the limit set in the parent process has been reached 841 the parent process has been reached again.
850 again.
851 842
852 In short: the parent will, after a short pause, continue as if fork 843 In short: the parent will, after a short pause, continue as if fork had
853 had not been called, while the child will act as if IO::AIO has not 844 not been called, while the child will act as if IO::AIO has not been
854 been used yet. 845 used yet.
855 846
856 MEMORY USAGE 847 MEMORY USAGE
857 Per-request usage: 848 Per-request usage:
858 849
859 Each aio request uses - depending on your architecture - around 850 Each aio request uses - depending on your architecture - around 100-200
860 100-200 bytes of memory. In addition, stat requests need a stat 851 bytes of memory. In addition, stat requests need a stat buffer (possibly
861 buffer (possibly a few hundred bytes), readdir requires a result 852 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 853 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 854 will consume memory till the request has entered the done state.
864 request has entered the done state.
865 855
866 This is now awfully much, so queuing lots of requests is not usually 856 This is now awfully much, so queuing lots of requests is not usually a
867 a problem. 857 problem.
868 858
869 Per-thread usage: 859 Per-thread usage:
870 860
871 In the execution phase, some aio requests require more memory for 861 In the execution phase, some aio requests require more memory for
872 temporary buffers, and each thread requires a stack and other data 862 temporary buffers, and each thread requires a stack and other data
873 structures (usually around 16k-128k, depending on the OS). 863 structures (usually around 16k-128k, depending on the OS).
874 864
875KNOWN BUGS 865KNOWN BUGS
876 Known bugs will be fixed in the next release. 866 Known bugs will be fixed in the next release.
877 867
878SEE ALSO 868SEE ALSO
879 Coro::AIO. 869 Coro::AIO.
880 870
881AUTHOR 871AUTHOR
882 Marc Lehmann <schmorp@schmorp.de> 872 Marc Lehmann <schmorp@schmorp.de>
883 http://home.schmorp.de/ 873 http://home.schmorp.de/
884 874

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