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

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