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Revision 1.23 by root, Mon Jan 22 15:59:52 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). Note that the $mode
248 will be modified by the umask in effect then the request is being
249 executed, so better never change the umask.
250
251 Example:
252
253 aio_open "/etc/passwd", O_RDONLY, 0, sub {
254 if ($_[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 result
264 code. *WARNING:* although accepted, you should not pass in a perl
265 filehandle here, as perl will likely close the file descriptor
266 another time when the filehandle is destroyed. Normally, you can
267 safely call perls "close" or just let filehandles go out of scope.
268
269 This is supposed to be a bug in the API, so that might change. It's
270 therefore best to avoid this function.
271
272 aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
273 aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
274 Reads or writes "length" bytes from the specified "fh" and "offset"
275 into the scalar given by "data" and offset "dataoffset" and calls
276 the callback without the actual number of bytes read (or -1 on
277 error, just like the syscall).
278
279 The $data scalar *MUST NOT* be modified in any way while the request
280 is outstanding. Modifying it can result in segfaults or WW3 (if the
281 necessary/optional hardware is installed).
282
283 Example: Read 15 bytes at offset 7 into scalar $buffer, starting at
284 offset 0 within the scalar:
285
286 aio_read $fh, 7, 15, $buffer, 0, sub {
287 $_[0] > 0 or die "read error: $!";
288 print "read $_[0] bytes: <$buffer>\n";
289 };
290
291 aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
292 Tries to copy $length bytes from $in_fh to $out_fh. It starts
293 reading at byte offset $in_offset, and starts writing at the current
294 file offset of $out_fh. Because of that, it is not safe to issue
295 more than one "aio_sendfile" per $out_fh, as they will interfere
296 with each other.
297
298 This call tries to make use of a native "sendfile" syscall to
299 provide zero-copy operation. For this to work, $out_fh should refer
300 to a socket, and $in_fh should refer to mmap'able file.
301
302 If the native sendfile call fails or is not implemented, it will be
303 emulated, so you can call "aio_sendfile" on any type of filehandle
304 regardless of the limitations of the operating system.
305
306 Please note, however, that "aio_sendfile" can read more bytes from
307 $in_fh than are written, and there is no way to find out how many
308 bytes have been read from "aio_sendfile" alone, as "aio_sendfile"
309 only provides the number of bytes written to $out_fh. Only if the
310 result value equals $length one can assume that $length bytes have
311 been read.
312
313 aio_readahead $fh,$offset,$length, $callback->($retval)
314 "aio_readahead" populates the page cache with data from a file so
315 that subsequent reads from that file will not block on disk I/O. The
316 $offset argument specifies the starting point from which data is to
317 be read and $length specifies the number of bytes to be read. I/O is
318 performed in whole pages, so that offset is effectively rounded down
319 to a page boundary and bytes are read up to the next page boundary
320 greater than or equal to (off-set+length). "aio_readahead" does not
321 read beyond the end of the file. The current file offset of the file
322 is left unchanged.
323
324 If that syscall doesn't exist (likely if your OS isn't Linux) it
325 will be emulated by simply reading the data, which would have a
326 similar effect.
327
328 aio_stat $fh_or_path, $callback->($status)
329 aio_lstat $fh, $callback->($status)
330 Works like perl's "stat" or "lstat" in void context. The callback
331 will be called after the stat and the results will be available
332 using "stat _" or "-s _" etc...
333
334 The pathname passed to "aio_stat" must be absolute. See API NOTES,
335 above, for an explanation.
336
337 Currently, the stats are always 64-bit-stats, i.e. instead of
338 returning an error when stat'ing a large file, the results will be
339 silently truncated unless perl itself is compiled with large file
340 support.
341
342 Example: Print the length of /etc/passwd:
343
344 aio_stat "/etc/passwd", sub {
345 $_[0] and die "stat failed: $!";
346 print "size is ", -s _, "\n";
347 };
348
349 aio_unlink $pathname, $callback->($status)
350 Asynchronously unlink (delete) a file and call the callback with the
351 result code.
352
353 aio_mknod $path, $mode, $dev, $callback->($status)
354 [EXPERIMENTAL]
355
356 Asynchronously create a device node (or fifo). See mknod(2).
357
358 The only (POSIX-) portable way of calling this function is:
359
360 aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...
361
362 aio_link $srcpath, $dstpath, $callback->($status)
363 Asynchronously create a new link to the existing object at $srcpath
364 at the path $dstpath and call the callback with the result code.
365
366 aio_symlink $srcpath, $dstpath, $callback->($status)
367 Asynchronously create a new symbolic link to the existing object at
368 $srcpath at the path $dstpath and call the callback with the result
369 code.
370
371 aio_readlink $path, $callback->($link)
372 Asynchronously read the symlink specified by $path and pass it to
373 the callback. If an error occurs, nothing or undef gets passed to
374 the callback.
375
376 aio_rename $srcpath, $dstpath, $callback->($status)
377 Asynchronously rename the object at $srcpath to $dstpath, just as
378 rename(2) and call the callback with the result code.
379
380 aio_mkdir $pathname, $mode, $callback->($status)
381 Asynchronously mkdir (create) a directory and call the callback with
382 the result code. $mode will be modified by the umask at the time the
383 request is executed, so do not change your umask.
384
385 aio_rmdir $pathname, $callback->($status)
386 Asynchronously rmdir (delete) a directory and call the callback with
387 the result code.
388
389 aio_readdir $pathname, $callback->($entries)
390 Unlike the POSIX call of the same name, "aio_readdir" reads an
391 entire directory (i.e. opendir + readdir + closedir). The entries
392 will not be sorted, and will NOT include the "." and ".." entries.
393
394 The callback a single argument which is either "undef" or an
395 array-ref with the filenames.
396
397 aio_load $path, $data, $callback->($status)
398 This is a composite request that tries to fully load the given file
399 into memory. Status is the same as with aio_read.
400
401 aio_copy $srcpath, $dstpath, $callback->($status)
402 Try to copy the *file* (directories not supported as either source
403 or destination) from $srcpath to $dstpath and call the callback with
404 the 0 (error) or -1 ok.
405
406 This is a composite request that it creates the destination file
407 with mode 0200 and copies the contents of the source file into it
408 using "aio_sendfile", followed by restoring atime, mtime, access
409 mode and uid/gid, in that order.
410
411 If an error occurs, the partial destination file will be unlinked,
412 if possible, except when setting atime, mtime, access mode and
413 uid/gid, where errors are being ignored.
414
415 aio_move $srcpath, $dstpath, $callback->($status)
416 Try to move the *file* (directories not supported as either source
417 or destination) from $srcpath to $dstpath and call the callback with
418 the 0 (error) or -1 ok.
419
420 This is a composite request that tries to rename(2) the file first.
421 If rename files with "EXDEV", it copies the file with "aio_copy"
422 and, if that is successful, unlinking the $srcpath.
423
424 aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)
425 Scans a directory (similar to "aio_readdir") but additionally tries
426 to efficiently separate the entries of directory $path into two sets
427 of names, directories you can recurse into (directories), and ones
428 you cannot recurse into (everything else, including symlinks to
429 directories).
430
431 "aio_scandir" is a composite request that creates of many sub
432 requests_ $maxreq specifies the maximum number of outstanding aio
433 requests that this function generates. If it is "<= 0", then a
434 suitable default will be chosen (currently 4).
435
436 On error, the callback is called without arguments, otherwise it
437 receives two array-refs with path-relative entry names.
438
439 Example:
440
441 aio_scandir $dir, 0, sub {
442 my ($dirs, $nondirs) = @_;
443 print "real directories: @$dirs\n";
444 print "everything else: @$nondirs\n";
445 };
446
447 Implementation notes.
448
449 The "aio_readdir" cannot be avoided, but "stat()"'ing every entry
450 can.
451
452 After reading the directory, the modification time, size etc. of the
453 directory before and after the readdir is checked, and if they match
454 (and isn't the current time), the link count will be used to decide
455 how many entries are directories (if >= 2). Otherwise, no knowledge
456 of the number of subdirectories will be assumed.
457
458 Then entries will be sorted into likely directories (everything
459 without a non-initial dot currently) and likely non-directories
460 (everything else). Then every entry plus an appended "/." will be
461 "stat"'ed, likely directories first. If that succeeds, it assumes
462 that the entry is a directory or a symlink to directory (which will
463 be checked seperately). This is often faster than stat'ing the entry
464 itself because filesystems might detect the type of the entry
465 without reading the inode data (e.g. ext2fs filetype feature).
466
467 If the known number of directories (link count - 2) has been
468 reached, the rest of the entries is assumed to be non-directories.
469
470 This only works with certainty on POSIX (= UNIX) filesystems, which
471 fortunately are the vast majority of filesystems around.
472
473 It will also likely work on non-POSIX filesystems with reduced
474 efficiency as those tend to return 0 or 1 as link counts, which
475 disables the directory counting heuristic.
476
477 aio_rmtree $path, $callback->($status)
478 Delete a directory tree starting (and including) $path, return the
479 status of the final "rmdir" only. This is a composite request that
480 uses "aio_scandir" to recurse into and rmdir directories, and unlink
481 everything else.
482
483 aio_fsync $fh, $callback->($status)
484 Asynchronously call fsync on the given filehandle and call the
485 callback with the fsync result code.
486
487 aio_fdatasync $fh, $callback->($status)
488 Asynchronously call fdatasync on the given filehandle and call the
489 callback with the fdatasync result code.
490
491 If this call isn't available because your OS lacks it or it couldn't
492 be detected, it will be emulated by calling "fsync" instead.
493
494 aio_group $callback->(...)
495 This is a very special aio request: Instead of doing something, it
496 is a container for other aio requests, which is useful if you want
497 to bundle many requests into a single, composite, request with a
498 definite callback and the ability to cancel the whole request with
499 its subrequests.
500
501 Returns an object of class IO::AIO::GRP. See its documentation below
502 for more info.
503
504 Example:
505
506 my $grp = aio_group sub {
507 print "all stats done\n";
508 };
509
510 add $grp
511 (aio_stat ...),
512 (aio_stat ...),
513 ...;
514
515 aio_nop $callback->()
516 This is a special request - it does nothing in itself and is only
517 used for side effects, such as when you want to add a dummy request
518 to a group so that finishing the requests in the group depends on
519 executing the given code.
520
521 While this request does nothing, it still goes through the execution
522 phase and still requires a worker thread. Thus, the callback will
523 not be executed immediately but only after other requests in the
524 queue have entered their execution phase. This can be used to
525 measure request latency.
526
527 IO::AIO::aio_busy $fractional_seconds, $callback->() *NOT EXPORTED*
528 Mainly used for debugging and benchmarking, this aio request puts
529 one of the request workers to sleep for the given time.
530
531 While it is theoretically handy to have simple I/O scheduling
532 requests like sleep and file handle readable/writable, the overhead
533 this creates is immense (it blocks a thread for a long time) so do
534 not use this function except to put your application under
535 artificial I/O pressure.
536
537 IO::AIO::REQ CLASS
538 All non-aggregate "aio_*" functions return an object of this class when
539 called in non-void context.
540
541 cancel $req
542 Cancels the request, if possible. Has the effect of skipping
543 execution when entering the execute state and skipping calling the
544 callback when entering the the result state, but will leave the
545 request otherwise untouched. That means that requests that currently
546 execute will not be stopped and resources held by the request will
547 not be freed prematurely.
548
549 cb $req $callback->(...)
550 Replace (or simply set) the callback registered to the request.
551
552 IO::AIO::GRP CLASS
553 This class is a subclass of IO::AIO::REQ, so all its methods apply to
554 objects of this class, too.
555
556 A IO::AIO::GRP object is a special request that can contain multiple
557 other aio requests.
558
559 You create one by calling the "aio_group" constructing function with a
560 callback that will be called when all contained requests have entered
561 the "done" state:
562
563 my $grp = aio_group sub {
564 print "all requests are done\n";
565 };
566
567 You add requests by calling the "add" method with one or more
568 "IO::AIO::REQ" objects:
569
570 $grp->add (aio_unlink "...");
571
572 add $grp aio_stat "...", sub {
573 $_[0] or return $grp->result ("error");
574
575 # add another request dynamically, if first succeeded
576 add $grp aio_open "...", sub {
577 $grp->result ("ok");
578 };
579 };
580
573 This makes it very easy to create composite requests (see the source 581 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 582 "aio_move" for an application) that work and feel like simple requests.
575 requests.
576 583
577 * The IO::AIO::GRP objects will be cleaned up during calls to 584 * The IO::AIO::GRP objects will be cleaned up during calls to
578 "IO::AIO::poll_cb", just like any other request. 585 "IO::AIO::poll_cb", just like any other request.
579 * They can be canceled like any other request. Canceling will cancel 586 * They can be canceled like any other request. Canceling will cancel not
580 not only the request itself, but also all requests it contains. 587 only the request itself, but also all requests it contains.
581 * They can also can also be added to other IO::AIO::GRP objects. 588 * 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 589 * You must not add requests to a group from within the group callback
583 callback (or any later time). 590 (or any later time).
584 591
585 Their lifetime, simplified, looks like this: when they are empty, 592 Their lifetime, simplified, looks like this: when they are empty, they
586 they will finish very quickly. If they contain only requests that 593 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 594 "done" state, they will also finish. Otherwise they will continue to
588 continue to exist. 595 exist.
589 596
590 That means after creating a group you have some time to add 597 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 598 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 599 the group. And only when all those requests have finished will the the
593 finished will the the group itself finish. 600 group itself finish.
594 601
595 add $grp ... 602 add $grp ...
596 $grp->add (...) 603 $grp->add (...)
597 Add one or more requests to the group. Any type of IO::AIO::REQ 604 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 605 be added, including other groups, as long as you do not create
599 create circular dependencies. 606 circular dependencies.
600 607
601 Returns all its arguments. 608 Returns all its arguments.
602 609
603 $grp->cancel_subs 610 $grp->cancel_subs
604 Cancel all subrequests and clears any feeder, but not the group 611 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 612 request itself. Useful when you queued a lot of events but got a
606 result early. 613 result early.
607 614
608 $grp->result (...) 615 $grp->result (...)
609 Set the result value(s) that will be passed to the group 616 Set the result value(s) that will be passed to the group callback
610 callback when all subrequests have finished and set thre groups 617 when all subrequests have finished and set thre groups errno to the
611 errno to the current value of errno (just like calling "errno" 618 current value of errno (just like calling "errno" without an error
612 without an error number). By default, no argument will be passed 619 number). By default, no argument will be passed and errno is zero.
613 and errno is zero.
614 620
615 $grp->errno ([$errno]) 621 $grp->errno ([$errno])
616 Sets the group errno value to $errno, or the current value of 622 Sets the group errno value to $errno, or the current value of errno
617 errno when the argument is missing. 623 when the argument is missing.
618 624
619 Every aio request has an associated errno value that is restored 625 Every aio request has an associated errno value that is restored
620 when the callback is invoked. This method lets you change this 626 when the callback is invoked. This method lets you change this value
621 value from its default (0). 627 from its default (0).
622 628
623 Calling "result" will also set errno, so make sure you either 629 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. 630 before the call to "result", or call c<errno> after it.
625 631
626 feed $grp $callback->($grp) 632 feed $grp $callback->($grp)
627 Sets a feeder/generator on this group: every group can have an 633 Sets a feeder/generator on this group: every group can have an
628 attached generator that generates requests if idle. The idea 634 attached generator that generates requests if idle. The idea behind
629 behind this is that, although you could just queue as many 635 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 636 want in a group, this might starve other requests for a potentially
631 requests for a potentially long time. For example, "aio_scandir" 637 long time. For example, "aio_scandir" might generate hundreds of
632 might generate hundreds of thousands "aio_stat" requests, 638 thousands "aio_stat" requests, delaying any later requests for a
633 delaying any later requests for a long time. 639 long time.
634 640
635 To avoid this, and allow incremental generation of requests, you 641 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 642 instead a group and set a feeder on it that generates those
637 requests. The feed callback will be called whenever there are 643 requests. The feed callback will be called whenever there are few
638 few enough (see "limit", below) requests active in the group 644 enough (see "limit", below) requests active in the group itself and
639 itself and is expected to queue more requests. 645 is expected to queue more requests.
640 646
641 The feed callback can queue as many requests as it likes (i.e. 647 The feed callback can queue as many requests as it likes (i.e. "add"
642 "add" does not impose any limits). 648 does not impose any limits).
643 649
644 If the feed does not queue more requests when called, it will be 650 If the feed does not queue more requests when called, it will be
645 automatically removed from the group. 651 automatically removed from the group.
646 652
647 If the feed limit is 0, it will be set to 2 automatically. 653 If the feed limit is 0, it will be set to 2 automatically.
648 654
649 Example: 655 Example:
650 656
651 # stat all files in @files, but only ever use four aio requests concurrently: 657 # stat all files in @files, but only ever use four aio requests concurrently:
652 658
653 my $grp = aio_group sub { print "finished\n" }; 659 my $grp = aio_group sub { print "finished\n" };
654 limit $grp 4; 660 limit $grp 4;
655 feed $grp sub { 661 feed $grp sub {
656 my $file = pop @files 662 my $file = pop @files
657 or return; 663 or return;
658 664
659 add $grp aio_stat $file, sub { ... }; 665 add $grp aio_stat $file, sub { ... };
660 }; 666 };
661 667
662 limit $grp $num 668 limit $grp $num
663 Sets the feeder limit for the group: The feeder will be called 669 Sets the feeder limit for the group: The feeder will be called
664 whenever the group contains less than this many requests. 670 whenever the group contains less than this many requests.
665 671
666 Setting the limit to 0 will pause the feeding process. 672 Setting the limit to 0 will pause the feeding process.
667 673
668 SUPPORT FUNCTIONS 674 SUPPORT FUNCTIONS
669 EVENT PROCESSING AND EVENT LOOP INTEGRATION 675 EVENT PROCESSING AND EVENT LOOP INTEGRATION
670 $fileno = IO::AIO::poll_fileno 676 $fileno = IO::AIO::poll_fileno
671 Return the *request result pipe file descriptor*. This 677 Return the *request result pipe file descriptor*. This filehandle
672 filehandle must be polled for reading by some mechanism outside 678 must be polled for reading by some mechanism outside this module
673 this module (e.g. Event or select, see below or the SYNOPSIS). 679 (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 680 becomes readable you have to call "poll_cb" to check the results.
675 the results.
676 681
677 See "poll_cb" for an example. 682 See "poll_cb" for an example.
678 683
679 IO::AIO::poll_cb 684 IO::AIO::poll_cb
680 Process some outstanding events on the result pipe. You have to 685 Process some outstanding events on the result pipe. You have to call
681 call this regularly. Returns the number of events processed. 686 this regularly. Returns the number of events processed. Returns
682 Returns immediately when no events are outstanding. The amount 687 immediately when no events are outstanding. The amount of events
683 of events processed depends on the settings of 688 processed depends on the settings of "IO::AIO::max_poll_req" and
684 "IO::AIO::max_poll_req" and "IO::AIO::max_poll_time". 689 "IO::AIO::max_poll_time".
685 690
686 If not all requests were processed for whatever reason, the 691 If not all requests were processed for whatever reason, the
687 filehandle will still be ready when "poll_cb" returns. 692 filehandle will still be ready when "poll_cb" returns.
688 693
689 Example: Install an Event watcher that automatically calls 694 Example: Install an Event watcher that automatically calls
690 IO::AIO::poll_cb with high priority: 695 IO::AIO::poll_cb with high priority:
691 696
692 Event->io (fd => IO::AIO::poll_fileno, 697 Event->io (fd => IO::AIO::poll_fileno,
693 poll => 'r', async => 1, 698 poll => 'r', async => 1,
694 cb => \&IO::AIO::poll_cb); 699 cb => \&IO::AIO::poll_cb);
695 700
696 IO::AIO::max_poll_reqs $nreqs 701 IO::AIO::max_poll_reqs $nreqs
697 IO::AIO::max_poll_time $seconds 702 IO::AIO::max_poll_time $seconds
698 These set the maximum number of requests (default 0, meaning 703 These set the maximum number of requests (default 0, meaning
699 infinity) that are being processed by "IO::AIO::poll_cb" in one 704 infinity) that are being processed by "IO::AIO::poll_cb" in one
700 call, respectively the maximum amount of time (default 0, 705 call, respectively the maximum amount of time (default 0, meaning
701 meaning infinity) spent in "IO::AIO::poll_cb" to process 706 infinity) spent in "IO::AIO::poll_cb" to process requests (more
702 requests (more correctly the mininum amount of time "poll_cb" is 707 correctly the mininum amount of time "poll_cb" is allowed to use).
703 allowed to use).
704 708
709 Setting "max_poll_time" to a non-zero value creates an overhead of
710 one syscall per request processed, which is not normally a problem
711 unless your callbacks are really really fast or your OS is really
712 really slow (I am not mentioning Solaris here). Using
713 "max_poll_reqs" incurs no overhead.
714
705 Setting these is useful if you want to ensure some level of 715 Setting these is useful if you want to ensure some level of
706 interactiveness when perl is not fast enough to process all 716 interactiveness when perl is not fast enough to process all requests
707 requests in time. 717 in time.
708 718
709 For interactive programs, values such as 0.01 to 0.1 should be 719 For interactive programs, values such as 0.01 to 0.1 should be fine.
710 fine.
711 720
712 Example: Install an Event watcher that automatically calls 721 Example: Install an Event watcher that automatically calls
713 IO::AIO::poll_some with low priority, to ensure that other parts 722 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. 723 the program get the CPU sometimes even under high AIO load.
715 724
716 # try not to spend much more than 0.1s in poll_cb 725 # try not to spend much more than 0.1s in poll_cb
717 IO::AIO::max_poll_time 0.1; 726 IO::AIO::max_poll_time 0.1;
718 727
719 # use a low priority so other tasks have priority 728 # use a low priority so other tasks have priority
720 Event->io (fd => IO::AIO::poll_fileno, 729 Event->io (fd => IO::AIO::poll_fileno,
721 poll => 'r', nice => 1, 730 poll => 'r', nice => 1,
722 cb => &IO::AIO::poll_cb); 731 cb => &IO::AIO::poll_cb);
723 732
724 IO::AIO::poll_wait 733 IO::AIO::poll_wait
734 If there are any outstanding requests and none of them in the result
725 Wait till the result filehandle becomes ready for reading 735 phase, wait till the result filehandle becomes ready for reading
726 (simply does a "select" on the filehandle. This is useful if you 736 (simply does a "select" on the filehandle. This is useful if you
727 want to synchronously wait for some requests to finish). 737 want to synchronously wait for some requests to finish).
728 738
729 See "nreqs" for an example. 739 See "nreqs" for an example.
730 740
731 IO::AIO::poll 741 IO::AIO::poll
732 Waits until some requests have been handled. 742 Waits until some requests have been handled.
733 743
744 Returns the number of requests processed, but is otherwise strictly
734 Strictly equivalent to: 745 equivalent to:
735 746
736 IO::AIO::poll_wait, IO::AIO::poll_cb 747 IO::AIO::poll_wait, IO::AIO::poll_cb
737 if IO::AIO::nreqs;
738 748
739 IO::AIO::flush 749 IO::AIO::flush
740 Wait till all outstanding AIO requests have been handled. 750 Wait till all outstanding AIO requests have been handled.
741 751
742 Strictly equivalent to: 752 Strictly equivalent to:
743 753
744 IO::AIO::poll_wait, IO::AIO::poll_cb 754 IO::AIO::poll_wait, IO::AIO::poll_cb
745 while IO::AIO::nreqs; 755 while IO::AIO::nreqs;
746 756
747 CONTROLLING THE NUMBER OF THREADS 757 CONTROLLING THE NUMBER OF THREADS
748 IO::AIO::min_parallel $nthreads 758 IO::AIO::min_parallel $nthreads
749 Set the minimum number of AIO threads to $nthreads. The current 759 Set the minimum number of AIO threads to $nthreads. The current
750 default is 8, which means eight asynchronous operations can 760 default is 8, which means eight asynchronous operations can execute
751 execute concurrently at any one time (the number of outstanding 761 concurrently at any one time (the number of outstanding requests,
752 requests, however, is unlimited). 762 however, is unlimited).
753 763
754 IO::AIO starts threads only on demand, when an AIO request is 764 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 765 and no free thread exists. Please note that queueing up a hundred
756 hundred requests can create demand for a hundred threads, even 766 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 767 out that everything is in the cache and could have been processed
758 been processed faster by a single thread. 768 faster by a single thread.
759 769
760 It is recommended to keep the number of threads relatively low, 770 It is recommended to keep the number of threads relatively low, as
761 as some Linux kernel versions will scale negatively with the 771 some Linux kernel versions will scale negatively with the number of
762 number of threads (higher parallelity => MUCH higher latency). 772 threads (higher parallelity => MUCH higher latency). With current
763 With current Linux 2.6 versions, 4-32 threads should be fine. 773 Linux 2.6 versions, 4-32 threads should be fine.
764 774
765 Under most circumstances you don't need to call this function, 775 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 776 the module selects a default that is suitable for low to moderate
767 moderate load. 777 load.
768 778
769 IO::AIO::max_parallel $nthreads 779 IO::AIO::max_parallel $nthreads
770 Sets the maximum number of AIO threads to $nthreads. If more 780 Sets the maximum number of AIO threads to $nthreads. If more than
771 than the specified number of threads are currently running, this 781 the specified number of threads are currently running, this function
772 function kills them. This function blocks until the limit is 782 kills them. This function blocks until the limit is reached.
773 reached.
774 783
775 While $nthreads are zero, aio requests get queued but not 784 While $nthreads are zero, aio requests get queued but not executed
776 executed until the number of threads has been increased again. 785 until the number of threads has been increased again.
777 786
778 This module automatically runs "max_parallel 0" at program end, 787 This module automatically runs "max_parallel 0" at program end, to
779 to ensure that all threads are killed and that there are no 788 ensure that all threads are killed and that there are no outstanding
780 outstanding requests. 789 requests.
781 790
782 Under normal circumstances you don't need to call this function. 791 Under normal circumstances you don't need to call this function.
783 792
784 IO::AIO::max_idle $nthreads 793 IO::AIO::max_idle $nthreads
785 Limit the number of threads (default: 4) that are allowed to 794 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 795 (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 796 seconds). That means if a thread becomes idle while $nthreads other
788 other threads are also idle, it will free its resources and 797 threads are also idle, it will free its resources and exit.
789 exit.
790 798
791 This is useful when you allow a large number of threads (e.g. 799 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 800 1000) to allow for extremely high load situations, but want to free
793 want to free resources under normal circumstances (1000 threads 801 resources under normal circumstances (1000 threads can easily
794 can easily consume 30MB of RAM). 802 consume 30MB of RAM).
795 803
796 The default is probably ok in most situations, especially if 804 The default is probably ok in most situations, especially if thread
797 thread creation is fast. If thread creation is very slow on your 805 creation is fast. If thread creation is very slow on your system you
798 system you might want to use larger values. 806 might want to use larger values.
799 807
800 $oldmaxreqs = IO::AIO::max_outstanding $maxreqs 808 $oldmaxreqs = IO::AIO::max_outstanding $maxreqs
801 This is a very bad function to use in interactive programs 809 This is a very bad function to use in interactive programs because
802 because it blocks, and a bad way to reduce concurrency because 810 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 811 inexact: Better use an "aio_group" together with a feed callback.
804 callback.
805 812
806 Sets the maximum number of outstanding requests to $nreqs. If 813 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 814 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 815 "poll_cb" (and "poll_some" and other functions calling "poll_cb")
809 "poll_cb") function will block until the limit is no longer 816 function will block until the limit is no longer exceeded.
810 exceeded.
811 817
812 The default value is very large, so there is no practical limit 818 The default value is very large, so there is no practical limit on
813 on the number of outstanding requests. 819 the number of outstanding requests.
814 820
815 You can still queue as many requests as you want. Therefore, 821 You can still queue as many requests as you want. Therefore,
816 "max_oustsanding" is mainly useful in simple scripts (with low 822 "max_oustsanding" is mainly useful in simple scripts (with low
817 values) or as a stop gap to shield against fatal memory overflow 823 values) or as a stop gap to shield against fatal memory overflow
818 (with large values). 824 (with large values).
819 825
820 STATISTICAL INFORMATION 826 STATISTICAL INFORMATION
821 IO::AIO::nreqs 827 IO::AIO::nreqs
822 Returns the number of requests currently in the ready, execute 828 Returns the number of requests currently in the ready, execute or
823 or pending states (i.e. for which their callback has not been 829 pending states (i.e. for which their callback has not been invoked
824 invoked yet). 830 yet).
825 831
826 Example: wait till there are no outstanding requests anymore: 832 Example: wait till there are no outstanding requests anymore:
827 833
828 IO::AIO::poll_wait, IO::AIO::poll_cb 834 IO::AIO::poll_wait, IO::AIO::poll_cb
829 while IO::AIO::nreqs; 835 while IO::AIO::nreqs;
830 836
831 IO::AIO::nready 837 IO::AIO::nready
832 Returns the number of requests currently in the ready state (not 838 Returns the number of requests currently in the ready state (not yet
833 yet executed). 839 executed).
834 840
835 IO::AIO::npending 841 IO::AIO::npending
836 Returns the number of requests currently in the pending state 842 Returns the number of requests currently in the pending state
837 (executed, but not yet processed by poll_cb). 843 (executed, but not yet processed by poll_cb).
838 844
839 FORK BEHAVIOUR 845 FORK BEHAVIOUR
840 This module should do "the right thing" when the process using it 846 This module should do "the right thing" when the process using it forks:
841 forks:
842 847
843 Before the fork, IO::AIO enters a quiescent state where no requests 848 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. 849 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 850 fork the parent simply leaves the quiescent state and continues
846 continues request/result processing, while the child frees the 851 request/result processing, while the child frees the request/result
847 request/result queue (so that the requests started before the fork 852 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 853 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 854 the parent process has been reached again.
850 again.
851 855
852 In short: the parent will, after a short pause, continue as if fork 856 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 857 not been called, while the child will act as if IO::AIO has not been
854 been used yet. 858 used yet.
855 859
856 MEMORY USAGE 860 MEMORY USAGE
857 Per-request usage: 861 Per-request usage:
858 862
859 Each aio request uses - depending on your architecture - around 863 Each aio request uses - depending on your architecture - around 100-200
860 100-200 bytes of memory. In addition, stat requests need a stat 864 bytes of memory. In addition, stat requests need a stat buffer (possibly
861 buffer (possibly a few hundred bytes), readdir requires a result 865 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 866 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 867 will consume memory till the request has entered the done state.
864 request has entered the done state.
865 868
866 This is now awfully much, so queuing lots of requests is not usually 869 This is now awfully much, so queuing lots of requests is not usually a
867 a problem. 870 problem.
868 871
869 Per-thread usage: 872 Per-thread usage:
870 873
871 In the execution phase, some aio requests require more memory for 874 In the execution phase, some aio requests require more memory for
872 temporary buffers, and each thread requires a stack and other data 875 temporary buffers, and each thread requires a stack and other data
873 structures (usually around 16k-128k, depending on the OS). 876 structures (usually around 16k-128k, depending on the OS).
874 877
875KNOWN BUGS 878KNOWN BUGS
876 Known bugs will be fixed in the next release. 879 Known bugs will be fixed in the next release.
877 880
878SEE ALSO 881SEE ALSO
879 Coro::AIO. 882 Coro::AIO.
880 883
881AUTHOR 884AUTHOR
882 Marc Lehmann <schmorp@schmorp.de> 885 Marc Lehmann <schmorp@schmorp.de>
883 http://home.schmorp.de/ 886 http://home.schmorp.de/
884 887

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