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Comparing IO-AIO/AIO.pm (file contents):
Revision 1.30 by root, Wed Aug 17 04:47:38 2005 UTC vs.
Revision 1.34 by root, Thu Aug 18 16:32:10 2005 UTC

… …
63use base 'Exporter'; 63use base 'Exporter';
64 64
65use Fcntl (); 65use Fcntl ();
66 66
67BEGIN { 67BEGIN {
68 $VERSION = 1.2; 68 $VERSION = 1.5;
69 69
70 @EXPORT = qw(aio_read aio_write aio_open aio_close aio_stat aio_lstat aio_unlink 70 @EXPORT = qw(aio_read aio_write aio_open aio_close aio_stat aio_lstat aio_unlink
71 aio_rmdir aio_symlink aio_fsync aio_fdatasync aio_readahead); 71 aio_rmdir aio_symlink aio_fsync aio_fdatasync aio_readahead);
72 @EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs); 72 @EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs);
73 73
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150Reads or writes C<length> bytes from the specified C<fh> and C<offset> 150Reads or writes C<length> bytes from the specified C<fh> and C<offset>
151into the scalar given by C<data> and offset C<dataoffset> and calls the 151into the scalar given by C<data> and offset C<dataoffset> and calls the
152callback without the actual number of bytes read (or -1 on error, just 152callback without the actual number of bytes read (or -1 on error, just
153like the syscall). 153like the syscall).
154 154
155The C<$data> scalar I<MUST NOT> be modified in any way while the request
156is outstanding. Modifying it can result in segfaults or WW3 (if the
157necessary/optional hardware is installed).
158
155Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at 159Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
156offset C<0> within the scalar: 160offset C<0> within the scalar:
157 161
158 aio_read $fh, 7, 15, $buffer, 0, sub { 162 aio_read $fh, 7, 15, $buffer, 0, sub {
159 $_[0] > 0 or die "read error: $!"; 163 $_[0] > 0 or die "read error: $!";
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283 IO::AIO::poll_wait, IO::AIO::poll_cb 287 IO::AIO::poll_wait, IO::AIO::poll_cb
284 if IO::AIO::nreqs; 288 if IO::AIO::nreqs;
285 289
286=item IO::AIO::min_parallel $nthreads 290=item IO::AIO::min_parallel $nthreads
287 291
288Set the minimum number of AIO threads to C<$nthreads>. The default is 292Set the minimum number of AIO threads to C<$nthreads>. The current default
289C<1>, which means a single asynchronous operation can be done at one time 293is C<4>, which means four asynchronous operations can be done at one time
290(the number of outstanding operations, however, is unlimited). 294(the number of outstanding operations, however, is unlimited).
295
296IO::AIO starts threads only on demand, when an AIO request is queued and
297no free thread exists.
291 298
292It is recommended to keep the number of threads low, as some Linux 299It is recommended to keep the number of threads low, as some Linux
293kernel versions will scale negatively with the number of threads (higher 300kernel versions will scale negatively with the number of threads (higher
294parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32 301parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32
295threads should be fine. 302threads should be fine.
296 303
297Under normal circumstances you don't need to call this function, as this 304Under most circumstances you don't need to call this function, as the
298module automatically starts some threads (the exact number might change, 305module selects a default that is suitable for low to moderate load.
299and is currently 4).
300 306
301=item IO::AIO::max_parallel $nthreads 307=item IO::AIO::max_parallel $nthreads
302 308
303Sets the maximum number of AIO threads to C<$nthreads>. If more than 309Sets the maximum number of AIO threads to C<$nthreads>. If more than the
304the specified number of threads are currently running, kill them. This 310specified number of threads are currently running, this function kills
305function blocks until the limit is reached. 311them. This function blocks until the limit is reached.
312
313While C<$nthreads> are zero, aio requests get queued but not executed
314until the number of threads has been increased again.
306 315
307This module automatically runs C<max_parallel 0> at program end, to ensure 316This module automatically runs C<max_parallel 0> at program end, to ensure
308that all threads are killed and that there are no outstanding requests. 317that all threads are killed and that there are no outstanding requests.
309 318
310Under normal circumstances you don't need to call this function. 319Under normal circumstances you don't need to call this function.
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314Sets the maximum number of outstanding requests to C<$nreqs>. If you 323Sets the maximum number of outstanding requests to C<$nreqs>. If you
315try to queue up more than this number of requests, the caller will block until 324try to queue up more than this number of requests, the caller will block until
316some requests have been handled. 325some requests have been handled.
317 326
318The default is very large, so normally there is no practical limit. If you 327The default is very large, so normally there is no practical limit. If you
319queue up many requests in a loop it it often improves speed if you set 328queue up many requests in a loop it often improves speed if you set
320this to a relatively low number, such as C<100>. 329this to a relatively low number, such as C<100>.
321 330
322Under normal circumstances you don't need to call this function. 331Under normal circumstances you don't need to call this function.
323 332
324=back 333=back
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349 358
3501; 3591;
351 360
352=head2 FORK BEHAVIOUR 361=head2 FORK BEHAVIOUR
353 362
354Before the fork IO::AIO first handles all outstanding requests - if other 363Before the fork, IO::AIO enters a quiescent state where no requests
355threads add requests during this period, this time is prolonged. It then 364can be added in other threads and no results will be processed. After
356enters a quiescent state where no requests can be added in other threads 365the fork the parent simply leaves the quiescent state and continues
357and no results will be processed. After the fork the parent simply leaves 366request/result processing, while the child clears the request/result
358the quiescent state and continues request processing, while the child 367queue (so the requests started before the fork will only be handled in
359starts the same number of threads as were in use by the parent. 368the parent). Threats will be started on demand until the limit ste in the
369parent process has been reached again.
360 370
361=head1 SEE ALSO 371=head1 SEE ALSO
362 372
363L<Coro>, L<Linux::AIO>. 373L<Coro>, L<Linux::AIO>.
364 374

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