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Comparing IO-AIO/AIO.pm (file contents):
Revision 1.32 by root, Wed Aug 17 05:26:20 2005 UTC vs.
Revision 1.35 by root, Mon Aug 22 23:20:37 2005 UTC

… …
63use base 'Exporter'; 63use base 'Exporter';
64 64
65use Fcntl (); 65use Fcntl ();
66 66
67BEGIN { 67BEGIN {
68 $VERSION = 1.3; 68 $VERSION = 1.5;
69
70 69
71 @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
72 aio_rmdir aio_symlink aio_fsync aio_fdatasync aio_readahead); 71 aio_rmdir aio_symlink aio_fsync aio_fdatasync aio_readahead);
73 @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);
74 73
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163 aio_read $fh, 7, 15, $buffer, 0, sub { 162 aio_read $fh, 7, 15, $buffer, 0, sub {
164 $_[0] > 0 or die "read error: $!"; 163 $_[0] > 0 or die "read error: $!";
165 print "read $_[0] bytes: <$buffer>\n"; 164 print "read $_[0] bytes: <$buffer>\n";
166 }; 165 };
167 166
167=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback
168
169Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
170reading at byte offset C<$in_offset>, and starts writing at the current
171file offset of C<$out_fh>. Because of that, it is not safe to issue more
172than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
173other.
174
175This call tries to make use of a native C<sendfile> syscall to provide
176zero-copy operation. For this to work, C<$out_fh> should refer to a
177socket, and C<$in_fh> should refer to mmap'able file.
178
179If the native sendfile call fails or is not implemented, it will be
180emulated, so you can call C<aio_sendfile> on any filehandles regardless of
181the limitations of the OS.
182
183Please note, however, that C<aio_sendfile> can read more bytes from
184C<$in_fh> than are written, and there is no way to find out how many
185bytes have been read form C<aio_sendfile> alone, as C<aio_sendfile> only
186provides the number of bytes written to C<$out_fh>. Only if the return
187value (the value provided to the callback) equals C<$length> one can
188assume that C<$length> bytes have been read.
189
168=item aio_readahead $fh,$offset,$length, $callback 190=item aio_readahead $fh,$offset,$length, $callback
169 191
170C<aio_readahead> populates the page cache with data from a file so that 192C<aio_readahead> populates the page cache with data from a file so that
171subsequent reads from that file will not block on disk I/O. The C<$offset> 193subsequent reads from that file will not block on disk I/O. The C<$offset>
172argument specifies the starting point from which data is to be read and 194argument specifies the starting point from which data is to be read and
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288 IO::AIO::poll_wait, IO::AIO::poll_cb 310 IO::AIO::poll_wait, IO::AIO::poll_cb
289 if IO::AIO::nreqs; 311 if IO::AIO::nreqs;
290 312
291=item IO::AIO::min_parallel $nthreads 313=item IO::AIO::min_parallel $nthreads
292 314
293Set the minimum number of AIO threads to C<$nthreads>. The default is 315Set the minimum number of AIO threads to C<$nthreads>. The current default
294C<1>, which means a single asynchronous operation can be done at one time 316is C<4>, which means four asynchronous operations can be done at one time
295(the number of outstanding operations, however, is unlimited). 317(the number of outstanding operations, however, is unlimited).
318
319IO::AIO starts threads only on demand, when an AIO request is queued and
320no free thread exists.
296 321
297It is recommended to keep the number of threads low, as some Linux 322It is recommended to keep the number of threads low, as some Linux
298kernel versions will scale negatively with the number of threads (higher 323kernel versions will scale negatively with the number of threads (higher
299parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32 324parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32
300threads should be fine. 325threads should be fine.
301 326
302Under normal circumstances you don't need to call this function, as this 327Under most circumstances you don't need to call this function, as the
303module automatically starts some threads (the exact number might change, 328module selects a default that is suitable for low to moderate load.
304and is currently 4).
305 329
306=item IO::AIO::max_parallel $nthreads 330=item IO::AIO::max_parallel $nthreads
307 331
308Sets the maximum number of AIO threads to C<$nthreads>. If more than 332Sets the maximum number of AIO threads to C<$nthreads>. If more than the
309the specified number of threads are currently running, kill them. This 333specified number of threads are currently running, this function kills
310function blocks until the limit is reached. 334them. This function blocks until the limit is reached.
335
336While C<$nthreads> are zero, aio requests get queued but not executed
337until the number of threads has been increased again.
311 338
312This module automatically runs C<max_parallel 0> at program end, to ensure 339This module automatically runs C<max_parallel 0> at program end, to ensure
313that all threads are killed and that there are no outstanding requests. 340that all threads are killed and that there are no outstanding requests.
314 341
315Under normal circumstances you don't need to call this function. 342Under normal circumstances you don't need to call this function.
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319Sets the maximum number of outstanding requests to C<$nreqs>. If you 346Sets the maximum number of outstanding requests to C<$nreqs>. If you
320try to queue up more than this number of requests, the caller will block until 347try to queue up more than this number of requests, the caller will block until
321some requests have been handled. 348some requests have been handled.
322 349
323The default is very large, so normally there is no practical limit. If you 350The default is very large, so normally there is no practical limit. If you
324queue up many requests in a loop it it often improves speed if you set 351queue up many requests in a loop it often improves speed if you set
325this to a relatively low number, such as C<100>. 352this to a relatively low number, such as C<100>.
326 353
327Under normal circumstances you don't need to call this function. 354Under normal circumstances you don't need to call this function.
328 355
329=back 356=back
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354 381
3551; 3821;
356 383
357=head2 FORK BEHAVIOUR 384=head2 FORK BEHAVIOUR
358 385
359Before the fork IO::AIO enters a quiescent state where no requests can be 386Before the fork, IO::AIO enters a quiescent state where no requests
360added in other threads and no results will be processed. After the fork 387can be added in other threads and no results will be processed. After
361the parent simply leaves the quiescent state and continues request/result 388the fork the parent simply leaves the quiescent state and continues
362processing, while the child clears the request/result queue and starts the 389request/result processing, while the child clears the request/result
363same number of threads as were in use by the parent. 390queue (so the requests started before the fork will only be handled in
391the parent). Threats will be started on demand until the limit ste in the
392parent process has been reached again.
364 393
365=head1 SEE ALSO 394=head1 SEE ALSO
366 395
367L<Coro>, L<Linux::AIO>. 396L<Coro>, L<Linux::AIO>.
368 397

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