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Revision 1.30 by root, Wed Aug 17 04:47:38 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 = 1.2; 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: $!";
160 print "read $_[0] bytes: <$buffer>\n"; 164 print "read $_[0] bytes: <$buffer>\n";
161 }; 165 };
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.
162 189
163=item aio_readahead $fh,$offset,$length, $callback 190=item aio_readahead $fh,$offset,$length, $callback
164 191
165C<aio_readahead> populates the page cache with data from a file so that 192C<aio_readahead> populates the page cache with data from a file so that
166subsequent reads from that file will not block on disk I/O. The C<$offset> 193subsequent reads from that file will not block on disk I/O. The C<$offset>
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283 IO::AIO::poll_wait, IO::AIO::poll_cb 310 IO::AIO::poll_wait, IO::AIO::poll_cb
284 if IO::AIO::nreqs; 311 if IO::AIO::nreqs;
285 312
286=item IO::AIO::min_parallel $nthreads 313=item IO::AIO::min_parallel $nthreads
287 314
288Set the minimum number of AIO threads to C<$nthreads>. The default is 315Set the minimum number of AIO threads to C<$nthreads>. The current default
289C<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
290(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.
291 321
292It 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
293kernel versions will scale negatively with the number of threads (higher 323kernel versions will scale negatively with the number of threads (higher
294parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32 324parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32
295threads should be fine. 325threads should be fine.
296 326
297Under 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
298module automatically starts some threads (the exact number might change, 328module selects a default that is suitable for low to moderate load.
299and is currently 4).
300 329
301=item IO::AIO::max_parallel $nthreads 330=item IO::AIO::max_parallel $nthreads
302 331
303Sets the maximum number of AIO threads to C<$nthreads>. If more than 332Sets the maximum number of AIO threads to C<$nthreads>. If more than the
304the specified number of threads are currently running, kill them. This 333specified number of threads are currently running, this function kills
305function blocks until the limit is reached. 334them. This function blocks until the limit is reached.
335
336While C<$nthreads> are zero, aio requests get queued but not executed
337until the number of threads has been increased again.
306 338
307This 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
308that all threads are killed and that there are no outstanding requests. 340that all threads are killed and that there are no outstanding requests.
309 341
310Under 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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314Sets the maximum number of outstanding requests to C<$nreqs>. If you 346Sets the maximum number of outstanding requests to C<$nreqs>. If you
315try to queue up more than this number of requests, the caller will block until 347try to queue up more than this number of requests, the caller will block until
316some requests have been handled. 348some requests have been handled.
317 349
318The 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
319queue 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
320this to a relatively low number, such as C<100>. 352this to a relatively low number, such as C<100>.
321 353
322Under normal circumstances you don't need to call this function. 354Under normal circumstances you don't need to call this function.
323 355
324=back 356=back
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349 381
3501; 3821;
351 383
352=head2 FORK BEHAVIOUR 384=head2 FORK BEHAVIOUR
353 385
354Before the fork IO::AIO first handles all outstanding requests - if other 386Before the fork, IO::AIO enters a quiescent state where no requests
355threads add requests during this period, this time is prolonged. It then 387can 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 388the fork the parent simply leaves the quiescent state and continues
357and no results will be processed. After the fork the parent simply leaves 389request/result processing, while the child clears the request/result
358the quiescent state and continues request processing, while the child 390queue (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. 391the parent). Threats will be started on demand until the limit ste in the
392parent process has been reached again.
360 393
361=head1 SEE ALSO 394=head1 SEE ALSO
362 395
363L<Coro>, L<Linux::AIO>. 396L<Coro>, L<Linux::AIO>.
364 397

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