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Revision 1.30 by root, Wed Aug 17 04:47:38 2005 UTC vs.
Revision 1.38 by root, Sun Aug 28 10:51:33 2005 UTC

… …
63use base 'Exporter'; 63use base 'Exporter';
64 64
65use Fcntl (); 65use Fcntl ();
66 66
67BEGIN { 67BEGIN {
68 $VERSION = 1.2; 68 $VERSION = 1.6;
69 69
70 @EXPORT = qw(aio_read aio_write aio_open aio_close aio_stat aio_lstat aio_unlink 70 @EXPORT = qw(aio_sendfile aio_read aio_write aio_open aio_close stat
71 aio_aio_lstat aio_unlink aio_rmdir aio_readdir aio_symlink
71 aio_rmdir aio_symlink aio_fsync aio_fdatasync aio_readahead); 72 aio_fsync aio_fdatasync aio_readahead);
72 @EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs); 73 @EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel
74 max_outstanding nreqs);
73 75
74 require XSLoader; 76 require XSLoader;
75 XSLoader::load IO::AIO, $VERSION; 77 XSLoader::load IO::AIO, $VERSION;
76} 78}
77 79
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150Reads or writes C<length> bytes from the specified C<fh> and C<offset> 152Reads or writes C<length> bytes from the specified C<fh> and C<offset>
151into the scalar given by C<data> and offset C<dataoffset> and calls the 153into the scalar given by C<data> and offset C<dataoffset> and calls the
152callback without the actual number of bytes read (or -1 on error, just 154callback without the actual number of bytes read (or -1 on error, just
153like the syscall). 155like the syscall).
154 156
157The C<$data> scalar I<MUST NOT> be modified in any way while the request
158is outstanding. Modifying it can result in segfaults or WW3 (if the
159necessary/optional hardware is installed).
160
155Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at 161Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at
156offset C<0> within the scalar: 162offset C<0> within the scalar:
157 163
158 aio_read $fh, 7, 15, $buffer, 0, sub { 164 aio_read $fh, 7, 15, $buffer, 0, sub {
159 $_[0] > 0 or die "read error: $!"; 165 $_[0] > 0 or die "read error: $!";
160 print "read $_[0] bytes: <$buffer>\n"; 166 print "read $_[0] bytes: <$buffer>\n";
161 }; 167 };
168
169=item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback
170
171Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
172reading at byte offset C<$in_offset>, and starts writing at the current
173file offset of C<$out_fh>. Because of that, it is not safe to issue more
174than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
175other.
176
177This call tries to make use of a native C<sendfile> syscall to provide
178zero-copy operation. For this to work, C<$out_fh> should refer to a
179socket, and C<$in_fh> should refer to mmap'able file.
180
181If the native sendfile call fails or is not implemented, it will be
182emulated, so you can call C<aio_sendfile> on any type of filehandle
183regardless of the limitations of the operating system.
184
185Please note, however, that C<aio_sendfile> can read more bytes from
186C<$in_fh> than are written, and there is no way to find out how many
187bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only
188provides the number of bytes written to C<$out_fh>. Only if the result
189value equals C<$length> one can assume that C<$length> bytes have been
190read.
162 191
163=item aio_readahead $fh,$offset,$length, $callback 192=item aio_readahead $fh,$offset,$length, $callback
164 193
165C<aio_readahead> populates the page cache with data from a file so that 194C<aio_readahead> populates the page cache with data from a file so that
166subsequent reads from that file will not block on disk I/O. The C<$offset> 195subsequent reads from that file will not block on disk I/O. The C<$offset>
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204=item aio_rmdir $pathname, $callback 233=item aio_rmdir $pathname, $callback
205 234
206Asynchronously rmdir (delete) a directory and call the callback with the 235Asynchronously rmdir (delete) a directory and call the callback with the
207result code. 236result code.
208 237
238=item aio_readdir $pathname $callback
239
240Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
241directory (i.e. opendir + readdir + closedir). The entries will not be
242sorted, and will B<NOT> include the C<.> and C<..> entries.
243
244The callback a single argument which is either C<undef> or an array-ref
245with the filenames.
246
209=item aio_fsync $fh, $callback 247=item aio_fsync $fh, $callback
210 248
211Asynchronously call fsync on the given filehandle and call the callback 249Asynchronously call fsync on the given filehandle and call the callback
212with the fsync result code. 250with the fsync result code.
213 251
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283 IO::AIO::poll_wait, IO::AIO::poll_cb 321 IO::AIO::poll_wait, IO::AIO::poll_cb
284 if IO::AIO::nreqs; 322 if IO::AIO::nreqs;
285 323
286=item IO::AIO::min_parallel $nthreads 324=item IO::AIO::min_parallel $nthreads
287 325
288Set the minimum number of AIO threads to C<$nthreads>. The default is 326Set 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 327is C<4>, which means four asynchronous operations can be done at one time
290(the number of outstanding operations, however, is unlimited). 328(the number of outstanding operations, however, is unlimited).
329
330IO::AIO starts threads only on demand, when an AIO request is queued and
331no free thread exists.
291 332
292It is recommended to keep the number of threads low, as some Linux 333It is recommended to keep the number of threads low, as some Linux
293kernel versions will scale negatively with the number of threads (higher 334kernel versions will scale negatively with the number of threads (higher
294parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32 335parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32
295threads should be fine. 336threads should be fine.
296 337
297Under normal circumstances you don't need to call this function, as this 338Under most circumstances you don't need to call this function, as the
298module automatically starts some threads (the exact number might change, 339module selects a default that is suitable for low to moderate load.
299and is currently 4).
300 340
301=item IO::AIO::max_parallel $nthreads 341=item IO::AIO::max_parallel $nthreads
302 342
303Sets the maximum number of AIO threads to C<$nthreads>. If more than 343Sets the maximum number of AIO threads to C<$nthreads>. If more than the
304the specified number of threads are currently running, kill them. This 344specified number of threads are currently running, this function kills
305function blocks until the limit is reached. 345them. This function blocks until the limit is reached.
346
347While C<$nthreads> are zero, aio requests get queued but not executed
348until the number of threads has been increased again.
306 349
307This module automatically runs C<max_parallel 0> at program end, to ensure 350This module automatically runs C<max_parallel 0> at program end, to ensure
308that all threads are killed and that there are no outstanding requests. 351that all threads are killed and that there are no outstanding requests.
309 352
310Under normal circumstances you don't need to call this function. 353Under normal circumstances you don't need to call this function.
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314Sets the maximum number of outstanding requests to C<$nreqs>. If you 357Sets the maximum number of outstanding requests to C<$nreqs>. If you
315try to queue up more than this number of requests, the caller will block until 358try to queue up more than this number of requests, the caller will block until
316some requests have been handled. 359some requests have been handled.
317 360
318The default is very large, so normally there is no practical limit. If you 361The 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 362queue up many requests in a loop it often improves speed if you set
320this to a relatively low number, such as C<100>. 363this to a relatively low number, such as C<100>.
321 364
322Under normal circumstances you don't need to call this function. 365Under normal circumstances you don't need to call this function.
323 366
324=back 367=back
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349 392
3501; 3931;
351 394
352=head2 FORK BEHAVIOUR 395=head2 FORK BEHAVIOUR
353 396
354Before the fork IO::AIO first handles all outstanding requests - if other 397Before the fork, IO::AIO enters a quiescent state where no requests
355threads add requests during this period, this time is prolonged. It then 398can 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 399the fork the parent simply leaves the quiescent state and continues
357and no results will be processed. After the fork the parent simply leaves 400request/result processing, while the child clears the request/result
358the quiescent state and continues request processing, while the child 401queue (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. 402the parent). Threats will be started on demand until the limit ste in the
403parent process has been reached again.
360 404
361=head1 SEE ALSO 405=head1 SEE ALSO
362 406
363L<Coro>, L<Linux::AIO>. 407L<Coro>, L<Linux::AIO>.
364 408

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