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63 | use base 'Exporter'; |
63 | use base 'Exporter'; |
64 | |
64 | |
65 | use Fcntl (); |
65 | use Fcntl (); |
66 | |
66 | |
67 | BEGIN { |
67 | BEGIN { |
68 | $VERSION = 1.2; |
68 | $VERSION = 1.5; |
69 | |
69 | |
70 | @EXPORT = qw(aio_read aio_write aio_open aio_close aio_stat aio_lstat aio_unlink |
70 | @EXPORT = qw(aio_read aio_write aio_open aio_close aio_stat aio_lstat aio_unlink |
71 | aio_rmdir aio_symlink aio_fsync aio_fdatasync aio_readahead); |
71 | aio_rmdir aio_symlink aio_fsync aio_fdatasync aio_readahead); |
72 | @EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs); |
72 | @EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel max_outstanding nreqs); |
73 | |
73 | |
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150 | Reads or writes C<length> bytes from the specified C<fh> and C<offset> |
150 | Reads or writes C<length> bytes from the specified C<fh> and C<offset> |
151 | into the scalar given by C<data> and offset C<dataoffset> and calls the |
151 | into the scalar given by C<data> and offset C<dataoffset> and calls the |
152 | callback without the actual number of bytes read (or -1 on error, just |
152 | callback without the actual number of bytes read (or -1 on error, just |
153 | like the syscall). |
153 | like the syscall). |
154 | |
154 | |
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155 | The C<$data> scalar I<MUST NOT> be modified in any way while the request |
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156 | is outstanding. Modifying it can result in segfaults or WW3 (if the |
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157 | necessary/optional hardware is installed). |
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158 | |
155 | Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at |
159 | Example: Read 15 bytes at offset 7 into scalar C<$buffer>, starting at |
156 | offset C<0> within the scalar: |
160 | offset 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 | }; |
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166 | |
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167 | =item aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback |
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168 | |
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169 | Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts |
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170 | reading at byte offset C<$in_offset>, and starts writing at the current |
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171 | file offset of C<$out_fh>. Because of that, it is not safe to issue more |
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172 | than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each |
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173 | other. |
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174 | |
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175 | This call tries to make use of a native C<sendfile> syscall to provide |
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176 | zero-copy operation. For this to work, C<$out_fh> should refer to a |
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177 | socket, and C<$in_fh> should refer to mmap'able file. |
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178 | |
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179 | If the native sendfile call fails or is not implemented, it will be |
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180 | emulated, so you can call C<aio_sendfile> on any filehandles regardless of |
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181 | the limitations of the OS. |
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182 | |
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183 | Please note, however, that C<aio_sendfile> can read more bytes from |
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184 | C<$in_fh> than are written, and there is no way to find out how many |
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185 | bytes have been read form C<aio_sendfile> alone, as C<aio_sendfile> only |
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186 | provides the number of bytes written to C<$out_fh>. Only if the return |
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187 | value (the value provided to the callback) equals C<$length> one can |
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188 | assume that C<$length> bytes have been read. |
162 | |
189 | |
163 | =item aio_readahead $fh,$offset,$length, $callback |
190 | =item aio_readahead $fh,$offset,$length, $callback |
164 | |
191 | |
165 | C<aio_readahead> populates the page cache with data from a file so that |
192 | C<aio_readahead> populates the page cache with data from a file so that |
166 | subsequent reads from that file will not block on disk I/O. The C<$offset> |
193 | subsequent 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 $nthreads |
287 | |
314 | |
288 | Set the minimum number of AIO threads to C<$nthreads>. The default is |
315 | Set the minimum number of AIO threads to C<$nthreads>. The current default |
289 | C<1>, which means a single asynchronous operation can be done at one time |
316 | is 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). |
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318 | |
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319 | IO::AIO starts threads only on demand, when an AIO request is queued and |
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320 | no free thread exists. |
291 | |
321 | |
292 | It is recommended to keep the number of threads low, as some Linux |
322 | It is recommended to keep the number of threads low, as some Linux |
293 | kernel versions will scale negatively with the number of threads (higher |
323 | kernel versions will scale negatively with the number of threads (higher |
294 | parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32 |
324 | parallelity => MUCH higher latency). With current Linux 2.6 versions, 4-32 |
295 | threads should be fine. |
325 | threads should be fine. |
296 | |
326 | |
297 | Under normal circumstances you don't need to call this function, as this |
327 | Under most circumstances you don't need to call this function, as the |
298 | module automatically starts some threads (the exact number might change, |
328 | module selects a default that is suitable for low to moderate load. |
299 | and is currently 4). |
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300 | |
329 | |
301 | =item IO::AIO::max_parallel $nthreads |
330 | =item IO::AIO::max_parallel $nthreads |
302 | |
331 | |
303 | Sets the maximum number of AIO threads to C<$nthreads>. If more than |
332 | Sets the maximum number of AIO threads to C<$nthreads>. If more than the |
304 | the specified number of threads are currently running, kill them. This |
333 | specified number of threads are currently running, this function kills |
305 | function blocks until the limit is reached. |
334 | them. This function blocks until the limit is reached. |
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335 | |
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336 | While C<$nthreads> are zero, aio requests get queued but not executed |
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337 | until the number of threads has been increased again. |
306 | |
338 | |
307 | This module automatically runs C<max_parallel 0> at program end, to ensure |
339 | This module automatically runs C<max_parallel 0> at program end, to ensure |
308 | that all threads are killed and that there are no outstanding requests. |
340 | that all threads are killed and that there are no outstanding requests. |
309 | |
341 | |
310 | Under normal circumstances you don't need to call this function. |
342 | Under normal circumstances you don't need to call this function. |
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314 | Sets the maximum number of outstanding requests to C<$nreqs>. If you |
346 | Sets the maximum number of outstanding requests to C<$nreqs>. If you |
315 | try to queue up more than this number of requests, the caller will block until |
347 | try to queue up more than this number of requests, the caller will block until |
316 | some requests have been handled. |
348 | some requests have been handled. |
317 | |
349 | |
318 | The default is very large, so normally there is no practical limit. If you |
350 | The default is very large, so normally there is no practical limit. If you |
319 | queue up many requests in a loop it it often improves speed if you set |
351 | queue up many requests in a loop it often improves speed if you set |
320 | this to a relatively low number, such as C<100>. |
352 | this to a relatively low number, such as C<100>. |
321 | |
353 | |
322 | Under normal circumstances you don't need to call this function. |
354 | Under normal circumstances you don't need to call this function. |
323 | |
355 | |
324 | =back |
356 | =back |
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349 | |
381 | |
350 | 1; |
382 | 1; |
351 | |
383 | |
352 | =head2 FORK BEHAVIOUR |
384 | =head2 FORK BEHAVIOUR |
353 | |
385 | |
354 | Before the fork IO::AIO first handles all outstanding requests - if other |
386 | Before the fork, IO::AIO enters a quiescent state where no requests |
355 | threads add requests during this period, this time is prolonged. It then |
387 | can be added in other threads and no results will be processed. After |
356 | enters a quiescent state where no requests can be added in other threads |
388 | the fork the parent simply leaves the quiescent state and continues |
357 | and no results will be processed. After the fork the parent simply leaves |
389 | request/result processing, while the child clears the request/result |
358 | the quiescent state and continues request processing, while the child will |
390 | queue (so the requests started before the fork will only be handled in |
359 | free the request and result queue and start the same number of threads as |
391 | the parent). Threats will be started on demand until the limit ste in the |
360 | were in use by the parent. |
392 | parent process has been reached again. |
361 | |
393 | |
362 | =head1 SEE ALSO |
394 | =head1 SEE ALSO |
363 | |
395 | |
364 | L<Coro>, L<Linux::AIO>. |
396 | L<Coro>, L<Linux::AIO>. |
365 | |
397 | |