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Comparing IO-AIO/AIO.pm (file contents):
Revision 1.184 by root, Mon Nov 1 22:03:43 2010 UTC vs.
Revision 1.185 by root, Sat Dec 11 19:06:07 2010 UTC

… …
428reading at byte offset C<$in_offset>, and starts writing at the current 428reading at byte offset C<$in_offset>, and starts writing at the current
429file offset of C<$out_fh>. Because of that, it is not safe to issue more 429file offset of C<$out_fh>. Because of that, it is not safe to issue more
430than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each 430than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
431other. 431other.
432 432
433Please note that C<aio_sendfile> can read more bytes from C<$in_fh> than
434are written, and there is no way to find out how many bytes have been read
435from C<aio_sendfile> alone, as C<aio_sendfile> only provides the number of
436bytes written to C<$out_fh>. Only if the result value equals C<$length>
437one can assume that C<$length> bytes have been read.
438
439Unlike with other C<aio_> functions, it makes a lot of sense to use
440C<aio_sendfile> on non-blocking sockets, as long as one end (typically
441the C<$in_fh>) is a file - the file I/O will then be asynchronous, while
442the socket I/O will be non-blocking. Note, however, that you can run into
443a trap where C<aio_sendfile> reads some data with readahead, then fails
444to write all data, and when the socket is ready the next time, the data
445in the cache is already lost, forcing C<aio_sendfile> to again hit the
446disk. Explicit C<aio_read> + C<aio_write> let's you control resource usage
447much better.
448
433This call tries to make use of a native C<sendfile> syscall to provide 449This call tries to make use of a native C<sendfile> syscall to provide
434zero-copy operation. For this to work, C<$out_fh> should refer to a 450zero-copy operation. For this to work, C<$out_fh> should refer to a
435socket, and C<$in_fh> should refer to an mmap'able file. 451socket, and C<$in_fh> should refer to an mmap'able file.
436 452
437If a native sendfile cannot be found or it fails with C<ENOSYS>, 453If a native sendfile cannot be found or it fails with C<ENOSYS>,
438C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or C<ENOTSOCK>, 454C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or C<ENOTSOCK>,
439it will be emulated, so you can call C<aio_sendfile> on any type of 455it will be emulated, so you can call C<aio_sendfile> on any type of
440filehandle regardless of the limitations of the operating system. 456filehandle regardless of the limitations of the operating system.
441
442Please note, however, that C<aio_sendfile> can read more bytes from
443C<$in_fh> than are written, and there is no way to find out how many
444bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only
445provides the number of bytes written to C<$out_fh>. Only if the result
446value equals C<$length> one can assume that C<$length> bytes have been
447read.
448 457
449 458
450=item aio_readahead $fh,$offset,$length, $callback->($retval) 459=item aio_readahead $fh,$offset,$length, $callback->($retval)
451 460
452C<aio_readahead> populates the page cache with data from a file so that 461C<aio_readahead> populates the page cache with data from a file so that

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