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=head1 NAME |
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Linux::AIO - linux-specific aio implemented using clone |
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=head1 SYNOPSIS |
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use Linux::AIO; |
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=head1 DESCRIPTION |
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|
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This module implements asynchronous i/o using the means available to linux |
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- clone. It does not hook into the POSIX aio_* functions because linux |
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does not yet support these in the kernel (and even if, it would only allow |
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aio_read and write, not open and stat). |
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|
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Instead, in this module a number of (non-posix) threads are started that |
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execute your read/writes and signal their completion. You don't need |
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thread support in your libc or perl, and the threads created by this |
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module will not be visible to the pthreads library. |
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|
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=over 4 |
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=cut |
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|
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package Linux::AIO; |
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use base 'Exporter'; |
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|
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BEGIN { |
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$VERSION = 1.01; |
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|
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@EXPORT = qw(aio_read aio_write aio_open aio_close aio_stat aio_lstat); |
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@EXPORT_OK = qw(poll_fileno poll_cb min_parallel max_parallel nreqs); |
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|
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require XSLoader; |
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XSLoader::load Linux::AIO, $VERSION; |
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} |
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|
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=item Linux::AIO::min_parallel $nthreads |
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|
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Set the minimum number of AIO threads to C<$nthreads>. You I<have> to call |
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this function with a positive number at least once, otherwise no threads |
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will be started and you aio-operations will seem to hang. |
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|
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It is recommended to keep the number of threads low, as many linux |
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kernel versions will scale negatively with the number of threads (higher |
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parallelity => MUCH higher latency). |
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|
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=item $fileno = Linux::AIO::poll_fileno |
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|
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Return the I<request result pipe filehandle>. This filehandle must be |
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polled for reading by some mechanism outside this module (e.g. Event |
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or select, see below). If the pipe becomes readable you have to call |
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C<poll_cb> to check the results. |
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|
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=item Linux::AIO::poll_cb |
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|
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Process all outstanding events on the result pipe. You have to call this |
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regularly. Returns the number of events processed. Returns immediately |
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when no events are outstanding. |
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|
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You can use Event to multiplex, e.g.: |
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|
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Event->io (fd => Linux::AIO::poll_fileno, |
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poll => 'r', async => 1, |
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cb => \&Linux::AIO::poll_cb ); |
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|
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|
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=item Linux::AIO::nreqs |
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Returns the number of requests currently outstanding. |
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|
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=item aio_open $pathname, $flags, $mode, $callback |
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|
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Asynchronously open or create a file and call the callback with the |
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filedescriptor (NOT a perl filehandle, sorry for that, but watch out, this |
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might change in the future). |
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|
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=item aio_close $fh, $callback |
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Asynchronously close a file and call the callback with the result code. |
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=item aio_read $fh,$offset,$length, $data,$dataoffset,$callback |
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=item aio_write $fh,$offset,$length, $data,$dataoffset,$callback |
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Reads or writes C<length> bytes from the specified C<fh> and C<offset> |
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into the scalar given by C<data> and offset C<dataoffset> and calls the |
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callback without the actual number of bytes read (or C<undef> on error). |
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=item aio_stat $fh_or_path, $callback |
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=item aio_lstat $fh, $callback |
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Works like perl's C<stat> or C<lstat> in void context. The callback will |
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be called after the stat and the results will be available using C<stat _> |
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or C<-s _> etc... |
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|
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Currently, the stats are always 64-bit-stats, i.e. instead of returning an |
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error when stat'ing a large file, the results will be silently truncated |
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unless perl itself is compiled with large file support. |
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|
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=cut |
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|
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END { |
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max_parallel 0; |
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} |
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|
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1; |
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|
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=back |
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=head1 BUGS |
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|
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This module has been extensively tested in a large and very busy webserver |
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for many years now. |
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- aio_open gives a fd, but all other functions expect a perl filehandle. |
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=head1 SEE ALSO |
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|
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L<Coro>. |
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|
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=head1 AUTHOR |
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|
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Marc Lehmann <pcg@goof.com> |
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http://www.goof.com/pcg/marc/ |
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|
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=cut |
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