/ 
Linux-AIO-1.51
River stage zero No dependents
/ Linux::AIO

NAME

Linux::AIO - linux-specific aio implemented using clone

SYNOPSIS

use Linux::AIO;

DESCRIPTION

This module implements asynchronous i/o using the means available to linux - clone. It does not hook into the POSIX aio_* functions because linux does not yet support these in the kernel (and even if, it would only allow aio_read and write, not open and stat).

Instead, in this module a number of (non-posix) threads are started that execute your read/writes and signal their completion. You don't need thread support in your libc or perl, and the threads created by this module will not be visible to the pthreads library.

NOTICE: the threads created by this module will automatically be killed when the thread calling min_parallel exits. Make sure you only ever call min_parallel from the same thread that loaded this module.

Although the module will work with threads, it is not reentrant, so use appropriate locking yourself.

Linux::AIO::min_parallel $nthreads

Set the minimum number of AIO threads to $nthreads. The default is 1, which means a single asynchronous operation can be done at one time (the number of outstanding operations, however, is unlimited).

It is recommended to keep the number of threads low, as some linux kernel versions will scale negatively with the number of threads (higher parallelity => MUCH higher latency).

Linux::AIO::max_parallel $nthreads

Sets the maximum number of AIO threads to $nthreads. If more than the specified number of threads are currently running, kill them. This function blocks until the limit is reached.

This module automatically runs max_parallel 0 at program end, to ensure that all threads are killed and that there are no outstanding requests.

$fileno = Linux::AIO::poll_fileno

Return the request result pipe filehandle. This filehandle must be polled for reading by some mechanism outside this module (e.g. Event or select, see below). If the pipe becomes readable you have to call poll_cb to check the results.

Linux::AIO::poll_cb

Process all outstanding events on the result pipe. You have to call this regularly. Returns the number of events processed. Returns immediately when no events are outstanding.

You can use Event to multiplex, e.g.:

Event->io (fd => Linux::AIO::poll_fileno,
           poll => 'r', async => 1,
           cb => \&Linux::AIO::poll_cb );
Linux::AIO::poll_wait

Wait till the result filehandle becomes ready for reading (simply does a select on the filehandle. This is useful if you want to synchronously wait for some requests to finish).

Linux::AIO::nreqs

Returns the number of requests currently outstanding.

aio_open $pathname, $flags, $mode, $callback

Asynchronously open or create a file and call the callback with the filedescriptor (NOT a perl filehandle, sorry for that, but watch out, this might change in the future).

aio_close $fh, $callback

Asynchronously close a file and call the callback with the result code.

aio_read $fh,$offset,$length, $data,$dataoffset,$callback
aio_write $fh,$offset,$length, $data,$dataoffset,$callback

Reads or writes length bytes from the specified fh and offset into the scalar given by data and offset dataoffset and calls the callback without the actual number of bytes read (or undef on error).

aio_stat $fh_or_path, $callback
aio_lstat $fh, $callback

Works like perl's stat or lstat in void context. The callback will be called after the stat and the results will be available using stat _ or -s _ etc...

Currently, the stats are always 64-bit-stats, i.e. instead of returning an error when stat'ing a large file, the results will be silently truncated unless perl itself is compiled with large file support.

Asynchronously unlink a file.

BUGS

This module has been extensively tested in a large and very busy webserver for many years now.

- aio_open gives a fd, but all other functions expect a perl filehandle.

SEE ALSO

Coro.

AUTHOR

Marc Lehmann <schmorp@schmorp.de>
http://home.schmorp.de/