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

 use Linux::AIO;

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. Set the minimum number of AIO threads to CW$nthreads. The default is CW1, 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 many linux kernel versions will scale negatively with the number of threads (higher parallelity => MUCH higher latency).

$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 CWpoll_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::nreqs

Returns the number of requests currently outstanding. 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). Asynchronously close a file and call the callback with the result code. Reads or writes CWlength bytes from the specified CWfh and CWoffset into the scalar given by CWdata and offset CWdataoffset and calls the callback without the actual number of bytes read (or CWundef on error). Works like perl's CWstat or CWlstat in void context. The callback will be called after the stat and the results will be available using CWstat _ or CW-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.

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.

Coro.

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