Re: Asynchronous IO

[Ananth Ananthanarayanan]

Peix Fabrice wrote:
> 
> Hye,
> 
>         Just a little question, when writing a device drivers (char device), i
> implement
>         a read/write method, but where aio is manage, in kernel space or user
> space(glib).
> 
>         thank, and Yops.
> 

With glibc (or more precisely librt), asynchronous I/O is done
with "slave" threads, and hence there is no kernel component.

However, it is advantageous to use "split-phase I/O", so
that the number of outstanding I/Os is not limited by the
number of slave threads as in librt. Split-phase I/o necessarily
involves kernel changes, since the standard system calls such
as read encapsulate both the I/O request & the associated wait.
Have a look at the patch available at http://oss.sgi.com/projects/kaio,
which implements Posix-style AIO with the help of kernel modifications.

ananth.