Re: compat_linux and AIO

[David Laight <david%l8s.co.uk@localhost>]

On Fri, Oct 05, 2012 at 04:16:38PM +0000, David Holland wrote:
> On Fri, Oct 05, 2012 at 04:01:47PM +0000, Emmanuel Dreyfus wrote:
>  > I am playing with oracle XE on 6.0_RC2 and ktrace tells me that this
>  > requires Linux aio_* system calls.
>  > 
>  > Here is the documentation:
>  > http://lse.sourceforge.net/io/aio.html
>  > 
>  > Abd the system call man pages:
>  > http://www.kernel.org/doc/man-pages/online/pages/man2/io_setup.2.html
>  > http://www.kernel.org/doc/man-pages/online/pages/man2/io_submit.2.html
>  > http://www.kernel.org/doc/man-pages/online/pages/man2/io_getevents.2.html
>  > http://www.kernel.org/doc/man-pages/online/pages/man2/io_cancel.2.html
>  > http://www.kernel.org/doc/man-pages/online/pages/man2/io_destroy.2.html
>  > 
>  > How difficult would this be to implement? Anyone has ideas on it?
> 
> Getting AIO working natively first would be a good step. :(

How does Linux handle aio?
I presume it has the same basic problem that all 'normal' unix
systems have in that io is basically synchronous - so async io
just involves getting another lwp to perform the synchronous
request on your behalf.

IIRC, At the moment NetBSD has a single aio worker thread.

Some OS (noteably RSX/11M and windows) always do async io, synchonous
requests just wait for the io to finish.

        David

-- 
David Laight: david%l8s.co.uk@localhost