> > At least according to [1], kernel AIO on Linux still doesn't work
for
> > buffered (i.e. non-O_DIRECT) files. There have been patches
available
> > for quite some time that implement this, but I'm not sure when they
> > are likely to get into the mainline kernel.
> >
> > -Neil
> >
> > [1] http://lse.sourceforge.net/io/aio.html
>
> An improvement is going into 2.6.19 to handle asynchronous
> vector reads and writes. This was covered by Linux Weekly
> News a couple of weeks ago:
> http://lwn.net/Articles/201682/
That is orthogonal. We don't really need vector io so much, since we
rely
on OS readahead. We want asyc IO to tell the OS earlier, that we will
need
these random pages, and continue our work in the meantime.
For random IO it is really important to tell the OS and disk subsystem
many pages in parallel so it can optimize head movements and busy more
than
one disk at a time.
Andreas