Re: Making diff(1) of linux kernels faster

Andrea Arcangeli
2001-10-17T21:30:39Z

On Wed, Oct 17, 2001 at 10:23:37PM +0100, chris@scary.beasts.org wrote:
>
> On Wed, 17 Oct 2001, Andrea Arcangeli wrote:
>
> > I think with directory readahead Marcelo meant a transparent kernel
> > heuristic in the readdir path. ext2_get_page is completly synchronous
> > and it's reading one page at time, that's bad but it can be improved
> > transparently to userspace, just like we do with the files, and also
> > like the old code was doing before the directory in pagecache IIRC.
>
> Do the -ac kernels have the directory in pagecache patch? If not, it could

yes, -ac has it too.

> explain why the -ac kernel performed _much_ better for the
> creat()/stat()/unlink() tests in bonnie++.

It can't explain that. But there was another optimization in -ac that
avoids restarting searching entries from the start of the directory. That
could make a relevant difference. It is included in mainline too starting
from 2.4.10.

Andrea