[ILUG] adaptive readahead

[Marcus Furlong]

Hi,

Having recently installed OpenSuse 10.1, I was surprised that it seems much
more responsive and snappier than a gentoo installation on the same machine
with processor-specific CFLAGS and prelinked binaries, etc. On the OpenSuse
site they actually state that prelinking in some cases slows down
applications, and they use an adaptive readahead technique. I was wondering
if anyone could enlighten me as to the differences between the difference
types of adaptive readahead that I've found:

*  There is Behdad Esfahbod's version completed last year for Google's SoC 
   (and used by Red Hat/Fedora I think)

   http://preload.sourceforge.net/


*  There is SUSE's preload (which is not the same as the above one, despite 
   having the same version number, I compared the source for both)

   http://en.opensuse.org/SUPER_preloading
   http://www.novell.com/products/linuxpackages/suselinux/preload.html


*  Debian (and I suppose Ubuntu too?) uses ld.so.preload-manager

   http://packages.debian.org/stable/admin/ld.so.preload-manager


*  Gentoo has readahead-list
  http://packages.gentoo.org/packages/?category=sys-apps;name=readahead-list


Ok so I was wondering if all the above are doing the same thing? If so, does
anyone know which one does it best? (SUSE 10.1 does seem very fast to me,
but I'm not sure about the other distros)

Also, there is Wu Fengguang's kernel version of adaptive readahead:

   http://lkml.org/lkml/2006/5/27/71

which seems to give a 3x speedup in a simple test =>

   http://linux.inet.hr/adaptive_readahead_benchmark.html

Does this do the same thing as the above programs? Will it obsolete them if
it accepted into the kernel?

There is also Con Kolivas's swap prefetch patchset at
http://kernel.kolivas.org and the aforementioned prelink, but AFAIK those
can be used along with adaptive readahead.