Re: [RFC] kernel facilities for cache prefetching

[Wu Fengguang <wfg@mail.ustc.edu.cn>]

On Tue, May 02, 2006 at 10:55:29AM +0200, Arjan van de Ven wrote:
> > Yes, I find it hard to improve the boot time of the init.d stage.
> > However, it is perfectly ok to preload all GUI staffs during that
> > timespan, by overlapping CPU/IO activities.
> 
> fwiw fedora even loads a bunch of GUI apps into memory already

Hopefully the warm cache time has been improving.
I have very good performance with fluxbox.  Lubos Lunak said
(http://wiki.kde.org/tiki-index.php?page=KDE%20Google%20SoC%202006%20ideas#id106304)
that "KDE startup with cold caches is several times slower than with
warm caches." The latest GNOME release also saw good speedup.

> > > Another interesting approach would be to actually put all the data you
> > > want to use in a non-fragmented, sequential area on disk somehow (there
> > > is an OLS paper submitted about that by Ben) so that at least the disk
> > > side is seekless... 
> > 
> > You are right, reducing seeking distances helps not much. My fluxbox
> > desktop requires near 3k seeks, which can be loaded in the 20s init.d
> > booting time.  But for KDE/GNOME desktops, some defragging would be
> > necessary to fit them into the 20s time span.
> 
> or just move the blocks (or copy them) to a reserved area...

Ah, we can save discontinuous pages into the journal file on umounting
and restore them on mounting. But let's do the simple way first :)

Wu