Boot-time improvements

[Timo Jyrinki]

2008/9/9 Jonathan Carter (highvoltage) <jonathan at ubuntu.com>:
> 2. Remove the flashes and brown screens when starting Gnome
>
> Personally, my biggest annoyance as a user is the brown screen that
> flashes between GDM and when Gnome starts. It would be much nicer if gdm
> displayed the greeter for half a second longer, and when Gnome has the
> desktop wallpaper ready, it would do some nice GL transition to the
> actual desktop environment. Where there has to be transitions, it would
> be good to keep it as smooth as possible.

I think this is an excellent point that the GDM would show "logging
in" for as long as desktop wallpaper can be switched to.

> It seems that with the current process, it's close to as fast as it can
> be at the moment. Readahead avoids unnecessary disk seeks.

No, really, I think there is room for at least 5x improvement in disk
seeks. The disk usage is currently terrible, and it is what is is
because of the wish not to do "too much" optimization work so that
there is no risk of breaking any complex setup of programs. The
optimization of disk reads should be possible to do, but it would
require a large amount of careful planning and testing and modifying
different software, working together with the upstream. And some
things like reordering/copying needed files on the disk to eg. a big
sequential file just seems too ugly from technical point of view to
some people, even though there are simply no alternatives to bringing
the same kind of benefits.

The amount of information GNOME reads from disk is probably under
100MB, which modern hard drives read in one second. However, there are
thousands of seeks, and each hundred of those consumes another second
of seeks. The current login time from GDM to GNOME desktop is
something like 20-40s depending on the disk speed, while if you have
the information from disk already in memory (logout and login again),
it might be as low as 3s (excluding compiz which seems very slow).

There also often seems to be new bottle-necks when old ones are fixed,
eg. I'm unsure why intrepid GRUB-to-GDM seems so slow while earlier
GDM-to-GNOME was the most annoying. Also GNOME 2.24 would seem to have
(for me) something preventing the "3s startup" I was seeing in hardy
times with all things cached, even when compiz is disabled.

> If something like Usplash continues to be used, I think it's important
> that it transitions well into the next phase. Not sure if that's even
> possible when using X.

There have been blueprints on the transitions before, so it's probably
very well known that it is wanted at some point. But it needs the new
features from kernel etc. to truly fulfill it. Fedora is indeed
thinking about the stuff already with their Fedora 10, from GRUB menu
to the GNOME/KDE desktop, and I hope they manage to do it well.

-Timo