Re: Mojo

[Matthew Allum <mallum openedhand com>]

Hi;

On Wed, 2008-07-23 at 15:28 +0300, Miko Nieminen wrote:
> 
> It's true that since Ubuntu is desktop distribution Mojo is too, but
> being desktop distribution doesn't make mojo interesting. What makes it
> interesting is the fact that it is full distribution and there are
> corresponding x86 version (Ubuntu) and ARM versions (Mojo). Basically
> the interesting part is just a subset of Mojo, subset which defines
> Gnome Mobile.

Angstrom, Poky also support X86... (and a load of ARM platforms and
other arches). 

> 
> So the real value comes from the fact that almost everything is already
> build as Debian packages and thus you just select your packages and
> start building your applications on top of those. And if you need some
> additional dependencies there are good possibilities that the
> distribution provides those already.

I'll think you'll find both Poky and Angstrom support packaging too and
extra packages, except they'll be more optimised towards embedded use
rather than desktop/server.

> 
> > Its nice to see that most of the desktop applications work on ARM as well, but
> > for Gnome Mobile distributions that target mobile devices such as Angstrom and
> > Poky are much more interesting.
> 
> Once again desktop side isn't the thing, but once again the fact that
> Mojo is a complete distribution.
> 
> Ångström is very interesting as a distribution, but it is build around
> OpenEmbeded which is build around cross-compilation like Maemo and
> that's what we want to get rid of.

In my experience if your developing for ARM cross compiling is just a
necessary evil. Sure building natively may seem nice at first but
further down the line it'll become a hindrance. 

> 
> Mojo goes with native builds (currently by using Qemu) like Debian and
> I'm in favour of that approach. Using native build just works much
> better, check that Andrew's presentation. With cross-compilation you
> need to be quite careful about which versions of different tools to
> select for your toolchain, with native build you don't have that many
> problems.

Native building is extremely slow, expensive and inflexible. Something
like Poky or Angstrom can do multithreaded builds and produce full
complete GNOME Mobile filesystems from scratch in under an hour on cheap
commodity quad core hardware. Native it would take days or a big
cluster. 

In my experience being able to do full filesystem builds from scratch
very quickly is extremely important when it comes to QA, testing,
debugging and profiling. 

Poky, Angstrom come with all the tools set up for you - thats not an
issue. I assume this is true also with Mojo in that it'll also come with
prebuilt tools for running in QEmu ? 

> 
> If I remember correctly building Ubuntu Feisty with Scratchbox, they
> were able to build something like 20-25% with out patching and with
> native build same number was around 80%.

Well this is a moot point as you'll likely end up patching ever* Ubuntu
package as to remove man pages and other desktop/server focused aspects
that make no sense on a consumer Linux device. 

> 
> What comes to Poky, I haven't checked it that well, but isn't it also
> cross-compilation environment?

Yes.

> 
> So far my experiences have been very positive with Mojo and we've be
> doing our things on top of it from the early days. Basically we have
> completely virtualized x86 environment which is configured to match our
> device images and we make our development completely inside it. Then we
> have ARM build images where we build our ARM packages which can be
> installed to the actual device. Basically this was the original idea (I
> suppose also current too) with Scratchbox, but having real virtualized
> environment over chroot-jailed environment just works much better for
> testing the whole system and running it as x86 is just much more
> efficient and you have better tools available.
> 
> Distribution doens't need be Mojo, but currently it is the distribution
> with which we have had least problems and which provides quite nice
> optimisations. Performance differences between ARMv5EL and ARMv6EL-VFP
> are quite noticeable and I suppose difference to Debian's ARM EABI port
> is even greater.
> 
> Any way my actual intention was to point out the existence of Mojo,
> since we have had lot's of good experiences with it. Previously we were
> using Maemo, but it was giving us way too much of headache so we end-up
> trying Mojo and our people have been very satisfied from this move. I
> have to see if I can put our development environment and images out so
> that people could try this approach, but in any case you can build our
> own quite easily.
> 

When you say you were using 'Mameo' what do you mean - to build
images ? 

Have you never actually tried OE or a derivative like Poky or Angstrom ?

  == Matthew