Applications selection discussion....

[Jim Gettys]

On Thu, 2008-09-04 at 11:24 -0400, Jeremy Katz wrote:
> On Thu, 2008-09-04 at 08:42 -0400, Jim Gettys wrote:
> > On Thu, 2008-09-04 at 01:24 -0400, Greg Dekoenigsberg wrote:
> > > On Wed, 3 Sep 2008, Jeremy Katz wrote:
> > > >> Nor will any existing spin fit in 1GB of internal flash.
> > > >
> > > > We fit on 700 meg CDs, so it's definitely doable.  There's nothing that
> > > > would fundamentally prevent the way we do things for the cds to also
> > > > function off of jffs2.  Two different compressions is kind of silly,
> > > > though.
> > 
> > It is also a performance killer; you're taking a slow processor and
> > having it decompress twice.  We need to get to the bottom of why the
> > current spins are so slow off USB/SD as quickly as possible, while
> > Daniel's native install on SD is very usable.
> 
> As I mentioned earlier in the week, trying off of SD was looking quite a
> bit better as far as usability was concerned.  So I think either I
> picked the wrong USB stick or the one I picked is beginning its death
> throes.

The SD's I have on order haven't come in yet.  Daniel's build is on the
one 4 gig SD I have; I may have a few slower 1-2 gig SD's I can try.

> 
> > Unfortunately, jffs2 does not have a way to say "don't compress a file",
> > though dwmw2 has talked about this from time to time.
> 
> A bit of an aside and not really relevant for the Fedora on XO
> discussion, especially in the short-term, but ubifs might be interesting
> to look at as an alternative to jffs2 as it seems to be adding a lot of
> the things which have stalled out in jffs2
> 
> > Not having wear leveling on bare NAND is a non-starter, if there is any
> > substantial write use.  We may need to page to make a viable system, and
> > will need to page to a file.
> 
> Where did anyone even suggest using the bare NAND?

The internal 1 gig of nand is bare.

Interfaced via the CAFE chip.

Runs very fast at the hardware level (25 MB/second); extremely low
latency, in particular.  We're generally compression limited.

> 
> > > > Also, I did state "off of a USB stick or SD card".  I actually think
> > > > that in a lot of ways, that's better because it means that we can not
> > > > worry about using any of the built-in flash leaving all of it for use
> > > > with Sugar and then wanting to run a joyride build, etc.
> > > 
> > > In my latest discussions with Kim, it seems unlikely that we will be able 
> > > to get something to the hardware manufacturers in time for an "onboard" 
> > > solution anyway.  
> > 
> > But olpc-update allows a late-binding: you can install bits later with
> > no hardware cost.  I'm pretty sure a small enough spin is not very hard
> > to do.
> 
> Making spins is fundamentally trivial.  Adding more variations of things
> to build, support and maintain is not trivial.
> 

I agree; I want, as close as possible, a formal subset of the "normal"
fedora desktop, and not to bring in any packages for OLPC beyond the
minimum.
                         - Jim

-- 
Jim Gettys <jg at laptop.org>
One Laptop Per Child