[sugar] python performance

[Chris Ball]

Hi Neal,

   > * Do we have a wiki that keeps track of the biggest priorities or 
   > things that need the most help?

We don't, though we have a "performance" component in our bugtracker,
and some bugs have "performance" keywords, for example:
   
http://dev.laptop.org/ticket/741 - Activity startup is slow
http://dev.laptop.org/ticket/530 - modules that compile regex import slowly

A wiki page for tracking your investigations sounds excellent.

   > * Are there known ways to reproduce the problems?

Best to ask us on this list if you want to reproduce something that
doesn't have instructions in one of the bugs, I think.

   > * Are these slowdowns noticeable/measurable on faster machines or
   > only on the actual XOs?

Only on the XOs.  For example, we get a 30% improvement in each pybench
score when python is compiled without -fPIC, yet your desktop won't
notice the difference.  The overriding theme for performance generally
on the XOs is that the low cache size (32K L1, no L2) is hurting us;
if you have any ideas for space optimizations for Python or gcc flags
to help in a low-cache situation (besides no -fPIC), we'd be very
interested.

   > I have an XO laptop.  However it might be a problem to build
   > binaries as my desktop is an amd64?  I was able to do a complete
   > build on Ubuntu (although the wiki says it doesn't work).  I had to
   > add a dependency on libncurses-dev and I added that note to the
   > wiki page.  I haven't tried to run/test anything yet.

Yes, that may be a problem.  We do most of our builds on FC5/FC6
machines, which generate binaries that the XOs will just run without
cross-compiling.  If you'd like access to an internal laptop.org machine
running FC5 that you could do compiles on and then ship over to your XO,
I'd be happy to set that up.  (Or you could install Xen/etc locally.)

Thanks!

- Chris.
-- 
Chris Ball   <cjb at laptop.org>