performance work

[Greg Smith]

Hi All,

Answering two e-mails on one pass.

I agree, its hard work.

Wade,

I believe this thread is about optimizing the XO OS and GUI. That's why 
I call the requirement General_UI_sluggishness.

Optimizing applications is yet another challenge. I'm all for people 
doing that hard work and documenting it so the next person doesn't have 
to re-invent the wheel. Your performance URL is already posted to the 
page in the "tools" section. Let me know if you have any other links 
(GIT URLs?) or e-mails I should make easily accessible.

Michael,

The performance goal I worked out with Eben is on the page already. It 
could be better but its a start.

Lots of people have noticed.

Neil and Jordan analyzed which Cairo calls are causing the most trouble 
and how long they take.  I also broke John's suggestions in to general 
areas: http://wiki.laptop.org/go/Feature_roadmap/General_UI_sluggishness

Could use more editing (e.g. swap suggestions may belong in memory, file 
read/write caching should be added etc.).

You're just scratcing the surface with BW, latency and "messages". CPU 
cycles, process priority, caching, bottleneck definition, instruction 
sets and compilers, word/block/sector size usage, and if you're really 
hard core rows and columns are all optimizable.

If you have an algorithm improvement to offer, I'm all ears.

When we have a critical mass of time from professional engineers we can 
improve performance. Until then it waits and the users wait too.

Let's build on what we have, we're making progress.

Thanks,

Greg S

****************

On Wed, Dec 31, 2008 at 09:20:27AM -0700, Jordan Crouse wrote:
 > The solution to the performance problems is good old fashioned elbow 
grease.... These are the sorts of things that we need to find and
 > squash - and yes, it will be very time consuming and a little boring.

Several anecdotes for your amusement and reflection:

* When was the last time someone posted to devel asking: "what is the
   right algorithm or datastructure for task ____?"

* When was the last time someone publicly analyzed the upper or lower
   bounds on the bandwidth, latency, or quantity of messages necessary to
   accomplish task ____?

* When was the last time that you published a performance goal for your
   software? Did you hit it? Did anyone notice?

Michael

P.S. - Charles Leiserson once remarked that performance is like a
currency which programmers trade for (all) other worthwhile things like
schedule targets, scope of features, other resource consumption, various
kinds of security, etc [1]. This suggests that one would do better to
ask for performance or ____ but not both. Think of Blizzard.

[1] http://www.catonmat.net/blog/mit-introduction-to-algorithms-part-one/

Wade Brainerd wrote:
> I agree with Jordan.  You just have to sit down and do the work to optimize
> the code, either finding the fastest path through hardware and software
> stack.
> I've rewritten Bounce twice now for performance just to hold on to 20fps on
> the XO.  Colors! has been through many performance iterations as well
> (compare v1 and v13 with large brushes).  I've just had my hat handed to me
> by Cairo for Typing Turtle as well (with the hand display enabled, you can
> type about 1WPM).  So I'm looking forward to rewriting my keyboard rendering
> to deal with that.
> 
> If you have an issue with the performance of the XO, just spend the time by
> yourself to analyze it and fix it, talking about it accomplishes nothing.
>  If you find a solution that would help others, post it.
> 
> -Wade
>