directfb

[Jim Gettys]

On Wed, 2007-01-10 at 10:46 +0100, Gabor Dolla wrote:
> Hi
> 
> As GTK and Mozilla can be run on top of directfb instead of X don't
> you think that could be an option for OLPC too ?
> 
> http://www.directfb.org/wiki/index.php/Projects:GTK_on_DirectFB
> 
> I guess that would save memory... OLPC does not use many X features,
> no multiple windows, no window manager,
> no network transparent client/server stuff...

There is great mythology around X and memory usage out there, often
encouraged by commercial interests wanting to sell their embedded
wares....  

Part of this has also been encouraged by the lousy memory usage
reporting tools on Linux and other systems; people go look at the
virtual size of the X server, which typically maps the entire frame
buffer (and often entire register file that sometimes is also huge in
address space), and say: X is consuming 270 meg of RAM, or some such
(ignoring that their wizzy graphics cards has 256meg of RAM on it).

Counter examples are the GPE environment running on 16 megabyte
handhelds (e.g. iPAQ). Remember, X was developed on VAX-11/750's with 2
megabytes of RAM.

We do use multiple windows.  We do use a window manager.

And unmodified Linux applications typically "just work".

Most memory issues is stupidity in applications that are independent of
X running or not.  The classic example at the moment is Firefox, which,
finally, is in the process of getting fixed; a year ago, I clocked it as
wasting 250 meg of pixmaps in the X server while using the same amount
in Firefox itself for a total of 500 megabytes, in a single day's use. 
Go look at Federico Mena Quintera's wonderful blog on the topic. 

Removing X won't fix those bugs. X itself is pretty much down in the
noise.  Even X's code size is dwarfed by the toolkit libraries on top
(gtk+, pango, cairo, etc.).  

The way to save memory, for everyone, not just OLPC, is to fix the
broken applications, which we have to do under any circumstances.
Please come help.

And our environment runs on a stock Linux desktop.

Tell me again why using directfb makes any sense for us?
                                 Best regards,
                                           - Jim Gettys

                                    
> 
> Gabor
> 
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-- 
Jim Gettys
One Laptop Per Child