[maemo-developers] QT map widget

[From: Alberto Mardegan]

kate.alhola at nokia.com wrote:
> Situation is when lot of map tiles are loaded.

"loaded" as in "downloaded"?
About the number of tiles loaded into memory, mappero uses a tile cache, which 
is actually quite big (140 tiles, and tiles are textures sized 256x256 pixels) 
so it may consume quite a bit of memory. But in my case, according to "top" the 
RSS is about 21MB, which doesn't seem so scary.

> I dont't know what 
> internaly happens. Some memory leak ? For application performance and 
> cpu usage also time needed for tile pre-processing need to be counted.

I doubt there are any substantial memory leaks, I've been using mappero for 
several hours without breaks, and didn't notice any worsening.

> Does it some scaling for tiles after loading them ?

No, it does only if the tile of the needed size is missing. But that's something 
you can notice quite easily, because it's quite evident when the pixels are 
being doubled.

> Finally time used for scaling tiles is one key issues. Do we scale them 
> or download every size. How much cpu power is used for scaling or do we 
> leave it all for GPU ?

Every size is downloaded. Scaling happens rarely, and it is done on the CPU; but 
after scaling the texture is stored into the GPU and reused, so the performance 
hit is minimal.

> For mappero case i don't know how much cpu is used for actual scaling 
> and how much by exhausting virtual memory ?

I'm not sure about virtual memory, but about CPU mappero will never use more 
than 30-35% -- it simply isn't allowed by the OS (startup times could be much 
faster if it were...).

Ciao,
   Alberto

-- 
http://blog.mardy.it <-- geek in un lingua international!