[Scummvm-devel] Common::HashMap tuning

Kostas Nakos knakos at phys.uoa.gr
Thu Aug 28 13:20:38 CEST 2008

On 08/28/2008 12:14 PM, Max Horn wrote:
> Drawback: The StringMap takes 1356 bytes (on a 32bit machine) of  
> stack space, instead of the 76 it takes now (note that in total, the  
> current StringMap always consumes at least 2772 bytes of *heap*  
> storage -- so in total, we save memory, but also shift some of it from  
> heap to stack). This could be reduced down to say 476 or 876 bytes of  
> stack storage, depending on certain easily tweakable params. See the  
> tracker item for some more details.

This could be a problem. I do not claim proficiency in the inner 
workings of ce's stack and heap handling, but: Currently, the port runs 
with a maximum of 64K stack, and there are serious indications that the 
stack cannot grow too much (perhaps not at all grow bigger than 64K - at 
least for compatibility reasons with older devices). For a cut-down 
operating system like this, conceptually it may be too much to ask to 
juggle memory between stack <-> heap, so there may be some design 
decisions in the spirit of "the stack is from here to there and that's it".

Is it possible for the stringmap use dynamic allocation for the larger 
part of its memory? Perhaps 2 templated varsions for stack and heap 
based allocations? Also, about the malloc call minimization: Is this for 
a reason like "to minimize heap fragmentation"?


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