Re: [GD-General] Scripting Systems

[Eero P. <epa...@ko...>]

Alen Ladavac wrote:

> 
> 
>>Lua is fast.  It's small.  It's trivial to embed.
> 
> 
> 
> Do you think that GC is main speed problem? How about name lookups? Does
> that show on your profile?
> 


For me GC has not been the main problem speed wise, and I do trigger
GC each frame, so that I can minimize "real time" problems with it.

Profilers show the Lua name lookup as a spike in the curves, this might
be partially because the VC++ generated code seems to just hit some kind
of cache line/branch prediction limitation at least on Athlon, when
compiling the Lua hashing function. I suspect that I see the name lookup,
not so much as plain variable lookup, but because it is used when fetching
array elements by name. Local variables them self AFAIK do not need the name
lookup.

The main CPU consumption spike still exists in the Lua virtual machine,
executing the "byte code" interpreter seems to be quite unlucky exercise
for the branch prediction logic in the CPU, and mispredicted branches
hurt a lot on P4/Athlon.


		Eero