Den 23. apr. 2011 00.54 skrev Dave <[email protected]>:
> Hi all,
>
> Since cleaning up the accessors to my native Sprite and Vector
> classes, I've noticed that code as simple as the following triggers
> the memory scavenging quite frequently (about every 2s, taking around
> 5ms on a debug build):
>
Performance measurements done on a debug build are meaningless.
>
> var my_sprite = new Sprite(); // native class
> while (1) {
> var pos = my_sprite.pos; // pos is actually a native vector type
> }
>
> It doesn't really affect performance greatly at the moment or leak
> handles (from what I can tell at least), but it's something that
> doesn't happen if I simply used Sprite/Vector classes that are
> completely defined in Javascript instead of wrapped around native
> types. Should it be expected that accessors which return proxies to
> native types will always add additional memory? From what I can tell,
> I really have no choice since I need to new up an External handle as
> well as the proxy object. A tight loop like my previous example is a
> little unrealistic, but I'm planning on using this in a 30hz game
> loop. It makes me wonder if I need to really limit these type of
> accesses.
>
> I've added some of my code as a reference.
>
> Thanks
> -Dave
>
> // Sprite accessor function for the vector position ("pos")
> Handle<Value> GetPos( Local<String>, const AccessorInfo& info )
> {
> CSprite* pSprite = static_cast<CSprite*>( info.This()-
> >GetPointerFromInternalField(0) );
> assert(pSprite);
>
> Handle<Function> vector_ctor =
> CV8FunctionTemplates::VectorTemplate->GetFunction();
>
> Handle<External> external = External::New(pSprite->GetPos());
> Handle<Value> args[] = {external};
>
> Handle<Object> pos_obj = vector_ctor->NewInstance(1, args);
>
> pos_obj->SetInternalField(1, info.This());
>
> return pos_obj;
> }
>
> // Ctor function for a native vector type
> Handle<Value> CreateVector(const Arguments& args)
> {
> if ( !args.IsConstructCall() )
> {
> ThrowException( String::New("Invalid use of Vector
> constructor!") );
> }
>
> Handle<External> external;
>
> // If there's already a vector, just wrap around it
> // (eg: an accessor call wraps around a pre-existing vector)
> if (args[0]->IsExternal())
> {
> external = Handle<External>::Cast(args[0]);
> }
> // Otherwise, create a brand new vector
> else
> {
> CVector* v = new CVector();
> Persistent<External> pexternal =
> Persistent<External>::New( External::New(v) );
> pexternal.MakeWeak(v, DestroyVector);
> external = pexternal;
>
> V8::AdjustAmountOfExternalAllocatedMemory(sizeof(CVector));
> }
>
> args.This()->SetInternalField(0, external);
>
> return args.This();
> }
>
> --
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> [email protected]
> http://groups.google.com/group/v8-users
>
--
Erik Corry, Software Engineer
Google Denmark ApS - Frederiksborggade 20B, 1 sal,
1360 København K - Denmark - CVR nr. 28 86 69 84
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