Re: ideas for returning memory to the OS

Jonas Sicking wrote:
> [...] For example a lot of
> objects are holding strings, we most likely will not want to pass
> pointers to the arena into every call to the string classes and pass in
> a pointer to what pool they should use. [...]

But string typically are object on which it's typically worth spending 
time to enhance memory allocation. In that case, it might be worth it to 
over-allocate the string initially, so that often the string classes 
operation won't need to allocate more memory.

I known Mozilla already has a lot of different string classes available 
for various optimizations (even if I don't know the details well), but I 
understand most developers don't use them very well. That's  not very 
surprising because it seems really hard to master. The better solution 
might be to always use the generic class initially, and then have a 
dedicated team that hand-tunes the usage during review, or as benchmarks 
show the need for enhancements for specific modules.

> Nor to every nsVoidArray call
> and tell it which pool to use for its internal buffer.
> [...]

If that internal buffer is a throw away buffer, it should allocated in 
stack.

That's another point on which there might be some very significant gain 
to have : Objects that have a "current function call" lifespan should be 
*fully* allocated on the stack. If the compiler won't cooperate enough 
to make that possible, maybe a "stack arena" is the way to do instead.