Re: Compiler warnings with the new base code

[David Chisnall]

On 18 Feb 2010, at 10:42, Richard Frith-Macdonald wrote:

> I think zones *are* somewhat useless...
> 
> There are a *lot* of cases where OSX Foundation does not honor them.

Well, they are on OS X, but I thought they were a bit more useful on GNUstep...

> They are unused when garbage collecting is enabled anyway.

With OS X, yes.  GCKit is designed to support them.

> Also, I strongly suspect that modern computer cache designs mean that the 
> supposed benefit of zones (being able to allocate a group of objects close 
> together in physical memory) has mostly been a fiction for many years now.

Bump-the-pointer allocation is still faster than malloc(), but there are lots 
of other fun things you can do with zones.  For example, I had some 
proof-of-concept code a little while ago that dumped a list of all of the 
classes to a file and then used mmap() to allocate a persistent region of 
memory.  Objects allocated in this zone persisted between program invocations 
automatically (there was some fixup code that would correct the isa pointers 
when you re-mapped the region) as long as they didn't refer to any objects in 
other zones.  You can also use them for per-thread memory pools, to avoid 
locking when allocating or freeing memory, although some malloc() 
implementations will do this automatically.  

David

-- Sent from my Cray X1