data.d

[Vladimir Panteleev]

On Thu, 15 Jul 2010 11:03:57 +0300, JimBob <jim at bob.com> wrote:

> VirtualAlloc returns chunks that have 'dwAllocationGranularity'  
> granularity,
> which is 64K on every Windows OS I've used. So allocating a page, 4K,  
> will
> actualy get you 64K.
>
> So using VirtualAlloc as a replacement for malloc is very wasteful unless
> the allocations are larger that 64K.
>
> You might want to look at HeapCreate and it's siblings. (on windows  
> anyway)

dwAllocationGranularity only controls the granularity of the allocation  
address, but not of the allocation size. A simple program that calls  
VirtualAlloc 16384 times uses up 1 GB of the address space, but only 64 MB  
of actual memory. So, while it is a waste of address space, it's not a  
waste of system memory.

I think that using heaps of any kind defeats part of this module's  
purpose, for the reason that due to heap fragmentation it is not possible  
to return memory to the OS directly (which is only possible to do in whole  
pages). There is also a small performance cost involved with using heaps.

-- 
Best regards,
  Vladimir                            mailto:vladimir at thecybershadow.net