Vladimir Panteleev wrote:
On Thu, 15 Jul 2010 11:03:57 +0300, JimBob <[email protected]> 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.
In a 32-bit process, the waste of address space is sometimes more
critical nowadays. There is only 2GB virtual memory available (3GB with
some tweaks), and with the example above, VirtualAlloc fails well before
allocating 128 MB.
