Support GPU memory preallocation. #110
Description
Right now, GPGMM only supports on-demand allocation. Meaning, GPGMM allocates only when the request is made then later, de-allocates iff the allocation is no longer in use. This is very slow. Instead of allocating memory "as needed", GPGMM could support pre-allocation so a pool of memory is always available or ready-to-allocate. Unfortunately, this could cause OOM frequently so the behavior must be optional.