Method create

kernels/common/alloc.h:744–800

      }

      static Block* create(Device* device, bool useUSM, size_t bytesAllocate, size_t bytesReserve, Block* next, AllocationType atype)
      {
        /* We avoid using os_malloc for small blocks as this could
         * cause a risk of fragmenting the virtual address space and
         * reach the limit of vm.max_map_count = 65k under Linux. */
        if (atype == EMBREE_OS_MALLOC && bytesAllocate < maxAllocationSize)
          atype = ALIGNED_MALLOC;

        /* we need to additionally allocate some header */
        const size_t sizeof_Header = offsetof(Block,data[0]);
        bytesAllocate = sizeof_Header+bytesAllocate;
        bytesReserve  = sizeof_Header+bytesReserve;

        /* consume full 4k pages with using os_malloc */
        if (atype == EMBREE_OS_MALLOC) {
          bytesAllocate = ((bytesAllocate+PAGE_SIZE-1) & ~(PAGE_SIZE-1));
          bytesReserve  = ((bytesReserve +PAGE_SIZE-1) & ~(PAGE_SIZE-1));
        }

        /* either use alignedMalloc or os_malloc */
        void *ptr = nullptr;
        if (atype == ALIGNED_MALLOC)
        {
          /* special handling for default block size */
          if (bytesAllocate == (2*PAGE_SIZE_2M))
          {
            const size_t alignment = maxAlignment;
            if (device) device->memoryMonitor(bytesAllocate+alignment,false);
            ptr = blockAlignedMalloc(device,useUSM,bytesAllocate,alignment);

            /* give hint to transparently convert these pages to 2MB pages */
            const size_t ptr_aligned_begin = ((size_t)ptr) & ~size_t(PAGE_SIZE_2M-1);
            os_advise((void*)(ptr_aligned_begin +              0),PAGE_SIZE_2M); // may fail if no memory mapped before block
            os_advise((void*)(ptr_aligned_begin + 1*PAGE_SIZE_2M),PAGE_SIZE_2M);
            os_advise((void*)(ptr_aligned_begin + 2*PAGE_SIZE_2M),PAGE_SIZE_2M); // may fail if no memory mapped after block

            return new (ptr) Block(ALIGNED_MALLOC,bytesAllocate-sizeof_Header,bytesAllocate-sizeof_Header,next,alignment);
          }
          else
          {
            const size_t alignment = maxAlignment;
            if (device) device->memoryMonitor(bytesAllocate+alignment,false);
            ptr = blockAlignedMalloc(device,useUSM,bytesAllocate,alignment);
            return new (ptr) Block(ALIGNED_MALLOC,bytesAllocate-sizeof_Header,bytesAllocate-sizeof_Header,next,alignment);
          }
        }
        else if (atype == EMBREE_OS_MALLOC)
        {
          if (device) device->memoryMonitor(bytesAllocate,false);
          bool huge_pages; ptr = os_malloc(bytesReserve,huge_pages);
          return new (ptr) Block(EMBREE_OS_MALLOC,bytesAllocate-sizeof_Header,bytesReserve-sizeof_Header,next,0,huge_pages);
        }
        else
          assert(false);

        return NULL;
      }