What Is The Concept Of Virtual Memory Manager In Windows NT?

The virtual memory portion of the Windows NT executive is the virtual memory manager (VM). The design of the VM manager supposes that the underlying hardware must be supporting the virtual to physical mapping, the whole mechanism of paging, plus also permits the multiple page table entries to map to the same page frame.

The VM manager in Windows NT basically uses a page based management scheme with a page size of 4 KB. The pages of the data that are assigned to a process but are not in physical memory are stored in the paging file on the disk. As we know that, the VM manager uses 32 bit addresses, so each of the process has a 4 GB virtual address space. The upper 2 GB is identical for all of the processes and is mainly used by NT in the kernel mode.

The other lower 2 GB is distinct for every process and is accessible by both the user and the kernel mode threads. There is a two step process that is used by the NT VM manager to allocate the memory. Both of these two steps can share the memory by getting handles to same memory object.

The virtual memory is a space of hard disk that is used by operating system to store data of RAM which is not required urgently. As we know all the processed and unprocessed data in RAM (temporary memory) until the data is saved. Whenever the available amount of RAM is low then some data is stored on the hard disk to free RAM. Using this process computer perform the tasks even there is a shortage of memory.

The virtual memory manager is used to manage the virtual memory settings. We can see the current settings of virtual memory by pressing Window button + break (or right click on my computer icon) and select advanced tab. Here we can see the performance button. After clicking on this we can see current settings of the virtual memory. We can change the settings according to our requirement. This is normally required when we have small amount of RAM. But it is good to have more RAM because the RAM speed is higher than the hard disk speed.

The current settings of virtual memory can also be seen in task manager. Press Ctrl + Alt + Del and select task manager. Click of the performance tab. At the bottom of this tab you can see kernel memory in (Kilo bytes).