What is the function of MMU?
A memory management unit (MMU), sometimes called paged memory management unit (PMMU), is a computer hardware unit having all memory references passed through itself, primarily performing the translation of virtual memory addresses to physical addresses.
How does an MMU provide memory protection?
The MMU provides per process address translation of linear (virtual) address to physical addresses. Protection. The MMU entries provide privilege checking and read/write protection of memory. Privilege checking ensures that the processor has the correct privilege level to access a particular memory region.
What is the primary role of MMU in virtual memory?
In order to implement virtual memory, it is necessary for the computer system to have special memory management hardware. A MMU is responsible for translating logical memory into a physical memory address, and for performing checks to make sure the translation can be done and that the access is permitted.
How does MMU translate incoming virtual memory to outgoing physical memory?
The MMU is responsible for the translation between virtual memory addresses and physical memory addresses. With vSphere ESXi, a virtual machine’s vCPU will call out to MMU functionality by the Virtual Machine Monitor (VMM) process, or a hardware MMU supported by a vendor specific CPU offloading instruction.
What is the difference between virtual memory and physical memory?
Physical and virtual memory are forms of memory (internal storage of data). Physical memory exists on chips (RAM memory) and on storage devices such as hard disks. Virtual memory is a process whereby data (e.g., programming code,) can be rapidly exchanged between physical memory storage locations and RAM memory.
What is the difference between a virtual address and a physical address in memory management?
Physical addresses refer to hardware addresses of physical memory. Virtual addresses refer to the virtual store viewed by the process. only a portion of the address space that processes do use is loaded into physical memory at a time.
Why do we need virtual addresses?
Virtual memory serves two purposes. First, it allows us to extend the use of physical memory by using disk. Second, it allows us to have memory protection, because each virtual address is translated to a physical address. Less number of I/O would be needed to load or swap each user program into memory.
Why is virtual address space bigger than physical?
The virtual address space of each process can be smaller or larger than the total physical memory available on the computer. To maximize its flexibility in managing memory, the system can move pages of physical memory to and from a paging file on disk.
What happen if your address space size is bigger than your physical memory?
When a virtual address space is larger than the physical memory, OS can use swapping to evict page frames (e.g. LRU eviction). CPU generates Page Fault where then page that is in disk is swapped into the main memory.
Can be larger than physical address space?
Logical Address space can be larger than physical address space. Explanation: The statement is true. Since, a part of the program needs to be in memory for the process of execution, the logical space can therefore be much larger than the physical address space. Explanation: Demand paging can implement virtual memory.
Where is virtual address space stored?
secondary storage
Can two processes have same virtual address?
2 diff process can have same virtual memory address. This is because each process has its own page table. Each process thinks it as 4Gb memory on a 32-bit machine.
What is the virtual address space for a Windows process?
The virtual address space for a user-mode process is called user space. In 32-bit Windows, the total available virtual address space is 2^32 bytes (4 gigabytes). Usually the lower 2 gigabytes are used for user space, and the upper 2 gigabytes are used for system space.
What is virtual address space explain?
The virtual address space for a process is the set of virtual memory addresses that it can use. The address space for each process is private and cannot be accessed by other processes unless it is shared. Each time a thread references an address, the system translates the virtual address to a physical address.
How do you calculate virtual address size?
31 bits in a virtual address means there are 231 bytes in the virtual memory and if there are 219 pages, then each page would be 231 / 219, which is 231-19 = 212, which is 4096. Thus each page must be 4096 bytes long, or 4K.
Is logical address same as virtual address?
Logical Address is generated by CPU while a program is running. The logical address is virtual address as it does not exist physically, therefore, it is also known as Virtual Address. This address is used as a reference to access the physical memory location by CPU.
Is the least significant part of virtual address?
The least significant 12 bits are the same in both the physical and the virtual address. The page table can be stored anywhere in physical memory, at the discretion of the OS.
What are the components fields of a virtual address?
A virtual address consists of two parts; the page and an offset into that page.