What is Virtual Memory
Virtual memory is a feature of an operating system.
It uses disk space as an extension of RAM so that the effective size of usable memory can be much larger than the actual amount of RAM present. OS will write the contents of a currently unused block of memory to the hard disk so that the memory can be used for another purpose. When the original contents are needed again, they are read back into memory. This is all made completely transparent to the user
It enables a process to use a memory address space that is independent of other processes running in the same system
Virtual memory is a feature of an operating system.
It uses disk space as an extension of RAM so that the effective size of usable memory can be much larger than the actual amount of RAM present. OS will write the contents of a currently unused block of memory to the hard disk so that the memory can be used for another purpose. When the original contents are needed again, they are read back into memory. This is all made completely transparent to the user
It enables a process to use a memory address space that is independent of other processes running in the same system
How Memory Protection Works
When a program starts up, OS creates a page table for the program, and make sure the disk pages it uses do not conflict with the disk pages of other pro
How Address translation Works
Whenever a program requests access to a memory address, the CPU will always work with this as a virtual memory address
- The CPU splits virtual address into a virtual page number and a page offset.
- The CPU looks into the page table. If the page entry says that the page is not in RAM, it initiates a page fault. This will cause the OS to bring the page into memory. After the OS handles the page fault, it returns back to the same instruction so the CPU ends up trying the instruction over again.
- Otherwise, the CPU loads from the memory address offs within page frame f.
Linux can use either a normal file in the filesystem or a separate partition for swap space. A swap partition is faster, but it is easier to change the size of a swap file (there's no need to repartition the whole hard disk).
When you know how much swap space you need, you should go for a swap partition, but if you are uncertain, you can use a swap file first, use the system for a while so that you can get a feel for how much swap you need, and then make a swap partition when you're confident about its size.
Linux allows one to use several swap partitions and/or swap files at the same time.
Computer science usually distinguishes between swapping (writing the whole process out to swap space) and paging (writing only fixed size parts, usually a few kilobytes, at a time). Paging is usually more efficient, and that's what Linux does.
What is virtual memory:
In computing, virtual memory is a memory management technique that is implemented using both hardware and software. It maps memory addresses used by a program, called virtual addresses, into physical addresses in computer memory.
In computing, virtual memory is a memory management technique that is implemented using both hardware and software. It maps memory addresses used by a program, called virtual addresses, into physical addresses in computer memory.
The operating system manages virtual address spaces and the assignment of real memory to virtual memory. Address translation hardware in the CPU, often referred to as a memory management unit or MMU, automatically translates virtual addresses to physical addresses. Software within the operating system may extend these capabilities to provide a virtual address space that can exceed the capacity of real memory and thus reference more memory than is physically present in the computer.
