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The (h,k)-paging problem is a generalization of the model of paging problem: Let h,k be positive integers such that . We measure the performance of an algorithm with cache of size h ≤ k {\displaystyle h\leq k} relative to the theoretically optimal page replacement algorithm .
Memory protection is a way to control memory access rights on a computer, and is a part of most modern instruction set architectures and operating systems. The main purpose of memory protection is to prevent a process from accessing memory that has not been allocated to it.
An example is a 32-bit x86 processor with 4 GB and without Physical Address Extension (PAE). In this case, the processor is able to address all the RAM installed and no more. However, even in this case, paging can be used to support more virtual memory than physical memory. For instance, many programs may be running concurrently.
However, many modern operating systems implement their memory access-control schemes via paging instead of segmentation, so it is often the case that invalid memory references in operating systems such as Windows are reported via page faults instead of general protection faults. Operating systems typically provide an abstraction layer (such as ...
By reducing the I/O activity caused by paging requests, virtual memory compression can produce overall performance improvements. The degree of performance improvement depends on a variety of factors, including the availability of any compression co-processors, spare bandwidth on the CPU, speed of the I/O channel, speed of the physical memory, and the compressibility of the physical memory ...
Thrashing occurs when there are too many pages in memory, and each page refers to another page. Real memory reduces its capacity to contain all the pages, so it uses 'virtual memory'. When each page in execution demands that page that is not currently in real memory (RAM) it places some pages on virtual memory and adjusts the required page on RAM.
Unlike virtual storage—paging or segmentation, rollout/rollin does not require any special memory management hardware; however, unless the system has relocation hardware such as a memory map or base and bounds registers, the program must be rolled back in to its original memory locations. Rollout/rollin has been largely superseded by virtual ...
Memory Manager Manages virtual memory, controlling memory protection and the paging of memory in and out of physical memory to secondary storage, and implements a general-purpose allocator of physical memory. It also implements a parser of PE executables that lets an executable be mapped or unmapped in a single, atomic step.