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When pure demand paging is used, pages are loaded only when they are referenced. A program from a memory mapped file begins execution with none of its pages in RAM. As the program commits page faults, the operating system copies the needed pages from a file, e.g., memory-mapped file, paging file, or a swap partition containing the page data ...
zswap is a Linux kernel feature that provides a compressed write-back cache for swapped pages, as a form of virtual memory compression. Instead of moving memory pages to a swap device when they are to be swapped out, zswap performs their compression and then stores them into a memory pool dynamically allocated in the system RAM.
In computing, resident set size (RSS) is the portion of memory (measured in kilobytes) occupied by a process that is held in main memory ().The rest of the occupied memory exists in the swap space or file system, either because some parts of the occupied memory were paged out, or because some parts of the executable were never loaded.
If processes are utilizing all main memory and need additional memory pages, a cascade of severe cache misses known as page faults will occur, often leading to a noticeable lag in the operating system responsiveness. This process together with the futile, repetitive page swapping that occurs is known as "thrashing".
%Cpu(s) counts the percentage of CPU usage, broken down into categories. MiB Mem: Memory usage in units of mebibyte. The buff/cache is for memory used by buffers and cache. MiB Swap: Swap space usage in units of mebibyte. If the system needs more memory resources and the RAM is full, inactive pages in memory are moved to the swap space.
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 ...
Similarly, a page frame is the smallest fixed-length contiguous block of physical memory into which memory pages are mapped by the operating system. [ 1 ] [ 2 ] [ 3 ] A transfer of pages between main memory and an auxiliary store, such as a hard disk drive , is referred to as paging or swapping.
Memory swapping is then used to handle spikes in memory usage. The disadvantage of this approach is that memory swap files are slower to read from than 'actual' memory, which can lead to performance drops. [2]