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Pages in the page cache modified after being brought in are called dirty pages. [5] Since non-dirty pages in the page cache have identical copies in secondary storage (e.g. hard disk drive or solid-state drive), discarding and reusing their space is much quicker than paging out application memory, and is often preferred over flushing the dirty pages into secondary storage and reusing their space.
The disk buffer is controlled by the microcontroller in the hard disk drive, and the page cache is controlled by the computer to which that disk is attached. The disk buffer is usually quite small, ranging between 8 MB to 4 GB, and the page cache is generally all unused main memory.
A cache hit occurs when the requested data can be found in a cache, while a cache miss occurs when it cannot. Cache hits are served by reading data from the cache, which is faster than recomputing a result or reading from a slower data store; thus, the more requests that can be served from the cache, the faster the system performs.
This support for larger pages (known as "huge pages" in Linux, "superpages" in FreeBSD, and "large pages" in Microsoft Windows and IBM AIX terminology) allows for "the best of both worlds", reducing the pressure on the TLB cache (sometimes increasing speed by as much as 15%) for large allocations while still keeping memory usage at a reasonable ...
The memory management unit (MMU) inside the CPU stores a cache of recently used mappings from the operating system's page table. This is called the translation lookaside buffer (TLB), which is an associative cache. When a virtual address needs to be translated into a physical address, the TLB is searched first.
Linux uses a unified page cache for brk and anonymous mmaped-regions. This includes the heap and stack of user-space programs. It is written to swap when paged out. Non-anonymous (file-backed) mmaped regions. If present in memory and not privately modified the physical page is shared with file cache or buffer. Shared memory acquired through shm ...
A browser's cache stores temporary website files which allows the site to load faster in future sessions. This data will be recreated every time you visit the webpage, though at times it can become corrupted. Clearing the cache deletes these files and fixes problems like outdated pages, websites freezing, and pages not loading or being ...
The default value is 60; setting it higher can cause high latency if cold pages need to be swapped back in (when interacting with a program that had been idle for example), while setting it lower (even 0) may cause high latency when files that had been evicted from the cache need to be read again, but will make interactive programs more ...