Sivuvälimuisti

Sivuvälimuisti, or page cache in English, is a technique used in computer operating systems to improve the performance of disk access. It involves reserving a portion of main memory (RAM) to store recently accessed data from disk. When the operating system needs to read data from disk, it first checks if the data is already present in the page cache. If it is, the data can be retrieved much faster from RAM than from the slower disk. This is known as a cache hit. If the data is not in the cache, it is fetched from disk and then also stored in the page cache for potential future use. This is a cache miss.

The page cache is managed dynamically. The operating system tries to keep frequently used data in the cache. When the cache is full and new data needs to be added, the operating system employs algorithms, such as Least Recently Used (LRU), to decide which existing data to remove to make space. The goal is to maximize the hit rate, thus reducing the average time it takes to access disk data. Effective use of the page cache can significantly speed up applications that perform a lot of input/output operations, such as databases, file servers, and large software applications. It is a fundamental component of modern operating system memory management.