cache
also: page cache, buffer cache, CPU cache, filesystem cache
A high-speed storage layer that temporarily holds frequently accessed data to reduce retrieval time from slower storage or computation sources.
In Linux, caching occurs at multiple levels: CPU caches (L1, L2, L3) store recently used data from RAM, the page cache holds frequently accessed file data in memory to avoid disk reads, and the buffer cache temporarily stores data being written to disk.
The kernel automatically manages caches to optimize performance. For example, when you read a file repeatedly, the first read fetches it from disk, but subsequent reads are served from the page cache in RAM, which is orders of magnitude faster.
You can view cache statistics using free -h (shows memory cache usage) or cat /proc/meminfo (detailed breakdown). Linux also provides tools like drop_caches to manually clear caches if needed, though this is rarely necessary in production systems.