bufferscache

bufferscache, commonly referred to as the buffer cache, is the portion of a computer's memory used to store recently accessed disk blocks and I/O buffers. Managed by the operating system kernel, it serves as an intermediary between applications and storage devices, allowing subsequent reads for the same data to be satisfied from RAM rather than from disk.

The bufferscache typically contains both file data blocks and filesystem metadata. When a program reads data, the kernel places the corresponding disk blocks into the bufferscache. If the data is needed again, it can be served from memory instead of performing another physical read. Writes may be performed in a write-back fashion: a buffer is marked dirty and written to disk later, either at intervals or under memory pressure or when a sync is requested. This reduces disk I/O and can improve latency.

In some operating systems the bufferscache is a distinct component from the page cache; Linux, for example, historically separated buffer cache from page cache, whereas modern Linux emphasizes a unified page cache for file data. Other systems use a system cache that caches file contents in memory. The cache size and behavior are influenced by available RAM, workload, and kernel tuning parameters.

Performance and management. Keeping frequently accessed blocks in memory speeds up I/O, but unbounded caching can reduce available memory for applications. Operating systems balance cache size against memory pressure, evicting least recently used entries and flushing dirty blocks to storage as needed. Tuning knobs may adjust writeback intervals and caching aggressiveness, but inappropriate settings can degrade performance.