Page Cache

Linux Readahead Expands Sequential Page-Cache Reads

A buffered file read can cause Linux to fetch more data than the application explicitly requested. The extra I/O is readahead: the kernel populates nearby page-cache folios in anticipation of continued access. This behavior sits between application read size and storage request size. A process may issue modest read() calls while the kernel submits larger reads to keep later accesses from waiting on storage. Readahead is page-cache speculation Buffered file I/O normally passes through the page cache. When requested file data is absent, the kernel must arrange I/O for that miss. The readahead path can extend that operation across additional folios that are not yet present in the cache.