Page Cache
The operating system's memory cache of file-backed data used to reduce repeated storage I/O and coalesce writes.
Operating-System Context
The page cache keeps file-backed pages in memory so repeated reads can avoid storage I/O and buffered writes can be coalesced. Benchmarks can accidentally measure RAM instead of the target storage device when the working set fits in cache.
Measurement Boundary
Once the working set exceeds available memory, reclaim and writeback can change the latency distribution sharply. The page cache is also a different layer from an application cache or a database buffer pool.