Understanding PageCache: The Secret Behind Faster File Access

This article explains the PageCache mechanism in operating systems, which bridges the performance gap between different storage devices. PageCache uses physical memory to cache frequently accessed data from disk, significantly improving system performance.

The article covers: (1) The performance gap between storage devices - mechanical hard drives can be 100x slower than memory; (2) What PageCache is - physical memory pages that cache disk blocks; (3) File reading process - cache hit vs cache miss scenarios; (4) File writing process - write-through strategy and asynchronous disk synchronization; (5) Experimental verification showing 20x performance improvement when reading the same file twice.

PageCache dynamically adjusts its size based on memory availability, uses LRU algorithms for cache replacement, and employs read-ahead technology for sequential file access. This mechanism is crucial for scenarios like code compilation, configuration file access, video editing, and database operations.