Directory and Inode Caches

Imagine a backend service opens the same configuration file for every request:

Without caching, each open could require the file system to rediscover srv, catalog, config, and features.json, then reload metadata for every object along the route.

Linux avoids most of that repeated namespace work with two related VFS caches:

The dentry cache answers “what object does this name reach here?” while the inode cache answers “what do we already know about this object?”

These caches accelerate path lookup and metadata access. They do not cache regular-file contents; file-data caching is a separate mechanism.

This chapter explains positive and negative dentries, inode-cache identity, warm path walks, namespace coherence, object lifetimes, reclaim, metadata pressure, and how to observe and measure these caches on Linux.