Abstract

Directory lookups in large namespaces repeatedly miss the cache and probe the directory index when memory is tight. SplineFS promotes a large, quiet subtree into one shared learned index, absorbs later mutations in an append-only delta, and returns the subtree to the conventional layout when churn persists. Implemented in ext4, SplineFS reduces directory metadata by up to 19.7× and speeds real application stages by up to 2.1×.