linux-refault-distance · research · also refault distance, nonresident-age distance

Linux refault distance

Linux refault distance is the nonresident-age counter difference used to assess reuse after eviction in the classic workingset path.

In Linux v6.12's classic path, evictions and activations advance nonresident age in page units. A shadow entry stores an eviction snapshot; refault compares it with the counter in the eviction memory-cgroup and NUMA-node context. This is not elapsed time or exact distinct-reference reuse distance. [1]

The eligibility comparison depends on file versus anonymous memory and available swap. Multi-Gen LRU uses separate branches, so the classic formula is not a universal Linux replacement rule. [1]

Shadow timestamps can use coarse buckets, and counter wraparound can make an old entry appear recent. A history match still needs the payload fetched. [1]

Relations

related

Reuse distance, Ghost cache entry, CLOCK-Pro

Citations

1. Linux v6.12 mm/workingset.c: workingset_eviction, workingset_test_recent, workingset_refault and workingset_activation. (accessed 2026-11-07)

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