clock-replacement · research · also CLOCK, second-chance replacement, FIFO reinsertion

CLOCK cache replacement

CLOCK is a cache replacement policy that gives referenced entries another chance by clearing their reference state during an eviction scan.

Related Observatory article: CLOCK cache replacement on hesela.com

In the one-bit FIFO-reinsertion form compared with SIEVE, a referenced victim candidate is moved to the new end of the queue. SIEVE instead preserves its old position. Similar reference bits do not imply identical eviction choices. [1]

Initial reference state and counter width can differ across implementations. A comparison needs these settings as well as capacity and request order. [2]

Relations

related: sieve-eviction, lru-replacement, adaptive-replacement-cache, cache-pollution

Citations

Yang and colleagues. SIEVE: Cache eviction can be simple, effective, and scalable. USENIX ;login:, 16 June 2024. Author explanation of list ordering. (accessed 2026-10-17)
Hesela: explicit CLOCK settings and complete constructed-trace hit/miss outcomes. (accessed 2026-10-17)

Sources & caveats

The constructed libCacheSim 0.3.5 replay fixes init_freq=0 and n_bit_counter=1; these are experiment settings, not a definition of every CLOCK variant. [2]

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