Struct EvictionPolicy

pub struct EvictionPolicy { /* private fields */ }

The eviction (and admission) policy of a cache.

When the cache is full, the eviction/admission policy is used to determine which items should be admitted to the cache and which cached items should be evicted. The choice of a policy will directly affect the performance (hit rate) of the cache.

The following policies are available:

• TinyLFU (default):
  • Suitable for most workloads.
  • TinyLFU combines the LRU eviction policy and an admission policy based on the historical popularity of keys.
  • Note that it tracks not only the keys currently in the cache, but all hit and missed keys. The data structure used to estimate the popularity of keys is a modified Count-Min Sketch, which has a very low memory footprint (thus the name “tiny”).
• LRU:
  • Suitable for some workloads with strong recency bias, such as streaming data processing.

LFU stands for Least Frequently Used. LRU stands for Least Recently Used.

Use associate function EvictionPolicy::tiny_lfu or EvictionPolicy::lru to obtain an instance of EvictionPolicy.

Implementations

impl EvictionPolicy

pub fn tiny_lfu() -> Self

Returns the TinyLFU policy, which is suitable for most workloads.

TinyLFU is a combination of the LRU eviction policy and the admission policy based on the historical popularity of keys.

Note that it tracks not only the keys currently in the cache, but all hit and missed keys. The data structure used to estimate the popularity of keys is a modified Count-Min Sketch, which has a very low memory footprint (thus the name “tiny”).

pub fn lru() -> Self

Returns the LRU policy.

Suitable for some workloads with strong recency bias, such as streaming data processing.

Trait Implementations

impl Clone for EvictionPolicy

fn clone(&self) -> EvictionPolicy

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for EvictionPolicy

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for EvictionPolicy

fn default() -> EvictionPolicy

Returns the “default value” for a type.