Struct TierConfig 

pub struct TierConfig {
    pub name: String,
    pub capacity_bytes: usize,
    pub access_latency_us: u64,
    pub eviction_policy: EvictionPolicy,
    pub disk_path: Option<PathBuf>,
    pub promotion_threshold: u64,
    pub compress: bool,
    pub adaptive_promotion: bool,
    pub use_arena: bool,
}

Configuration for one tier.

Fields

name: String

Human-readable name (e.g. "L1", "L2", "disk").

capacity_bytes: usize

Maximum number of bytes this tier may hold.

access_latency_us: u64

Simulated read latency in microseconds (used in future work / profiling).

eviction_policy: EvictionPolicy

How entries are selected for eviction when the tier is full.

disk_path: Option<PathBuf>

Optional path to a directory on disk for file-backed storage.

When Some(path), entries evicted from this tier are stored as individual files under path/<key_hash>. Memory entries act as an in-memory index; disk is the actual backing store.

promotion_threshold: u64

Minimum access frequency before a hit in this tier promotes the entry to the previous (hotter) tier.

A value of 0 means “always promote” (original behaviour). A value of 3 means the key must have been accessed at least 3 times in this tier before it is considered hot enough to move up.

compress: bool

Whether to compress entry bytes in this tier.

When true, values are compressed with a simple run-length encoder before being stored and decoded on retrieval. Useful for L2+ tiers to reduce memory / disk footprint.

adaptive_promotion: bool

Whether to use a P² quantile estimator to auto-tune the promotion threshold. When true, the static promotion_threshold acts as a fallback during warmup (first 5 observations); afterwards the 75th percentile of observed per-key access frequencies is used.

use_arena: bool

When true, tier entry bytes are stored in a BumpArena and the HashMap keeps lightweight (offset, len) handles instead of owned Vec<u8>. Falls back to owned storage when false (default).

Implementations

impl TierConfig

pub fn memory(name: impl Into<String>, capacity_bytes: usize) -> Self

Create a minimal in-memory tier config with default values.

pub fn disk( name: impl Into<String>, capacity_bytes: usize, path: impl Into<PathBuf>, ) -> Self

Create a disk-backed tier config.

pub fn enable_adaptive_promotion(self, enabled: bool) -> Self

Enable or disable P²-adaptive promotion threshold tuning.

pub fn enable_arena(self, enabled: bool) -> Self

Enable or disable arena allocation for tier entries.

Trait Implementations

impl Clone for TierConfig

fn clone(&self) -> TierConfig

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for TierConfig

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

Formats the value using the given formatter.