Enum TierEvict 

pub enum TierEvict {
    Spill {
        slot: usize,
        key: u64,
        depth: usize,
    },
    Drop {
        slot: usize,
        depth: usize,
    },
}

Outcome of crate::prefix_cache::PrefixCache::evict_snapshot_to_tier.

The spill side of the tier has a cost gate (ATLAS_SSM_SPILL_MIN_TOKENS) mirroring the fault-in side’s ATLAS_SSM_FAULT_MIN_TOKENS, and the gate has to be applied at VICTIM SELECTION, not at the byte move. Gating only the byte move would leave the index entry marked tiered — findable by lookup_tiered — with no blob behind it, so every warm turn would pay a full-blob allocation plus a store.get only to learn it misses.

Both arms free the victim’s HBM slot, so the caller’s invariant “a reclaim always yields a slot” is preserved either way.

Variants

Spill

Move the victim’s bytes to the tier and keep its index entry findable (tiered = true) so a warm turn faults it back instead of recomputing.

Fields

slot: usize

The freed HBM snapshot slot (spill FROM here, then free it).

key: u64

Tier key = the entry’s prefix hash.

depth: usize

Victim depth in tokens — what the spill’s cost buys back.

Drop

Too shallow to be worth a spill: the index entry was REMOVED, no tier key exists, and tier_spills was not incremented. Identical to the pre-tier drop path.

Fields

slot: usize

The freed HBM snapshot slot.

depth: usize

Victim depth in tokens (for the gate-skip log line).

Implementations

impl TierEvict

pub fn slot(&self) -> usize

The freed HBM slot, whichever arm was taken.

Trait Implementations

impl Clone for TierEvict

fn clone(&self) -> TierEvict

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for TierEvict

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

Formats the value using the given formatter.

impl PartialEq for TierEvict

fn eq(&self, other: &TierEvict) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Copy for TierEvict

impl Eq for TierEvict

impl StructuralPartialEq for TierEvict