Enum Sizing 

#[non_exhaustive]
pub enum Sizing {
    NotEnoughData,
    Oversized {
        needed: usize,
    },
    Fits,
    TooSmall,
    MuchTooSmall,
    Thrashing,
}

A verdict on a cache’s capacity, from Stats::sizing.

New verdicts may be added, so a match needs a _ arm.

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

NotEnoughData

Fewer than 10 * cap lookups so far: too early to judge.

Oversized

The cache never filled up. needed entries (the most it ever held) would have been enough: a cache of that size behaves the same and uses less memory.

Fields

needed: usize

The most entries the cache ever held.

Fits

The cache fills up and turns over, and a bigger one would gain little: it is doing what the workload allows (with one-off scans in the traffic, that may be few hits).

TooSmall

Many hits relied on the previous generation not yet being dropped: the keys in use somewhat outnumber cap. A larger cap, up to about twice the current one, would turn those lucky hits into reliable ones.

MuchTooSmall

Many hits relied on the previous generation, and the hit ratio is low: the keys in use outnumber cap several times over. A cap of a few times the current one would help a lot; or the workload has a long tail of keys that rarely come back.

Thrashing

Fewer than one lookup in ten hits: almost nothing is used again before it is dropped. Either the cache is far too small for the keys in use, or the access pattern has little reuse to exploit.

Trait Implementations

impl Clone for Sizing

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for Sizing

impl Debug for Sizing

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

Formats the value using the given formatter.

impl Eq for Sizing

impl PartialEq for Sizing

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

Equality operator ==.

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

Inequality operator !=.

impl StructuralPartialEq for Sizing