Enum OracleConfig 

#[non_exhaustive]
pub enum OracleConfig {
    Centralised,
}

How timestamps are handed out.

One strategy, deliberately. Two others are described in the literature and were the obvious next steps; both turned out to conflict with the completion ring that computes the read watermark, and neither is offered as a setting that silently does nothing.

Batched — each thread claims a block of stride timestamps with one fetch_add and hands them out locally. It cannot work here: the ring needs commit timestamps to be dense, and a reserved-but-unused timestamp is an permanent hole. Tried as an experiment, it did not merely run slowly, it deadlocked — every committer blocked waiting for a watermark that could never advance. Making it work needs the watermark to track reserved ranges, at which point an idle thread holding a block freezes every snapshot in the system.

Epoch (Silo-style) — a global epoch advances on a timer and transactions are ordered between epochs but not within one, which removes the shared counter from the commit path entirely. The obstacle is not the counter but the two things built on top of it here: visibility would lag by up to an epoch, so “commit, then read it back” would stop working without an extra wait; and SSI revalidates read sets against the read watermark, which would no longer be able to see same-epoch commits. It remains the right answer for a much larger machine.

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.

Centralised

One global atomic counter for commit timestamps.

Exact and totally ordered, and now a bare fetch_add with no lock behind it. The counter is still a shared cache line, but measurement put the watermark’s compare-exchange well ahead of it as the write path’s cost — see Oracle::publish.

Trait Implementations

impl Clone for OracleConfig

fn clone(&self) -> OracleConfig

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for OracleConfig

impl Debug for OracleConfig

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

Formats the value using the given formatter.

impl Default for OracleConfig

fn default() -> OracleConfig

Returns the “default value” for a type.

impl Eq for OracleConfig

impl PartialEq for OracleConfig

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

Equality operator ==.

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

Inequality operator !=.

impl StructuralPartialEq for OracleConfig