Struct OrderingHeader 

pub struct OrderingHeader {
    pub magic: u64,
    pub mode: AtomicU32,
    pub stamp_kind: u32,
    pub inversions: AtomicU64,
    pub shared_stamp: AtomicU64,
    pub drainer_token: AtomicU64,
    pub drainer_heartbeat: AtomicU64,
    pub drainer_epoch: AtomicU64,
    /* private fields */
}

Ordering header. One cache line at offset 0 of the region.

Fields

magic: u64

mode: AtomicU32

Active OrderingMode, cross-process visible. The ordered switch is one Release store here; the in-flight backlog is retroactively ordered because the stamps were already there.

stamp_kind: u32

StampKind discriminant. Written once at creation; openers adopt it.

inversions: AtomicU64

Cross-producer inversions observed at pop. The runtime signal that converts the invisible ordering property into “inversions/sec observed”.

shared_stamp: AtomicU64

Stamp counter for StampKind::SharedCounter.

drainer_token: AtomicU64

Drainer lease: (pid << 32) | consumer_id, 0 = unleased.

drainer_heartbeat: AtomicU64

Drainer heartbeat: last drainer_epoch value the holder confirmed liveness at.

drainer_epoch: AtomicU64

Global epoch for heartbeat-grace takeover. Ticked by the sidecar (or any caller); mirrors OwnerLease::tick_epoch.