Struct RingHeader 

pub struct RingHeader {
    pub magic: u64,
    pub capacity: u64,
    pub slot_size: u64,
    pub epoch: AtomicU64,
    pub producer_seq: AtomicU64,
    pub consumer_seq: AtomicU64,
    /* private fields */
}

Header layout: three cache lines so the two hot counters never false-share. Line 0 is read-mostly metadata (plus the rarely-written epoch); producer_seq and consumer_seq each get their own line. Every producer CASes producer_seq and every consumer CASes consumer_seq; co-locating them on one line made each side’s CAS invalidate the other side’s copy, serializing the producer and consumer coherence traffic under contention. The SPSC ring separates head/tail for exactly this reason.

Fields

magic: u64

capacity: u64

slot_size: u64

epoch: AtomicU64

Epoch counter; advanced by the watchdog every scan tick. Heartbeats compare against this to detect liveness. Read-mostly from the ring’s perspective, so it shares the metadata line.

producer_seq: AtomicU64

Producer-owned enqueue counter; sole occupant of its line.

consumer_seq: AtomicU64

Consumer-owned dequeue counter; sole occupant of its line.