Struct LohHeader 

#[repr(C, align(64))]
pub struct LohHeader {
    pub magic: u64,
    pub capacity: u64,
    pub owner_pid: AtomicU64,
    pub epoch: AtomicU64,
    pub _pad_meta: [u8; 24],
    pub tail: AtomicI64,
    pub _pad_tail: [u8; 56],
    pub head: AtomicI64,
    pub _pad_head: [u8; 56],
}

File header. Cache-line aligned. head and tail each get their own cache line so the producer-side tail.fetch_add does not invalidate the consumer-side head line.

Fields

magic: u64

Magic constant.

capacity: u64

Number of ring slots; always a power of two.

owner_pid: AtomicU64

Pid of the owner process; informational. Cleared on close_owner().

epoch: AtomicU64

Epoch counter advanced by the owner on shutdown.

_pad_meta: [u8; 24]

Padding to push tail to its own cache line.

tail: AtomicI64

Producer counter. Owner fetch_add(batch_size) during migration to claim a contiguous block of slots.

_pad_tail: [u8; 56]

Padding to push head to its own cache line.

head: AtomicI64

Consumer counter. Thieves CAS this to claim a slot.

_pad_head: [u8; 56]

Padding round to two whole cache lines after head.