Struct MapId 

pub struct MapId { /* private fields */ }

Identity of the memory mapping a repacked buffer was built from.

The repack caches below key on a weight’s address, and an address is only a stable identity for as long as the mapping that published it is alive. Unmap one file and map another and the kernel will hand the same address straight back – a textbook ABA. The cache then serves one matrix another matrix’s interleaved bytes, which panicked with an out-of-range slice when the two shapes differed and was SILENT, i.e. wrong output, when they matched.

Holding a std::sync::Weak is what closes it, and it closes both halves at once:

• while the Weak lives, the Arc’s control block cannot be recycled, so Self::id is a unique name for exactly one mapping for as long as the cache entry exists; and
• upgrade() succeeding proves the mapping itself is still alive, which is what makes the address it published still mean what it meant when the entry was written.

A dead Weak is therefore a stale entry, not a hit, and is repacked and replaced. The Weak holds no mapping open, so nothing here keeps a file resident.

Trait Implementations

impl Clone for MapId

fn clone(&self) -> MapId

Returns a duplicate of the value.

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

Performs copy-assignment from source.