d.m[h] = true
	d.mu.Unlock()
	return seen
}

// seenLossy is a variant of seen that avoids a lock by using a cache of recently seen hashes.
// Each cache entry is N-way set-associative: h can appear in any of the slots.
// If h does not appear in any of them, then it is inserted into a random slot,
// overwriting whatever was there before.
func (d *dedup) seenLossy(h uint64) bool {
	cache := &d.recent[uint(h)%uint(len(d.recent))]