The problem is: "a pending write lock acquisition will prevent further read lock acquisitions until fulfilled." Inserts aren't actually guaranteed to be in memo

The problem is: "a pending write lock acquisition will prevent further read lock acquisitions until fulfilled." Inserts aren't actually guaranteed to be in memory, as they're done in a file-backed memory region. A write and page fault can and frequently does cause a flush and hang while that lock is held, particularly as the hot dataset size increases relative to physical RAM.