Currently it gets the list of namespaces then gets the CollectionOptions for each namespace. The second step involves a table-scan of system.namespaces. Due to
SERVER-18622 this happens even if you are only requesting information for a single namespace.
Instead, the storageEngine API should have a way to get all namespaces and their CollectionOptions in one pass. This should speed up both MMAP and KVCatalog-based engines.