The LockState::isLocked() function beginning on line 59 in src/mongo/db/lockstate.cpp is a low-level routine that is called heavily. It should be modified to be less expensive. It is generally called with a database name (not a full database.collection name) but it always makes a local copy of the portion that appears before the first period, which is usually the full string. If there are cases where a full namespace name is used, that should be a different version of this routine. If this routine is only called with database names, the string copy should be removed.