src/mongo/db/command_generic_argument.cpp defines:

bool isGenericArgument(StringData arg);
bool isRequestStripArgument(StringData arg);
bool isReplyStripArgument(StringData arg); 

These are implemented by a table lookup via linear search on a std::array of struct, and then returning the value of a bool member of the struct. Two improvements:

1) Switch from linear search to binary search.

2) Each predicate should not have to search through structs that contain a false. That is, search a smaller pre-filtered array such that successful find automatically means the predicate is true.

These predicates are called on every field of every request and response, so their speed feels important.