The name _read_only_tables_start is ambiguous, as there are multiple read-only tables in the CDS archive. It should be renamed to _serialized_data_start, as that where the data is accessed by {ReadClosure,WriteClosure}::serialize.

See http://hg.openjdk.java.net/jdk/jdk/file/a82fe7a88ce4/src/hotspot/share/memory/metaspaceShared.cpp#l2054