I noticed we are not very efficient on packing the fields in current instanceKlass.hpp. The 'bool' typed variables, '_is_marked_dependent' and '_has_default_methods' are grouped with u2 typed fields. For both, there are 1byte padding added on 32bit machine. We can pack those two boolean variables together to avoid the padding, then move one of the u2 field to be together with '_init_state' and '_reference_type'. That will save 1byte for free without any real code change.