I have no idea about that but I am pretty sure that ltcmalloc_minimal is not a plateform dependant configuration so if we keep only plateform dependant stuff, it should be remove.

About this value, I think it is plateform dependant (AND program dependant) as it dependant of the number of core on the computer. Of course it is not the best value but 100 can be a correct threshold for a 2 core processor while it is not a good choice for a 200 core processor.