On Tue, 5 Aug 2025 01:42:53 GMT, Shaojin Wen <[email protected]> wrote:
> The DateTimeFormatterBuilder::FIELD_MAP is of type Map<Character, > TemporalField>, with key values in the range 'A-Z' and 'a-z'. > > We can change the type of FIELD_MAP to an array of length 128 and then use > char as an index to access the array. > > This will reduce the memory usage of DateTimeFormatterBuilder::FIELD_MAP and > improve performance slightly. > > By analyzing the jmap dump memory, we can see that the memory size used by > DateTimeFormatterBuilder::FIELD_MAP has dropped from 1.12kb to 528b, the > number of objects has decreased and the memory has become more flat. as shown > below: > * before > <img width="2018" height="1016" alt="image" > src="https://github.com/user-attachments/assets/57d4c513-55c7-472e-95a8-9f7a4b47662d"; > /> > > * after > <img width="1894" height="352" alt="image" > src="https://github.com/user-attachments/assets/89cbfb6c-360a-475f-85ea-4365d3b66871"; > /> A sensible minor optimization. Looking at this code, I think to accomplish real performance gains, we might need some redesign to simplify the branchiness and speed up lookup. ------------- PR Comment: https://git.openjdk.org/jdk/pull/26634#issuecomment-3344845684
