UnicastHeader3: reduce in-memory size ------------------------------------- Key: JGRP-2127 URL: https://issues.jboss.org/browse/JGRP-2127 Project: JGroups Issue Type: Enhancement Reporter: Bela Ban Assignee: Bela Ban Priority: Minor Fix For: 4.0 JOL reports: {noformat} org.jgroups.protocols.UnicastHeader3 object internals: OFFSET SIZE TYPE DESCRIPTION VALUE 0 4 (object header) 01 00 00 00 (00000001 00000000 00000000 00000000) (1) 4 4 (object header) 00 00 00 00 (00000000 00000000 00000000 00000000) (0) 8 4 (object header) 9d 11 01 f8 (10011101 00010001 00000001 11111000) (-134147683) 12 2 short Header.prot_id 0 14 2 (alignment/padding gap) N/A 16 8 long UnicastHeader3.seqno 0 24 8 long UnicastHeader3.timestamp 0 32 2 short UnicastHeader3.conn_id 0 34 1 byte UnicastHeader3.type 0 35 1 boolean UnicastHeader3.first false 36 4 (loss due to the next object alignment) Instance size: 40 bytes Space losses: 2 bytes internal + 4 bytes external = 6 bytes total {noformat} We could reduce the size to 32 by making {{timestamp}} an int. This field is used for comparison against previous timestamps, and since the comparison takes numeric overflow into account, wrap-around is not a problem. After the change of {{timestamp}} from {{long}} -> {{int}}: {noformat} org.jgroups.protocols.UnicastHeader3 object internals: OFFSET SIZE TYPE DESCRIPTION VALUE 0 4 (object header) 01 00 00 00 (00000001 00000000 00000000 00000000) (1) 4 4 (object header) 00 00 00 00 (00000000 00000000 00000000 00000000) (0) 8 4 (object header) 9d 11 01 f8 (10011101 00010001 00000001 11111000) (-134147683) 12 2 short Header.prot_id 0 14 2 (alignment/padding gap) N/A 16 8 long UnicastHeader3.seqno 0 24 4 int UnicastHeader3.timestamp 0 28 2 short UnicastHeader3.conn_id 0 30 1 byte UnicastHeader3.type 0 31 1 boolean UnicastHeader3.first false Instance size: 32 bytes Space losses: 2 bytes internal + 0 bytes external = 2 bytes total {noformat}