First recognising that the sections of 2 Samuel  21-24 are arranged chiastically  is attributed to Karle Budde in 1902.

A: Israel suffer famine because Saul has killed the Gibeonites – Saul’s sons executed (21:1-14)
B: David’s mighty men kill Goliath’s sons (21:15-22)
C:  David’s song of deliverance from his enemies (22:1-51)
C’: David’s last words as the sweet psalmist of Israel (23:1-7)
B’: David’s mighty men and their deeds (23:8-38)
A’: Israel suffer pestilence because David numbered the people (24:1-25)