jruls is a top-alike utility to display FreeBSD jails resource usage.
RACCT/RCTL should be enabled: add kern.racct.enable=1 to
/boot/loader.conf and restart.
Then just run it; same as with top.
# ./jruls -d1
jid name cpu% mem r/s read w/s writtn
1 www 0 8936K 0 0 0 0
2 tm 0 14.0M 0 0 0 0
3 pms 0 164.5M 0 0 0 0
4 imap 0 11.6M 0 0 0 0
5 homebridge 0 5324K 0 0 0 0
6 fever 0 79.0M 0 0 0 0
7 develop 177 56.0M 10 1280K 1 81
8 chitanka 0 101.6M 0 0 0 0
9 cdns 0 68.7M 0 0 0 0
#
Type make.