This is normal. The flowd_octeon thread usually runs at high percentage in order to make sure that all the packets received are processed faster. This is why flowd reads high always, however it does not mean that system is busy.
The actual CPU usage can be viewed below.
For Routing Engine (Control Plane) CPU usage:
show chassis routing-engine
For Packet Forwarding Engine (Data Plane) CPU usage:
show chassis forwarding
show security monitoring fpc 0
Here is an output from an SRX240, the multicore processor, people sometimes wonder why the CPU% is 270%, but it is normal, 90% per core.
PID USERNAME THR PRI NICE SIZE RES STATE C TIME WCPU COMMAND
1095 root 7 76 0 499M 49852K select 0 ??? 277.39% flowd_octeon_hm
22 root 1 171 52 0K 16K RUN 0 3720.0 87.21% idle: cpu0
23 root 1 -20 -139 0K 16K WAIT 0 41.1H 0.00% swi7: clock
1120 root 1 76 0 8788K 3740K select 0 582:56 0.00% license-check
5 root 1 -84 0 0K 16K rtfifo 0 502:39 0.00% rtfifo_kern_recv
1086 root 1 76 0 17084K 6696K select 0 325:33 0.00% l2ald
25 root 1 -40 -159 0K 16K WAIT 0 200:36 0.00% swi2: net
1099 root 3 20 0 43940K 13416K sigwai 0 173:25 0.00% authd
And the top -H shows each CPU
PID USERNAME PRI NICE SIZE RES STATE C TIME WCPU COMMAND
1095 root 139 0 499M 49852K CPU3 3 ??? 91.70% flowd_octeon_hm
1095 root 139 0 499M 49852K CPU2 2 ??? 91.70% flowd_octeon_hm
1095 root 139 0 499M 49852K CPU1 1 ??? 91.70% flowd_octeon_hm
1095 root 77 0 499M 49852K RUN 0 ??? 1.46% flowd_octeon_hm
1095 root 76 0 499M 49852K select 0 ??? 0.00% flowd_octeon_hm
1095 root 76 0 499M 49852K select 0 ??? 0.00% flowd_octeon_hm
1095 root 8 0 499M 49852K nanslp 0 ??? 0.00% flowd_octeon_hm
1120 root 76 0 8788K 3740K select 0 582:55 0.00% license-check
1086 root 76 0 17084K 6696K select 0 325:33 0.00% l2ald
1099 root 96 0 43940K 13416K ucond 0 173:25 0.00% authd
1099 root 76 0 43940K 13416K select 0 173:25 0.00% authd
1099 root 20 0 43940K 13416K sigwai 0 173:25 0.00% authd
1088 root 76 0 22016K 6800K select 0 155:18 0.00% pfed