Hi, VOIPBunny
Based on your explanation I believe you are looking to monitor throughput rather than CPU utilization. For checking this you could sum up all the incoming bits per second and packets per second the SRX is receiving on all its interfaces and then compare the resulting value with the SRX datasheet values.
Command: > monitor interface traffic
SRX1500-R002 Seconds: 17 Time: 10:16:28
Interface Link Input packets (pps) Output packets (pps)
ge-0/0/0 Up 0 (0) 0 (0)
gr-0/0/0 Up 0 (0) 0 (0)
ip-0/0/0 Up 0 (0) 0 (0)
lt-0/0/0 Up 0 (0) 0 (0)
ge-0/0/1 Up 1152091 (0) 1151378 (0)
ge-0/0/2 Down 0 (0) 0 (0)
ge-0/0/3 Down 0 (0) 0 (0)
ge-0/0/4 Up 1521538 (1) 1521593 (1)
ge-0/0/5 Down 0 (0) 0 (0)
ge-0/0/6 Down 0 (0) 0 (0)
ge-0/0/7 Down 0 (0) 0 (0)
ge-0/0/8 Down 0 (0) 0 (0)
ge-0/0/9 Down 0 (0) 0 (0)
ge-0/0/10 Down 0 (0) 0 (0)
ge-0/0/11 Down 0 (0) 0 (0)
ge-0/0/12 Down 0 (0) 0 (0)
ge-0/0/13 Down 0 (0) 0 (0)
ge-0/0/14 Down 0 (0) 0 (0)
ge-0/0/15 Down 0 (0) 0 (0)
Bytes=b, Clear=c, Delta=d, Packets=p, Quit=q or ESC, Rate=r, Up=^U, Down=^D
Total input packets per second in below output: 1
Pressing letter B, when the output is running, will change the results displayed to bits per second:
SRX1500-R002 Seconds: 36 Time: 10:16:47
Interface Link Input bytes (bps) Output bytes (bps)
ge-0/0/0 Up 0 (0) 0 (0)
gr-0/0/0 Up 0 (0) 0 (0)
ip-0/0/0 Up 0 (0) 0 (0)
lt-0/0/0 Up 0 (0) 0 (0)
ge-0/0/1 Up 96782875 (0) 96747665 (0)
ge-0/0/2 Down 0 (0) 0 (0)
ge-0/0/3 Down 0 (0) 0 (0)
ge-0/0/4 Up 216081068 (2264) 216069947 (2264)
ge-0/0/5 Down 0 (0) 0 (0)
ge-0/0/6 Down 0 (0) 0 (0)
ge-0/0/7 Down 0 (0) 0 (0)
ge-0/0/8 Down 0 (0) 0 (0)
ge-0/0/9 Down 0 (0) 0 (0)
ge-0/0/10 Down 0 (0) 0 (0)
ge-0/0/11 Down 0 (0) 0 (0)
ge-0/0/12 Down 0 (0) 0 (0)
ge-0/0/13 Down 0 (0) 0 (0)
ge-0/0/14 Down 0 (0) 0 (0)
ge-0/0/15 Down 0 (0) 0 (0)
Bytes=b, Clear=c, Delta=d, Packets=p, Quit=q or ESC, Rate=r, Up=^U, Down=^D
Total input bits per second in the below output: 2264
On SRX1500 datasheet you can find the supported pps and bps for this platform:
https://www.juniper.net/assets/us/en/local/pdf/datasheets/1000551-en.pdf
For instance the capacity for "Routing/firewall (IMIX packet size)" is 5Gbps
Note that the numbers showing in the datasheet are just for reference. For your SRX to handle those numbers you need to make sure that the traffic passing your SRX is UDP and that it is sent like the tests mentioned in RFC2544. Still these numbers gives you a good idea of the amount of bps and pps they SRX can process.
Another commands you can use to monitor CPU and session utilization at a given time are the following.
CPU utilization in last 60 seconds:
{primary:node0}
root@SRX1500-R002> show security monitoring performance spu
node0:
--------------------------------------------------------------------------
fpc 0 pic 0
Last 60 seconds:
0: 0 1: 0 2: 0 3: 0 4: 0 5: 0
6: 0 7: 0 8: 0 9: 0 10: 0 11: 0
12: 0 13: 0 14: 0 15: 0 16: 0 17: 0
18: 0 19: 0 20: 0 21: 0 22: 0 23: 0
24: 0 25: 0 26: 0 27: 0 28: 0 29: 0
30: 0 31: 0 32: 0 33: 0 34: 0 35: 0
36: 0 37: 0 38: 0 39: 0 40: 0 41: 0
42: 0 43: 0 44: 0 45: 0 46: 0 47: 0
48: 0 49: 0 50: 0 51: 0 52: 0 53: 0
54: 0 55: 0 56: 0 57: 0 58: 0 59: 0
Session utilization in last 60 seconds:
{primary:node0}
root@SRX1500-R002> show security monitoring performance session
node0:
--------------------------------------------------------------------------
fpc 0 pic 0
Last 60 seconds:
0: 0 1: 0 2: 0 3: 0 4: 0 5: 0
6: 0 7: 0 8: 0 9: 0 10: 0 11: 0
12: 0 13: 0 14: 0 15: 0 16: 0 17: 0
18: 0 19: 0 20: 0 21: 0 22: 0 23: 0
24: 0 25: 0 26: 0 27: 0 28: 0 29: 0
30: 0 31: 0 32: 0 33: 0 34: 0 35: 0
36: 0 37: 0 38: 0 39: 0 40: 0 41: 0
42: 0 43: 0 44: 0 45: 0 46: 0 47: 0
48: 0 49: 0 50: 0 51: 0 52: 0 53: 0
54: 0 55: 0 56: 0 57: 0 58: 0 59: 0
I hope this information helps you!