system.cpu.util - always return 0
root@srv:~# while true; do
{ zabbix_get -s SERVER -p 30050 -k system.cpu.util; sleep 2; } done
0.000000
0.000000
0.000000
0.000000
0.000000
0.000000
0.000000
0.000000
0.000000
0.000000
0.000000
0.000000
0.000000
Tell me please what should i do to fix this?