How to use all 4 cores (OPi Zero 2+)?

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Hi guys!

I have a 2Mp webcam connected to OPi zero H3.  It nicely works with mjpg-streamer and  web-server, but stream is only about 10-12 FPS with 1280*720 resolution. 

After running "armbianmonitor -m"  cpu load is only 26-27% 

Time        CPU    load %cpu %sys %usr %nice %io %irq   CPU  C.St.

19:32:15: 1104MHz  0.05  13%   0%  11%   0%   0%   1% 27.7°C  0/7
19:32:20: 1104MHz  0.12  26%   0%  26%   0%   0%   0% 27.6°C  0/7
19:32:25: 1104MHz  0.19  26%   0%  26%   0%   0%   0% 26.7°C  0/7
19:32:30: 1104MHz  0.26  28%   0%  26%   0%   0%   1% 28.3°C  0/7
19:32:36: 1104MHz  0.32  27%   0%  26%   0%   0%   1% 28.1°C  0/7

as i can understand, board now running on only one core. In Raspbian was command "-j4" to use all 4 cores, is there similar command in Armbian?

If it possible, can i turn on additional cores to get more FPS from camera?

Here is command  i use to run stream:

mjpg_streamer -i "/usr/local/lib/input_uvc.so -d /dev/video0 -n -y -r 1280x720  -f 30" -o "/usr/local/lib/output_http.so -n -w /usr/local/www -p 9000" -b

p/s/ camera can run about 20 FPS with same resolution connected to laptop