If your docker container do not use all your cpu’s, it may be the case that limits are set in /etc/systemd/system/docker.slice. To apply changed settings I had to reboot my machine (just a restart of docker didn’t change the behaviour).

cat /etc/systemd/system/docker.slice 

[Unit]
Description=Docker Systemd Slice
Before=slices.target

[Slice]
CPUQuota=200%
MemoryAccounting=true
CPUAccounting=true
MemoryLimit=1280M
#StartupCPUWeight=