Cadence simulation setup

Hi team

I have posted this question on other EE forums and received conflicted answers. But I think no where can give me a better answer then here. So here we go

Now I am using CADENCE IC 617 and MMSIM151 on a Linux machine with 10 cores CPU (20 threads). The simulation setup is like this:

ADE L --> Setup --> High-Performance Simulation Options. Then I click APS. choose Error Preset: DO not override; Use ++aps; Multi_Threading Manual #Threads: 19 (1-19)

But when I try to simulate, the total CPU usage is about 16% and a lot of cores are idle. The total simulation time-steps are 2210000 steps (transient time is 2210ns and simulation step is 0.001ns. ) this cost me more than 2 hours per simulation.

this is the info

[xxxxx@xxxxxx ~]$ top

top - 00:55:30 up 4 days, 2:38, 6 users, load average: 2.00, 1.61, 1.57
Tasks: 422 total, 2 running, 419 sleeping, 0 stopped, 1 zombie
%Cpu(s): 10.1 us, 0.7 sy, 0.0 ni, 89.2 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
KiB Mem : 65727816 total, 538404 free, 3730288 used, 61459124 buff/cache
KiB Swap: 32964604 total, 31957960 free, 1006644 used. 61534544 avail Mem

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
7718 xxxxxxxxxxxx 20 0 1744388 469288 4152 R 206.6 0.7 1460:39 spectre

It seems the CPU is very underused.

My questions are:

1. Does anyone know how I can setup the software to use all or most of the CPU power to speed up the simulation?

2. What dictate the time step of the simulation?

Thank you very much
Allen