Connection time out

hi
i have a single node emqx brocker server with 4 core cpu and 4 GB RAM and i tune it step by step from this link:Performance Tuning (Linux) | EMQX 5.1 Documentation
and this is out put of emqx_ctl vm all:
cpu/load1 : 0.05
cpu/load5 : 0.12
cpu/load15 : 0.41
memory/total : 158437376
memory/processes : 54146416
memory/processes_used : 54143048
memory/system : 104290960
memory/atom : 2007425
memory/atom_used : 1994394
memory/binary : 845816
memory/code : 46368262
memory/ets : 10909872
process/limit : 4194304
process/count : 598
io/max_fds : 2097152
io/active_fds : 0
ports/count : 22
ports/limit : 2097152

but whene i test my perfomance, i cant reach more than 1000 Concurrent session

can some one help me please?