iperf3 write RAM

devce:~ # iperf3 -s -F /tmp/iperf.txt
-----------------------------------------------------------
Server listening on 5201
-----------------------------------------------------------
Accepted connection from 192.168.10.2, port 40130
[  5] local 192.168.10.4 port 5201 connected to 192.168.10.2 port 40132
[ ID] Interval           Transfer     Bitrate
[  5]   0.00-1.00   sec   112 MBytes   935 Mbits/sec
[  5]   1.00-2.00   sec   112 MBytes   941 Mbits/sec
[  5]   2.00-3.00   sec   112 MBytes   941 Mbits/sec
[  5]   3.00-4.00   sec   112 MBytes   941 Mbits/sec
[  5]   4.00-5.00   sec   112 MBytes   941 Mbits/sec
[  5]   5.00-6.00   sec   112 MBytes   942 Mbits/sec
[  5]   6.00-7.00   sec   112 MBytes   941 Mbits/sec
[  5]   7.00-8.00   sec   112 MBytes   941 Mbits/sec
[  5]   8.00-9.00   sec   112 MBytes   941 Mbits/sec
[  5]   9.00-10.00  sec   112 MBytes   941 Mbits/sec
[  5]  10.00-10.00  sec   178 KBytes   749 Mbits/sec
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate
        Sent 1.10 GByte / 1.10 GByte (100%) of /tmp/iperf.txt
[  5]   0.00-10.00  sec  1.10 GBytes   941 Mbits/sec                  receiver