Ping is slow even when a server has enough bandwidth

Question

Hello stackoverflow community, I'd like to get help to understand what causes ping to be slow

(This is copied from Stackoverflow following to an advice I've got there)

context

• I have two linux servers.
  1. rasberry pi 4
  • kernel is 5.4.0-1042-raspi
  2. Lenovo n75q tiny gen2
  • kernel is 5.4.0-89-generic
• They have an identical /etc/netplan/99_config.yaml file, and belongs to the same wifi network
• They both are connected with the Internet, and they can retrieve contents from outer wolld. (I mean curl works in both servers)
• Their cpu are not busy, and they have enough mem.

problem

• When accessing to the second server(Lenovo) via ssh, its response is very laggy. (every single typing is laggy)
  • However, it has better bandwidth than rasberry pi.
  • The only curious fact I've found throw investigation on this is, ping to lenovo is slower than to rasberry pi.
• rasberry pi works/responds very smoothly.

question

• What can be the reason why lenovo is laggy when accessing to it via ssh?
• (If the reason is the same as the reason why ping is slow, ) how can I address to fix this issue?

result of iperf

# rasberry pi
[ ID] Interval       Transfer     Bandwidth
[  4] local 192.168.3.13 port 5001 connected with 192.168.3.2 port 52172
[  4]  0.0-12.8 sec   100 MBytes  65.6 Mbits/sec
[  4] local 192.168.3.13 port 5001 connected with 192.168.3.2 port 52248
[  4]  0.0-153.3 sec  1000 MBytes  54.7 Mbits/sec

# lenovo
[ ID] Interval       Transfer     Bandwidth
[  4] local 192.168.3.11 port 5001 connected with 192.168.3.2 port 52163
[  4]  0.0-12.4 sec   100 MBytes  67.6 Mbits/sec
[  4] local 192.168.3.11 port 5001 connected with 192.168.3.2 port 52180
[  4]  0.0-64.8 sec  1000 MBytes   129 Mbits/sec
[  4] local 192.168.3.11 port 5001 connected with 192.168.3.2 port 52312
[  4]  0.0-68.4 sec  1000 MBytes   123 Mbits/sec

result of speedtest

# rasberry pi
$ speedtest
Retrieving speedtest.net configuration...
Testing from Softbank BB ...
Retrieving speedtest.net server list...
Selecting best server based on ping...
Hosted by denpa893 (Tokyo) [4.11 km]: 18.09 ms
Testing download speed................................................................................
Download: 53.25 Mbit/s
Testing upload speed......................................................................................................
Upload: 58.68 Mbit/s

# lenovo
$ speedtest
Retrieving speedtest.net configuration...
Testing from Softbank BB ...
Retrieving speedtest.net server list...
Selecting best server based on ping...
Hosted by NEVERLOSS LLC. (Tokyo) [4.11 km]: 12.093 ms
Testing download speed................................................................................
Download: 189.07 Mbit/s
Testing upload speed......................................................................................................
Upload: 74.77 Mbit/s

result of ping

# rasberry pi
$ ping -s 1000 192.168.3.13
PING 192.168.3.13 (192.168.3.13): 1000 data bytes
1008 bytes from 192.168.3.13: icmp_seq=0 ttl=64 time=79.925 ms
1008 bytes from 192.168.3.13: icmp_seq=1 ttl=64 time=10.203 ms
1008 bytes from 192.168.3.13: icmp_seq=2 ttl=64 time=13.297 ms
1008 bytes from 192.168.3.13: icmp_seq=3 ttl=64 time=9.976 ms
1008 bytes from 192.168.3.13: icmp_seq=4 ttl=64 time=2.932 ms
1008 bytes from 192.168.3.13: icmp_seq=5 ttl=64 time=9.611 ms
1008 bytes from 192.168.3.13: icmp_seq=6 ttl=64 time=2.983 ms
1008 bytes from 192.168.3.13: icmp_seq=7 ttl=64 time=12.698 ms
1008 bytes from 192.168.3.13: icmp_seq=8 ttl=64 time=3.286 ms
1008 bytes from 192.168.3.13: icmp_seq=9 ttl=64 time=3.937 ms
1008 bytes from 192.168.3.13: icmp_seq=10 ttl=64 time=2.689 ms

# lenovo
$ ping -s 1000 192.168.3.11
PING 192.168.3.11 (192.168.3.11): 1000 data bytes
1008 bytes from 192.168.3.11: icmp_seq=0 ttl=64 time=211.042 ms <--- much slower than rasberry pi
1008 bytes from 192.168.3.11: icmp_seq=1 ttl=64 time=26.955 ms
1008 bytes from 192.168.3.11: icmp_seq=2 ttl=64 time=47.657 ms
1008 bytes from 192.168.3.11: icmp_seq=3 ttl=64 time=172.856 ms
1008 bytes from 192.168.3.11: icmp_seq=4 ttl=64 time=194.496 ms
1008 bytes from 192.168.3.11: icmp_seq=5 ttl=64 time=216.379 ms
1008 bytes from 192.168.3.11: icmp_seq=6 ttl=64 time=134.123 ms
1008 bytes from 192.168.3.11: icmp_seq=7 ttl=64 time=155.828 ms

result of traceroute

# rasberry pi
$ traceroute 192.168.3.11
traceroute to 192.168.3.11 (192.168.3.11), 64 hops max, 52 byte packets
 1  ${rasberry pi} (192.168.3.11)  4.122 ms  2.568 ms  2.109 ms

# lenovo
$ traceroute 192.168.3.13
traceroute to 192.168.3.13 (192.168.3.13), 64 hops max, 52 byte packets
 1  * ${lenovo} (192.168.3.13)  105.194 ms  3.069 ms

result of top

# rasberry pi
top - 04:03:38 up  3:30,  1 user,  load average: 0.00, 0.00, 0.00
Tasks: 166 total,   1 running, 165 sleeping,   0 stopped,   0 zombie
%Cpu(s):  0.2 us,  0.2 sy,  0.0 ni, 99.7 id,  0.0 wa,  0.0 hi,  0.0 si,  0.0 st
MiB Mem :   7811.3 total,   6909.1 free,    284.0 used,    618.2 buff/cache
MiB Swap:      0.0 total,      0.0 free,      0.0 used.   7394.4 avail Mem

# lenovo
top - 04:03:54 up  1:45,  1 user,  load average: 0.07, 0.02, 0.00
Tasks: 197 total,   1 running, 196 sleeping,   0 stopped,   0 zombie
%Cpu(s):  0.0 us,  0.5 sy,  0.0 ni, 99.5 id,  0.0 wa,  0.0 hi,  0.0 si,  0.0 st
MiB Mem :  31587.8 total,  30665.4 free,    426.2 used,    496.3 buff/cache
MiB Swap:      0.0 total,      0.0 free,      0.0 used.  30758.7 avail Mem

Answer 1

If iw dev wlan0 get power_save returns on, then set it off with iw dev wlan0 set power_save off and retry. I have no idea though how to set it as default, since at each reboot, it will be back to power save mode.