Ping localhost: high latency

Installing and Using OpenWrt
1

I just bought a gl-inet B1300 and wondering whether to keep it. While evaluating various performance metrics, I found that the ping times are much higher than for the edgerouter ERX that it is replacing (for cost and consolidation reasons). With ERX (stock firmware), pinging the router had a latency consistently <0.5ms. With the gl-inet B1300 (openwrt), I get a latency of 1-2ms on average with it being up to 30ms for some packets. Then I sshed into the router and pinged localhost and was surprised to see similarly high latency which was in the ballpark as that for pinging from desktop to router.

root@OpenWrt:~# ping localhost
PING localhost (127.0.0.1): 56 data bytes
64 bytes from 127.0.0.1: seq=0 ttl=64 time=0.451 ms
64 bytes from 127.0.0.1: seq=1 ttl=64 time=2.092 ms
64 bytes from 127.0.0.1: seq=2 ttl=64 time=2.916 ms
64 bytes from 127.0.0.1: seq=3 ttl=64 time=3.248 ms
64 bytes from 127.0.0.1: seq=4 ttl=64 time=0.320 ms
64 bytes from 127.0.0.1: seq=5 ttl=64 time=1.621 ms
64 bytes from 127.0.0.1: seq=6 ttl=64 time=2.111 ms
64 bytes from 127.0.0.1: seq=7 ttl=64 time=2.156 ms
64 bytes from 127.0.0.1: seq=8 ttl=64 time=0.319 ms
64 bytes from 127.0.0.1: seq=9 ttl=64 time=2.894 ms
64 bytes from 127.0.0.1: seq=10 ttl=64 time=2.135 ms
64 bytes from 127.0.0.1: seq=11 ttl=64 time=0.329 ms

For comparison, here is the result on my desktop:

[abhishek@optiplex home-aut]$ ping 127.0.0.1
PING 127.0.0.1 (127.0.0.1) 56(84) bytes of data.
64 bytes from 127.0.0.1: icmp_seq=1 ttl=64 time=0.027 ms
64 bytes from 127.0.0.1: icmp_seq=2 ttl=64 time=0.039 ms
64 bytes from 127.0.0.1: icmp_seq=3 ttl=64 time=0.038 ms
64 bytes from 127.0.0.1: icmp_seq=4 ttl=64 time=0.037 ms
64 bytes from 127.0.0.1: icmp_seq=5 ttl=64 time=0.040 ms
64 bytes from 127.0.0.1: icmp_seq=6 ttl=64 time=0.038 ms
64 bytes from 127.0.0.1: icmp_seq=7 ttl=64 time=0.040 ms
64 bytes from 127.0.0.1: icmp_seq=8 ttl=64 time=0.042 ms
64 bytes from 127.0.0.1: icmp_seq=9 ttl=64 time=0.033 ms
64 bytes from 127.0.0.1: icmp_seq=10 ttl=64 time=0.036 ms
64 bytes from 127.0.0.1: icmp_seq=11 ttl=64 time=0.041 ms

I'm fairly sure that this difference would not matter in practice. But I was wondering if I have misconfigured the openwrt (OpenWrt 19.07.3 r11063-85e04e9f46) running on my gl-inet B1300. Also, I am curious to understand why there is a much higher latency on the gl-inet B1300 (vs my desktop).
It would be great if other people having the same router could post their ping localhost results.

2

What was the CPU usage when you ran that test?

1 Like
3

I think the cpu usage was not high. top output was mostly like this:

Mem: 72772K used, 178188K free, 280K shrd, 2528K buff, 9640K cached
CPU:   0% usr   0% sys   0% nic  97% idle   0% io   0% irq   1% sirq
Load average: 0.16 0.09 0.11 2/79 5549
4

Yes, that looks normal, I also think there is something weird there, let's wait for other users to confirm the issue.

2 Likes
5 
# for HOST in 127.0.0.1 ::1 localhost; do mtr -wbc 100 ${HOST}; done
Start: 2020-09-01T12:45:38+0300
HOST: vgrouter              Loss%   Snt   Last   Avg  Best  Wrst StDev
  1.|-- localhost (127.0.0.1)  0.0%   100    0.6   0.6   0.6   0.8   0.0
Start: 2020-09-01T12:47:26+0300
HOST: vgrouter        Loss%   Snt   Last   Avg  Best  Wrst StDev
  1.|-- localhost (::1)  0.0%   100    0.8   0.8   0.8   1.2   0.1
Start: 2020-09-01T12:49:12+0300
HOST: vgrouter        Loss%   Snt   Last   Avg  Best  Wrst StDev
  1.|-- localhost (::1)  0.0%   100    0.8   0.8   0.8   1.1   0.1

# ubus call system board
{
	"kernel": "4.14.187",
	"hostname": "vgrouter",
	"system": "Ralink RT3352 id:1 rev:6",
	"model": "D-Link DIR-620 D1",
	"board_name": "dlink,dir-620-d1",
	"release": {
		"distribution": "OpenWrt",
		"version": "SNAPSHOT",
		"revision": "r13850-e363470d1a",
		"target": "ramips/rt305x",
		"description": "OpenWrt SNAPSHOT r13850-e363470d1a"
	}
}
1 Like
6

You need to use performance governor, on demand causes massive ping spikes on my IPQ4018 router

2 Likes