Re: strange guest slowness after some time

[Tomasz Chmielewski <mangoo@wpkg.org>]

Tomasz Chmielewski schrieb:

> I upgraded ~2 days ago to kvm-84 and the same just happened for a guest 
> with 256 MB memory.
> 
> Note how _time_ is different (similar timings are to other unaffected 
> guests):

This is also pretty interesting:

# ping -c 10 <unaffected guest>
PING 192.168.4.4 (192.168.4.4) 56(84) bytes of data.
64 bytes from 192.168.4.4: icmp_seq=1 ttl=64 time=1.25 ms
64 bytes from 192.168.4.4: icmp_seq=2 ttl=64 time=1.58 ms
64 bytes from 192.168.4.4: icmp_seq=3 ttl=64 time=3.53 ms
64 bytes from 192.168.4.4: icmp_seq=4 ttl=64 time=1.43 ms
64 bytes from 192.168.4.4: icmp_seq=5 ttl=64 time=3.89 ms
64 bytes from 192.168.4.4: icmp_seq=6 ttl=64 time=3.43 ms
64 bytes from 192.168.4.4: icmp_seq=7 ttl=64 time=1.03 ms
64 bytes from 192.168.4.4: icmp_seq=8 ttl=64 time=1.36 ms
64 bytes from 192.168.4.4: icmp_seq=9 ttl=64 time=1.28 ms
64 bytes from 192.168.4.4: icmp_seq=10 ttl=64 time=1.78 ms

--- 192.168.4.4 ping statistics ---
10 packets transmitted, 10 received, 0% packet loss, time 9091ms
rtt min/avg/max/mdev = 1.031/2.059/3.894/1.045 ms



How probable it is so many pings returned with exactly 1000 ms?

# ping -c 10 <affected_guest>
PING 192.168.4.5 (192.168.4.5) 56(84) bytes of data.
64 bytes from 192.168.4.5: icmp_seq=1 ttl=64 time=1009 ms
64 bytes from 192.168.4.5: icmp_seq=2 ttl=64 time=9.61 ms
64 bytes from 192.168.4.5: icmp_seq=3 ttl=64 time=1000 ms
64 bytes from 192.168.4.5: icmp_seq=4 ttl=64 time=1000 ms
64 bytes from 192.168.4.5: icmp_seq=5 ttl=64 time=1000 ms
64 bytes from 192.168.4.5: icmp_seq=6 ttl=64 time=992 ms
64 bytes from 192.168.4.5: icmp_seq=7 ttl=64 time=1000 ms
64 bytes from 192.168.4.5: icmp_seq=8 ttl=64 time=1001 ms
64 bytes from 192.168.4.5: icmp_seq=9 ttl=64 time=1000 ms
64 bytes from 192.168.4.5: icmp_seq=10 ttl=64 time=998 ms

--- 192.168.4.5 ping statistics ---
10 packets transmitted, 10 received, 0% packet loss, time 10025ms
rtt min/avg/max/mdev = 9.610/901.198/1009.161/297.222 ms, pipe 2


This one is with "dd if=/dev/vda of=/dev/null" running on the affected guest:

# ping -c 10 <affected_guest>
PING 192.168.4.5 (192.168.4.5) 56(84) bytes of data.
64 bytes from 192.168.4.5: icmp_seq=1 ttl=64 time=29.4 ms
64 bytes from 192.168.4.5: icmp_seq=2 ttl=64 time=4.56 ms
64 bytes from 192.168.4.5: icmp_seq=3 ttl=64 time=4.05 ms
64 bytes from 192.168.4.5: icmp_seq=4 ttl=64 time=4.20 ms
64 bytes from 192.168.4.5: icmp_seq=5 ttl=64 time=3.82 ms
64 bytes from 192.168.4.5: icmp_seq=6 ttl=64 time=2.47 ms
64 bytes from 192.168.4.5: icmp_seq=7 ttl=64 time=2.16 ms
64 bytes from 192.168.4.5: icmp_seq=8 ttl=64 time=3.89 ms
64 bytes from 192.168.4.5: icmp_seq=9 ttl=64 time=5.98 ms
64 bytes from 192.168.4.5: icmp_seq=10 ttl=64 time=9.16 ms

--- 192.168.4.5 ping statistics ---
10 packets transmitted, 10 received, 0% packet loss, time 9107ms
rtt min/avg/max/mdev = 2.169/6.978/29.439/7.714 ms



-- 
Tomasz Chmielewski
http://wpkg.org