[Bug 1079212] [NEW] network slow when 2 VMs using virtio net bridged to same pyhs. network device on kvm host
ITec
1079212 at bugs.launchpad.net
Thu Nov 15 14:25:43 UTC 2012
Public bug reported:
Versions:
----------
Ubuntu: 12.10
linux: 3.5.0-18-generic
bridge-utils 1.5-4ubuntu2
qemu-kvm: 1.2.0+noroms-0ubuntu2
libvirt0: 0.9.13-0ubuntu12
Problem:
----------
When bidirectionally transmitting network data from LAN to two VMs on a
KVM host via a bridged network interface, I have got a significant
performance loss compared to transmissions from LAN to only one VM on
the KVM host.
When bidirectionally transmitting to one VM I get about 1000 Mbit/s in one and 250 Mbit/s in the other direction.
When concurrently, bidirectionally transmitting to two VMs I get about 1000 Mbit/s in one and only 37 Mbit/s in the other direction.
Questions:
------------
So what is the bottle neck?
How can I reach full network bandwith?
Machines:
-----------
ubuntu5 KVM host
ubuntu1 host on same network-switch like ubuntu5
ubuntu4 host on same network-switch like ubuntu5
vm2 KVM virtual machine on ubuntu5
vm3 KVM virtual machine on ubuntu5
Network interfaces:
-----------------------
eth0:ubuntu1 (172.16.2.131) physical network interface eth0 on ubuntu1 1Gbit/s
eth0:ubuntu4 (172.16.2.134) physical network interface eth0 on ubuntu4 1Gbit/s
eth2:ubuntu5 physical network interface eth2 on ubuntu5 1Gbit/s
br2 (172.16.2.125) network bridge on ubuntu5 that VMs connect to
vnet0 virtual network interface that vm2 connects with to br2 (equiv. eth0 on vm2 guest system)
vnet1 virtual network interface that vm3 connects with to br2 (equiv. eth0 on vm3 guest system)
eth0:vm2 (172.16.2.122) virtual network interface on vm2 using virtio
eth0:vm2 (172.16.2.123) virtual network interface on vm3 using virtio
Network map:
----------------
eth0:ubuntu1
|
switch--eth0:ubuntu4
|
eth2:ubuntu5
|
br2-----vnet0(eth0:vm2)
|
vnet1(eth0:vm3)
Performance checks:
------------------------
Performance_01: ubuntu1 <-> vm2:
+ 1191 Mbit/s (932 Mbit/s + 259 Mbit/s)
Performance_02: ubuntu4 <-> vm3:
+ 1209 Mbit/s (938 Mbit/s + 271 Mbit/s)
Performance_03: ubuntu1 <-> vm2 & ubuntu4 <-> vm3:
+ 497 Mbit/s (475 Mbit/s + 22 Mbit/s)
+ 481 Mbit/s (466 Mbit/s + 15 Mbit/s)
---------------------------------------
= 978 Mbit/s (941 Mbit/s + 37 Mbit/s)
Why are Performance_01 and Performance_02 not a bit more like: 2048 Mbit/s (1024 Mbit/s + 1024 Mbit/s)?
Why does it get even less, when I transfer data from/to two different VMs?
37 Mbit/s is very poor! :-(
Here is the output of the commands used:
Performance_01
-------------------
ubuntu5# bmon
# Interface RX Rate RX # TX Rate TX #
-------------------------------------------------------------------
ubuntu5 (source: local)
0 br2 143.00B 3 0.00B 0
13 eth2 117.02MiB 95394 47.80MiB 57761
19 vnet1 0.00B 0 211.00B 3
20 vnet0 45.84MiB 26565 113.50MiB 39413
ubuntu1# iperf -c 172.16.2.122 -t 31536000 -i 10 -d
------------------------------------------------------------
Server listening on TCP port 5001
TCP window size: 85.3 KByte (default)
------------------------------------------------------------
------------------------------------------------------------
Client connecting to 172.16.2.122, TCP port 5001
TCP window size: 16.0 KByte (default)
------------------------------------------------------------
[ 5] local 172.16.2.131 port 58506 connected with 172.16.2.122 port 5001
[ 4] local 172.16.2.131 port 5001 connected with 172.16.2.122 port 47751
[ 5] 0.0-10.0 sec 1.02 GBytes 874 Mbits/sec
[ 4] 0.0-10.0 sec 500 MBytes 420 Mbits/sec
[ 5] 10.0-20.0 sec 1.08 GBytes 932 Mbits/sec
[ 4] 10.0-20.0 sec 419 MBytes 351 Mbits/sec
[ 4] 20.0-30.0 sec 450 MBytes 378 Mbits/sec
[ 5] 20.0-30.0 sec 1.08 GBytes 932 Mbits/sec
[ 4] 30.0-40.0 sec 453 MBytes 380 Mbits/sec
[ 5] 30.0-40.0 sec 1.08 GBytes 932 Mbits/sec
[ 5] 40.0-50.0 sec 1.08 GBytes 932 Mbits/sec
[ 4] 40.0-50.0 sec 309 MBytes 259 Mbits/sec
Performance_02
-------------------
ubuntu5# bmon
# Interface RX Rate RX # TX Rate TX #
-------------------------------------------------------------------
ubuntu5 (source: local)
0 br2 352.00B 5 0.00B 0
13 eth2 27.59MiB 53660 117.32MiB 82784
19 vnet1 112.38MiB 3611 26.59MiB 37871
20 vnet0 169.00B 0 527.00B 7
ubuntu4# iperf -c 172.16.2.123 -t 31536000 -i 10 -d
------------------------------------------------------------
Server listening on TCP port 5001
TCP window size: 85.3 KByte (default)
------------------------------------------------------------
------------------------------------------------------------
Client connecting to 172.16.2.123, TCP port 5001
TCP window size: 92.4 KByte (default)
------------------------------------------------------------
[ 5] local 172.16.2.134 port 58403 connected with 172.16.2.123 port 5001
[ 4] local 172.16.2.134 port 5001 connected with 172.16.2.123 port 41502
[ 4] 0.0-10.0 sec 1.09 GBytes 934 Mbits/sec
[ 5] 0.0-10.0 sec 206 MBytes 173 Mbits/sec
[ 4] 10.0-20.0 sec 1.09 GBytes 940 Mbits/sec
[ 5] 10.0-20.0 sec 212 MBytes 178 Mbits/sec
[ 4] 20.0-30.0 sec 1.09 GBytes 940 Mbits/sec
[ 5] 20.0-30.0 sec 237 MBytes 199 Mbits/sec
[ 5] 30.0-40.0 sec 260 MBytes 218 Mbits/sec
[ 4] 30.0-40.0 sec 1.09 GBytes 939 Mbits/sec
[ 5] 40.0-50.0 sec 323 MBytes 271 Mbits/sec
[ 4] 40.0-50.0 sec 1.09 GBytes 938 Mbits/sec
Performance_03
-------------------
ubuntu5# bmon
# Interface RX Rate RX # TX Rate TX #
-------------------------------------------------------------------
ubuntu5 (source: local)
0 br2 149.00B 2 0.00B 0
13 eth2 5.96MiB 42154 117.34MiB 81736
19 vnet1 55.74MiB 1185 2.38MiB 20075
20 vnet0 56.59MiB 1322 3.47MiB 20275
ubuntu1# iperf -c 172.16.2.122 -t 31536000 -i 10 -d
------------------------------------------------------------
Server listening on TCP port 5001
TCP window size: 85.3 KByte (default)
------------------------------------------------------------
------------------------------------------------------------
Client connecting to 172.16.2.122, TCP port 5001
TCP window size: 16.0 KByte (default)
------------------------------------------------------------
[ 5] local 172.16.2.131 port 54191 connected with 172.16.2.122 port 5001
[ 4] local 172.16.2.131 port 5001 connected with 172.16.2.122 port 47752
[ 5] 0.0-10.0 sec 17.8 MBytes 14.9 Mbits/sec
[ 4] 0.0-10.0 sec 686 MBytes 575 Mbits/sec
[ 5] 10.0-20.0 sec 20.5 MBytes 17.2 Mbits/sec
[ 4] 10.0-20.0 sec 666 MBytes 558 Mbits/sec
[ 4] 20.0-30.0 sec 565 MBytes 474 Mbits/sec
[ 5] 20.0-30.0 sec 18.1 MBytes 15.2 Mbits/sec
[ 5] 30.0-40.0 sec 17.4 MBytes 14.6 Mbits/sec
[ 4] 30.0-40.0 sec 563 MBytes 472 Mbits/sec
[ 4] 40.0-50.0 sec 566 MBytes 475 Mbits/sec
[ 5] 40.0-50.0 sec 26.2 MBytes 22.0 Mbits/sec
ubuntu4# iperf -c 172.16.2.123 -t 31536000 -i 10 -d
------------------------------------------------------------
Server listening on TCP port 5001
TCP window size: 85.3 KByte (default)
------------------------------------------------------------
------------------------------------------------------------
Client connecting to 172.16.2.123, TCP port 5001
TCP window size: 150 KByte (default)
------------------------------------------------------------
[ 3] local 172.16.2.134 port 46644 connected with 172.16.2.123 port 5001
[ 5] local 172.16.2.134 port 5001 connected with 172.16.2.123 port 41503
[ 5] 0.0-10.0 sec 512 MBytes 430 Mbits/sec
[ 3] 0.0-10.0 sec 114 MBytes 96.0 Mbits/sec
[ 5] 10.0-20.0 sec 441 MBytes 370 Mbits/sec
[ 3] 10.0-20.0 sec 28.9 MBytes 24.2 Mbits/sec
[ 5] 20.0-30.0 sec 548 MBytes 460 Mbits/sec
[ 3] 20.0-30.0 sec 27.4 MBytes 23.0 Mbits/sec
[ 5] 30.0-40.0 sec 560 MBytes 469 Mbits/sec
[ 3] 30.0-40.0 sec 15.1 MBytes 12.7 Mbits/sec
[ 5] 40.0-50.0 sec 556 MBytes 466 Mbits/sec
[ 3] 40.0-50.0 sec 18.0 MBytes 15.1 Mbits/sec
** Affects: qemu-kvm (Ubuntu)
Importance: Undecided
Status: New
--
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https://bugs.launchpad.net/bugs/1079212
Title:
network slow when 2 VMs using virtio net bridged to same pyhs. network
device on kvm host
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