KVM host high level of context switching and interrupt/s


Hi all,

I am using KVM on ubuntu 12.04.02 . full spec:

  • Dell C6220 , 32G RAM , Software RAID1 500GB x 2 , 12 Cores (24 +Hyper)
  • Ubuntu server 12.04.02 Kernel / KVM version 1.00
  • Using virtio on disk and network vhost_net as kernel module
  • Using bridge over bond with 2 network interfaces (1g each , active
    backup mode)

iperf tests I get an excellent trpt of ~ 940Mbit/s on a 1Gb/s port ,
that said I operate 3 centos 5.9 vm’s this box which all together
consume ~ 10Mbit/s o peak times

I am seeing insane numbers of context switching and interrupt per
seconds (Host machine) while the machines are idle most of the time :

~ 50k CS , and SI of ~ 80k , this of course impact performance and I
wonder why on a non busy kvm host I get this number , I red that
vhost_net should improve the network latency as it should bypass the
qemu user level …

Will gladly share all needed information…

Any Ideas?