Very bad performance on Qemu/KVM
Good morning LKML,
I see extremely slow virtual machines
running on qemu-kvm-0.12.1.2-2.295.el6_3.2.x86_64
on Centos 6.3 with Linux 2.6.32-279.5.2.el6.x86_64 on a 64 core machine using AMD Opteron(TM) Processor 6276 (dell r815).
The guests are Centos 6.3, Linux 2.6.32-220.13.1.el6.x86_64. The disk images reside on local storage, ext4 filesystem.
I checked that kvm is loaded and enabled. I changed -drive to use if=virtio, -net to use model=virtio.
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From the processes running it seems that cpu performance is the
bottleneck. I added -cpu host to skip the emulation, but this did not fix the issue.
Comparing the performance to qemu running on a xenserver, performance is at most half of it.
Does anyone of you have a good pointer how to debug this further or are there any known issues with the given setup?
I'm happy for every pointer I get, as there seems to be no easy to spot issue.
Cheers,
Nico
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