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The main difference here is that vcpu0 is always at 100% in the virtio-scsi tests. The load is much more balanced between vcpu0 and vcpu1 for virtio-blk.
This applies to both qcow2 and raw actually, but we only see worse performance from it in qcow2. I think we should first analyze/fix this fairness issue to see whether it affects performance, because it's "weird".
(In reply to Amos Kong from comment #5)
> Hi xgao,
>
> can you list the host numanode info and the pin setup info?
Irqblance is running on both host and guest, we didn't do any pin setup on host and guest.
[root@hp-z800-06 ~]# numactl --hardware
available: 2 nodes (0-1)
node 0 cpus: 0 1 2 3
node 0 size: 8175 MB
node 0 free: 7287 MB
node 1 cpus: 4 5 6 7
node 1 size: 8192 MB
node 1 free: 7906 MB
node distances:
node 0 1
0: 10 20
1: 20 10
(In reply to Fam Zheng from comment #8)
> Xiaomei,
>
> This bug has been around for a while and I know we are switching to fio.
> Does latest performance tests have such vcpu fairness measurement (e.g. on
> 6.5, 6.6 and new qemu-kvm)? Can you help confirm if the unfairness is still
> observed?
Okay, We will test the latest 6.6 qemu-kvm and see if the issue still happened. We will update the comment once fresh results are on hand.
(In reply to Xiaomei Gao from comment #9)
> (In reply to Fam Zheng from comment #8)
> > Xiaomei,
> >
> > This bug has been around for a while and I know we are switching to fio.
> > Does latest performance tests have such vcpu fairness measurement (e.g. on
> > 6.5, 6.6 and new qemu-kvm)? Can you help confirm if the unfairness is still
> > observed?
>
> Okay, We will test the latest 6.6 qemu-kvm and see if the issue still
> happened. We will update the comment once fresh results are on hand.
Keeping the needinfo until you have the test results. Thanks.