[nova] iothread support with Libvirt

Eric K. Miller emiller at genesishosting.com
Fri Jan 7 00:15:32 UTC 2022

> For sure!  I would be curious to see the benchmarks. I haven't deployed anything with LVM but I'm surprised that the cost is so high.

No problem.  I'll work on this tonight.

> There is a pretty thin line between the VM --> Libvirt --> Qemu --> LVM. I would expect the performance to be close to baremetal, but lower of course.

The bare metal test is using a logical volume on the same LVM volume group as OpenStack, so it is an easy comparison of VM versus bare metal.

The fact that the bare metal test is ridiculously fast shows that there is significant latency in QEMU/KVM somewhere.  I have seen others that mention they get a maximum of about 190k IOPS, which is still quite a bit, but that is slowly becoming easy to achieve with the latest SSDs, even when writing small random blocks.


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