Re: [Qemu-devel] [PATCH 0/5] vhost-scsi: Add support for host virtualized target

[Paolo Bonzini]

Il 13/09/2012 22:12, Nicholas A. Bellinger ha scritto:
>> > Are you still seeing the performance degradation discussed in the thread
>> > 
>> >  "vhost-scsi port to v1.1.0 + MSI-X performance regression"
>> > 
> So the performance regression reported here with QEMU v1.2-rc +
> virtio-scsi ended up being related to virtio interrupts being delivered
> across multiple CPUs.
> 
> After explicitly setting the IRQ affinity of the virtio0-request MSI-X
> vector to a specific CPU, the small block (4k) mixed random I/O
> performance jumped back up to the expected ~100K IOPs for a single LUN.

Have you tried setting rq_affinity to 2?  Benchmarking this against
multiqueue virtio-scsi is on my todo list.

Paolo

> FYI, I just tried this again with the most recent QEMU v1.2.50 (v1.3-rc)
> code, and both cases appear to be performing as expected once again
> regardless of the explicit IRQ affinity setting.