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

Il 13/09/2012 22:12, Nicholas A. Bellinger ha scritto:

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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.