Re: [PATCH v4 00/13] virtio-scsi: add iothread-vq-mapping parameter

[Peter Krempa]

On Tue, Mar 11, 2025 at 21:26:03 +0800, Stefan Hajnoczi wrote:
> v4:
> - Squash fixup commit properly this time >_< [Peter]
> v3:
> - Use vq_aio_context[VIRTIO_SCSI_VQ_NUM_FIXED] as the AioContext for the Block
>   Backend [Kevin]
> v2:
> - Only expose cmd vqs via iothread-vq-mapping [Kevin, Peter]
> 
> Implement --device virtio-scsi-pci,iothread-vq-mapping= support so that
> virtqueues can be assigned to different IOThreads. This improves SMP guest
> scalability where I/O-intensive applications can become bottlenecked on a
> single IOThread.
> 
> The following benchmark results show the effect of iothread-vq-mapping. fio
> randread 4k iodepth=64 results from a 4 vCPU guest with an Intel P4800X SSD:
> iothreads IOPS
> ------------------------------
> 1         189576
> 2         312698
> 4         346744

I've modified my libvirt patches to take only the command queues into
account same as with virtio-blk.

After learning how 'fio' works I was able to set multiple iothreads on
fire based on the mapping.

Tested-by: Peter Krempa <pkrempa@redhat.com>