Re: virtio-fs: adding support for multi-queue

[Stefan Hajnoczi <stefanha@redhat.com>]

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On Tue, Feb 07, 2023 at 11:14:46AM +0100, Peter-Jan Gootzen wrote:
> Hi,
> 
> For my MSc thesis project in collaboration with IBM
> (https://github.com/IBM/dpu-virtio-fs) we are looking to improve the
> performance of the virtio-fs driver in high throughput scenarios. We think
> the main bottleneck is the fact that the virtio-fs driver does not support
> multi-queue (while the spec does). A big factor in this is that our setup on
> the virtio-fs device-side (a DPU) does not easily allow multiple cores to
> tend to a single virtio queue.
> 
> We are therefore looking to implement multi-queue functionality in the
> virtio-fs driver. The request queues seem to already get created at probe,
> but left unused afterwards. The current plan is to select the queue for a
> request based on the current smp processor id and set the virtio queue
> interrupt affinity for each core accordingly at probe.
> 
> This is my first time contributing to the Linux kernel so I am here to ask
> what the maintainers' thoughts are about this plan.

Hi,
Sounds good. Assigning vqs round-robin is the strategy that virtio-net
and virtio-blk use. virtio-blk could be an interesting example as it's
similar to virtiofs. The Linux multiqueue block layer and core virtio
irq allocation handle CPU affinity in the case of virtio-blk.

Which DPU are you targetting?

Stefan

> 
> Best,
> Peter-Jan Gootzen
> MSc student at VU University Amsterdam & IBM Research Zurich
> 

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