netdev - Re: [PATCH net-next] virtio_net: force_napi

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Date:   Thu, 2 Aug 2018 01:48:42 +0300
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Willem de Bruijn <willemdebruijn.kernel@...il.com>
Cc:     David Miller <davem@...emloft.net>, caleb.raitto@...il.com,
        Jason Wang <jasowang@...hat.com>,
        Network Development <netdev@...r.kernel.org>,
        Caleb Raitto <caraitto@...gle.com>
Subject: Re: [PATCH net-next] virtio_net: force_napi_tx module param.

On Wed, Aug 01, 2018 at 06:43:53PM -0400, Willem de Bruijn wrote:
>  > > So e.g. we could set an affinity hint to a group of CPUs that
> > > > might transmit to this queue.
> > >
> > > We also want to set the xps mask for all cpus in the group to this queue.
> > >
> > > Is there a benefit over explicitly choosing one cpu from the set, btw?
> >
> > If only one CPU actually transmits on this queue then probably yes.
> > And virtio doesn't know whether that's the case.
> 
> Oh, yes, good example.
> 
> To plumb that through, vp_set_vq_affinity would have to take a cpu
> mask like irq_set_affinity_hint, instead of a single value.
> 
> Though I don't suggest doing that as part of the core
> virtnet_set_affinity changes.

Why not? It seems a reasonable thing to do.

-- 
MST