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

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Message-ID: <CAF=yD-+mZE3hs2+peMmDBqu=9HrEmghQsSq2LAkcnV5Eb7AJNQ@mail.gmail.com>
Date:   Tue, 24 Jul 2018 20:02:04 -0400
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     caleb.raitto@...il.com, Jason Wang <jasowang@...hat.com>,
        David Miller <davem@...emloft.net>,
        Network Development <netdev@...r.kernel.org>,
        Caleb Raitto <caraitto@...gle.com>
Subject: Re: [PATCH net-next] virtio_net: force_napi_tx module param.

On Tue, Jul 24, 2018 at 6:46 PM Michael S. Tsirkin <mst@...hat.com> wrote:
>
> On Tue, Jul 24, 2018 at 06:31:54PM -0400, Willem de Bruijn wrote:
> > On Tue, Jul 24, 2018 at 6:23 PM Michael S. Tsirkin <mst@...hat.com> wrote:
> > >
> > > On Tue, Jul 24, 2018 at 04:52:53PM -0400, Willem de Bruijn wrote:
> > > > >From the above linked patch, I understand that there are yet
> > > > other special cases in production, such as a hard cap on #tx queues to
> > > > 32 regardless of number of vcpus.
> > >
> > > I don't think upstream kernels have this limit - we can
> > > now use vmalloc for higher number of queues.
> >
> > Yes. that patch* mentioned it as a google compute engine imposed
> > limit. It is exactly such cloud provider imposed rules that I'm
> > concerned about working around in upstream drivers.
> >
> > * for reference, I mean https://patchwork.ozlabs.org/patch/725249/
>
> Yea. Why does GCE do it btw?

I have no idea, either. I guess some host-side constraint.