netdev - Re: [PATCH net-next RFC 2/4] virtio-net: transmit napi

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Date:   Mon, 6 Mar 2017 21:33:56 +0200
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     David Miller <davem@...emloft.net>
Cc:     willemdebruijn.kernel@...il.com, jasowang@...hat.com,
        netdev@...r.kernel.org, willemb@...gle.com
Subject: Re: [PATCH net-next RFC 2/4] virtio-net: transmit napi

On Mon, Mar 06, 2017 at 10:55:22AM -0800, David Miller wrote:
> From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
> Date: Mon, 6 Mar 2017 12:50:19 -0500
> 
> >>>   drivers/net/virtio_net.c | 73
> >>> ++++++++++++++++++++++++++++++++++++++++--------
> >>>   1 file changed, 61 insertions(+), 12 deletions(-)
> >>>
> >>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> >>> index 8c21e9a4adc7..9a9031640179 100644
> >>> --- a/drivers/net/virtio_net.c
> >>> +++ b/drivers/net/virtio_net.c
> >>> @@ -33,6 +33,8 @@
> >>>   static int napi_weight = NAPI_POLL_WEIGHT;
> >>>   module_param(napi_weight, int, 0444);
> >>>   +static int napi_tx_weight = NAPI_POLL_WEIGHT;
> >>> +
> >>
> >>
> >> Maybe we should use module_param for this? Or in the future, use
> >> tx-frames-irq for a per-device configuration.
> > 
> > This option should eventually just go away, and napi tx become the
> > standard mode.
> > 
> > In the short term, while we evaluate it on varied workloads, a
> > module_param sounds good to me. In general that is frowned
> > upon, as it leads to different configuration interfaces for each
> > device driver. But that should not be a concern in this limited
> > case.
> 
> In any event, do we really need a TX weight at all?
> 
> I guess you tried this, but why doesn't it not work to just do
> all TX work unconditionally in a NAPI poll pass?  This is how
> we encourage all NIC drivers to handle this.

This seems to be more or less what this driver does already.
So I suspect it can just ignore the weight.

-- 
MST