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Date: Mon, 6 Mar 2017 17:21:32 +0800 From: Jason Wang <jasowang@...hat.com> To: Willem de Bruijn <willemdebruijn.kernel@...il.com>, netdev@...r.kernel.org Cc: mst@...hat.com, Willem de Bruijn <willemb@...gle.com> Subject: Re: [PATCH net-next RFC 2/4] virtio-net: transmit napi On 2017年03月03日 22:39, Willem de Bruijn wrote: > From: Willem de Bruijn <willemb@...gle.com> > > Convert virtio-net to a standard napi tx completion path. This enables > better TCP pacing using TCP small queues and increases single stream > throughput. > > The virtio-net driver currently cleans tx descriptors on transmission > of new packets in ndo_start_xmit. Latency depends on new traffic, so > is unbounded. To avoid deadlock when a socket reaches its snd limit, > packets are orphaned on tranmission. This breaks socket backpressure, > including TSQ. > > Napi increases the number of interrupts generated compared to the > current model, which keeps interrupts disabled as long as the ring > has enough free descriptors. Keep tx napi optional for now. Follow-on > patches will reduce the interrupt cost. > > Signed-off-by: Willem de Bruijn <willemb@...gle.com> > --- > 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. Thanks
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