On Tue, Apr 13, 2021 at 04:53:32PM +0800, Jason Wang wrote:
>
> 在 2021/4/13 下午1:47, Michael S. Tsirkin 写道:
> > There are currently two cases where we poll TX vq not in response to a
> > callback: start xmit and rx napi. We currently do this with callbacks
> > enabled which can cause extra interrupts from the card. Used not to be
> > a big issue as we run with interrupts disabled but that is no longer the
> > case, and in some cases the rate of spurious interrupts is so high
> > linux detects this and actually kills the interrupt.
> >
> > Fix up by disabling the callbacks before polling the tx vq.
> >
> > Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
> > ---
> > drivers/net/virtio_net.c | 2 ++
> > 1 file changed, 2 insertions(+)
> >
> > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > index 82e520d2cb12..16d5abed582c 100644
> > --- a/drivers/net/virtio_net.c
> > +++ b/drivers/net/virtio_net.c
> > @@ -1429,6 +1429,7 @@ static void virtnet_poll_cleantx(struct receive_queue *rq)
> > return;
> > if (__netif_tx_trylock(txq)) {
> > + virtqueue_disable_cb(sq->vq);
> > free_old_xmit_skbs(sq, true);
> > __netif_tx_unlock(txq);
>
>
> Any reason that we don't need to enable the cb here?
Good point ... probably only if the vq isn't empty ...
> And as we discussed in the past, it's probably the time to have a single
> NAPI for both tx and rx?
>
> Thanks
Donnu. I'd like to get a minimal bugfix in, refactoring on top ...
>
> > }
> > @@ -1582,6 +1583,7 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev)
> > bool use_napi = sq->napi.weight;
> > /* Free up any pending old buffers before queueing new ones. */
> > + virtqueue_disable_cb(sq->vq);
> > free_old_xmit_skbs(sq, false);
> > if (use_napi && kick)
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