Jesper Dangaard Brouer
2021-Feb-25 17:01 UTC
[PATCH v2 net-next] virtio-net: support XDP_TX when not more queues
On Thu, 25 Feb 2021 16:22:29 +0800 Xuan Zhuo <xuanzhuo at linux.alibaba.com> wrote:> The number of queues implemented by many virtio backends is limited, > especially some machines have a large number of CPUs. In this case, it > is often impossible to allocate a separate queue for XDP_TX. > > This patch allows XDP_TX to run by reuse the existing SQ with > __netif_tx_lock() hold when there are not enough queues. > > Signed-off-by: Xuan Zhuo <xuanzhuo at linux.alibaba.com> > Reviewed-by: Dust Li <dust.li at linux.alibaba.com> > --- > drivers/net/virtio_net.c | 48 ++++++++++++++++++++++++++++++++++++------------ > 1 file changed, 36 insertions(+), 12 deletions(-) > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c[...]> @@ -2416,12 +2441,8 @@ static int virtnet_xdp_set(struct net_device *dev, struct bpf_prog *prog, > xdp_qp = nr_cpu_ids; > > /* XDP requires extra queues for XDP_TX */ > - if (curr_qp + xdp_qp > vi->max_queue_pairs) { > - NL_SET_ERR_MSG_MOD(extack, "Too few free TX rings available"); > - netdev_warn(dev, "request %i queues but max is %i\n", > - curr_qp + xdp_qp, vi->max_queue_pairs); > - return -ENOMEM; > - } > + if (curr_qp + xdp_qp > vi->max_queue_pairs) > + xdp_qp = 0;I think we should keep a netdev_warn message, but as a warning (not error) that this will cause XDP_TX and XDP_REDIRECT to be slower on this device due to too few free TX rings available. In the future, we can mark a XDP features flag that this device is operating in a slower "locked" Tx mode.> > old_prog = rtnl_dereference(vi->rq[0].xdp_prog); > if (!prog && !old_prog)-- Best regards, Jesper Dangaard Brouer MSc.CS, Principal Kernel Engineer at Red Hat LinkedIn: http://www.linkedin.com/in/brouer