Re: [PATCH v2 net-next] virtio-net: support XDP_TX when not more queues
From: Jesper Dangaard Brouer <hidden>
Date: 2021-02-25 17:04:47
Also in:
bpf, netdev
On Thu, 25 Feb 2021 16:22:29 +0800 Xuan Zhuo [off-list ref] wrote:
quoted hunk
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@linux.alibaba.com> Reviewed-by: Dust Li <dust.li@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
[...]
quoted hunk
@@ -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 _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization