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bpf/xdp: non-map redirect can avoid calling ndo_xdp_flush 

This is the first real user of the XDP_XMIT_FLUSH flag.

As pointed out many times, XDP_REDIRECT without using BPF maps is
significant slower than the map variant.  This is primary due to the
lack of bulking, as the ndo_xdp_flush operation is required after each
frame (to avoid frames hanging on the egress device).

It is still possible to optimize this case.  Instead of invoking two
NDO indirect calls, which are very expensive with CONFIG_RETPOLINE,
instead instruct ndo_xdp_xmit to flush via XDP_XMIT_FLUSH flag.

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Jesper Dangaard Brouer 2018-05-31 11:00:18 +02:00 committed by Alexei Starovoitov
parent 73de5717eb
commit 1e67575a58
1 changed files with 1 additions and 2 deletions
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3
net/core/filter.c
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@ -3056,10 +3056,9 @@ static int __bpf_tx_xdp(struct net_device *dev,
if (unlikely(!xdpf))
return -EOVERFLOW;
sent = dev->netdev_ops->ndo_xdp_xmit(dev, 1, &xdpf, 0);
sent = dev->netdev_ops->ndo_xdp_xmit(dev, 1, &xdpf, XDP_XMIT_FLUSH);
if (sent <= 0)
return sent;
dev->netdev_ops->ndo_xdp_flush(dev);
return 0;
}