linux-kernel - [PATCH net-next 2/3] virtio-net: add packet len average only when needed during XDP

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Date:   Tue, 19 Sep 2017 17:42:42 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     mst@...hat.com, jasowang@...hat.com,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     John Fastabend <john.fastabend@...il.com>
Subject: [PATCH net-next 2/3] virtio-net: add packet len average only when needed during XDP

There's no need to add packet len average in the case of XDP_PASS
since it will be done soon after skb is created.

Cc: John Fastabend <john.fastabend@...il.com>
Signed-off-by: Jason Wang <jasowang@...hat.com>
---
 drivers/net/virtio_net.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index a0ef4b0..db5924c 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -656,6 +656,9 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
 		xdp.data_end = xdp.data + (len - vi->hdr_len);
 		act = bpf_prog_run_xdp(xdp_prog, &xdp);
 
+		if (act != XDP_PASS)
+			ewma_pkt_len_add(&rq->mrg_avg_pkt_len, len);
+
 		switch (act) {
 		case XDP_PASS:
 			/* recalculate offset to account for any header
@@ -671,14 +674,12 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
 				put_page(page);
 				head_skb = page_to_skb(vi, rq, xdp_page,
 						       offset, len, PAGE_SIZE);
-				ewma_pkt_len_add(&rq->mrg_avg_pkt_len, len);
 				return head_skb;
 			}
 			break;
 		case XDP_TX:
 			if (unlikely(!virtnet_xdp_xmit(vi, &xdp)))
 				trace_xdp_exception(vi->dev, xdp_prog, act);
-			ewma_pkt_len_add(&rq->mrg_avg_pkt_len, len);
 			if (unlikely(xdp_page != page))
 				goto err_xdp;
 			rcu_read_unlock();
@@ -690,7 +691,6 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
 		case XDP_DROP:
 			if (unlikely(xdp_page != page))
 				__free_pages(xdp_page, 0);
-			ewma_pkt_len_add(&rq->mrg_avg_pkt_len, len);
 			goto err_xdp;
 		}
 	}
-- 
2.7.4