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Subject[PATCH 1/2] virtio_net: Recycle some more rx buffer pages
Date
Each time we re-fill the recv queue with buffers, we allocate
one too many skbs and free it again when adding fails. We should
recycle the pages allocated in this case.

A previous version of this patch made trim_pages() trim trailing
unused pages from skbs with some paged data, but this actually
caused a barely measurable slowdown.

Signed-off-by: Mark McLoughlin <markmc@redhat.com>
---
drivers/net/virtio_net.c | 21 +++++++++++++--------
1 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 0196a0d..985271a 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -82,6 +82,16 @@ static void give_a_page(struct virtnet_info *vi, struct page *page)
vi->pages = page;
}

+static void trim_pages(struct virtnet_info *vi, struct sk_buff *skb)
+{
+ unsigned int i;
+
+ for (i = 0; i < skb_shinfo(skb)->nr_frags; i++)
+ give_a_page(vi, skb_shinfo(skb)->frags[i].page);
+ skb_shinfo(skb)->nr_frags = 0;
+ skb->data_len = 0;
+}
+
static struct page *get_a_page(struct virtnet_info *vi, gfp_t gfp_mask)
{
struct page *p = vi->pages;
@@ -121,14 +131,8 @@ static void receive_skb(struct net_device *dev, struct sk_buff *skb,
}
len -= sizeof(struct virtio_net_hdr);

- if (len <= MAX_PACKET_LEN) {
- unsigned int i;
-
- for (i = 0; i < skb_shinfo(skb)->nr_frags; i++)
- give_a_page(dev->priv, skb_shinfo(skb)->frags[i].page);
- skb->data_len = 0;
- skb_shinfo(skb)->nr_frags = 0;
- }
+ if (len <= MAX_PACKET_LEN)
+ trim_pages(dev->priv, skb);

err = pskb_trim(skb, len);
if (err) {
@@ -232,6 +236,7 @@ static void try_fill_recv(struct virtnet_info *vi)
err = vi->rvq->vq_ops->add_buf(vi->rvq, sg, 0, num, skb);
if (err) {
skb_unlink(skb, &vi->recv);
+ trim_pages(vi, skb);
kfree_skb(skb);
break;
}
--
1.5.4.3


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