PATCH v2 3/4] Defer skb allocation -- new recvbuf alloc & receive calls

Shirley Ma
2009-12-11T12:46:49Z

Signed-off-by: Shirley Ma <xma@us.ibm.com>
-------------

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 100b4b9..dde8060 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -203,6 +203,73 @@ static struct sk_buff *skb_goodcopy(struct virtnet_info *vi, struct page **page,
return skb;
}

+static struct sk_buff *receive_big(struct virtnet_info *vi, struct page *page,
+ unsigned int len)
+{
+ struct sk_buff *skb;
+
+ skb = skb_goodcopy(vi, &page, &len);
+ if (unlikely(!skb))
+ return NULL;
+
+ while (len > 0) {
+ len = skb_set_frag(skb, page, 0, len);
+ page = (struct page *)page->private;
+ }
+
+ if (page)
+ give_pages(vi, page);
+
+ return skb;
+}
+
+static struct sk_buff *receive_mergeable(struct virtnet_info *vi,
+ struct page *page, unsigned int len)
+{
+ struct sk_buff *skb;
+ struct skb_vnet_hdr *hdr;
+ int num_buf, i;
+
+ if (len > PAGE_SIZE)
+ len = PAGE_SIZE;
+
+ skb = skb_goodcopy(vi, &page, &len);
+
+ if (unlikely(!skb))
+ return NULL;
+
+ hdr = skb_vnet_hdr(skb);
+ num_buf = hdr->mhdr.num_buffers;
+ while (--num_buf) {
+ struct page *page;
+
+ i = skb_shinfo(skb)->nr_frags;
+ if (i >= MAX_SKB_FRAGS) {
+ pr_debug("%s: packet too long %d\n", skb->dev->name,
+ len);
+ skb->dev->stats.rx_length_errors++;
+ return skb;
+ }
+
+ page = vi->rvq->vq_ops->get_buf(vi->rvq, &len);
+ if (!page) {
+ pr_debug("%s: rx error: %d buffers missing\n",
+ skb->dev->name, hdr->mhdr.num_buffers);
+ skb->dev->stats.rx_length_errors++;
+ return skb;
+ }
+
+ if (len > PAGE_SIZE)
+ len = PAGE_SIZE;
+
+ skb_set_frag(skb, page, 0, len);
+
+ vi->num--;
+ }
+
+ return skb;
+}
+
static void receive_skb(struct net_device *dev, struct sk_buff *skb,
unsigned len)
{
@@ -356,6 +423,103 @@ drop:
dev_kfree_skb(skb);
}

+static int add_recvbuf_small(struct virtnet_info *vi, gfp_t gfp, bool *oom)
+{
+ struct sk_buff *skb;
+ struct skb_vnet_hdr *hdr;
+ struct scatterlist sg[2];
+ int err = 0;
+
+ skb = netdev_alloc_skb(vi->dev, MAX_PACKET_LEN + NET_IP_ALIGN);
+ if (unlikely(!skb)) {
+ *oom = true;
+ return err;
+ }
+
+ skb_reserve(skb, NET_IP_ALIGN);
+ skb_put(skb, MAX_PACKET_LEN);
+
+ hdr = skb_vnet_hdr(skb);
+ sg_set_buf(sg, &hdr->hdr, sizeof(hdr->hdr));
+
+ skb_to_sgvec(skb, sg+1, 0, skb->len);
+
+ err = vi->rvq->vq_ops->add_buf(vi->rvq, sg, 0, 2, skb);
+ if (err < 0)
+ kfree_skb(skb);
+ else
+ skb_queue_head(&vi->recv, skb);
+
+ return err;
+}
+
+static int add_recvbuf_big(struct virtnet_info *vi, gfp_t gfp, bool *oom)
+{
+ struct scatterlist sg[2 + MAX_SKB_FRAGS];
+ int total = MAX_SKB_FRAGS + 2;
+ char *p;
+ int err = 0;
+ int i, offset;
+ struct page *first = NULL;
+ struct page *page;
+ /* share one page between virtio_net header and data */
+ struct padded_vnet_hdr {
+ struct virtio_net_hdr hdr;
+ /* This padding makes our data 16 byte aligned */
+ char padding[6];
+ };
+
+ offset = sizeof(struct padded_vnet_hdr);
+
+ for (i = total - 1; i > 0; i--) {
+ page = get_a_page(vi, gfp);
+ if (!page) {
+ if (first)
+ give_pages(vi, first);
+ *oom = true;
+ break;
+ }
+
+ p = page_address(page);
+ page->private = (unsigned long)first;
+ first = page;
+
+ /* allocate MAX_SKB_FRAGS + 1 pages for big packets */
+ if (i == 1) {
+ sg_set_buf(&sg[i-1], p, sizeof(struct virtio_net_hdr));
+ sg_set_buf(&sg[i], p + offset, PAGE_SIZE - offset);
+ err = vi->rvq->vq_ops->add_buf(vi->rvq, sg, 0, total,
+ first);
+ if (err < 0)
+ give_pages(vi, first);
+ } else
+ sg_set_buf(&sg[i], p, PAGE_SIZE);
+ }
+
+ return err;
+}
+
+static int add_recvbuf_mergeable(struct virtnet_info *vi, gfp_t gfp, bool *oom)
+{
+ struct page *page;
+ struct scatterlist sg;
+ int err = 0;
+
+ page = get_a_page(vi, gfp);
+ if (!page) {
+ *oom = true;
+ return err;
+ }
+
+ sg_init_one(&sg, page_address(page), PAGE_SIZE);
+
+ err = vi->rvq->vq_ops->add_buf(vi->rvq, &sg, 0, 1, page);
+ if (err < 0)
+ give_pages(vi, page);
+
+ return err;
+}
+
static bool try_fill_recv_maxbufs(struct virtnet_info *vi, gfp_t gfp)
{
struct sk_buff *skb;