在 2021/4/16 下午5:16, Xuan Zhuo 写道:
In page_to_skb(), if we have enough tailroom to save skb_shared_info, we
can use build_skb to create skb directly. No need to alloc for
additional space. And it can save a 'frags slot', which is very friendly
to GRO.
Here, if the payload of the received package is too small (less than
GOOD_COPY_LEN), we still choose to copy it directly to the space got by
napi_alloc_skb. So we can reuse these pages.
Testing Machine:
The four queues of the network card are bound to the cpu1.
Test command:
for ((i=0;i<5;++i)); do sockperf tp --ip 192.168.122.64 -m 1000 -t 150& done
The size of the udp package is 1000, so in the case of this patch, there
will always be enough tailroom to use build_skb. The sent udp packet
will be discarded because there is no port to receive it. The irqsoftd
of the machine is 100%, we observe the received quantity displayed by
sar -n DEV 1:
no build_skb: 956864.00 rxpck/s
build_skb: 1158465.00 rxpck/s
I suggess to test the case of XDP_PASS in this case as well.
Signed-off-by: Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx>
Suggested-by: Jason Wang <jasowang@xxxxxxxxxx>
---
v3: fix the truesize when headroom > 0
v2: conflict resolution
drivers/net/virtio_net.c | 69 ++++++++++++++++++++++++++++------------
1 file changed, 48 insertions(+), 21 deletions(-)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 101659cd4b87..8cd76037c724 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -379,21 +379,17 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi,
struct receive_queue *rq,
struct page *page, unsigned int offset,
unsigned int len, unsigned int truesize,
- bool hdr_valid, unsigned int metasize)
+ bool hdr_valid, unsigned int metasize,
+ unsigned int headroom)
{
struct sk_buff *skb;
struct virtio_net_hdr_mrg_rxbuf *hdr;
unsigned int copy, hdr_len, hdr_padded_len;
- char *p;
+ int tailroom, shinfo_size;
+ char *p, *hdr_p;
p = page_address(page) + offset;
-
- /* copy small packet so we can reuse these pages for small data */
- skb = napi_alloc_skb(&rq->napi, GOOD_COPY_LEN);
- if (unlikely(!skb))
- return NULL;
-
- hdr = skb_vnet_hdr(skb);
+ hdr_p = p;
hdr_len = vi->hdr_len;
if (vi->mergeable_rx_bufs)
@@ -401,14 +397,38 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi,
else
hdr_padded_len = sizeof(struct padded_vnet_hdr);
- /* hdr_valid means no XDP, so we can copy the vnet header */
- if (hdr_valid)
- memcpy(hdr, p, hdr_len);
+ /* If headroom is not 0, there is an offset between the beginning of the
+ * data and the allocated space, otherwise the data and the allocated
+ * space are aligned.
+ */
+ if (headroom) {
+ /* The actual allocated space size is PAGE_SIZE. */
I think the comment in receive_mergeable() is better:
/* Buffers with headroom use PAGE_SIZE as alloc size,
* see add_recvbuf_mergeable() + get_mergeable_buf_len()
*/
+ truesize = PAGE_SIZE;
+ tailroom = truesize - len - offset;
+ } else {
+ tailroom = truesize - len;
+ }
len -= hdr_len;
offset += hdr_padded_len;
p += hdr_padded_len;
+ shinfo_size = SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
+
+ if (len > GOOD_COPY_LEN && tailroom >= shinfo_size) {
Any reason that you don't use build_skb() for len < GOOD_COPY_LEN?
Other looks good.
Thanks
+ skb = build_skb(p, truesize);
+ if (unlikely(!skb))
+ return NULL;
+
+ skb_put(skb, len);
+ goto ok;
+ }
+
+ /* copy small packet so we can reuse these pages for small data */
+ skb = napi_alloc_skb(&rq->napi, GOOD_COPY_LEN);
+ if (unlikely(!skb))
+ return NULL;
+
/* Copy all frame if it fits skb->head, otherwise
* we let virtio_net_hdr_to_skb() and GRO pull headers as needed.
*/
@@ -418,11 +438,6 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi,
copy = ETH_HLEN + metasize;
skb_put_data(skb, p, copy);
- if (metasize) {
- __skb_pull(skb, metasize);
- skb_metadata_set(skb, metasize);
- }
-
len -= copy;
offset += copy;
@@ -431,7 +446,7 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi,
skb_add_rx_frag(skb, 0, page, offset, len, truesize);
else
put_page(page);
- return skb;
+ goto ok;
}
/*
@@ -458,6 +473,18 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi,
if (page)
give_pages(rq, page);
+ok:
+ /* hdr_valid means no XDP, so we can copy the vnet header */
+ if (hdr_valid) {
+ hdr = skb_vnet_hdr(skb);
+ memcpy(hdr, hdr_p, hdr_len);
+ }
+
+ if (metasize) {
+ __skb_pull(skb, metasize);
+ skb_metadata_set(skb, metasize);
+ }
+
return skb;
}
@@ -808,7 +835,7 @@ static struct sk_buff *receive_big(struct net_device *dev,
{
struct page *page = buf;
struct sk_buff *skb =
- page_to_skb(vi, rq, page, 0, len, PAGE_SIZE, true, 0);
+ page_to_skb(vi, rq, page, 0, len, PAGE_SIZE, true, 0, 0);
stats->bytes += len - vi->hdr_len;
if (unlikely(!skb))
@@ -922,7 +949,7 @@ 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, false,
- metasize);
+ metasize, headroom);
return head_skb;
}
break;
@@ -980,7 +1007,7 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
}
head_skb = page_to_skb(vi, rq, page, offset, len, truesize, !xdp_prog,
- metasize);
+ metasize, headroom);
curr_skb = head_skb;
if (unlikely(!curr_skb))
--
2.31.0
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