From: Xuan Zhuo <xuanz...@linux.alibaba.com>
This patch is used to construct skb based on page to save memory copy
overhead.
This function is implemented based on IFF_TX_SKB_NO_LINEAR. Only the
network card priv_flags supports IFF_TX_SKB_NO_LINEAR will use page to
directly construct skb. If this feature is not supported, it is still
necessary to copy data to construct skb.
---------------- Performance Testing ------------
The test environment is Aliyun ECS server.
Test cmd:
```
xdpsock -i eth0 -t -S -s <msg size>
```
Test result data:
size 64 512 1024 1500
copy 1916747 1775988 1600203 1440054
page 1974058 1953655 1945463 1904478
percent 3.0% 10.0% 21.58% 32.3%
Signed-off-by: Xuan Zhuo <xuanz...@linux.alibaba.com>
Reviewed-by: Dust Li <dust...@linux.alibaba.com>
[ alobakin:
- expand subject to make it clearer;
- improve skb->truesize calculation;
- reserve some headroom in skb for drivers;
- tailroom is not needed as skb is non-linear ]
Signed-off-by: Alexander Lobakin <aloba...@pm.me>
---
net/xdp/xsk.c | 119 ++++++++++++++++++++++++++++++++++++++++----------
1 file changed, 95 insertions(+), 24 deletions(-)
diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index 143979ea4165..ff7bd06e1241 100644
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -445,6 +445,96 @@ static void xsk_destruct_skb(struct sk_buff *skb)
sock_wfree(skb);
}
+static struct sk_buff *xsk_build_skb_zerocopy(struct xdp_sock *xs,
+ struct xdp_desc *desc)
+{
+ struct xsk_buff_pool *pool = xs->pool;
+ u32 hr, len, offset, copy, copied;
+ struct sk_buff *skb;
+ struct page *page;
+ void *buffer;
+ int err, i;
+ u64 addr;
+
+ hr = max(NET_SKB_PAD, L1_CACHE_ALIGN(xs->dev->needed_headroom));
+
+ skb = sock_alloc_send_skb(&xs->sk, hr, 1, &err);
+ if (unlikely(!skb))
+ return ERR_PTR(err);
+
+ skb_reserve(skb, hr);
+
+ addr = desc->addr;
+ len = desc->len;
+
+ buffer = xsk_buff_raw_get_data(pool, addr);
+ offset = offset_in_page(buffer);
+ addr = buffer - pool->addrs;
+
+ for (copied = 0, i = 0; copied < len; i++) {
+ page = pool->umem->pgs[addr >> PAGE_SHIFT];
+ get_page(page);
+
+ copy = min_t(u32, PAGE_SIZE - offset, len - copied);
+ skb_fill_page_desc(skb, i, page, offset, copy);
+
+ copied += copy;
+ addr += copy;
+ offset = 0;
+ }
+
+ skb->len += len;
+ skb->data_len += len;
+ skb->truesize += pool->unaligned ? len : pool->chunk_size;
+
+ refcount_add(skb->truesize, &xs->sk.sk_wmem_alloc);
+
+ return skb;
+}
+
+static struct sk_buff *xsk_build_skb(struct xdp_sock *xs,
+ struct xdp_desc *desc)
+{
+ struct net_device *dev = xs->dev;
+ struct sk_buff *skb;
+
+ if (dev->priv_flags & IFF_TX_SKB_NO_LINEAR) {
+ skb = xsk_build_skb_zerocopy(xs, desc);
+ if (IS_ERR(skb))
+ return skb;
+ } else {
+ u32 hr, tr, len;
+ void *buffer;
+ int err;
+
+ hr = max(NET_SKB_PAD, L1_CACHE_ALIGN(dev->needed_headroom));
+ tr = dev->needed_tailroom;
+ len = desc->len;
+
+ skb = sock_alloc_send_skb(&xs->sk, hr + len + tr, 1, &err);
+ if (unlikely(!skb))
+ return ERR_PTR(err);
+
+ skb_reserve(skb, hr);
+ skb_put(skb, len);
+
+ buffer = xsk_buff_raw_get_data(xs->pool, desc->addr);
+ err = skb_store_bits(skb, 0, buffer, len);
+ if (unlikely(err)) {
+ kfree_skb(skb);
+ return ERR_PTR(err);
+ }
+ }
+
+ skb->dev = dev;
+ skb->priority = xs->sk.sk_priority;
+ skb->mark = xs->sk.sk_mark;
+ skb_shinfo(skb)->destructor_arg = (void *)(long)desc->addr;
+ skb->destructor = xsk_destruct_skb;
+
+ return skb;
+}
+
static int xsk_generic_xmit(struct sock *sk)
{
struct xdp_sock *xs = xdp_sk(sk);
@@ -454,56 +544,37 @@ static int xsk_generic_xmit(struct sock *sk)
struct sk_buff *skb;
unsigned long flags;
int err = 0;
- u32 hr, tr;
mutex_lock(&xs->mutex);
if (xs->queue_id >= xs->dev->real_num_tx_queues)
goto out;
- hr = max(NET_SKB_PAD, L1_CACHE_ALIGN(xs->dev->needed_headroom));
- tr = xs->dev->needed_tailroom;
-
while (xskq_cons_peek_desc(xs->tx, &desc, xs->pool)) {
- char *buffer;
- u64 addr;
- u32 len;
-
if (max_batch-- == 0) {
err = -EAGAIN;
goto out;
}
- len = desc.len;
- skb = sock_alloc_send_skb(sk, hr + len + tr, 1, &err);
- if (unlikely(!skb))
+ skb = xsk_build_skb(xs, &desc);
+ if (IS_ERR(skb)) {
+ err = PTR_ERR(skb);
goto out;
+ }
- skb_reserve(skb, hr);
- skb_put(skb, len);
-
- addr = desc.addr;
- buffer = xsk_buff_raw_get_data(xs->pool, addr);
- err = skb_store_bits(skb, 0, buffer, len);
/* This is the backpressure mechanism for the Tx path.
* Reserve space in the completion queue and only proceed
* if there is space in it. This avoids having to implement
* any buffering in the Tx path.
*/
spin_lock_irqsave(&xs->pool->cq_lock, flags);
- if (unlikely(err) || xskq_prod_reserve(xs->pool->cq)) {
+ if (xskq_prod_reserve(xs->pool->cq)) {
spin_unlock_irqrestore(&xs->pool->cq_lock, flags);
kfree_skb(skb);
goto out;
}
spin_unlock_irqrestore(&xs->pool->cq_lock, flags);
- skb->dev = xs->dev;
- skb->priority = sk->sk_priority;
- skb->mark = sk->sk_mark;
- skb_shinfo(skb)->destructor_arg = (void *)(long)desc.addr;
- skb->destructor = xsk_destruct_skb;
-
err = __dev_direct_xmit(skb, xs->queue_id);
if (err == NETDEV_TX_BUSY) {
/* Tell user-space to retry the send */
--
2.30.1
