On Wed, Jan 20, 2021 at 9:29 PM Alexander Lobakin [off-list ref] wrote:

From: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Date: Wed, 20 Jan 2021 16:30:56 +0800

quoted

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 <xuanzhuo@linux.alibaba.com>
Reviewed-by: Dust Li <dust.li@linux.alibaba.com>
---
 net/xdp/xsk.c | 104 ++++++++++++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 86 insertions(+), 18 deletions(-)

Now I like the result, thanks!

But Patchwork still display your series incorrectly (messages 0 and 1
are missing). I'm concerning maintainers may not take this in such
form. Try to pass the folder's name, not folder/*.patch to
git send-email when sending, and don't use --in-reply-to when sending
a new iteration.

Xuan,

Please make the new submission of the patch set a v3 even though you
did not change the code. Just so we can clearly see it is the new
submission.

quoted

diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index 8037b04..40bac11 100644
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c

@@ -430,6 +430,87 @@ 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)
+{
+     u32 len, offset, copy, copied;
+     struct sk_buff *skb;
+     struct page *page;
+     void *buffer;
+     int err, i;
+     u64 addr;
+
+     skb = sock_alloc_send_skb(&xs->sk, 0, 1, &err);
+     if (unlikely(!skb))
+             return ERR_PTR(err);
+
+     addr = desc->addr;
+     len = desc->len;
+
+     buffer = xsk_buff_raw_get_data(xs->pool, addr);
+     offset = offset_in_page(buffer);
+     addr = buffer - xs->pool->addrs;
+
+     for (copied = 0, i = 0; copied < len; i++) {
+             page = xs->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 += len;
+
+     refcount_add(len, &xs->sk.sk_wmem_alloc);
+
+     return skb;
+}
+
+static struct sk_buff *xsk_build_skb(struct xdp_sock *xs,
+                                  struct xdp_desc *desc)
+{
+     struct sk_buff *skb = NULL;
+
+     if (xs->dev->priv_flags & IFF_TX_SKB_NO_LINEAR) {
+             skb = xsk_build_skb_zerocopy(xs, desc);
+             if (IS_ERR(skb))
+                     return skb;
+     } else {
+             void *buffer;
+             u32 len;
+             int err;
+
+             len = desc->len;
+             skb = sock_alloc_send_skb(&xs->sk, len, 1, &err);
+             if (unlikely(!skb))
+                     return ERR_PTR(err);
+
+             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 = xs->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);

@@ -446,43 +527,30 @@ static int xsk_generic_xmit(struct sock *sk)
              goto out;

      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, len, 1, &err);
-             if (unlikely(!skb))
+             skb = xsk_build_skb(xs, &desc);
+             if (IS_ERR(skb)) {
+                     err = PTR_ERR(skb);
                      goto out;
+             }

-             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 */
--

1.8.3.1

Al