[PATCH bpf-next 1/2] xsk: speed-up generic full-copy xmit

From: Alexander Lobakin
Date: Tue Mar 30 2021 - 19:17:00 EST


There are a few moments that are known for sure at the moment of
copying:
- allocated skb is fully linear;
- its linear space is long enough to hold the full buffer data.

So, the out-of-line skb_put(), skb_store_bits() and the check for
a retcode can be replaced with plain memcpy(__skb_put()) with
no loss.
Also align memcpy()'s len to sizeof(long) to improve its performance.

Signed-off-by: Alexander Lobakin <alobakin@xxxxx>
---
net/xdp/xsk.c | 7 +------
1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index a71ed664da0a..41f8f21b3348 100644
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -517,14 +517,9 @@ static struct sk_buff *xsk_build_skb(struct xdp_sock *xs,
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);
- }
+ memcpy(__skb_put(skb, len), buffer, ALIGN(len, sizeof(long)));
}

skb->dev = dev;
--
2.31.1