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Date:   Tue, 30 Mar 2021 23:15:52 +0000
To:     Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>
From:   Alexander Lobakin <alobakin@pm.me>
Cc:     Xuan Zhuo <xuanzhuo@linux.alibaba.com>,
        =?utf-8?Q?Bj=C3=B6rn_T=C3=B6pel?= <bjorn@kernel.org>,
        Magnus Karlsson <magnus.karlsson@intel.com>,
        Jonathan Lemon <jonathan.lemon@gmail.com>,
        "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Jesper Dangaard Brouer <hawk@kernel.org>,
        John Fastabend <john.fastabend@gmail.com>,
        Andrii Nakryiko <andrii@kernel.org>,
        Martin KaFai Lau <kafai@fb.com>,
        Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
        KP Singh <kpsingh@kernel.org>,
        Alexander Lobakin <alobakin@pm.me>, netdev@vger.kernel.org,
        bpf@vger.kernel.org, linux-kernel@vger.kernel.org
Reply-To: Alexander Lobakin <alobakin@pm.me>
Subject: [PATCH bpf-next 1/2] xsk: speed-up generic full-copy xmit
Message-ID: <20210330231528.546284-2-alobakin@pm.me>
In-Reply-To: <20210330231528.546284-1-alobakin@pm.me>
References: <20210330231528.546284-1-alobakin@pm.me>
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Precedence: bulk

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@pm.me>
---
 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,
 =09=09=09return ERR_PTR(err);

 =09=09skb_reserve(skb, hr);
-=09=09skb_put(skb, len);

 =09=09buffer =3D xsk_buff_raw_get_data(xs->pool, desc->addr);
-=09=09err =3D skb_store_bits(skb, 0, buffer, len);
-=09=09if (unlikely(err)) {
-=09=09=09kfree_skb(skb);
-=09=09=09return ERR_PTR(err);
-=09=09}
+=09=09memcpy(__skb_put(skb, len), buffer, ALIGN(len, sizeof(long)));
 =09}

 =09skb->dev =3D dev;
--
2.31.1