From: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
To: netdev@vger.kernel.org
Cc: ast@kernel.org, daniel@iogearbox.net, alan.maguire@oracle.com,
Willem de Bruijn <willemb@google.com>
Subject: [PATCH bpf-next v2 01/13] bpf: in bpf_skb_adjust_room avoid copy in tx fast path
Date: Fri, 22 Mar 2019 11:14:52 -0400 [thread overview]
Message-ID: <20190322151504.89983-2-willemdebruijn.kernel@gmail.com> (raw)
In-Reply-To: <20190322151504.89983-1-willemdebruijn.kernel@gmail.com>
From: Willem de Bruijn <willemb@google.com>
bpf_skb_adjust_room calls skb_cow on grow.
This expensive operation can be avoided in the fast path when the only
other clone has released the header. This is the common case for TCP,
where one headerless clone is kept on the retransmit queue.
It is safe to do so even when touching the gso fields in skb_shinfo.
Regular tunnel encap with iptunnel_handle_offloads takes the same
optimization.
The tcp stack unclones in the unlikely case that it accesses these
fields through headerless clones packets on the retransmit queue (see
__tcp_retransmit_skb).
If any other clones are present, e.g., from packet sockets,
skb_cow_head returns the same value as skb_cow().
Signed-off-by: Willem de Bruijn <willemb@google.com>
---
net/core/filter.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/core/filter.c b/net/core/filter.c
index d2511fe46db3..d21e1acdde29 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -2971,7 +2971,7 @@ static int bpf_skb_net_grow(struct sk_buff *skb, u32 len_diff)
if (skb_is_gso(skb) && !skb_is_gso_tcp(skb))
return -ENOTSUPP;
- ret = skb_cow(skb, len_diff);
+ ret = skb_cow_head(skb, len_diff);
if (unlikely(ret < 0))
return ret;
--
2.21.0.392.gf8f6787159e-goog
next prev parent reply other threads:[~2019-03-22 15:15 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-22 15:14 [PATCH bpf-next v2 00/13] bpf tc tunneling Willem de Bruijn
2019-03-22 15:14 ` Willem de Bruijn [this message]
2019-03-22 15:14 ` [PATCH bpf-next v2 02/13] selftests/bpf: bpf tunnel encap test Willem de Bruijn
2019-03-22 15:14 ` [PATCH bpf-next v2 03/13] selftests/bpf: expand bpf tunnel test with decap Willem de Bruijn
2019-03-22 15:14 ` [PATCH bpf-next v2 04/13] selftests/bpf: expand bpf tunnel test to ipv6 Willem de Bruijn
2019-03-22 15:14 ` [PATCH bpf-next v2 05/13] selftests/bpf: extend bpf tunnel test with gre Willem de Bruijn
2019-03-22 15:14 ` [PATCH bpf-next v2 06/13] selftests/bpf: extend bpf tunnel test with tso Willem de Bruijn
2019-03-22 15:14 ` [PATCH bpf-next v2 07/13] bpf: add bpf_skb_adjust_room mode BPF_ADJ_ROOM_MAC Willem de Bruijn
2019-03-22 15:14 ` [PATCH bpf-next v2 08/13] bpf: add bpf_skb_adjust_room flag BPF_F_ADJ_ROOM_FIXED_GSO Willem de Bruijn
2019-03-22 15:15 ` [PATCH bpf-next v2 09/13] bpf: add bpf_skb_adjust_room encap flags Willem de Bruijn
2019-03-22 15:44 ` Alexei Starovoitov
2019-03-22 15:47 ` Willem de Bruijn
2019-03-22 16:11 ` Alexei Starovoitov
2019-03-22 16:31 ` Willem de Bruijn
2019-03-22 15:15 ` [PATCH bpf-next v2 10/13] bpf: Sync bpf.h to tools Willem de Bruijn
2019-03-22 15:15 ` [PATCH bpf-next v2 11/13] selftests/bpf: convert bpf tunnel test to BPF_ADJ_ROOM_MAC Willem de Bruijn
2019-03-22 15:15 ` [PATCH bpf-next v2 12/13] selftests/bpf: convert bpf tunnel test to BPF_F_ADJ_ROOM_FIXED_GSO Willem de Bruijn
2019-03-22 15:15 ` [PATCH bpf-next v2 13/13] selftests/bpf: convert bpf tunnel test to encap modes Willem de Bruijn
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