Commit 15e6ca97 authored by Paolo Abeni's avatar Paolo Abeni Committed by Jakub Kicinski
Browse files

mptcp: let MPTCP create max size skbs 



Currently the xmit path of the MPTCP protocol creates smaller-
than-max-size skbs, which is suboptimal for the performances.

There are a few things to improve:
- when coalescing to an existing skb, must clear the PUSH flag
- tcp_build_frag() expect the available space as an argument.
  When coalescing is enable MPTCP already subtracted the
  to-be-coalesced skb len. We must increment said argument
  accordingly.

Before:
./use_mptcp.sh netperf -H 127.0.0.1 -t TCP_STREAM
[...]
131072  16384  16384    30.00    24414.86

After:
./use_mptcp.sh netperf -H 127.0.0.1 -t TCP_STREAM
[...]
131072  16384  16384    30.05    28357.69

Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
Signed-off-by: default avatarMat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 1bc7327b

net/mptcp/protocol.c

+9 −5
Original line number Diff line number Diff line
@@ -1256,6 +1256,7 @@ static int mptcp_sendmsg_frag(struct sock *sk, struct sock *ssk, 
	struct mptcp_ext *mpext = NULL;

	struct sk_buff *skb, *tail;

	bool can_collapse = false;

	int size_bias = 0;

	int avail_size;

	size_t ret = 0;
@@ -1277,11 +1278,13 @@ static int mptcp_sendmsg_frag(struct sock *sk, struct sock *ssk, 
		mpext = skb_ext_find(skb, SKB_EXT_MPTCP);

		can_collapse = (info->size_goal - skb->len > 0) &&

			 mptcp_skb_can_collapse_to(data_seq, skb, mpext);

		if (!can_collapse)

		if (!can_collapse) {

			TCP_SKB_CB(skb)->eor = 1;

		else

		} else {

			size_bias = skb->len;

			avail_size = info->size_goal - skb->len;

		}

	}



	/* Zero window and all data acked? Probe. */

	avail_size = mptcp_check_allowed_size(msk, data_seq, avail_size);
@@ -1300,8 +1303,8 @@ static int mptcp_sendmsg_frag(struct sock *sk, struct sock *ssk, 
		return 0;



	ret = info->limit - info->sent;

	tail = tcp_build_frag(ssk, avail_size, info->flags, dfrag->page,

			      dfrag->offset + info->sent, &ret);

	tail = tcp_build_frag(ssk, avail_size + size_bias, info->flags,

			      dfrag->page, dfrag->offset + info->sent, &ret);

	if (!tail) {

		tcp_remove_empty_skb(sk, tcp_write_queue_tail(ssk));

		return -ENOMEM;
@@ -1310,8 +1313,9 @@ static int mptcp_sendmsg_frag(struct sock *sk, struct sock *ssk, 
	/* if the tail skb is still the cached one, collapsing really happened.

	 */

	if (skb == tail) {

		WARN_ON_ONCE(!can_collapse);

		TCP_SKB_CB(tail)->tcp_flags &= ~TCPHDR_PSH;

		mpext->data_len += ret;

		WARN_ON_ONCE(!can_collapse);

		WARN_ON_ONCE(zero_window_probe);

		goto out;

	}

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