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mptcp: let MPTCP create max size skbs

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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: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Paolo Abeni 2020-12-10 14:25:06 -08:00 committed by Jakub Kicinski
parent 1bc7327b5f
commit 15e6ca974b
1 changed files with 9 additions and 5 deletions
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14
net/mptcp/protocol.c
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@ -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;
@ -1277,10 +1278,12 @@ 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. */
@ -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;
}