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tcp: use TCP_SKB_CB(skb)->tcp_flags in input path

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Input path of TCP do not currently uses TCP_SKB_CB(skb)->tcp_flags,
which is only used in output path.

tcp_recvmsg(), looks at tcp_hdr(skb)->syn for every skb found in receive queue,
and its unfortunate because this bit is located in a cache line right before
the payload.

We can simplify TCP by copying tcp flags into TCP_SKB_CB(skb)->tcp_flags.

This patch does so, and avoids the cache line miss in tcp_recvmsg()

Following patches will
- allow a segment with FIN being coalesced in tcp_try_coalesce()
- simplify tcp_collapse() by not copying the headers.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet
2014-09-15 04:19:51 -07:00
committed by David S. Miller
parent 13bb5180e8
commit e11ecddf51
4 changed files with 17 additions and 13 deletions
Download Patch File Download Diff File Expand all files Collapse all files

18
net/ipv4/tcp.c
View File

@@ -1510,9 +1510,9 @@ static struct sk_buff *tcp_recv_skb(struct sock *sk, u32 seq, u32 *off)
while ((skb = skb_peek(&sk->sk_receive_queue)) != NULL) {
offset = seq - TCP_SKB_CB(skb)->seq;
if (tcp_hdr(skb)->syn)
if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
offset--;
if (offset < skb->len || tcp_hdr(skb)->fin) {
if (offset < skb->len || (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)) {
*off = offset;
return skb;
}
@@ -1585,7 +1585,7 @@ int tcp_read_sock(struct sock *sk, read_descriptor_t *desc,
if (offset + 1 != skb->len)
continue;
}
if (tcp_hdr(skb)->fin) {
if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) {
sk_eat_skb(sk, skb, false);
++seq;
break;
@@ -1722,11 +1722,11 @@ int tcp_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
break;
offset = *seq - TCP_SKB_CB(skb)->seq;
if (tcp_hdr(skb)->syn)
if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
offset--;
if (offset < skb->len)
goto found_ok_skb;
if (tcp_hdr(skb)->fin)
if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
goto found_fin_ok;
WARN(!(flags & MSG_PEEK),
"recvmsg bug 2: copied %X seq %X rcvnxt %X fl %X\n",
@@ -1959,7 +1959,7 @@ skip_copy:
if (used + offset < skb->len)
continue;
if (tcp_hdr(skb)->fin)
if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
goto found_fin_ok;
if (!(flags & MSG_PEEK)) {
sk_eat_skb(sk, skb, copied_early);
@@ -2160,8 +2160,10 @@ void tcp_close(struct sock *sk, long timeout)
* reader process may not have drained the data yet!
*/
while ((skb = __skb_dequeue(&sk->sk_receive_queue)) != NULL) {
u32 len = TCP_SKB_CB(skb)->end_seq - TCP_SKB_CB(skb)->seq -
tcp_hdr(skb)->fin;
u32 len = TCP_SKB_CB(skb)->end_seq - TCP_SKB_CB(skb)->seq;
if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)
len--;
data_was_unread += len;
__kfree_skb(skb);
}