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tcp: add tp->dup_ack_counter

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In commit 86de5921a3 ("tcp: defer SACK compression after DupThresh")
I added a TCP_FASTRETRANS_THRESH bias to tp->compressed_ack in order
to enable sack compression only after 3 dupacks.

Since we plan to relax this rule for flows that involve
stacks not requiring this old rule, this patch adds
a distinct tp->dup_ack_counter.

This means the TCP_FASTRETRANS_THRESH value is now used
in a single location that a future patch can adjust:

	if (tp->dup_ack_counter < TCP_FASTRETRANS_THRESH) {
		tp->dup_ack_counter++;
		goto send_now;
	}

This patch also introduces tcp_sack_compress_send_ack()
helper to ease following patch comprehension.

This patch refines LINUX_MIB_TCPACKCOMPRESSED to not
count the acks that we had to send if the timer expires
or tcp_sack_compress_send_ack() is sending an ack.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@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
2020-04-30 10:35:41 -07:00
committed by David S. Miller
parent 3857c77624
commit 2b19585012
4 changed files with 38 additions and 13 deletions
Download Patch File Download Diff File Expand all files Collapse all files

8
net/ipv4/tcp_timer.c
View File

@@ -753,8 +753,14 @@ static enum hrtimer_restart tcp_compressed_ack_kick(struct hrtimer *timer)
bh_lock_sock(sk);
if (!sock_owned_by_user(sk)) {
if (tp->compressed_ack > TCP_FASTRETRANS_THRESH)
if (tp->compressed_ack) {
/* Since we have to send one ack finally,
* substract one from tp->compressed_ack to keep
* LINUX_MIB_TCPACKCOMPRESSED accurate.
*/
tp->compressed_ack--;
tcp_send_ack(sk);
}
} else {
if (!test_and_set_bit(TCP_DELACK_TIMER_DEFERRED,
&sk->sk_tsq_flags))