From 2b195850128f5bafde177b12489d9fa27962cc1e Mon Sep 17 00:00:00 2001
From: Eric Dumazet <edumazet@google.com>
Date: Thu, 30 Apr 2020 10:35:41 -0700
Subject: tcp: add tp->dup_ack_counter
In commit 86de5921a3d5 ("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>
---
net/ipv4/tcp_timer.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
(limited to 'net/ipv4/tcp_timer.c')
diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index c3f26dcd6704..ada046f425d2 100644
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -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))
--
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