diff mbox series

[net-next,3/3] tcp: remove obsolete check in __tcp_retransmit_skb()

Message ID 20210311203506.3450792-4-eric.dumazet@gmail.com
State New
Headers show
Series tcp: better deal with delayed TX completions | expand

Commit Message

Eric Dumazet March 11, 2021, 8:35 p.m. UTC 
From: Eric Dumazet <edumazet@google.com>

TSQ provides a nice way to avoid bufferbloat on individual socket,
including retransmit packets. We can get rid of the old
heuristic:

	/* Do not sent more than we queued. 1/4 is reserved for possible
	 * copying overhead: fragmentation, tunneling, mangling etc.
	 */
	if (refcount_read(&sk->sk_wmem_alloc) >
	    min_t(u32, sk->sk_wmem_queued + (sk->sk_wmem_queued >> 2),
		  sk->sk_sndbuf))
		return -EAGAIN;

This heuristic was giving false positives according to Jakub,
whenever TX completions are delayed above RTT. (Ack packets
are processed by TCP stack before clones are orphaned/freed)

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Jakub Kicinski <kuba@kernel.org>
Cc: Neal Cardwell <ncardwell@google.com>
Cc: Yuchung Cheng <ycheng@google.com>
---
 net/ipv4/tcp_output.c | 8 --------
 1 file changed, 8 deletions(-)
diff mbox series

Patch

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 0dbf208a4f2f17c630084e87f4a9a2ad0dc24168..bde781f46b41a5dd9eb8db3fb65b45d73e592b4b 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -3151,14 +3151,6 @@  int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs)
 	if (icsk->icsk_mtup.probe_size)
 		icsk->icsk_mtup.probe_size = 0;
 
-	/* Do not sent more than we queued. 1/4 is reserved for possible
-	 * copying overhead: fragmentation, tunneling, mangling etc.
-	 */
-	if (refcount_read(&sk->sk_wmem_alloc) >
-	    min_t(u32, sk->sk_wmem_queued + (sk->sk_wmem_queued >> 2),
-		  sk->sk_sndbuf))
-		return -EAGAIN;
-
 	if (skb_still_in_host_queue(sk, skb))
 		return -EBUSY;