From ac3959fd0dcc0e49298ea5cadfe257db0e58ef8b Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Thu, 11 Mar 2021 12:35:06 -0800 Subject: [PATCH] tcp: remove obsolete check in __tcp_retransmit_skb() 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 Reported-by: Jakub Kicinski Cc: Neal Cardwell Cc: Yuchung Cheng Signed-off-by: David S. Miller --- net/ipv4/tcp_output.c | 8 -------- 1 file changed, 8 deletions(-) diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 0dbf208a4f2f..bde781f46b41 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; -- 2.34.1