| From | Willy Tarreau <> | Subject | [PATCH 3.10 083/139] tcp: when rearming RTO, if RTO time is in past then fire RTO ASAP | Date | Wed, 1 Nov 2017 22:26:24 +0100 |
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From: Neal Cardwell <ncardwell@google.com>
commit cdbeb633ca71a02b7b63bfeb94994bf4e1a0b894 upstream.
In some situations tcp_send_loss_probe() can realize that it's unable to send a loss probe (TLP), and falls back to calling tcp_rearm_rto() to schedule an RTO timer. In such cases, sometimes tcp_rearm_rto() realizes that the RTO was eligible to fire immediately or at some point in the past (delta_us <= 0). Previously in such cases tcp_rearm_rto() was scheduling such "overdue" RTOs to happen at now + icsk_rto, which caused needless delays of hundreds of milliseconds (and non-linear behavior that made reproducible testing difficult). This commit changes the logic to schedule "overdue" RTOs ASAP, rather than at now + icsk_rto.
Fixes: 6ba8a3b19e76 ("tcp: Tail loss probe (TLP)") Suggested-by: Yuchung Cheng <ycheng@google.com> Signed-off-by: Neal Cardwell <ncardwell@google.com> Signed-off-by: Yuchung Cheng <ycheng@google.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net> [wt: no need for usec_to_jiffies conversion in 3.10]
Signed-off-by: Willy Tarreau <w@1wt.eu> --- net/ipv4/tcp_input.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 828835c..85dd09b 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -2977,8 +2977,7 @@ void tcp_rearm_rto(struct sock *sk) /* delta may not be positive if the socket is locked * when the retrans timer fires and is rescheduled. */ - if (delta > 0) - rto = delta; + rto = max_t(int, delta, 1); } inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, rto, TCP_RTO_MAX); -- 2.8.0.rc2.1.gbe9624a
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