diff options
| author | Eric Dumazet <edumazet@google.com> | 2013-08-05 20:05:12 -0700 |
|---|---|---|
| committer | Willy Tarreau <w@1wt.eu> | 2014-05-19 07:53:52 +0200 |
| commit | 91b5dbd86fedea48e1808df5496617a87b6f320c (patch) | |
| tree | 8d41fbc44c3c678e2cfd63e1fed8315fbed6e6a4 | |
| parent | eedcafdc0abf54a33b2c021b74c30c7a96eee050 (diff) | |
tcp: cubic: fix bug in bictcp_acked()
[ Upstream commit cd6b423afd3c08b27e1fed52db828ade0addbc6b ]
While investigating about strange increase of retransmit rates
on hosts ~24 days after boot, Van found hystart was disabled
if ca->epoch_start was 0, as following condition is true
when tcp_time_stamp high order bit is set.
(s32)(tcp_time_stamp - ca->epoch_start) < HZ
Quoting Van :
At initialization & after every loss ca->epoch_start is set to zero so
I believe that the above line will turn off hystart as soon as the 2^31
bit is set in tcp_time_stamp & hystart will stay off for 24 days.
I think we've observed that cubic's restart is too aggressive without
hystart so this might account for the higher drop rate we observe.
Diagnosed-by: Van Jacobson <vanj@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Neal Cardwell <ncardwell@google.com>
Cc: Yuchung Cheng <ycheng@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Willy Tarreau <w@1wt.eu>
| -rw-r--r-- | net/ipv4/tcp_cubic.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/net/ipv4/tcp_cubic.c b/net/ipv4/tcp_cubic.c index 71d5f2f29fa6..0d41c2657f45 100644 --- a/net/ipv4/tcp_cubic.c +++ b/net/ipv4/tcp_cubic.c @@ -388,7 +388,7 @@ static void bictcp_acked(struct sock *sk, u32 cnt, s32 rtt_us) return; /* Discard delay samples right after fast recovery */ - if ((s32)(tcp_time_stamp - ca->epoch_start) < HZ) + if (ca->epoch_start && (s32)(tcp_time_stamp - ca->epoch_start) < HZ) return; delay = usecs_to_jiffies(rtt_us) << 3; |