From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
stable@vger.kernel.org, Eric Dumazet <edumazet@google.com>,
Neal Cardwell <ncardwell@google.com>,
Yuchung Cheng <ycheng@google.com>,
"David S. Miller" <davem@davemloft.net>
Subject: [ 05/19] tcp: cubic: fix bug in bictcp_acked()
Date: Thu, 12 Sep 2013 10:26:14 -0700 [thread overview]
Message-ID: <20130912172524.755689263@linuxfoundation.org> (raw)
In-Reply-To: <20130912172524.135620246@linuxfoundation.org>
3.0-stable review patch. If anyone has any objections, please let me know.
------------------
From: Eric Dumazet <edumazet@google.com>
[ 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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/ipv4/tcp_cubic.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/net/ipv4/tcp_cubic.c
+++ b/net/ipv4/tcp_cubic.c
@@ -414,7 +414,7 @@ static void bictcp_acked(struct sock *sk
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 = (rtt_us << 3) / USEC_PER_MSEC;
next prev parent reply other threads:[~2013-09-12 17:26 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-12 17:26 [ 00/19] 3.0.96-stable review Greg Kroah-Hartman
2013-09-12 17:26 ` [ 01/19] htb: fix sign extension bug Greg Kroah-Hartman
2013-09-12 17:26 ` [ 02/19] net: check net.core.somaxconn sysctl values Greg Kroah-Hartman
2013-09-12 17:26 ` [ 03/19] fib_trie: remove potential out of bound access Greg Kroah-Hartman
2013-09-12 17:26 ` [ 04/19] tcp: cubic: fix overflow error in bictcp_update() Greg Kroah-Hartman
2013-09-12 17:26 ` Greg Kroah-Hartman [this message]
2013-09-12 17:26 ` [ 06/19] ipv6: dont stop backtracking in fib6_lookup_1 if subtree does not match Greg Kroah-Hartman
2013-09-12 17:26 ` [ 07/19] tun: signedness bug in tun_get_user() Greg Kroah-Hartman
2013-09-12 17:26 ` [ 08/19] ipv6: remove max_addresses check from ipv6_create_tempaddr Greg Kroah-Hartman
2013-09-12 17:26 ` [ 09/19] ipv6: drop packets with multiple fragmentation headers Greg Kroah-Hartman
2013-09-12 17:26 ` [ 10/19] ipv6: Dont depend on per socket memory for neighbour discovery messages Greg Kroah-Hartman
2013-09-12 17:26 ` [ 11/19] net: bridge: convert MLDv2 Query MRC into msecs_to_jiffies for max_delay Greg Kroah-Hartman
2013-09-12 17:26 ` [ 12/19] ICMPv6: treat dest unreachable codes 5 and 6 as EACCES, not EPROTO Greg Kroah-Hartman
2013-09-12 17:26 ` [ 13/19] tipc: fix lockdep warning during bearer initialization Greg Kroah-Hartman
2013-09-12 17:26 ` [ 14/19] PARISC: include <linux/prefetch.h> in drivers/parisc/iommu-helpers.h Greg Kroah-Hartman
2013-09-12 17:26 ` [ 15/19] pci: frv architecture needs generic setup-bus infrastructure Greg Kroah-Hartman
2013-09-12 17:26 ` [ 16/19] m32r: consistently use "suffix-$(...)" Greg Kroah-Hartman
2013-09-12 17:26 ` [ 17/19] m32r: add memcpy() for CONFIG_KERNEL_GZIP=y Greg Kroah-Hartman
2013-09-12 17:26 ` [ 18/19] m32r: make memset() global for CONFIG_KERNEL_BZIP2=y Greg Kroah-Hartman
2013-09-12 17:26 ` [ 19/19] KVM: s390: move kvm_guest_enter,exit closer to sie Greg Kroah-Hartman
2013-09-12 22:29 ` [ 00/19] 3.0.96-stable review Guenter Roeck
2013-09-12 23:07 ` Greg Kroah-Hartman
2013-09-13 23:04 ` Shuah Khan
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