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Yuchung Cheng 1b7fdd2ab5 tcp: do not use cached RTT for RTT estimation
RTT cached in the TCP metrics are valuable for the initial timeout
because SYN RTT usually does not account for serialization delays
on low BW path.

However using it to seed the RTT estimator maybe disruptive because
other components (e.g., pacing) require the smooth RTT to be obtained
from actual connection.

The solution is to use the higher cached RTT to set the first RTO
conservatively like tcp_rtt_estimator(), but avoid seeding the other
RTT estimator variables such as srtt.  It is also a good idea to
keep RTO conservative to obtain the first RTT sample, and the
performance is insured by TCP loss probe if SYN RTT is available.

To keep the seeding formula consistent across SYN RTT and cached RTT,
the rttvar is twice the cached RTT instead of cached RTTVAR value. The
reason is because cached variation may be too small (near min RTO)
which defeats the purpose of being conservative on first RTO. However
the metrics still keep the RTT variations as they might be useful for
user applications (through ip).

Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Tested-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2013-08-30 15:14:38 -04:00
..
9p 9p: client: remove unused code and any reference to "cancelled" function 2013-07-30 15:54:28 -07:00
802 net/802/mrp: fix lockdep splat 2013-05-14 13:02:30 -07:00
8021q Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2013-08-16 15:37:26 -07:00
appletalk net: proc_fs: trivial: print UIDs as unsigned int 2013-08-15 14:37:46 -07:00
atm net: always pass struct netdev_notifier_info to netdevice notifiers 2013-05-28 21:58:54 -07:00
ax25 net: Convert uses of typedef ctl_table to struct ctl_table 2013-06-13 02:36:09 -07:00
batman-adv batman-adv: send GW_DEL event when the gw client mode is deselected 2013-08-28 11:33:00 +02:00
bluetooth Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/bluetooth/bluetooth 2013-07-31 15:11:50 -04:00
bridge bridge: inherit slave devices needed_headroom 2013-08-29 15:17:09 -04:00
caif net: pass info struct via netdevice notifier 2013-05-28 13:11:01 -07:00
can net: pass info struct via netdevice notifier 2013-05-28 13:11:01 -07:00
ceph net: add sk_stream_is_writeable() helper 2013-07-24 17:54:48 -07:00
core net: add netdev_upper_get_next_dev_rcu(dev, iter) 2013-08-29 16:19:42 -04:00
dcb rtnetlink: Remove passing of attributes into rtnl_doit functions 2013-03-22 10:31:16 -04:00
dccp net: add sk_stream_is_writeable() helper 2013-07-24 17:54:48 -07:00
decnet net: Convert uses of typedef ctl_table to struct ctl_table 2013-06-13 02:36:09 -07:00
dns_resolver net: strict_strtoul is obsolete, use kstrtoul instead 2013-07-12 16:09:14 -07:00
dsa dsa: fix freeing of sparse port allocation 2013-03-25 12:23:41 -04:00
ethernet net: Fix sysfs_format_mac() code duplication. 2013-07-16 17:09:22 -07:00
ieee802154 6lowpan: handle context based source address 2013-08-20 13:23:12 -07:00
ipv4 tcp: do not use cached RTT for RTT estimation 2013-08-30 15:14:38 -04:00
ipv6 ipv6: drop fragmented ndisc packets by default (RFC 6980) 2013-08-29 15:32:08 -04:00
ipx net: proc_fs: trivial: print UIDs as unsigned int 2013-08-15 14:37:46 -07:00
irda net/irda: fixed style issues in irttp 2013-07-19 17:34:40 -07:00
iucv net: delete __cpuinit usage from all net files 2013-07-14 19:36:58 -04:00
key xfrm: Remove rebundant address family checking 2013-08-07 10:12:58 +02:00
l2tp l2tp: make datapath resilient to packet loss when sequence numbers enabled 2013-07-02 16:33:25 -07:00
lapb net/lapb: remove depends on CONFIG_EXPERIMENTAL 2013-01-11 11:40:01 -08:00
llc net: proc_fs: trivial: print UIDs as unsigned int 2013-08-15 14:37:46 -07:00
mac80211 Merge branch 'for-john' of git://git.kernel.org/pub/scm/linux/kernel/git/jberg/mac80211-next 2013-08-09 15:08:10 -04:00
mac802154 Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2013-04-30 03:55:20 -04:00
mpls MPLS: Add limited GSO support 2013-05-27 22:50:59 -07:00
netfilter netfilter: ctnetlink: fix uninitialized variable 2013-08-28 00:28:19 +02:00
netlabel netlabel: use domain based selectors when address based selectors are not available 2013-08-02 16:57:01 -07:00
netlink Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2013-08-26 16:37:08 -04:00
netrom net: Convert uses of typedef ctl_table to struct ctl_table 2013-06-13 02:36:09 -07:00
nfc NFC: netlink: Rename CMD_FW_UPLOAD to CMD_FW_DOWNLOAD 2013-07-31 01:19:43 +02:00
openvswitch openvswitch: optimize flow compare and mask functions 2013-08-27 13:13:09 -07:00
packet net: packet: use reciprocal_divide in fanout_demux_hash 2013-08-29 16:43:29 -04:00
phonet net: proc_fs: trivial: print UIDs as unsigned int 2013-08-15 14:37:46 -07:00
rds net: Convert uses of typedef ctl_table to struct ctl_table 2013-06-13 02:36:09 -07:00
rfkill Merge branch 'for-john' of git://git.kernel.org/pub/scm/linux/kernel/git/jberg/mac80211-next 2013-04-22 14:58:14 -04:00
rose net: Convert uses of typedef ctl_table to struct ctl_table 2013-06-13 02:36:09 -07:00
rxrpc Driver core patches for 3.9-rc1 2013-02-21 12:05:51 -08:00
sched pkt_sched: fq: prefetch() fix 2013-08-30 14:51:59 -04:00
sctp net: sctp: sctp_verify_init: clean up mandatory checks and add comment 2013-08-29 15:54:48 -04:00
sunrpc Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2013-08-16 15:37:26 -07:00
tipc tipc: avoid possible deadlock while enable and disable bearer 2013-08-11 21:58:41 -07:00
unix af_unix: fix bug on large send() 2013-08-11 22:02:36 -07:00
vmw_vsock Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2013-08-16 15:37:26 -07:00
wimax
wireless Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2013-08-26 16:37:08 -04:00
x25 x25: Fix broken locking in ioctl error paths. 2013-07-01 18:15:25 -07:00
xfrm xfrm: remove irrelevant comment in xfrm_input(). 2013-08-19 12:45:16 +02:00
Kconfig Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2013-08-03 21:36:46 -07:00
Makefile MPLS: Add limited GSO support 2013-05-27 22:50:59 -07:00
compat.c net: Unbreak compat_sys_{send,recv}msg 2013-06-06 11:52:14 -07:00
nonet.c
socket.c net: rename CONFIG_NET_LL_RX_POLL to CONFIG_NET_RX_BUSY_POLL 2013-08-01 15:11:17 -07:00
sysctl_net.c user_ns: get rid of duplicate code in net_ctl_permissions 2012-11-18 20:32:45 -05:00