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f278b99ca6
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Eric Dumazet f278b99ca6 tcp_cubic: refactor code to perform a divide only when needed 
Neal Cardwell suggested to not change ca->delay_min
and apply the ack delay cushion only when Hystart ACK train
is still under consideration. This should avoid a 64bit
divide unless needed.

Tested:

40Gbit(mlx4) testbed (with sch_fq as packet scheduler)

$ echo -n 'file tcp_cubic.c +p'  >/sys/kernel/debug/dynamic_debug/control
$ nstat -n;for f in {1..10}; do ./super_netperf 1 -H lpaa24 -l -4000000; done;nstat|egrep "Hystart"
  14815
  16280
  15293
  15563
  11574
  15145
  14789
  18548
  16972
  12520
TcpExtTCPHystartTrainDetect     10                 0.0
TcpExtTCPHystartTrainCwnd       1396               0.0
$ dmesg | tail -10
[ 4873.951350] hystart_ack_train (116 > 93) delay_min 24 (+ ack_delay 69) cwnd 80
[ 4875.155379] hystart_ack_train (55 > 50) delay_min 21 (+ ack_delay 29) cwnd 160
[ 4876.333921] hystart_ack_train (69 > 62) delay_min 23 (+ ack_delay 39) cwnd 130
[ 4877.519037] hystart_ack_train (69 > 60) delay_min 22 (+ ack_delay 38) cwnd 130
[ 4878.701559] hystart_ack_train (87 > 63) delay_min 24 (+ ack_delay 39) cwnd 160
[ 4879.844597] hystart_ack_train (93 > 50) delay_min 21 (+ ack_delay 29) cwnd 216
[ 4880.956650] hystart_ack_train (74 > 67) delay_min 20 (+ ack_delay 47) cwnd 108
[ 4882.098500] hystart_ack_train (61 > 57) delay_min 23 (+ ack_delay 34) cwnd 130
[ 4883.262056] hystart_ack_train (72 > 67) delay_min 21 (+ ack_delay 46) cwnd 130
[ 4884.418760] hystart_ack_train (74 > 67) delay_min 29 (+ ack_delay 38) cwnd 152

10Gbit(bnx2x) testbed (with sch_fq as packet scheduler)

$ echo -n 'file tcp_cubic.c +p'  >/sys/kernel/debug/dynamic_debug/control
$ nstat -n;for f in {1..10}; do ./super_netperf 1 -H lpk52 -l -4000000; done;nstat|egrep "Hystart"
   7050
   7065
   7100
   6900
   7202
   7263
   7189
   6869
   7463
   7034
TcpExtTCPHystartTrainDetect     10                 0.0
TcpExtTCPHystartTrainCwnd       3199               0.0
$ dmesg | tail -10
[  176.920012] hystart_ack_train (161 > 141) delay_min 83 (+ ack_delay 58) cwnd 264
[  179.144645] hystart_ack_train (164 > 159) delay_min 120 (+ ack_delay 39) cwnd 444
[  181.354527] hystart_ack_train (214 > 168) delay_min 125 (+ ack_delay 43) cwnd 436
[  183.539565] hystart_ack_train (170 > 147) delay_min 96 (+ ack_delay 51) cwnd 326
[  185.727309] hystart_ack_train (177 > 160) delay_min 61 (+ ack_delay 99) cwnd 128
[  187.947142] hystart_ack_train (184 > 167) delay_min 123 (+ ack_delay 44) cwnd 367
[  190.166680] hystart_ack_train (230 > 153) delay_min 116 (+ ack_delay 37) cwnd 444
[  192.327285] hystart_ack_train (210 > 206) delay_min 86 (+ ack_delay 120) cwnd 152
[  194.511392] hystart_ack_train (173 > 151) delay_min 94 (+ ack_delay 57) cwnd 239
[  196.736023] hystart_ack_train (149 > 146) delay_min 105 (+ ack_delay 41) cwnd 399

Fixes: 42f3a8aaae ("tcp_cubic: tweak Hystart detection for short RTT flows")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Neal Cardwell <ncardwell@google.com>
Link: https://www.spinics.net/lists/netdev/msg621886.html
Link: https://www.spinics.net/lists/netdev/msg621797.html
Acked-by: Neal Cardwell <ncardwell@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2019-12-30 14:44:27 -08:00
..
6lowpan
9p 9p pull request for inclusion in 5.4 2019-09-27 15:10:34 -07:00
802 treewide: Use sizeof_field() macro 2019-12-09 10:36:44 -08:00
8021q net: vlan: Use the PHY time stamping interface. 2019-12-25 19:51:33 -08:00
appletalk
atm netdev: pass the stuck queue to the timeout handler 2019-12-12 21:38:57 -08:00
ax25 net: use helpers to change sk_ack_backlog 2019-11-06 16:14:48 -08:00
batman-adv treewide: Use sizeof_field() macro 2019-12-09 10:36:44 -08:00
bluetooth netdev: pass the stuck queue to the timeout handler 2019-12-12 21:38:57 -08:00
bpf bpf: Allow to change skb mark in test_run 2019-12-18 17:05:58 -08:00
bpfilter
bridge Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2019-12-22 15:15:05 -08:00
caif Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2019-11-02 13:54:56 -07:00
can can: j1939: j1939_sk_bind(): take priv after lock is held 2019-12-08 11:52:02 +01:00
ceph libceph, rbd, ceph: convert to use the new mount API 2019-11-27 22:28:37 +01:00
core Merge git://git.kernel.org/pub/scm/linux/kernel/git/pablo/nf-next 2019-12-30 14:22:11 -08:00
dcb
dccp treewide: Use sizeof_field() macro 2019-12-09 10:36:44 -08:00
decnet net: use helpers to change sk_ack_backlog 2019-11-06 16:14:48 -08:00
dns_resolver
dsa net: dsa: Deny PTP on master if switch supports it 2019-12-28 11:43:41 -08:00
ethernet net: add annotations on hh->hh_len lockless accesses 2019-11-07 20:07:30 -08:00
ethtool ethtool: provide link state with LINKSTATE_GET request 2019-12-27 16:40:02 -08:00
hsr hsr: fix a NULL pointer dereference in hsr_dev_xmit() 2019-12-05 12:09:02 -08:00
ieee802154 Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2019-11-02 13:54:56 -07:00
ife
ipv4 tcp_cubic: refactor code to perform a divide only when needed 2019-12-30 14:44:27 -08:00
ipv6 ipv6: Remove old route notifications and convert listeners 2019-12-24 22:37:30 -08:00
iucv treewide: Use sizeof_field() macro 2019-12-09 10:36:44 -08:00
kcm kcm: disable preemption in kcm_parse_func_strparser() 2019-09-27 10:27:14 +02:00
key
l2tp net: ipv6: add net argument to ip6_dst_lookup_flow 2019-12-04 12:27:12 -08:00
l3mdev
lapb
llc llc2: Fix return statement of llc_stat_ev_rx_null_dsap_xid_c (and _test_c) 2019-12-20 21:19:36 -08:00
mac80211 mac80211: Turn AQL into an NL80211_EXT_FEATURE 2019-12-13 10:34:04 +01:00
mac802154
mpls net: ipv6_stub: use ip6_dst_lookup_flow instead of ip6_dst_lookup 2019-12-04 12:27:13 -08:00
ncsi
netfilter Merge git://git.kernel.org/pub/scm/linux/kernel/git/pablo/nf-next 2019-12-30 14:22:11 -08:00
netlabel
netlink treewide: Use sizeof_field() macro 2019-12-09 10:36:44 -08:00
netrom net: core: add generic lockdep keys 2019-10-24 14:53:48 -07:00
nfc net: nfc: nci: fix a possible sleep-in-atomic-context bug in nci_uart_tty_receive() 2019-12-18 11:57:33 -08:00
nsh
openvswitch openvswitch: New MPLS actions for layer 2 tunnelling 2019-12-24 22:24:45 -08:00
packet af_packet: refactoring code for prb_calc_retire_blk_tmo 2019-12-26 15:19:59 -08:00
phonet net: use skb_queue_empty_lockless() in poll() handlers 2019-10-28 13:33:41 -07:00
psample net: psample: fix skb_over_panic 2019-11-26 14:40:13 -08:00
qrtr net: qrtr: Simplify 'qrtr_tun_release()' 2019-10-30 17:58:23 -07:00
rds Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2019-11-16 21:51:42 -08:00
rfkill rfkill: Fix incorrect check to avoid NULL pointer dereference 2019-12-16 10:15:49 +01:00
rose net: use helpers to change sk_ack_backlog 2019-11-06 16:14:48 -08:00
rxrpc treewide: Use sizeof_field() macro 2019-12-09 10:36:44 -08:00
sched Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2019-12-22 15:15:05 -08:00
sctp sctp: do trace_sctp_probe after SACK validation and check 2019-12-27 16:34:51 -08:00
smc Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2019-12-22 15:15:05 -08:00
strparser
sunrpc This is a relatively quiet cycle for nfsd, mainly various bugfixes. 2019-12-07 16:56:00 -08:00
switchdev
tipc Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2019-12-22 15:15:05 -08:00
tls net/tls: add helper for testing if socket is RX offloaded 2019-12-19 17:46:51 -08:00
unix Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2019-12-22 15:15:05 -08:00
vmw_vsock Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2019-12-22 15:15:05 -08:00
wimax
wireless Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2019-12-22 15:15:05 -08:00
x25 net/x25: add new state X25_STATE_5 2019-12-09 10:28:43 -08:00
xdp Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next 2019-12-27 14:20:10 -08:00
xfrm Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next 2019-11-25 20:02:57 -08:00
compat.c y2038: socket: use __kernel_old_timespec instead of timespec 2019-11-15 14:38:29 +01:00
Kconfig ethtool: introduce ethtool netlink interface 2019-12-27 16:40:01 -08:00
Makefile ethtool: move to its own directory 2019-12-12 17:07:05 -08:00
socket.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2019-12-22 15:15:05 -08:00
sysctl_net.c