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2016-11-21tcp: make undo_cwnd mandatory for congestion modulesFlorian Westphal1-0/+1
The undo_cwnd fallback in the stack doubles cwnd based on ssthresh, which un-does reno halving behaviour. It seems more appropriate to let congctl algorithms pair .ssthresh and .undo_cwnd properly. Add a 'tcp_reno_undo_cwnd' function and wire it up for all congestion algorithms that used to rely on the fallback. Cc: Eric Dumazet <edumazet@google.com> Cc: Yuchung Cheng <ycheng@google.com> Cc: Neal Cardwell <ncardwell@google.com> Signed-off-by: Florian Westphal <fw@strlen.de> Signed-off-by: David S. Miller <davem@davemloft.net>
2015-07-09tcp: do not slow start when cwnd equals ssthreshYuchung Cheng1-1/+1
In the original design slow start is only used to raise cwnd when cwnd is stricly below ssthresh. It makes little sense to slow start when cwnd == ssthresh: especially when hystart has set ssthresh in the initial ramp, or after recovery when cwnd resets to ssthresh. Not doing so will also help reduce the buffer bloat slightly. Signed-off-by: Yuchung Cheng <ycheng@google.com> Signed-off-by: Neal Cardwell <ncardwell@google.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: Nandita Dukkipati <nanditad@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2014-09-01tcp: whitespace fixesstephen hemminger1-1/+0
Fix places where there is space before tab, long lines, and awkward if(){, double spacing etc. Add blank line after declaration/initialization. Signed-off-by: Stephen Hemminger <stephen@networkplumber.org> Signed-off-by: David S. Miller <davem@davemloft.net>
2014-05-03tcp: remove in_flight parameter from cong_avoid() methodsEric Dumazet1-4/+3
Commit e114a710aa505 ("tcp: fix cwnd limited checking to improve congestion control") obsoleted in_flight parameter from tcp_is_cwnd_limited() and its callers. This patch does the removal as promised. Signed-off-by: Eric Dumazet <edumazet@google.com> Acked-by: Neal Cardwell <ncardwell@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2014-02-26tcp: switch rtt estimations to usec resolutionEric Dumazet1-5/+7
Upcoming congestion controls for TCP require usec resolution for RTT estimations. Millisecond resolution is simply not enough these days. FQ/pacing in DC environments also require this change for finer control and removal of bimodal behavior due to the current hack in tcp_update_pacing_rate() for 'small rtt' TCP_CONG_RTT_STAMP is no longer needed. As Julian Anastasov pointed out, we need to keep user compatibility : tcp_metrics used to export RTT and RTTVAR in msec resolution, so we added RTT_US and RTTVAR_US. An iproute2 patch is needed to use the new attributes if provided by the kernel. In this example ss command displays a srtt of 32 usecs (10Gbit link) lpk51:~# ./ss -i dst lpk52 Netid State Recv-Q Send-Q Local Address:Port Peer Address:Port tcp ESTAB 0 1 10.246.11.51:42959 10.246.11.52:64614 cubic wscale:6,6 rto:201 rtt:0.032/0.001 ato:40 mss:1448 cwnd:10 send 3620.0Mbps pacing_rate 7240.0Mbps unacked:1 rcv_rtt:993 rcv_space:29559 Updated iproute2 ip command displays : lpk51:~# ./ip tcp_metrics | grep 10.246.11.52 10.246.11.52 age 561.914sec cwnd 10 rtt 274us rttvar 213us source 10.246.11.51 Old binary displays : lpk51:~# ip tcp_metrics | grep 10.246.11.52 10.246.11.52 age 561.914sec cwnd 10 rtt 250us rttvar 125us source 10.246.11.51 With help from Julian Anastasov, Stephen Hemminger and Yuchung Cheng Signed-off-by: Eric Dumazet <edumazet@google.com> Acked-by: Neal Cardwell <ncardwell@google.com> Cc: Stephen Hemminger <stephen@networkplumber.org> Cc: Yuchung Cheng <ycheng@google.com> Cc: Larry Brakmo <brakmo@google.com> Cc: Julian Anastasov <ja@ssi.bg> Signed-off-by: David S. Miller <davem@davemloft.net>
2014-02-13tcp: remove unused min_cwnd member of tcp_congestion_opsStanislav Fomichev1-1/+0
Commit 684bad110757 "tcp: use PRR to reduce cwin in CWR state" removed all calls to min_cwnd, so we can safely remove it. Also, remove tcp_reno_min_cwnd because it was only used for min_cwnd. Signed-off-by: Stanislav Fomichev <stfomichev@yandex-team.ru> Acked-by: Yuchung Cheng <ycheng@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2013-11-04tcp: properly handle stretch acks in slow startYuchung Cheng1-2/+3
Slow start now increases cwnd by 1 if an ACK acknowledges some packets, regardless the number of packets. Consequently slow start performance is highly dependent on the degree of the stretch ACKs caused by receiver or network ACK compression mechanisms (e.g., delayed-ACK, GRO, etc). But slow start algorithm is to send twice the amount of packets of packets left so it should process a stretch ACK of degree N as if N ACKs of degree 1, then exits when cwnd exceeds ssthresh. A follow up patch will use the remainder of the N (if greater than 1) to adjust cwnd in the congestion avoidance phase. In addition this patch retires the experimental limited slow start (LSS) feature. LSS has multiple drawbacks but questionable benefit. The fractional cwnd increase in LSS requires a loop in slow start even though it's rarely used. Configuring such an increase step via a global sysctl on different BDPS seems hard. Finally and most importantly the slow start overshoot concern is now better covered by the Hybrid slow start (hystart) enabled by default. Signed-off-by: Yuchung Cheng <ycheng@google.com> Signed-off-by: Neal Cardwell <ncardwell@google.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2012-05-17tcp: bool conversionsEric Dumazet1-5/+5
bool conversions where possible. __inline__ -> inline space cleanups Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2011-03-10tcp: mark tcp_congestion_ops read_mostlyStephen Hemminger1-1/+1
Signed-off-by: Stephen Hemminger <shemminger@vyatta.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2010-06-02TCP: tcp_hybla: Fix integer overflow in slow start incrementDaniele Lacamera1-2/+2
For large values of rtt, 2^rho operation may overflow u32. Clamp down the increment to 2^16. Signed-off-by: Daniele Lacamera <root@danielinux.net> Signed-off-by: David S. Miller <davem@davemloft.net>
2008-10-07tcp: Fix tcp_hybla zero congestion window growth with small rho and large cwnd.Daniele Lacamera1-1/+5
Because of rounding, in certain conditions, i.e. when in congestion avoidance state rho is smaller than 1/128 of the current cwnd, TCP Hybla congestion control starves and the cwnd is kept constant forever. This patch forces an increment by one segment after #send_cwnd calls without increments(newreno behavior). Signed-off-by: Daniele Lacamera <root@danielinux.net> Signed-off-by: David S. Miller <davem@davemloft.net>
2008-05-01net: fix returning void-valued expression warningsHarvey Harrison1-2/+4
drivers/net/8390.c:37:2: warning: returning void-valued expression drivers/net/bnx2.c:1635:3: warning: returning void-valued expression drivers/net/xen-netfront.c:1806:2: warning: returning void-valued expression net/ipv4/tcp_hybla.c:105:3: warning: returning void-valued expression net/ipv4/tcp_vegas.c:171:3: warning: returning void-valued expression net/ipv4/tcp_veno.c:123:3: warning: returning void-valued expression net/sysctl_net.c:85:2: warning: returning void-valued expression Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com> Acked-by: Alan Cox <alan@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2008-01-28[TCP]: Cong.ctrl modules: remove unused good_ack from cong_avoidIlpo Järvinen1-3/+2
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-07-18[TCP]: remove unused argument to cong_avoid opStephen Hemminger1-2/+2
None of the existing TCP congestion controls use the rtt value pased in the ca_ops->cong_avoid interface. Which is lucky because seq_rtt could have been -1 when handling a duplicate ack. Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-04-25[TCP]: whitespace cleanupStephen Hemminger1-1/+1
Add whitespace around keywords. Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org> Signed-off-by: David S. Miller <davem@davemloft.net>
2006-09-22[TCP] Congestion control (modulo lp, bic): use BUILD_BUG_ONAlexey Dobriyan1-1/+1
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2006-06-30Remove obsolete #include <linux/config.h>Jörn Engel1-1/+0
Signed-off-by: Jörn Engel <joern@wohnheim.fh-wedel.de> Signed-off-by: Adrian Bunk <bunk@stusta.de>
2005-11-10[TCP]: fix congestion window update when using TSO deferalStephen Hemminger1-3/+3
TCP peformance with TSO over networks with delay is awful. On a 100Mbit link with 150ms delay, we get 4Mbits/sec with TSO and 50Mbits/sec without TSO. The problem is with TSO, we intentionally do not keep the maximum number of packets in flight to fill the window, we hold out to until we can send a MSS chunk. But, we also don't update the congestion window unless we have filled, as per RFC2861. This patch replaces the check for the congestion window being full with something smarter that accounts for TSO. Signed-off-by: Stephen Hemminger <shemminger@osdl.org> Signed-off-by: David S. Miller <davem@davemloft.net>
2005-08-29[ICSK]: Move TCP congestion avoidance members to icskArnaldo Carvalho de Melo1-15/+16
This changeset basically moves tcp_sk()->{ca_ops,ca_state,etc} to inet_csk(), minimal renaming/moving done in this changeset to ease review. Most of it is just changes of struct tcp_sock * to struct sock * parameters. With this we move to a state closer to two interesting goals: 1. Generalisation of net/ipv4/tcp_diag.c, becoming inet_diag.c, being used for any INET transport protocol that has struct inet_hashinfo and are derived from struct inet_connection_sock. Keeps the userspace API, that will just not display DCCP sockets, while newer versions of tools can support DCCP. 2. INET generic transport pluggable Congestion Avoidance infrastructure, using the current TCP CA infrastructure with DCCP. Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2005-06-23[TCP]: Add TCP Hybla congestion control module.Daniele Lacamera1-0/+187
TCP Hybla congestion avoidance. - "In heterogeneous networks, TCP connections that incorporate a terrestrial or satellite radio link are greatly disadvantaged with respect to entirely wired connections, because of their longer round trip times (RTTs). To cope with this problem, a new TCP proposal, the TCP Hybla, is presented and discussed in the paper[1]. It stems from an analytical evaluation of the congestion window dynamics in the TCP standard versions (Tahoe, Reno, NewReno), which suggests the necessary modifications to remove the performance dependence on RTT.[...]"[1] [1]: Carlo Caini, Rosario Firrincieli, "TCP Hybla: a TCP enhancement for heterogeneous networks", International Journal of Satellite Communications and Networking Volume 22, Issue 5 , Pages 547 - 566. September 2004. Signed-off-by: Daniele Lacamera (root at danielinux.net)net Signed-off-by: Stephen Hemminger <shemminger@osdl.org> Signed-off-by: David S. Miller <davem@davemloft.net>
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