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2016-05-11tcp: replace cnt & rtt with struct in pkts_acked()Lawrence Brakmo1-3/+3
Replace 2 arguments (cnt and rtt) in the congestion control modules' pkts_acked() function with a struct. This will allow adding more information without having to modify existing congestion control modules (tcp_nv in particular needs bytes in flight when packet was sent). As proposed by Neal Cardwell in his comments to the tcp_nv patch. Signed-off-by: Lawrence Brakmo <brakmo@fb.com> Acked-by: Yuchung Cheng <ycheng@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2015-07-09tcp: add tcp_in_slow_start helperYuchung Cheng1-1/+1
Add a helper to test the slow start condition in various congestion control modules and other places. This is to prepare a slight improvement in policy as to exactly when to slow start. 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>
2015-01-28tcp: stretch ACK fixes prepNeal Cardwell1-1/+1
LRO, GRO, delayed ACKs, and middleboxes can cause "stretch ACKs" that cover more than the RFC-specified maximum of 2 packets. These stretch ACKs can cause serious performance shortfalls in common congestion control algorithms that were designed and tuned years ago with receiver hosts that were not using LRO or GRO, and were instead politely ACKing every other packet. This patch series fixes Reno and CUBIC to handle stretch ACKs. This patch prepares for the upcoming stretch ACK bug fix patches. It adds an "acked" parameter to tcp_cong_avoid_ai() to allow for future fixes to tcp_cong_avoid_ai() to correctly handle stretch ACKs, and changes all congestion control algorithms to pass in 1 for the ACKed count. It also changes tcp_slow_start() to return the number of packet ACK "credits" that were not processed in slow start mode, and can be processed by the congestion control module in additive increase mode. In future patches we will fix tcp_cong_avoid_ai() to handle stretch ACKs, and fix Reno and CUBIC handling of stretch ACKs in slow start and additive increase mode. Reported-by: Eyal Perry <eyalpe@mellanox.com> Signed-off-by: Neal Cardwell <ncardwell@google.com> Signed-off-by: Yuchung Cheng <ycheng@google.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2014-09-01tcp: whitespace fixesstephen hemminger1-7/+4
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 Dumazet1-3/+2
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>
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>
2012-01-20tcp: fix undo after RTO for BICNeal Cardwell1-4/+7
This patch fixes BIC so that cwnd reductions made during RTOs can be undone (just as they already can be undone when using the default/Reno behavior). When undoing cwnd reductions, BIC-derived congestion control modules were restoring the cwnd from last_max_cwnd. There were two problems with using last_max_cwnd to restore a cwnd during undo: (a) last_max_cwnd was set to 0 on state transitions into TCP_CA_Loss (by calling the module's reset() functions), so cwnd reductions from RTOs could not be undone. (b) when fast_covergence is enabled (which it is by default) last_max_cwnd does not actually hold the value of snd_cwnd before the loss; instead, it holds a scaled-down version of snd_cwnd. This patch makes the following changes: (1) upon undo, revert snd_cwnd to ca->loss_cwnd, which is already, as the existing comment notes, the "congestion window at last loss" (2) stop forgetting ca->loss_cwnd on TCP_CA_Loss events (3) use ca->last_max_cwnd to check if we're in slow start Signed-off-by: Neal Cardwell <ncardwell@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>
2009-03-02tcp: add helper for AI algorithmIlpo Järvinen1-10/+1
It seems that implementation in yeah was inconsistent to what other did as it would increase cwnd one ack earlier than the others do. Size benefits: bictcp_cong_avoid | -36 tcp_cong_avoid_ai | +52 bictcp_cong_avoid | -34 tcp_scalable_cong_avoid | -36 tcp_veno_cong_avoid | -12 tcp_yeah_cong_avoid | -38 = -104 bytes total Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi> Signed-off-by: David S. Miller <davem@davemloft.net>
2008-02-28[TCP]: BIC web page link is corrected.Sangtae Ha1-2/+3
Signed-off-by: Sangtae Ha <sha2@ncsu.edu> Signed-off-by: David S. Miller <davem@davemloft.net>
2008-01-28[TCP]: Cong.ctrl modules: remove unused good_ack from cong_avoidIlpo Järvinen1-2/+1
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>
2007-10-10[TCP]: Remove num_acked>0 checks from cong.ctrl mods pkts_ackedIlpo Järvinen1-1/+1
There is no need for such check in pkts_acked because the callback is not invoked unless at least one segment got fully ACKed (i.e., the snd_una moved past skb's end_seq) by the cumulative ACK's snd_una advancement. Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-07-31[TCP]: congestion control API pass RTT in microsecondsStephen Hemminger1-1/+1
This patch changes the API for the callback that is done after an ACK is received. It solves a couple of issues: * Some congestion controls want higher resolution value of RTT (controlled by TCP_CONG_RTT_SAMPLE flag). These don't really want a ktime, but all compute a RTT in microseconds. * Other congestion control could use RTT at jiffies resolution. To keep API consistent the units should be the same for both cases, just the resolution should change. Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-07-18[TCP]: remove unused argument to cong_avoid opStephen Hemminger1-1/+1
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>
2007-06-13[TCP]: Set initial_ssthresh default to zero in Cubic and BIC.David S. Miller1-1/+1
Because of the current default of 100, Cubic and BIC perform very poorly compared to standard Reno. In the worst case, this change makes Cubic and BIC as aggressive as Reno. So this change should be very safe. Signed-off-by: David S. Miller <davem@davemloft.net>
2007-04-25[TCP]: Congestion control API update.Stephen Hemminger1-1/+1
Do some simple changes to make congestion control API faster/cleaner. * use ktime_t rather than timeval * merge rtt sampling into existing ack callback this means one indirect call versus two per ack. * use flags bits to store options/settings Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org> Signed-off-by: David S. Miller <davem@davemloft.net>
2006-09-22[TCP] tcp_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>
2006-06-17[TCP]: Minimum congestion window consolidation.Stephen Hemminger1-7/+0
Many of the TCP congestion methods all just use ssthresh as the minimum congestion window on decrease. Rather than duplicating the code, just have that be the default if that handle in the ops structure is not set. Minor behaviour change to TCP compound. It probably wants to use this (ssthresh) as lower bound, rather than ssthresh/2 because the latter causes undershoot on loss. Signed-off-by: Stephen Hemminger <shemminger@osdl.org> Signed-off-by: David S. Miller <davem@davemloft.net>
2006-01-03[TCP] BIC: spelling and whitespaceStephen Hemminger1-2/+2
Signed-off-by: Stephen Hemminger <shemminger@osdl.org> Signed-off-by: David S. Miller <davem@davemloft.net>
2006-01-03[TCP] BIC: remove low utilization code.Stephen Hemminger1-80/+1
The latest BICTCP patch at: http://www.csc.ncsu.edu:8080/faculty/rhee/export/bitcp/index_files/Page546.htm disables the low_utilization feature of BICTCP because it doesn't work in some cases. This patch removes it. Signed-off-by: Stephen Hemminger <shemminger@osdl.org> Signed-off-by: David S. Miller <davem@davemloft.net>
2005-11-10[TCP]: add tcp_slow_start helperStephen Hemminger1-6/+4
Move all the code that does linear TCP slowstart to one inline function to ease later patch to add ABC support. Signed-off-by: Stephen Hemminger <shemminger@osdl.org> Signed-off-by: David S. Miller <davem@davemloft.net>
2005-11-10[TCP]: fix congestion window update when using TSO deferalStephen Hemminger1-1/+1
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>
2005-11-02[TCP]: BIC max increment too largeStephen Hemminger1-1/+1
The max growth of BIC TCP is too large. Original code was based on BIC 1.0 and the default there was 32. Later code (2.6.13) included compensation for delayed acks, and should have reduced the default value to 16; since normally TCP gets one ack for every two packets sent. The current value of 32 makes BIC too aggressive and unfair to other flows. Submitted-by: Injong Rhee <rhee@eos.ncsu.edu> Signed-off-by: Stephen Hemminger <shemminger@osdl.org> Acked-by: Ian McDonald <imcdnzl@gmail.com> Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
2005-10-05[TCP]: BIC coding bug in Linux 2.6.13Stephen Hemminger1-1/+1
Missing parenthesis in causes BIC to be slow in increasing congestion window. Spotted by Injong Rhee. 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 Melo1-20/+26
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 BIC congestion control module.Stephen Hemminger1-0/+331
TCP BIC congestion control reworked to use the new congestion control infrastructure. This version is more up to date than the BIC code in 2.6.12; it incorporates enhancements from BICTCP 1.1, to handle low latency links. Signed-off-by: Stephen Hemminger <shemminger@osdl.org> Signed-off-by: David S. Miller <davem@davemloft.net>
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