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2012-01-20tcp: fix undo after RTO for CUBICNeal Cardwell
This patch fixes CUBIC 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> Acked-by: Stephen Hemminger <shemminger@vyatta.com> Acked-by: Sangtae Ha <sangtae.ha@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2011-05-08tcp_cubic: limit delayed_ack ratio to prevent divide errorstephen hemminger
TCP Cubic keeps a metric that estimates the amount of delayed acknowledgements to use in adjusting the window. If an abnormally large number of packets are acknowledged at once, then the update could wrap and reach zero. This kind of ACK could only happen when there was a large window and huge number of ACK's were lost. This patch limits the value of delayed ack ratio. The choice of 32 is just a conservative value since normally it should be range of 1 to 4 packets. Signed-off-by: Stephen Hemminger <shemminger@vyatta.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2011-03-15Merge branch 'master' of ↵David S. Miller
master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6
2011-03-14tcp_cubic: fix low utilization of CUBIC with HyStartSangtae Ha
HyStart sets the initial exit point of slow start. Suppose that HyStart exits at 0.5BDP in a BDP network and no history exists. If the BDP of a network is large, CUBIC's initial cwnd growth may be too conservative to utilize the link. CUBIC increases the cwnd 20% per RTT in this case. Signed-off-by: Sangtae Ha <sangtae.ha@gmail.com> Acked-by: Stephen Hemminger <shemminger@vyatta.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2011-03-14tcp_cubic: make the delay threshold of HyStart less sensitiveSangtae Ha
Make HyStart less sensitive to abrupt delay variations due to buffer bloat. Signed-off-by: Sangtae Ha <sangtae.ha@gmail.com> Acked-by: Stephen Hemminger <shemminger@vyatta.com> Reported-by: Lucas Nussbaum <lucas.nussbaum@loria.fr> Signed-off-by: David S. Miller <davem@davemloft.net>
2011-03-14tcp_cubic: enable high resolution ack time if neededstephen hemminger
This is a refined version of an earlier patch by Lucas Nussbaum. Cubic needs RTT values in milliseconds. If HZ < 1000 then the values will be too coarse. Signed-off-by: Stephen Hemminger <shemminger@vyatta.com> Reported-by: Lucas Nussbaum <lucas.nussbaum@loria.fr> Signed-off-by: David S. Miller <davem@davemloft.net>
2011-03-14tcp_cubic: fix clock dependencystephen hemminger
The hystart code was written with assumption that HZ=1000. Replace the use of jiffies with bictcp_clock as a millisecond real time clock. Signed-off-by: Stephen Hemminger <shemminger@vyatta.com> Reported-by: Lucas Nussbaum <lucas.nussbaum@loria.fr> Signed-off-by: David S. Miller <davem@davemloft.net>
2011-03-14tcp_cubic: make ack train delta value a parameterstephen hemminger
Make the spacing between ACK's that indicates a train a tuneable value like other hystart values. Signed-off-by: Stephen Hemminger <shemminger@vyatta.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2011-03-14tcp_cubic: fix comparison of jiffiesstephen hemminger
Jiffies wraps around therefore the correct way to compare is to use cast to signed value. Note: cubic is not using full jiffies value on 64 bit arch because using full unsigned long makes struct bictcp grow too large for the available ca_priv area. Includes correction from Sangtae Ha to improve ack train detection. Signed-off-by: Stephen Hemminger <shemminger@vyatta.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2011-03-10tcp: mark tcp_congestion_ops read_mostlyStephen Hemminger
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 Järvinen
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>
2008-11-02[TCP] CUBIC v2.3Sangtae Ha
Signed-off-by: Sangtae Ha <sha2@ncsu.edu> Signed-off-by: David S. Miller <davem@davemloft.net>
2008-05-01rename div64_64 to div64_u64Roman Zippel
Rename div64_64 to div64_u64 to make it consistent with the other divide functions, so it clearly includes the type of the divide. Move its definition to math64.h as currently no architecture overrides the generic implementation. They can still override it of course, but the duplicated declarations are avoided. Signed-off-by: Roman Zippel <zippel@linux-m68k.org> Cc: Avi Kivity <avi@qumranet.com> Cc: Russell King <rmk@arm.linux.org.uk> Cc: Geert Uytterhoeven <geert@linux-m68k.org> Cc: Ralf Baechle <ralf@linux-mips.org> Cc: David Howells <dhowells@redhat.com> Cc: Jeff Dike <jdike@addtoit.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: "David S. Miller" <davem@davemloft.net> Cc: Patrick McHardy <kaber@trash.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-03-04[TCP]: TCP cubic v2.2Sangtae Ha
We have updated CUBIC to fix some issues with slow increase in large BDP networks. We also improved its convergence speed. The fix is in fact very simple -- the window increase limit of smax during the window probing phase (i.e., convex growth phase) is removed. We found that this does not affect TCP friendliness, but only improves its scalability. We have run some tests in our lab and also over the Internet path from NCSU to Japan. These results can be seen from the following page: http://netsrv.csc.ncsu.edu/wiki/index.php/Intra_protocol_fairness_testing_with_linux-2.6.23.9 http://netsrv.csc.ncsu.edu/wiki/index.php/RTT_fairness_testing_with_linux-2.6.23.9 http://netsrv.csc.ncsu.edu/wiki/index.php/TCP_friendliness_testing_with_linux-2.6.23.9 Signed-off-by: Sangtae Ha <sha2@ncsu.edu> Signed-off-by: Stephen Hemminger <shemminger@vyatta.com> Signed-off-by: David S. Miller <davem@davemloft.net>
2008-01-28[TCP]: Cong.ctrl modules: remove unused good_ack from cong_avoidIlpo Järvinen
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 Järvinen
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]: cubic - eliminate use of receive time stampStephen Hemminger
Remove use of received timestamp option value from RTT calculation in Cubic. A hostile receiver may be returning a larger timestamp option than the original value. This would cause the sender to believe the malevolent receiver had a larger RTT and because Cubic tries to provide some RTT friendliness, the sender would then favor the liar. Instead, use the jiffie resolutionRTT value already computed and passed back after ack. Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-07-31[TCP]: congestion control API pass RTT in microsecondsStephen Hemminger
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 Hemminger
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. Miller
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 Hemminger
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>
2007-04-25[TCP]: cubic update for net-2.6.22Stephen Hemminger
The following update received from Injong updates TCP cubic to the latest version. I am running more complete tests and will have results after 4/1. According to Injong: the new version improves on its scalability, fairness and stability. So in all properties, we confirmed it shows better performance. NCSU results (for 2.6.18 and 2.6.20) available: http://netsrv.csc.ncsu.edu/wiki/index.php/TCP_Testing This version is described in a new Internet draft for CUBIC. http://www.ietf.org/internet-drafts/draft-rhee-tcp-cubic-00.txt Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-04-25[TCP]: cubic optimizationStephen Hemminger
Use willy's work in optimizing cube root by having table for small values. Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-04-25[TCP] tcp_cubic: faster cube rootStephen Hemminger
The Newton-Raphson method is quadratically convergent so only a small fixed number of steps are necessary. Therefore it is faster to unroll the loop. Since div64_64 is no longer inline it won't cause code explosion. Also fixes a bug that can occur if x^2 was bigger than 32 bits. Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-04-25[NET]: div64_64 consolidate (rev3)Stephen Hemminger
Here is the current version of the 64 bit divide common code. Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-02-12[TCP]: Use read mostly for CUBIC parameters.Stephen Hemminger
These module parameters should be in the read mostly area to avoid cache pollution. Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org> Signed-off-by: David S. Miller <davem@davemloft.net>
2007-02-10[NET] IPV4: Fix whitespace errors.YOSHIFUJI Hideaki
Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org> Signed-off-by: David S. Miller <davem@davemloft.net>
2006-10-25[TCP] cubic: scaling errorStephen Hemminger
Doug Leith observed a discrepancy between the version of CUBIC described in the papers and the version in 2.6.18. A math error related to scaling causes Cubic to grow too slowly. Patch is from "Sangtae Ha" <sha2@ncsu.edu>. I validated that it does fix the problems. See the following to show behavior over 500ms 100 Mbit link. Sender (2.6.19-rc3) --- Bridge (2.6.18-rt7) ------- Receiver (2.6.19-rc3) 1G [netem] 100M http://developer.osdl.org/shemminger/tcp/2.6.19-rc3/cubic-orig.png http://developer.osdl.org/shemminger/tcp/2.6.19-rc3/cubic-fix.png Signed-off-by: Stephen Hemminger <shemminger@osdl.org> Signed-off-by: David S. Miller <davem@davemloft.net>
2006-09-22[TCP] Congestion control (modulo lp, bic): use BUILD_BUG_ONAlexey Dobriyan
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 Engel
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 Hemminger
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] cubic: use Newton-RaphsonStephen Hemminger
Replace cube root algorithim with a faster version using Newton-Raphson. Surprisingly, doing the scaled div64_64 is faster than a true 64 bit division on 64 bit CPU's. Signed-off-by: Stephen Hemminger <shemminger@osdl.org> Signed-off-by: David S. Miller <davem@davemloft.net>
2006-01-03[TCP] cubic: precompute constantsStephen Hemminger
Revised version of patch to pre-compute values for TCP cubic. * d32,d64 replaced with descriptive names * cube_factor replaces srtt[scaled by count] / HZ * ((1 << (10+2*BICTCP_HZ)) / bic_scale) * beta_scale replaces 8*(BICTCP_BETA_SCALE+beta)/3/(BICTCP_BETA_SCALE-beta); Signed-off-by: Stephen Hemminger <shemminger@osdl.org> Signed-off-by: David S. Miller <davem@davemloft.net>
2006-01-03[TCP] BIC: CUBIC window growth (2.0)Stephen Hemminger
Replace existing BIC version 1.1 with new version 2.0. The main change is to replace the window growth function with a cubic function as described in: http://www.csc.ncsu.edu/faculty/rhee/export/bitcp/cubic-paper.pdf Signed-off-by: Stephen Hemminger <shemminger@osdl.org> Signed-off-by: David S. Miller <davem@davemloft.net>
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