Commit Graph

29 Commits

Author SHA1 Message Date
Yuchung Cheng 9f9843a751 tcp: properly handle stretch acks in slow start
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>
2013-11-04 19:57:59 -05:00
Stephen Hemminger a252bebe22 tcp: mark tcp_congestion_ops read_mostly
Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2011-03-10 00:40:17 -08:00
Doug Leith c80a5cdfc5 tcp: tcp_vegas ssthresh bugfix
This patch fixes ssthresh accounting issues in tcp_vegas when cwnd decreases

Signed-off-by: Doug Leith <doug.leith@nuim.ie>
Signed-off-by: David S. Miller <davem@davemloft.net>
2009-05-25 22:44:59 -07:00
Doug Leith 8d3a564da3 tcp: tcp_vegas cong avoid fix
This patch addresses a book-keeping issue in tcp_vegas.c.  At present
tcp_vegas does separate book-keeping of cwnd based on packet sequence
numbers.  A mismatch can develop between this book-keeping and
tp->snd_cwnd due, for example, to delayed acks acking multiple
packets.  When vegas transitions to reno operation (e.g. following
loss), then this mismatch leads to incorrect behaviour (akin to a cwnd
backoff).  This seems mostly to affect operation at low cwnds where
delayed acking can lead to a significant fraction of cwnd being
covered by a single ack, leading to the book-keeping mismatch.  This
patch modifies the congestion avoidance update to avoid the need for
separate book-keeping while leaving vegas congestion avoidance
functionally unchanged.  A secondary advantage of this modification is
that the use of fixed-point (via V_PARAM_SHIFT) and 64 bit arithmetic
is no longer necessary, simplifying the code.

Some example test measurements with the patched code (confirming no functional
change in the congestion avoidance algorithm) can be seen at:

http://www.hamilton.ie/doug/vegaspatch/

Signed-off-by: Doug Leith <doug.leith@nuim.ie>
Signed-off-by: David S. Miller <davem@davemloft.net>
2008-12-09 00:13:04 -08:00
Doug Leith a6af2d6ba5 tcp: tcp_vegas ssthresh bug fix
This patch fixes a bug in tcp_vegas.c.  At the moment this code leaves
ssthresh untouched.  However, this means that the vegas congestion
control algorithm is effectively unable to reduce cwnd below the
ssthresh value (if the vegas update lowers the cwnd below ssthresh,
then slow start is activated to raise it back up).  One example where
this matters is when during slow start cwnd overshoots the link
capacity and a flow then exits slow start with ssthresh set to a value
above where congestion avoidance would like to adjust it.

Signed-off-by: Doug Leith <doug.leith@nuim.ie>
Signed-off-by: David S. Miller <davem@davemloft.net>
2008-12-04 17:17:18 -08:00
Harvey Harrison ab59859de1 net: fix returning void-valued expression warnings
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>
2008-05-01 02:47:38 -07:00
Lachlan Andrew 159131149c tcp: Overflow bug in Vegas
From: Lachlan Andrew <lachlan.andrew@gmail.com>

There is an overflow bug in net/ipv4/tcp_vegas.c for large BDPs
(e.g. 400Mbit/s, 400ms).  The multiplication (old_wnd *
vegas->baseRTT) << V_PARAM_SHIFT overflows a u32.

[ Fix tcp_veno.c too, it has similar calculations. -DaveM ]

Signed-off-by: David S. Miller <davem@davemloft.net>
2008-04-30 01:04:03 -07:00
Ilpo Järvinen c3a05c6050 [TCP]: Cong.ctrl modules: remove unused good_ack from cong_avoid
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>
2008-01-28 14:55:41 -08:00
Xiaoliang (David) Wei c940587bf6 [TCP] vegas: Fix a bug in disabling slow start by gamma parameter.
TCP Vegas implementation has a bug in the process of disabling
slow-start with gamma parameter. The bug may lead to extreme
unfairness in the presence of early packet loss. See details in:
http://www.cs.caltech.edu/~weixl/technical/ns2linux/known_linux/index.html#vegas

Switch the order of "if (tp->snd_cwnd <= tp->snd_ssthresh)" statement
and "if (diff > gamma)" statement to eliminate the problem.

Signed-off-by: Xiaoliang (David) Wei <davidwei79@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2007-10-29 22:37:25 -07:00
Stephen Hemminger 30cfd0baf0 [TCP]: congestion control API pass RTT in microseconds
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>
2007-07-31 02:27:57 -07:00
Stephen Hemminger 16751347a0 [TCP]: remove unused argument to cong_avoid op
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>
2007-07-18 01:46:58 -07:00
Ilpo Järvinen b9ce204f0a [TCP]: Congestion control API RTT sampling fix
Commit 164891aadf broke RTT
sampling of congestion control modules. Inaccurate timestamps
could be fed to them without providing any way for them to
identify such cases. Previously RTT sampler was called only if
FLAG_RETRANS_DATA_ACKED was not set filtering inaccurate
timestamps nicely. In addition, the new behavior could give an
invalid timestamp (zero) to RTT sampler if only skbs with
TCPCB_RETRANS were ACKed. This solves both problems.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>
2007-06-15 15:08:43 -07:00
YOSHIFUJI Hideaki 84299b3bc4 [TCP]: Fix linkage errors on i386.
To avoid raw division, use ktime_to_timeval() to get usec.

Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
2007-04-25 22:29:49 -07:00
Stephen Hemminger 7752237e9f [TCP] TCP YEAH: Use vegas dont copy it.
Rather than using a copy of vegas code, the YEAH code should just have
it exported so there is common code.

Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
2007-04-25 22:29:46 -07:00
Stephen Hemminger 164891aadf [TCP]: Congestion control API update.
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 22:29:45 -07:00
Thomas Graf e9195d677d [TCP] vegas: Use type safe netlink interface
Signed-off-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
2007-04-25 22:27:26 -07:00
YOSHIFUJI Hideaki e905a9edab [NET] IPV4: Fix whitespace errors.
Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
2007-02-10 23:19:39 -08:00
David S. Miller d2e4bdc870 [TCP] Vegas: Increase default alpha to 2 and beta to 4.
This helps Vegas cope better with delayed ACKs, see
analysis at:

http://www.cs.caltech.edu/%7Eweixl/technical/ns2linux/known_linux/index.html#vegas

Signed-off-by: David S. Miller <davem@davemloft.net>
2006-12-02 21:31:03 -08:00
Alexey Dobriyan 74975d40b1 [TCP] Congestion control (modulo lp, bic): use BUILD_BUG_ON
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2006-09-22 15:18:13 -07:00
Jörn Engel 6ab3d5624e Remove obsolete #include <linux/config.h>
Signed-off-by: Jörn Engel <joern@wohnheim.fh-wedel.de>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
2006-06-30 19:25:36 +02:00
Thomas Young 74cb879822 [TCP] tcp_vegas: Fix slow start
Vegas' slow start was only adding one MSS per RTT rather than one for
every ack. Slow start behavior should now match Reno.

Signed-off-by: Thomas Young <tyo@ee.mu.oz.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
2006-01-04 13:59:32 -08:00
Thomas Young 0d7bef600a [TCP] Vegas: Remove extra call to tcp_vegas_rtt_calc
Remove unneeded call to tcp_vegas_rtt_calc. The more accurate
microsecond value has already been registered prior to calling
tcp_vegas_cong_avoid.

Signed-off-by: Thomas Young <tyo@ee.mu.oz.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
2005-12-06 16:17:11 -08:00
Thomas Young 5b49561381 [TCP] Vegas: stop resetting rtt every ack
Move the resetting of rtt measurements to inside the once per RTT
block of code.

Signed-off-by: Thomas Young <tyo@ee.mu.oz.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
2005-12-06 16:16:34 -08:00
Jeff Garzik c050970a25 [PATCH] TCP: fix vegas build
Recent TCP changes broke the build.

Signed-off-by: Jeff Garzik <jgarzik@pobox.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-11-11 09:21:28 -08:00
Stephen Hemminger 7faffa1c7f [TCP]: add tcp_slow_start helper
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 17:07:24 -08:00
Arnaldo Carvalho de Melo a8c2190ee7 [INET_DIAG]: Rename tcp_diag.[ch] to inet_diag.[ch]
Next changeset will introduce net/ipv4/tcp_diag.c, moving the code that was put
transitioanlly in inet_diag.c.

Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2005-08-29 15:57:48 -07:00
Arnaldo Carvalho de Melo 73c1f4a033 [TCPDIAG]: Just rename everything to inet_diag
Next changeset will rename tcp_diag.[ch] to inet_diag.[ch].

I'm taking this longer route so as to easy review, making clear the changes
made all along the way.

Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2005-08-29 15:57:44 -07:00
Arnaldo Carvalho de Melo 6687e988d9 [ICSK]: Move TCP congestion avoidance members to icsk
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>
2005-08-29 15:56:18 -07:00
Stephen Hemminger b87d8561d8 [TCP]: Add TCP Vegas congestion control module.
TCP Vegas code modified for the new TCP infrastructure.  
Vegas now uses microsecond resolution timestamps for 
better estimation of performance over higher speed links.

Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
2005-06-23 12:27:19 -07:00