linux-toradex.git/net/ipv4/tcp_cubic.c, branch v3.0.9

tcp_cubic: limit delayed_ack ratio to prevent divide error

2011-05-08T22:51:57+00:00

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 
Signed-off-by: David S. Miller

Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6

2011-03-15T22:15:17+00:00

tcp_cubic: fix low utilization of CUBIC with HyStart

2011-03-14T22:54:42+00:00

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 
Acked-by: Stephen Hemminger 
Signed-off-by: David S. Miller

tcp_cubic: make the delay threshold of HyStart less sensitive

2011-03-14T22:54:42+00:00

Make HyStart less sensitive to abrupt delay variations due to buffer bloat.

Signed-off-by: Sangtae Ha 
Acked-by: Stephen Hemminger 
Reported-by: Lucas Nussbaum 
Signed-off-by: David S. Miller

tcp_cubic: enable high resolution ack time if needed

2011-03-14T22:54:40+00:00

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 
Reported-by: Lucas Nussbaum 
Signed-off-by: David S. Miller

tcp_cubic: fix clock dependency

2011-03-14T22:54:39+00:00

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 
Reported-by: Lucas Nussbaum 
Signed-off-by: David S. Miller

tcp_cubic: make ack train delta value a parameter

2011-03-14T22:54:39+00:00

Make the spacing between ACK's that indicates a train a tuneable
value like other hystart values.

Signed-off-by: Stephen Hemminger 
Signed-off-by: David S. Miller

tcp_cubic: fix comparison of jiffies

2011-03-14T22:54:38+00:00

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 
Signed-off-by: David S. Miller

tcp: mark tcp_congestion_ops read_mostly

2011-03-10T08:40:17+00:00

Signed-off-by: Stephen Hemminger 
Signed-off-by: David S. Miller

tcp: add helper for AI algorithm

2009-03-02T11:00:15+00:00

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 
Signed-off-by: David S. Miller