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>
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>
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>
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>
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>
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>
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>
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.pnghttp://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>
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>
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>
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>
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>
