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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: Adrian Bunk <bunk@stusta.de>
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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>
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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>
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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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