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| author | Gerrit Renker <gerrit@erg.abdn.ac.uk> | 2008-06-11 11:19:10 +0100 |
|---|---|---|
| committer | Gerrit Renker <gerrit@erg.abdn.ac.uk> | 2008-06-11 11:19:10 +0100 |
| commit | 1e8a287c79f64226541f5c44aa52d4698bb84cf5 (patch) | |
| tree | a280516dae548981cd9c9f981cc7bd8ec879baf2 /net/dccp | |
| parent | 65907a433ac0ca450c4408080f24c6e4743386b2 (diff) | |
| download | linux-1e8a287c79f64226541f5c44aa52d4698bb84cf5.tar.bz2 | |
dccp ccid-3: TFRC reverse-lookup Bug-Fix
This fixes a bug in the reverse lookup of p: given a value f(p), instead of p,
the function returned the smallest tabulated value f(p).
The smallest tabulated value of
10^6 * f(p) = sqrt(2*p/3) + 12 * sqrt(3*p/8) * (32 * p^3 + p)
for p=0.0001 is 8172.
Since this value is scaled by 10^6, the outcome of this bug is that a loss
of 8172/10^6 = 0.8172% was reported whenever the input was below the table
resolution of 0.01%.
This means that the value was over 80 times too high, resulting in large spikes
of the initial loss interval, thus unnecessarily reducing the throughput.
Also corrected the printk format (%u for u32).
Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Diffstat (limited to 'net/dccp')
| -rw-r--r-- | net/dccp/ccids/lib/tfrc_equation.c | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/net/dccp/ccids/lib/tfrc_equation.c b/net/dccp/ccids/lib/tfrc_equation.c index e4e64b76c10c..2f20a29cffe4 100644 --- a/net/dccp/ccids/lib/tfrc_equation.c +++ b/net/dccp/ccids/lib/tfrc_equation.c @@ -661,7 +661,7 @@ u32 tfrc_calc_x(u16 s, u32 R, u32 p) EXPORT_SYMBOL_GPL(tfrc_calc_x); -/* +/** * tfrc_calc_x_reverse_lookup - try to find p given f(p) * * @fvalue: function value to match, scaled by 1000000 @@ -676,11 +676,11 @@ u32 tfrc_calc_x_reverse_lookup(u32 fvalue) /* Error cases. */ if (fvalue < tfrc_calc_x_lookup[0][1]) { - DCCP_WARN("fvalue %d smaller than resolution\n", fvalue); - return tfrc_calc_x_lookup[0][1]; + DCCP_WARN("fvalue %u smaller than resolution\n", fvalue); + return TFRC_SMALLEST_P; } if (fvalue > tfrc_calc_x_lookup[TFRC_CALC_X_ARRSIZE - 1][0]) { - DCCP_WARN("fvalue %d exceeds bounds!\n", fvalue); + DCCP_WARN("fvalue %u exceeds bounds!\n", fvalue); return 1000000; } |