From 1e8a287c79f64226541f5c44aa52d4698bb84cf5 Mon Sep 17 00:00:00 2001 From: Gerrit Renker Date: Wed, 11 Jun 2008 11:19:10 +0100 Subject: [PATCH] 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 --- net/dccp/ccids/lib/tfrc_equation.c | 8 ++++---- 1 file 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; }