diff options
Diffstat (limited to 'net/dccp/ccids/lib/tfrc_equation.c')
| -rw-r--r-- | net/dccp/ccids/lib/tfrc_equation.c | 50 |
1 files changed, 29 insertions, 21 deletions
diff --git a/net/dccp/ccids/lib/tfrc_equation.c b/net/dccp/ccids/lib/tfrc_equation.c index e4e64b76c10..88ef98285be 100644 --- a/net/dccp/ccids/lib/tfrc_equation.c +++ b/net/dccp/ccids/lib/tfrc_equation.c @@ -1,6 +1,4 @@ /* - * net/dccp/ccids/lib/tfrc_equation.c - * * Copyright (c) 2005 The University of Waikato, Hamilton, New Zealand. * Copyright (c) 2005 Ian McDonald <ian.mcdonald@jandi.co.nz> * Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@conectiva.com.br> @@ -79,10 +77,10 @@ } With the given configuration, we have, with M = TFRC_CALC_X_ARRSIZE-1, - lookup[0][0] = g(1000000/(M+1)) = 1000000 * f(0.2%) - lookup[M][0] = g(1000000) = 1000000 * f(100%) - lookup[0][1] = g(TFRC_SMALLEST_P) = 1000000 * f(0.01%) - lookup[M][1] = g(TFRC_CALC_X_SPLIT) = 1000000 * f(5%) + lookup[0][0] = g(1000000/(M+1)) = 1000000 * f(0.2%) + lookup[M][0] = g(1000000) = 1000000 * f(100%) + lookup[0][1] = g(TFRC_SMALLEST_P) = 1000000 * f(0.01%) + lookup[M][1] = g(TFRC_CALC_X_SPLIT) = 1000000 * f(5%) In summary, the two columns represent f(p) for the following ranges: * The first column is for 0.002 <= p <= 1.0 @@ -610,11 +608,11 @@ static inline u32 tfrc_binsearch(u32 fval, u8 small) /** * tfrc_calc_x - Calculate the send rate as per section 3.1 of RFC3448 + * @s: packet size in bytes + * @R: RTT scaled by 1000000 (i.e., microseconds) + * @p: loss ratio estimate scaled by 1000000 * - * @s: packet size in bytes - * @R: RTT scaled by 1000000 (i.e., microseconds) - * @p: loss ratio estimate scaled by 1000000 - * Returns X_calc in bytes per second (not scaled). + * Returns X_calc in bytes per second (not scaled). */ u32 tfrc_calc_x(u16 s, u32 R, u32 p) { @@ -630,17 +628,17 @@ u32 tfrc_calc_x(u16 s, u32 R, u32 p) return ~0U; } - if (p <= TFRC_CALC_X_SPLIT) { /* 0.0000 < p <= 0.05 */ + if (p <= TFRC_CALC_X_SPLIT) { /* 0.0000 < p <= 0.05 */ if (p < TFRC_SMALLEST_P) { /* 0.0000 < p < 0.0001 */ DCCP_WARN("Value of p (%d) below resolution. " "Substituting %d\n", p, TFRC_SMALLEST_P); index = 0; - } else /* 0.0001 <= p <= 0.05 */ + } else /* 0.0001 <= p <= 0.05 */ index = p/TFRC_SMALLEST_P - 1; f = tfrc_calc_x_lookup[index][1]; - } else { /* 0.05 < p <= 1.00 */ + } else { /* 0.05 < p <= 1.00 */ index = p/(1000000/TFRC_CALC_X_ARRSIZE) - 1; f = tfrc_calc_x_lookup[index][0]; @@ -659,12 +657,10 @@ u32 tfrc_calc_x(u16 s, u32 R, u32 p) return scaled_div32(result, f); } -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 + * * Returns closest match for p, also scaled by 1000000 */ u32 tfrc_calc_x_reverse_lookup(u32 fvalue) @@ -676,11 +672,11 @@ 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; } @@ -694,4 +690,16 @@ u32 tfrc_calc_x_reverse_lookup(u32 fvalue) return (index + 1) * 1000000 / TFRC_CALC_X_ARRSIZE; } -EXPORT_SYMBOL_GPL(tfrc_calc_x_reverse_lookup); +/** + * tfrc_invert_loss_event_rate - Compute p so that 10^6 corresponds to 100% + * When @loss_event_rate is large, there is a chance that p is truncated to 0. + * To avoid re-entering slow-start in that case, we set p = TFRC_SMALLEST_P > 0. + */ +u32 tfrc_invert_loss_event_rate(u32 loss_event_rate) +{ + if (loss_event_rate == UINT_MAX) /* see RFC 4342, 8.5 */ + return 0; + if (unlikely(loss_event_rate == 0)) /* map 1/0 into 100% */ + return 1000000; + return max_t(u32, scaled_div(1, loss_event_rate), TFRC_SMALLEST_P); +} |