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sys/netinet/cc/cc_cubic.h

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#define CUBIC_SHIFT_4 32 #define CUBIC_SHIFT_4 32
/* 0.5 << CUBIC_SHIFT. */ /* 0.5 << CUBIC_SHIFT. */
#define RENO_BETA 128 #define RENO_BETA 128
/* ~0.7 << CUBIC_SHIFT. */ /* ~0.7 << CUBIC_SHIFT. */
#define CUBIC_BETA 179 #define CUBIC_BETA 179
/* ~0.53 << CUBIC_SHIFT: 3 * (1-beta_cubic)/(1+beta_cubic). */
#define CUBIC_ALPHA 135
/* 1 << CUBIC_SHIFT. */
#define CUBIC_ALPHA_ONE 256
/* ~0.3 << CUBIC_SHIFT. */ /* ~0.3 << CUBIC_SHIFT. */
#define ONE_SUB_CUBIC_BETA 77 #define ONE_SUB_CUBIC_BETA 77
/* 3 * ONE_SUB_CUBIC_BETA. */ /* 3 * ONE_SUB_CUBIC_BETA. */
#define THREE_X_PT3 231 #define THREE_X_PT3 231
/* (2 << CUBIC_SHIFT) - ONE_SUB_CUBIC_BETA. */ /* (2 << CUBIC_SHIFT) - ONE_SUB_CUBIC_BETA. */
#define TWO_SUB_PT3 435 #define TWO_SUB_PT3 435
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/* Userland only bits. */ /* Userland only bits. */
#ifndef _KERNEL #ifndef _KERNEL
extern int hz; extern int hz;
/* /*
* Implementation based on the formulae found in the CUBIC Internet Draft * Implementation based on the formulae found in the CUBIC Internet Draft
* "draft-ietf-tcpm-cubic-04". * "draft-ietf-tcpm-rfc8312bis-15".
* *
*/ */
static __inline float static __inline float
theoretical_cubic_k(double wmax_pkts) theoretical_cubic_k(double wmax_pkts, double cwnd_epoch_pkts)
{ {
double C; double C;
C = 0.4; C = 0.4;
return (pow((wmax_pkts * 0.3) / C, (1.0 / 3.0)) * pow(2, CUBIC_SHIFT)); if (wmax_pkts <= cwnd_epoch_pkts)
return 0.0;
return (pow((wmax_pkts - cwnd_epoch_pkts) / C, (1.0 / 3.0)) * pow(2, CUBIC_SHIFT));
} }
static __inline unsigned long static __inline unsigned long
theoretical_cubic_cwnd(int ticks_since_epoch, unsigned long wmax, uint32_t smss) theoretical_cubic_cwnd(int ticks_since_epoch, unsigned long wmax,
unsigned long cwnd_epoch, uint32_t smss)
{ {
double C, wmax_pkts; double C, wmax_pkts, cwnd_epoch_pkts;
C = 0.4; C = 0.4;
wmax_pkts = wmax / (double)smss; wmax_pkts = wmax / (double)smss;
cwnd_epoch_pkts = cwnd_epoch / (double)smss;
return (smss * (wmax_pkts + return (smss * (wmax_pkts +
(C * pow(ticks_since_epoch / (double)hz - (C * pow(ticks_since_epoch / (double)hz -
theoretical_cubic_k(wmax_pkts) / pow(2, CUBIC_SHIFT), 3.0)))); theoretical_cubic_k(wmax_pkts, cwnd_epoch_pkts) / pow(2, CUBIC_SHIFT), 3.0))));
} }
static __inline unsigned long static __inline unsigned long
theoretical_reno_cwnd(int ticks_since_epoch, int rtt_ticks, unsigned long wmax, theoretical_reno_cwnd(int ticks_since_epoch, int rtt_ticks, unsigned long wmax,
uint32_t smss) uint32_t smss)
{ {
return ((wmax * 0.5) + ((ticks_since_epoch / (float)rtt_ticks) * smss)); return ((wmax * 0.5) + ((ticks_since_epoch / (float)rtt_ticks) * smss));
} }
static __inline unsigned long static __inline unsigned long
theoretical_tf_cwnd(int ticks_since_epoch, int rtt_ticks, unsigned long wmax, theoretical_tf_cwnd(unsigned long west, unsigned long bytes_acked, unsigned long cwnd,
uint32_t smss) unsigned long cwnd_prior, unsigned long smss)
{ {
return ((wmax * 0.7) + ((3 * 0.3) / (2 - 0.3) * float cubic_alpha;
(ticks_since_epoch / (float)rtt_ticks) * smss));
if (west >= cwnd_prior)
cubic_alpha = 1.0;
else
cubic_alpha = (3.0 * (1.0 - 0.7)) / (1.0 + 0.7);
return (west + (cubic_alpha * ((bytes_acked * smss) / (float)cwnd)));
} }
#endif /* !_KERNEL */ #endif /* !_KERNEL */
/* /*
* Compute the CUBIC K value used in the cwnd calculation, using an * Compute the CUBIC K value used in the cwnd calculation, using an
* implementation of eqn 2 in the I-D. The method used * implementation mentioned in Fig. 2 of draft-ietf-tcpm-rfc8312bis-15.
* here is adapted from Apple Computer Technical Report #KT-32. * The method used here is adapted from Apple Computer Technical
* Report #KT-32.
*/ */
static __inline int64_t static __inline int64_t
cubic_k(unsigned long wmax_pkts) cubic_k(unsigned long wmax_pkts, unsigned long cwnd_epoch_pkts)
{ {
int64_t s, K; int64_t s, K;
uint16_t p; uint16_t p;
K = s = 0; K = s = 0;
p = 0; p = 0;
/* (wmax * beta)/C with CUBIC_SHIFT worth of precision. */ /* Handle the corner case where W_max <= cwnd_epoch */
s = ((wmax_pkts * ONE_SUB_CUBIC_BETA) << CUBIC_SHIFT) / CUBIC_C_FACTOR; if (wmax_pkts <= cwnd_epoch_pkts) {
return 0;
}
/* (wmax - cwnd_epoch) / C with CUBIC_SHIFT worth of precision. */
s = ((wmax_pkts - cwnd_epoch_pkts) << (2 * CUBIC_SHIFT)) / CUBIC_C_FACTOR;
/* Rebase s to be between 1 and 1/8 with a shift of CUBIC_SHIFT. */ /* Rebase s to be between 1 and 1/8 with a shift of CUBIC_SHIFT. */
while (s >= 256) { while (s >= 256) {
s >>= 3; s >>= 3;
p++; p++;
} }
/* /*
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