Differential D14141 Diff 40760 head/sys/netinet/cc/cc_cubic.h

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head/sys/netinet/cc/cc_cubic.h

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* SUCH DAMAGE.		* SUCH DAMAGE.
*		*
* $FreeBSD$		* $FreeBSD$
*/		*/

#ifndef _NETINET_CC_CUBIC_H_		#ifndef _NETINET_CC_CUBIC_H_
#define _NETINET_CC_CUBIC_H_		#define _NETINET_CC_CUBIC_H_

		#include <sys/limits.h>

/* Number of bits of precision for fixed point math calcs. */		/* Number of bits of precision for fixed point math calcs. */
#define CUBIC_SHIFT 8		#define CUBIC_SHIFT 8

#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

▲ Show 20 Lines • Show All 105 Lines • ▼ Show 20 Lines	cubic_k(unsigned long wmax_pkts)

/* Multiply by 2^p to undo the rebasing of s from above. */		/* Multiply by 2^p to undo the rebasing of s from above. */
return (K <<= p);		return (K <<= p);
}		}

/*		/*
* Compute the new cwnd value using an implementation of eqn 1 from the I-D.		* Compute the new cwnd value using an implementation of eqn 1 from the I-D.
* Thanks to Kip Macy for help debugging this function.		* Thanks to Kip Macy for help debugging this function.
*
* XXXLAS: Characterise bounds for overflow.
*/		*/
static __inline unsigned long		static __inline unsigned long
cubic_cwnd(int ticks_since_cong, unsigned long wmax, uint32_t smss, int64_t K)		cubic_cwnd(int ticks_since_cong, unsigned long wmax, uint32_t smss, int64_t K)
{		{
int64_t cwnd;		int64_t cwnd;

/* K is in fixed point form with CUBIC_SHIFT worth of precision. */		/* K is in fixed point form with CUBIC_SHIFT worth of precision. */

/* t - K, with CUBIC_SHIFT worth of precision. */		/* t - K, with CUBIC_SHIFT worth of precision. */
cwnd = ((int64_t)(ticks_since_cong << CUBIC_SHIFT) - (K * hz)) / hz;		cwnd = ((int64_t)(ticks_since_cong << CUBIC_SHIFT) - (K * hz)) / hz;

		/* moved this calculation up because it cannot overflow or underflow */
		cwnd = CUBIC_C_FACTOR smss;

		if (cwnd > 2097151) /* 2^21 cubed is long max */
		return INT_MAX;

		if (cwnd < -2097152) /* -2^21 cubed is long min */
		return smss;

/* (t - K)^3, with CUBIC_SHIFT^3 worth of precision. */		/* (t - K)^3, with CUBIC_SHIFT^3 worth of precision. */
cwnd = (cwnd cwnd);		cwnd = (cwnd cwnd);

/*		/*
* C(t - K)^3 + wmax		* C(t - K)^3 + wmax
* The down shift by CUBIC_SHIFT_4 is because cwnd has 4 lots of		* The down shift by CUBIC_SHIFT_4 is because cwnd has 4 lots of
* CUBIC_SHIFT included in the value. 3 from the cubing of cwnd above,		* CUBIC_SHIFT included in the value. 3 from the cubing of cwnd above,
* and an extra from multiplying through by CUBIC_C_FACTOR.		* and an extra from multiplying through by CUBIC_C_FACTOR.
		*
		* The original formula was this:
		* cwnd = ((cwnd * CUBIC_C_FACTOR * smss) >> CUBIC_SHIFT_4) + wmax;
		*
		* CUBIC_C_FACTOR and smss factors were moved up to an earlier
		* calculation to simplify overflow and underflow detection.
*/		*/
cwnd = ((cwnd * CUBIC_C_FACTOR * smss) >> CUBIC_SHIFT_4) + wmax;		cwnd = (cwnd >> CUBIC_SHIFT_4) + wmax;

		if (cwnd < 0)
		return 1;

return ((unsigned long)cwnd);		return ((unsigned long)cwnd);
}		}

/*		/*
* Compute an approximation of the NewReno cwnd some number of ticks after a		* Compute an approximation of the NewReno cwnd some number of ticks after a
* congestion event. RTT should be the average RTT estimate for the path		* congestion event. RTT should be the average RTT estimate for the path
* measured over the previous congestion epoch and wmax is the value of cwnd at		* measured over the previous congestion epoch and wmax is the value of cwnd at
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