Differential D6442 Diff 65979 sys/netinet/cc/cc_cdg.c

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sys/netinet/cc/cc_cdg.c

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	* probability of backoff over time.			* probability of backoff over time.
	*			*
	* Prob_backoff = 1 - exp(-qtrend / V_cdg_exp_backoff_scale), where			* Prob_backoff = 1 - exp(-qtrend / V_cdg_exp_backoff_scale), where
	* V_cdg_exp_backoff_scale is the average qtrend for the exponential backoff.			* V_cdg_exp_backoff_scale is the average qtrend for the exponential backoff.
	*/			*/
	static inline int			static inline int
	prob_backoff(long qtrend)			prob_backoff(long qtrend)
	{			{
	int backoff, idx, p;			u_int backoff, idx, p;
				cemUnsubmitted Not Done Inline Actions I am hesitant to make type changes like this. They’re unrelated to using arc4random. cem: I am hesitant to make type changes like this. They’re unrelated to using arc4random.

	backoff = (qtrend > ((MAXGRAD * V_cdg_exp_backoff_scale) << D_P_E));			backoff = (qtrend > ((MAXGRAD * V_cdg_exp_backoff_scale) << D_P_E));

	if (!backoff) {			if (!backoff) {
	if (V_cdg_exp_backoff_scale > 1)			if (V_cdg_exp_backoff_scale > 1)
	idx = (qtrend + V_cdg_exp_backoff_scale / 2) /			idx = (qtrend + V_cdg_exp_backoff_scale / 2) /
	V_cdg_exp_backoff_scale;			V_cdg_exp_backoff_scale;
	else			else
	idx = qtrend;			idx = qtrend;

	/* Backoff probability proportional to rate of queue growth. */			/* Backoff probability proportional to rate of queue growth. */
	p = (INT_MAX / (1 << EXP_PREC)) * probexp[idx];			p = (UINT_MAX / (1 << EXP_PREC)) * probexp[idx];
	backoff = (random() < p);			backoff = (arc4random() < p);
				cemUnsubmitted Not Done Inline Actions This is now a completely different expression in a way that has nothing to do with s/random/arc4random/. Ditto earlier concerns about not being an expert in this code; I don’t know how significant unpredictability is in this context. cem: This is now a completely different expression in a way that has nothing to do with…
				pfgAuthorUnsubmitted Done Inline Actions The real change happens in the comparison in the next line. Yes, the change is tricky and has been moved to its own differential: D22924 pfg: The real change happens in the comparison in the next line. Yes, the change is tricky and has…
	}			}

	return (backoff);			return (backoff);
	}			}

	static inline void			static inline void
	calc_moving_average(struct cdg *cdg_data, long qdiff_max, long qdiff_min)			calc_moving_average(struct cdg *cdg_data, long qdiff_max, long qdiff_min)
	{			{
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