Function rte_red_enqueue_nonempty

dpdk/lib/sched/rte_red.h:312–356

* @brief Decides if new packet should be enqueued or dropped in queue non-empty case * * @param red_cfg [in] config pointer to a RED configuration parameter structure * @param red [in,out] data pointer to RED runtime data * @param q [in] current queue size (measured in packets) * * @return Operation status * @retval 0 enqueue the packet * @retval 1 drop the packet based on max threshold cr

 * @retval 2 drop the packet based on mark probability criterion
 */
static inline int
rte_red_enqueue_nonempty(const struct rte_red_config *red_cfg,
	struct rte_red *red,
	const unsigned q)
{
	RTE_ASSERT(red_cfg != NULL);
	RTE_ASSERT(red != NULL);

	/**
	* EWMA filter (Sally Floyd and Van Jacobson):
	*    avg = (1 - wq) * avg + wq * q
	*    avg = avg + q * wq - avg * wq
	*
	* We select: wq = 2^(-n). Let scaled version of avg be: avg_s = avg * 2^(N+n). We get:
	*    avg_s = avg_s + q * 2^N - avg_s * 2^(-n)
	*
	* By using shift left/right operations, we get:
	*    avg_s = avg_s + (q << N) - (avg_s >> n)
	*    avg_s += (q << N) - (avg_s >> n)
	*/

	/* avg update */
	red->avg += (q << RTE_RED_SCALING) - (red->avg >> red_cfg->wq_log2);

	/* avg < min_th: do not mark the packet  */
	if (red->avg < red_cfg->min_th) {
		red->count ++;
		return 0;
	}

	/* min_th <= avg < max_th: mark the packet with pa probability */
	if (red->avg < red_cfg->max_th) {
		if (!__rte_red_drop(red_cfg, red)) {
			red->count ++;
			return 0;
		}

		red->count = 0;
		return 2;
	}

	/* max_th <= avg: always mark the packet */
	red->count = 0;
	return 1;
}

/**
 * @brief Decides if new packet should be enqueued or dropped