--- /dev/null
+/*-
+ * BSD LICENSE
+ *
+ * Copyright(c) 2010-2014 Intel Corporation. All rights reserved.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * * Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in
+ * the documentation and/or other materials provided with the
+ * distribution.
+ * * Neither the name of Intel Corporation nor the names of its
+ * contributors may be used to endorse or promote products derived
+ * from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef __RTE_RED_H_INCLUDED__
+#define __RTE_RED_H_INCLUDED__
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @file
+ * RTE Random Early Detection (RED)
+ *
+ *
+ ***/
+
+#include <stdint.h>
+#include <limits.h>
+#include <rte_common.h>
+#include <rte_debug.h>
+#include <rte_cycles.h>
+#include <rte_branch_prediction.h>
+
+#define RTE_RED_SCALING 10 /**< Fraction size for fixed-point */
+#define RTE_RED_S (1 << 22) /**< Packet size multiplied by number of leaf queues */
+#define RTE_RED_MAX_TH_MAX 1023 /**< Max threshold limit in fixed point format */
+#define RTE_RED_WQ_LOG2_MIN 1 /**< Min inverse filter weight value */
+#define RTE_RED_WQ_LOG2_MAX 12 /**< Max inverse filter weight value */
+#define RTE_RED_MAXP_INV_MIN 1 /**< Min inverse mark probability value */
+#define RTE_RED_MAXP_INV_MAX 255 /**< Max inverse mark probability value */
+#define RTE_RED_2POW16 (1<<16) /**< 2 power 16 */
+#define RTE_RED_INT16_NBITS (sizeof(uint16_t) * CHAR_BIT)
+#define RTE_RED_WQ_LOG2_NUM (RTE_RED_WQ_LOG2_MAX - RTE_RED_WQ_LOG2_MIN + 1)
+
+#ifdef RTE_RED_DEBUG
+
+#define RTE_RED_ASSERT(exp) \
+if (!(exp)) { \
+ rte_panic("line%d\tassert \"" #exp "\" failed\n", __LINE__); \
+}
+
+#else
+
+#define RTE_RED_ASSERT(exp) do { } while(0)
+
+#endif /* RTE_RED_DEBUG */
+
+/**
+ * Externs
+ *
+ */
+extern uint32_t rte_red_rand_val;
+extern uint32_t rte_red_rand_seed;
+extern uint16_t rte_red_log2_1_minus_Wq[RTE_RED_WQ_LOG2_NUM];
+extern uint16_t rte_red_pow2_frac_inv[16];
+
+/**
+ * RED configuration parameters passed by user
+ *
+ */
+struct rte_red_params {
+ uint16_t min_th; /**< Minimum threshold for queue (max_th) */
+ uint16_t max_th; /**< Maximum threshold for queue (max_th) */
+ uint16_t maxp_inv; /**< Inverse of packet marking probability maximum value (maxp = 1 / maxp_inv) */
+ uint16_t wq_log2; /**< Negated log2 of queue weight (wq = 1 / (2 ^ wq_log2)) */
+};
+
+/**
+ * RED configuration parameters
+ */
+struct rte_red_config {
+ uint32_t min_th; /**< min_th scaled in fixed-point format */
+ uint32_t max_th; /**< max_th scaled in fixed-point format */
+ uint32_t pa_const; /**< Precomputed constant value used for pa calculation (scaled in fixed-point format) */
+ uint8_t maxp_inv; /**< maxp_inv */
+ uint8_t wq_log2; /**< wq_log2 */
+};
+
+/**
+ * RED run-time data
+ */
+struct rte_red {
+ uint32_t avg; /**< Average queue size (avg), scaled in fixed-point format */
+ uint32_t count; /**< Number of packets since last marked packet (count) */
+ uint64_t q_time; /**< Start of the queue idle time (q_time) */
+};
+
+/**
+ * @brief Initialises run-time data
+ *
+ * @param red [in,out] data pointer to RED runtime data
+ *
+ * @return Operation status
+ * @retval 0 success
+ * @retval !0 error
+ */
+int
+rte_red_rt_data_init(struct rte_red *red);
+
+/**
+ * @brief Configures a single RED configuration parameter structure.
+ *
+ * @param red_cfg [in,out] config pointer to a RED configuration parameter structure
+ * @param wq_log2 [in] log2 of the filter weight, valid range is:
+ * RTE_RED_WQ_LOG2_MIN <= wq_log2 <= RTE_RED_WQ_LOG2_MAX
+ * @param min_th [in] queue minimum threshold in number of packets
+ * @param max_th [in] queue maximum threshold in number of packets
+ * @param maxp_inv [in] inverse maximum mark probability
+ *
+ * @return Operation status
+ * @retval 0 success
+ * @retval !0 error
+ */
+int
+rte_red_config_init(struct rte_red_config *red_cfg,
+ const uint16_t wq_log2,
+ const uint16_t min_th,
+ const uint16_t max_th,
+ const uint16_t maxp_inv);
+
+/**
+ * @brief Generate random number for RED
+ *
+ * Implemenetation based on:
+ * http://software.intel.com/en-us/articles/fast-random-number-generator-on-the-intel-pentiumr-4-processor/
+ *
+ * 10 bit shift has been found through empirical tests (was 16).
+ *
+ * @return Random number between 0 and (2^22 - 1)
+ */
+static inline uint32_t
+rte_fast_rand(void)
+{
+ rte_red_rand_seed = (214013 * rte_red_rand_seed) + 2531011;
+ return rte_red_rand_seed >> 10;
+}
+
+/**
+ * @brief calculate factor to scale average queue size when queue
+ * becomes empty
+ *
+ * @param wq_log2 [in] where EWMA filter weight wq = 1/(2 ^ wq_log2)
+ * @param m [in] exponent in the computed value (1 - wq) ^ m
+ *
+ * @return computed value
+ * @retval ((1 - wq) ^ m) scaled in fixed-point format
+ */
+static inline uint16_t
+__rte_red_calc_qempty_factor(uint8_t wq_log2, uint16_t m)
+{
+ uint32_t n = 0;
+ uint32_t f = 0;
+
+ /**
+ * Basic math tells us that:
+ * a^b = 2^(b * log2(a) )
+ *
+ * in our case:
+ * a = (1-Wq)
+ * b = m
+ * Wq = 1/ (2^log2n)
+ *
+ * So we are computing this equation:
+ * factor = 2 ^ ( m * log2(1-Wq))
+ *
+ * First we are computing:
+ * n = m * log2(1-Wq)
+ *
+ * To avoid dealing with signed numbers log2 values are positive
+ * but they should be negative because (1-Wq) is always < 1.
+ * Contents of log2 table values are also scaled for precision.
+ */
+
+ n = m * rte_red_log2_1_minus_Wq[wq_log2 - RTE_RED_WQ_LOG2_MIN];
+
+ /**
+ * The tricky part is computing 2^n, for this I split n into
+ * integer part and fraction part.
+ * f - is fraction part of n
+ * n - is integer part of original n
+ *
+ * Now using basic math we compute 2^n:
+ * 2^(f+n) = 2^f * 2^n
+ * 2^f - we use lookup table
+ * 2^n - can be replaced with bit shift right oeprations
+ */
+
+ f = (n >> 6) & 0xf;
+ n >>= 10;
+
+ if (n < RTE_RED_SCALING)
+ return (uint16_t) ((rte_red_pow2_frac_inv[f] + (1 << (n - 1))) >> n);
+
+ return 0;
+}
+
+/**
+ * @brief Updates queue average in condition when queue is empty
+ *
+ * Note: packet is never dropped in this particular case.
+ *
+ * @param red_cfg [in] config pointer to a RED configuration parameter structure
+ * @param red [in,out] data pointer to RED runtime data
+ * @param time [in] current time stamp
+ *
+ * @return Operation status
+ * @retval 0 enqueue the packet
+ * @retval 1 drop the packet based on max threshold criterion
+ * @retval 2 drop the packet based on mark probability criterion
+ */
+static inline int
+rte_red_enqueue_empty(const struct rte_red_config *red_cfg,
+ struct rte_red *red,
+ const uint64_t time)
+{
+ uint64_t time_diff = 0, m = 0;
+
+ RTE_RED_ASSERT(red_cfg != NULL);
+ RTE_RED_ASSERT(red != NULL);
+
+ red->count ++;
+
+ /**
+ * We compute avg but we don't compare avg against
+ * min_th or max_th, nor calculate drop probability
+ */
+ time_diff = time - red->q_time;
+
+ /**
+ * m is the number of packets that might have arrived while the queue was empty.
+ * In this case we have time stamps provided by scheduler in byte units (bytes
+ * transmitted on network port). Such time stamp translates into time units as
+ * port speed is fixed but such approach simplifies the code.
+ */
+ m = time_diff / RTE_RED_S;
+
+ /**
+ * Check that m will fit into 16-bit unsigned integer
+ */
+ if (m >= RTE_RED_2POW16) {
+ red->avg = 0;
+ } else {
+ red->avg = (red->avg >> RTE_RED_SCALING) * __rte_red_calc_qempty_factor(red_cfg->wq_log2, (uint16_t) m);
+ }
+
+ return 0;
+}
+
+/**
+ * Drop probability (Sally Floyd and Van Jacobson):
+ *
+ * pb = (1 / maxp_inv) * (avg - min_th) / (max_th - min_th)
+ * pa = pb / (2 - count * pb)
+ *
+ *
+ * (1 / maxp_inv) * (avg - min_th)
+ * ---------------------------------
+ * max_th - min_th
+ * pa = -----------------------------------------------
+ * count * (1 / maxp_inv) * (avg - min_th)
+ * 2 - -----------------------------------------
+ * max_th - min_th
+ *
+ *
+ * avg - min_th
+ * pa = -----------------------------------------------------------
+ * 2 * (max_th - min_th) * maxp_inv - count * (avg - min_th)
+ *
+ *
+ * We define pa_const as: pa_const = 2 * (max_th - min_th) * maxp_inv. Then:
+ *
+ *
+ * avg - min_th
+ * pa = -----------------------------------
+ * pa_const - count * (avg - min_th)
+ */
+
+/**
+ * @brief make a decision to drop or enqueue a packet based on mark probability
+ * criteria
+ *
+ * @param red_cfg [in] config pointer to structure defining RED parameters
+ * @param red [in,out] data pointer to RED runtime data
+ *
+ * @return operation status
+ * @retval 0 enqueue the packet
+ * @retval 1 drop the packet
+ */
+static inline int
+__rte_red_drop(const struct rte_red_config *red_cfg, struct rte_red *red)
+{
+ uint32_t pa_num = 0; /* numerator of drop-probability */
+ uint32_t pa_den = 0; /* denominator of drop-probability */
+ uint32_t pa_num_count = 0;
+
+ pa_num = (red->avg - red_cfg->min_th) >> (red_cfg->wq_log2);
+
+ pa_num_count = red->count * pa_num;
+
+ if (red_cfg->pa_const <= pa_num_count)
+ return 1;
+
+ pa_den = red_cfg->pa_const - pa_num_count;
+
+ /* If drop, generate and save random number to be used next time */
+ if (unlikely((rte_red_rand_val % pa_den) < pa_num)) {
+ rte_red_rand_val = rte_fast_rand();
+
+ return 1;
+ }
+
+ /* No drop */
+ return 0;
+}
+
+/**
+ * @brief Decides if new packet should be enqeued 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 criterion
+ * @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_RED_ASSERT(red_cfg != NULL);
+ RTE_RED_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 enqeued or dropped
+ * Updates run time data based on new queue size value.
+ * Based on new queue average and RED configuration parameters
+ * gives verdict whether to enqueue or drop the packet.
+ *
+ * @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] updated queue size in packets
+ * @param time [in] current time stamp
+ *
+ * @return Operation status
+ * @retval 0 enqueue the packet
+ * @retval 1 drop the packet based on max threshold criteria
+ * @retval 2 drop the packet based on mark probability criteria
+ */
+static inline int
+rte_red_enqueue(const struct rte_red_config *red_cfg,
+ struct rte_red *red,
+ const unsigned q,
+ const uint64_t time)
+{
+ RTE_RED_ASSERT(red_cfg != NULL);
+ RTE_RED_ASSERT(red != NULL);
+
+ if (q != 0) {
+ return rte_red_enqueue_nonempty(red_cfg, red, q);
+ } else {
+ return rte_red_enqueue_empty(red_cfg, red, time);
+ }
+}
+
+/**
+ * @brief Callback to records time that queue became empty
+ *
+ * @param red [in,out] data pointer to RED runtime data
+ * @param time [in] current time stamp
+ */
+static inline void
+rte_red_mark_queue_empty(struct rte_red *red, const uint64_t time)
+{
+ red->q_time = time;
+}
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* __RTE_RED_H_INCLUDED__ */
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