rte_red.h

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/* SPDX-License-Identifier: BSD-3-Clause
 * Copyright(c) 2010-2014 Intel Corporation
 */
 
#ifndef __RTE_RED_H_INCLUDED__
#define __RTE_RED_H_INCLUDED__

 
#include <stdint.h>
#include <limits.h>
#include <rte_debug.h>
#include <rte_cycles.h>
#include <rte_branch_prediction.h>
 
#ifdef __cplusplus
extern "C" {
#endif
 
#define RTE_RED_SCALING                     10         
#define RTE_RED_S                           (1 << 22)  
#define RTE_RED_MAX_TH_MAX                  1023       
#define RTE_RED_WQ_LOG2_MIN                 1          
#define RTE_RED_WQ_LOG2_MAX                 12         
#define RTE_RED_MAXP_INV_MIN                1          
#define RTE_RED_MAXP_INV_MAX                255        
#define RTE_RED_2POW16                      (1<<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)

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];

struct rte_red_params {
    uint16_t min_th;   
    uint16_t max_th;   
    uint16_t maxp_inv; 
    uint16_t wq_log2;  
};

struct rte_red_config {
    uint32_t min_th;   
    uint32_t max_th;   
    uint32_t pa_const; 
    uint8_t maxp_inv;  
    uint8_t wq_log2;   
};

struct rte_red {
    uint32_t avg;      
    uint32_t count;    
    uint64_t q_time;   
};

int
rte_red_rt_data_init(struct rte_red *red);

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);

static inline uint32_t
rte_fast_rand(void)
{
    rte_red_rand_seed = (214013 * rte_red_rand_seed) + 2531011;
    return rte_red_rand_seed >> 10;
}

static inline uint16_t
__rte_red_calc_qempty_factor(uint8_t wq_log2, uint16_t m)
{
    uint32_t n = 0;
    uint32_t f = 0;

 
    n = m * rte_red_log2_1_minus_Wq[wq_log2 - RTE_RED_WQ_LOG2_MIN];

 
    f = (n >> 6) & 0xf;
    n >>= 10;
 
    if (n < RTE_RED_SCALING) {
        /* When n == 0, no rounding or shifting needed.
         * For n > 0, add 2^(n-1) for rounding before right shift.
         * This avoids UB from (1 << -1) when n == 0.
         */
        if (n == 0)
            return (uint16_t) rte_red_pow2_frac_inv[f];
        return (uint16_t) ((rte_red_pow2_frac_inv[f] + (1 << (n - 1))) >> n);
    }
 
    return 0;
}

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_ASSERT(red_cfg != NULL);
    RTE_ASSERT(red != NULL);
 
    red->count ++;

    time_diff = time - red->q_time;

    m = time_diff / RTE_RED_S;

    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;
}


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;
}

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);

 
    /* 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;
}

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_ASSERT(red_cfg != NULL);
    RTE_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);
    }
}

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__ */