DPDK 17.11.1-执行基于目标的速率限制时会出现掉线

如何解决DPDK 17.11.1-执行基于目标的速率限制时会出现掉线

编辑问题说明以突出显示核心逻辑上的更多信息

进行基于目标的速率限制时，我们发现性能问题。我们为每个{destination-src}对保持状态（最多100个目的地和2 ^ 16个源）。我们有一个由100个节点组成的数组，在每个节点上都有一个rte_hash *。该哈希表将维护该目标看到的每个源ip的状态。我们为看到的每个目标（从0到100）都有一个映射，该映射用于索引数组。如果特定来源在一秒钟内超过为此目的地定义的阈值，则我们将阻止该来源，否则我们将允许该来源。在运行时，当我们仅看到2或3个目的地的流量时，就没有问题，但是当流量超过5时，就会看到很多掉线。我们的函数必须进行查找并标识与dest_ip和src_ip相匹配的流。处理流程并确定是否需要删除。如果未找到流，则将其添加到哈希中。

struct flow_state {
    struct rte_hash* hash;    
};

struct flow_state flow_state_arr[100];

//将要在pipeline_init中使用rte_hash_create创建这些哈希表，并在pipeline_free期间释放它们。

我概述了我们在伪代码中的工作。

run()
{
    1) do rx
    2) from the pkt,get index into the flow_state_arr and retrieve the rte_hash* handle    
    3) rte_hash_lookup_data(hash,src_ip,flow_data)
    4) if entry found,take decision on the flow (the decision is simply say rate limiting the flow)
    5) else rte_hash_add_data(hash,new_flow_data) to add the flow to table and forward
}

请指导我们是否可以在数据路径中拥有这些多个哈希表对象，或者如果我们需要分别处理每个目标的状态，那是最好的方法。

修改
谢谢回答。我将很高兴分享代码段和我们收集的结果。我没有其他DPDK版本的比较结果，但是下面是使用17.11.1。进行测试的一些结果。

测试设置
我正在使用IXIA流量生成器（使用两个10G链接生成12Mpps）用于3个目的地14.143.156.x（在这种情况下为101,102,103）。每个目的地的流量都来自2 ^ 16个不同的来源。这是流量生成器设置。

代码段

    struct flow_state_t {
        struct rte_hash* hash;
        uint32_t size;
        uint64_t threshold;
    };
    struct flow_data_t {
        uint8_t curr_state; // 0 if blocked,1 if allowed
        uint64_t pps_count;
        uint64_t src_first_seen;
    };
    struct pipeline_ratelimit {
        struct pipeline p;
        struct pipeline_ratelimit_params params;
        rte_table_hash_op_hash f_hash;
        uint32_t swap_field0_offset[SWAP_DIM];
        uint32_t swap_field1_offset[SWAP_DIM];
        uint64_t swap_field_mask[SWAP_DIM];
        uint32_t swap_n_fields;
        pipeline_msg_req_handler custom_handlers[2]; // handlers for add and del
        struct flow_state_t flow_state_arr[100];
        struct flow_data_t flows[100][65536];
    } __rte_cache_aligned;
    
    /*
      add_handler(pipeline,msg) -- msg includes index and threshold
      In the add handler
      a rule/ threshold is added for a destination
      rte_hash_create and store rte_hash* in flow_state_arr[index]
      max of 100 destinations or rules are allowed
      previous pipelines add the ID (index) to the packet to look in to the
      flow_state_arr for the rule
    */
    
    /*
      del_handler(pipeline,msg) -- msg includes index
      In the del handler
      a rule/ threshold @index is deleted
      the associated rte_hash* is also freed
      the slot is made free
    */
    
    #define ALLOWED 1
    #define BLOCKED 0
    #define TABLE_MAX_CAPACITY 65536
    int do_rate_limit(struct pipeline_ratelimit* ps,uint32_t id,unsigned char* pkt)
    {
        uint64_t curr_time_stamp = rte_get_timer_cycles();
        struct iphdr* iph = (struct iphdr*)pkt;
        uint32_t src_ip = rte_be_to_cpu_32(iph->saddr);
    
        struct flow_state_t* node = &ps->flow_state_arr[id];
        struct flow_data_t* flow = NULL
        rte_hash_lookup_data(node->hash,&src_ip,(void**)&flow);
        if (flow != NULL)
        {
            if (flow->curr_state == ALLOWED)
            {
                if (flow->pps_count++ > node->threshold)
                {
                    uint64_t seconds_elapsed = (curr_time_stamp - flow->src_first_seen) / CYCLES_IN_1SEC;
                    if (seconds_elapsed)
                    {
                        flow->src_first_seen += seconds_elapsed * CYCLES_IN_1_SEC;
                        flow->pps_count = 1;
                        return ALLOWED;
                    }
                    else
                    {
                        flow->pps_count = 0;
                        flow->curr_state = BLOCKED;
                        return BLOCKED;
                    }
                }
                return ALLOWED;
            }
            else
            {
                uint64_t seconds_elapsed = (curr_time_stamp - flow->src_first_seen) / CYCLES_IN_1SEC;
                if (seconds_elapsed > 120)
                {
                    flow->curr_state = ALLOWED;
                    flow->pps_count = 0;
                    flow->src_first_seen += seconds_elapsed * CYCLES_IN_1_SEC;
                    return ALLOWED;
                }
                return BLOCKED;
            }
        }
        int index = node->size;
        // If entry not found and we have reached capacity
        // Remove the rear element and mark it as the index for the new node    
        if (node->size == TABLE_MAX_CAPACITY)
        {
            rte_hash_reset(node->hash);
            index = node->size = 0;
        }
    
        // Add new element @packet_flows[mit_id][index]
        struct flow_data_t* flow_data = &ps->flows[id][index]; 
        *flow_data = { ALLOWED,1,curr_time_stamp };
        node->size++;
    
        // Add the new key to hash
        rte_hash_add_key_data(node->hash,(void*)&src_ip,(void*)flow_data);    
        return ALLOWED;
    }
    static int pipeline_ratelimit_run(void* pipeline)
    {
        struct pipeline_ratelimit* ps = (struct pipeline_ratelimit*)pipeline;
    
        struct rte_port_in* port_in = p->port_in_next;
        struct rte_port_out* port_out = &p->ports_out[0];
        struct rte_port_out* port_drop = &p->ports_out[2];
    
        uint8_t valid_pkt_cnt = 0,invalid_pkt_cnt = 0;
        struct rte_mbuf* valid_pkts[RTE_PORT_IN_BURST_SIZE_MAX];
        struct rte_mbuf* invalid_pkts[RTE_PORT_IN_BURST_SIZE_MAX];
    
        memset(valid_pkts,sizeof(valid_pkts));
        memset(invalid_pkts,sizeof(invalid_pkts));
    
        uint64_t n_pkts;
    
        if (unlikely(port_in == NULL)) {
            return 0;
        }
    
        /* Input port RX */
        n_pkts = port_in->ops.f_rx(port_in->h_port,p->pkts,port_in->burst_size);
    
        if (n_pkts == 0)
        {
            p->port_in_next = port_in->next;
            return 0;
        }
    
        uint32_t rc = 0;
        char* rx_pkt = NULL;
    
        for (j = 0; j < n_pkts; j++) {
    
            struct rte_mbuf* m = p->pkts[j];
            rx_pkt = rte_pktmbuf_mtod(m,char*);
            uint32_t id = rte_be_to_cpu_32(*(uint32_t*)(rx_pkt - sizeof(uint32_t)));
            unsigned short packet_len = rte_be_to_cpu_16(*((unsigned short*)(rx_pkt + 16)));
    
            struct flow_state_t* node = &(ps->flow_state_arr[id]);
    
            if (node->hash && node->threshold != 0)
            {
                // Decide whether to allow of drop the packet
                // returns allow - 1,drop - 0
                if (do_rate_limit(ps,id,(unsigned char*)(rx_pkt + 14)))
                    valid_pkts[valid_pkt_count++] = m;
                else
                    invalid_pkts[invalid_pkt_count++] = m;
            }
            else
                valid_pkts[valid_pkt_count++] = m;
    
            if (invalid_pkt_cnt) {
                p->pkts_mask = 0;
                rte_memcpy(p->pkts,invalid_pkts,sizeof(invalid_pkts));
                p->pkts_mask = RTE_LEN2MASK(invalid_pkt_cnt,uint64_t);
                rte_pipeline_action_handler_port_bulk_mod(p,p->pkts_mask,port_drop);
            }
    
            p->pkts_mask = 0;
            memset(p->pkts,sizeof(p->pkts));
    
            if (valid_pkt_cnt != 0)
            {
                rte_memcpy(p->pkts,valid_pkts,sizeof(valid_pkts));
                p->pkts_mask = RTE_LEN2MASK(valid_pkt_cnt,uint64_t);
            }
    
            rte_pipeline_action_handler_port_bulk_mod(p,port_out);
    
            /* Pick candidate for next port IN to serve */
            p->port_in_next = port_in->next;
            return (int)n_pkts;
        }
}

结果

当从60000个源中为一个目的地生成的流量仅为14Mpps阈值时，没有丢弃。我们能够从IXIA发送12Mpps和接收12Mpps
添加3个或更多目的地后（每个都配置为从60000个来源接收流量），观察到了丢弃。吞吐量仅为8-9 Mpps。当发送到100个目的地（每个目的地60000 src）时，仅处理6.4Mpps。下降了50％。
通过vtune-profiler运行它时，它报告rte_hash_lookup_data为热点，并且主要是内存绑定（DRAM绑定）。我将尽快附上vtune报告。

解决方法

根据内部测试的更新，rte_hash库不会导致性能下降。因此，如注释中所建议，由于当前的模式和算法设计，更有可能导致高速缓存未命中，并且每个周期的指令更少。

要确定是前端停滞还是后端管道停滞或内存停滞，请使用perf或vtune。另外，请尽量减少分支，并使用更多的likely和prefetch。

DPDK 17.11.1-执行基于目标的速率限制时会出现掉线

如何解决DPDK 17.11.1-执行基于目标的速率限制时会出现掉线

解决方法

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