作者｜donatello1996

來源 | 電子發燒友

題圖｜飛凌嵌入式

rte_ring是一個用CAS實現的無鎖FIFO環形隊列，支持多消費者/生產者同時出入隊列，常用于多線程/多進程之間的通信。具體原理可以查看DPDK官方文檔或者閱讀源碼，本文采用的硬件板卡為飛凌嵌入式OKMX8MP-C開發板，系統版本Linux5.4.70+Qt5.15.0，主要介紹通過編譯DPDK源碼實現rte_ring無鎖環隊列進程間通信。

下面就跟著小編一起了解下。

下載并解壓飛凌廠商提供的iMX8MP內核源碼壓縮包分卷：

在虛擬機中合并壓縮分卷并解壓得出內核源碼包文件夾OK8MP-linux-kernel，將文件夾使用tar打包并復制到TF卡文件系統中解壓：

找到內核源碼中的配置文件OK8MP-C_defconfig：

這個就是make選項，使用

make OK8MP-C_defconfig

指令即可配置編譯選項：

make -j4

開始編譯：

注意開始編譯前需要安裝常用軟件：

apt install bison bc flex

增量編譯完畢：

接下來就可以下載DPDK并運行rte_ring無鎖環隊列Demo應用，需要從

https://www.dpdk.org/

官網中下載DPDK 19.11.10 (LTS)長期支持版本：

在根目錄下的mk/文件夾下找到名為rte_vars.mk設置文件，找到環境變量RTE_KERNELDIR，修改為上述的內核源碼路徑：

RTE_KERNELDIR ?= /home/OK8MP-linux-kernel/

進入usertools文件夾，找到dpdk-setup.sh腳本并運行

選擇8，ARM64-armv8a-linuxapp-gcc，

這個選項會使dpdk的gcc交叉編譯鏈生成適用于armv8a處理器的外部庫，外部庫中有kmod和lib等ko文件和so文件，是用于第三方程序開發和運行的：

使用指令

insmod /home/dpdk-stable-19.11.10/arm64-armv8a-linuxapp-gcc/kmod/igb_uio.ko

加載igb_uio.ko驅動文件，這是進行dpdk開發必備的步驟：

然后是使用dpdk-devbind.py腳本手動進行hugepage大頁內存綁定，此處為numa方式：

此舉會將/mnt/huge文件mount成hugepage映射文件，并實實在在地占用內存空間：

準備工作完成，我們接下來可以進行rte_ring無鎖環隊列Demo代碼的編寫，但是在編寫之前，需要對無鎖環隊列有一個基本的認識：https://blog.csdn.net/chen98765432101/article/details/69367633

無論是dpdk第三方開發的rte_ring還是Linux內核中本就存在的無鎖環隊列，其基本原理類似，在一條分配好的隊列型內存空間中，讀寫方式為FIFO（先進先出），讀和寫的動作分別有兩個進程或兩個線程進行，寫進程不斷往地址自增的內存位置寫入數據，讀進程不斷讀取地址自增的內存位置的數據，當寫位置的內存地址已為隊列中內存的最高值時，需要釋放隊列中內存地址最低值的空間供寫進程繼續寫，方式仍與上一周期相同（不斷往地址自增的內存位置寫入數據），釋放過程需要保證對末尾內存地址空間的鎖定與解鎖，避免讀寫過程出錯。而不同的是，Linux內核中的無鎖環隊列，地址管理和讀寫控制均由內核進行，而dpdk的rte_ring則由dpdk內部的控制器進行，因為dpdk這一模塊完整地接管了所分配內存空間的管理權，是直接繞過Linux內核進行管理的，內核也無權訪問dpdk控制器的具體管理細節。

編寫無鎖環隊列兩個進程的Demo，先寫Primary進程：

#include #include #include #include #include #include #include #include #include #include 
#include #include 
#define RTE_LOGTYPE_APP RTE_LOGTYPE_USER1
static const char *_MSG_POOL = "MSG_POOL";static const char *_SEC_2_PRI = "SEC_2_PRI";static const char *_PRI_2_SEC = "PRI_2_SEC";static const char *_PRI_2_THI = "PRI_2_THI";
struct rte_ring *send_ring, *recv_ring , *send_ring_third;struct rte_mempool *message_pool;volatile int quit = 0;
static void * lcore_recv(void *arg){        unsigned lcore_id = rte_lcore_id();
        printf("Starting core %u\n", lcore_id);        while (!quit){                void *msg;                if (rte_ring_dequeue(recv_ring, &msg) < 0)                {                        usleep(5);                        continue;                }                printf("lcore_id = %d Received '%s'\n" , lcore_id , (char *)msg);                rte_mempool_put(message_pool , msg);        }
        return 0;}
int string_size = 100;int elt_size = 128;pthread_t id1;
int main(int argc, char **argv){        const unsigned flags = 0;        const unsigned ring_size = 64;        const unsigned pool_size = 1024;        const unsigned pool_cache = 32;        const unsigned priv_data_sz = 0;
        int ret;        unsigned lcore_id;
        ret = rte_eal_init(argc, argv);        if (ret < 0)                rte_exit(EXIT_FAILURE, "Cannot init EAL\n");
        send_ring = rte_ring_create(_PRI_2_SEC, ring_size, rte_socket_id(), flags);        recv_ring = rte_ring_create(_SEC_2_PRI, ring_size, rte_socket_id(), flags);        send_ring_third = rte_ring_create(_PRI_2_THI, ring_size, rte_socket_id(), flags);        message_pool = rte_mempool_create(_MSG_POOL, pool_size,                        elt_size, pool_cache, priv_data_sz,                        NULL, NULL, NULL, NULL,                        rte_socket_id(), flags);
        if (send_ring == NULL)                rte_exit(EXIT_FAILURE, "Problem getting sending ring\n");
        if (recv_ring == NULL)                rte_exit(EXIT_FAILURE, "Problem getting receiving ring\n");
        if (send_ring_third == NULL)                rte_exit(EXIT_FAILURE, "Problem getting send_ring_third\n");
        if (message_pool == NULL)                rte_exit(EXIT_FAILURE, "Problem getting message pool\n");
        pthread_create(&id1 , NULL , lcore_recv , NULL);        while(1)        {                void *msg = NULL;                if (rte_mempool_get(message_pool, &msg) < 0)                        continue;
                snprintf((char *)msg, string_size, "%s", "primary to secondary");                if (rte_ring_enqueue(send_ring , msg) < 0)                 {                        rte_mempool_put(message_pool, msg);                }
                if (rte_mempool_get(message_pool, &msg) < 0)                        continue;
                snprintf((char *)msg, string_size, "%s", "primary to third");                if (rte_ring_enqueue(send_ring_third , msg) < 0)                 {                        rte_mempool_put(message_pool, msg);                }
                sleep(1);        }
        return 0;}

注意在Makefile文件里面要關閉WERROR相關編譯選項：

#   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.
ifeq ($(RTE_SDK),)$(error "Please define RTE_SDK environment variable")endif
# Default target, can be overridden by command line or environmentRTE_TARGET ?= arm64-armv8a-linuxapp-gcc
include $(RTE_SDK)/mk/rte.vars.mk
# binary nameAPP = rte_ring_primary
# all source are stored in SRCS-ySRCS-y := main.c
CFLAGS += -O0CFLAGS += 
include $(RTE_SDK)/mk/rte.extapp.mk

Secondary進程：

#include #include #include #include #include #include #include #include #include #include 
#include #include 
#define RTE_LOGTYPE_APP RTE_LOGTYPE_USER1
static const char *_MSG_POOL = "MSG_POOL";static const char *_SEC_2_PRI = "SEC_2_PRI";static const char *_PRI_2_SEC = "PRI_2_SEC";
struct rte_ring *send_ring, *recv_ring;struct rte_mempool *message_pool;volatile int quit = 0;int string_size = 100;
static int lcore_send(__attribute__((unused)) void *arg){        unsigned lcore_id = rte_lcore_id();
        while(1)        {                void *msg = NULL;                if (rte_mempool_get(message_pool, &msg) < 0)                        continue;
                snprintf((char *)msg , string_size , "%s", "secondary to primary");                if (rte_ring_enqueue(send_ring , msg) < 0)                 {                        rte_mempool_put(message_pool, msg);                }                sleep(1);        }        return 0;}
pthread_t id1;
int main(int argc, char **argv){        const unsigned flags = 0;        const unsigned ring_size = 64;        const unsigned pool_size = 1024;        const unsigned pool_cache = 32;        const unsigned priv_data_sz = 0;
        int ret;        unsigned lcore_id;        ret = rte_eal_init(argc, argv);        if (ret < 0)                rte_exit(EXIT_FAILURE, "Cannot init EAL\n");
        recv_ring = rte_ring_lookup(_PRI_2_SEC);        send_ring = rte_ring_lookup(_SEC_2_PRI);        message_pool = rte_mempool_lookup(_MSG_POOL);
        if (send_ring == NULL)                rte_exit(EXIT_FAILURE, "Problem getting sending ring\n");        if (recv_ring == NULL)                rte_exit(EXIT_FAILURE, "Problem getting receiving ring\n");        if (message_pool == NULL)                rte_exit(EXIT_FAILURE, "Problem getting message pool\n");
        pthread_create(&id1 , NULL , lcore_send , NULL);    while (1)        {                lcore_id = rte_lcore_id();        void * msg = NULL;        if (rte_ring_dequeue(recv_ring, &msg) < 0)                {            usleep(5);            continue;        }
        printf("lcore_id = %d Received: %s\n" , lcore_id , (char *)msg);
        rte_mempool_put(message_pool, msg);    }
        return 0;}

左右滑動查看完整代碼

同樣在Makefile文件里面要關閉WERROR相關編譯選項：

#   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.
ifeq ($(RTE_SDK),)$(error "Please define RTE_SDK environment variable")endif
# Default target, can be overridden by command line or environmentRTE_TARGET ?= arm64-armv8a-linuxapp-gcc
include $(RTE_SDK)/mk/rte.vars.mk
# binary nameAPP = rte_ring_secondary
# all source are stored in SRCS-ySRCS-y := main.c
CFLAGS += -O3CFLAGS += $()
include $(RTE_SDK)/mk/rte.extapp.mk

運行，這里說一下，基于rte_ring的進程間通信，Secondary進程最好是使用auto類型：

./rte_ring_primary --proc-type primary./rte_ring_secondary --proc-type auto

運行效果：

作者簡介

donatello1996，某大型企業資深嵌入式工程師，電子發燒友論壇技術大牛，同時也是飛凌嵌入式多年鐵粉，曾基于飛凌多款板卡產出過優質測評文章或使用心得。本期三篇文章為donatello1996在使用OKMX8MP-C開發板過程中精心產出的干貨，在此對donatello1996表示感謝。