dpdk helloworld代码分析

int
MAIN(int argc, char **argv)
{
    int ret;
    unsigned lcore_id;

    ret = rte_eal_init(argc, argv);
    if (ret < 0)
        rte_panic("Cannot init EAL
");

    /* call lcore_hello() on every slave lcore */
    RTE_LCORE_FOREACH_SLAVE(lcore_id) {
        rte_eal_remote_launch(lcore_hello, NULL, lcore_id);
    }

    /* call it on master lcore too */
    lcore_hello(NULL);

    rte_eal_mp_wait_lcore();
    return 0;
}

程序的流程如下图所示：

代码首先初始化了Environment Abstraction Layer（EAL），EAL主要提供了以下功能

• Intel® DPDK loading and launching
• Support for multi-process and multi-thread execution types
• Core affinity/assignment procedures
• System memory allocation/de-allocation
• Atomic/lock operations
• Time reference
• PCI bus access
• Trace and debug functions
• CPU feature identification
• Interrupt handling
• Alarm operations

num_pages

/* Launch threads, called at application init(). */
int
rte_eal_init(int argc, char **argv)
{
    int i, fctret, ret;
    pthread_t thread_id;
    static rte_atomic32_t run_once = RTE_ATOMIC32_INIT(0);
    struct shared_driver *solib = NULL;
    const char *logid;

    /* 只允许运行一次 */
    if (!rte_atomic32_test_and_set(&run_once))
        return -1;

    logid = strrchr(argv[0], '/');
    logid = strdup(logid ? logid + 1: argv[0]);

    thread_id = pthread_self();

    if (rte_eal_log_early_init() < 0)
        rte_panic("Cannot init early logs
");

    /* 获取系统中的CPU数量 */
    if (rte_eal_cpu_init() < 0)
        rte_panic("Cannot detect lcores
");

    /* 根据命令行参数初始化internal_config */
    fctret = eal_parse_args(argc, argv);
    if (fctret < 0)
        exit(1);

    /* 初始化系统中hugepage种类以及数量信息到internal_config.hugepage_info，用于后续内存初始化 */
    if (internal_config.no_hugetlbfs == 0 &&
            internal_config.process_type != RTE_PROC_SECONDARY &&
            internal_config.xen_dom0_support == 0 &&
            eal_hugepage_info_init() < 0)
        rte_panic("Cannot get hugepage information
");

    /* 获取系统中所有hugepage内存大小，计算方法hugepage_sz*num_pages */
    if (internal_config.memory == 0 && internal_config.force_sockets == 0) {
        if (internal_config.no_hugetlbfs)
            internal_config.memory = MEMSIZE_IF_NO_HUGE_PAGE;
        else
            internal_config.memory = eal_get_hugepage_mem_size();
    }

    if (internal_config.vmware_tsc_map == 1) {
#ifdef RTE_LIBRTE_EAL_VMWARE_TSC_MAP_SUPPORT
        rte_cycles_vmware_tsc_map = 1;
        RTE_LOG (DEBUG, EAL, "Using VMWARE TSC MAP, "
                "you must have monitor_control.pseudo_perfctr = TRUE
");
#else
        RTE_LOG (WARNING, EAL, "Ignoring --vmware-tsc-map because "
                "RTE_LIBRTE_EAL_VMWARE_TSC_MAP_SUPPORT is not set
");
#endif
    }

    rte_srand(rte_rdtsc());

    /* 在/var/run或者用户的home目录创建.rte_config文件用于存储内存配置信息（rte_mem_config结构）如果process type为RTE_PROC_SECONDARY则等待PRIMARY完成内存初始化 */
    rte_config_init();

    /* 请求IO权限 */
    if (rte_eal_iopl_init() == 0)
        rte_config.flags |= EAL_FLG_HIGH_IOPL;
    
    /* 扫描系统中所有的PCI设备，并创建对应的device结构链到device_list中 */
    if (rte_eal_pci_init() < 0)
        rte_panic("Cannot init PCI
");

#ifdef RTE_LIBRTE_IVSHMEM
    if (rte_eal_ivshmem_init() < 0)
        rte_panic("Cannot init IVSHMEM
");
#endif

    /* 初始化rte_config->mem_config，并映射hugepage到挂载目录下的文件rte_map* */
    if (rte_eal_memory_init() < 0)
        rte_panic("Cannot init memory
");

    /* the directories are locked during eal_hugepage_info_init */
    eal_hugedirs_unlock();
    
    /* memzone可用内存初始化 */
    if (rte_eal_memzone_init() < 0)
        rte_panic("Cannot init memzone
");

    /* memconfig链表初始化 */
    if (rte_eal_tailqs_init() < 0)
        rte_panic("Cannot init tail queues for objects
");

#ifdef RTE_LIBRTE_IVSHMEM
    if (rte_eal_ivshmem_obj_init() < 0)
        rte_panic("Cannot init IVSHMEM objects
");
#endif

    if (rte_eal_log_init(logid, internal_config.syslog_facility) < 0)
        rte_panic("Cannot init logs
");

    /* 告警? 具体内容待分析 */
    if (rte_eal_alarm_init() < 0)
        rte_panic("Cannot init interrupt-handling thread
");

    /* 创建与收包驱动通信用管道并初始化中断处理线程 */
    if (rte_eal_intr_init() < 0)
        rte_panic("Cannot init interrupt-handling thread
");

    /* 定时器 */
    if (rte_eal_timer_init() < 0)
        rte_panic("Cannot init HPET or TSC timers
");

    /* 检查master core所在socket是否有内存 */
    eal_check_mem_on_local_socket();

    /* 标记初始化完成 */
    rte_eal_mcfg_complete();

    /* 白名单内设备初始化 */
    if (rte_eal_non_pci_ethdev_init() < 0)
        rte_panic("Cannot init non-PCI eth_devs
");

    /* 动态链接库 */
    TAILQ_FOREACH(solib, &solib_list, next) {
        solib->lib_handle = dlopen(solib->name, RTLD_NOW);
        if ((solib->lib_handle == NULL) && (solib->name[0] != '/')) {
            /* relative path: try again with "./" prefix */
            char sopath[PATH_MAX];
            snprintf(sopath, sizeof(sopath), "./%s", solib->name);
            solib->lib_handle = dlopen(sopath, RTLD_NOW);
        }
        if (solib->lib_handle == NULL)
            RTE_LOG(WARNING, EAL, "%s
", dlerror());
    }

    RTE_LOG(DEBUG, EAL, "Master core %u is ready (tid=%x)
",
        rte_config.master_lcore, (int)thread_id);

    /* 创建lcore的主线程 */
    RTE_LCORE_FOREACH_SLAVE(i) {

        /*
         * create communication pipes between master thread
         * and children
         */
        if (pipe(lcore_config[i].pipe_master2slave) < 0)
            rte_panic("Cannot create pipe
");
        if (pipe(lcore_config[i].pipe_slave2master) < 0)
            rte_panic("Cannot create pipe
");

        lcore_config[i].state = WAIT;

        /* create a thread for each lcore */
        ret = pthread_create(&lcore_config[i].thread_id, NULL,
                     eal_thread_loop, NULL);
        if (ret != 0)
            rte_panic("Cannot create thread
");
    }

    /* master线程绑定CPU */
    eal_thread_init_master(rte_config.master_lcore);

    /*
     * Launch a dummy function on all slave lcores, so that master lcore
     * knows they are all ready when this function returns.
     */
    /* 通知lcore开始调用loop */
    rte_eal_mp_remote_launch(sync_func, NULL, SKIP_MASTER);
    rte_eal_mp_wait_lcore();

    return fctret;
}

下面主要分析一下内存的初始化过程

对于process type是PRIMARY的调用rte_eal_hugepage_init； SECONDARY的调用rte_eal_hugepage_attach；

/* init memory subsystem */
int
rte_eal_memory_init(void)
{
    RTE_LOG(INFO, EAL, "Setting up memory...
");
    const int retval = rte_eal_process_type() == RTE_PROC_PRIMARY ?
            rte_eal_hugepage_init() :
            rte_eal_hugepage_attach();
    if (retval < 0)
        return -1;

    if (internal_config.no_shconf == 0 && rte_eal_memdevice_init() < 0)
        return -1;

    return 0;
}

/*
 * Prepare physical memory mapping: fill configuration structure with
 * these infos, return 0 on success.
 *  1. map N huge pages in separate files in hugetlbfs
 *  2. find associated physical addr
 *  3. find associated NUMA socket ID
 *  4. sort all huge pages by physical address
 *  5. remap these N huge pages in the correct order
 *  6. unmap the first mapping
 *  7. fill memsegs in configuration with contiguous zones
 */
static int
rte_eal_hugepage_init(void)
{
    struct rte_mem_config *mcfg;
    struct hugepage_file *hugepage, *tmp_hp = NULL;
    struct hugepage_info used_hp[MAX_HUGEPAGE_SIZES];

    uint64_t memory[RTE_MAX_NUMA_NODES];

    unsigned hp_offset;
    int i, j, new_memseg;
    int nr_hugefiles, nr_hugepages = 0;
    void *addr;
#ifdef RTE_EAL_SINGLE_FILE_SEGMENTS
    int new_pages_count[MAX_HUGEPAGE_SIZES];
#endif

    memset(used_hp, 0, sizeof(used_hp));

    /* get pointer to global configuration */
    mcfg = rte_eal_get_configuration()->mem_config;

    /* hugetlbfs can be disabled */
    if (internal_config.no_hugetlbfs) {
        /* 对于不使用hugetlbfs的直接使用堆内存 */
        addr = malloc(internal_config.memory);
        mcfg->memseg[0].phys_addr = (phys_addr_t)(uintptr_t)addr;
        mcfg->memseg[0].addr = addr;
        mcfg->memseg[0].len = internal_config.memory;
        mcfg->memseg[0].socket_id = SOCKET_ID_ANY;
        return 0;
    }

/* check if app runs on Xen Dom0 */
    if (internal_config.xen_dom0_support) {
#ifdef RTE_LIBRTE_XEN_DOM0
        /* use dom0_mm kernel driver to init memory */
        if (rte_xen_dom0_memory_init() < 0)
            return -1;
        else
            return 0;
#endif
    }


    /* calculate total number of hugepages available. at this point we haven't
     * yet started sorting them so they all are on socket 0 */
    for (i = 0; i < (int) internal_config.num_hugepage_sizes; i++) {
        /* meanwhile, also initialize used_hp hugepage sizes in used_hp */
        used_hp[i].hugepage_sz = internal_config.hugepage_info[i].hugepage_sz;

        nr_hugepages += internal_config.hugepage_info[i].num_pages[0];
    }

    /* tmp_hp为hugepage的控制块 */
    /*
     * allocate a memory area for hugepage table.
     * this isn't shared memory yet. due to the fact that we need some
     * processing done on these pages, shared memory will be created
     * at a later stage.
     */
    tmp_hp = malloc(nr_hugepages * sizeof(struct hugepage_file));
    if (tmp_hp == NULL)
        goto fail;

    memset(tmp_hp, 0, nr_hugepages * sizeof(struct hugepage_file));

    hp_offset = 0; /* where we start the current page size entries */

    /* map all hugepages and sort them */
    for (i = 0; i < (int)internal_config.num_hugepage_sizes; i ++){
        struct hugepage_info *hpi;

        /*
         * we don't yet mark hugepages as used at this stage, so
         * we just map all hugepages available to the system
         * all hugepages are still located on socket 0
         */
        hpi = &internal_config.hugepage_info[i];

        if (hpi->num_pages[0] == 0)
            continue;

        /* 把所有hugepage映射进内存 */
        /* map all hugepages available */
        if (map_all_hugepages(&tmp_hp[hp_offset], hpi, 1) < 0){
            RTE_LOG(DEBUG, EAL, "Failed to mmap %u MB hugepages
",
                    (unsigned)(hpi->hugepage_sz / 0x100000));
            goto fail;
        }

        /* 记录每一片hugepage的物理内存 */
        /* find physical addresses and sockets for each hugepage */
        if (find_physaddrs(&tmp_hp[hp_offset], hpi) < 0){
            RTE_LOG(DEBUG, EAL, "Failed to find phys addr for %u MB pages
",
                    (unsigned)(hpi->hugepage_sz / 0x100000));
            goto fail;
        }

        /* 记录每一个片hugepage的socket id */
        if (find_numasocket(&tmp_hp[hp_offset], hpi) < 0){
            RTE_LOG(DEBUG, EAL, "Failed to find NUMA socket for %u MB pages
",
                    (unsigned)(hpi->hugepage_sz / 0x100000));
            goto fail;
        }

        /* 控制块按照物理地址从小到大排序 */
        if (sort_by_physaddr(&tmp_hp[hp_offset], hpi) < 0)
            goto fail;

#ifdef RTE_EAL_SINGLE_FILE_SEGMENTS
        /* remap all hugepages into single file segments */
        new_pages_count[i] = remap_all_hugepages(&tmp_hp[hp_offset], hpi);
        if (new_pages_count[i] < 0){
            RTE_LOG(DEBUG, EAL, "Failed to remap %u MB pages
",
                    (unsigned)(hpi->hugepage_sz / 0x100000));
            goto fail;
        }

        /* we have processed a num of hugepages of this size, so inc offset */
        hp_offset += new_pages_count[i];
#else
        /* 连续的物理内存hugepage找到对应连续的虚拟内存空间重新映射 */
        /* remap all hugepages */
        if (map_all_hugepages(&tmp_hp[hp_offset], hpi, 0) < 0){
            RTE_LOG(DEBUG, EAL, "Failed to remap %u MB pages
",
                    (unsigned)(hpi->hugepage_sz / 0x100000));
            goto fail;
        }

        /* 删除第一次不连续的映射 */
        /* unmap original mappings */
        if (unmap_all_hugepages_orig(&tmp_hp[hp_offset], hpi) < 0)
            goto fail;

        /* we have processed a num of hugepages of this size, so inc offset */
        hp_offset += hpi->num_pages[0];
#endif
    }

#ifdef RTE_EAL_SINGLE_FILE_SEGMENTS
    nr_hugefiles = 0;
    for (i = 0; i < (int) internal_config.num_hugepage_sizes; i++) {
        nr_hugefiles += new_pages_count[i];
    }
#else
    nr_hugefiles = nr_hugepages;
#endif

    /* 所有socket的内存清零 */
    /* clean out the numbers of pages */
    for (i = 0; i < (int) internal_config.num_hugepage_sizes; i++)
        for (j = 0; j < RTE_MAX_NUMA_NODES; j++)
            internal_config.hugepage_info[i].num_pages[j] = 0;

    /* 重新计算每个socket对应size的内存 */
    /* get hugepages for each socket */
    for (i = 0; i < nr_hugefiles; i++) {
        int socket = tmp_hp[i].socket_id;

        /* find a hugepage info with right size and increment num_pages */
        for (j = 0; j < (int) internal_config.num_hugepage_sizes; j++) {
            if (tmp_hp[i].size ==
                    internal_config.hugepage_info[j].hugepage_sz) {
#ifdef RTE_EAL_SINGLE_FILE_SEGMENTS
                    internal_config.hugepage_info[j].num_pages[socket] +=
                        tmp_hp[i].repeated;
#else
                internal_config.hugepage_info[j].num_pages[socket]++;
#endif
            }
        }
    }

    /* make a copy of socket_mem, needed for number of pages calculation */
    for (i = 0; i < RTE_MAX_NUMA_NODES; i++)
        memory[i] = internal_config.socket_mem[i];

    /* 把每个socket内存的情况写入used_hp，并返回所有hugepage页数 */
    /* calculate final number of pages */
    nr_hugepages = calc_num_pages_per_socket(memory,
            internal_config.hugepage_info, used_hp,
            internal_config.num_hugepage_sizes);

    /* error if not enough memory available */
    if (nr_hugepages < 0)
        goto fail;

    /* reporting in! */
    for (i = 0; i < (int) internal_config.num_hugepage_sizes; i++) {
        for (j = 0; j < RTE_MAX_NUMA_NODES; j++) {
            if (used_hp[i].num_pages[j] > 0) {
                RTE_LOG(INFO, EAL,
                        "Requesting %u pages of size %uMB"
                        " from socket %i
",
                        used_hp[i].num_pages[j],
                        (unsigned)
                            (used_hp[i].hugepage_sz / 0x100000),
                        j);
            }
        }
    }

    /* 创建可通过文件定位到的共享hugepage控制块 */
    /* create shared memory */
    hugepage = create_shared_memory(eal_hugepage_info_path(),
            nr_hugefiles * sizeof(struct hugepage_file));

    if (hugepage == NULL) {
        RTE_LOG(ERR, EAL, "Failed to create shared memory!
");
        goto fail;
    }
    memset(hugepage, 0, nr_hugefiles * sizeof(struct hugepage_file));

    /* 根据used_hp的内容，每个socket内存只映射used_hp[i].num_pages[socket]，剩下的unmap，什么时候会出现这种情况呢？ */
    /*
     * unmap pages that we won't need (looks at used_hp).
     * also, sets final_va to NULL on pages that were unmapped.
     */
    if (unmap_unneeded_hugepages(tmp_hp, used_hp,
            internal_config.num_hugepage_sizes) < 0) {
        RTE_LOG(ERR, EAL, "Unmapping and locking hugepages failed!
");
        goto fail;
    }

    /* 最终结果的hugepage控制块复制到共享内存中 */
    /*
     * copy stuff from malloc'd hugepage* to the actual shared memory.
     * this procedure only copies those hugepages that have final_va
     * not NULL. has overflow protection.
     */
    if (copy_hugepages_to_shared_mem(hugepage, nr_hugefiles,
            tmp_hp, nr_hugefiles) < 0) {
        RTE_LOG(ERR, EAL, "Copying tables to shared memory failed!
");
        goto fail;
    }

    /* free the temporary hugepage table */
    free(tmp_hp);
    tmp_hp = NULL;

    /* find earliest free memseg - this is needed because in case of IVSHMEM,
     * segments might have already been initialized */
    for (j = 0; j < RTE_MAX_MEMSEG; j++)
        if (mcfg->memseg[j].addr == NULL) {
            /* move to previous segment and exit loop */
            j--;
            break;
        }

    for (i = 0; i < nr_hugefiles; i++) {
        new_memseg = 0;

        /* if this is a new section, create a new memseg */
        if (i == 0)
            new_memseg = 1;
        else if (hugepage[i].socket_id != hugepage[i-1].socket_id)
            new_memseg = 1;
        else if (hugepage[i].size != hugepage[i-1].size)
            new_memseg = 1;
        else if ((hugepage[i].physaddr - hugepage[i-1].physaddr) !=
            hugepage[i].size)
            new_memseg = 1;
        else if (((unsigned long)hugepage[i].final_va -
            (unsigned long)hugepage[i-1].final_va) != hugepage[i].size)
            new_memseg = 1;

        /* 物理地址连续且虚拟地址连续的内存块为一个segment */
        if (new_memseg) {
            j += 1;
            if (j == RTE_MAX_MEMSEG)
                break;

            mcfg->memseg[j].phys_addr = hugepage[i].physaddr;
            mcfg->memseg[j].addr = hugepage[i].final_va;
#ifdef RTE_EAL_SINGLE_FILE_SEGMENTS
            mcfg->memseg[j].len = hugepage[i].size * hugepage[i].repeated;
#else
            mcfg->memseg[j].len = hugepage[i].size;
#endif
            mcfg->memseg[j].socket_id = hugepage[i].socket_id;
            mcfg->memseg[j].hugepage_sz = hugepage[i].size;
        }
        /* continuation of previous memseg */
        else {
            mcfg->memseg[j].len += mcfg->memseg[j].hugepage_sz;
        }
        hugepage[i].memseg_id = j;
    }

    if (i < nr_hugefiles) {
        RTE_LOG(ERR, EAL, "Can only reserve %d pages "
            "from %d requested
"
            "Current %s=%d is not enough
"
            "Please either increase it or request less amount "
            "of memory.
",
            i, nr_hugefiles, RTE_STR(CONFIG_RTE_MAX_MEMSEG),
            RTE_MAX_MEMSEG);
        return (-ENOMEM);
    }

    return 0;

fail:
    if (tmp_hp)
        free(tmp_hp);
    return -1;
}