[dpdk-dev] one lightwight rte_eal_init() for SECONDARY processes which only use sharedmemory

["Chi, Xiaobo (NSN - CN/Hangzhou)" <xiaobo.chi@nsn.com>]

Hi,
Background:
What we are doing now is port make telecom network element to be cloud based.  For one of our product,  DPDK is applied not only for fastpath/dataplane processing, but also for Distributed Message eXchange (DMX) between different processes/applications which may located in different VM even different host.  for such a DMX system, in one VM, we have one DPDK based dmxdemo (which acts as the PRIMARY) which is in charge of distribute message between different applications, and dozens of applications (act as SECONDARY) to use DPDK based rte_tx_ring/rte_rx_ring/mempool/memzone to send receive messages to dmxdemo.

Problem:
Here, these DPDK based SECONDARY processes need only the DPDK's hugepage based sharememory mechanism and it's upper libs (such as ring, mempool, etc.), they need not cpu core pinning, iopl privilege changing , pci device, timer, alarm, interrupt, shared_driver_list,  core_info, threads for each core, etc. Then, for such kind of SECONDARY processes, the current rte_eal_init() is too heavy.
I have seen some others also met similar troubles.

Solution:
I write one light weight rte_eal_init(), called rte_eal_secondary_mem_init() as following.  It only initializes shared memory and mandatory resources. I expect your review and hope these code can be merged into DPDK main branch.

static void eal_secondary_mem_parse_args(int argc, char **argv)
{
        static struct option lgopts[] = {
                {OPT_HUGE_DIR, 1, 0, 0},
                {OPT_FILE_PREFIX, 1, 0, 0},
                {0, 0, 0, 0}
        };

        int opt;
        int option_index;

        while ((opt = getopt_long(argc, argv, "", lgopts, &option_index)) != EOF) {

        if (!opt ) {
         if (!strcmp(lgopts[option_index].name, OPT_HUGE_DIR)) {
            internal_config.hugepage_dir = optarg;
         }
         else if (!strcmp(lgopts[option_index].name, OPT_FILE_PREFIX)) {
            internal_config.hugefile_prefix = optarg;
         }
      }
   }
}

int rte_eal_secondary_mem_init( int argc, char **argv )
{
        static rte_atomic32_t run_once = RTE_ATOMIC32_INIT(0);
        const char *logid;

        if (!rte_atomic32_test_and_set(&run_once))
                return -1;

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

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

   memset( &internal_config, 0, sizeof( struct internal_config ) );
   /*this is only for secondary PRBs */
   internal_config.process_type = RTE_PROC_SECONDARY;
        internal_config.hugefile_prefix = HUGEFILE_PREFIX_DEFAULT;
        internal_config.hugepage_dir = NULL;
   /* user can freely define the hugefile_prefix and hugepage_dir */
   eal_secondary_mem_parse_args( argc, argv );

   RTE_LOG(INFO, EAL, "prefix=%s, dir=%s.\n",internal_config.hugefile_prefix, internal_config.hugepage_dir );

   /* To share memory config with PRIMARY process */
   internal_config.no_shconf = 0;
   rte_config_init();

        if (rte_eal_memory_init() < 0)
                rte_panic("Cannot init memory\n");

        if (rte_eal_memzone_init() < 0)
                rte_panic("Cannot init memzone\n");

        if (rte_eal_log_init(logid, LOG_DAEMON ) < 0)
                rte_panic("Cannot init logs\n");

        return 0;
}

brgs,
chi xiaobo