[dpdk-dev] Non-argv dependant rte_eal_init() call
Stephen Hemminger
stephen at networkplumber.org
Thu Aug 1 19:06:38 CEST 2013
On Thu, 01 Aug 2013 17:37:35 +0200
Marc Sune <marc.sune at bisdn.de> wrote:
> Dear all,
>
> Sorry in advance if there is another API for this and I haven't found
> it, or if there is a strong reason for having it this way. I've seen
> that in the case of both baremetal and Linux applications, the way to
> initialize EAL is passing argv:
>
> <code>
> //...
> /* init EAL */
> ret = rte_eal_init(argc, argv);
> if (ret < 0)
> rte_exit(EXIT_FAILURE, "Invalid EAL arguments\n");
> argc -= ret;
> argv += ret;
> //...
> </code>
>
> However, this is a little bit annoying in the case of GNU/Linux
> user-space applications, hence using DPDK as a library, when porting
> them to DPDK (specially in case of multi-platform applications, like in
> our case), since they are not necessarily designed to be changing the
> main routines in a per platform basis. In our case they are even in
> separate autotools package, since the library providing DPDK based
> services needs to be distributed also in binary version, linking to
> non-DPDK aware code.
>
> In our case, we are right now simply faking the argv, which is a little
> bit ugly:
> <code>
> //...
> 37 const char* argv[EAL_ARGS] = {"./fake", "-c",CORE_MASK,
> "-n",NUM_CACHE_LINES, ""};
> //...
> 53 ret = rte_eal_init(EAL_ARGS, (char**)argv);
> 54 if (ret < 0)
> 55 rte_exit(EXIT_FAILURE, "rte_eal_init failed");
> //...
> </code>
>
> IMHO it would make more sense to have actually two calls, adding a
> library-like initialization. Something like:
>
> <code>
> /*
> * In the comments a warning that this should be called at the very
> beginning of the program.
> *...
> */
> int rte_eal_init(eal_coremask_t core_mask, unsigned int num_of_lines
> /*More parameters here...*/);
>
> /*
> *
> */
> int rte_eal_init_argv(int argc, char **argv);
>
> </code>
>
> Btw, the same applies to the mangling of the main() (MAIN) routine. Is
> this really necessary? Isn't it enough to clearly state in the
> documentation that certain API calls need to be made on the very
> beginning of the application?
We found it more convenient to handle application arguments first before
calling rte_eal_init(). Mostly because application needs to start as daemon,
and eal_init spawns threads.
main(argc, argv) {
progname = strrchr (argv[0], '/');
progname = strdup(progname ? progname + 1 : argv[0]);
ret = parse_args(argc, argv);
if (ret < 0)
return -1;
argc -= ret;
argv += ret;
...
if (daemon_mode) {
if (daemon(1,1) < 0)
rte_panic("daemon failed\n");
}
/* workaround fact that EAL expects progname as first argument */
argv[0] = progname;
ret = rte_eal_init(argc, argv);
if (ret < 0)
return -1;
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