[dpdk-dev] Issues with running multicore

[Bruce Richardson]

On Wed, Nov 25, 2015 at 12:59:01PM -0500, Sugumaran, Varthamanan wrote:
> Hi All,
> Iam trying to create multi core application by mapping separate function for each core.
> I had followed Multi process example and I had used pthread.
> The use case is:
> 
> 1.      In a single process, launch pthread and run rte_eal_init
> 
> 2.      Once  rte_eal_init is done, create 3 pthreads
> 
> 3.      Launch master core.
> 
> 4.      In each of 3 pthread, launch slave core.
> 
> The issue is, I don't see 4 cores running. Instead I see only single core running.
> 
> Here is the Pseudo code:
> 
> Init_pmd{
>    ret = rte_eal_init(args, argv) ==> I had set the number of cores to 4 in the params.

Just to clarify here, what did you actually use as the coremask. If you used
-c 4, then that will cause only a single thread to be used running on core 2.

> 
>     pthread_create(&thread1, NULL, (void*)threadFun1, NULL);
>     pthread_create(&thread2, NULL, (void*)threadFun2, NULL);
>     pthread_create(&thread3, NULL, (void*)threadFun3, NULL);

These threads are separate from any threads used by DPDK, and DPDK will not use
them for anything, or assign them to any lcores. Unless you configure them
otherwise in your code, they will run on the same physical core as the master
thread.

> 
>    rte_eal_mp_remote_launch(launch_pmd_single_lcore, NULL, CALL_MASTER);
> 

This call will only launch functions on the threads created by DPDK - not the
other threads you created above.

> }
> 
> Iam mapping each core to threadFun1, threadFun2 and threadFun3.
> 
> threadFun1
> {
>    RTE_LCORE_FOREACH_SLAVE(lcore_id)
>    {
>       if( lcore_id == 1 )
>          rte_eal_remote_launch(threadFun1_launch_one_lcore, NULL, lcore_id);
>    }
> }
> 
> Has anyone seen this issue?
> Please let me know if iam missing something?

I'm not sure your understanding of how DPDK threads work is correct. See my
comments above, and perhaps check how things are done in a number of the DPDK
sample applications to see if what you want can be done without additional 
pthread calls in your application.

/Bruce

> 
> Thanks
> Vartha
>