Re: [dpdk-users] Using DPDK EAL with existing multi-threaded application

[Daniel Verkamp <daniel.verkamp@intel.com>]

On 11/07/2016 11:39 PM, Jason Lefley wrote:
> I am working on leveraging SPDK (which internally uses EAL from DPDK)
> from an existing application that uses Intel’s TBB. I do not need to
> use EAL for multithreading but SPDK does require at least huge page
> support and PCI access from EAL.
> 
> I noticed that if I try to use TBB’s parallel_for() after I have
> called rte_eal_init(), then the TBB operation doesn’t actually run in
> parallel. If I remove the call to rte_eal_init(), the TBB operations
> work as expected however I then cannot use SPDK. Does anyone have any
> input regarding how I can keep my existing multi-threaded application
> working as intended as I integrate SPDK/DPDK?
> 
> Thanks
> 

Hi Jason,

If you are not calling any functions that rely on DPDK's lcore pinning
for correctness, you should be able to change the calling thread's CPU
affinity with rte_thread_set_affinity() so that newly-created threads
can run on more than one CPU core.  I am not sure how TBB creates its
threads, but as long as you set the affinity before calling any TBB
functions, the updated CPU affinity should be inherited by any
newly-created threads.

There is a recently-implemented helper function in SPDK to temporarily
change the thread affinity in this way:

https://github.com/spdk/spdk/commit/fa5206c416144b41c384d678cf33f98f1fe1042c

Thanks,
-- Daniel