On 2022-09-06 11:43, per...@o2.pl wrote:

Marcus D. Leech wrote:

    On 2022-09-06 06:56, per...@o2.pl wrote:

        Hi,

        Fruits aside, that was a valid question. Cause of bad
        performance when combining DPDK with GNU Radio is a topic that
        needs to be addressed.

        My hypothesis regarding the cause was:

        DPDK needs few processor cores for itself only. GNU Radio runs
        a lot of thread (one thread per block +) and it doesn’t care
        that it tries to run on cores that are busy with DPDK related
        work. And that causes problems.

    I'll point out that at the end of the day, it's the /OS kernel/
    that makes thread scheduling decisions--the application can   give
    it hints (sometimes strong ones), but at the end of the day, the
    kernel assigns work to threads.   An application, per se,  
    doesn't "know" whether a given core is busy--it's not the one
    assigning work to cores...

        The resulting solution that solved the problem for me:

        For every block of the flow-graph run set_processor_affinity
        with a list of all processor cores minus DPDK cores, that you
        set in the /etc/uhd/uhd.conf file.

        Best Regards, Piotr Krysik

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I’ve described what solved the issue on my system, what was the assumed cause and what seemed to prove that assumption. I won’t guarantee that my solution will work on any system, but the general idea that “in order to make GNU Radio + UHD with DPDK work better you have to isolate cores they are running on” will probably prevail. The method of isolation might change.

BTW finally I’ve gone through enough of DPDK’s gotchas to make it work stably again on my systems. So the good news I’ll stop digging up configuration of DPDK publicly on the mailing-list. Even quicker than I initially thought. Soon I’ll try describe my setup and steps I had to go through that are still in my memory. At least one issue that I’ve got to resolve wasn’t on the mailing-list and in the howtos.

Best Regards,
Piotr Krysik


This is totally valuable work, I don't want to diminish that at all.

But your post might leave some with the impression that Gnu Radio isn't doing enough to "notice" when it's using cores
  that DPDK needs, and that's the kernel's job...


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