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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