[dpdk-dev] [PATCH v3] net/mlx5: relaxed ordering for multi-packet RQ buffer refcnt

[Alexander Kozyrev]

> Phil Yang <Phil.Yang at arm.com> writes:
> 
> <...>
> > Subject: RE: [dpdk-dev] [PATCH v3] net/mlx5: relaxed ordering for
> > multi- packet RQ buffer refcnt
> >
> > Hi Phil Yang, we noticed that this patch gives us 10% of performance
> > degradation on ARM.
> > x86 seems to be unaffected though. Do you know what may be the reason
> > of this behavior?
> 
> Hi Alexander,
> 
> Thanks for your feedback.
> This patch removed some expensive memory barriers on aarch64, it should get
> better performance.
> I am not sure the root cause of this degradation now, I will start the
> investigation. We can profiling this issue together.
> Could you share your test case(including your testbed configuration) with us?
> 
> Thanks,
> Phil

I'm surprised too, Phil, but looks like it is actually making things worse. I used Connect-X 6DX on aarch64:
Linux dragon71-bf 5.4.31-mlnx.15.ge938819 #1 SMP PREEMPT Thu Jul 2 17:01:15 IDT 2020 aarch64 aarch64 aarch64 GNU/Linux
Traffic generator sends 60 bytes packets and DUT executes the following command:
arm64-bluefield-linuxapp-gcc/build/app/test-pmd/testpmd -n 4  -w 0000:03:00.1,mprq_en=1,rxqs_min_mprq=1  -w 0000:03:00.0,mprq_en=1,rxqs_min_mprq=1 -c 0xe  -- --burst=64 --mbcache=512 -i  --nb-cores=1  --rxq=1 --txq=1 --txd=256 --rxd=256  --auto-start --rss-udp
Without a patch I'm getting 3.2mpps, and only 2.9mpps when the patch is applied.

Regards,
Alex