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

[Alexander Kozyrev <akozyrev@mellanox.com>]

<snip>
> 
> > > > 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.
> You are running on A72 cores, is that correct?

Correct, cat /proc/cpuinfo
processor       : 0
BogoMIPS        : 312.50
Features        : fp asimd evtstrm crc32 cpuid
CPU implementer : 0x41
CPU architecture: 8
CPU variant     : 0x0
CPU part        : 0xd08
CPU revision    : 3