[dpdk-dev] Fwd: DPDK testpmd forwarding performace degradation

[Alexander Belyakov <abelyako@gmail.com>]

Hi Pablo,

On Mon, Jan 26, 2015 at 5:22 PM, De Lara Guarch, Pablo <
pablo.de.lara.guarch@intel.com> wrote:

> Hi Alexander,
>
> > -----Original Message-----
> > From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Alexander Belyakov
> > Sent: Monday, January 26, 2015 10:18 AM
> > To: dev@dpdk.org
> > Subject: [dpdk-dev] DPDK testpmd forwarding performace degradation
> >
> > Hello,
> >
> > recently I have found a case of significant performance degradation for
> our
> > application (built on top of DPDK, of course). Surprisingly, similar
> issue
> > is easily reproduced with default testpmd.
> >
> > To show the case we need simple IPv4 UDP flood with variable UDP payload
> > size. Saying "packet length" below I mean: Eth header length (14 bytes) +
> > IPv4 header length (20 bytes) + UPD header length (8 bytes) + UDP payload
> > length (variable) + CRC (4 bytes). Source IP addresses and ports are
> selected
> > randomly for each packet.
> >
> > I have used DPDK with revisions 1.6.0r2 and 1.7.1. Both show the same
> issue.
> >
> > Follow "Quick start" guide (http://dpdk.org/doc/quick-start) to build
> and
> > run testpmd. Enable testpmd forwarding ("start" command).
> >
> > Table below shows measured forwarding performance depending on packet
> > length:
> >
> > No. -- UDP payload length (bytes) -- Packet length (bytes) -- Forwarding
> > performance (Mpps) -- Expected theoretical performance (Mpps)
> >
> > 1. 0 -- 64 -- 14.8 -- 14.88
> > 2. 34 -- 80 -- 12.4 -- 12.5
> > 3. 35 -- 81 -- 6.2 -- 12.38 (!)
> > 4. 40 -- 86 -- 6.6 -- 11.79
> > 5. 49 -- 95 -- 7.6 -- 10.87
> > 6. 50 -- 96 -- 10.7 -- 10.78 (!)
> > 7. 60 -- 106 -- 9.4 -- 9.92
> >
> > At line number 3 we have added 1 byte of UDP payload (comparing to
> > previous
> > line) and got forwarding performance halved! 6.2 Mpps against 12.38 Mpps
> > of
> > expected theoretical maximum for this packet size.
> >
> > That is the issue.
> >
> > Significant performance degradation exists up to 50 bytes of UDP payload
> > (96 bytes packet length), where it jumps back to theoretical maximum.
> >
> > What is happening between 80 and 96 bytes packet length?
> >
> > This issue is stable and 100% reproducible. At this point I am not sure
> if
> > it is DPDK or NIC issue. These tests have been performed on Intel(R) Eth
> > Svr Bypass Adapter X520-LR2 (X520LR2BP).
> >
> > Is anyone aware of such strange behavior?
>
> I cannot reproduce the issue using two ports on two different 82599EB
> NICs, using 1.7.1 and 1.8.0.
> I always get either same or better linerate as I increase the packet size.
>

Thank you for trying to reproduce the issue.


> Actually, have you tried using 1.8.0?
>

I feel 1.8.0 is little bit immature and might require some post-release
patching. Even tespmd from this release is not forwarding packets properly
on my setup. It is up and running without visible errors/warnings, TX/RX
counters are ticking but I can not see any packets at the output. Please
note, both 1.6.0r2 and 1.7.1 releases work (on the same setup)
out-of-the-box just fine with only exception of this mysterious performance
drop.

So it will take some time to figure out what is wrong with dpdk-1.8.0.
Meanwhile we could focus on stable dpdk-1.7.1.

As for X520-LR2 NIC - it is dual port bypass adapter with device id 155d. I
believe it should be treated as 82599EB except bypass feature. I put bypass
mode to "normal" in those tests.

Alexander


>
> Pablo
> >
> > Regards,
> > Alexander Belyakov
>