On Tue, Jan 27, 2015 at 10:51 AM, Alexander Belyakov <abelyako at gmail.com> wrote:
> > Hi Pablo, > > On Mon, Jan 26, 2015 at 5:22 PM, De Lara Guarch, Pablo < > pablo.de.lara.guarch at intel.com> wrote: > >> Hi Alexander, >> >> > -----Original Message----- >> > From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Alexander Belyakov >> > Sent: Monday, January 26, 2015 10:18 AM >> > To: dev at 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. > > Managed to get testpmd from dpdk-1.8.0 to work on my setup. Unfortunately I had to disable RTE_LIBRTE_IXGBE_RX_ALLOW_BULK_ALLOC, it is new comparing to 1.7.1 and somehow breaks testpmd forwarding. By the way, simply disabling RTE_LIBRTE_IXGBE_RX_ALLOW_BULK_ALLOC in common_linuxapp config file breaks the build - had to make quick'n'dirty fix in struct igb_rx_queue as well. Anyway, issue is still here. Forwarding 80 bytes packets at 12.4 Mpps. Forwarding 81 bytes packets at 7.2 Mpps. Any ideas? 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 >> > > >
