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. Actually, have you tried using 1.8.0? Pablo > > Regards, > Alexander Belyakov
