Hi, I've set up a simple packet forwarding perf test on a dual-port 10G 82599ES: one port receives 64 byte UDP packets, the other sends it out, one core used. I've used latest OVS with DPDK 2.1, and the first result was only 13.2 Mpps, which was a bit far from the 13.9 I've seen last year with the same test. The first thing I've changed was to revert back to the old behaviour about this issue:
http://permalink.gmane.org/gmane.comp.networking.dpdk.devel/22731 So instead of the new default I've passed 2048 + RTE_PKTMBUF_HEADROOM. That increased the performance to 13.5, but to figure out what's wrong started to play with the receive functions. First I've disabled vector PMD, but ixgbe_recv_pkts_bulk_alloc() was even worse, only 12.5 Mpps. So then I've enabled scattered RX, and with ixgbe_recv_pkts_lro_bulk_alloc() I could manage to get 13.98 Mpps, which is I guess as close as possible to the 14.2 line rate (on my HW at least, with one core) Does anyone has a good explanation about why the vector PMD performs so significantly worse? I would expect that on a 3.2 GHz i5-4570 one core should be able to reach ~14 Mpps, SG and vector PMD shouldn't make a difference. I've tried to look into it with oprofile, but the results were quite strange: 35% of the samples were from miniflow_extract, the part where parse_vlan calls data_pull to jump after the MAC addresses. The oprofile snippet (1M samples): 511454 19 0.0037 flow.c:511 511458 149 0.0292 dp-packet.h:266 51145f 4264 0.8357 dp-packet.h:267 511466 18 0.0035 dp-packet.h:268 51146d 43 0.0084 dp-packet.h:269 511474 172 0.0337 flow.c:511 51147a 4320 0.8467 string3.h:51 51147e 358763 70.3176 flow.c:99 511482 2 3.9e-04 string3.h:51 511485 3060 0.5998 string3.h:51 511488 1693 0.3318 string3.h:51 51148c 2933 0.5749 flow.c:326 511491 47 0.0092 flow.c:326 And the corresponding disassembled code: 511454: 49 83 f9 0d cmp r9,0xd 511458: c6 83 81 00 00 00 00 mov BYTE PTR [rbx+0x81],0x0 51145f: 66 89 83 82 00 00 00 mov WORD PTR [rbx+0x82],ax 511466: 66 89 93 84 00 00 00 mov WORD PTR [rbx+0x84],dx 51146d: 66 89 8b 86 00 00 00 mov WORD PTR [rbx+0x86],cx 511474: 0f 86 af 01 00 00 jbe 511629 <miniflow_extract+0x279> 51147a: 48 8b 45 00 mov rax,QWORD PTR [rbp+0x0] 51147e: 4c 8d 5d 0c lea r11,[rbp+0xc] 511482: 49 89 00 mov QWORD PTR [r8],rax 511485: 8b 45 08 mov eax,DWORD PTR [rbp+0x8] 511488: 41 89 40 08 mov DWORD PTR [r8+0x8],eax 51148c: 44 0f b7 55 0c movzx r10d,WORD PTR [rbp+0xc] 511491: 66 41 81 fa 81 00 cmp r10w,0x81 My only explanation to this so far is that I misunderstand something about the oprofile results. Regards, Zoltan
