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Date: Wed, 18 Dec 2013 17:43:50 +0100 From: Hector Palacios <hector.palacios@...i.com> To: Marek Vasut <marex@...x.de>, "netdev@...r.kernel.org" <netdev@...r.kernel.org> CC: "fabio.estevam@...escale.com" <fabio.estevam@...escale.com>, "shawn.guo@...aro.org" <shawn.guo@...aro.org>, <l.stach@...gutronix.de>, Frank Li <Frank.Li@...escale.com>, <fugang.duan@...escale.com>, <bhutchings@...arflare.com>, "davem@...emloft.net" <davem@...emloft.net> Subject: Re: FEC performance degradation with certain packet sizes Hello, I'm resending this thread (reworded the subject) with additional people on CC. I found the issue happens also with auto-negotiated link and is reproducible on the i.MX6 as well as on the i.MX28. It looks like a problem with the fec driver. Steps to reproduce: On the target: netpipe On the host: netpipe -h <target_ip> -n 5 At certain packet sizes (starting always at 1533 bytes), the performance drops dramatically: On i.MX28: [...] 42: 771 bytes 5 times --> 19.78 Mbps in 297.41 usec 43: 1021 bytes 5 times --> 23.29 Mbps in 334.41 usec 44: 1024 bytes 5 times --> 23.61 Mbps in 330.90 usec 45: 1027 bytes 5 times --> 23.43 Mbps in 334.41 usec 46: 1533 bytes 5 times --> 0.13 Mbps in 88817.49 usec 47: 1536 bytes 5 times --> 0.06 Mbps in 189914.91 usec 48: 1539 bytes 5 times --> 0.06 Mbps in 204917.19 usec 49: 2045 bytes 5 times --> 0.07 Mbps in 210931.79 usec 50: 2048 bytes 5 times --> 0.07 Mbps in 210919.10 usec 51: 2051 bytes 5 times --> 0.07 Mbps in 212915.71 usec 52: 3069 bytes 5 times --> 35.42 Mbps in 661.01 usec 53: 3072 bytes 5 times --> 35.57 Mbps in 659.00 usec 54: 3075 bytes 5 times --> 35.42 Mbps in 662.29 usec 55: 4093 bytes 5 times --> 40.03 Mbps in 780.19 usec 56: 4096 bytes 5 times --> 40.75 Mbps in 766.79 usec 57: 4099 bytes 5 times --> 40.64 Mbps in 769.49 usec 58: 6141 bytes 5 times --> 3.08 Mbps in 15187.90 usec 59: 6144 bytes 5 times --> 2.94 Mbps in 15928.19 usec 60: 6147 bytes 5 times --> 5.57 Mbps in 8418.91 usec 61: 8189 bytes 5 times --> 1.34 Mbps in 46574.90 usec 62: 8192 bytes 5 times --> 2.17 Mbps in 28781.99 usec 63: 8195 bytes 5 times --> 1.36 Mbps in 45923.69 usec 64: 12285 bytes 5 times --> 51.78 Mbps in 1810.21 usec 65: 12288 bytes 5 times --> 50.46 Mbps in 1857.81 usec 66: 12291 bytes 5 times --> 54.01 Mbps in 1736.21 usec 67: 16381 bytes 5 times --> 55.86 Mbps in 2237.50 usec 68: 16384 bytes 5 times --> 56.93 Mbps in 2195.79 usec 69: 16387 bytes 5 times --> 35.62 Mbps in 3509.60 usec 70: 24573 bytes 5 times --> 7.19 Mbps in 26075.60 usec 71: 24576 bytes 5 times --> 58.36 Mbps in 3212.59 usec 72: 24579 bytes 5 times --> 7.92 Mbps in 23678.90 usec 73: 32765 bytes 5 times --> 58.14 Mbps in 4299.79 usec 74: 32768 bytes 5 times --> 5.34 Mbps in 46810.20 usec 75: 32771 bytes 5 times --> 41.51 Mbps in 6023.21 usec 76: 49149 bytes 5 times --> 49.62 Mbps in 7557.20 usec 77: 49152 bytes 5 times --> 48.82 Mbps in 7681.11 usec On i.MX6: [...] 42: 771 bytes 5 times --> 16.21 Mbps in 362.91 usec 43: 1021 bytes 5 times --> 17.97 Mbps in 433.51 usec 44: 1024 bytes 5 times --> 18.19 Mbps in 429.40 usec 45: 1027 bytes 5 times --> 18.16 Mbps in 431.41 usec 46: 1533 bytes 5 times --> 2.35 Mbps in 4970.11 usec 47: 1536 bytes 5 times --> 2.36 Mbps in 4959.91 usec 48: 1539 bytes 5 times --> 2.37 Mbps in 4959.20 usec 49: 2045 bytes 5 times --> 3.14 Mbps in 4972.31 usec 50: 2048 bytes 5 times --> 3.15 Mbps in 4959.50 usec 51: 2051 bytes 5 times --> 3.15 Mbps in 4960.01 usec 52: 3069 bytes 5 times --> 4.70 Mbps in 4984.19 usec 53: 3072 bytes 5 times --> 4.73 Mbps in 4960.10 usec 54: 3075 bytes 5 times --> 4.73 Mbps in 4957.81 usec 55: 4093 bytes 5 times --> 6.29 Mbps in 4966.71 usec 56: 4096 bytes 5 times --> 6.30 Mbps in 4962.00 usec 57: 4099 bytes 5 times --> 6.31 Mbps in 4957.71 usec 58: 6141 bytes 5 times --> 49.25 Mbps in 951.40 usec 59: 6144 bytes 5 times --> 49.23 Mbps in 952.21 usec 60: 6147 bytes 5 times --> 49.18 Mbps in 953.69 usec Does anyone have any clue about where the problem might be? Best regards, -- Hector Palacios On 11/25/2013 09:56 AM, Hector Palacios wrote: > On 11/24/2013 05:40 AM, Marek Vasut wrote: >> Hi Hector, >> >>> Hello, >>> >>> When forcing the Ethernet PHY link media with ethtool/mii-tool on the >>> i.MX28 I've seen important performance degradation as the packet size >>> increases. >>> >>> On the target: >>> # mii-tool eth0 -F 10baseT-FD >>> # netpipe >>> >>> On the host: >>> # netpipe -h <target-ip> -n 1 >>> ... >>> 44: 1024 bytes 1 times --> 6.56 Mbps in 1191.00 usec >>> 45: 1027 bytes 1 times --> 6.56 Mbps in 1193.52 usec >>> 46: 1533 bytes 1 times --> 0.60 Mbps in 19600.54 usec >>> 47: 1536 bytes 1 times --> 0.46 Mbps in 25262.52 usec >>> 48: 1539 bytes 1 times --> 0.57 Mbps in 20745.54 usec >>> 49: 2045 bytes 1 times --> 0.74 Mbps in 20971.95 usec >>> ... >>> On loop 46, as the packet size exceeds the MTU (1500) performance falls >>> from 6.56Mbps to 0.60Mbps. >>> >>> Going back to 100baseTX-FD, but still forced (autonegotiation off), the >>> same occurs: On the target: >>> # mii-tool eth0 -F 100baseTx-FD >>> # netpipe >>> >>> On the host: >>> # netpipe -h <target-ip> -n 1 >>> ... >>> 58: 6141 bytes 1 times --> 39.74 Mbps in 1179.03 usec >>> 59: 6144 bytes 1 times --> 41.83 Mbps in 1120.51 usec >>> 60: 6147 bytes 1 times --> 41.39 Mbps in 1133.03 usec >>> 61: 8189 bytes 1 times --> 6.36 Mbps in 9823.94 usec >>> 62: 8192 bytes 1 times --> 6.56 Mbps in 9521.46 usec >>> 63: 8195 bytes 1 times --> 6.56 Mbps in 9532.99 usec >>> ... >>> only this time it happens with a larger packet size (8189 bytes). >>> >>> With autonegotiation on, performance is ok and does not suffer these drops. >>> >>> I've reproduced this on the mx28evk board but it also happens in my >>> hardware, with different PHY on v3.10. >>> I also tried on an old v2.6.35 kernel and the issue was reproducible as >>> well, though it happened with larger packet sizes than it happens with >>> v3.10: >>> ... >>> 75: 32771 bytes 1 times --> 49.64 Mbps in 5036.50 usec >>> 76: 49149 bytes 1 times --> 46.18 Mbps in 8120.48 usec >>> 77: 49152 bytes 1 times --> 43.30 Mbps in 8660.46 usec >>> 78: 49155 bytes 1 times --> 40.10 Mbps in 9351.46 usec >>> 79: 65533 bytes 1 times --> 2.03 Mbps in 246061.04 usec >>> 80: 65536 bytes 1 times --> 2.21 Mbps in 226516.50 usec >>> 81: 65539 bytes 1 times --> 1.45 Mbps in 344196.46 usec >>> ... >>> >>> Could there be any issue with packet fragmentation? >>> I tried the same on imx6sabresd but here the issue is not reproducible. I >>> don't know if the higher CPU frequency might be hiding the problem, >>> though. >>> >>> Any idea about what can make the difference between forcing media vs >>> autonegotiation? >> >> Let me ask, this might be unrelated, but I will still go ahead. Do you also >> observe packetloss? You can check with iperf: >> >> On host machine (PC): iperf -u -s -l 4M -i 60 >> On target: iperf -u -c <hostip> -t 3600 -B 100M -i 60 > > Yes, with forced 100baseTX-FD there is a small packet loss: > > [ ID] Interval Transfer Bandwidth Jitter Lost/Total Datagrams > [ 3] 0.0-60.0 sec 339 MBytes 47.4 Mbits/sec 0.075 ms 61/242070 (0.025%) > [ 3] 60.0-120.0 sec 339 MBytes 47.4 Mbits/sec 0.209 ms 45/242122 (0.019%) > [ 3] 120.0-180.0 sec 339 MBytes 47.5 Mbits/sec 0.084 ms 70/242237 (0.029%) > [ 3] 180.0-240.0 sec 339 MBytes 47.4 Mbits/sec 0.030 ms 80/241993 (0.033%) > [ 3] 240.0-300.0 sec 340 MBytes 47.5 Mbits/sec 0.042 ms 111/242363 (0.046%) > [ 3] 300.0-360.0 sec 339 MBytes 47.4 Mbits/sec 0.038 ms 93/241972 (0.038%) > [ 3] 360.0-420.0 sec 339 MBytes 47.5 Mbits/sec 0.030 ms 78/242214 (0.032%) > [ 3] 420.0-480.0 sec 339 MBytes 47.4 Mbits/sec 0.090 ms 77/241980 (0.032%) > [ 3] 480.0-540.0 sec 339 MBytes 47.4 Mbits/sec 0.025 ms 125/242058 (0.052%) > > With autonegotiated 100baseTX-FD, there is not: > > [ ID] Interval Transfer Bandwidth Jitter Lost/Total Datagrams > [ 3] 0.0-60.0 sec 336 MBytes 47.0 Mbits/sec 0.038 ms 0/239673 (0%) > [ 3] 60.0-120.0 sec 337 MBytes 47.1 Mbits/sec 0.078 ms 0/240353 (0%) > [ 3] 120.0-180.0 sec 337 MBytes 47.1 Mbits/sec 0.047 ms 0/240054 (0%) > [ 3] 180.0-240.0 sec 337 MBytes 47.1 Mbits/sec 0.038 ms 0/240195 (0%) > [ 3] 240.0-300.0 sec 337 MBytes 47.1 Mbits/sec 0.038 ms 0/240109 (0%) > [ 3] 300.0-360.0 sec 337 MBytes 47.1 Mbits/sec 0.035 ms 0/240101 (0%) > [ 3] 360.0-420.0 sec 337 MBytes 47.0 Mbits/sec 0.031 ms 0/240032 (0%) > [ 3] 420.0-480.0 sec 336 MBytes 47.0 Mbits/sec 0.036 ms 0/239912 (0%) > > > Best regards, > -- > Hector Palacios -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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