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Date: Sun, 18 Jan 2015 18:22:33 +0200 From: Eyal Perry <eyalpe@....mellanox.co.il> To: Eric Dumazet <eric.dumazet@...il.com> Cc: Or Gerlitz <gerlitz.or@...il.com>, Linux Netdev List <netdev@...r.kernel.org>, Amir Vadai <amirv@...lanox.com>, Yevgeny Petrilin <yevgenyp@...lanox.com>, Saeed Mahameed <saeedm@...lanox.com>, Ido Shamay <idos@...lanox.com>, Amir Ancel <amira@...lanox.com>, Eyal Perry <eyalpe@...lanox.com> Subject: Re: BW regression after "tcp: refine TSO autosizing" On Wed, Jan 14, 2015 at 12:00 AM, Eric Dumazet <eric.dumazet@...il.com> wrote: > Make sure you do not drop packets at receiver. (Patch might have increased raw speed, and receiver starts dropping packets because it is not able to sustain line rate on a single flow) Hi Eric, I double checked that there are no drops on the receiver (ifconfig, ethtool, and net_dropmonitor). > If cwnd is too small, then yes, sending slightly smaller TSO packets can impact performance, but this is desirable as well. This is a congestion control problem. How can we reliably measure the cwnd? tpci_snd_cwnd is not consistent across runs. Anyway, we don't see difference in the TSO packets size (see results below). > lpaa23:~# nstat >/dev/null; DUMP_TCP_INFO=1 ./netperf -H lpaa24;nstat [...] > > You also can see in this sample Hystart ended slow start with a very small cwnd of 70 We see the issue also on very long runs so I don't understand how is it related to the slow start mechanism. Below, are two measurements with all the statistics. * with your patch: $ nstat >/dev/null; netperf -H remote;nstat MIGRATED TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 11.11.11.36 () port 0 AF_INET tcpi_rto 204000 tcpi_ato 0 tcpi_pmtu 1500 tcpi_rcv_ssthresh 29200 tcpi_rtt 79 tcpi_rttvar 14 tcpi_snd_ssthresh 214 tpci_snd_cwnd 634 tcpi_reordering 3 tcpi_total_retrans 0 Recv Send Send Socket Socket Message Elapsed Size Size Size Time Throughput bytes bytes bytes secs. 10^6bits/sec 87380 16384 16384 10.00 18537.46 #kernel IpInReceives 260728 0.0 IpInDelivers 260728 0.0 IpOutRequests 355684 0.0 TcpActiveOpens 2 0.0 TcpInSegs 260729 0.0 TcpOutSegs 16004157 0.0 UdpInDatagrams 1 0.0 UdpOutDatagrams 7 0.0 UdpIgnoredMulti 1 0.0 Ip6InReceives 4 0.0 Ip6InDelivers 4 0.0 Ip6OutRequests 3 0.0 Ip6InMcastPkts 1 0.0 Ip6InOctets 288 0.0 Ip6OutOctets 856 0.0 Ip6InMcastOctets 72 0.0 Ip6InNoECTPkts 4 0.0 Icmp6InMsgs 1 0.0 Icmp6InNeighborAdvertisements 1 0.0 Icmp6InType136 1 0.0 TcpExtDelayedACKs 2 0.0 TcpExtTCPHPHits 3 0.0 TcpExtTCPPureAcks 208131 0.0 TcpExtTCPHPAcks 52591 0.0 TcpExtTCPAutoCorking 49920 0.0 TcpExtTCPOrigDataSent 16004146 0.0 TcpExtTCPHystartTrainDetect 1 0.0 TcpExtTCPHystartTrainCwnd 214 0.0 IpExtInBcastPkts 1 0.0 IpExtInOctets 13560399 0.0 IpExtOutOctets 23192484354 0.0 IpExtInBcastOctets 367 0.0 IpExtInNoECTPkts 260728 0.0 * And without it: $ nstat >/dev/null; netperf -H remote;nstat MIGRATED TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 11.11.11.37 () port 0 AF_INET tcpi_rto 204000 tcpi_ato 0 tcpi_pmtu 1500 tcpi_rcv_ssthresh 29200 tcpi_rtt 108 tcpi_rttvar 13 tcpi_snd_ssthresh 801 tpci_snd_cwnd 809 tcpi_reordering 64 tcpi_total_retrans 6 Recv Send Send Socket Socket Message Elapsed Size Size Size Time Throughput bytes bytes bytes secs. 10^6bits/sec 87380 16384 16384 10.00 26826.32 #kernel IpInReceives 431716 0.0 IpInDelivers 431716 0.0 IpOutRequests 521537 0.0 TcpActiveOpens 2 0.0 TcpInSegs 431676 0.0 TcpOutSegs 23164903 0.0 TcpRetransSegs 6 0.0 UdpInDatagrams 3 0.0 UdpOutDatagrams 1 0.0 UdpIgnoredMulti 40 0.0 Ip6InReceives 4 0.0 Ip6InDelivers 4 0.0 Ip6OutRequests 4 0.0 Ip6InOctets 288 0.0 Ip6OutOctets 928 0.0 Ip6InNoECTPkts 4 0.0 Icmp6InMsgs 1 0.0 Icmp6OutMsgs 1 0.0 Icmp6InNeighborAdvertisements 1 0.0 Icmp6OutNeighborSolicits 1 0.0 Icmp6InType136 1 0.0 Icmp6OutType135 1 0.0 TcpExtDelayedACKs 1 0.0 TcpExtTCPHPHits 2 0.0 TcpExtTCPPureAcks 291894 0.0 TcpExtTCPHPAcks 139775 0.0 TcpExtTCPSackRecovery 5 0.0 TcpExtTCPTSReorder 1 0.0 TcpExtTCPPartialUndo 1 0.0 TcpExtTCPDSACKUndo 4 0.0 TcpExtTCPFastRetrans 6 0.0 TcpExtTCPDSACKRecv 6 0.0 TcpExtTCPDSACKIgnoredNoUndo 1 0.0 TcpExtTCPSackShifted 46436 0.0 TcpExtTCPSackMerged 1306 0.0 TcpExtTCPSackShiftFallback 4414 0.0 TcpExtTCPAutoCorking 274120 0.0 TcpExtTCPOrigDataSent 23164893 0.0 TcpExtTCPHystartTrainDetect 1 0.0 TcpExtTCPHystartTrainCwnd 71 0.0 IpExtInBcastPkts 42 0.0 IpExtInOctets 23066435 0.0 IpExtOutOctets 33567160556 0.0 IpExtInBcastOctets 4275 0.0 IpExtInNoECTPkts 431716 0.0 Please let me know if you see something in the results. Regards, Eyal. -- 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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