Date:	Wed, 30 May 2012 08:28:11 +0200
From:	Jean-Michel Hautbois <jhautbois@...il.com>
To:	netdev <netdev@...r.kernel.org>
Subject: Re: Difficulties to get 1Gbps on be2net ethernet card

2012/5/29 Jean-Michel Hautbois <jhautbois@...il.com>:
> Hi list,
>
> I am using a NC553i ethernet card connected on a HP 10GbE Flex-10.
> I am sending UDP multicast packets from one blade to another (HP
> ProLiant BL460c G7) which has stricly the same HW.
>
> I have lots of packet loss from Tx to Rx, and I can't understand why.
> I suspected TX coalescing but since 3.4 I can't set this parameter
> (and adaptive-tx is on by default).
> I have tried the same test with a debian lenny (2.6.26 kernel and HP
> drivers) and it works very well (adaptive-tx is off).
>
> Here is the netstat (from Tx point of view) :
>
> $> netstat -s eth1 > before ; sleep 10 ; netstat -s eth1 > after
> $> beforeafter before after
> Ip:
>    280769 total packets received
>    4 with invalid addresses
>    0 forwarded
>    0 incoming packets discarded
>    275063 incoming packets delivered
>    305430 requests sent out
>    0 dropped because of missing route
> Icmp:
>    0 ICMP messages received
>    0 input ICMP message failed.
>    ICMP input histogram:
>        destination unreachable: 0
>        echo requests: 0
>    0 ICMP messages sent
>    0 ICMP messages failed
>    ICMP output histogram:
>        destination unreachable: 0
>        echo replies: 0
> IcmpMsg:
>        InType3: 0
>        InType8: 0
>        OutType0: 0
>        OutType3: 0
> Tcp:
>    18 active connections openings
>    18 passive connection openings
>    0 failed connection attempts
>    0 connection resets received
>    0 connections established
>    3681 segments received
>    3650 segments send out
>    0 segments retransmited
>    0 bad segments received.
>    0 resets sent
> Udp:
>    12626 packets received
>    0 packets to unknown port received.
>    0 packet receive errors
>    259025 packets sent
> UdpLite:
> TcpExt:
>    0 invalid SYN cookies received
>    0 packets pruned from receive queue because of socket buffer overrun
>    14 TCP sockets finished time wait in fast timer
>    0 packets rejects in established connections because of timestamp
>    61 delayed acks sent
>    0 delayed acks further delayed because of locked socket
>    Quick ack mode was activated 0 times
>    2924 packets directly queued to recvmsg prequeue.
>    32 bytes directly in process context from backlog
>    48684 bytes directly received in process context from prequeue
>    232 packet headers predicted
>    1991 packets header predicted and directly queued to user
>    132 acknowledgments not containing data payload received
>    2230 predicted acknowledgments
>    0 times recovered from packet loss by selective acknowledgements
>    0 congestion windows recovered without slow start after partial ack
>    0 TCP data loss events
>    0 timeouts after SACK recovery
>    0 fast retransmits
>    0 forward retransmits
>    0 retransmits in slow start
>    0 other TCP timeouts
>    1 times receiver scheduled too late for direct processing
>    0 packets collapsed in receive queue due to low socket buffer
>    0 DSACKs sent for old packets
>    0 DSACKs received
>    0 connections reset due to unexpected data
>    0 connections reset due to early user close
>    0 connections aborted due to timeout
>    0 times unabled to send RST due to no memory
>    TCPSackShifted: 0
>    TCPSackMerged: 0
>    TCPSackShiftFallback: 0
>    TCPBacklogDrop: 0
>    TCPDeferAcceptDrop: 0
> IpExt:
>    InMcastPkts: -652745397
>    OutMcastPkts: 301498
>    InBcastPkts: 13
>    InOctets: -2004227752
>    OutOctets: -2096666083
>    InMcastOctets: 1058181285
>    OutMcastOctets: -1510963815
>    InBcastOctets: 1014
>
> And ethtool diff :
> $> ethtool -S eth1 > before ; sleep 10 ; ethtool -S eth1 > after
> $> beforeafter before after
> NIC statistics:
>     rx_crc_errors: 0
>     rx_alignment_symbol_errors: 0
>     rx_pause_frames: 0
>     rx_control_frames: 0
>     rx_in_range_errors: 0
>     rx_out_range_errors: 0
>     rx_frame_too_long: 0
>     rx_address_mismatch_drops: 6
>     rx_dropped_too_small: 0
>     rx_dropped_too_short: 0
>     rx_dropped_header_too_small: 0
>     rx_dropped_tcp_length: 0
>     rx_dropped_runt: 0
>     rxpp_fifo_overflow_drop: 0
>     rx_input_fifo_overflow_drop: 0
>     rx_ip_checksum_errs: 0
>     rx_tcp_checksum_errs: 0
>     rx_udp_checksum_errs: 0
>     tx_pauseframes: 0
>     tx_controlframes: 0
>     rx_priority_pause_frames: 0
>     pmem_fifo_overflow_drop: 0
>     jabber_events: 0
>     rx_drops_no_pbuf: 0
>     rx_drops_no_erx_descr: 0
>     rx_drops_no_tpre_descr: 0
>     rx_drops_too_many_frags: 0
>     forwarded_packets: 0
>     rx_drops_mtu: 0
>     eth_red_drops: 0
>     be_on_die_temperature: 0
>     rxq0: rx_bytes: 0
>     rxq0: rx_pkts: 0
>     rxq0: rx_compl: 0
>     rxq0: rx_mcast_pkts: 0
>     rxq0: rx_post_fail: 0
>     rxq0: rx_drops_no_skbs: 0
>     rxq0: rx_drops_no_frags: 0
>     txq0: tx_compl: 257113
>     txq0: tx_bytes: 1038623935
>     txq0: tx_pkts: 257113
>     txq0: tx_reqs: 257113
>     txq0: tx_wrbs: 514226
>     txq0: tx_stops: 10
>
> As you can see, there is 10 tx_stops in 10 seconds (it varies, can be 3 to 15).
> Any thoughts ?
>
> Regards,
> JM

If this can help, setting tx queue length to 5000 seems to make the
problem disappear.
I didn't specified it : MTU is 4096, UDP packets are 4000 bytes.

JM
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