Re: [E1000-devel] A lot of TCP Packets drop when only with ACK flag

[周介龙 <dil...@12...>]

Hi Alex,
    thanks for your reply. I used an Agilent N2X packet generator to generate and send TCP packets. The generator could be configured to send all kinds of network packets. I configured it to send 150 byte long TCP packets, 7.35M packets per second (about 10Gbps). The sended TCP packets have normal format:
EthernetHeader + IPHeader + TCPHeader + TCPPayload
 
The TCP header of packets is configured as below:(every sended packet has same configuration)
TCP Header:
        Source port:                                 [1-2000, Increment]
        Destination port:                          [1-2000, Increment]
        Sequence number                       0
        Ackowledge number                    0
        Data offset:                                  5
        Reserved:                                   0x00
        Code Bits:
                 URG:                                  0
                 ACK:                                  1
                 PSH:                                  0
                 RST:                                  0
                 SYN:                                  0
                 FIN:                                   0
         Window Size:                             0
         Checksum:                                0x2D71 (automated, differ from packet)
         Urgent pointer:                          0
         TCP options:                             None
 
Sending packets with above configuration causes a lot of rx_missed_error(drop) at the receiving 82599 NIC. But if I just set any flag(in Code Bits field) other than ACK to 1, there would be no errors or drops.
 
Thanks,If any other info is needed, please let me known.
Dillan
 
在 2012-12-21 02:03:15，"Alexander Duyck" <ale...@in...> 写道：
>On 12/20/2012 05:56 AM, 周介龙 wrote:
>> Hi all,
>>     I am testing the receive side performance of a 82599EB NIC, using the newest stable driver ixgbe3.11. When receiving 10Gbps tcp pkts with (and only with) ACK flag, I found a lot of drop statistics in the result of ifconfig command and rx_missed_error in the result of ethtool -S. And the cpu utilized percent if less than 40%. If tcp pkts have any flag other than ACK, or have any optional tcp header, the NIC would never drop any pkts. I think it may be caused by RSC feature, but after disabling RSC by "ethtool -C eth* rx-usecs 0" or adding MACRO "-DIXGBE_NO_HW_RSC" in Makefile, the NIC still drops pkts. Also, the RFCTL.RSC_DIS register can not be set to 1. I have also run the same test on different motherboards, CPUs, kernels, and drivers, and got the same result... This problem has been puzzling me for a few months, is there any way to solve it?
>>     Thanks,
>> Dillan Zhou
>>
>
>Hi Dillan,
>
>It would help if you could explain your test setup.  For example how is
>it you are generating the TCP frames with the ACK flag set?  Also what
>rate is it you are sending these packets at?
>
>Thanks,
>
>Alex