Re: [dpdk-users] Packet losses using DPDK

[dfernandes@toulouse.viveris.com]

Hi !

I performed many tests using Pktgen and it seems to work much better. 
However, I observed that one of the tests showed that 2 packets were 
dropped. In this test I sent packets between the 2 physical ports in 
bidirectional mode during 24 hours. The packets size was 450 bytes and 
the rate in both ports was 1500 Mbps.

The port stats I got are the following :


** Port 0 **  Tx: 34481474912. Rx: 34481474846. Dropped: 2
** Port 1 **  Tx: 34481474848. Rx: 34481474912. Dropped: 0

DEBUG portStats = {
   [1] = {
     ["ipackets"] = 34481474912,
     ["ierrors"] = 0,
     ["rx_nombuf"] = 0,
     ["ibytes"] = 15378737810752,
     ["oerrors"] = 0,
     ["opackets"] = 34481474848,
     ["obytes"] = 15378737782208,
   },
   [0] = {
     ["ipackets"] = 34481474846,
     ["ierrors"] = 1,
     ["rx_nombuf"] = 0,
     ["ibytes"] = 15378737781316,
     ["oerrors"] = 0,
     ["opackets"] = 34481474912,
     ["obytes"] = 15378737810752,
   },
   ["n"] = 2,
}

So 2 packets were dropped by port 0 and I see that "ierrors" counter has 
a value of 1. Do you know what does this counter represent ? And what 
could it be interpreted ?
By the way, I performed as well the same test changing the packet size 
to 1518 bytes and the rate to 4500 Mbps (on each port) and 0 packets 
were dropped.

David



Le 17.05.2017 09:53, dfernandes@toulouse.viveris.com a écrit :
> Thanks for your response !
> 
> I have installed Pktgen and I will perform some tests. So far it seems
> to work fine. I'll keep you informed. Thanks again.
> 
> David
> 
> Le 12.05.2017 18:18, Wiles, Keith a écrit :
>>> On May 12, 2017, at 10:45 AM, dfernandes@toulouse.viveris.com wrote:
>>> 
>>> Hi !
>>> 
>>> I am working with MoonGen which is a fully scriptable packet 
>>> generator build on DPDK.
>>> (→ https://github.com/emmericp/MoonGen)
>>> 
>>> The system on which I perform tests has the following characteristics 
>>> :
>>> 
>>> CPU : Intel Core i3-⁠⁠6100 (3.70 GHz, 2 cores, 2 threads/⁠⁠core)
>>> NIC : X540-⁠⁠AT2 with 2x10Gbe ports
>>> OS : Linux Ubuntu Server 16.04 (kernel 4.4)
>>> 
>>> I coded a MoonGen script which requests DPDK to transmit packets from 
>>> one physical port and to receive them at the second physical port. 
>>> The 2 physical ports are directly connected with an RJ-45 cat6 cable.
>>> 
>>> The issue is that I perform the same test with exactly the same 
>>> script and the same parameters several times and the results show a 
>>> random behavior. For most of the tests there is no losses but for 
>>> some of them I observe packet losses. The percentage of lost packets 
>>> is very variable. It happens even when the packet rate is very low.
>>> 
>>> Some examples of random failed tests :
>>> 
>>> # 1,000,000 packets sent (packets size = 124 bytes, rate = 76 Mbps) → 
>>> 10170 lost packets
>>> 
>>> # 3,000,000 packets sent (packets size = 450 bytes, rate = 460 Mbps) 
>>> → ALL packets lost
>>> 
>>> 
>>> I tested the following system modifications without success :
>>> 
>>> # BIOS parameters :
>>> 
>>>    Hyperthreading : enable (because the machine has only 2 cores)
>>>    Multi-⁠⁠⁠processor : enable
>>>    Virtualization Technology (VTx) : disable
>>>    Virtualization Technology for Directed I/⁠⁠⁠O (VTd) : disable
>>>    Allow PCIe/⁠⁠⁠PCI SERR# Interrupt (=PCIe System Errors) : disable
>>>    NUMA unavailable
>>> 
>>> # use of isolcpus in order to isolate the cores which are in charge 
>>> of transmission and reception
>>> 
>>> # hugepages size = 1048576 kB
>>> 
>>> # size of buffer descriptors : tried with Tx = 512 descriptors and Rx 
>>> = 128 descriptors and also with  Tx = 4096 descriptors and Rx = 4096  
>>> descriptors
>>> 
>>> # Tested with 2 different X540-⁠⁠T2 NICs units
>>> 
>>> # I tested all with a Dell FC430 which has a CPU Intel Xeon E5-2660 
>>> v3 @ 2.6GHz with 10 Cores and 2threads/Core (tested with and without 
>>> hyper-threading)
>>>    → same results and even worse
>>> 
>>> 
>>> Remark concerning the NIC stats :
>>>     I used the rte_eth_stats struct in order to get more information 
>>> about the losses and I observed that in some cases, when there is 
>>> packet losses,  ierrors value is > 0 and also ierrors + imissed + 
>>> ipackets < opackets. In other cases I get ierrors = 0 and  imissed + 
>>> ipackets = opackets which has more sense.
>>> 
>>> What could be the origin of that erroneous packets counting?
>>> 
>>> Do you have any explanation about that behaviour ?
>> 
>> Not knowing MoonGen at all other then a brief look at the source I may
>> not be much help, but I have a few ideas to help locate the problem.
>> 
>> Try using testpmd in tx-only mode or try Pktgen to see if you get the
>> same problem. I hope this would narrow down the problem to a specific
>> area. As we know DPDK works if correctly coded and testpmd/pktgen
>> work.
>> 
>>> 
>>> Thanks in advance.
>>> 
>>> David
>> 
>> Regards,
>> Keith