[dpdk-users] Packet losses using DPDK

[dfernandes at toulouse.viveris.com]

Hi Andriy !

Thanks for your response.

Yes, I wait links are up.

David


Le 15.05.2017 10:25, Andriy Berestovskyy a écrit :
> Hey,
> It might be a silly guess, but do you wait for the links are up and
> ready to send/receive packets?
> 
> Andriy
> 
> On Fri, May 12, 2017 at 5:45 PM,  <dfernandes at 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 ?
>> 
>> Thanks in advance.
>> 
>> David