Re: [dpdk-users] Packet losses using DPDK

[Andriy Berestovskyy <aber@semihalf.com>]

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@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



-- 
Andriy Berestovskyy