[dpdk-dev] Rx-errors with testpmd (only 75% line rate)

Dmitry Vyal dmitryvyal at gmail.com
Wed Jan 22 15:52:00 CET 2014

Hello MIchael,

I suggest you to check average burst sizes on receive queues. Looks like 
I stumbled upon a similar issue several times. If you are calling 
rte_eth_rx_burst too frequently, NIC begins losing packets no matter how 
many CPU horse power you have (more you have, more it loses, actually). 
In my case this situation occured when average burst size is less than 
20 packets or so. I'm not sure what's the reason for this behavior, but 
I observed it on several applications on Intel 82599 10Gb cards.

Regards, Dmitry

On 01/09/2014 11:28 PM, Michael Quicquaro wrote:
> Hello,
> My hardware is a Dell PowerEdge R820:
> 4x Intel Xeon E5-4620 2.20GHz 8 core
> 16GB RDIMM 1333 MHz Dual Rank, x4 - Quantity 16
> Intel X520 DP 10Gb DA/SFP+
> So in summary 32 cores @ 2.20GHz and 256GB RAM
> ... plenty of horsepower.
> I've reserved 16 1GB Hugepages
> I am configuring only one interface and using testpmd in rx_only mode to
> first see if I can receive at line rate.
> I am generating traffic on a different system which is running the netmap
> pkt-gen program - generating 64 byte packets at close to line rate.
> I am only able to receive approx. 75% of line rate and I see the Rx-errors
> in the port stats going up proportionally.
> I have verified that all receive queues are being used, but strangely
> enough, it doesn't matter how many queues more than 2 that I use, the
> throughput is the same.  I have verified with 'mpstat -P ALL' that all
> specified cores are used.  The utilization of each core is only roughly 25%.
> Here is my command line:
> testpmd -c 0xffffffff -n 4 -- --nb-ports=1 --coremask=0xfffffffe
> --nb-cores=8 --rxd=2048 --txd=2048 --mbcache=512 --burst=512 --rxq=8
> --txq=8 --interactive
> What can I do to trace down this problem?  It seems very similar to a
> thread on this list back in May titled "Best example for showing
> throughput?" where no resolution was ever mentioned in the thread.
> Thanks for any help.
> - Michael

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