[dpdk-users] DPDK Distributor app issues

George Yaneff gesha2 at abv.bg
Tue Jun 11 08:40:13 CEST 2019


Harry, thank you for the answer.
 I will look into this event dev lib, but I hoped my time with the distributor lib will not be wasted. Actually  it pretty much fits into my use case.
  
  About the packet loss I suspect that they are always the first one or two packets, I'm still debugging and trying to  figure out what really happens.  
  About the delay - unfortunately the cycles in the worker are not the cause for them. When I comment these lines  there is no effect on the delay. Also these is some buffering happening in the tx_core but the reason is not there also.  I suspect some buffering happens internally in the distributor itself.  I understand that the throughput is traded for bigger latency, but hoped there will be a way to tune this.  
  Regards  George  
  
  
  







 >-------- Оригинално писмо --------

 >От: "Van Haaren, Harry" harry.van.haaren at intel.com

 >Относно: RE: [dpdk-users] DPDK Distributor app issues

 >До: George Yaneff  , "users at dpdk.org"  

 >Изпратено на: 10.06.2019 19:13


> -----Original Message-----

> From: users [mailto:users-bounces at dpdk.org] On Behalf Of George Yaneff

> Sent: Monday, June 10, 2019 3:40 PM

> To:  users at dpdk.org 

> Subject: [dpdk-users] DPDK Distributor app issues

> 

> I'm playing with the distributor example application from dpdk 19.05.0



Ah cool - Not sure what your goal is, but if you're looking for the

more future-proof load-balancing / distribution APIs in DPDK the I

recommend to look at the Eventdev library, as this has been added to

DPDK for more "pipelined" applications and load-balancing within those

pipeline stages.



If you know your use case matches distributor library, and are aware of

the existence of Eventdev libs, please ignore the above :)



> I

> have three machines connected sequentially with an UTP Ethernet cable. The

>   middle is Ubuntu 18.04.2 LTS with a eigth core Intel I7 processor and 24

> GB ram.  The eth device used is Intel I350 with four ports.

>

>   The strange behavior I'm observing is when I ping the second node from the

> first node (traffic passing through the distributor)  there are always one

> or two packets lost.

>   When I use

> l2fwd or

> basicfwd applications there is no packet loss.  Anyone knows if this is

> normal or if it is not - what I'm doing wrong?



This seems strange - although I'm not very familiar with Distributor sample app.



Perhaps add some statistics counters around the "rte_pktmbuf_free()" calls in

the sample app, to identify if the sample-app is dropping packets in SW, or if

the root cause is really platform configuration?





>   Another thing I noticed is that the ping replies come to the first node

> with around one second of delay. (1024ms on most packets)  Again there is no

> latency with the basicfwd (packets arriving in 0.101 ms there).  Is there

> any way to minimize this delay in distributor application also?



The sample application adds artificial "work" per packet to simulate a real

world distributing workload:

 http://git.dpdk.org/dpdk/tree/examples/distributor/main.c#n574 



Per packet, 100 cycles of work is performed, so eg:

(burst-size # of packets * 100 cycles) @ CPU freq + RX, TX and Distributor

work will be the total delay along the wire.





>   George



Hope that helps, -Harry

   


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