Re: [dpdk-dev] Fwd: high latency detected in IP pipeline example

[James Huang <jamsphon@gmail.com>]

No. We didn't see noticable throughput difference in our test.

On Mon., Feb. 17, 2020, 11:04 p.m. Victor Huertas <vhuertas@gmail.com>
wrote:

> Thanks James for your quick answer.
> I guess that this configuration modification implies that the packets must
> be written one by one in the sw ring. Did you notice loose of performance
> (in throughput) in your aplicación because of that?
>
> Regards
>
> El mar., 18 feb. 2020 0:10, James Huang <jamsphon@gmail.com> escribió:
>
>> Yes, I experienced similar issue in my application. In a short answer,
>> set the swqs write burst value to 1 may reduce the latency significantly.
>> The default write burst value is 32.
>>
>> On Mon., Feb. 17, 2020, 8:41 a.m. Victor Huertas <vhuertas@gmail.com>
>> wrote:
>>
>>> Hi all,
>>>
>>> I am developing my own DPDK application basing it in the dpdk-stable
>>> ip_pipeline example.
>>> At this moment I am using the 17.11 LTS version of DPDK and I amb
>>> observing
>>> some extrange behaviour. Maybe it is an old issue that can be solved
>>> quickly so I would appreciate it if some expert can shade a light on
>>> this.
>>>
>>> The ip_pipeline example allows you to develop Pipelines that perform
>>> specific packet processing functions (ROUTING, FLOW_CLASSIFYING, etc...).
>>> The thing is that I am extending some of this pipelines with my own.
>>> However I want to take advantage of the built-in ip_pipeline capability
>>> of
>>> arbitrarily assigning the logical core where the pipeline (f_run()
>>> function) must be executed so that i can adapt the packet processing
>>> power
>>> to the amount of the number of cores available.
>>> Taking this into account I have observed something strange. I show you
>>> this
>>> simple example below.
>>>
>>> Case 1:
>>> [PIPELINE 0 MASTER core =0]
>>> [PIPELINE 1 core=1] --- SWQ1--->[PIPELINE 2 core=2] -----SWQ2---->
>>> [PIPELINE 3 core=3]
>>>
>>> Case 2:
>>> [PIPELINE 0 MASTER core =0]
>>> [PIPELINE 1 core=1] --- SWQ1--->[PIPELINE 2 core=1] -----SWQ2---->
>>> [PIPELINE 3 core=1]
>>>
>>> I send a ping between two hosts connected at both sides of the pipeline
>>> model which allows these pings to cross all the pipelines (from 1 to 3).
>>> What I observe in Case 1 (each pipeline has its own thread in different
>>> core) is that the reported RTT is less than 1 ms, whereas in Case 2 (all
>>> pipelines except MASTER are run in the same thread) is 20 ms.
>>> Furthermore,
>>> in Case 2, if I increase a lot (hundreds of Mbps) the packet rate this
>>> RTT
>>> decreases to 3 or 4 ms.
>>>
>>> Has somebody observed this behaviour in the past? Can it be solved
>>> somehow?
>>>
>>> Thanks a lot for your attention
>>> --
>>> Victor
>>>
>>>
>>> --
>>> Victor
>>>
>>