OK James, Thanks for sharing your own experience. What I would need right now is to know from maintainers if this latency behaviour is something inherent in DPDK in the particular case we are talking about. Furthermore, I would also appreciate it if some maintainer could tell us if there is some workaround or special configuration that completely mitigate this latency. I guess that there is one mitigation mechanism, which is the approach that the new ip_pipeline app example exposes: if two or more pipelines are in the same core the "connection" between them is not a software queue but a "direct table connection".
This proposed approach has a big impact on my application and I would like to know if there is other mitigation approach taking into account the "old" version of ip_pipeline example. Thanks for your attention El mar., 18 feb. 2020 a las 23:09, James Huang (<jamsp...@gmail.com>) escribió: > No. I didn't notice the RTT bouncing symptoms. > In high throughput scenario, if multiple pipelines runs in a single cpu > core, it does increase the latency. > > > Regards, > James Huang > > > On Tue, Feb 18, 2020 at 1:50 AM Victor Huertas <vhuer...@gmail.com> wrote: > >> Dear James, >> >> I have done two different tests with the following configuration: >> [PIPELINE 0 MASTER core =0] >> [PIPELINE 1 core=1] --- SWQ1--->[PIPELINE 2 core=1] -----SWQ2----> >> [PIPELINE 3 core=1] >> >> The first test (sending a single ping to cross all the pipelines to >> measure RTT) has been done by setting the burst_write to 32 in SWQ1 and >> SWQ2. NOTE: All the times we use rte_ring_enqueue_burst in the pipelines 1 >> and 2 we set the number of packets to write to 1. >> >> The result of this first test is as shown subsquently: >> 64 bytes from 192.168.0.101: icmp_seq=343 ttl=63 time=59.8 ms >> 64 bytes from 192.168.0.101: icmp_seq=344 ttl=63 time=59.4 ms >> 64 bytes from 192.168.0.101: icmp_seq=345 ttl=63 time=59.2 ms >> 64 bytes from 192.168.0.101: icmp_seq=346 ttl=63 time=59.0 ms >> 64 bytes from 192.168.0.101: icmp_seq=347 ttl=63 time=59.0 ms >> 64 bytes from 192.168.0.101: icmp_seq=348 ttl=63 time=59.2 ms >> 64 bytes from 192.168.0.101: icmp_seq=349 ttl=63 time=59.3 ms >> 64 bytes from 192.168.0.101: icmp_seq=350 ttl=63 time=59.1 ms >> 64 bytes from 192.168.0.101: icmp_seq=351 ttl=63 time=58.9 ms >> 64 bytes from 192.168.0.101: icmp_seq=352 ttl=63 time=58.5 ms >> 64 bytes from 192.168.0.101: icmp_seq=353 ttl=63 time=58.4 ms >> 64 bytes from 192.168.0.101: icmp_seq=354 ttl=63 time=58.0 ms >> 64 bytes from 192.168.0.101: icmp_seq=355 ttl=63 time=58.4 ms >> 64 bytes from 192.168.0.101: icmp_seq=356 ttl=63 time=57.7 ms >> 64 bytes from 192.168.0.101: icmp_seq=357 ttl=63 time=56.9 ms >> 64 bytes from 192.168.0.101: icmp_seq=358 ttl=63 time=57.2 ms >> 64 bytes from 192.168.0.101: icmp_seq=359 ttl=63 time=57.5 ms >> 64 bytes from 192.168.0.101: icmp_seq=360 ttl=63 time=57.3 ms >> >> As you can see, the RTT is quite high and the range of values is more or >> less stable. >> >> The second test is the same as the first one but setting burst_write to 1 >> for all SWQs. The result is this one: >> >> 64 bytes from 192.168.0.101: icmp_seq=131 ttl=63 time=10.6 ms >> 64 bytes from 192.168.0.101: icmp_seq=132 ttl=63 time=10.6 ms >> 64 bytes from 192.168.0.101: icmp_seq=133 ttl=63 time=10.5 ms >> 64 bytes from 192.168.0.101: icmp_seq=134 ttl=63 time=10.7 ms >> 64 bytes from 192.168.0.101: icmp_seq=135 ttl=63 time=10.8 ms >> 64 bytes from 192.168.0.101: icmp_seq=136 ttl=63 time=10.4 ms >> 64 bytes from 192.168.0.101: icmp_seq=137 ttl=63 time=10.7 ms >> 64 bytes from 192.168.0.101: icmp_seq=138 ttl=63 time=10.5 ms >> 64 bytes from 192.168.0.101: icmp_seq=139 ttl=63 time=10.4 ms >> 64 bytes from 192.168.0.101: icmp_seq=140 ttl=63 time=10.2 ms >> 64 bytes from 192.168.0.101: icmp_seq=141 ttl=63 time=10.4 ms >> 64 bytes from 192.168.0.101: icmp_seq=142 ttl=63 time=10.9 ms >> 64 bytes from 192.168.0.101: icmp_seq=143 ttl=63 time=11.4 ms >> 64 bytes from 192.168.0.101: icmp_seq=144 ttl=63 time=11.3 ms >> 64 bytes from 192.168.0.101: icmp_seq=145 ttl=63 time=11.5 ms >> 64 bytes from 192.168.0.101: icmp_seq=146 ttl=63 time=11.6 ms >> 64 bytes from 192.168.0.101: icmp_seq=147 ttl=63 time=11.0 ms >> 64 bytes from 192.168.0.101: icmp_seq=148 ttl=63 time=11.3 ms >> 64 bytes from 192.168.0.101: icmp_seq=149 ttl=63 time=12.0 ms >> 64 bytes from 192.168.0.101: icmp_seq=150 ttl=63 time=12.6 ms >> 64 bytes from 192.168.0.101: icmp_seq=151 ttl=63 time=12.4 ms >> 64 bytes from 192.168.0.101: icmp_seq=152 ttl=63 time=12.3 ms >> 64 bytes from 192.168.0.101: icmp_seq=153 ttl=63 time=12.8 ms >> 64 bytes from 192.168.0.101: icmp_seq=154 ttl=63 time=12.4 ms >> 64 bytes from 192.168.0.101: icmp_seq=155 ttl=63 time=12.8 ms >> 64 bytes from 192.168.0.101: icmp_seq=156 ttl=63 time=12.7 ms >> 64 bytes from 192.168.0.101: icmp_seq=157 ttl=63 time=12.6 ms >> 64 bytes from 192.168.0.101: icmp_seq=158 ttl=63 time=12.9 ms >> 64 bytes from 192.168.0.101: icmp_seq=159 ttl=63 time=13.4 ms >> 64 bytes from 192.168.0.101: icmp_seq=160 ttl=63 time=13.8 ms >> 64 bytes from 192.168.0.101: icmp_seq=161 ttl=63 time=13.4 ms >> 64 bytes from 192.168.0.101: icmp_seq=162 ttl=63 time=13.3 ms >> 64 bytes from 192.168.0.101: icmp_seq=163 ttl=63 time=13.3 ms >> 64 bytes from 192.168.0.101: icmp_seq=164 ttl=63 time=13.7 ms >> 64 bytes from 192.168.0.101: icmp_seq=165 ttl=63 time=13.7 ms >> 64 bytes from 192.168.0.101: icmp_seq=166 ttl=63 time=13.8 ms >> 64 bytes from 192.168.0.101: icmp_seq=167 ttl=63 time=14.7 ms >> 64 bytes from 192.168.0.101: icmp_seq=168 ttl=63 time=14.7 ms >> 64 bytes from 192.168.0.101: icmp_seq=169 ttl=63 time=14.7 ms >> 64 bytes from 192.168.0.101: icmp_seq=170 ttl=63 time=14.7 ms >> 64 bytes from 192.168.0.101: icmp_seq=171 ttl=63 time=14.6 ms >> 64 bytes from 192.168.0.101: icmp_seq=172 ttl=63 time=14.6 ms >> 64 bytes from 192.168.0.101: icmp_seq=173 ttl=63 time=14.5 ms >> 64 bytes from 192.168.0.101: icmp_seq=174 ttl=63 time=14.5 ms >> 64 bytes from 192.168.0.101: icmp_seq=175 ttl=63 time=15.1 ms >> 64 bytes from 192.168.0.101: icmp_seq=176 ttl=63 time=15.6 ms >> 64 bytes from 192.168.0.101: icmp_seq=177 ttl=63 time=16.0 ms >> 64 bytes from 192.168.0.101: icmp_seq=178 ttl=63 time=16.9 ms >> 64 bytes from 192.168.0.101: icmp_seq=179 ttl=63 time=17.7 ms >> 64 bytes from 192.168.0.101: icmp_seq=180 ttl=63 time=17.6 ms >> 64 bytes from 192.168.0.101: icmp_seq=181 ttl=63 time=17.9 ms >> 64 bytes from 192.168.0.101: icmp_seq=182 ttl=63 time=17.9 ms >> 64 bytes from 192.168.0.101: icmp_seq=183 ttl=63 time=18.5 ms >> 64 bytes from 192.168.0.101: icmp_seq=184 ttl=63 time=18.9 ms >> 64 bytes from 192.168.0.101: icmp_seq=185 ttl=63 time=19.8 ms >> 64 bytes from 192.168.0.101: icmp_seq=186 ttl=63 time=19.8 ms >> 64 bytes from 192.168.0.101: icmp_seq=187 ttl=63 time=10.7 ms >> 64 bytes from 192.168.0.101: icmp_seq=188 ttl=63 time=10.5 ms >> 64 bytes from 192.168.0.101: icmp_seq=189 ttl=63 time=10.4 ms >> 64 bytes from 192.168.0.101: icmp_seq=190 ttl=63 time=10.3 ms >> 64 bytes from 192.168.0.101: icmp_seq=191 ttl=63 time=10.5 ms >> 64 bytes from 192.168.0.101: icmp_seq=192 ttl=63 time=10.7 ms >> As you mentioned, the delay has decreased a lot but it is still >> considerably high (in a normal router this delay is less than 1 ms). >> A second strange behaviour is seen in the evolution of the RTT detected. >> It begins in 10 ms and goes increasing little by litttle to reach a peak of >> 20 ms aprox and then it suddely comes back to 10 ms again to increase again >> till 20 ms. >> >> Is this the behaviour you have in your case when the burst_write is set >> to 1? >> >> Regards, >> >> El mar., 18 feb. 2020 a las 8:18, James Huang (<jamsp...@gmail.com>) >> escribió: >> >>> No. We didn't see noticable throughput difference in our test. >>> >>> On Mon., Feb. 17, 2020, 11:04 p.m. Victor Huertas <vhuer...@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 <jamsp...@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 <vhuer...@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 >>>>>> >>>>> >> >> -- >> Victor >> > -- Victor