27/04/2021 11:57, Ananyev, Konstantin: > From: Yigit, Ferruh <ferruh.yi...@intel.com> > > On 4/26/2021 9:46 PM, Honnappa Nagarahalli wrote: > > >>>>>>>>>>>> On Thu, Mar 11, 2021 at 12:01 AM Honnappa > > >>>>>>>>>>>> Nagarahalli <honnappa.nagaraha...@arm.com> wrote: > > >>>>>>>>>>>>> > > >>>>>>>>>>>>> Hello, > > >>>>>>>>>>>>> Performance of L3fwd example application > > >>>>>>>>>>>>> is one of the key > > >>>>>>>>>>>> benchmarks in DPDK. However, the application does > > >>>>>>>>>>>> not have many debugging statistics to understand the > > >>>>>>>>>>>> performance issues. We have added L3fwd as another > > >>>>>>>>>>>> mode/stream to testpmd which provides > > >>>>>>>>>> enough > > >>>>>>>>>>>> statistics at various levels. This has allowed us to > > >>>>>>>>>>>> debug the performance issues effectively. > > >>>>>>>>>>>>> > > >>>>>>>>>>>>> There is more work to be done to get it to > > >>>>>>>>>>>>> upstreamable state. I am > > >>>>>>>>>>>> wondering if such a patch is helpful for others and > > >>>>>>>>>>>> if the community would be interested in taking a > > >>>>>>>>>>>> look. Please let me know > > >>>>>>>>> what you think. > > >>>>>>>>>>>> > > >>>>>>>>>>>> We are using app/proc-info/ to attach and analyze > > >>>>>>>>>>>> the > > >>>>> performance. > > >>>>>>>>>>>> That helps to analyze the unmodified application. I > > >>>>>>>>>>>> think, if something is missing in proc-info app, in > > >>>>>>>>>>>> my opinion it is better to enhance proc-info so that > > >>>>>>>>>>>> it can help other third-party > > >>>>>>> applications. > > >>>>>>>>>>>> > > >>>>>>>>>>>> Just my 2c. > > >>>>>>>>>>> Thanks Jerin. We will explore that. > > >>>>>>>>>> > > >>>>>>>>>> I agree it is dangerous to rely too much on testpmd for > > >> everything. > > >>>>>>>>>> Please tell us what in testpmd could be useful out of it. > > >>>>>>>>>> > > >>>>>>>>> Things that are very helpful in testpmd are: 1) HW > > >>>>>>>>> statistics from the NIC 2) Forwarding stats 3) Burst stats > > >>>>>>>>> (indication of headroom > > >>>>>>>>> availability) 4) Easy to set parameters like RX and TX > > >>>>>>>>> queue depths (among others) without having to recompile. > > >>>>>>>> > > >>>>>>>> [Kathleen Capella] > > >>>>>>>> Thank you for the suggestion of app/proc-info. I've tried it > > >>>>>>>> out with l3fwd and see that it does have the HW stats from > > >>>>>>>> the NIC and the forwarding > > >>>>>>> stats. > > >>>>>>>> However, it does not have the burst stats testpmd offers, > > >>>>>>>> nor the > > >>>>>>> > > >>>>>>> One option to see such level of debugging would be to have > > >>>>>>> - Create a memzone in the primary process > > >>>>>>> - Application under test can update the stats in memzone based > > >>>>>>> on the code flow > > >>>>>>> - proc-info can read the counters updated by application under > > >>>>>>> test using the memzone object got through > > >> rte_memzone_lookup() > > >>>>>> Agreed. Currently, using app/proc-info does not provide this > > >>>>>> ability. We > > >>>>> cannot add this capability to app/proc-info as these stats would > > >>>>> be specific to L3fwd application. > > >>>>> > > >>>>> I meant creating generic counter-read/write infra via memzone to > > >>>>> not make it as l3fwd specific. > > >>>> Currently, app/proc-info is able to print the stats as they are > > >>>> standardized > > >> via the API. But for statistics that are generated in the application, > > >> they are > > >> very specific to that application. For ex: burst stats in testpmd are > > >> very > > >> specific to it and another application might implement the same in a very > > >> different manner. > > >>>> > > >>>> In needs to be something like the app/proc-info just needs to be a dumb > > >> displaying utility and the application has to do all the heavy lifting > > >> of copying > > >> the exact display strings to the memory. > > >>> > > >>> Yes. > > >>> > > >>>> > > >>>>>>> > > >>>>>>> Another approach will be using rte_trace()[1] for > > >>>>>>> debugging/tracing by adding tracepoints in l3fwd for such events. > > >>>>>>> It has a timestamp and the trace format is opensource trace > > >>>>>>> format(CTF(Common trace format)), so that we can use post > > >>>>>>> posting tools to analyze. > > >>>>>>> [1] > > >>>>>>> https://doc.dpdk.org/guides/prog_guide/trace_lib.html > > >>>>>> This is good for analyzing an incident. I think it is an > > >>>>>> overhead for > > >>>>> development purposes. > > >>>>> > > >>>>> Consider if one wants to add burst stats, one can add stats > > >>>>> increment under RTE_TRACE_POINT_FP, it will be emitted whenever > > >>>>> code flow through that path. Set of events of can be viewed in > > >>>>> trace viewer[1]. Would that be enough? > > >>>>> Adding traces to l3fwd can be upstreamed as it is useful for > > >>>>> others for debugging. > > >>>>> > > >>>>> [1] > > >>>>> https://github.com/jerinjacobk/share/blob/master/dpdk_trace.JPG > > >>>> This needs post processing of the trace info to derive the > > >>>> information, is it > > >> correct? For ex: for burst stats, there will be several traces generated > > >> collecting the number of packets returned by rte_eth_rx_burst which needs > > >> to be post processed. > > >>> > > >>> Or You can have an additional variable to acculate it. > > >>> > > >>>> Also, adding traces is equivalent to adding statistics in L3fwd. > > >>> > > >>> Yes. > > >>> > > >>> If the sole purpose only stats then it is better to add status in > > >>> l3fwd without performance impact. I thought some thing else. > > >>> > > >>>> > > >>>>>>> > > >>>>>>>> ability to easily change parameters without having to > > >>>>>>>> recompile, which helps reduce debugging time significantly. > > >>>> We will not be able to fix this above issue. > > >>> > > >>> It depends on what you want to debug. Trace can be disabled at runtime. > > >> > > >> > > >> DPDK has existing API's for application metrics but they are rarely used. > > >> > > >> Why not implement rte_metrics in l3fwd and proc-info? > > > This discussion has ended up as a stats discussion. But, we also need to > > > be able to change the configurable parameters easily. > > > If we implement the stats and ability to change the configurable > > > parameters, then it is essentially bringing in some of the capabilities > > > from > > testpmd to the sample application. I think that will result in lot more > > code in the sample application and will make it complicated. > > > > > > Instead our proposal is to take L3fwd to testpmd and use all the infra > > > code that testpmd provides. We see that this approach results in less > > amount of code added to DPDK overall. > > > > > > > Agree that it may help testing to have l3fwd support on the testpmd. > > > > Two concerns, > > 1) Testpmd already too complex. > > 2) Code duplication. > > > > For 1), if the l3fwd can be implemented in testpmd as new, independent > > forwarding mode, without touching rest of the testpmd, I think it can be OK. > > In fact, l3fwd is also quite big and complex: > $ wc -l examples/l3fwd/*.[h,c] |grep total > 6969 total > > Plus it will introduce extra dependencies (fib, lpm, hash, might-be acl?) > I am not sure it is a good idea to pull all these complexities into test-pmd. > I can't imagine that l3fwd app need ability to configure each and every > PMD parameter. > From my experience in l3fwd most of cycles are spent not in PMD itself, > but in actual packet processing: header parsing and checking, classification, > routing table lookup, etc.
testpmd goal is to test the driver, not the libraries. > > Not sure how to address 2), also lets say we want to add new feature to > > l3fwd, > > where it should go, to the sample or to the testpmd? l3fwd is not targetted for testing. Maybe we just lack a new test application for routing libraries?
