<snip> > > > > > > > > > > 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. Stats as well as ability to change the configuration parameters without having to recompile.
> > > > > > > > > > > > > > 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. We need to be able to identify the best configurations for various parameters like RX/TX queue depths, burst size etc
