Hey, My current (unfinished) progress on this is now available here: https://github.com/thebracket/cpumap-pping-hackjob I mean it about the warnings, this isn't at all stable, debugged - and can't promise that it won't unleash the nasal demons (to use a popular C++ phrase). The name is descriptive! ;-) With that said, I'm pretty happy so far: * It runs only on the classifier - which xdp-cpumap-tc has nicely shunted onto a dedicated CPU. It has to run on both the inbound and outbound classifiers, since otherwise it would only see half the conversation. * It does assume that your ingress and egress CPUs are mapped to the same interface; I do that anyway in BracketQoS. Not doing that opens up a potential world of pain, since writes to the shared maps would require a locking scheme. Too much locking, and you lose all of the benefit of using multiple CPUs to begin with. * It is pretty wasteful of RAM, but most of the shaper systems I've worked with have lots of it. * I've been gradually removing features that I don't want for BracketQoS. A hypothetical future "useful to everyone" version wouldn't do that. * Rate limiting is working, but I removed the requirement for a shared configuration provided from userland - so right now it's always set to report at 1 second intervals per stream. My testbed is currently 3 Hyper-V VMs - a simple "client" and "world", and a "shaper" VM in between running a slightly hacked-up LibreQoS. iperf from "client" to "world" (with Libre set to allow 10gbit/s max, via a cake/HTB queue setup) is around 5 gbit/s at present, on my test PC (the host is a core i7, 12th gen, 12 cores - 64gb RAM and fast SSDs) Output currently consists of debug messages reading: cpumap/0/map:4-1371 [000] D..2. 515.399222: bpf_trace_printk: (tc) Flow open event cpumap/0/map:4-1371 [000] D..2. 515.399239: bpf_trace_printk: (tc) Send performance event (5,1), 374696 cpumap/0/map:4-1371 [000] D..2. 515.399466: bpf_trace_printk: (tc) Flow open event cpumap/0/map:4-1371 [000] D..2. 515.399475: bpf_trace_printk: (tc) Send performance event (5,1), 247069 cpumap/0/map:4-1371 [000] D..2. 516.405151: bpf_trace_printk: (tc) Send performance event (5,1), 5217155 cpumap/0/map:4-1371 [000] D..2. 517.405248: bpf_trace_printk: (tc) Send performance event (5,1), 4515394 cpumap/0/map:4-1371 [000] D..2. 518.406117: bpf_trace_printk: (tc) Send performance event (5,1), 4481289 cpumap/0/map:4-1371 [000] D..2. 519.406255: bpf_trace_printk: (tc) Send performance event (5,1), 4255268 cpumap/0/map:4-1371 [000] D..2. 520.407864: bpf_trace_printk: (tc) Send performance event (5,1), 5249493 cpumap/0/map:4-1371 [000] D..2. 521.406664: bpf_trace_printk: (tc) Send performance event (5,1), 3795993 cpumap/0/map:4-1371 [000] D..2. 522.407469: bpf_trace_printk: (tc) Send performance event (5,1), 3949519 cpumap/0/map:4-1371 [000] D..2. 523.408126: bpf_trace_printk: (tc) Send performance event (5,1), 4365335 cpumap/0/map:4-1371 [000] D..2. 524.408929: bpf_trace_printk: (tc) Send performance event (5,1), 4154910 cpumap/0/map:4-1371 [000] D..2. 525.410048: bpf_trace_printk: (tc) Send performance event (5,1), 4405582 cpumap/0/map:4-1371 [000] D..2. 525.434080: bpf_trace_printk: (tc) Send flow event cpumap/0/map:4-1371 [000] D..2. 525.482714: bpf_trace_printk: (tc) Send flow event The times haven't been tweaked yet. The (5,1) is tc handle major/minor, allocated by the xdp-cpumap parent. I get pretty low latency between VMs; I'll set up a test with some real-world data very soon. I plan to keep hacking away, but feel free to take a peek. Thanks, Herbert On Mon, Oct 17, 2022 at 10:14 AM Simon Sundberg wrote: > Hi, thanks for adding me to the conversation. Just a couple of quick > notes. > > On Mon, 2022-10-17 at 16:13 +0200, Toke Høiland-Jørgensen wrote: > > [ Adding Simon to Cc ] > > > > Herbert Wolverson via LibreQoS writes: > > > > > Hey, > > > > > > I've had some pretty good success with merging xdp-pping ( > > > https://github.com/xdp-project/bpf-examples/blob/master/pping/pping.h > ) > > > into xdp-cpumap-tc ( https://github.com/xdp-project/xdp-cpumap-tc ). > > > > > > I ported over most of the xdp-pping code, and then changed the entry > point > > > and packet parsing code to make use of the work already done in > > > xdp-cpumap-tc (it's already parsed a big chunk of the packet, no need > to do > > > it twice). Then I switched the maps to per-cpu maps, and had to pin > them - > > > otherwise the two tc instances don't properly share data. > > > > > I guess the xdp-cpumap-tc ensures that the same flow is processed on > the same CPU core at both ingress or egress. Otherwise, if a flow may > be processed by different cores on ingress and egress the per-CPU maps > will not really work reliably as each core will have a different view > on the state of the flow, if there's been a previous packet with a > certain TSval from that flow etc. > > Furthermore, if a flow is always processed on the same core (on both > ingress and egress) I think per-CPU maps may be a bit wasteful on > memory. From my understanding the keys for per-CPU maps are still > shared across all CPUs, it's just that each CPU gets its own value. So > all CPUs will then have their own data for each flow, but it's only the > CPU processing the flow that will have any relevant data for the flow > while the remaining CPUs will just have an empty state for that flow. > Under the same assumption that packets within the same flow are always > processed on the same core there should generally not be any > concurrency issues with having a global (non-per-CPU) either as packets > from the same flow cannot be processed concurrently then (and thus no > concurrent access to the same value in the map). I am however still > very unclear on if there's any considerable performance impact between > global and per-CPU map versions if the same key is not accessed > concurrently. > > > > Right now, output > > > is just stubbed - I've still got to port the perfmap output code. > Instead, > > > I'm dumping a bunch of extra data to the kernel debug pipe, so I can > see > > > roughly what the output would look like. > > > > > > With debug enabled and just logging I'm now getting about 4.9 > Gbits/sec on > > > single-stream iperf between two VMs (with a shaper VM in the middle). > :-) > > > > Just FYI, that "just logging" is probably the biggest source of > > overhead, then. What Simon found was that sending the data from kernel > > to userspace is one of the most expensive bits of epping, at least when > > the number of data points goes up (which is does as additional flows are > > added). > > Yhea, reporting individual RTTs when there's lots of them (you may get > upwards of 1000 RTTs/s per flow) is not only problematic in terms of > direct overhead from the tool itself, but also becomes demanding for > whatever you use all those RTT samples for (i.e. need to log, parse, > analyze etc. a very large amount of RTTs). One way to deal with that is > of course to just apply some sort of sampling (the -r/--rate-limit and > -R/--rtt-rate > > > > > So my question: how would you prefer to receive this data? I'll have to > > > write a daemon that provides userspace control (periodic cleanup as > well as > > > reading the performance stream), so the world's kinda our oyster. I can > > > stick to Kathie's original format (and dump it to a named pipe, > perhaps?), > > > a condensed format that only shows what you want to use, an efficient > > > binary format if you feel like parsing that... > > > > It would be great if we could combine efforts a bit here so we don't > > fork the codebase more than we have to. I.e., if "upstream" epping and > > whatever daemon you end up writing can agree on data format etc that > > would be fantastic! Added Simon to Cc to facilitate this :) > > > > Briefly what I've discussed before with Simon was to have the ability to > > aggregate the metrics in the kernel (WiP PR [0]) and have a userspace > > utility periodically pull them out. What we discussed was doing this > > using an LPM map (which is not in that PR yet). The idea would be that > > userspace would populate the LPM map with the keys (prefixes) they > > wanted statistics for (in LibreQOS context that could be one key per > > customer, for instance). Epping would then do a map lookup into the LPM, > > and if it gets a match it would update the statistics in that map entry > > (keeping a histogram of latency values seen, basically). Simon's PR > > below uses this technique where userspace will "reset" the histogram > > every time it loads it by swapping out two different map entries when it > > does a read; this allows you to control the sampling rate from > > userspace, and you'll just get the data since the last time you polled. > > Thank's Toke for summarzing both the current state and the plan going > forward. I will just note that this PR (and all my other work with > ePPing/BPF-PPing/XDP-PPing/I-suck-at-names-PPing) will be more or less > on hold for a couple of weeks right now as I'm trying to finish up a > paper. > > > I was thinking that if we all can agree on the map format, then your > > polling daemon could be one userspace "client" for that, and the epping > > binary itself could be another; but we could keep compatibility between > > the two, so we don't duplicate effort. > > > > Similarly, refactoring of the epping code itself so it can be plugged > > into the cpumap-tc code would be a good goal... > > Should probably do that...at some point. In general I think it's a bit > of an interesting problem to think about how to chain multiple XDP/tc > programs together in an efficent way. Most XDP and tc programs will do > some amount of packet parsing and when you have many chained programs > parsing the same packets this obviously becomes a bit wasteful. In the > same time it would be nice if one didn't need to manually merge > multiple programs together into a single one like this to get rid of > this duplicated parsing, or at least make that process of merging those > programs as simple as possible. > > > > -Toke > > > > [0] https://github.com/xdp-project/bpf-examples/pull/59 > > När du skickar e-post till Karlstads universitet behandlar vi dina > personuppgifter. > When you send an e-mail to Karlstad University, we will process your > personal data. >