On Fri, Aug 24, 2018 at 10:13 AM Pete Heist <p...@heistp.net> wrote: > > > On Aug 23, 2018, at 10:26 AM, Pete Heist <p...@heistp.net> wrote: > > On Aug 23, 2018, at 2:49 AM, Dave Taht <dave.t...@gmail.com> wrote: > > I had a chance to give a talk at broadcom recently, slides here: > > http://flent-fremont.bufferbloat.net/~d/broadcom_aug9.pdf > > > Thanks for sharing, this is really useful, raising awareness where it > matters. Quite a bit of content... :) > > Ubiquiti needs some work getting this into more of their products (EdgeMAX in > particular). A good time to lobby for this might be, well a couple months > ago, as they’re producing alpha builds for their upcoming 2.0 release with > kernel 4.9 and new Cavium/Mediatek/Octeon SDKs. I just asked about the status > in the EdgeRouter Beta forum, in case it finds the right eyes before the > release: > > https://community.ubnt.com/t5/EdgeRouter-Beta/BQL-support/m-p/2466657 > > > This started a discussion, and no, so far it looks like there’s no BQL > support in the upcoming 2.0 release. > > For my own benefit, re-reading the original patch series comment > (https://lwn.net/Articles/469652/) makes it sound like BQL is useful even > without AQM (original benchmarks were done with straight pfifo_fast). I > didn’t realize this, actually. If anything incorrect about BQL was said in > this discussion, correct us, please… :)
yes, bql is very useful even with pfifo fast. without BQL I doubt the internet would be scaling as it is today in the dc, or on the smaller hosts and devices that support it. It's in the mvneta, it's in the ar71xx, with documented results there that I could dig up. (tho: things like tsq are helping and mask the problem on simple tests) The experiment I documented on the slides that kicked off this thread and the other experiment on the systemd bug, easily show the benefit on hosts forwarding packets (be they from local applications, coming from various sources like docker containers, etc), and anyone can show what goes wrong if you disable BQL nowadays, basically restoring linux-3.3 behavior, with a very simple test: For I in /sys/class/net/your_device/queues/tx*/byte_queue_limits/limit_min do echo 10000000 > $I done so long as you run enough kinds of flows that don't engage TSQ. However, in the edgerouter w/offloads case all that part of the stack has been short circuited into the offload engine. I don't know how much buffering is in there on the new firmware, I'd done a few tests on it in the old days, showing it to be around 10ms at gigE but even that memory is kind of vague (the easy test here is slam two ports into one), and for all I know the new firmware is worse, without going back to track this new release. (I do have a few edgerouters but they are all in production) There was also a paper on BQL a few years back that I can dig up.... > Pete > -- Dave Täht CEO, TekLibre, LLC http://www.teklibre.com Tel: 1-669-226-2619 _______________________________________________ Cerowrt-devel mailing list Cerowrt-devel@lists.bufferbloat.net https://lists.bufferbloat.net/listinfo/cerowrt-devel