On Wed, Jul 25, 2018 at 3:07 AM Sebastian Moeller <[email protected]> wrote: > > Hi Toke, > > > > On Jul 25, 2018, at 12:02, Toke Høiland-Jørgensen <[email protected]> wrote: > > > > Dave Taht <[email protected]> writes: > > > >> I really wanted cake to always optimize for low latency. I wanted it > >> to "just work" at line rate on dsl, on 100mbit, even 10mbit ethernet, > >> to work against pause frames, etc, without configuration. I wanted to > >> defeat drivers like the mvneta that can do 64k of software GRO > >> automagically. > > > > So I think that Eric's point was that the GSO logic itself should > > throttle back and not build so big packets when the link rate is lower. > > Might be worth it to check if this is actually the case, and if not to > > get GSO fixed rather than disabling it.
It doesn't and I think I should just put forth the patch and face the howling from the 40gbit guys. > > > > Also, are there actually any modems that will negotiate ethernet line > > rates less than a gigabit? > > Yes, there are XDSL Modem(routers) that only have fast-ethernet > ports. Not sure how rare these are though. And there are also many devices that ecert hardware flow control. > Best Regards > Sebastian > > > > > >> Along the way to mainlining it, cake's behavior got changed, to scale > >> well to 50Gbit by allowing GSO above a 1gbit shaped rate, and *always > >> allowing GSO at line rate*. > >> > >> if (q->rate_bps && q->rate_bps <= CAKE_SPLIT_GSO_THRESHOLD) > >> q->rate_flags |= CAKE_FLAG_SPLIT_GSO; > >> else > >> q->rate_flags &= ~CAKE_FLAG_SPLIT_GSO; > >> > >> I don't care about 50gbit. I'm delighted, even astonished, it does > >> 50Gbit. I want it to do 1mbit with 13ms interpacket latency when hit > >> by an IW10 burst from somewhere else, not 130, with hardware pause > >> frames in use on the dsl modem or elsewhere. > > > > Getting pause frames to work properly in this setup kinda requires the > > buffering in the modem to be reasonable in the first place... > > > >> so, I'd like to A) default to always split shaped or unshaped. And B) > >> expose the split threshold to be configured via userspace. This latter > >> option would give a tunable for those struggling a bit for cpu to play > >> with, also. > > > > I very much doubt that we can get upstream to accept split as the > > default. It may be possible to get it to be user tunable. I don't think > > we should deviate from upstream unless we absolutely have to (that was > > kinda the whole point of the upstreaming exercise), and I'm not > > convinced that this is a good enough reason... > > > > -Toke > > _______________________________________________ > > Cake mailing list > > [email protected] > > https://lists.bufferbloat.net/listinfo/cake > -- Dave Täht CEO, TekLibre, LLC http://www.teklibre.com Tel: 1-669-226-2619 _______________________________________________ Cake mailing list [email protected] https://lists.bufferbloat.net/listinfo/cake
