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. > > 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. 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 _______________________________________________ Cake mailing list [email protected] https://lists.bufferbloat.net/listinfo/cake
