The two treatments of quantum are very different. In htb, this is an optimization for lowering the cpu load on switching between classes. In the sqm system I gradually increased this parameter as bandwidth went up to ease the cpu (softirq) load on the system. It helps, but not a lot. In fq_codel this is an optimization to change how much data (in bytes, rather than packets) is served from each flow, per round. If set very low it devolves to being more "packet fair" than "byte fair", and you re-introduce the sorts of problems that SFQ introduced, with needing things like ack prioritization, etc. If set too high you starve downloads on asymmetric networks. So we have evolved to recomending that fq_codel be set to 300 bytes (roughly 4 ipv4 acks), on asymmetric networks running at less than 20mbit/sec (think your typical 22mbit/4mbit cable service or 8mbit/1mbit dsl service). https://tools.ietf.org/id/draft-*-aqm- ...and that it be left at the default, otherwise. Reducing the fq_codel quantum and not doing anything else to the algorithm, allows for far more things than just acks (think, voip, dns, ipv6 acks, quic) to be slightly prioritized over larger packets on asymmetric networks. Otherwise, please leave it alone. For a bit more detail on that there was a thread here recently, and me asking the dd-wrt devs to stop allowing for ack prioritization at all in their qos system when fq_codel is used, and numerous other docs elsewhere. fq_codel is also sensitive to the overall bandwidth on the link. At rates below 2.5mbit, presently, target and interval should be bumped to account for the induced mtu time. On Wed, Dec 17, 2014 at 8:01 AM, Marco Gaiarin <gaio@xxxxxxxxx> wrote: > > A question, probably dumb, but i've no found relevant info out there... > > If i use htb as a classifier (tc class), with parameters 'r2q' that do > some sort of ''quantum automatic computation'', still i need to set > 'quantum' on qdisc, specifically on fq_codel qdisc? > > > Thanks. > > -- > dott. Marco Gaiarin GNUPG Key ID: 240A3D66 > Associazione ``La Nostra Famiglia'' http://www.sv.lnf.it/ > Polo FVG - Via della Bontà, 7 - 33078 - San Vito al Tagliamento (PN) > marco.gaiarin(at)lanostrafamiglia.it t +39-0434-842711 f +39-0434-842797 > > Dona il 5 PER MILLE a LA NOSTRA FAMIGLIA! > http://www.lanostrafamiglia.it/25/index.php/component/k2/item/123 > (cf 00307430132, categoria ONLUS oppure RICERCA SANITARIA) > -- > To unsubscribe from this list: send the line "unsubscribe lartc" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- Dave Täht thttp://www.bufferbloat.net/projects/bloat/wiki/Upcoming_Talks -- To unsubscribe from this list: send the line "unsubscribe lartc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
