On Mon, Jun 1, 2015 at 10:06 AM, jsullivan@xxxxxxxxxxxxxxxxxxx <jsullivan@xxxxxxxxxxxxxxxxxxx> wrote: > >> On June 1, 2015 at 12:36 PM Andy Furniss <adf.lists@xxxxxxxxx> wrote: >> >> >> Robert LeBlanc wrote: >> > -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 >> > >> > Any ideas on this? >> >> 40 gig nics are way beyond anything I've ever done with tc and I guess >> involve some offload = huge "packets". >> >> It could be that aas sfq has a default qlen of 128 and as you are not >> actually rate limiting (and to do that may be "interesting" at 80 gig) >> the prio relies on some downstream buffer being full. Perhaps it's just >> that at these rates prio can not dequeue anything for periods of time so >> the 128 limit of sfq is overrun even for the highest prio. >> >> This is pure guesswork. >> -- >> 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 > > Alas, I haven't yet read the details of the original post but I know we just > replaced all our sfq leaves with fq_codel because of concerns about the per flow > packet depth on high speed, high latency networks. Yes, older versions of SFQ had a hard limit on queue depth. This was "improved" in linux 3.6 and later but that work ultimately pointed at a need to actively manage the queue depth, which begat sfqred, and ultimately fq_codel. I note that, these days, the best results we get for tcp-heavy-*servers and hosts* (not routers, not udp heavy services, and the bare metal under a vm is a "router" in this context), in the data center, at these speeds, now come from sch_fq (from the pacing, fq, and tso fixes), and a low setting for tcp_limit_output_bytes. example: https://fasterdata.es.net/host-tuning/linux/fair-queuing-scheduler/ fq_codel remains a great all-around choice, but what pacing is doing is really remarkable for servers in sch_fq. > -- > 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 What will it take to vastly improve wifi for everyone? https://plus.google.com/u/0/explore/makewififast -- 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
