On Tue, Jul 12, 2016 at 2:28 PM, Toke Høiland-Jørgensen <toke@xxxxxxx> wrote: > Felix Fietkau <nbd@xxxxxxxx> writes: > >> Hi, >> >> With Toke's ath9k txq patch I've noticed a pretty nasty performance >> regression when running local iperf on an AP (running the txq stuff) to >> a wireless client. >> >> Here's some things that I found: >> - when I use only one TCP stream I get around 90-110 Mbit/s >> - when running multiple TCP streams, I get only 35-40 Mbit/s total >> - fairness between TCP streams looks completely fine >> - there's no big queue buildup, the code never actually drops any packets >> - if I put a hack in the fq code to force the hash to a constant value >> (effectively disabling fq without disabling codel), the problem >> disappears and even multiple streams get proper performance. >> >> Please let me know if you have any ideas. > > Hmm, I see two TCP streams get about the same aggregate throughput as > one, both when started from the AP and when started one hop away. > However, do see TCP flows take a while to ramp up when started from the > AP - a short test gets ~70Mbps when run from one hop away and ~50Mbps > when run from the AP. how long are you running the tests for? > > (I seem to recall the ramp-up issue to be there pre-patch as well, > though). The original ath10k code had a "swag" at hooking in an estimator from rate control. With minstrel in play that can be done better in the ath9k. > As for why this would happen... There could be a bug in the dequeue code > somewhere, but since you get better performance from sticking everything > into one queue, my best guess would be that the client is choking on the > interleaved packets? I.e. expending more CPU when it can't stick > subsequent packets into the same TCP flow? I share this concern. The quantum is? I am not opposed to a larger quantum (2 full size packets = 3028 in this case?). > -Toke > -- > To unsubscribe from this list: send the line "unsubscribe linux-wireless" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- Dave Täht Let's go make home routers and wifi faster! With better software! http://blog.cerowrt.org -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
