On Sun, Aug 26, 2018 at 2:09 PM Dave Taht <[email protected]> wrote: > > On Sun, Aug 26, 2018 at 1:58 PM Rosen Penev <[email protected]> wrote: > > > > On Sun, Aug 26, 2018 at 11:44 AM Mikael Abrahamsson <[email protected]> > > wrote: > > > > > > On Sat, 25 Aug 2018, Dave Taht wrote: > > > > > > > The expressobin is a Marvell Armada "3700LP (88F3720) dual core ARM > > > > Cortex A53 processor up to 1.2GHz" - how does that compare? I have > > > > plenty of ath10k and ath9k pcmcia cards.... > > > > > > I have one of these, incl wifi. Right now the drivers are not in great > > > shape, but they're being worked on. My espressobin has worse performance > > > than on its wired ports than my WRT1200AC (Armada 385). > > If as you mentioned earlier that ethernet performance is limited by > > interrupts, then this commit is kind of depressing: > > > > https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/drivers/net/ethernet/marvell/mvneta.c?h=next-20180824&id=0f5c6c30a0f8c629b92ecdaef61b315c43fde10a > > I was on that thread. It was broken before entirely. As for the single > interrupt on this chip variant - believe it or not, I'm not huge on > lots of different interrupts for everything. I'd like it if we had > more than an rx or tx interrupt > in general, I'd love it if we had a programmable "tx is almost done" > interrupt that you could tune to the > interrupt latency... and it's complicated and costs wires to have lots > of different interrupt types... and (fantasizing again) I'd love it if > we had a scratchpad or dedicated memory to store interrupt handlers in > rather than relying on cache.... > > I'd looked deeply into improving this driver once upon a time, and > wanted to rip the software gro out of it, > in particular, and not defer things as much, trying things like NAPI > of 16 and measuring where time was spent. The copy to memory is > expensive, and then it defers further work. > > Less code, particularly near interrupt time, is better than a lot. > adding XMIT_MORE to the ar71xx driver (which hurt it badly) is one > example. I've been looking a lot at ag71xx. The driver has so much low hanging fruit. Unfortunately I lack the knowledge to fix most of it.
This patch for example gives me a ~20-30mbps improvement in iperf tests: https://pastebin.com/ZExWjXQZ It's kind of unfortunate given how much atheros hardware is out there. > > Given something *cool* now landing ( skb list batching, see lwn ) it > would be worthwhile to revisit this. I don't care if I get more > interrupts/sec (particularly on a multicore) if we could drain the rx > ring over smaller intervals... > > but that's me, I'm all about the latency. :) Nobody's willing to rip > the latency out of stuff, they'd rather add features. It's really hard > to correctly measure interrupt latency regardless. > > > > > > > > I have talked to people who say the drivers are being worked on though... > > > If you have input, Kaloz is probably a great person to take that input. I > > > know other people working on Marvell drivers as well. > > > > > > -- > > > Mikael Abrahamsson email: [email protected] > > > _______________________________________________ > > > Bloat mailing list > > > [email protected] > > > https://lists.bufferbloat.net/listinfo/bloat > > > > -- > > Dave Täht > CEO, TekLibre, LLC > http://www.teklibre.com > Tel: 1-669-226-2619 _______________________________________________ Bloat mailing list [email protected] https://lists.bufferbloat.net/listinfo/bloat
