Hi Neal, On Thu, 2019-12-12 at 10:11 -0500, Neal Cardwell wrote: > On Thu, Dec 12, 2019 at 9:50 AM Johannes Berg <johannes@xxxxxxxxxxxxxxxx> wrote: > > If you have any thoughts on this, I'd appreciate it. > > Thanks for the detailed report! Well, it wasn't. For example, I neglected to mention that I have to actually use at least 2 TCP streams (but have tried up to 20) in order to not run into the gbit link limit on the AP :-) > I was curious: > > o What's the sender's qdisc configuration? There's none, mac80211 bypasses qdiscs in favour of its internal TXQs with FQ/codel. > o Would you be able to log periodic dumps (e.g. every 50ms or 100ms) > of the test connection using a recent "ss" binary and "ss -tinm", to > hopefully get a sense of buffer parameters, and whether the flow in > these cases is being cwnd-limited, pacing-limited, > send-buffer-limited, or receive-window-limited? Sure, though I'm not sure my ss is recent enough for what you had in mind - if not I'll have to rebuild it (it was iproute2-ss190708). https://p.sipsolutions.net/3e515625bf13fa69.txt Note there are 4 connections (iperf is being used) but two are control and two are data. Easy to see the difference really :-) > o Would you be able to share a headers-only tcpdump pcap trace? I'm not sure how to do headers-only, but I guess -s100 will work. https://johannes.sipsolutions.net/files/he-tcp.pcap.xz Note that this is from a different run than the ss stats. johannes
