[Make-wifi-fast] NanoStation M5 anyone?

[Pete Heist <pete@heistp.net>]

This is an appeal to anyone who has access to a NanoStation M5 and a little time to try to reproduce this problem and add to this post:

https://community.ubnt.com/t5/airMAX-Installation/NanoStation-M5-ping-spikes-about-once-per-second-even-just-to/td-p/2358704

I’ve been trying unsuccessfully to demonstrate to Ubiquiti that they have a bug somewhere that causes isochronous latency spikes. It seems what’s happening is that for a fixed period of time (20ms when one Ethernet port is in use and 40ms when two are in use), once per second, the device queues packets until the pause is over. The function ar7240sw_phy_poll_reset in ag71xx_ar7240.c exactly describes the behavior of 20ms delays when one port is connected and 40ms delays when two ports are connected, so basically it appears that the Ethernet / internal switch device is being reset once per second for some reason.

So far nobody has seemed to care (after all, who’s counting 40ms here or there when it comes to WiFi?), but it does pollute my test results and may be causing latency spikes wherever these devices are deployed (like, worldwide). So if anyone else tests this and can add some weight to the discussion, I’d be glad. :)

Pete