Re: compat-wireless and minstrel

Christian Lamparter
2009-11-04T15:53:37Z

On Wednesday 04 November 2009 02:13:49 Adam Wozniak wrote:
> I have two systems under test, both Dell laptops (a Latitude D630 and an
> Inspiron 600m) both running Ubuntu 9.10 with the latest updates, and
> bleeding edge compat-wireless-2009-11-02. I'm using identical AR9170
> based D-Link DWA-160 USB 802.11adapters. I'm using nuttcp to measure
> throughput. I'm running in ad-hoc mode. Both machines have the same
> ar9170 files in /lib/firmware. The machines are sitting about 5 feet
> apart in my office.
>
> I'm having occasional problems where throughput drops through the floor
> (0.5Mbps - 1.5Mbps). When I cat
> /sys/kernel/debug/ieee80211/*/stations/*/rc_stats, one of the machines
> lists the full set of rates, but the other only lists 1M and 54M. After
> a period of time, that machine drops 54M and lists only one rate
> (1Mbps), and the throughput listed by nuttcp drops accordingly. I
> assume that, for whatever reason, the rates drop off the list and
> minstrel uses the only one left available to it.
>
> If I modify include/net/mac80211.h and force the inline function
> rate_supported to always return 1, this fixes the problem. However, I
> think this is a band aid around some other issue.
>
> Any clues or ideas what the real issue might be here?
no, but there are a few knobs you can play with...

First of: more debug data

1. enable some ibss-related verbose messages
open config.mk (in your compat-wireless directory)
and get rid of the leading "# " <-- "sharp + space"
in front of # CONFIG_MAC80211_IBSS_DEBUG=y
(rebuild, reload, retest & checkout dmesg for a _flood_
of potential interesting data)

2. do you think you can get a capture any beacons, auth, assoc, reassoc
management frames form the misbehaving setup?

3. cat /sys/kernel/debug/ieee80211/*/stations/*/rc_stats perhaps?
(yeah, I know... sort of pointless, but people have different believes
and somehow they have the bad tendency to really _stick_ to it!)

Regards,
Chr