[ath9k-devel] ath9k-issue with stop RX/TX DMA - correlation with WMM traffic classes?

[Felix Fietkau <nbd@openwrt.org>]

On 2013-04-12 10:27 AM, Rougu wrote:
> Hi everyone,
> 
> while I might be totally wrong with my observation, I still would like 
> to share it, because this issue is lingering for years now and many 
> users are waiting to a solid grip on it to fix it.
> 
> I'm running several freifunk-nodes in Cologne, Germany, where the 
> firmware contains a ath9k-watchdog that restarts the node, once the 
> failure occurs. One of my nodes is affected in varying intervals of 200 
> .. 10000 seconds uptime, depending on WLAN activity.
> 
> (openwrt, attitude adjustment, kernel 3.3.8)
Please also run a test with OpenWrt trunk and compare stability.

> Looking at "/sys/kernel/debug/ieee80211/phy0/ath9k/xmit", it seems that
> MPDUs in the highest priority queue "VO" have a lower rate of 
> "completion" (90,5%) than those in "BE" (>99,9%).
> 
>  From my laymen's perspective I would expect "VO" to have an even better 
> completion rate than "BE".
What you're missing in that perspective is the fact that not all traffic
is created equal :)
The VO queue carries management traffic. Probe responses frequently end
up in XRetry because the number of retries is intentionally limited to 1
(some clients are often either too far away to ACK the probe response,
or do not stick around long enough to receive it).

> Any chance to see a correlation between WMM priority queue handling and 
> DMA access problems?
No, the data is too limited for that.

- Felix