help troubleshooting low throughput

[Tim Harvey]

On Thu, May 22, 2014 at 2:39 AM, Tim Harvey <tharvey at gateworks.com> wrote:
> Greetings,
>
> I could use some help troubleshooting a low throughput issue. I'm
> currently using the following:
>  - UNEX DAXA-O1 11ac/n/a 3x3 MIMO qca988x hw2.0
> http://www.unex.com.tw/product/daxa-o1
>  - 80MHz channel w/o local interference
>  - ath10k git 0dbbb028a7c461777bf4a0d53780e539e6f40e14 (May 16)
>  - up-to-date git of hostapd/wpa_supplicant/iw
>  - fw 10.1.467.2-1 api 2 htt 2.1
>  - infrastructure mode using
> http://wireless.kernel.org/en/users/Drivers/ath10k/configuration#Full_hostapd_configuration
>
> I'm using iperf for throughput tests and getting no more than 220mbps
> best case, typically more like 120mbps. The rx bitrate bounces around
> MCS 5 to 8 and shows 3 spatial streams so I would be expecting a much
> higher throughput. The cards are in boards with a quad-core ARM 1GHz
> Cortex-A9 CPU and there is no indication the system is bottle-necked.
> There are no other kernel modules loaded other thank
> ath10k_pci/ath10k_core/ath and debugging is disabled.
>
> Using tcpdump/wireshark to inspect the radiotap headers I only see
> packets with 'Antenna: 0' - Does this field indicate what transmitter
> the pkt was received on and indicate I'm only receiving from a single
> transmitter?
>
> I've noticed 'iw phy0 info' shows 'Available Antennas: TX 0 RX 0' and
> any attempt to set the antenna mask with 'iw phy set antenna' fails
> with an 'Operation not supported (-95)' - does this indicate an issue
> with ath10k, iw, or perhaps the card's EEPROM?
>
> I've also noticed that 'iw wlan0 station dump' statistics show in the
> rx bitrate stat that sometimes SGI is flagged and sometimes its not -
> should I expect this to change like this? I was under the impression
> that was a static configuration.
>
> Thanks,
>
> Tim

I neglected to mention that on whichever end is running the iperf
server (receiving) I do see periodic 'failed to pop...' warnings, a
pair of them a couple times a minute. I'm not quite clear if this is a
hardware issue or something else:

[ 3763.131280] ath10k: failed to pop amsdu from htt rx ring -22
[ 3769.081093] ath10k: failed to pop chained msdus, dropping
[ 3769.086575] ath10k: failed to pop amsdu from htt rx ring -22
[ 3781.092383] ath10k: failed to pop chained msdus, dropping
[ 3781.097869] ath10k: failed to pop amsdu from htt rx ring -22
[ 3784.367225] ath10k: failed to pop chained msdus, dropping
[ 3784.372735] ath10k: failed to pop amsdu from htt rx ring -22
[ 3809.501484] ath10k: failed to pop chained msdus, dropping
[ 3809.506993] ath10k: failed to pop amsdu from htt rx ring -22
[ 3821.723404] ath10k: failed to pop chained msdus, dropping
[ 3821.728914] ath10k: failed to pop amsdu from htt rx ring -22
[ 3832.067136] ath10k: failed to pop chained msdus, dropping
[ 3832.072690] ath10k: failed to pop amsdu from htt rx ring -22
[ 3833.632859] ath10k: failed to pop chained msdus, dropping
[ 3833.638341] ath10k: failed to pop amsdu from htt rx ring -22
[ 3837.940414] ath10k: failed to pop chained msdus, dropping
[ 3837.945982] ath10k: failed to pop amsdu from htt rx ring -22
[ 3844.100514] ath10k: failed to pop chained msdus, dropping

Tim