I'll see if I can do some monitoring on the USB port. One thing I noticed: If pinging from just the AP to the client device, the latency is high. But as soon as pings are made from the client device to the AP, the latency drops.
In case this is a kernel configuration issue, can someone point me to an ARM kernel config they've used successfully with the ath9k_htc? On Thu, May 29, 2014 at 9:21 PM, Oleksij Rempel <li...@rempel-privat.de> wrote: > Am 28.05.2014 07:36, schrieb Aaron Hamilton: > > If one device has 7ms pings while the other consistently has 200 to > > 1500ms pings, then wouldn't this rule out an interrupt issue? I'd assume > > if the latency was caused by delays in interrupt processing, that both > > devices would have similar latency problems? > > > > The only difference I can see between the PC (no latency) and the > > embedded device (high latency) is that the PC is also sending other > > traffic over the interface while the embedded device is simply > > responding to pings. If it helps, this is a station dump for the two > > devices: > > > > Station 10:0b:a9:a5:46:e4 (on wlan0) <--- low latency PC > > inactive time:35 ms > > rx bytes:345250 > > rx packets:2488 > > tx bytes:4568941 > > tx packets:3258 > > tx retries:0 > > tx failed:0 > > signal: -55 dBm > > signal avg:-54 dBm > > tx bitrate:2.0 MBit/s > > Station 00:22:52:02:20:b1 (on wlan0) <--- high latency embedded device > > inactive time:20136 ms > > rx bytes:40968 > > rx packets:364 > > tx bytes:18713 > > tx packets:127 > > tx retries:0 > > tx failed:0 > > signal: -52 dBm > > signal avg:-52 dBm > > tx bitrate:2.0 MBit/s > > > > I've also attached packet captures using tcpdump on the AP. > > IP level capture is not interesting. More interesting is radio level > capture - should be made in monitore mode with radiotap enabled. And > probably more important usb traffic capture - usbmonitore module should > be enabled. > > > On Mon, May 12, 2014 at 7:47 AM, Oleksij Rempel <li...@rempel-privat.de > > <mailto:li...@rempel-privat.de>> wrote: > > > > Am 12.05.2014 15:11, schrieb Peter Stuge: > > > Oleksij Rempel wrote: > > >> From dmesg i see that, to one USB 1.1 root-hub attached two > device, > > >> ath9k_htc and GobiNet. GobiNet was recognised as eth1 + 3 x > ttyUSB. > > >> IMO, it is a lot for one USB 1.1. > > > > > > True as that may be, if there is a bandwidth requirement for the > > > interface to function correctly and the USB protocol being used > does > > > not guarantee that bandwidth (only control+interrupt transfers > could > > > do it in a meaningful way, and they are rather low bandwidth) then > > > the USB stack would have to allow the driver to reserve bus time, > and > > > the driver would have to make a reservation to successfully handle > > > worst-case load. > > > > > > That's not neccessarily a small change. :\ > > > > I tested ath9k-htc on many different usb host controllers (not usb > 1.1), > > and noticed that most USB 2.0 controllers need some *msecs* to > transfer > > one Interrupt package to the adapter or at least to get ACK signal. > USB > > 3.0 was transferring same package in some *usecs*. The results > should be > > similar for both controller, but it is not the case. Even different > USB > > 2.0 controller was performing differently. > > > > This big difference is responsible for extremely long scan time on > > ath9k_htc on USB 2.0. Since Interrupt Endpoints are heavily used on > this > > devices, reducing bandwidth and/or increasing transfer time for > > Interrupt traffic will be critical. > > > > Best indicator for this issue would be, disabling LED subsystem to > get > > better stability. What, according to Aaron, is the case. > > > > -- > > Regards, > > Oleksij > > > > > > > > > > _______________________________________________ > > ath9k-devel mailing list > > ath9k-devel@lists.ath9k.org > > https://lists.ath9k.org/mailman/listinfo/ath9k-devel > > > > > -- > Regards, > Oleksij > >
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