On 20 October 2011 05:35, Bryan Phillippe b...@terran.org wrote:
Hi All,
After upgrading to compat-wireless-2011-10-10 and hostapd-0.7.3 on my
IXP4xx-based ARM Access Point, I'm seeing dramatically-improved stability and
performance. Great work!
Under these combinations of software, I'm seeing long-term AP associations
maintained by the clients (no longer getting the drops and disconnects I was
seeing in previous versions); pretty good performance; and stable memory use.
However, I've noted two issues that I'd like to explore with your help. The
first is that, under enough load, I still see this:
ath: Failed to stop TX DMA!
Hm, that bug has been in FreeBSD/Linux for quite a while. I don't
think we've ever figured out what it is, and it's likely some kind of
magical cross-section of architecture, utilisation and NIC version.
So, call it hard to figure out.
This message doesn't really seem to coincide with a functional problem, so
perhaps I can just safely ignore it...
Yeah, it's likely something to do with cabq traffic being disabled and
being unable to. Don't worry about it for now.
The other problem I'm seeing is that when I have a lot of clients connected -
say, 20 or so - performance degrades pretty steeply and I start seeing high
packet loss. I know that sounds like a pure load issue, but I'd like to make
sure it's only that and not some efficiency setting I can tune in the driver.
I do NOT see this kind of performance degradation if I have the same 20
people connected to the AP via a wired connection, doing the same traffic
test - so that seems to suggest the WiFi is suffering early.
Thoughts or suggestions? Tests I can run? Data I can gather?
Well, if you reach 20 people, there are a few questions:
* are they saturating the air? is it something that can be fixed by
driver hacking?
* is it a tx or rx problem? or both?
* have you hit some driver limit (eg ran out of crypto keycache slots
and some clients are being done in software? or all? or an even worse
failure mode?) ?
I'd suggest grabbing some kind of diagnostic tool (eg wispy or
something similar) and see how busy the spectrum is. The
driver/mac80211 can give you some idea of how busy it sees the air
being but I don't know whether the survey results are available in
hostap mode. (iw survey, I think?)
So the answer is maybe, but you need to do further digging.
Adrian
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