Re: [ath9k-devel] [PATCH RFC] ath9k: collect statistics about Rx-Dup and Rx-STBC packets

[Felix Fietkau <nbd@openwrt.org>]

On 2013-04-28 4:54 PM, Ben Greear wrote:
> On 04/28/2013 05:51 AM, Felix Fietkau wrote:
>> On 2013-04-27 5:25 PM, Oleksij Rempel wrote:
>>> Collect statistics about recived duplicate and STBC packets.
>>> This information should help see if STBC is actually working.
>>>
>>> Tested on ar9285;
>>>
>>> Signed-off-by: Oleksij Rempel <linux@rempel-privat.de>
>> I thought about this patch some more, and I'm wondering what's the point
>> in doing this? These statistics are going to be completely useless for
>> most people and they'll waste some memory/cpu cycles, especially on
>> small-cache devices. I think it's much more useful to simply pass the
>> information to mac80211 via rx flags and get them added to the radiotap
>> header.
>> I'd like to keep the number of 'poor man's debug hacks' in the driver to
>> a minimum, and there are some other things that I think should be
>> removed: rx_frags and rx_beacons in struct ath_rx_stats, the tx/rx MAC
>> sampling hack, and pretty much anything else that can be just as easily
>> accessed from mac80211 through regular interfaces.
> 
> Does that mean we can just put the stats in mac80211, or do we have
> to be running a sniffer to gather the stats?
Right now you'd have to use a sniffer, but if you really care about
getting specific stats it might make sense to write a kernel module that
attaches to a monitor interface and gathers them (maybe even with
support for gathering arbitrary stats by attaching bpf filters).

The problem I have with the current stats is they're just an arbitrary
collection of random stuff that is probably useless for 99% of all
users. In many cases the way the stats are collected also makes the data
completely meaningless (e.g. because the source/destination address is
not taken into account).

Why care about the number of packets on the air that were sent with a
specific rate flag? Why care about the number of beacons on the air
(with no filter on a set of APs or anything)? Or what about the number
of fragments received? To me it just looks like an incoherent set of
useless facts.

- Felix