Re: [PATCH 4/4] ath9k: Support ethtool getstats api.

[Felix Fietkau <nbd@openwrt.org>]

On 2012-03-16 5:23 PM, Ben Greear wrote:
> On 03/16/2012 08:06 AM, Felix Fietkau wrote:
>> On 2012-03-16 12:20 AM, greearb@candelatech.com wrote:
>>> From: Ben Greear<greearb@candelatech.com>
>>>
>>> This returns many of the values that formerly could
>>> only be obtained from debugfs.  This should be an
>>> improvement when trying to access these counters
>>> programatically.  Currently this support is only
>>> enabled when DEBUGFS is enabled because otherwise
>>> these stats are not accumulated.
>>>
>>> Signed-off-by: Ben Greear<greearb@candelatech.com>
>> I don't really like the idea just throwing every random counter into
>> ethtool. Many of these counters are actually quite misleading, not
>> properly tracked, or not even updated properly, and thus do not deserve
>> to be made visible through ethtool.
>>
>> I think before something gets exported that way, it should be made clear
>> what it's for and what the limitations are.
> 
> My personal goal is to give my users a better insight into their
> wireless environment.  I would like to be able to break out the
> various low-level errors (as well as add them together to present
> summary errors).
> 
> For anyone reporting mysterious bugs on mailing lists and such, I'd like
> to ask them to dump the stats and send it to me/list/whatever.
> I am still of the mind that looking for patterns in various
> counters might point to underlying problems, so anything that
> makes it easier to get that data is a win in my mind.
That's what debugfs is for, and it's not exactly hard to use.
I think it would be bad if tools started depending on the counters in
their current state, they're pretty messy.

> If there are some stats that really don't work, maybe I
> will notice, or maybe someone else will and we can fix
> them.  If you are aware of any specific ones that don't
> work right, please let me know and I'll at least add some
> comments to the code to mention they are questionable,
> or fix them if I'm able.
There's lots of confusion in the AMPDU/Aggregates counters (some count
whole A-MPDUs, some count subframes).
Also, many of these counters are useless unless you're doing live
debugging and actually know what you're doing - especially the ones that
display the current queue state.
Most of the PHY error counters aren't even tracked by the hw, nothing in
the driver enables their use.

For some of these counters it might make sense to track them in
mac80211, as they're sufficiently generic.

If you really want to export more stats, please put some thought into
what actually makes sense for exporting, rather than carpet-bombing the
stats with every random debugfs counter crap you can find.

- Felix