Re: Reporting firmware stats to ethtool

[Ben Greear <greearb@candelatech.com>]

On 08/08/2014 08:55 AM, Dave Taht wrote:
> On Fri, Aug 8, 2014 at 8:42 AM, Ben Greear <greearb@candelatech.com> wrote:
>> On 08/08/2014 02:06 AM, Kalle Valo wrote:
>>> Ben Greear <greearb@candelatech.com> writes:
>>>
>>>> I'm working on a patch to report the stats seen in debugfs/...ath10k/fw_stats
>>>> as ethtool stats, somewhat similar to how ath9k does it.
>>>>
>>>> I notice that my user-space tool is reporting huge numbers because
>>>> the stats are reset to zero when firmware restarts, and so my tool
>>>> thinks the stats wrapped.
>>>>
>>>> I can fix my tool easily enough, but I first wanted to see if
>>>> anyone had strong feelings about keeping the stats from resetting
>>>> to zero by storing history and calculating diffs in the driver.
>>>>
>>>> I think my preference is to punt this to user-space, but if
>>>> someone feels otherwise, please let me know sooner than later.
>>>
>>> I also prefer to have this in user space, but how does user space know
>>> when the stats have been zeroed?
>>
>> Poll often enough that it cannot increment more than 2 billion (or other large number)
>> between polls, and then if polled value is less than previous (and difference is > 2 billion),
>> we know we had a reset and not a wrap.
> 
> I do kind of prefer 64 bit counters in the general case. Nuke it from
> orbit, it's the only way to be sure.

It's 64-bit to user-space, but that means nothing because firmware
uses 32-bit (or even 16 bit in some cases, probably) internally.
A great deal of counters are the same, so be very careful when
trying to keep long term counters grabbed from firmware/drivers/hardware.

And, stations come and go when you re-associate, so all sorts of wifi counters
reset themselves all the time...

Thanks,
Ben

> 
>> User-space stats will not be perfect in the case of firmware resets, or resets
>> after the 'large number', but nothing is going to make it perfect, and in
>> practice, this seems good enough.
>>
>> Thanks,
>> Ben
>>
>> --
>> Ben Greear <greearb@candelatech.com>
>> Candela Technologies Inc  http://www.candelatech.com
>>
>>
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> 
> 
> 


-- 
Ben Greear <greearb@candelatech.com>
Candela Technologies Inc  http://www.candelatech.com