Re: Reporting firmware stats to ethtool

[Kalle Valo <kvalo@qca.qualcomm.com>]

Ben Greear <greearb@candelatech.com> writes:

> 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.

That's not very reliable as "less than previous" assumption is not
always true.

> 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.

Yeah, and we can always fix this later if there's a sudden need to get
reliable numbers.

-- 
Kalle Valo