Re: [PATCH 2/2] ath9k: Add more recv stats.

[Ben Greear <greearb@candelatech.com>]

On 04/06/2012 09:51 AM, Felix Fietkau wrote:
> On 2012-04-04 5:13 PM, Ben Greear wrote:
>> On 04/04/2012 05:01 AM, Felix Fietkau wrote:
>>
>>>> + * @rx_beacons:  No. of beacons received.
>>>> + * @rx_frags:  No. of rx-fragements received.
>>> Why should the driver keep track of those last two?
>>
>> Well, for instance, I often see around 5Mbps of total rx bytes
>> (as counted by the NIC), but much less transmitted.  And this is
>> with stations sending to stations.
>>
>> I was trying to figure out where the extra packets come from.  It
>> seems beacons is a lot of it so it seemed worth counting.  And maybe
>> fragments count towards that too since there would be more overhead???
>>
>> As for rx-frags, just seemed useful to know how many frags
>> were received.  My understanding is that this is like receiving
>> 1/2 of a packet at a time...so if we wanted to know how many
>> real packets the NIC received, we'd need to take frags v/s non-frags
>> into account.  The current logic that counts 'all-packets' for
>> the rx path is counting individual fragments, I think.
>>
>> At least for beacons, as long as they are always passed up
>> the stack, I can count them in the mac80211 layer instead if
>> you prefer.
> When you only need the packet type based counters for debugging stuff,
> why not just create a monitor mode interface and count in user space?
> I think that would make more sense, since these counters are irrelevant
> for most users, and avoiding unnecessary work in the rx path is useful
> for performance reasons.

I always want to be calculating stats.  I will poll many of them in user-space
every few seconds to generate reports.  It is way easier and more efficient to get
some numbers out of ethtool (or have a user cat a debugfs file)
than it is to set up a sniffer and parse it's output.

If you want me to create another compile-time option for the
extra stats, I can do that?

Thanks,
Ben

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