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

[Felix Fietkau <nbd@openwrt.org>]

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.

- Felix