Re: [PATCH v2 2/4] knownnetworks: sort known frequencies by BSS rank

[James Prestwood <prestwoj@gmail.com>]

Hi Denis,

On 1/24/24 11:06 AM, Denis Kenzior wrote:
> Hi James,
>
> On 1/24/24 12:55, James Prestwood wrote:
>>
>> On 1/24/24 10:44 AM, Denis Kenzior wrote:
>>> Hi James,
>>>
>>>>> Perhaps an easier way to accomplish this would be to add known 
>>>>> frequencies in reverse bss->rank sorted order.  That way last seen 
>>>>> frequency with best ranked BSS would be first?
>>>>
>>>> I'm not sure I understand, how would this be any different than 
>>>> just reversing
>>>
>>> Well, right now we maintain the least recently seen frequency list 
>>> in a very simple way:
>>>
>>> - When scan results become available
>>>     - Walk the result list (which is sorted by bss_rank?)
>>>     - Add each result's frequency to the frequency cache
>>>         - Remove any matching entry in the cache
>>>         - Add it to head
>>>
>>> Since the result list is sorted, the top entry in the frequency 
>>> cache is the least ranked.  This doesn't matter for small networks 
>>> since there would only be a couple results.
>>>
>>> What we should do is to add the frequencies to the frequency cache 
>>> in reverse order.  That way the highest ranked bss is at the top of 
>>> the frequency cache.

Ok I understand what your getting at now, but providing the list in 
reverse order is somewhat problematic. The majority of additions are 
going to be from station's can results, via network_bss_add(). We 
_could_ reverse the BSS list in station but that seems like an expensive 
operation for each scan, and I really don't want to muck with that code. 
The only somewhat simple place to reverse the list is when a known 
network is added. But again its expensive.

To avoid refactoring elsewhere, I think the only way would be to 
timestamp entries (based on bss->time_stamp) and sort by both rank and 
timestamp. We could also limit the list to e.g. 5 values if we wanted to 
avoid storing a ton of u64's in memory.

Thanks,

James

>>
> Regards,
> -Denis