Re: [WT PATCH 4/6] mac80211: Add per-sdata station hash, and sdata hash.

[Ben Greear <greearb@candelatech.com>]

On 07/26/2013 02:56 AM, Felix Fietkau wrote:
> On 2013-07-26 10:53 AM, Johannes Berg wrote:
>> On Thu, 2013-07-11 at 08:29 -0700, Ben Greear wrote:
>>
>>>> I also don't like maintaining two separate hash tables and all that.
>>>>
>>>> I'd reconsider if you actually remove the hash entirely, but that'll be
>>>> tricky to walk the station list and will quite possibly make the RX path
>>>> there more expensive?
>>>
>>> Remove local->sta_hash ?
>>
>> To be honest, I'm undecided. Yes, I was thinking that, but I also think
>> having a huge hashtable like that for each virtual interface is way
>> overkill, in particular for station interfaces that usually have one
>> peer (the AP) and maybe a few TDLS peers. Or P2P-Device interfaces that
>> have no peers at all ...
>>
>> I don't see a good way to improve the hash either, since we don't always
>> (e.g. in RX path) have the interface address.
> How about mixing in the interface address into the hash. Theoretically
> you should always have that available, even in the rx path. Multicast
> data packets contain the BSSID, so you can get the address from there.
> You just need to be careful about checking the DS bits to figure out
> which address to use ;)
> I think this is a much better solution than duplicating the hash, or
> moving it into sdata entirely.

I think I could probably get rid of the big global per wiphy hash and
use the per-wiphy sdata-hash and per-sdata station hashes.

To me, that is cleanest because it gives a nice ownership relationship
between wiphy, sdata, and stations.

For what it's worth, my hashing scheme has been working well on highly
loaded APs and Station machines.

Thanks,
Ben

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