Re: [RFC] mac80211: Re-enable aggregation

[Johannes Berg <johannes@sipsolutions.net>]

[-- Attachment #1: Type: text/plain, Size: 1871 bytes --]

On Thu, 2008-10-23 at 15:01 +0530, Sujith wrote:
> Johannes Berg wrote:
> > It seems that should be a rate control decision? Possibly taking into
> > account more than just always doing aggregation sessions. Then again, I
> > suppose aggregation sessions are cheap. What about latency here?
> > 
> 
> Well, that is what Luis seems to think too, but our RC
> doesn't do much now, so we try to setup an aggregation session with any
> associated STA.

If that was done in the RC at least (could easily be moved I suppose)
and you cleaned up the RC, then surely nbd would play with porting
minstrel and making it aware of such things, which probably makes for a
better RC... And since you have to clean up the RC anyway :)

> > "maintain minimum HW queue depth"? In what way? You mean put in enough
> > frames?
> 
> I was talking about this:
> (txq->axq_depth < ATH_AGGR_MIN_QDEPTH) in ath_tx_sched_aggr()@xmit.c

But what does this invariant mean? ATH_AGGR_MIN_QDEPTH is 2.

> > > Well, I really don't know how this would affect performance, but
> > > I think this _might_ be a better model.
> > 
> > Where would you see it have a noticeable effect on performance?
> 
> How would mac80211 buffer frames ? 

Well I suppose it would just put them on a list in the sta_info struct.

> Would it wait for enough sub-frames
> to fill an A-MPDU ?

It should, no? And if for some reason that doesn't happen fast enough it
can send them out anyway, it'll just be a shorter A-MPDU, no?

>  When does it decide that buffered frames have to
> be pushed down to the driver ?

When the A-MPDU is full, subject to the TX and RX constraints, or when
too much time has passed maybe?

I really don't know. But I'd like to get to a model where we can
implement other drivers without having to keep track of all this like
ath9k does.

johannes

[-- Attachment #2: This is a digitally signed message part --]
[-- Type: application/pgp-signature, Size: 836 bytes --]