From: Tim Shepard <shep@alum.mit.edu>
To: Felix Fietkau <nbd@nbd.name>
cc: =?UTF-8?Q?Toke_H=c3=b8iland-J=c3=b8rgensen?= <toke@toke.dk>,
	linux-wireless@vger.kernel.org,
	make-wifi-fast@lists.bufferbloat.net, ath9k-devel@lists.ath9k.org
Subject: Re: [PATCH 1/2] ath9k: use mac80211 intermediate software queues 
In-reply-to: Your message of Fri, 17 Jun 2016 15:28:26 +0200.
             <30beabff-a8c6-5431-be09-8f2f83ffc974@nbd.name>
Date: Fri, 17 Jun 2016 09:41:33 -0400
Message-Id: <E1bDu1d-0007mR-00@www.xplot.org> (sfid-20160617_160809_832305_894EFD84)
Sender: linux-wireless-owner@vger.kernel.org


> > diff --git a/drivers/net/wireless/ath/ath9k/ath9k.h b/drivers/net/wireless/ath/ath9k/ath9k.h
> > index 93b3793..caeae10 100644
> > --- a/drivers/net/wireless/ath/ath9k/ath9k.h
> > +++ b/drivers/net/wireless/ath/ath9k/ath9k.h
> > @@ -145,8 +145,6 @@ int ath_descdma_setup(struct ath_softc *sc, struct ath_descdma *dd,
> >  #define BAW_WITHIN(_start, _bawsz, _seqno) \
> >  	((((_seqno) - (_start)) & 4095) < (_bawsz))
> >  
> > -#define ATH_AN_2_TID(_an, _tidno)  (&(_an)->tid[(_tidno)])
> > -
> >  #define IS_HT_RATE(rate)   (rate & 0x80)
> >  #define IS_CCK_RATE(rate)  ((rate >= 0x18) && (rate <= 0x1e))
> >  #define IS_OFDM_RATE(rate) ((rate >= 0x8) && (rate <= 0xf))
> > @@ -232,8 +230,10 @@ struct ath_buf {
> >  
> >  struct ath_atx_tid {
> >  	struct list_head list;
> > +	struct sk_buff_head i_q;
> Do we really need a third queue here? Instead of adding yet another
> layer of queueing here, I think we should even get rid of buf_q.
> 
> Channel context based queue handling can be dealt with by
> stopping/starting relevant queues on channel context changes.
> 
> buf_q becomes unnecessary when you remove all code in the drv_tx
> codepath that moves frames to the intermediate queue.
> 
> Any frame that was pulled from the intermediate queue and prepared for
> tx, but which can't be sent right now can simply be queued to retry_q.
> 
> This will also help with getting the diffstat insertion/deletion ratio
> under control ;)
> 
> >  	struct sk_buff_head buf_q;
> >  	struct sk_buff_head retry_q;
> > +	struct ieee80211_txq *swq;
> No need for this pointer, you can use container_of.


Felix, great to hear from you and thanks for your feedback.  I will
try to work on this.

I was struggling to understand the channel context stuff, and I have
no idea how to test it.  (Is there anyone else listening who might be
able to help with testing the channel context stuff as we improve this
patch and simplify the ath9k driver's use of the new mac80211
intermediate queues?)


Felix, do you have any thoughts on the renaming of txq to hwx that I
had done in my original version of this patch?  I had a good e-mail
discussion with Toke a week or two ago (cc these same various lists)
and I believe he came to understand that perhaps the renaming I had
done in the original version of this patch was worth doing.

Now in Toke's version of my patch he calls the ieee80211 txq a "swq"
and the ath9k hardware queue is called a "txq".  (I had called the
ieee80211 txq a "txq" and I renamed the ath9k hardware queue "hwq"
throught all the ath9k driver code.    This also made ath9k's names of
things more similar to mt76 which I was looking at as an example of a
driver that uses your new ieee80211 txq mechanism.

I think the renaming is worth doing, but I also understand the
renaming can be disruptive to others actively working on ath9k.
It would be nice to have another opinion on this.


			-Tim Shepard
			 shep@alum.mit.edu