Subject: Re: [RFC] mac80211: move TX status processing to process context
From: Johannes Berg <johannes@sipsolutions.net>
To: "Luis R. Rodriguez" <lrodriguez@atheros.com>
Cc: Luis Rodriguez <Luis.Rodriguez@Atheros.com>,
	"Luis R. Rodriguez" <mcgrof@bombadil.infradead.org>,
	"linux-wireless@vger.kernel.org" <linux-wireless@vger.kernel.org>
In-Reply-To: <20091118211201.GJ6581@tux>
References: <1258571772.30511.54.camel@johannes.local>
	 <20091118195339.GB25188@bombadil.infradead.org>
	 <1258574517.30511.61.camel@johannes.local> <20091118202334.GG6581@tux>
	 <1258576479.30511.65.camel@johannes.local> <20091118210654.GI6581@tux>
	 <20091118211201.GJ6581@tux>
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Date: Wed, 18 Nov 2009 22:13:37 +0100
Message-ID: <1258578817.30511.83.camel@johannes.local>
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On Wed, 2009-11-18 at 13:12 -0800, Luis R. Rodriguez wrote:
> On Wed, Nov 18, 2009 at 01:06:54PM -0800, Luis Rodriguez wrote:
> >=20
> > OK, but can't you still have a driver spam mac80211 with a lot of
> > ieee80211_tx_status_irqsafe() calls in soft irq context with the final
> > skb requiring the tx complete, in that case the queue *will* get stuffe=
d
> > and you could potentially free more if so desired.
> >=20
> > Also, if our goal is to just avoid adding the skb if it does not requir=
e
> > a tx complete and our queue size is too large
>=20
> Hit send too early, I meant if our goal is to avoid adding the skb
> if we've reached our limit why not just ree it immediately instead
> of queing it and dequeing it. Wouldn't we even be able to just
> return and not bother mac80211 about it at all?
>=20
> >=20
> >         if (!(info->flags & IEEE80211_TX_CTL_REQ_TX_STATUS) &&
> >             num + 1 > IEEE80211_TX_STATUS_QUEUE_LIMIT)
> 		{
> >                 dev_kfree_skb_irq(skb);
> 		return;
> 	}
> >         else
> >                 skb_queue_tail(&local->skb_queue)
>=20

Ah. Well, then we still would like them for rate control, just if we
can't keep up we drop older ones.

Not that it makes a whole lot of sense ... if you can't keep up with TX
status how did you manage to TX them to start with?

johannes

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