[ofa-general] Re: [PATCH 2/3][NET_BATCH] net core use batching

[David Miller <davem@davemloft.net>]

From: jamal <hadi@cyberus.ca>
Date: Mon, 08 Oct 2007 16:48:50 -0400

> On Mon, 2007-08-10 at 12:46 -0700, Waskiewicz Jr, Peter P wrote:
> 
> > 	I still have concerns how this will work with Tx multiqueue.
> > The way the batching code looks right now, you will probably send a
> > batch of skb's from multiple bands from PRIO or RR to the driver.  For
> > non-Tx multiqueue drivers, this is fine.  For Tx multiqueue drivers,
> > this isn't fine, since the Tx ring is selected by the value of
> > skb->queue_mapping (set by the qdisc on {prio|rr}_classify()).  If the
> > whole batch comes in with different queue_mappings, this could prove to
> > be an interesting issue.
> 
> true, that needs some resolution. Heres a hand-waving thought:
> Assuming all packets of a specific map end up in the same qdiscn queue,
> it seems feasible to ask the qdisc scheduler to give us enough packages
> (ive seen people use that terms to refer to packets) for each hardware
> ring's available space. With the patches i posted, i do that via
> dev->xmit_win that assumes only one view of the driver; essentially a
> single ring.  
> If that is doable, then it is up to the driver to say
> "i have space for 5 in ring[0], 10 in ring[1] 0 in ring[2]" based on
> what scheduling scheme the driver implements - the dev->blist can stay
> the same. Its a handwave, so there may be issues there and there could
> be better ways to handle this.

Add xmit_win to struct net_device_subqueue, problem solved.