netdev - Re: [PATCHv2 net-next 2/2] sunvnet: Use one Tx queue per vnet

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Message-ID: <1415291564.3398.66.camel@decadent.org.uk>
Date:	Thu, 06 Nov 2014 16:32:44 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	Sowmini Varadhan <sowmini.varadhan@...cle.com>
Cc:	davem@...emloft.net, netdev@...r.kernel.org
Subject: Re: [PATCHv2 net-next 2/2] sunvnet: Use one Tx queue per vnet_port

On Thu, 2014-11-06 at 11:28 -0500, Sowmini Varadhan wrote:
> On (11/06/14 16:19), Ben Hutchings wrote:
> > > +	txq = netdev_get_tx_queue(port->vp->dev, port->q_index);
> > > +	__netif_tx_lock(txq, smp_processor_id());
> > > +	if (likely(netif_tx_queue_stopped(txq))) {
> > > +		struct vio_dring_state *dr;
> > > +
> > > +		dr = &port->vio.drings[VIO_DRIVER_TX_RING];
> > 
> > You seem to have dropped the condition for the netif_tx_wake_queue(),
> > which I would guess based on the old code should be:
> > 
> > 		if (vnet_tx_dring_avail(dr) >= VNET_TX_WAKEUP_THRESH(dr))
> > 
> > > +			netif_tx_wake_queue(txq);
> 
> yes, this was deliberate.
> 
> As I indicated in the comments:
> 
> /* Got back a STOPPED LDC message on port. If the queue is stopped,
>  * wake it up so that we'll send out another START message at the
>  * next TX.
>  */
> 
> We only call maybe_tx_wakeup() if the peer has sent us a STOPPED
> ack (meaning that the peer is no longer reading the descriptor rings).
> So if our tx queue is full and stopped, we need to poke the peer
> on the next TX with a start message. (otherwise we'd never wake up!)

OK, then the indentation of the following line is wrong.

Ben.

-- 
Ben Hutchings
Beware of programmers who carry screwdrivers. - Leonard Brandwein

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