Subject: Re: [net-next-2.6 PATCH 3/3] ixgbe: Do not allocate too many netdev txqueues

From: Peter P Waskiewicz Jr <[email-masked]>
Date: Sun, 28 Feb 2010 23:21:37 -0800

On Sat, 2010-02-27 at 20:57 -0700, Eric Dumazet wrote:
> Le samedi 27 février 2010 à 17:02 -0800, Peter P Waskiewicz Jr a écrit :
> > On Fri, 2010-02-26 at 06:04 -0800, Eric Dumazet wrote:
> > > Le vendredi 26 février 2010 à 01:15 -0800, Jeff Kirsher a écrit :
> > > > +	if (ii->mac == ixgbe_mac_82598EB)
> > > > +		indices = min_t(unsigned int, indices, IXGBE_MAX_RSS_INDICES);
> > > > +	else
> > > > +		indices = min_t(unsigned int, indices, IXGBE_MAX_FDIR_INDICES);
> > > > +
> > > > +	indices = max_t(unsigned int, indices, IXGBE_MAX_DCB_INDICES);
> > > > +#ifdef IXGBE_FCOE
> > > > +	indices += min_t(unsigned int, num_possible_cpus(),
> > > > +			 IXGBE_MAX_FCOE_INDICES);
> > > > +#endif
> > > > +	indices = min_t(unsigned int, indices, MAX_TX_QUEUES);
> > > > +	netdev = alloc_etherdev_mq(sizeof(struct ixgbe_adapter), indices);
> > > >  	if (!netdev) {
> > > >  		err = -ENOMEM;
> > > >  		goto err_alloc_etherdev;
> > > > 
> > > 
> > > Thanks Jeff, but what is the reason for limiting to MAX_TX_QUEUES ?
> > > Is it a hardware issue ?
> > > 
> > 
> > MAX_TX_QUEUES is 128, which is the maximum the 82599 device supports in
> > hardware (82598 supports 32 Tx queues).  I'm not sure why you'd ever
> > want to have more Tx queues than what you have in the network device.
> 
> I was not sure MAX_TX_QUEUES capping was still necessary after the
> block :
> 
> if (ii->mac == ixgbe_mac_82598EB)
>           indices = min_t(unsigned int, indices, IXGBE_MAX_RSS_INDICES);
> else
>           indices = min_t(unsigned int, indices,
> IXGBE_MAX_FDIR_INDICES);
> 
> indices = max_t(unsigned int, indices, IXGBE_MAX_DCB_INDICES);
> #ifdef IXGBE_FCOE
> 	indices += min_t(unsigned int, num_possible_cpus(),
>                     IXGBE_MAX_FCOE_INDICES);
> #endif
> 
> So I asked to be sure that MAX_TX_QUEUES was not a leftover from the
> previous default allocation.
> 
> Thanks

I see what you're getting at now.  The most we could have from this
codepath is 72 indices for 82599, and 24 for 82598, so yeah, this is
probably unneeded.

We can get the patch cleaned up.

Cheers,
-PJ