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

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Date:	Sun, 28 Feb 2010 04:57:00 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@...el.com>
Cc:	"Kirsher, Jeffrey T" <jeffrey.t.kirsher@...el.com>,
	"davem@...emloft.net" <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"gospo@...hat.com" <gospo@...hat.com>,
	"Fastabend, John R" <john.r.fastabend@...el.com>
Subject: Re: [net-next-2.6 PATCH 3/3] ixgbe: Do not allocate too many
 netdev txqueues

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


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