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

[Eric Dumazet <eric.dumazet@gmail.com>]

Le vendredi 26 février 2010 à 01:15 -0800, Jeff Kirsher a écrit :
> From: John Fastabend <john.r.fastabend@intel.com>
> 
> Instead of allocating 128 struct netdev_queue per device, use the
> minimum value between 128 and the number of possible txq's, to
> reduce ram usage and "tc -s -d class shod dev .." output.
> 
> This patch fixes Eric Dumazet's patch to set the TX queues to
> the correct minimum.
> 
> Signed-off-by: John Fastabend <john.r.fastabend@intel.com>
> Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
> ---
> 
>  drivers/net/ixgbe/ixgbe_main.c |   14 +++++++++++++-
>  1 files changed, 13 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/net/ixgbe/ixgbe_main.c b/drivers/net/ixgbe/ixgbe_main.c
> index 4a01022..a961da2 100644
> --- a/drivers/net/ixgbe/ixgbe_main.c
> +++ b/drivers/net/ixgbe/ixgbe_main.c
> @@ -5996,6 +5996,7 @@ static int __devinit ixgbe_probe(struct pci_dev *pdev,
>  	const struct ixgbe_info *ii = ixgbe_info_tbl[ent->driver_data];
>  	static int cards_found;
>  	int i, err, pci_using_dac;
> +	unsigned int indices = num_possible_cpus();
>  #ifdef IXGBE_FCOE
>  	u16 device_caps;
>  #endif
> @@ -6034,7 +6035,18 @@ static int __devinit ixgbe_probe(struct pci_dev *pdev,
>  	pci_set_master(pdev);
>  	pci_save_state(pdev);
>  
> -	netdev = alloc_etherdev_mq(sizeof(struct ixgbe_adapter), MAX_TX_QUEUES);
> +	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 ?