netdev - Re: [net-next-2.6 PATCH v2] net: implement mechanism for HW based QOS

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Date:	Mon, 20 Dec 2010 22:48:07 +0000
From:	Ben Hutchings <bhutchings@...arflare.com>
To:	John Fastabend <john.r.fastabend@...el.com>
Cc:	davem@...emloft.net, netdev@...r.kernel.org, hadi@...erus.ca,
	shemminger@...tta.com, tgraf@...radead.org, eric.dumazet@...il.com,
	nhorman@...driver.com
Subject: Re: [net-next-2.6 PATCH v2] net: implement mechanism for HW based
 QOS

On Fri, 2010-12-17 at 08:56 -0800, John Fastabend wrote:
[...]
> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> index cc916c5..c5d7949 100644
> --- a/include/linux/netdevice.h
> +++ b/include/linux/netdevice.h
> @@ -646,6 +646,12 @@ struct xps_dev_maps {
>      (nr_cpu_ids * sizeof(struct xps_map *)))
>  #endif /* CONFIG_XPS */
>  
> +/* HW offloaded queuing disciplines txq count and offset maps */
> +struct netdev_tc_txq {
> +	u16 count;
> +	u16 offset;
> +};
> +
>  /*
>   * This structure defines the management hooks for network devices.
>   * The following hooks can be defined; unless noted otherwise, they are
> @@ -1146,6 +1152,9 @@ struct net_device {
>  	/* Data Center Bridging netlink ops */
>  	const struct dcbnl_rtnl_ops *dcbnl_ops;
>  #endif
> +	u8 num_tc;
> +	struct netdev_tc_txq tc_to_txq[16];
> +	u8 prio_tc_map[16];

That seems like a fair amount of data to add to every net device,
considering that users may create e.g. a lot of VLAN devices and they
won't use this state at all.  Have you considered putting these in a
structure that is accessed indirectly?

>  #if defined(CONFIG_FCOE) || defined(CONFIG_FCOE_MODULE)
>  	/* max exchange id for FCoE LRO by ddp */
> @@ -1162,6 +1171,57 @@ struct net_device {
>  #define	NETDEV_ALIGN		32
>  
>  static inline
> +int netdev_get_prio_tc_map(const struct net_device *dev, u32 prio)
> +{
> +	return dev->prio_tc_map[prio & 15];
> +}
> +
> +static inline
> +int netdev_set_prio_tc_map(struct net_device *dev, u8 prio, u8 tc)
> +{
> +	if (tc >= dev->num_tc)
> +		return -EINVAL;
> +
> +	dev->prio_tc_map[prio & 15] = tc & 15;
> +	return 0;
> +}
[...]

Please name the magic numbers 15 and 16.

Ben.

-- 
Ben Hutchings, Senior Software Engineer, Solarflare Communications
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

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