netdev - Re: [PATCH v5] rps: Receive Packet Steering

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Date:	Thu, 21 Jan 2010 15:54:13 +0800
From:	Changli Gao <xiaosuo@...il.com>
To:	Tom Herbert <therbert@...gle.com>
Cc:	davem@...emloft.net, netdev@...r.kernel.org
Subject: Re: [PATCH v5] rps: Receive Packet Steering

On Fri, Jan 15, 2010 at 5:56 AM, Tom Herbert <therbert@...gle.com> wrote:
> +/*
> + * get_rps_cpu is called from netif_receive_skb and returns the target
> + * CPU from the RPS map of the receiving NAPI instance for a given skb.
> + */
> +static int get_rps_cpu(struct net_device *dev, struct sk_buff *skb)
> +{
> +       u32 addr1, addr2, ports;
> +       struct ipv6hdr *ip6;
> +       struct iphdr *ip;
> +       u32 ihl;
> +       u8 ip_proto;
> +       int cpu = -1;
> +       struct dev_rps_maps *drmap;
> +       struct rps_map *map = NULL;
> +       u16 index;
> +
> +       rcu_read_lock();
> +
> +       drmap = rcu_dereference(dev->dev_rps_maps);
> +       if (!drmap)
> +               goto done;
> +
> +       index = skb_get_rx_queue(skb);
> +       if (index >= drmap->num_maps)
> +               index = 0;
> +
> +       map = (struct rps_map *)
> +           ((void *)drmap->maps + (rps_map_size * index));
> +       if (!map->len)
> +               goto done;
> +
> +       if (skb->rxhash)
> +               goto got_hash; /* Skip hash computation on packet header */
> +

Sometimes, rxhash will be 0 generated. In order to check whether
rxhash is generated or not, a new bit field in sk_buff is needed. When
rxhash is generated and saved in sk_buff, the bit is set.

And, I think rxhash should be reserved when calling skb_copy and skb_clone.


-- 
Regards，
Changli Gao(xiaosuo@...il.com)
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