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Message-ID: <AANLkTikfW_PfYVfA-9cSx8-j16OuH6mr9K32apPj6nLy@mail.gmail.com>
Date: Wed, 4 Aug 2010 19:22:58 +0800
From: Changli Gao <xiaosuo@...il.com>
To: Krishna Kumar <krkumar2@...ibm.com>
Cc: davem@...emloft.net, arnd@...db.de, mst@...hat.com,
netdev@...r.kernel.org, bhutchings@...arflare.com,
therbert@...gle.com
Subject: Re: [PATCH v4 1/2] core: Factor out flow calculation from get_rps_cpu
On Wed, Aug 4, 2010 at 6:55 PM, Krishna Kumar <krkumar2@...ibm.com> wrote:
> From: Krishna Kumar <krkumar2@...ibm.com>
>
> Factor out flow calculation code from get_rps_cpu, since other
> functions can use the same code.
>
> Revisions:
>
> v2 - Ben: Separate flow calcuation out and use in select queue.
> v3 - Arnd: Don't re-implement MIN.
> v4 - Changli: skb->data points to ethernet header in macvtap, and
> make a fast path.
>
> Tested macvtap with this patch.
>
> Signed-off-by: Krishna Kumar <krkumar2@...ibm.com>
> ---
> include/linux/skbuff.h | 11 ++++
> net/core/dev.c | 107 ++++++++++++++++++++++-----------------
> 2 files changed, 74 insertions(+), 44 deletions(-)
>
> diff -ruNp org/include/linux/skbuff.h new/include/linux/skbuff.h
> --- org/include/linux/skbuff.h 2010-08-04 09:07:05.000000000 +0530
> +++ new/include/linux/skbuff.h 2010-08-04 16:19:30.000000000 +0530
> @@ -558,6 +558,17 @@ extern unsigned int skb_find_text(stru
> unsigned int to, struct ts_config *config,
> struct ts_state *state);
>
> +extern __u32 __skb_get_rxhash(struct sk_buff *skb);
> +static inline __u32 skb_get_rxhash(struct sk_buff *skb)
> +{
> + __u32 rxhash = skb->rxhash;
> +
> + if (!rxhash)
> + rxhash = __skb_get_rxhash(skb);
> +
> + return rxhash;
> +}
> +
> #ifdef NET_SKBUFF_DATA_USES_OFFSET
> static inline unsigned char *skb_end_pointer(const struct sk_buff *skb)
> {
> diff -ruNp org/net/core/dev.c new/net/core/dev.c
> --- org/net/core/dev.c 2010-08-04 09:07:05.000000000 +0530
> +++ new/net/core/dev.c 2010-08-04 16:19:30.000000000 +0530
> @@ -2259,69 +2259,41 @@ static inline void ____napi_schedule(str
> __raise_softirq_irqoff(NET_RX_SOFTIRQ);
> }
>
> -#ifdef CONFIG_RPS
> -
> -/* One global table that all flow-based protocols share. */
> -struct rps_sock_flow_table *rps_sock_flow_table __read_mostly;
> -EXPORT_SYMBOL(rps_sock_flow_table);
> -
> /*
> - * get_rps_cpu is called from netif_receive_skb and returns the target
> - * CPU from the RPS map of the receiving queue for a given skb.
> - * rcu_read_lock must be held on entry.
> + * __skb_get_rxhash: calculate a flow hash based on src/dst addresses
> + * and src/dst port numbers. On success, returns a non-zero hash number,
> + * otherwise 0.
> */
> -static int get_rps_cpu(struct net_device *dev, struct sk_buff *skb,
> - struct rps_dev_flow **rflowp)
> +__u32 __skb_get_rxhash(struct sk_buff *skb)
> {
> + int nhoff, hash = 0;
> struct ipv6hdr *ip6;
> struct iphdr *ip;
> - struct netdev_rx_queue *rxqueue;
> - struct rps_map *map;
> - struct rps_dev_flow_table *flow_table;
> - struct rps_sock_flow_table *sock_flow_table;
> - int cpu = -1;
> u8 ip_proto;
> - u16 tcpu;
> u32 addr1, addr2, ihl;
> union {
> u32 v32;
> u16 v16[2];
> } ports;
>
> - if (skb_rx_queue_recorded(skb)) {
> - u16 index = skb_get_rx_queue(skb);
> - if (unlikely(index >= dev->num_rx_queues)) {
> - WARN_ONCE(dev->num_rx_queues > 1, "%s received packet "
> - "on queue %u, but number of RX queues is %u\n",
> - dev->name, index, dev->num_rx_queues);
> - goto done;
> - }
> - rxqueue = dev->_rx + index;
> - } else
> - rxqueue = dev->_rx;
> -
> - if (!rxqueue->rps_map && !rxqueue->rps_flow_table)
> - goto done;
> -
> - if (skb->rxhash)
> - goto got_hash; /* Skip hash computation on packet header */
> + nhoff = skb_network_offset(skb);
>
> switch (skb->protocol) {
> case __constant_htons(ETH_P_IP):
> - if (!pskb_may_pull(skb, sizeof(*ip)))
> + if (!pskb_may_pull(skb, sizeof(*ip) + nhoff))
> goto done;
>
> - ip = (struct iphdr *) skb->data;
> + ip = (struct iphdr *) skb->data + nhoff;
> ip_proto = ip->protocol;
> addr1 = (__force u32) ip->saddr;
> addr2 = (__force u32) ip->daddr;
> ihl = ip->ihl;
> break;
> case __constant_htons(ETH_P_IPV6):
> - if (!pskb_may_pull(skb, sizeof(*ip6)))
> + if (!pskb_may_pull(skb, sizeof(*ip6) + nhoff))
> goto done;
>
> - ip6 = (struct ipv6hdr *) skb->data;
> + ip6 = (struct ipv6hdr *) skb->data + nhoff;
> ip_proto = ip6->nexthdr;
> addr1 = (__force u32) ip6->saddr.s6_addr32[3];
> addr2 = (__force u32) ip6->daddr.s6_addr32[3];
> @@ -2330,6 +2302,7 @@ static int get_rps_cpu(struct net_device
> default:
> goto done;
> }
> +
> switch (ip_proto) {
> case IPPROTO_TCP:
> case IPPROTO_UDP:
> @@ -2338,8 +2311,9 @@ static int get_rps_cpu(struct net_device
> case IPPROTO_AH:
> case IPPROTO_SCTP:
> case IPPROTO_UDPLITE:
> - if (pskb_may_pull(skb, (ihl * 4) + 4)) {
> - ports.v32 = * (__force u32 *) (skb->data + (ihl * 4));
> + if (pskb_may_pull(skb, (ihl * 4) + 4 + nhoff)) {
> + ports.v32 = * (__force u32 *) (skb->data + nhoff +
> + (ihl * 4));
> if (ports.v16[1] < ports.v16[0])
> swap(ports.v16[0], ports.v16[1]);
> break;
> @@ -2352,11 +2326,56 @@ static int get_rps_cpu(struct net_device
> /* get a consistent hash (same value on both flow directions) */
> if (addr2 < addr1)
> swap(addr1, addr2);
> - skb->rxhash = jhash_3words(addr1, addr2, ports.v32, hashrnd);
> - if (!skb->rxhash)
> - skb->rxhash = 1;
>
> -got_hash:
> + hash = jhash_3words(addr1, addr2, ports.v32, hashrnd);
> + if (!hash)
> + hash = 1;
> +
> +done:
> + return hash;
> +}
> +EXPORT_SYMBOL(__skb_get_rxhash);
> +
> +#ifdef CONFIG_RPS
> +
> +/* One global table that all flow-based protocols share. */
> +struct rps_sock_flow_table *rps_sock_flow_table __read_mostly;
> +EXPORT_SYMBOL(rps_sock_flow_table);
> +
> +/*
> + * get_rps_cpu is called from netif_receive_skb and returns the target
> + * CPU from the RPS map of the receiving queue for a given skb.
> + * rcu_read_lock must be held on entry.
> + */
> +static int get_rps_cpu(struct net_device *dev, struct sk_buff *skb,
> + struct rps_dev_flow **rflowp)
> +{
> + struct netdev_rx_queue *rxqueue;
> + struct rps_map *map;
> + struct rps_dev_flow_table *flow_table;
> + struct rps_sock_flow_table *sock_flow_table;
> + int cpu = -1;
> + u16 tcpu;
> +
> + if (skb_rx_queue_recorded(skb)) {
> + u16 index = skb_get_rx_queue(skb);
> + if (unlikely(index >= dev->num_rx_queues)) {
> + WARN_ONCE(dev->num_rx_queues > 1, "%s received packet "
> + "on queue %u, but number of RX queues is %u\n",
> + dev->name, index, dev->num_rx_queues);
> + goto done;
> + }
> + rxqueue = dev->_rx + index;
> + } else
> + rxqueue = dev->_rx;
> +
> + if (!rxqueue->rps_map && !rxqueue->rps_flow_table)
> + goto done;
> +
> + skb->rxhash = skb_get_rxhash(skb);
the return value of skb_get_rxhash() maybe skb->rxhash, so we don't
need to assign it to skb->rxhash again. Use a local variable to save
the value and __skb_get_rxhash() should cache the rxhash into
skb->rxhash for future use.
> + if (skb->rxhash < 0)
> + goto done;
> +
> flow_table = rcu_dereference(rxqueue->rps_flow_table);
> sock_flow_table = rcu_dereference(rps_sock_flow_table);
> if (flow_table && sock_flow_table) {
>
--
Regards,
Changli Gao(xiaosuo@...il.com)
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