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RFC [PATCH net-2.6 3/6] net: softRSS net changes

PATCH Tom Herbert 1 participant 1 message Mar 5, 2008

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Networking Network drivers
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Tom Herbert

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This patch adds support for software RSS in the networking layer.

Signed-off-by Tom Herbert <[email protected]>

---

include/linux/netdevice.h +41 -3
diff -uprN -X /tmp/donts/rss_1 net-2.6/include/linux/netdevice.h net-2.6.patch/include/linux/netdevice.h
@@ -308,10 +308,15 @@ struct napi_struct {
 	unsigned long		state;
 	int			weight;
 	int			(*poll)(struct napi_struct *, int);
+#ifdef CONFIG_NET_NAPI_RSS
+	int			last_rx_cpu;
+#endif
+#if defined(CONFIG_NETPOLL) || defined(CONFIG_NET_NAPI_RSS)
+	struct net_device	*dev;
+#endif
 #ifdef CONFIG_NETPOLL
 	spinlock_t		poll_lock;
 	int			poll_owner;
-	struct net_device	*dev;
 	struct list_head	dev_list;
 #endif
 };

@@ -607,6 +612,12 @@ struct net_device
 	/* ingress path synchronizer */
 	spinlock_t		ingress_lock;
 	struct Qdisc		*qdisc_ingress;
+#ifdef CONFIG_NET_SOFTRSS
+	cpumask_t		soft_rss_cpus;
+#endif
+#ifdef CONFIG_NET_NAPI_RSS
+	cpumask_t		napi_rss_cpus;
+#endif
 
 /*
  * Cache line mostly used on queue transmit path (qdisc)

@@ -767,8 +778,10 @@ static inline void netif_napi_add(struct
 	INIT_LIST_HEAD(&napi->poll_list);
 	napi->poll = poll;
 	napi->weight = weight;
-#ifdef CONFIG_NETPOLL
+#if defined(CONFIG_NETPOLL) || defined(CONFIG_NET_NAPI_RSS)
 	napi->dev = dev;
+#endif
+#ifdef CONFIG_NETPOLL
 	list_add(&napi->dev_list, &dev->napi_list);
 	spin_lock_init(&napi->poll_lock);
 	napi->poll_owner = -1;

@@ -888,6 +901,10 @@ struct softnet_data
 	struct net_device	*output_queue;
 	struct sk_buff_head	input_pkt_queue;
 	struct list_head	poll_list;
+#if defined(CONFIG_NET_NAPI_RSS) || defined(CONFIG_NET_SOFTRSS)
+	struct list_head	rss_poll_list;
+	spinlock_t		rss_poll_list_lock;
+#endif
 	struct sk_buff		*completion_queue;
 
 	struct napi_struct	backlog;

@@ -1085,7 +1102,28 @@ extern void dev_kfree_skb_any(struct sk_
 extern int		netif_rx(struct sk_buff *skb);
 extern int		netif_rx_ni(struct sk_buff *skb);
 #define HAVE_NETIF_RECEIVE_SKB 1
-extern int		netif_receive_skb(struct sk_buff *skb);
+extern int		__netif_receive_skb(struct sk_buff *skb);
+
+#ifdef CONFIG_NET_NAPI_RSS
+extern int sysctl_napi_rss;
+#endif
+
+#ifdef CONFIG_NET_SOFTRSS
+extern int sysctl_soft_rss;
+static inline int netif_receive_skb(struct sk_buff *skb)
+{
+	if (sysctl_soft_rss)
+		return (netif_rx(skb));
+	else
+		return (__netif_receive_skb(skb));
+}
+#else
+static inline int netif_receive_skb(struct sk_buff *skb)
+{
+	return (__netif_receive_skb(skb));
+}
+#endif
+
 extern int		dev_valid_name(const char *name);
 extern int		dev_ioctl(struct net *net, unsigned int cmd, void __user *);
 extern int		dev_ethtool(struct net *net, struct ifreq *);
net/Kconfig +32 -0
diff -uprN -X /tmp/donts/rss_1 net-2.6/net/Kconfig net-2.6.patch/net/Kconfig
@@ -35,6 +35,38 @@ config NET_NS
 	  Allow user space to create what appear to be multiple instances
 	  of the network stack.
 
+config NET_NAPI_RSS
+	bool "NAPI RSS"
+	help
+	  Say Y here to enable NAPI RSS.  In this mode the execution of the
+	  NAPI poll function for each device is spread across CPUs in a
+	  round robin fashion.  Each time the poll function runs it gets
+	  scheduled on the next CPU in the round robin.
+
+	  A mask of CPUs that can be used is set on a per device basis
+	  in the sysfs variable /sys/class/net/<device>/napi_rss_cpus. This
+	  feature needs to  be enabled at run-time by setting the
+	  net.core.napi_rss sysctl to "1".
+
+config NET_SOFTRSS
+	bool "Software RSS"
+	help
+	  Say Y here to enable a software implementation of receive side
+	  scaling (RSS).  RSS distributes the load of received
+	  packet processing across multiple CPUs.  In this software
+	  implementation of RSS, stack processing for each packet can be
+	  scheduled on a different CPU from that which handles the device
+	  interrupt or NAPI poll.  The scheduling is done by the netif_rx
+	  function which uses a hash over fields in the packet header into
+	  a CPU identifier. For example, in the case of a TCP packet, the
+	  four tuple is hashed to choose a CPU for processing all packets of
+	  that connection.
+
+	  A mask of CPUs that can be used is set on a per device basis
+	  in the sysfs variable /sys/class/net/<device>/soft_rss_cpus. This
+	  feature needs to  be enabled at run-time by setting the
+	  net.core.soft_rss sysctl to "1".
+
 source "net/packet/Kconfig"
 source "net/unix/Kconfig"
 source "net/xfrm/Kconfig"
net/core/dev.c +188 -12

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