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Date: Thu, 17 Nov 2011 11:33:47 +0100 From: Eric Dumazet <eric.dumazet@...il.com> To: David Miller <davem@...emloft.net> Cc: netdev <netdev@...r.kernel.org>, Tom Herbert <therbert@...gle.com> Subject: [PATCH] net: use jump_label to shortcut RPS if not setup Most machines dont use RPS/RFS, and pay a fair amount of instructions in netif_receive_skb() / get_rps_cpu() just to discover RPS/RFS is not setup. Add a jump_label named rps_needed. If no device rps_map or global rps_sock_flow_table is setup, netif_receive_skb() does a single instruction instead of many ones, including conditional jumps. jmp +0 (if CONFIG_JUMP_LABEL=y) Signed-off-by: Eric Dumazet <eric.dumazet@...il.com> CC: Tom Herbert <therbert@...gle.com> --- include/linux/netdevice.h | 5 +++++ net/core/dev.c | 14 ++++++-------- net/core/net-sysfs.c | 7 +++++-- net/core/sysctl_net_core.c | 9 +++++++-- 4 files changed, 23 insertions(+), 12 deletions(-) diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index 4d5698a..0bbe030 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -214,6 +214,11 @@ enum { #include <linux/cache.h> #include <linux/skbuff.h> +#ifdef CONFIG_RPS +#include <linux/jump_label.h> +extern struct jump_label_key rps_needed; +#endif + struct neighbour; struct neigh_parms; struct sk_buff; diff --git a/net/core/dev.c b/net/core/dev.c index 26c49d5..4c3942c 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -2711,6 +2711,8 @@ EXPORT_SYMBOL(__skb_get_rxhash); struct rps_sock_flow_table __rcu *rps_sock_flow_table __read_mostly; EXPORT_SYMBOL(rps_sock_flow_table); +struct jump_label_key rps_needed __read_mostly; + static struct rps_dev_flow * set_rps_cpu(struct net_device *dev, struct sk_buff *skb, struct rps_dev_flow *rflow, u16 next_cpu) @@ -3359,7 +3361,7 @@ int netif_receive_skb(struct sk_buff *skb) return NET_RX_SUCCESS; #ifdef CONFIG_RPS - { + if (static_branch(&rps_needed)) { struct rps_dev_flow voidflow, *rflow = &voidflow; int cpu, ret; @@ -3370,16 +3372,12 @@ int netif_receive_skb(struct sk_buff *skb) if (cpu >= 0) { ret = enqueue_to_backlog(skb, cpu, &rflow->last_qtail); rcu_read_unlock(); - } else { - rcu_read_unlock(); - ret = __netif_receive_skb(skb); + return ret; } - - return ret; + rcu_read_unlock(); } -#else - return __netif_receive_skb(skb); #endif + return __netif_receive_skb(skb); } EXPORT_SYMBOL(netif_receive_skb); diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c index 602b141..db6c2f8 100644 --- a/net/core/net-sysfs.c +++ b/net/core/net-sysfs.c @@ -606,9 +606,12 @@ static ssize_t store_rps_map(struct netdev_rx_queue *queue, rcu_assign_pointer(queue->rps_map, map); spin_unlock(&rps_map_lock); - if (old_map) + if (map) + jump_label_inc(&rps_needed); + if (old_map) { kfree_rcu(old_map, rcu); - + jump_label_dec(&rps_needed); + } free_cpumask_var(mask); return len; } diff --git a/net/core/sysctl_net_core.c b/net/core/sysctl_net_core.c index 77a65f0..d05559d 100644 --- a/net/core/sysctl_net_core.c +++ b/net/core/sysctl_net_core.c @@ -68,8 +68,13 @@ static int rps_sock_flow_sysctl(ctl_table *table, int write, if (sock_table != orig_sock_table) { rcu_assign_pointer(rps_sock_flow_table, sock_table); - synchronize_rcu(); - vfree(orig_sock_table); + if (sock_table) + jump_label_inc(&rps_needed); + if (orig_sock_table) { + jump_label_dec(&rps_needed); + synchronize_rcu(); + vfree(orig_sock_table); + } } } -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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