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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);
+ }
}
}
--
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