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() / netif_rx() / 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() / netif_rx() do a single instruction instead of many
ones, including conditional jumps.
jmp +0 (if CONFIG_JUMP_LABEL=y)
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
CC: Tom Herbert <therbert@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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 @@
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;
}