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net: use jump_label to shortcut RPS if not setup

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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>
This commit is contained in:
Eric Dumazet
2011-11-17 03:13:26 +00:00
committed by David S. Miller
parent d6f144830b
commit adc9300e78
4 changed files with 26 additions and 16 deletions
Download Patch File Download Diff File Expand all files Collapse all files

7
net/core/net-sysfs.c
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@@ -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;
}