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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
commit adc9300e78
4 changed files with 26 additions and 16 deletions
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5
include/linux/netdevice.h
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@ -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;