Hi Eric,

I love your patch! Yet something to improve:

[auto build test ERROR on net-next/master]

url:    https://github.com/0day-ci/linux/commits/Eric-Dumazet/tcp-add-rx-tx-cache-to-reduce-lock-contention/20190322-215506
config: x86_64-randconfig-x016-201911 (attached as .config)
compiler: gcc-7 (Debian 7.3.0-1) 7.3.0
reproduce:
        # save the attached .config to linux build tree
        make ARCH=x86_64 

All errors (new ones prefixed by >>):

   In file included from include/linux/dynamic_debug.h:6:0,
                    from include/linux/printk.h:330,
                    from include/linux/kernel.h:15,
                    from include/linux/list.h:9,
                    from include/linux/module.h:9,
                    from drivers//net/ethernet/intel/e1000/e1000.h:10,
                    from drivers//net/ethernet/intel/e1000/e1000_main.c:4:
   include/net/sock.h: In function 'sk_eat_skb':
>> include/net/sock.h:2442:31: error: 'rps_needed' undeclared (first use in this function); did you mean 'free_netdev'?
     if (!static_branch_unlikely(&rps_needed) && !sk->sk_rx_skb_cache) {
                                  ^
   include/linux/jump_label.h:466:43: note: in definition of macro 'static_branch_unlikely'
     if (__builtin_types_compatible_p(typeof(*x), struct static_key_true)) \
                                              ^
   include/net/sock.h:2442:31: note: each undeclared identifier is reported only once for each function it appears in
     if (!static_branch_unlikely(&rps_needed) && !sk->sk_rx_skb_cache) {
                                  ^
   include/linux/jump_label.h:466:43: note: in definition of macro 'static_branch_unlikely'
     if (__builtin_types_compatible_p(typeof(*x), struct static_key_true)) \
                                              ^

vim +2442 include/net/sock.h

  2430	
  2431	/**
  2432	 * sk_eat_skb - Release a skb if it is no longer needed
  2433	 * @sk: socket to eat this skb from
  2434	 * @skb: socket buffer to eat
  2435	 *
  2436	 * This routine must be called with interrupts disabled or with the socket
  2437	 * locked so that the sk_buff queue operation is ok.
  2438	*/
  2439	static inline void sk_eat_skb(struct sock *sk, struct sk_buff *skb)
  2440	{
  2441		__skb_unlink(skb, &sk->sk_receive_queue);
> 2442		if (!static_branch_unlikely(&rps_needed) && !sk->sk_rx_skb_cache) {
  2443			sk->sk_rx_skb_cache = skb;
  2444			skb_orphan(skb);
  2445			return;
  2446		}
  2447		__kfree_skb(skb);
  2448	}
  2449	

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