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    • David S. Miller's avatar
    • David S. Miller's avatar
    • David S. Miller's avatar
      Merge branch 'fib_trie-next' · e495f78d
      David S. Miller authored
      Alexander Duyck says:
      
      ====================
      fib_trie: Reduce time spent in fib_table_lookup by 35 to 75%
      
      These patches are meant to address several performance issues I have seen
      in the fib_trie implementation, and fib_table_lookup specifically.  With
      these changes in place I have seen a reduction of up to 35 to 75% for the
      total time spent in fib_table_lookup depending on the type of search being
      performed.
      
      On a VM running in my Corei7-4930K system with a trie of maximum depth of 7
      this resulted in a reduction of over 370ns per packet in the total time to
      process packets received from an ixgbe interface and route them to a dummy
      interface.  This represents a failed lookup in the local trie followed by
      a successful search in the main trie.
      
      				Baseline	Refactor
        ixgbe->dummy routing		1.20Mpps	2.21Mpps
        ------------------------------------------------------------
        processing time per packet		835ns		453ns
        fib_table_lookup		50.1%	418ns	25.0%	113ns
        check_leaf.isra.9		 7.9%	 66ns	   --	 --
        ixgbe_clean_rx_irq		 5.3%	 44ns	 9.8%	 44ns
        ip_route_input_noref		 2.9%	 25ns	 4.6%	 21ns
        pvclock_clocksource_read	 2.6%	 21ns	 4.6%	 21ns
        ip_rcv			 2.6%	 22ns	 4.0%	 18ns
      
      In the simple case of receiving a frame and dropping it before it can reach
      the socket layer I saw a reduction of 40ns per packet.  This represents a
      trip through the local trie with the correct leaf found with no need for
      any backtracing.
      
      				Baseline	Refactor
        ixgbe->local receive		2.65Mpps	2.96Mpps
        ------------------------------------------------------------
        processing time per packet		377ns		337ns
        fib_table_lookup		25.1%	 95ns	25.8%	 87ns
        ixgbe_clean_rx_irq		 8.7%	 33ns	 9.0%	 30ns
        check_leaf.isra.9		 7.2%	 27ns	   --	 --
        ip_rcv			 5.7%	 21ns	 6.5%	 22ns
      
      These changes have resulted in several functions being inlined such as
      check_leaf and fib_find_node, but due to the code simplification the
      overall size of the code has been reduced.
      
         text	   data	    bss	    dec	    hex	filename
        16932	    376	     16	  17324	   43ac	net/ipv4/fib_trie.o - before
        15259	    376	      8	  15643	   3d1b	net/ipv4/fib_trie.o - after
      
      Changes since RFC:
        Replaced this_cpu_ptr with correct call to this_cpu_inc in patch 1
        Changed test for leaf_info mismatch to (key ^ n->key) & li->mask_plen in patch 10
      ====================
      Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
      e495f78d