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0197aa38df
ip_route_output_slow() is enclosed in an rcu_read_lock() protected section, so that no references are taken/released on device, thanks to __ip_dev_find() & dev_get_by_index_rcu() Tested with ip route cache disabled, and a stress test : Before patch: elapsed time : real 1m38.347s user 0m11.909s sys 23m51.501s Profile: 13788.00 22.7% ip_route_output_slow [kernel] 7875.00 13.0% dst_destroy [kernel] 3925.00 6.5% fib_semantic_match [kernel] 3144.00 5.2% fib_rules_lookup [kernel] 3061.00 5.0% dst_alloc [kernel] 2276.00 3.7% rt_set_nexthop [kernel] 1762.00 2.9% fib_table_lookup [kernel] 1538.00 2.5% _raw_read_lock [kernel] 1358.00 2.2% ip_output [kernel] After patch: real 1m28.808s user 0m13.245s sys 20m37.293s 10950.00 17.2% ip_route_output_slow [kernel] 10726.00 16.9% dst_destroy [kernel] 5170.00 8.1% fib_semantic_match [kernel] 3937.00 6.2% dst_alloc [kernel] 3635.00 5.7% rt_set_nexthop [kernel] 2900.00 4.6% fib_rules_lookup [kernel] 2240.00 3.5% fib_table_lookup [kernel] 1427.00 2.2% _raw_read_lock [kernel] 1157.00 1.8% kmem_cache_alloc [kernel] Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>