• Thomas Graf's avatar
    netlink: Convert netlink_lookup() to use RCU protected hash table · e341694e
    Thomas Graf authored
    Heavy Netlink users such as Open vSwitch spend a considerable amount of
    time in netlink_lookup() due to the read-lock on nl_table_lock. Use of
    RCU relieves the lock contention.
    
    Makes use of the new resizable hash table to avoid locking on the
    lookup.
    
    The hash table will grow if entries exceeds 75% of table size up to a
    total table size of 64K. It will automatically shrink if usage falls
    below 30%.
    
    Also splits nl_table_lock into a separate mutex to protect hash table
    mutations and allow synchronize_rcu() to sleep while waiting for readers
    during expansion and shrinking.
    
    Before:
       9.16%  kpktgend_0  [openvswitch]      [k] masked_flow_lookup
       6.42%  kpktgend_0  [pktgen]           [k] mod_cur_headers
       6.26%  kpktgend_0  [pktgen]           [k] pktgen_thread_worker
       6.23%  kpktgend_0  [kernel.kallsyms]  [k] memset
       4.79%  kpktgend_0  [kernel.kallsyms]  [k] netlink_lookup
       4.37%  kpktgend_0  [kernel.kallsyms]  [k] memcpy
       3.60%  kpktgend_0  [openvswitch]      [k] ovs_flow_extract
       2.69%  kpktgend_0  [kernel.kallsyms]  [k] jhash2
    
    After:
      15.26%  kpktgend_0  [openvswitch]      [k] masked_flow_lookup
       8.12%  kpktgend_0  [pktgen]           [k] pktgen_thread_worker
       7.92%  kpktgend_0  [pktgen]           [k] mod_cur_headers
       5.11%  kpktgend_0  [kernel.kallsyms]  [k] memset
       4.11%  kpktgend_0  [openvswitch]      [k] ovs_flow_extract
       4.06%  kpktgend_0  [kernel.kallsyms]  [k] _raw_spin_lock
       3.90%  kpktgend_0  [kernel.kallsyms]  [k] jhash2
       [...]
       0.67%  kpktgend_0  [kernel.kallsyms]  [k] netlink_lookup
    Signed-off-by: default avatarThomas Graf <tgraf@suug.ch>
    Reviewed-by: default avatarNikolay Aleksandrov <nikolay@redhat.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    e341694e
diag.c 5.1 KB