1. 07 10月, 2010 4 次提交
  2. 06 10月, 2010 13 次提交
  3. 05 10月, 2010 22 次提交
  4. 04 10月, 2010 1 次提交
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      net: introduce DST_NOCACHE flag · c7d4426a
      Eric Dumazet 提交于
      While doing stress tests with IP route cache disabled, and multi queue
      devices, I noticed a very high contention on one rwlock used in
      neighbour code.
      
      When many cpus are trying to send frames (possibly using a high
      performance multiqueue device) to the same neighbour, they fight for the
      neigh->lock rwlock in order to call neigh_hh_init(), and fight on
      hh->hh_refcnt (a pair of atomic_inc/atomic_dec_and_test())
      
      But we dont need to call neigh_hh_init() for dst that are used only
      once. It costs four atomic operations at least, on two contended cache
      lines, plus the high contention on neigh->lock rwlock.
      
      Introduce a new dst flag, DST_NOCACHE, that is set when dst was not
      inserted in route cache.
      
      With the stress test bench, sending 160000000 frames on one neighbour,
      results are :
      
      Before patch:
      
      real	2m28.406s
      user	0m11.781s
      sys	36m17.964s
      
      
      After patch:
      
      real	1m26.532s
      user	0m12.185s
      sys	20m3.903s
      Signed-off-by: NEric Dumazet <eric.dumazet@gmail.com>
      Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      c7d4426a