1. 21 10月, 2010 39 次提交
  2. 20 10月, 2010 1 次提交
    • E
      net: avoid RCU for NOCACHE dst · 27b75c95
      Eric Dumazet 提交于
      There is no point using RCU for dst we allocate for a very short time
      (used once).
      
      Change dst_release() to take DST_NOCACHE into account, but also change
      skb_dst_set_noref() to force a refcount increment for such dst.
      
      This is a _huge_ gain, because we dont waste memory to store xx thousand
      of dsts. Instead of queueing them to RCU, we can free them instantly.
      
      CPU caches can stay hot, re-using same memory blocks to hold temporary
      dsts.
      
      Note : remove unneeded smp_mb__before_atomic_dec(); in dst_release(),
      since atomic_dec_return() implies a full memory barrier.
      
      Stress test, 160.000.000 udp frames sent, IP route cache disabled
      (DDOS).
      
      Before:
      
      real    0m38.091s
      user    0m13.189s
      sys     7m53.018s
      
      After:
      
      real	0m29.946s
      user	0m12.157s
      sys	7m40.605s
      
      For reference, if IP route cache was enabled :
      
      real	0m32.030s
      user	0m10.521s
      sys	8m15.243s
      Signed-off-by: NEric Dumazet <eric.dumazet@gmail.com>
      Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      27b75c95