1. 28 4月, 2009 1 次提交
    • E
      net: Avoid extra wakeups of threads blocked in wait_for_packet() · bf368e4e
      Eric Dumazet 提交于
      In 2.6.25 we added UDP mem accounting.
      
      This unfortunatly added a penalty when a frame is transmitted, since
      we have at TX completion time to call sock_wfree() to perform necessary
      memory accounting. This calls sock_def_write_space() and utimately
      scheduler if any thread is waiting on the socket.
      Thread(s) waiting for an incoming frame was scheduled, then had to sleep
      again as event was meaningless.
      
      (All threads waiting on a socket are using same sk_sleep anchor)
      
      This adds lot of extra wakeups and increases latencies, as noted
      by Christoph Lameter, and slows down softirq handler.
      
      Reference : http://marc.info/?l=linux-netdev&m=124060437012283&w=2 
      
      Fortunatly, Davide Libenzi recently added concept of keyed wakeups
      into kernel, and particularly for sockets (see commit
      37e5540b 
      epoll keyed wakeups: make sockets use keyed wakeups)
      
      Davide goal was to optimize epoll, but this new wakeup infrastructure
      can help non epoll users as well, if they care to setup an appropriate
      handler.
      
      This patch introduces new DEFINE_WAIT_FUNC() helper and uses it
      in wait_for_packet(), so that only relevant event can wakeup a thread
      blocked in this function.
      
      Trace of function calls from bnx2 TX completion bnx2_poll_work() is :
      __kfree_skb()
       skb_release_head_state()
        sock_wfree()
         sock_def_write_space()
          __wake_up_sync_key()
           __wake_up_common()
            receiver_wake_function() : Stops here since thread is waiting for an INPUT
      Reported-by: NChristoph Lameter <cl@linux.com>
      Signed-off-by: NEric Dumazet <dada1@cosmosbay.com>
      Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      bf368e4e
  2. 27 4月, 2009 12 次提交
  3. 26 4月, 2009 2 次提交
  4. 24 4月, 2009 4 次提交
  5. 22 4月, 2009 17 次提交
  6. 21 4月, 2009 4 次提交