1. 11 Jul, 2012 17 commits
  2. 09 Jul, 2012 21 commits
  3. 07 Jul, 2012 2 commits
    • David S. Miller's avatar
    • Eric Dumazet's avatar
      asix: avoid copies in tx path · 95162d65
      Eric Dumazet authored
      I noticed excess calls to skb_copy_expand() or memmove() in asix driver.
      
      This driver needs to push 4 bytes in front of frame (packet_len)
      and maybe add 4 bytes after the end (if padlen is 4)
      
      So it should set needed_headroom & needed_tailroom to avoid
      copies. But its not enough, because many packets are cloned
      before entering asix_tx_fixup() and this driver use skb_cloned()
      as a lazy way to check if it can push and put additional bytes in frame.
      
      Avoid skb_copy_expand() expensive call, using following rules :
      
      - We are allowed to push 4 bytes in headroom if skb_header_cloned()
        is false (and if we have 4 bytes of headroom)
      
      - We are allowed to put 4 bytes at tail if skb_cloned()
        is false (and if we have 4 bytes of tailroom)
      
      TCP packets for example are cloned, but skb_header_release()
      was called in tcp stack, allowing us to use headroom for our needs.
      Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
      Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
      Cc: Allan Chou <allan@asix.com.tw>
      Cc: Trond Wuellner <trond@chromium.org>
      Cc: Grant Grundler <grundler@chromium.org>
      Cc: Paul Stewart <pstew@chromium.org>
      Cc: Ming Lei <tom.leiming@gmail.com>
      Tested-by: default avatarMing Lei <ming.lei@canonical.com>
      Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
      95162d65