1. 28 Oct, 2008 1 commit
    • Neil Horman's avatar
      net: implement emergency route cache rebulds when gc_elasticity is exceeded · 1080d709
      Neil Horman authored
      This is a patch to provide on demand route cache rebuilding.  Currently, our
      route cache is rebulid periodically regardless of need.  This introduced
      unneeded periodic latency.  This patch offers a better approach.  Using code
      provided by Eric Dumazet, we compute the standard deviation of the average hash
      bucket chain length while running rt_check_expire.  Should any given chain
      length grow to larger that average plus 4 standard deviations, we trigger an
      emergency hash table rebuild for that net namespace.  This allows for the common
      case in which chains are well behaved and do not grow unevenly to not incur any
      latency at all, while those systems (which may be being maliciously attacked),
      only rebuild when the attack is detected.  This patch take 2 other factors into
      account:
      1) chains with multiple entries that differ by attributes that do not affect the
      hash value are only counted once, so as not to unduly bias system to rebuilding
      if features like QOS are heavily used
      2) if rebuilding crosses a certain threshold (which is adjustable via the added
      sysctl in this patch), route caching is disabled entirely for that net
      namespace, since constant rebuilding is less efficient that no caching at all
      
      Tested successfully by me.
      Signed-off-by: default avatarNeil Horman <nhorman@tuxdriver.com>
      Signed-off-by: default avatarEric Dumazet <dada1@cosmosbay.com>
      Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
      1080d709
  2. 27 Oct, 2008 15 commits
  3. 26 Oct, 2008 24 commits