1. 02 Mar, 2009 1 commit
    • Jeremy Fitzhardinge's avatar
      x86-32: use non-lazy io bitmap context switching · db949bba
      Jeremy Fitzhardinge authored
      Impact: remove 32-bit optimization to prepare unification
      
      x86-32 and -64 differ in the way they context-switch tasks
      with io permission bitmaps.  x86-64 simply copies the next
      tasks io bitmap into place (if any) on context switch.  x86-32
      invalidates the bitmap on context switch, so that the next
      IO instruction will fault; at that point it installs the
      appropriate IO bitmap.
      
      This makes context switching IO-bitmap-using tasks a bit more
      less expensive, at the cost of making the next IO instruction
      slower due to the extra fault.  This tradeoff only makes sense
      if IO-bitmap-using processes are relatively common, but they
      don't actually use IO instructions very often.
      
      However, in a typical desktop system, the only process likely
      to be using IO bitmaps is the X server, and nothing at all on
      a server.  Therefore the lazy context switch doesn't really win
      all that much, and its just a gratuitious difference from
      64-bit code.
      
      This patch removes the lazy context switch, with a view to
      unifying this code in a later change.
      Signed-off-by: default avatarJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
      Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      db949bba
  2. 01 Mar, 2009 3 commits
  3. 28 Feb, 2009 23 commits
  4. 27 Feb, 2009 13 commits