cvs commit: src/sys/amd64/amd64 pmap.c

Alan Cox alc at
Thu Jun 12 05:18:20 UTC 2008

alc         2008-06-12 05:18:09 UTC

  FreeBSD src repository

  Modified files:
    sys/amd64/amd64      pmap.c 
  SVN rev 179749 on 2008-06-12 05:18:09Z by alc
  Reverse the direction of pmap_promote_pde()'s traversal over the specified
  page table page.  The direction of the traversal can matter if
  pmap_promote_pde() has to remove write access (PG_RW) from a PTE that hasn't
  been modified (PG_M).  In general, if there are two or more such PTEs to
  choose among, it is better to write protect the one nearer the high end of
  the page table page rather than the low end.  This is because most programs
  access memory in an ascending direction.  The net result of this change is a
  sometimes significant reduction in the number of failed promotion attempts
  and the number of pages that are write protected by pmap_promote_pde().
  Revision  Changes    Path
  1.620     +28 -12    src/sys/amd64/amd64/pmap.c

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