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From: Alan Cox <alc@FreeBSD.org>
Date: Sun, 25 Apr 2010 20:40:45 +0000 (UTC)
To: cvs-src-old@freebsd.org
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Subject: cvs commit: src/sys/amd64/amd64 pmap.c src/sys/i386/i386 pmap.c
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alc         2010-04-25 20:40:45 UTC

  FreeBSD src repository

  Modified files:
    sys/amd64/amd64      pmap.c 
    sys/i386/i386        pmap.c 
  Log:
  SVN rev 207205 on 2010-04-25 20:40:45Z by alc
  
  Clearing a page table entry's accessed bit (PG_A) and setting the
  page's PG_REFERENCED flag in pmap_protect() can't really be justified.
  In contrast to pmap_remove() or pmap_remove_all(), the mapping is not
  being destroyed, so the notion that the page was accessed is not lost.
  Moreover, clearing the page table entry's accessed bit and setting the
  page's PG_REFERENCED flag can throw off the page daemon's activity
  count calculation.  Finally, in my tests, I found that 15% of the
  atomic memory operations being performed by pmap_protect() were only
  to clear PG_A, and not change protection.  This could, by itself, be
  fixed, but I don't see the point given the above argument.
  
  Remove a comment from pmap_protect_pde() that is no longer meaningful
  after the above change.
  
  Revision  Changes    Path
  1.691     +6 -23     src/sys/amd64/amd64/pmap.c
  1.673     +6 -22     src/sys/i386/i386/pmap.c