Resurrect pmap_is_referenced() and use it in mincore(). Essentially,

pmap_ts_referenced() is not always appropriate for checking whether or
not pages have been referenced because it clears any reference bits
that it encounters.  For example, in mincore(), clearing the reference
bits has two negative consequences.  First, it throws off the activity
count calculations performed by the page daemon.  Specifically, a page
on which mincore() has called pmap_ts_referenced() looks less active
to the page daemon than it should.  Consequently, the page could be
deactivated prematurely by the page daemon.  Arguably, this problem
could be fixed by having mincore() duplicate the activity count
calculation on the page.  However, there is a second problem for which
that is not a solution.  In order to clear a reference on a 4KB page,
it may be necessary to demote a 2/4MB page mapping.  Thus, a mincore()
by one process can have the side effect of demoting a superpage
mapping within another process!

1 files changed, 1 insertions, 0 deletions

diff --git a/sys/vm/pmap.h b/sys/vm/pmap.h
index 51a3bbe..e4d8e81 100644
--- a/sys/vm/pmap.h
+++ b/sys/vm/pmap.h
@@ -119,6 +119,7 @@ void		 pmap_growkernel(vm_offset_t);
 void		 pmap_init(void);
 boolean_t	 pmap_is_modified(vm_page_t m);
 boolean_t	 pmap_is_prefaultable(pmap_t pmap, vm_offset_t va);
+boolean_t	 pmap_is_referenced(vm_page_t m);
 boolean_t	 pmap_ts_referenced(vm_page_t m);
 vm_offset_t	 pmap_map(vm_offset_t *, vm_paddr_t, vm_paddr_t, int);
 void		 pmap_object_init_pt(pmap_t pmap, vm_offset_t addr,