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, 11 insertions, 0 deletions

diff --git a/sys/powerpc/aim/mmu_oea.c b/sys/powerpc/aim/mmu_oea.c
index 8357929..24e7b4e 100644
--- a/sys/powerpc/aim/mmu_oea.c
+++ b/sys/powerpc/aim/mmu_oea.c
@@ -305,6 +305,7 @@ vm_paddr_t moea_extract(mmu_t, pmap_t, vm_offset_t);
 vm_page_t moea_extract_and_hold(mmu_t, pmap_t, vm_offset_t, vm_prot_t);
 void moea_init(mmu_t);
 boolean_t moea_is_modified(mmu_t, vm_page_t);
+boolean_t moea_is_referenced(mmu_t, vm_page_t);
 boolean_t moea_ts_referenced(mmu_t, vm_page_t);
 vm_offset_t moea_map(mmu_t, vm_offset_t *, vm_offset_t, vm_offset_t, int);
 boolean_t moea_page_exists_quick(mmu_t, pmap_t, vm_page_t);
@@ -344,6 +345,7 @@ static mmu_method_t moea_methods[] = {
 	MMUMETHOD(mmu_extract_and_hold,	moea_extract_and_hold),
 	MMUMETHOD(mmu_init,		moea_init),
 	MMUMETHOD(mmu_is_modified,	moea_is_modified),
+	MMUMETHOD(mmu_is_referenced,	moea_is_referenced),
 	MMUMETHOD(mmu_ts_referenced,	moea_ts_referenced),
 	MMUMETHOD(mmu_map,     		moea_map),
 	MMUMETHOD(mmu_page_exists_quick,moea_page_exists_quick),
@@ -1269,6 +1271,15 @@ moea_init(mmu_t mmu)
 }
 
 boolean_t
+moea_is_referenced(mmu_t mmu, vm_page_t m)
+{
+
+	if ((m->flags & (PG_FICTITIOUS | PG_UNMANAGED)) != 0)
+		return (FALSE);
+	return (moea_query_bit(m, PTE_REF));
+}
+
+boolean_t
 moea_is_modified(mmu_t mmu, vm_page_t m)
 {