Simplify the implementation of pmap_emulate_reference(). The new version

simply manipulates the pte which faulted instead of traversing the mapping
list for that page. This makes it possible to complete the trap without
needing locks and incidentally improves the accuracy of some statistics
used by the VM system.

3 files changed, 76 insertions, 59 deletions

diff --git a/sys/alpha/alpha/pmap.c b/sys/alpha/alpha/pmap.c
index 4eb0c36..43f65e3 100644
--- a/sys/alpha/alpha/pmap.c
+++ b/sys/alpha/alpha/pmap.c
@@ -1189,7 +1189,6 @@ pmap_pinit0(pmap)
 	int i;
 
 	pmap->pm_lev1 = Lev1map;
-	pmap->pm_flags = 0;
 	pmap->pm_count = 1;
 	pmap->pm_ptphint = NULL;
 	pmap->pm_active = 0;
@@ -1239,7 +1238,6 @@ pmap_pinit(pmap)
 	pmap->pm_lev1[PTLEV1I] = pmap_phys_to_pte(VM_PAGE_TO_PHYS(lev1pg))
 		| PG_V | PG_KRE | PG_KWE;
 
-	pmap->pm_flags = 0;
 	pmap->pm_count = 1;
 	pmap->pm_ptphint = NULL;
 	pmap->pm_active = 0;
@@ -2107,16 +2105,10 @@ validate:
 	newpte = pmap_phys_to_pte(pa) | pte_prot(pmap, prot) | PG_V | managed;
 
 	if (managed) {
-		vm_page_t om;
-
 		/*
 		 * Set up referenced/modified emulation for the new mapping
 		 */
-		om = PHYS_TO_VM_PAGE(pa);
-		if ((om->md.pv_flags & PV_TABLE_REF) == 0)
-			newpte |= PG_FOR | PG_FOW | PG_FOE;
-		else if ((om->md.pv_flags & PV_TABLE_MOD) == 0)
-			newpte |= PG_FOW;
+		newpte |= origpte & (PG_FOR | PG_FOW | PG_FOE);
 	}
 
 	if (wired)
@@ -2745,16 +2737,32 @@ pmap_phys_address(ppn)
 int
 pmap_ts_referenced(vm_page_t m)
 {
+	pv_entry_t pv;
+	pt_entry_t *pte;
+	int count;
+
 	if (!pmap_initialized || (m->flags & PG_FICTITIOUS))
 		return 0;
 
-	if (m->md.pv_flags & PV_TABLE_REF) {
-		pmap_changebit(m, PG_FOR|PG_FOE|PG_FOW, TRUE);
-		m->md.pv_flags &= ~PV_TABLE_REF;
-		return 1;
+	/*
+	 * Loop over current mappings looking for any which have don't
+	 * have PG_FOR set (i.e. ones where we have taken an emulate
+	 * reference trap recently).
+	 */
+	count = 0;
+	for (pv = TAILQ_FIRST(&m->md.pv_list);
+	     pv;
+	     pv = TAILQ_NEXT(pv, pv_list)) {
+		pte = pmap_lev3pte(pv->pv_pmap, pv->pv_va);
+		
+		if (!(*pte & PG_FOR)) {
+			count++;
+			*pte |= PG_FOR | PG_FOE;
+			pmap_invalidate_page(pv->pv_pmap, pv->pv_va);
+		}
 	}
 
-	return 0;
+	return count;
 }
 
 /*
@@ -2766,11 +2774,25 @@ pmap_ts_referenced(vm_page_t m)
 boolean_t
 pmap_is_modified(vm_page_t m)
 {
+	pv_entry_t pv;
+	pt_entry_t *pte;
 
 	if (!pmap_initialized || (m->flags & PG_FICTITIOUS))
 		return FALSE;
 
-	return (m->md.pv_flags & PV_TABLE_MOD) != 0;
+	/*
+	 * A page is modified if any mapping has had its PG_FOW flag
+	 * cleared.
+	 */
+	for (pv = TAILQ_FIRST(&m->md.pv_list);
+	     pv;
+	     pv = TAILQ_NEXT(pv, pv_list)) {
+		pte = pmap_lev3pte(pv->pv_pmap, pv->pv_va);
+		if (!(*pte & PG_FOW))
+			return 1;
+	}
+
+	return 0;
 }
 
 /*
@@ -2779,12 +2801,24 @@ pmap_is_modified(vm_page_t m)
 void
 pmap_clear_modify(vm_page_t m)
 {
+	pv_entry_t pv;
+	pt_entry_t *pte;
+
 	if (!pmap_initialized || (m->flags & PG_FICTITIOUS))
 		return;
 
-	if (m->md.pv_flags & PV_TABLE_MOD) {
-		pmap_changebit(m, PG_FOW, TRUE);
-		m->md.pv_flags &= ~PV_TABLE_MOD;
+	/*
+	 * Loop over current mappings setting PG_FOW where needed.
+	 */
+	for (pv = TAILQ_FIRST(&m->md.pv_list);
+	     pv;
+	     pv = TAILQ_NEXT(pv, pv_list)) {
+		pte = pmap_lev3pte(pv->pv_pmap, pv->pv_va);
+		
+		if (!(*pte & PG_FOW)) {
+			*pte |= PG_FOW;
+			pmap_invalidate_page(pv->pv_pmap, pv->pv_va);
+		}
 	}
 }
 
@@ -2809,12 +2843,24 @@ pmap_page_is_free(vm_page_t m)
 void
 pmap_clear_reference(vm_page_t m)
 {
+	pv_entry_t pv;
+	pt_entry_t *pte;
+
 	if (!pmap_initialized || (m->flags & PG_FICTITIOUS))
 		return;
 
-	if (m->md.pv_flags & PV_TABLE_REF) {
-		pmap_changebit(m, PG_FOR|PG_FOE|PG_FOW, TRUE);
-		m->md.pv_flags &= ~PV_TABLE_REF;
+	/*
+	 * Loop over current mappings setting PG_FOR and PG_FOE where needed.
+	 */
+	for (pv = TAILQ_FIRST(&m->md.pv_list);
+	     pv;
+	     pv = TAILQ_NEXT(pv, pv_list)) {
+		pte = pmap_lev3pte(pv->pv_pmap, pv->pv_va);
+		
+		if (!(*pte & (PG_FOR | PG_FOE))) {
+			*pte |= (PG_FOR | PG_FOE);
+			pmap_invalidate_page(pv->pv_pmap, pv->pv_va);
+		}
 	}
 }
 
@@ -2829,7 +2875,6 @@ pmap_emulate_reference(struct proc *p, vm_offset_t v, int user, int write)
 {
 	pt_entry_t faultoff, *pte;
 	vm_offset_t pa;
-	vm_page_t m;
 	int user_addr;
 
 	/*
@@ -2883,36 +2928,14 @@ pmap_emulate_reference(struct proc *p, vm_offset_t v, int user, int write)
 	 * 	(1) always mark page as used, and
 	 *	(2) if it was a write fault, mark page as modified.
 	 */
-	m = PHYS_TO_VM_PAGE(pa);
-	m->md.pv_flags |= PV_TABLE_REF;
-	faultoff = PG_FOR | PG_FOE;
-
-	if (user_addr) {
-		mtx_lock(&Giant);
-		vm_page_flag_set(m, PG_REFERENCED);
-		mtx_unlock(&Giant);
-	}
-
 	if (write) {
-		m->md.pv_flags |= PV_TABLE_MOD;
-		vm_page_dirty(m);
-		faultoff |= PG_FOW;
-	}
-	pmap_changebit(m, faultoff, FALSE);
-	if ((*pte & faultoff) != 0) {
-#if 1
-		/*
-		 * XXX dfr - don't think its possible in our pmap
-		 */
-		/*
-		 * This is apparently normal.  Why? -- cgd
-		 * XXX because was being called on unmanaged pages?
-		 */
-		panic("warning: pmap_changebit didn't.");
-#endif
-		*pte &= ~faultoff;
-		ALPHA_TBIS(v);
+		faultoff = PG_FOR | PG_FOE | PG_FOW;
+	} else {
+		faultoff = PG_FOR | PG_FOE;
 	}
+
+	*pte = (*pte & ~faultoff);
+	ALPHA_TBIS(v);
 }
 
 /*
@@ -2975,7 +2998,6 @@ pmap_mincore(pmap, addr)
 	pmap_t pmap;
 	vm_offset_t addr;
 {
-	
 	pt_entry_t *pte;
 	int val = 0;
 	
@@ -2999,7 +3021,7 @@ pmap_mincore(pmap, addr)
 		/*
 		 * Modified by us
 		 */
-		if (m->md.pv_flags & PV_TABLE_MOD)
+		if ((*pte & PG_FOW) == 0)
 			val |= MINCORE_MODIFIED|MINCORE_MODIFIED_OTHER;
 		/*
 		 * Modified by someone
@@ -3009,7 +3031,7 @@ pmap_mincore(pmap, addr)
 		/*
 		 * Referenced by us
 		 */
-		if (m->md.pv_flags & PV_TABLE_REF)
+		if ((*pte & (PG_FOR | PG_FOE)) == 0)
 			val |= MINCORE_REFERENCED|MINCORE_REFERENCED_OTHER;
 
 		/*
diff --git a/sys/alpha/alpha/trap.c b/sys/alpha/alpha/trap.c
index 27ca15c..2fdb2a2 100644
--- a/sys/alpha/alpha/trap.c
+++ b/sys/alpha/alpha/trap.c
@@ -434,11 +434,10 @@ trap(a0, a1, a2, entry, framep)
 		case ALPHA_MMCSR_FOR:
 		case ALPHA_MMCSR_FOE:
 		case ALPHA_MMCSR_FOW:
-		{
 			pmap_emulate_reference(p, a0, user,
 			    a1 == ALPHA_MMCSR_FOW);
 			goto out;
-		}
+
 		case ALPHA_MMCSR_INVALTRANS:
 		case ALPHA_MMCSR_ACCESS:
 	    	{
diff --git a/sys/alpha/include/pmap.h b/sys/alpha/include/pmap.h
index 886627c..055ea36 100644
--- a/sys/alpha/include/pmap.h
+++ b/sys/alpha/include/pmap.h
@@ -165,15 +165,11 @@ struct md_page {
 	TAILQ_HEAD(,pv_entry)	pv_list;
 };
 
-#define PV_TABLE_MOD		0x01 /* modified */
-#define PV_TABLE_REF		0x02 /* referenced */
-
 struct pmap {
 	pt_entry_t		*pm_lev1;	/* KVA of lev0map */
 	vm_object_t		pm_pteobj;	/* Container for pte's */
 	TAILQ_HEAD(,pv_entry)	pm_pvlist;	/* list of mappings in pmap */
 	int			pm_count;	/* reference count */
-	int			pm_flags;	/* pmap flags */
 	u_int32_t		pm_active;	/* active cpus */
 	struct {
 		u_int32_t	asn:8;		/* address space number */