Make several changes to pmap_enter_quick_locked():

1. Make the caller responsible for performing pmap_install().  This reduces
the number of times that pmap_install() is performed by
pmap_enter_object() from twice per page to twice overall.

2. Don't block if pmap_find_pte() is unable to allocate a PTE.  If it did
block, then it might wind up mapping a cache page.  Specifically, if
pmap_enter_quick_locked() slept when called from pmap_enter_object(), the
page daemon could change an active or inactive page into a cache page just
before it was to be mapped.

3. Bail out of pmap_enter_quick_locked() if pv entries aren't plentiful.
In other words, don't force the allocation of a pv entry if they aren't
readily available.

Reviewed by: marcel@

1 files changed, 39 insertions, 20 deletions

diff --git a/sys/ia64/ia64/pmap.c b/sys/ia64/ia64/pmap.c
index 155b0c7..18d9644 100644
--- a/sys/ia64/ia64/pmap.c
+++ b/sys/ia64/ia64/pmap.c
@@ -242,6 +242,8 @@ static pmap_t	pmap_install(pmap_t);
 static void	pmap_invalidate_all(pmap_t pmap);
 static int	pmap_remove_pte(pmap_t pmap, struct ia64_lpte *pte,
 		    vm_offset_t va, pv_entry_t pv, int freepte);
+static boolean_t pmap_try_insert_pv_entry(pmap_t pmap, vm_offset_t va,
+		    vm_page_t m);
 
 vm_offset_t
 pmap_steal_memory(vm_size_t size)
@@ -863,6 +865,29 @@ retry:
 }
 
 /*
+ * Conditionally create a pv entry.
+ */
+static boolean_t
+pmap_try_insert_pv_entry(pmap_t pmap, vm_offset_t va, vm_page_t m)
+{
+	pv_entry_t pv;
+
+	PMAP_LOCK_ASSERT(pmap, MA_OWNED);
+	mtx_assert(&vm_page_queue_mtx, MA_OWNED);
+	if (pv_entry_count < pv_entry_high_water && 
+	    (pv = uma_zalloc(pvzone, M_NOWAIT)) != NULL) {
+		pv_entry_count++;
+		pv->pv_va = va;
+		pv->pv_pmap = pmap;
+		TAILQ_INSERT_TAIL(&pmap->pm_pvlist, pv, pv_plist);
+		TAILQ_INSERT_TAIL(&m->md.pv_list, pv, pv_list);
+		m->md.pv_list_count++;
+		return (TRUE);
+	} else
+		return (FALSE);
+}
+
+/*
  * Add an ia64_lpte to the VHPT.
  */
 static void
@@ -1643,16 +1668,20 @@ void
 pmap_enter_object(pmap_t pmap, vm_offset_t start, vm_offset_t end,
     vm_page_t m_start, vm_prot_t prot)
 {
+	pmap_t oldpmap;
 	vm_page_t m;
 	vm_pindex_t diff, psize;
 
+	VM_OBJECT_LOCK_ASSERT(m_start->object, MA_OWNED);
 	psize = atop(end - start);
 	m = m_start;
 	PMAP_LOCK(pmap);
+	oldpmap = pmap_install(pmap);
 	while (m != NULL && (diff = m->pindex - m_start->pindex) < psize) {
 		pmap_enter_quick_locked(pmap, start + ptoa(diff), m, prot);
 		m = TAILQ_NEXT(m, listq);
 	}
+	pmap_install(oldpmap);
  	PMAP_UNLOCK(pmap);
 }
 
@@ -1668,9 +1697,12 @@ pmap_enter_object(pmap_t pmap, vm_offset_t start, vm_offset_t end,
 void
 pmap_enter_quick(pmap_t pmap, vm_offset_t va, vm_page_t m, vm_prot_t prot)
 {
+	pmap_t oldpmap;
 
 	PMAP_LOCK(pmap);
+	oldpmap = pmap_install(pmap);
 	pmap_enter_quick_locked(pmap, va, m, prot);
+	pmap_install(oldpmap);
 	PMAP_UNLOCK(pmap);
 }
 
@@ -1679,35 +1711,24 @@ pmap_enter_quick_locked(pmap_t pmap, vm_offset_t va, vm_page_t m,
     vm_prot_t prot)
 {
 	struct ia64_lpte *pte;
-	pmap_t oldpmap;
 	boolean_t managed;
 
 	KASSERT(va < kmi.clean_sva || va >= kmi.clean_eva ||
 	    (m->flags & (PG_FICTITIOUS | PG_UNMANAGED)) != 0,
 	    ("pmap_enter_quick_locked: managed mapping within the clean submap"));
 	mtx_assert(&vm_page_queue_mtx, MA_OWNED);
-	VM_OBJECT_LOCK_ASSERT(m->object, MA_OWNED);
 	PMAP_LOCK_ASSERT(pmap, MA_OWNED);
-	oldpmap = pmap_install(pmap);
 
-	while ((pte = pmap_find_pte(va)) == NULL) {
-		pmap_install(oldpmap);
-		PMAP_UNLOCK(pmap);
-		vm_page_busy(m);
-		vm_page_unlock_queues();
-		VM_OBJECT_UNLOCK(m->object);
-		VM_WAIT;
-		VM_OBJECT_LOCK(m->object);
-		vm_page_lock_queues();
-		vm_page_wakeup(m);
-		PMAP_LOCK(pmap);
-		oldpmap = pmap_install(pmap);
-	}
+	if ((pte = pmap_find_pte(va)) == NULL)
+		return;
 
 	if (!pmap_present(pte)) {
-		/* Enter on the PV list if its managed. */
+		/* Enter on the PV list if the page is managed. */
 		if ((m->flags & (PG_FICTITIOUS | PG_UNMANAGED)) == 0) {
-			pmap_insert_entry(pmap, va, m);
+			if (!pmap_try_insert_pv_entry(pmap, va, m)) {
+				pmap_free_pte(pte, va);
+				return;
+			}
 			managed = TRUE;
 		} else
 			managed = FALSE;
@@ -1721,8 +1742,6 @@ pmap_enter_quick_locked(pmap_t pmap, vm_offset_t va, vm_page_t m,
 		    prot & (VM_PROT_READ | VM_PROT_EXECUTE));
 		pmap_set_pte(pte, va, VM_PAGE_TO_PHYS(m), FALSE, managed);
 	}
-
-	pmap_install(oldpmap);
 }
 
 /*