Index: vm_page.c
===================================================================
--- vm_page.c
+++ vm_page.c
@@ -833,7 +833,7 @@
 
 			vmd = VM_DOMAIN(seg->domain);
 			vm_domain_free_lock(vmd);
-			vm_phys_free_contig(m, pagecount);
+			vm_phys_free_bounded_contig(m, pagecount);
 			vm_domain_free_unlock(vmd);
 			vm_domain_freecnt_inc(vmd, pagecount);
 			vm_cnt.v_page_count += (u_int)pagecount;
Index: vm_phys.h
===================================================================
--- vm_phys.h
+++ vm_phys.h
@@ -88,6 +88,7 @@
     vm_memattr_t memattr);
 void vm_phys_fictitious_unreg_range(vm_paddr_t start, vm_paddr_t end);
 vm_page_t vm_phys_fictitious_to_vm_page(vm_paddr_t pa);
+void vm_phys_free_bounded_contig(vm_page_t m, u_long npages);
 void vm_phys_free_contig(vm_page_t m, u_long npages);
 void vm_phys_free_pages(vm_page_t m, int order);
 void vm_phys_init(void);
Index: vm_phys.c
===================================================================
--- vm_phys.c
+++ vm_phys.c
@@ -1095,14 +1095,38 @@
 }
 
 /*
- * Free a contiguous, arbitrarily sized set of physical pages.
+ * Return the largest possible order of a page starting at m.
+ */
+static int
+max_order(vm_page_t m)
+{
+	/*
+	 * Unsigned "min" is used here so that "order" is assigned
+	 * "VM_NFREEORDER - 1" when "m"'s physical address is zero
+	 * or the low-order bits of its physical address are zero
+	 * because the size of a physical address exceeds the size of
+	 * a long.
+	 */
+	return (min(ffsl(VM_PAGE_TO_PHYS(m) >> PAGE_SHIFT) - 1,
+	    VM_NFREEORDER - 1));
+}
+
+/*
+ * Free a contiguous, arbitrarily sized set of physical pages, without
+ * merging across set boundaries.
  *
+ * Either the pages just across a boundary must be allocated, or the boundary
+ * must be superpage boundary, because there is no check here for
+ * buddy-system merges across a boundary.
+ *
  * The free page queues must be locked.
  */
 void
-vm_phys_free_contig(vm_page_t m, u_long npages)
+vm_phys_free_bounded_contig(vm_page_t m, u_long npages)
 {
-	u_int n;
+	struct vm_freelist *fl;
+	struct vm_phys_seg *seg;
+	vm_page_t m_end;
 	int order;
 
 	/*
@@ -1110,32 +1134,71 @@
 	 * possible power-of-two-sized subsets.
 	 */
 	vm_domain_free_assert_locked(vm_pagequeue_domain(m));
-	for (;; npages -= n) {
-		/*
-		 * Unsigned "min" is used here so that "order" is assigned
-		 * "VM_NFREEORDER - 1" when "m"'s physical address is zero
-		 * or the low-order bits of its physical address are zero
-		 * because the size of a physical address exceeds the size of
-		 * a long.
-		 */
-		order = min(ffsl(VM_PAGE_TO_PHYS(m) >> PAGE_SHIFT) - 1,
-		    VM_NFREEORDER - 1);
-		n = 1 << order;
-		if (npages < n)
-			break;
-		vm_phys_free_pages(m, order);
-		m += n;
+	seg = &vm_phys_segs[m->segind];
+	fl = (*seg->free_queues)[m->pool];
+	m_end = m + npages;
+	/* Free blocks of increasing size. */
+	while ((order = max_order(m)) < VM_NFREEORDER - 1 &&
+	    m + (1 << order) <= m_end) {
+		KASSERT(seg == &vm_phys_segs[m->segind],
+		    ("%s: page range [%p,%p) spans multiple segments",
+		     __func__, m, m_end));
+		vm_freelist_add(fl, m, order, 1);
+		m += (1 << order);
 	}
-	/* The residual "npages" is less than "1 << (VM_NFREEORDER - 1)". */
-	for (; npages > 0; npages -= n) {
-		order = flsl(npages) - 1;
-		n = 1 << order;
-		vm_phys_free_pages(m, order);
-		m += n;
+	/* Free blocks of maximum size. */
+	while (m + (1 << order) <= m_end) {
+		KASSERT(seg == &vm_phys_segs[m->segind],
+		    ("%s: page range [%p,%p) spans multiple segments",
+		     __func__, m, m_end));
+		vm_freelist_add(fl, m, order, 1);
+		m += (1 << order);
 	}
+	/* Free blocks of diminishing size. */
+	while (m < m_end) {
+		KASSERT(seg == &vm_phys_segs[m->segind],
+		    ("%s: page range [%p,%p) spans multiple segments",
+		     __func__, m, m_end));
+		order = flsl(m_end - m) - 1;
+		vm_freelist_add(fl, m, order, 1);
+		m += (1 << order);
+	}
 }
 
 /*
+ * Free a contiguous, arbitrarily sized set of physical pages.
+ *
+ * The free page queues must be locked.
+ */
+void
+vm_phys_free_contig(vm_page_t m, u_long npages)
+{
+	int order_start, order_end;
+	vm_page_t m_start, m_end;
+
+	vm_domain_free_assert_locked(vm_pagequeue_domain(m));
+
+	m_start = m;
+	order_start = max_order(m_start);
+	if (order_start < VM_NFREEORDER - 1)
+		m_start += 1 << order_start;
+	m_end = m + npages;
+	order_end = max_order(m_end);
+	if (order_end < VM_NFREEORDER - 1)
+		m_end -= 1 << order_end;
+	/*
+	 * Avoid unnecessary coalescing by freeing the pages at the start and
+	 * end of the range last.
+	 */
+	if (m_start < m_end)
+		vm_phys_free_bounded_contig(m_start, m_end - m_start);
+	if (order_start < VM_NFREEORDER - 1)
+		vm_phys_free_pages(m, order_start);
+	if (order_end < VM_NFREEORDER - 1)
+		vm_phys_free_pages(m_end, order_end);
+}
+
+/*
  * Scan physical memory between the specified addresses "low" and "high" for a
  * run of contiguous physical pages that satisfy the specified conditions, and
  * return the lowest page in the run.  The specified "alignment" determines
Index: vm_reserv.c
===================================================================
--- vm_reserv.c
+++ vm_reserv.c
@@ -1066,7 +1066,8 @@
 			else {
 				hi = NBPOPMAP * i + bitpos;
 				vm_domain_free_lock(VM_DOMAIN(rv->domain));
-				vm_phys_free_contig(&rv->pages[lo], hi - lo);
+				vm_phys_free_bounded_contig(&rv->pages[lo],
+				    hi - lo);
 				vm_domain_free_unlock(VM_DOMAIN(rv->domain));
 				lo = hi;
 			}