Index: sys/vm/vm_phys.c
===================================================================
--- sys/vm/vm_phys.c
+++ sys/vm/vm_phys.c
@@ -1034,13 +1034,37 @@
 }
 
 /*
- * 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 block merging.
+ *
+ * The pages just before and after the freed pages must be
+ * allocated, because there is no check here for buddy-
+ * system merges.
  *
  * The free page queues must be locked.
  */
-void
-vm_phys_free_contig(vm_page_t m, u_long npages)
+static void
+vm_phys_nomerge_free_contig(vm_page_t m, u_long npages)
 {
+	struct vm_freelist *fl;
+	struct vm_phys_seg *seg;
 	u_int n;
 	int order;
 
@@ -1049,32 +1073,59 @@
 	 * possible power-of-two-sized subsets.
 	 */
 	vm_domain_free_assert_locked(vm_pagequeue_domain(m));
+	seg = &vm_phys_segs[m->segind];
+	fl = (*seg->free_queues)[m->pool];
 	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);
+		order = max_order(m);
 		n = 1 << order;
 		if (npages < n)
 			break;
-		vm_phys_free_pages(m, order);
+		vm_freelist_add(fl, m, order, 1);
 		m += n;
 	}
 	/* 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);
+		vm_freelist_add(fl, m, order, 1);
 		m += n;
 	}
 }
 
 /*
+ * 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_nomerge_free_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