diff -ru ../../REF/2.4.16-ia64-011128/arch/ia64/lib/swiotlb.c linux/arch/ia64/lib/swiotlb.c
--- ../../REF/2.4.16-ia64-011128/arch/ia64/lib/swiotlb.c	Wed Nov 28 16:55:04 2001
+++ linux/arch/ia64/lib/swiotlb.c	Mon Dec  3 11:41:51 2001
@@ -27,6 +27,16 @@
 #define ALIGN(val, align) ((unsigned long)	\
 	(((unsigned long) (val) + ((align) - 1)) & ~((align) - 1)))
 
+#define OFFSET(val,align) ((unsigned long)	\
+	                   ( (val) & ( (align) - 1)))
+
+/*
+ * Maximum allowable number of contiguous slabs to map, 
+ * must be a power of 2.  What is the appropriate value ?
+ * The complexity of {map,unmap}_single is linearly dependent on this value.
+ */ 
+#define IO_TLB_SEGSIZE	128
+
 /*
  * log of the size of each IO TLB slab.  The number of slabs is command line controllable.
  */
@@ -65,10 +75,15 @@
 setup_io_tlb_npages (char *str)
 {
 	io_tlb_nslabs = simple_strtoul(str, NULL, 0) << (PAGE_SHIFT - IO_TLB_SHIFT);
+
+	/* avoid tail segment of size < IO_TLB_SEGSIZE */  
+	io_tlb_nslabs = ALIGN(io_tlb_nslabs, IO_TLB_SEGSIZE);
+
 	return 1;
 }
 __setup("swiotlb=", setup_io_tlb_npages);
 
+
 /*
  * Statically reserve bounce buffer space and initialize bounce buffer data structures for
  * the software IO TLB used to implement the PCI DMA API.
@@ -88,12 +103,12 @@
 
 	/*
 	 * Allocate and initialize the free list array.  This array is used
-	 * to find contiguous free memory regions of size 2^IO_TLB_SHIFT between
-	 * io_tlb_start and io_tlb_end.
+	 * to find contiguous free memory regions of size up to IO_TLB_SEGSIZE
+	 * between io_tlb_start and io_tlb_end.
 	 */
 	io_tlb_list = alloc_bootmem(io_tlb_nslabs * sizeof(int));
 	for (i = 0; i < io_tlb_nslabs; i++)
-		io_tlb_list[i] = io_tlb_nslabs - i;
+ 		io_tlb_list[i] = IO_TLB_SEGSIZE - OFFSET(i, IO_TLB_SEGSIZE);
 	io_tlb_index = 0;
 	io_tlb_orig_addr = alloc_bootmem(io_tlb_nslabs * sizeof(char *));
 
@@ -120,7 +135,7 @@
 	if (size > (1 << PAGE_SHIFT))
 		stride = (1 << (PAGE_SHIFT - IO_TLB_SHIFT));
 	else
-		stride = nslots;
+		stride = 1; 
 
 	if (!nslots)
 		BUG();
@@ -147,7 +162,8 @@
 
 				for (i = index; i < index + nslots; i++)
 					io_tlb_list[i] = 0;
-				for (i = index - 1; (i >= 0) && io_tlb_list[i]; i--)
+				for (i = index - 1; (OFFSET(i, IO_TLB_SEGSIZE) != IO_TLB_SEGSIZE -1)
+				       && io_tlb_list[i]; i--)
 					io_tlb_list[i] = ++count;
 				dma_addr = io_tlb_start + (index << IO_TLB_SHIFT);
 
@@ -213,7 +229,8 @@
 	 */
 	spin_lock_irqsave(&io_tlb_lock, flags);
 	{
-		int count = ((index + nslots) < io_tlb_nslabs ? io_tlb_list[index + nslots] : 0);
+		int count = ((index + nslots) < ALIGN(index + 1, IO_TLB_SEGSIZE) ?
+			     io_tlb_list[index + nslots] : 0);
 		/*
 		 * Step 1: return the slots to the free list, merging the slots with
 		 * superceeding slots
@@ -224,7 +241,8 @@
 		 * Step 2: merge the returned slots with the preceeding slots, if
 		 * available (non zero)
 		 */
-		for (i = index - 1; (i >= 0) && io_tlb_list[i]; i--)
+		for (i = index - 1;  (OFFSET(i, IO_TLB_SEGSIZE) != IO_TLB_SEGSIZE -1) &&
+		       io_tlb_list[i]; i--)
 			io_tlb_list[i] = ++count;
 	}
 	spin_unlock_irqrestore(&io_tlb_lock, flags);