RE: [Patch] Move swiotlb_init early on X86_64

[Zou Nan hai <nanhai.zou@intel.com>]

On Thu, 2006-03-02 at 17:09, Zhang, Yanmin wrote:
> >>-----Original Message-----
> >>From: linux-kernel-owner@vger.kernel.org [mailto:linux-kernel-owner@vger.kernel.org] On Behalf Of Zou Nan hai
> >>Sent: 2006年3月2日 12:33
> >>
> >>Really, then how about the following patch?
> >>
> >>Let normal bootmem allocator go above 4G first.
> >>This will save more memory with address less than 4G.
> >>
> >>Signed-off-by: Zou Nan hai <nanhai.zou@intel.com>
> >>
> >>--- linux-2.6.16-rc5/mm/bootmem.c	2006-03-03 08:31:52.000000000 +0800
> >>+++ b/mm/bootmem.c	2006-03-03 09:05:17.000000000 +0800
> >>@@ -381,16 +381,24 @@ unsigned long __init free_all_bootmem (v
> >> 	return(free_all_bootmem_core(NODE_DATA(0)));
> >> }
> >>
> >>+#define LOW32LIMIT 0xffffffff
> >>+
> >> void * __init __alloc_bootmem(unsigned long size, unsigned long align, unsigned long goal)
> >> {
> >> 	pg_data_t *pgdat = pgdat_list;
> >> 	void *ptr;
> >>
> >>+	if (goal < LOW32LIMIT) {
> On i386, above is always true.
> 
> 

Ok, I modified the patch.

On single node SMP System with large physical memory, 
allocation from bootmem allocator like memmap and vfs_cache 
may eat up usable memory under 4G, then software I/O TLB will not be able to allocate bounce buffer.

This patch modify the bootmem allocator,
let normal bootmem allocation on 64 bit system first go above 4G
address.

Signed-off-by: Zou Nan hai <nanhai.zou@intel.com>

--- linux-2.6.16-rc5/mm/bootmem.c	2006-03-03 08:31:52.000000000 +0800
+++ b/mm/bootmem.c	2006-03-04 03:48:55.000000000 +0800
@@ -381,16 +381,25 @@ unsigned long __init free_all_bootmem (v
 	return(free_all_bootmem_core(NODE_DATA(0)));
 }
 
+#define LOW32LIMIT 0xffffffff
+
 void * __init __alloc_bootmem(unsigned long size, unsigned long align, unsigned long goal)
 {
 	pg_data_t *pgdat = pgdat_list;
 	void *ptr;
 
+#if (BITS_PER_LONG == 64)
+	if (goal < LOW32LIMIT) {
+		for_each_pgdat(pgdat)
+			if ((ptr = __alloc_bootmem_core(pgdat->bdata, size,
+						 align, LOW32LIMIT, 0)))
+			return(ptr);
+	}
+#endif
 	for_each_pgdat(pgdat)
 		if ((ptr = __alloc_bootmem_core(pgdat->bdata, size,
 						 align, goal, 0)))
 			return(ptr);
-
 	/*
 	 * Whoops, we cannot satisfy the allocation request.
 	 */
@@ -404,6 +413,14 @@ void * __init __alloc_bootmem_node(pg_da
 				   unsigned long goal)
 {
 	void *ptr;
+#if (BITS_PER_LONG == 64)
+	if (goal < LOW32LIMIT) {
+		ptr = __alloc_bootmem_core(pgdat->bdata, size, align,
+				LOW32LIMIT, 0);
+		if (ptr)
+			return (ptr);
+	}
+#endif
 
 	ptr = __alloc_bootmem_core(pgdat->bdata, size, align, goal, 0);
 	if (ptr)
@@ -412,7 +429,6 @@ void * __init __alloc_bootmem_node(pg_da
 	return __alloc_bootmem(size, align, goal);
 }
 
-#define LOW32LIMIT 0xffffffff
 
 void * __init __alloc_bootmem_low(unsigned long size, unsigned long align, unsigned long goal)
 {