Re: [Patch] Move swiotlb_init early on X86_64

[Zou Nan hai]

On Thu, 2006-03-02 at 12:30, Andi Kleen wrote:
> On Thursday 02 March 2006 05:15, Tony Luck wrote:
> > On 01 Mar 2006 09:10:58 +0800, Zou Nan hai <nanhai.zou@xxxxxxxxx> wrote:
> > > on X86_64, swiotlb buffer is allocated in mem_init, after memmap and vfs cache allocation.
> > >
> > > On platforms with huge physical memory,
> > > large memmap and vfs cache may eat up all usable system memory
> > > under 4G.
> > >
> > > Move swiotlb_init early before memmap is allocated can
> > > solve this issue.
> > 
> > Shouldn't memmap be allocated from memory above 4G (if available)? Using
> > up lots of <4G memory on something that doesn't need to be below 4G
> > sounds like a poor use of resources.
> 
> On the really large machines it will be distributed over the nodes anyways.
> But yes the single node SMP case should probably allocate it higher.
> 
> -Andi

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@xxxxxxxxx>

--- 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) {
+		for_each_pgdat(pgdat)
+			if ((ptr = __alloc_bootmem_core(pgdat->bdata, size,
+						 align, LOW32LIMIT, 0)))
+			return(ptr);
+	}
+
 	for_each_pgdat(pgdat)
 		if ((ptr = __alloc_bootmem_core(pgdat->bdata, size,
 						 align, goal, 0)))
 			return(ptr);
-
 	/*
 	 * Whoops, we cannot satisfy the allocation request.
 	 */
@@ -405,6 +413,13 @@ void * __init __alloc_bootmem_node(pg_da
 {
 	void *ptr;
 
+	if (goal < LOW32LIMIT) {
+		ptr = __alloc_bootmem_core(pgdat->bdata, size, align,
+				LOW32LIMIT, 0);
+		if (ptr)
+			return (ptr);
+	}
+
 	ptr = __alloc_bootmem_core(pgdat->bdata, size, align, goal, 0);
 	if (ptr)
 		return (ptr);
@@ -412,7 +427,6 @@ 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)
 {





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