Re: [PATCH] improve speed of freeing bootmem

From: Josh Aas <josha_at_sgi.com>
Date: 2004-08-07 08:02:33
New patch is attached.

Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Josh Aas <josha@sgi.com>

-- 
Josh Aas
Silicon Graphics, Inc. (SGI)
Linux System Software
651-683-3068

Andrew Morton wrote:
> Josh Aas <josha@sgi.com> wrote:
> 
>>Attached is a patch that greatly improves the speed of freeing boot 
>>memory.
> 
> 
> hm, OK.  I have a vague feeling that Bill Irwin had patches to fix this up
> ages ago.
> 
> 
> A few nits:
> 
> 
>>--- a/mm/bootmem.c	2004-08-05 15:33:39.000000000 -0500
>>+++ b/mm/bootmem.c	2004-08-06 13:42:33.000000000 -0500
>>@@ -259,6 +259,7 @@ static unsigned long __init free_all_boo
>> 	unsigned long i, count, total = 0;
>> 	unsigned long idx;
>> 	unsigned long *map; 
>>+	int gofast = 0;
>> 
>> 	BUG_ON(!bdata->node_bootmem_map);
>> 
>>@@ -267,14 +268,32 @@ static unsigned long __init free_all_boo
>> 	page = virt_to_page(phys_to_virt(bdata->node_boot_start));
>> 	idx = bdata->node_low_pfn - (bdata->node_boot_start >> PAGE_SHIFT);
>> 	map = bdata->node_bootmem_map;
>>+	if (bdata->node_boot_start == 0 ||
>>+	    ffs(bdata->node_boot_start) - PAGE_SHIFT > ffs(BITS_PER_LONG))
>>+		gofast = 1;
> 
> 
> A comment describing the above reasoning would be nice.
> 
> 
>> 	for (i = 0; i < idx; ) {
>> 		unsigned long v = ~map[i / BITS_PER_LONG];
>>-		if (v) {
>>+		if (gofast && v == ~0UL) {
>>+			int j;
>>+
>>+			count += BITS_PER_LONG;
>>+			ClearPageReservedNoAtomic(page);
>>+			set_page_count(page, 1);
>>+			for (j = 1; j < BITS_PER_LONG; j++) {
>>+				if (j + 16 < BITS_PER_LONG) {
>>+                      			prefetchw(page + j + 16);
>>+                                }
> 
> 
> The whitespace/tabbing has gone funny here.
> 
> 
>>+#define ClearPageReservedNoAtomic(page)	(page)->flags &= ~(1UL << PG_reserved)
> 
> 
> The naming convention we used in 2.4 for the nonatomic operation was
> __ClearPageReserved(), so can we please stick with that?
> 
> And this macro can use __clear_bit() rather than open-coding it.

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Received on Fri Aug 6 18:02:39 2004

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