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Subject[PATCH 2/5] Light fragmentation avoidance without usemap: 002_fragcore
Date
This patch adds the core of the anti-fragmentation strategy. It works by
grouping related allocation types together. The idea is that large groups of
pages that may be reclaimed are placed near each other. The zone->free_area
list is broken into RCLM_TYPES number of lists.

Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Joel Schopp <jschopp@austin.ibm.com>
diff -rup -X /usr/src/patchset-0.5/bin//dontdiff linux-2.6.15-rc1-mm2-001_antidefrag_flags/include/linux/mmzone.h linux-2.6.15-rc1-mm2-002_fragcore/include/linux/mmzone.h
--- linux-2.6.15-rc1-mm2-001_antidefrag_flags/include/linux/mmzone.h 2005-11-21 19:44:33.000000000 +0000
+++ linux-2.6.15-rc1-mm2-002_fragcore/include/linux/mmzone.h 2005-11-22 16:50:09.000000000 +0000
@@ -22,8 +22,16 @@
#define MAX_ORDER CONFIG_FORCE_MAX_ZONEORDER
#endif

+#define RCLM_NORCLM 0
+#define RCLM_EASY 1
+#define RCLM_TYPES 2
+
+#define for_each_rclmtype_order(type, order) \
+ for (order = 0; order < MAX_ORDER; order++) \
+ for (type = 0; type < RCLM_TYPES; type++)
+
struct free_area {
- struct list_head free_list;
+ struct list_head free_list[RCLM_TYPES];
unsigned long nr_free;
};

diff -rup -X /usr/src/patchset-0.5/bin//dontdiff linux-2.6.15-rc1-mm2-001_antidefrag_flags/include/linux/page-flags.h linux-2.6.15-rc1-mm2-002_fragcore/include/linux/page-flags.h
--- linux-2.6.15-rc1-mm2-001_antidefrag_flags/include/linux/page-flags.h 2005-11-21 19:44:33.000000000 +0000
+++ linux-2.6.15-rc1-mm2-002_fragcore/include/linux/page-flags.h 2005-11-22 16:50:09.000000000 +0000
@@ -76,6 +76,7 @@
#define PG_reclaim 17 /* To be reclaimed asap */
#define PG_nosave_free 18 /* Free, should not be written */
#define PG_uncached 19 /* Page has been mapped as uncached */
+#define PG_easyrclm 20 /* Page is in an easy reclaim block */

/*
* Global page accounting. One instance per CPU. Only unsigned longs are
@@ -304,6 +305,12 @@ extern void __mod_page_state(unsigned lo
#define SetPageUncached(page) set_bit(PG_uncached, &(page)->flags)
#define ClearPageUncached(page) clear_bit(PG_uncached, &(page)->flags)

+#define PageEasyRclm(page) test_bit(PG_easyrclm, &(page)->flags)
+#define SetPageEasyRclm(page) set_bit(PG_easyrclm, &(page)->flags)
+#define ClearPageEasyRclm(page) clear_bit(PG_easyrclm, &(page)->flags)
+#define __SetPageEasyRclm(page) __set_bit(PG_easyrclm, &(page)->flags)
+#define __ClearPageEasyRclm(page) __clear_bit(PG_easyrclm, &(page)->flags)
+
struct page; /* forward declaration */

int test_clear_page_dirty(struct page *page);
diff -rup -X /usr/src/patchset-0.5/bin//dontdiff linux-2.6.15-rc1-mm2-001_antidefrag_flags/mm/page_alloc.c linux-2.6.15-rc1-mm2-002_fragcore/mm/page_alloc.c
--- linux-2.6.15-rc1-mm2-001_antidefrag_flags/mm/page_alloc.c 2005-11-21 19:44:33.000000000 +0000
+++ linux-2.6.15-rc1-mm2-002_fragcore/mm/page_alloc.c 2005-11-22 16:50:09.000000000 +0000
@@ -68,6 +68,16 @@ int sysctl_lowmem_reserve_ratio[MAX_NR_Z

EXPORT_SYMBOL(totalram_pages);

+static inline int get_pageblock_type(struct page *page)
+{
+ return (PageEasyRclm(page) != 0);
+}
+
+static inline int gfpflags_to_alloctype(unsigned long gfp_flags)
+{
+ return ((gfp_flags & __GFP_EASYRCLM) != 0);
+}
+
/*
* Used by page_zone() to look up the address of the struct zone whose
* id is encoded in the upper bits of page->flags
@@ -314,11 +324,13 @@ static inline void __free_pages_bulk (st
{
unsigned long page_idx;
int order_size = 1 << order;
+ int alloctype = get_pageblock_type(page);

if (unlikely(order))
destroy_compound_page(page, order);

page_idx = page_to_pfn(page) & ((1 << MAX_ORDER) - 1);
+ __SetPageEasyRclm(page);

BUG_ON(page_idx & (order_size - 1));
BUG_ON(bad_range(zone, page));
@@ -326,7 +338,6 @@ static inline void __free_pages_bulk (st
zone->free_pages += order_size;
while (order < MAX_ORDER-1) {
unsigned long combined_idx;
- struct free_area *area;
struct page *buddy;

combined_idx = __find_combined_index(page_idx, order);
@@ -337,15 +348,14 @@ static inline void __free_pages_bulk (st
if (!page_is_buddy(buddy, order))
break; /* Move the buddy up one level. */
list_del(&buddy->lru);
- area = zone->free_area + order;
- area->nr_free--;
+ zone->free_area[order].nr_free--;
rmv_page_order(buddy);
page = page + (combined_idx - page_idx);
page_idx = combined_idx;
order++;
}
set_page_order(page, order);
- list_add(&page->lru, &zone->free_area[order].free_list);
+ list_add(&page->lru, &zone->free_area[order].free_list[alloctype]);
zone->free_area[order].nr_free++;
}

@@ -450,7 +460,8 @@ void __free_pages_ok(struct page *page,
*/
static inline struct page *
expand(struct zone *zone, struct page *page,
- int low, int high, struct free_area *area)
+ int low, int high, struct free_area *area,
+ int alloctype)
{
unsigned long size = 1 << high;

@@ -459,7 +470,7 @@ expand(struct zone *zone, struct page *p
high--;
size >>= 1;
BUG_ON(bad_range(zone, &page[size]));
- list_add(&page[size].lru, &area->free_list);
+ list_add(&page[size].lru, &area->free_list[alloctype]);
area->nr_free++;
set_page_order(&page[size], high);
}
@@ -520,30 +531,79 @@ static int prep_new_page(struct page *pa
return 0;
}

+/* Remove an element from the buddy allocator from the fallback list */
+static struct page *__rmqueue_fallback(struct zone *zone, int order,
+ int alloctype)
+{
+ struct free_area * area;
+ int current_order;
+ struct page *page;
+
+ /* Find the largest possible block of pages in the other list */
+ alloctype = !alloctype;
+ for (current_order = MAX_ORDER-1; current_order >= order;
+ --current_order) {
+ area = &(zone->free_area[current_order]);
+ if (list_empty(&area->free_list[alloctype]))
+ continue;
+
+ page = list_entry(area->free_list[alloctype].next,
+ struct page, lru);
+ area->nr_free--;
+
+ /*
+ * If breaking a large block of pages, place the buddies
+ * on the preferred allocation list
+ */
+ if (unlikely(current_order >= MAX_ORDER / 2))
+ alloctype = !alloctype;
+
+ list_del(&page->lru);
+ rmv_page_order(page);
+ zone->free_pages -= 1UL << order;
+ return expand(zone, page, order, current_order, area,
+ alloctype);
+
+ }
+
+ return NULL;
+}
+
/*
* Do the hard work of removing an element from the buddy allocator.
* Call me with the zone->lock already held.
*/
-static struct page *__rmqueue(struct zone *zone, unsigned int order)
+static struct page *__rmqueue(struct zone *zone, unsigned int order,
+ int alloctype)
{
struct free_area * area;
unsigned int current_order;
struct page *page;

+ /* Find a page of the appropriate size in the preferred list */
for (current_order = order; current_order < MAX_ORDER; ++current_order) {
- area = zone->free_area + current_order;
- if (list_empty(&area->free_list))
+ area = &(zone->free_area[current_order]);
+ if (list_empty(&area->free_list[alloctype]))
continue;

- page = list_entry(area->free_list.next, struct page, lru);
+ page = list_entry(area->free_list[alloctype].next,
+ struct page, lru);
list_del(&page->lru);
rmv_page_order(page);
area->nr_free--;
zone->free_pages -= 1UL << order;
- return expand(zone, page, order, current_order, area);
+ page = expand(zone, page, order, current_order, area,
+ alloctype);
+ goto got_page;
}

- return NULL;
+ page = __rmqueue_fallback(zone, order, alloctype);
+
+got_page:
+ if (unlikely(alloctype == RCLM_NORCLM))
+ __ClearPageEasyRclm(page);
+
+ return page;
}

/*
@@ -552,7 +612,8 @@ static struct page *__rmqueue(struct zon
* Returns the number of new pages which were placed at *list.
*/
static int rmqueue_bulk(struct zone *zone, unsigned int order,
- unsigned long count, struct list_head *list)
+ unsigned long count, struct list_head *list,
+ int alloctype)
{
unsigned long flags;
int i;
@@ -561,7 +622,7 @@ static int rmqueue_bulk(struct zone *zon

spin_lock_irqsave(&zone->lock, flags);
for (i = 0; i < count; ++i) {
- page = __rmqueue(zone, order);
+ page = __rmqueue(zone, order, alloctype);
if (page == NULL)
break;
allocated++;
@@ -627,7 +688,7 @@ static void __drain_pages(unsigned int c
void mark_free_pages(struct zone *zone)
{
unsigned long zone_pfn, flags;
- int order;
+ int order, t;
struct list_head *curr;

if (!zone->spanned_pages)
@@ -638,13 +699,15 @@ void mark_free_pages(struct zone *zone)
ClearPageNosaveFree(pfn_to_page(zone_pfn + zone->zone_start_pfn));

for (order = MAX_ORDER - 1; order >= 0; --order)
- list_for_each(curr, &zone->free_area[order].free_list) {
+ for_each_rclmtype_order(t, order) {
+ list_for_each(curr, &zone->free_area[order].free_list[t]) {
unsigned long start_pfn, i;

start_pfn = page_to_pfn(list_entry(curr, struct page, lru));

for (i=0; i < (1<<order); i++)
SetPageNosaveFree(pfn_to_page(start_pfn+i));
+ }
}
spin_unlock_irqrestore(&zone->lock, flags);
}
@@ -748,6 +811,7 @@ buffered_rmqueue(struct zone *zone, int
unsigned long flags;
struct page *page;
int cold = !!(gfp_flags & __GFP_COLD);
+ int alloctype = gfpflags_to_alloctype(gfp_flags);

again:
if (order == 0) {
@@ -758,7 +822,8 @@ again:
local_irq_save(flags);
if (pcp->count <= pcp->low)
pcp->count += rmqueue_bulk(zone, 0,
- pcp->batch, &pcp->list);
+ pcp->batch, &pcp->list,
+ alloctype);
if (pcp->count) {
page = list_entry(pcp->list.next, struct page, lru);
list_del(&page->lru);
@@ -768,7 +833,7 @@ again:
put_cpu();
} else {
spin_lock_irqsave(&zone->lock, flags);
- page = __rmqueue(zone, order);
+ page = __rmqueue(zone, order, alloctype);
spin_unlock_irqrestore(&zone->lock, flags);
}

@@ -1791,7 +1856,8 @@ void zone_init_free_lists(struct pglist_
{
int order;
for (order = 0; order < MAX_ORDER ; order++) {
- INIT_LIST_HEAD(&zone->free_area[order].free_list);
+ INIT_LIST_HEAD(&zone->free_area[order].free_list[RCLM_NORCLM]);
+ INIT_LIST_HEAD(&zone->free_area[order].free_list[RCLM_EASY]);
zone->free_area[order].nr_free = 0;
}
}
-
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