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Subject[PATCH 3/8] Fragmentation Avoidance V17: 003_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 three free lists for each RCLM_TYPE.

Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Mike Kravetz <kravetz@us.ibm.com>
Signed-off-by: Joel Schopp <jschopp@austin.ibm.com>
diff -rup -X /usr/src/patchset-0.5/bin//dontdiff linux-2.6.14-rc3-002_usemap/include/linux/mmzone.h linux-2.6.14-rc3-003_fragcore/include/linux/mmzone.h
--- linux-2.6.14-rc3-002_usemap/include/linux/mmzone.h 2005-10-11 12:07:26.000000000 +0100
+++ linux-2.6.14-rc3-003_fragcore/include/linux/mmzone.h 2005-10-11 12:08:07.000000000 +0100
@@ -32,6 +32,10 @@
#define RCLM_TYPES 3
#define BITS_PER_RCLM_TYPE 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;
unsigned long nr_free;
@@ -148,7 +152,6 @@ struct zone {
* free areas of different sizes
*/
spinlock_t lock;
- struct free_area free_area[MAX_ORDER];

#ifndef CONFIG_SPARSEMEM
/*
@@ -158,6 +161,8 @@ struct zone {
unsigned long *free_area_usemap;
#endif

+ struct free_area free_area_lists[RCLM_TYPES][MAX_ORDER];
+
ZONE_PADDING(_pad1_)

/* Fields commonly accessed by the page reclaim scanner */
diff -rup -X /usr/src/patchset-0.5/bin//dontdiff linux-2.6.14-rc3-002_usemap/mm/page_alloc.c linux-2.6.14-rc3-003_fragcore/mm/page_alloc.c
--- linux-2.6.14-rc3-002_usemap/mm/page_alloc.c 2005-10-11 12:07:26.000000000 +0100
+++ linux-2.6.14-rc3-003_fragcore/mm/page_alloc.c 2005-10-11 12:08:07.000000000 +0100
@@ -314,6 +314,16 @@ __find_combined_index(unsigned long page
}

/*
+ * Return the free list for a given page within a zone
+ */
+static inline struct free_area *__page_find_freelist(struct zone *zone,
+ struct page *page)
+{
+ int type = (int)get_pageblock_type(zone, page);
+ return zone->free_area_lists[type];
+}
+
+/*
* This function checks whether a page is free && is the buddy
* we can do coalesce a page and its buddy if
* (a) the buddy is free &&
@@ -361,6 +371,8 @@ static inline void __free_pages_bulk (st
{
unsigned long page_idx;
int order_size = 1 << order;
+ struct free_area *area;
+ struct free_area *freelist;

if (unlikely(order))
destroy_compound_page(page, order);
@@ -370,10 +382,11 @@ static inline void __free_pages_bulk (st
BUG_ON(page_idx & (order_size - 1));
BUG_ON(bad_range(zone, page));

+ freelist = __page_find_freelist(zone, page);
+
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);
@@ -384,7 +397,7 @@ 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 = &(freelist[order]);
area->nr_free--;
rmv_page_order(buddy);
page = page + (combined_idx - page_idx);
@@ -392,8 +405,8 @@ static inline void __free_pages_bulk (st
order++;
}
set_page_order(page, order);
- list_add(&page->lru, &zone->free_area[order].free_list);
- zone->free_area[order].nr_free++;
+ list_add_tail(&page->lru, &freelist[order].free_list);
+ freelist[order].nr_free++;
}

static inline void free_pages_check(const char *function, struct page *page)
@@ -548,6 +561,47 @@ static void prep_new_page(struct page *p
kernel_map_pages(page, 1 << order, 1);
}

+/*
+ * Find a list that has a 2^MAX_ORDER-1 block of pages available and
+ * return it
+ */
+struct page* steal_largepage(struct zone *zone, int alloctype)
+{
+ struct page *page;
+ struct free_area *area = NULL;
+ int i = 0;
+
+ for(i = 0; i < RCLM_TYPES; i++) {
+ if (i == alloctype)
+ continue;
+
+ area = &zone->free_area_lists[i][MAX_ORDER-1];
+ if (!list_empty(&area->free_list))
+ break;
+ }
+ if (i == RCLM_TYPES)
+ return NULL;
+
+ page = list_entry(area->free_list.next, struct page, lru);
+ area->nr_free--;
+
+ set_pageblock_type(zone, page, (unsigned long)alloctype);
+
+ return page;
+}
+
+
+static inline struct page *
+remove_page(struct zone *zone, struct page *page, unsigned int order,
+ unsigned int current_order, struct free_area *area)
+{
+ list_del(&page->lru);
+ rmv_page_order(page);
+ zone->free_pages -= 1UL << order;
+ return expand(zone, page, order, current_order, area);
+
+}
+
/*
* Do the hard work of removing an element from the buddy allocator.
* Call me with the zone->lock already held.
@@ -555,32 +609,25 @@ static void prep_new_page(struct page *p
static struct page *__rmqueue(struct zone *zone, unsigned int order,
int alloctype)
{
- struct free_area * area;
+ struct free_area * area = NULL;
unsigned int current_order;
struct page *page;

for (current_order = order; current_order < MAX_ORDER; ++current_order) {
- area = zone->free_area + current_order;
+ area = &(zone->free_area_lists[alloctype][current_order]);
if (list_empty(&area->free_list))
continue;

page = list_entry(area->free_list.next, struct page, lru);
- list_del(&page->lru);
- rmv_page_order(page);
area->nr_free--;
- zone->free_pages -= 1UL << order;
-
- /*
- * If splitting a large block, record what the block is being
- * used for in the usemap
- */
- if (current_order == MAX_ORDER-1)
- set_pageblock_type(zone, page,
- (unsigned long)alloctype);
-
- return expand(zone, page, order, current_order, area);
+ return remove_page(zone, page, order, current_order, area);
}

+ /* Allocate a MAX_ORDER block */
+ page = steal_largepage(zone, alloctype);
+ if (page != NULL)
+ return remove_page(zone, page, order, MAX_ORDER-1, area);
+
return NULL;
}

@@ -666,9 +713,9 @@ static void __drain_pages(unsigned int c
void mark_free_pages(struct zone *zone)
{
unsigned long zone_pfn, flags;
- int order;
+ int order, t;
+ unsigned long start_pfn, i;
struct list_head *curr;
-
if (!zone->spanned_pages)
return;

@@ -676,14 +723,12 @@ void mark_free_pages(struct zone *zone)
for (zone_pfn = 0; zone_pfn < zone->spanned_pages; ++zone_pfn)
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) {
- unsigned long start_pfn, i;
-
+ for_each_rclmtype_order(t, order) {
+ list_for_each(curr,&zone->free_area_lists[t][order].free_list){
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);
}
@@ -834,6 +879,7 @@ int zone_watermark_ok(struct zone *z, in
/* free_pages my go negative - that's OK */
long min = mark, free_pages = z->free_pages - (1 << order) + 1;
int o;
+ struct free_area *kernnorclm, *kernrclm, *userrclm;

if (gfp_high)
min -= min / 2;
@@ -842,15 +888,21 @@ int zone_watermark_ok(struct zone *z, in

if (free_pages <= min + z->lowmem_reserve[classzone_idx])
return 0;
+ kernnorclm = z->free_area_lists[RCLM_NORCLM];
+ kernrclm = z->free_area_lists[RCLM_KERN];
+ userrclm = z->free_area_lists[RCLM_USER];
for (o = 0; o < order; o++) {
/* At the next order, this order's pages become unavailable */
- free_pages -= z->free_area[o].nr_free << o;
-
+ free_pages -= (kernnorclm->nr_free + kernrclm->nr_free +
+ userrclm->nr_free) << o;
/* Require fewer higher order pages to be free */
min >>= 1;

if (free_pages <= min)
return 0;
+ kernnorclm++;
+ kernrclm++;
+ userrclm++;
}
return 1;
}
@@ -1389,6 +1441,7 @@ void show_free_areas(void)
unsigned long inactive;
unsigned long free;
struct zone *zone;
+ int type;

for_each_zone(zone) {
show_node(zone);
@@ -1471,7 +1524,9 @@ void show_free_areas(void)
}

for_each_zone(zone) {
- unsigned long nr, flags, order, total = 0;
+ unsigned long nr = 0;
+ unsigned long total = 0;
+ unsigned long flags,order;

show_node(zone);
printk("%s: ", zone->name);
@@ -1481,10 +1536,18 @@ void show_free_areas(void)
}

spin_lock_irqsave(&zone->lock, flags);
- for (order = 0; order < MAX_ORDER; order++) {
- nr = zone->free_area[order].nr_free;
+ for_each_rclmtype_order(type, order) {
+ nr += zone->free_area_lists[type][order].nr_free;
total += nr << order;
- printk("%lu*%lukB ", nr, K(1UL) << order);
+
+ /*
+ * if type had reached RCLM_TYPE, the free pages
+ * for this order have been summed up
+ */
+ if (type == RCLM_TYPES-1) {
+ printk("%lu*%lukB ", nr, K(1UL) << order);
+ nr = 0;
+ }
}
spin_unlock_irqrestore(&zone->lock, flags);
printk("= %lukB\n", K(total));
@@ -1784,9 +1847,14 @@ void zone_init_free_lists(struct pglist_
unsigned long size)
{
int order;
- for (order = 0; order < MAX_ORDER ; order++) {
- INIT_LIST_HEAD(&zone->free_area[order].free_list);
- zone->free_area[order].nr_free = 0;
+ int type;
+ struct free_area *area;
+
+ /* Initialse the three size ordered lists of free_areas */
+ for_each_rclmtype_order(type, order) {
+ area = &(zone->free_area_lists[type][order]);
+ INIT_LIST_HEAD(&area->free_list);
+ area->nr_free = 0;
}
}

@@ -2178,16 +2246,26 @@ static int frag_show(struct seq_file *m,
struct zone *zone;
struct zone *node_zones = pgdat->node_zones;
unsigned long flags;
- int order;
+ int order, type;
+ struct free_area *area;
+ unsigned long nr_bufs = 0;

for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) {
if (!zone->present_pages)
continue;

spin_lock_irqsave(&zone->lock, flags);
- seq_printf(m, "Node %d, zone %8s ", pgdat->node_id, zone->name);
- for (order = 0; order < MAX_ORDER; ++order)
- seq_printf(m, "%6lu ", zone->free_area[order].nr_free);
+ seq_printf(m, "Node %d, zone %8s", pgdat->node_id, zone->name);
+ for_each_rclmtype_order(type, order) {
+ area = &(zone->free_area_lists[type][order]);
+ nr_bufs += area->nr_free;
+
+ if (type == RCLM_TYPES-1) {
+ seq_printf(m, "%6lu ", nr_bufs);
+ nr_bufs = 0;
+ }
+ }
+
spin_unlock_irqrestore(&zone->lock, flags);
seq_putc(m, '\n');
}
-
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