Commit b92a6edd authored by Mel Gorman's avatar Mel Gorman Committed by Linus Torvalds
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Add a configure option to group pages by mobility



The grouping mechanism has some memory overhead and a more complex allocation
path.  This patch allows the strategy to be disabled for small memory systems
or if it is known the workload is suffering because of the strategy.  It also
acts to show where the page groupings strategy interacts with the standard
buddy allocator.
Signed-off-by: default avatarMel Gorman <mel@csn.ul.ie>
Signed-off-by: default avatarJoel Schopp <jschopp@austin.ibm.com>
Cc: Andy Whitcroft <apw@shadowen.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 535131e6
......@@ -33,9 +33,15 @@
*/
#define PAGE_ALLOC_COSTLY_ORDER 3
#ifdef CONFIG_PAGE_GROUP_BY_MOBILITY
#define MIGRATE_UNMOVABLE 0
#define MIGRATE_MOVABLE 1
#define MIGRATE_TYPES 2
#else
#define MIGRATE_UNMOVABLE 0
#define MIGRATE_MOVABLE 0
#define MIGRATE_TYPES 1
#endif
#define for_each_migratetype_order(order, type) \
for (order = 0; order < MAX_ORDER; order++) \
......
......@@ -607,6 +607,19 @@ config BASE_SMALL
default 0 if BASE_FULL
default 1 if !BASE_FULL
config PAGE_GROUP_BY_MOBILITY
bool "Group pages based on their mobility in the page allocator"
def_bool y
help
The standard allocator will fragment memory over time which means
that high order allocations will fail even if kswapd is running. If
this option is set, the allocator will try and group page types
based on their ability to migrate or reclaim. This is a best effort
attempt at lowering fragmentation which a few workloads care about.
The loss is a more complex allocator that may perform slower. If
you are interested in working with large pages, say Y and set
/proc/sys/vm/min_free_bytes to 16374. Otherwise say N
menuconfig MODULES
bool "Enable loadable module support"
help
......
......@@ -158,6 +158,7 @@ int nr_node_ids __read_mostly = MAX_NUMNODES;
EXPORT_SYMBOL(nr_node_ids);
#endif
#ifdef CONFIG_PAGE_GROUP_BY_MOBILITY
static inline int get_pageblock_migratetype(struct page *page)
{
return get_pageblock_flags_group(page, PB_migrate, PB_migrate_end);
......@@ -174,6 +175,22 @@ static inline int gfpflags_to_migratetype(gfp_t gfp_flags)
return ((gfp_flags & __GFP_MOVABLE) != 0);
}
#else
static inline int get_pageblock_migratetype(struct page *page)
{
return MIGRATE_UNMOVABLE;
}
static void set_pageblock_migratetype(struct page *page, int migratetype)
{
}
static inline int gfpflags_to_migratetype(gfp_t gfp_flags)
{
return MIGRATE_UNMOVABLE;
}
#endif /* CONFIG_PAGE_GROUP_BY_MOBILITY */
#ifdef CONFIG_DEBUG_VM
static int page_outside_zone_boundaries(struct zone *zone, struct page *page)
{
......@@ -653,6 +670,7 @@ static int prep_new_page(struct page *page, int order, gfp_t gfp_flags)
return 0;
}
#ifdef CONFIG_PAGE_GROUP_BY_MOBILITY
/*
* This array describes the order lists are fallen back to when
* the free lists for the desirable migrate type are depleted
......@@ -709,6 +727,13 @@ static struct page *__rmqueue_fallback(struct zone *zone, int order,
return NULL;
}
#else
static struct page *__rmqueue_fallback(struct zone *zone, int order,
int start_migratetype)
{
return NULL;
}
#endif /* CONFIG_PAGE_GROUP_BY_MOBILITY */
/*
* Do the hard work of removing an element from the buddy allocator.
......@@ -953,27 +978,25 @@ again:
if (unlikely(!pcp->count))
goto failed;
}
#ifdef CONFIG_PAGE_GROUP_BY_MOBILITY
/* Find a page of the appropriate migrate type */
list_for_each_entry(page, &pcp->list, lru) {
if (page_private(page) == migratetype) {
list_del(&page->lru);
pcp->count--;
list_for_each_entry(page, &pcp->list, lru)
if (page_private(page) == migratetype)
break;
}
}
/*
* Check if a page of the appropriate migrate type
* was found. If not, allocate more to the pcp list
*/
if (&page->lru == &pcp->list) {
/* Allocate more to the pcp list if necessary */
if (unlikely(&page->lru == &pcp->list)) {
pcp->count += rmqueue_bulk(zone, 0,
pcp->batch, &pcp->list, migratetype);
page = list_entry(pcp->list.next, struct page, lru);
VM_BUG_ON(page_private(page) != migratetype);
list_del(&page->lru);
pcp->count--;
}
#else
page = list_entry(pcp->list.next, struct page, lru);
#endif /* CONFIG_PAGE_GROUP_BY_MOBILITY */
list_del(&page->lru);
pcp->count--;
} else {
spin_lock_irqsave(&zone->lock, flags);
page = __rmqueue(zone, order, migratetype);
......
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