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Subject[PATCH 08/15] mm: mmzone: MIGRATE_CMA migration type added
From: Michal Nazarewicz <mina86@mina86.com>

The MIGRATE_CMA migration type has two main characteristics:
(i) only movable pages can be allocated from MIGRATE_CMA
pageblocks and (ii) page allocator will never change migration
type of MIGRATE_CMA pageblocks.

This guarantees (to some degree) that page in a MIGRATE_CMA page
block can always be migrated somewhere else (unless there's no
memory left in the system).

It is designed to be used for allocating big chunks (eg. 10MiB)
of physically contiguous memory. Once driver requests
contiguous memory, pages from MIGRATE_CMA pageblocks may be
migrated away to create a contiguous block.

To minimise number of migrations, MIGRATE_CMA migration type
is the last type tried when page allocator falls back to other
migration types then requested.

Signed-off-by: Michal Nazarewicz <mina86@mina86.com>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
---
include/linux/mmzone.h | 43 +++++++++++++++++++++----
include/linux/page-isolation.h | 3 ++
mm/Kconfig | 2 +-
mm/compaction.c | 11 +++++--
mm/page_alloc.c | 68 +++++++++++++++++++++++++++++++++-------
mm/vmstat.c | 3 ++
6 files changed, 107 insertions(+), 23 deletions(-)
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 650ba2f..fcd4a14 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -35,13 +35,37 @@
*/
#define PAGE_ALLOC_COSTLY_ORDER 3

-#define MIGRATE_UNMOVABLE 0
-#define MIGRATE_RECLAIMABLE 1
-#define MIGRATE_MOVABLE 2
-#define MIGRATE_PCPTYPES 3 /* the number of types on the pcp lists */
-#define MIGRATE_RESERVE 3
-#define MIGRATE_ISOLATE 4 /* can't allocate from here */
-#define MIGRATE_TYPES 5
+enum {
+ MIGRATE_UNMOVABLE,
+ MIGRATE_RECLAIMABLE,
+ MIGRATE_MOVABLE,
+ MIGRATE_PCPTYPES, /* the number of types on the pcp lists */
+ MIGRATE_RESERVE = MIGRATE_PCPTYPES,
+#ifdef CONFIG_CMA
+ /*
+ * MIGRATE_CMA migration type is designed to mimic the way
+ * ZONE_MOVABLE works. Only movable pages can be allocated
+ * from MIGRATE_CMA pageblocks and page allocator never
+ * implicitly change migration type of MIGRATE_CMA pageblock.
+ *
+ * The way to use it is to change migratetype of a range of
+ * pageblocks to MIGRATE_CMA which can be done by
+ * __free_pageblock_cma() function. What is important though
+ * is that a range of pageblocks must be aligned to
+ * MAX_ORDER_NR_PAGES should biggest page be bigger then
+ * a single pageblock.
+ */
+ MIGRATE_CMA,
+#endif
+ MIGRATE_ISOLATE, /* can't allocate from here */
+ MIGRATE_TYPES
+};
+
+#ifdef CONFIG_CMA
+# define is_migrate_cma(migratetype) unlikely((migratetype) == MIGRATE_CMA)
+#else
+# define is_migrate_cma(migratetype) false
+#endif

#define for_each_migratetype_order(order, type) \
for (order = 0; order < MAX_ORDER; order++) \
@@ -54,6 +78,11 @@ static inline int get_pageblock_migratetype(struct page *page)
return get_pageblock_flags_group(page, PB_migrate, PB_migrate_end);
}

+static inline bool is_pageblock_cma(struct page *page)
+{
+ return is_migrate_cma(get_pageblock_migratetype(page));
+}
+
struct free_area {
struct list_head free_list[MIGRATE_TYPES];
unsigned long nr_free;
diff --git a/include/linux/page-isolation.h b/include/linux/page-isolation.h
index 430cf61..454dd29 100644
--- a/include/linux/page-isolation.h
+++ b/include/linux/page-isolation.h
@@ -45,6 +45,9 @@ extern void unset_migratetype_isolate(struct page *page);
extern int alloc_contig_range(unsigned long start, unsigned long end);
extern void free_contig_range(unsigned long pfn, unsigned nr_pages);

+/* CMA stuff */
+extern void init_cma_reserved_pageblock(struct page *page);
+
#endif

#endif
diff --git a/mm/Kconfig b/mm/Kconfig
index e338407..3922002 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -198,7 +198,7 @@ config COMPACTION
config MIGRATION
bool "Page migration"
def_bool y
- depends on NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION
+ depends on NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA
help
Allows the migration of the physical location of pages of processes
while the virtual addresses are not changed. This is useful in
diff --git a/mm/compaction.c b/mm/compaction.c
index 3e21d28..a075b43 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -35,6 +35,11 @@ static unsigned long release_freepages(struct list_head *freelist)
return count;
}

+static inline bool migrate_async_suitable(int migratetype)
+{
+ return is_migrate_cma(migratetype) || migratetype == MIGRATE_MOVABLE;
+}
+
/*
* Isolate free pages onto a private freelist. Caller must hold zone->lock.
* If @strict is true, will abort returning 0 on any invalid PFNs or non-free
@@ -274,7 +279,7 @@ isolate_migratepages_range(struct zone *zone, struct compact_control *cc,
*/
pageblock_nr = low_pfn >> pageblock_order;
if (!cc->sync && last_pageblock_nr != pageblock_nr &&
- get_pageblock_migratetype(page) != MIGRATE_MOVABLE) {
+ migrate_async_suitable(get_pageblock_migratetype(page))) {
low_pfn += pageblock_nr_pages;
low_pfn = ALIGN(low_pfn, pageblock_nr_pages) - 1;
last_pageblock_nr = pageblock_nr;
@@ -342,8 +347,8 @@ static bool suitable_migration_target(struct page *page)
if (PageBuddy(page) && page_order(page) >= pageblock_order)
return true;

- /* If the block is MIGRATE_MOVABLE, allow migration */
- if (migratetype == MIGRATE_MOVABLE)
+ /* If the block is MIGRATE_MOVABLE or MIGRATE_CMA, allow migration */
+ if (migrate_async_suitable(migratetype))
return true;

/* Otherwise skip the block */
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 0a9cc8e..0fcde78 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -750,6 +750,26 @@ void __meminit __free_pages_bootmem(struct page *page, unsigned int order)
__free_pages(page, order);
}

+#ifdef CONFIG_CMA
+/*
+ * Free whole pageblock and set it's migration type to MIGRATE_CMA.
+ */
+void __init init_cma_reserved_pageblock(struct page *page)
+{
+ unsigned i = pageblock_nr_pages;
+ struct page *p = page;
+
+ do {
+ __ClearPageReserved(p);
+ set_page_count(p, 0);
+ } while (++p, --i);
+
+ set_page_refcounted(page);
+ set_pageblock_migratetype(page, MIGRATE_CMA);
+ __free_pages(page, pageblock_order);
+ totalram_pages += pageblock_nr_pages;
+}
+#endif

/*
* The order of subdivision here is critical for the IO subsystem.
@@ -875,10 +895,15 @@ struct page *__rmqueue_smallest(struct zone *zone, unsigned int order,
* This array describes the order lists are fallen back to when
* the free lists for the desirable migrate type are depleted
*/
-static int fallbacks[MIGRATE_TYPES][3] = {
+static int fallbacks[MIGRATE_TYPES][4] = {
[MIGRATE_UNMOVABLE] = { MIGRATE_RECLAIMABLE, MIGRATE_MOVABLE, MIGRATE_RESERVE },
[MIGRATE_RECLAIMABLE] = { MIGRATE_UNMOVABLE, MIGRATE_MOVABLE, MIGRATE_RESERVE },
+#ifdef CONFIG_CMA
+ [MIGRATE_MOVABLE] = { MIGRATE_RECLAIMABLE, MIGRATE_UNMOVABLE, MIGRATE_CMA , MIGRATE_RESERVE },
+ [MIGRATE_CMA] = { MIGRATE_RESERVE }, /* Never used */
+#else
[MIGRATE_MOVABLE] = { MIGRATE_RECLAIMABLE, MIGRATE_UNMOVABLE, MIGRATE_RESERVE },
+#endif
[MIGRATE_RESERVE] = { MIGRATE_RESERVE }, /* Never used */
[MIGRATE_ISOLATE] = { MIGRATE_RESERVE }, /* Never used */
};
@@ -995,11 +1020,18 @@ __rmqueue_fallback(struct zone *zone, int order, int start_migratetype)
* pages to the preferred allocation list. If falling
* back for a reclaimable kernel allocation, be more
* aggressive about taking ownership of free pages
+ *
+ * On the other hand, never change migration
+ * type of MIGRATE_CMA pageblocks nor move CMA
+ * pages on different free lists. We don't
+ * want unmovable pages to be allocated from
+ * MIGRATE_CMA areas.
*/
- if (unlikely(current_order >= (pageblock_order >> 1)) ||
- start_migratetype == MIGRATE_RECLAIMABLE ||
- page_group_by_mobility_disabled) {
- unsigned long pages;
+ if (!is_pageblock_cma(page) &&
+ (unlikely(current_order >= pageblock_order / 2) ||
+ start_migratetype == MIGRATE_RECLAIMABLE ||
+ page_group_by_mobility_disabled)) {
+ int pages;
pages = move_freepages_block(zone, page,
start_migratetype);

@@ -1017,11 +1049,14 @@ __rmqueue_fallback(struct zone *zone, int order, int start_migratetype)
rmv_page_order(page);

/* Take ownership for orders >= pageblock_order */
- if (current_order >= pageblock_order)
+ if (current_order >= pageblock_order &&
+ !is_pageblock_cma(page))
change_pageblock_range(page, current_order,
start_migratetype);

- expand(zone, page, order, current_order, area, migratetype);
+ expand(zone, page, order, current_order, area,
+ is_migrate_cma(start_migratetype)
+ ? start_migratetype : migratetype);

trace_mm_page_alloc_extfrag(page, order, current_order,
start_migratetype, migratetype);
@@ -1093,7 +1128,12 @@ static int rmqueue_bulk(struct zone *zone, unsigned int order,
list_add(&page->lru, list);
else
list_add_tail(&page->lru, list);
- set_page_private(page, migratetype);
+#ifdef CONFIG_CMA
+ if (is_pageblock_cma(page))
+ set_page_private(page, MIGRATE_CMA);
+ else
+#endif
+ set_page_private(page, migratetype);
list = &page->lru;
}
__mod_zone_page_state(zone, NR_FREE_PAGES, -(i << order));
@@ -1337,8 +1377,12 @@ int split_free_page(struct page *page)

if (order >= pageblock_order - 1) {
struct page *endpage = page + (1 << order) - 1;
- for (; page < endpage; page += pageblock_nr_pages)
- set_pageblock_migratetype(page, MIGRATE_MOVABLE);
+ for (; page < endpage; page += pageblock_nr_pages) {
+ int mt = get_pageblock_migratetype(page);
+ if (mt != MIGRATE_ISOLATE && !is_migrate_cma(mt))
+ set_pageblock_migratetype(page,
+ MIGRATE_MOVABLE);
+ }
}

return 1 << order;
@@ -5375,8 +5419,8 @@ __count_immobile_pages(struct zone *zone, struct page *page, int count)
*/
if (zone_idx(zone) == ZONE_MOVABLE)
return true;
-
- if (get_pageblock_migratetype(page) == MIGRATE_MOVABLE)
+ if (get_pageblock_migratetype(page) == MIGRATE_MOVABLE ||
+ is_pageblock_cma(page))
return true;

pfn = page_to_pfn(page);
diff --git a/mm/vmstat.c b/mm/vmstat.c
index f600557..ace5383 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -613,6 +613,9 @@ static char * const migratetype_names[MIGRATE_TYPES] = {
"Reclaimable",
"Movable",
"Reserve",
+#ifdef CONFIG_CMA
+ "CMA",
+#endif
"Isolate",
};

--
1.7.1.569.g6f426


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